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链路分析

2020-12-21T01:19:31Z

WildBoar：

本词条由Ryan初步翻译，已由WildBoar审校

In [[network theory]], '''link analysis''' is a [[data-analysis]] technique used to evaluate relationships (connections) between nodes. Relationships may be identified among various types of nodes (objects), including [[organization]]s, [[people]] and [[Financial transaction|transactions]]. Link analysis has been used for investigation of criminal activity ([[fraud detection]], [[counterterrorism]], and [[Intelligence (information gathering)|intelligence]]), [[Computer security|computer security analysis]], [[search engine optimization]], [[market research]], [[medical research]], and art.

In network theory, link analysis is a data-analysis technique used to evaluate relationships (connections) between nodes. Relationships may be identified among various types of nodes (objects), including organizations, people and transactions. Link analysis has been used for investigation of criminal activity (fraud detection, counterterrorism, and intelligence), computer security analysis, search engine optimization, market research, medical research, and art.

在''' 网络理论 Network Theory'''中，''' 链路分析 Link Analysis'''是一种用于评估节点之间关系（连接）的''' 数据分析 Data Analysis'''技术。该技术可以鉴别各种类型节点（对象）之间的关系，包括组织、人和金融交易。链路分析已被应用于诸多领域，如打击犯罪活动(如欺诈侦查、反恐和情报)、计算机安全分析、搜索引擎优化、市场调查、医学研究和艺术。

==Knowledge discovery==

==知识发现==

[[Knowledge discovery]] is an [[Iteration|iterative]] and [[interactive]] process used to [[Identification (information)|identify]], analyze and visualize patterns in data.<ref>{{cite web|url=https://www.torproject.org/about/overview.html.en|title=Tor Project: Overview|first=The Tor Project|last=Inc.|publisher=}}</ref> Network analysis, link analysis and [[social network analysis]] are all methods of knowledge discovery, each a corresponding subset of the prior method. Most knowledge discovery methods follow these steps (at the highest level):<ref>Ahonen, H., [http://www.cs.helsinki.fi/u/hahonen/features.txt Features of Knowledge Discovery Systems].</ref>

Knowledge discovery is an iterative and interactive process used to identify, analyze and visualize patterns in data. Network analysis, link analysis and social network analysis are all methods of knowledge discovery, each a corresponding subset of the prior method. Most knowledge discovery methods follow these steps (at the highest level):

''' 知识发现 Knowledge Discovery'''，是指不断地识别、分析和可视化数据中的内在模式，这是一个持续迭代和交互的过程。<ref>{{cite web|url=https://www.torproject.org/about/overview.html.en|title=Tor Project: Overview|first=The Tor Project|last=Inc.|publisher=}}</ref>网络分析、链路分析和'''社会网络分析 Social Network Analysis'''都是知识发现的方法，它们都是属于''' 先验方法 Prior Method'''。大多数知识发现方法遵循以下几个步骤('''在最高级别''' at the highest level) :<ref>Ahonen, H., [http://www.cs.helsinki.fi/u/hahonen/features.txt Features of Knowledge Discovery Systems].</ref>
--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）遇到拿不准的专业名词翻译可从cnki翻译助手检索一下该名词，下为链接http://dict.cnki.net/dict_result.aspx 选取引用量较高的释义进行翻译譬如Knowledge Discovery 可以暂时定为知识发现后续专家审校进行反馈再核实其准不准确

# [[Data processing]]

Data processing

数据处理

# [[Data transformation|Transformation]]

Transformation

数据转换

# [[Data analysis|Analysis]]

Analysis

数据分析

# [[Data visualization|Visualization]]

Visualization

数据可视化

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）这里很棒补充出“数据”这个限定词

Data gathering and processing requires access to data and has several inherent issues, including [[information overload]] and data errors. Once data is collected, it will need to be transformed into a format that can be effectively used by both human and computer analyzers. Manual or computer-generated visualizations tools may be mapped from the data, including network charts. Several algorithms exist to help with analysis of data – [[Dijkstra's algorithm|Dijkstra’s algorithm]], [[breadth-first search]], and [[depth-first search]].

Data gathering and processing requires access to data and has several inherent issues, including information overload and data errors. Once data is collected, it will need to be transformed into a format that can be effectively used by both human and computer analyzers. Manual or computer-generated visualizations tools may be mapped from the data, including network charts. Several algorithms exist to help with analysis of data – Dijkstra’s algorithm, breadth-first search, and depth-first search.

数据的收集和处理需要访问数据，但此过程存在一些固有的问题，包括'''信息超载 Information Overload'''和数据错误等。在数据被收集后，它将转换成一种人和计算机分析程序都能有效使用的格式。之后基于数据，可使用计算机生成的或人工操作的可视化工具进行作图（如网络图）。目前有几种算法可以帮助人类进行数据分析-'''迪杰斯特算法 Dijkstra’s algorithm'''，'''广度优先搜索 Breadth-First Search'''和''' 深度优先搜索 Depth-First Search'''。

Link analysis focuses on analysis of relationships among nodes through [[Visualization (computer graphics)|visualization methods]] ([[network charts]], association matrix). Here is an example of the relationships that may be mapped for crime investigations:<ref name=Krebs>Krebs, V. E. 2001, [http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf Mapping networks of terrorist cells] {{webarchive|url=https://web.archive.org/web/20110720000539/http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf |date=2011-07-20 }}, Connections 24, 43–52.</ref>

Link analysis focuses on analysis of relationships among nodes through visualization methods (network charts, association matrix). Here is an example of the relationships that may be mapped for crime investigations:

链路分析主要通过可视化方法(网络图、关联矩阵)分析节点之间的关系。这里有一个基于犯罪侦查绘制网图的例子:<ref name=Krebs>Krebs, V. E. 2001, [http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf Mapping networks of terrorist cells] {{webarchive|url=https://web.archive.org/web/20110720000539/http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf |date=2011-07-20 }}, Connections 24, 43–52.</ref>

{| class="wikitable"

{| class="wikitable"

{ | class“ wikitable”

|-

|-

|-

! Relationship/Network !! Data Sources

! Relationship/Network !! Data Sources

!关系/网络 !! 数据来源

|-

|-

|-

| 1. Trust || Prior contacts in family, neighborhood, school, military, club or organization. Public and court records. Data may only be available in suspect's native country.

| 1. Trust || Prior contacts in family, neighborhood, school, military, club or organization. Public and court records. Data may only be available in suspect's native country.

| 1.信任 || 嫌疑人在家庭、社区、学校、军队、俱乐部或组织中已有的关系；公开信息及法庭纪录；只能在嫌疑人本国使用的数据。

|-

|-

|-

| 2. Task || Logs and records of phone calls, electronic mail, chat rooms, instant messages, Web site visits. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 2. Task || Logs and records of phone calls, electronic mail, chat rooms, instant messages, Web site visits. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 2.任务 || 电话、电子邮件、聊天室、即时消息、网站访问的日志和记录；出入境纪录；人工智能: 会议和出席公共活动的观察报告。

|-

|-

|-

| 3. Money & Resources || Bank account and money transfer records. Pattern and location of credit card use. Prior court records. Human intelligence: observation of visits to alternate banking resources such as [[Hawala]].

| 3. Money & Resources || Bank account and money transfer records. Pattern and location of credit card use. Prior court records. Human intelligence: observation of visits to alternate banking resources such as Hawala.

| 3.资金和资源 || 银行账户和汇款记录；信用卡使用地点及使用习惯；以前的法庭记录。人工智能: 访问其他银行资源（如 Hawala）的观察报告。

|-

|-

|-

| 4. Strategy & Goals || Web sites. Videos and encrypted disks delivered by courier. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 4. Strategy & Goals || Web sites. Videos and encrypted disks delivered by courier. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 4.策略与目标 || 网站；由快递公司递送的视频和加密光盘；出入境纪录；人工智能: 会议和出席公共活动的观察报告。

|}

|}

|}

--[[用户:Vicky|Vicky]]（[[用户讨论:Vicky|讨论]]）observation 翻译为观察报告是不是更好？

--[[用户:Vicky|Vicky]]（[[用户讨论:Vicky|讨论]]）hawala: 哈瓦拉是独立于传统银行金融渠道的非正统、非主流的汇款系统，所以可以译为其他银行资源

Link analysis is used for 3 primary purposes:<ref name="Link Analysis Workbench">[https://docs.google.com/viewer?a=v&q=cache:R4_7k-udkxMJ:www.fas.org/irp/eprint/law.pdf+%22link+analysis%22&hl=en&gl=uk&pid=bl&srcid=ADGEESjUVRJFP2O2eMGzSuW4WtGgujUHVeuUYDQ9wqOkJUeVMHOwpagPa65ypDM5Fgma2AlwDyFBblZwXNMoYDCHwCQuTQvK-HnmqbW-z5A-MOwMKLy8nk6_uHLa0CiUAql-kAilAYcd&sig=AHIEtbRgGVNE4PMZ0a2vipzlDTd6OLX4fA Link Analysis Workbench], Air Force Research Laboratory Information Directorate, Rome Research Site, Rome, New York, September 2004.</ref>

Link analysis is used for 3 primary purposes:

链路分析主要有3个作用:<ref name="Link Analysis Workbench">[https://docs.google.com/viewer?a=v&q=cache:R4_7k-udkxMJ:www.fas.org/irp/eprint/law.pdf+%22link+analysis%22&hl=en&gl=uk&pid=bl&srcid=ADGEESjUVRJFP2O2eMGzSuW4WtGgujUHVeuUYDQ9wqOkJUeVMHOwpagPa65ypDM5Fgma2AlwDyFBblZwXNMoYDCHwCQuTQvK-HnmqbW-z5A-MOwMKLy8nk6_uHLa0CiUAql-kAilAYcd&sig=AHIEtbRgGVNE4PMZ0a2vipzlDTd6OLX4fA Link Analysis Workbench], Air Force Research Laboratory Information Directorate, Rome Research Site, Rome, New York, September 2004.</ref>

# Find matches in data for known patterns of interest;

Find matches in data for known patterns of interest;

在数据中寻找已知兴趣模式的匹配;

# Find anomalies where known patterns are violated;

Find anomalies where known patterns are violated;

发现与已知模式不相符的异常数据;

# Discover new patterns of interest (social network analysis, [[data mining]]).

Discover new patterns of interest (social network analysis, data mining).

发现新的兴趣模式(社会网络分析、数据挖掘)。

==History==

==历史==

Klerks categorized link analysis tools into 3 generations.<ref>{{cite journal | last = Klerks | first = P. | year = 2001 | title = The network paradigm applied to criminal organizations: Theoretical nitpicking or a relevant doctrine for investigators? Recent developments in the Netherlands | citeseerx = 10.1.1.129.4720 | journal = Connections | volume = 24 | pages = 53–65 }}</ref> The first generation was introduced in 1975 as the Anacpapa Chart of Harper and Harris.<ref>Harper and Harris, The Analysis of Criminal Intelligence, Human Factors and Ergonomics Society Annual Meeting Proceedings, 19(2), 1975, pp. 232-238.</ref> This method requires that a domain expert review data files, identify associations by constructing an association matrix, create a link chart for visualization and finally analyze the network chart to identify patterns of interest. This method requires extensive domain knowledge and is extremely time-consuming when reviewing vast amounts of data.

[[File:Association Matrix.png|thumb|
图1：Association Matrix 关联矩阵]]
--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）点击编辑后会发现[[File: 开头关于图片的语法该图注需要进行翻译且遵循格式【图1：英文原文＋翻译内容】

Klerks categorized link analysis tools into 3 generations. The first generation was introduced in 1975 as the Anacpapa Chart of Harper and Harris. This method requires that a domain expert review data files, identify associations by constructing an association matrix, create a link chart for visualization and finally analyze the network chart to identify patterns of interest. This method requires extensive domain knowledge and is extremely time-consuming when reviewing vast amounts of data.

Klerks把链路分析工具分为三代。<ref>{{cite journal | last = Klerks | first = P. | year = 2001 | title = The network paradigm applied to criminal organizations: Theoretical nitpicking or a relevant doctrine for investigators? Recent developments in the Netherlands | citeseerx = 10.1.1.129.4720 | journal = Connections | volume = 24 | pages = 53–65 }}</ref>第一代是由哈珀 Harper和哈里斯 Harris在1975年引入的''' 阿纳卡帕图 Anacpapa Chart'''。<ref>Harper and Harris, The Analysis of Criminal Intelligence, Human Factors and Ergonomics Society Annual Meeting Proceedings, 19(2), 1975, pp. 232-238.</ref>这种方法需要一个领域专家来查看数据文件，通过构造一个关联矩阵来识别关联，然后创建一个用于可视化的链路图，最后通过分析网络图来识别兴趣模式。这种方法需要广泛的领域知识，且因要审查大量数据，所以非常耗时。

In addition to the association matrix, the activities matrix can be used to produce actionable information, which has practical value and use to law-enforcement. The activities matrix, as the term might imply, centers on the actions and activities of people with respect to locations. Whereas the association matrix focuses on the relationships between people, organizations, and/or properties. The distinction between these two types of matrices, while minor, is nonetheless significant in terms of the output of the analysis completed or rendered.<ref>{{cite web|url=http://www.globalsecurity.org/military/library/policy/army/fm/3-07-22/app-f.htm|title=FMI 3-07.22 Appendix F Intelligence Analysis Tools and Indicators|first=John|last=Pike|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm Social Network Analysis and Other Analytical Tools] {{webarchive|url=https://web.archive.org/web/20140308233614/https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm |date=2014-03-08 }}</ref><ref>{{cite web|url=http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/Aeronautics_Activity_Matrices.html|title=Aeronautics Educator Guide - Activity Matrices|first=Rebecca Whitaker|last=MSFC|date=10 July 2009|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm Personality/Activity Matrix] {{webarchive|url=https://web.archive.org/web/20140308234135/https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm |date=2014-03-08 }}</ref>

In addition to the association matrix, the activities matrix can be used to produce actionable information, which has practical value and use to law-enforcement. The activities matrix, as the term might imply, centers on the actions and activities of people with respect to locations. Whereas the association matrix focuses on the relationships between people, organizations, and/or properties. The distinction between these two types of matrices, while minor, is nonetheless significant in terms of the output of the analysis completed or rendered.

除了关联矩阵外，活动矩阵也可用于生成对执法具有实用和使用价值的可操作的信息。正如这个术语可能暗示的那样，活动矩阵关注的是人们基于地点的行动和活动。而关联矩阵关注的是人，组织和/或属性之间的关系。这两类矩阵之间的区别虽然很小，但就完成或提供的数据来看，这些区别还是很重要的。<ref>{{cite web|url=http://www.globalsecurity.org/military/library/policy/army/fm/3-07-22/app-f.htm|title=FMI 3-07.22 Appendix F Intelligence Analysis Tools and Indicators|first=John|last=Pike|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm Social Network Analysis and Other Analytical Tools] {{webarchive|url=https://web.archive.org/web/20140308233614/https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm |date=2014-03-08 }}</ref><ref>{{cite web|url=http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/Aeronautics_Activity_Matrices.html|title=Aeronautics Educator Guide - Activity Matrices|first=Rebecca Whitaker|last=MSFC|date=10 July 2009|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm Personality/Activity Matrix] {{webarchive|url=https://web.archive.org/web/20140308234135/https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm |date=2014-03-08 }}</ref>

Second generation tools consist of automatic graphics-based analysis tools such as IBM i2 Analyst’s Notebook, Netmap, [[ClueMaker]] and Watson. These tools offer the ability to automate the construction and updates of the link chart once an association matrix is manually created, however, analysis of the resulting charts and graphs still requires an expert with extensive domain knowledge.

Second generation tools consist of automatic graphics-based analysis tools such as IBM i2 Analyst’s Notebook, Netmap, ClueMaker and Watson. These tools offer the ability to automate the construction and updates of the link chart once an association matrix is manually created, however, analysis of the resulting charts and graphs still requires an expert with extensive domain knowledge.

第二代工具包括基于图形的自动分析工具，如 IBM i2 Analyst’s Notebook、Netmap、 ClueMaker和Watson。在手动创建关联矩阵的情况下，这些工具提供了自动构建和更新链路图表的能力。然而，对结果图表的分析仍然需要在该领域具有广泛知识的专家。

The third generation of link-analysis tools like DataWalk allow the automatic visualization of linkages between elements in a data set, that can then serve as the canvas for further exploration or manual updates.

The third generation of link-analysis tools like DataWalk allow the automatic visualization of linkages between elements in a data set, that can then serve as the canvas for further exploration or manual updates.

第三代链路分析工具（例如DataWalk）可以自动显示数据集中元素之间的链路，然后可以在此基础上进一步探索或手动更新、。

==Applications ==

==应用 ==

* [[ViCAP|FBI Violent Criminal Apprehension Program (ViCAP)]]
联邦调查局暴力刑事逮捕程序

* Iowa State Sex Crimes Analysis System
爱荷华州性犯罪分析系统

* Minnesota State Sex Crimes Analysis System (MIN/SCAP)
明尼苏达州性犯罪分析系统

* Washington State Homicide Investigation Tracking System (HITS)<ref>{{cite web|url=http://www.atg.wa.gov/HITS.aspx |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101021005202/http://atg.wa.gov/HITS.aspx |archivedate=2010-10-21 }}</ref>
华盛顿州凶杀案调查追踪系统<ref>{{cite web|url=http://www.atg.wa.gov/HITS.aspx |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101021005202/http://atg.wa.gov/HITS.aspx |archivedate=2010-10-21 }}</ref>

* New York State Homicide Investigation & Lead Tracking (HALT)
纽约州凶杀案调查和线索追踪系统

* New Jersey Homicide Evaluation & Assessment Tracking (HEAT)<ref>{{cite web|url=http://www.state.nj.us/njsp/divorg/invest/invest.html |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20090325004722/http://www.state.nj.us/njsp/divorg/invest/invest.html |archivedate=2009-03-25 }}</ref>
新泽西州凶杀案评估与测评跟踪系统<ref>{{cite web|url=http://www.state.nj.us/njsp/divorg/invest/invest.html |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20090325004722/http://www.state.nj.us/njsp/divorg/invest/invest.html |archivedate=2009-03-25 }}</ref>

* Pennsylvania State ATAC Program.
宾夕法尼亚州ATAC程序

* Violent Crime Linkage Analysis System (ViCLAS)<ref>{{cite web|url=http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101202144141/http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |archivedate=2010-12-02 }}</ref>
暴力犯罪联系分析系统<ref>{{cite web|url=http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101202144141/http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |archivedate=2010-12-02 }}</ref>

==Issues with link analysis==

==链路分析的问题==

===Information overload===

===信息过载===

With the vast amounts of data and information that are stored electronically, users are confronted with multiple unrelated sources of information available for analysis. Data analysis techniques are required to make effective and efficient use of the data. Palshikar classifies data analysis techniques into two categories – ([[Statistics|statistical]] [[Models of computation|models]], [[Time series analysis|time-series analysis]], [[Clustering coefficient|clustering]] and [[Statistical classification|classification]], matching algorithms to detect anomalies) and [[Artificial intelligence|artificial intelligence (AI)]] techniques (data mining, [[expert systems]], [[pattern recognition]], [[Machine learning|machine learning techniques]], [[neural network]]s).<ref>Palshikar, G. K., [http://www.intelligententerprise.com//020528/509feat3_1.jhtml The Hidden Truth], Intelligent Enterprise, May 2002.</ref>

With the vast amounts of data and information that are stored electronically, users are confronted with multiple unrelated sources of information available for analysis. Data analysis techniques are required to make effective and efficient use of the data. Palshikar classifies data analysis techniques into two categories – (statistical models, time-series analysis, clustering and classification, matching algorithms to detect anomalies) and artificial intelligence (AI) techniques (data mining, expert systems, pattern recognition, machine learning techniques, neural networks).

由于大量数据和信息以电子形式存储，用户可能会面临拥有多种不相关的信息来源却不知如何分析的难题。数据分析技术的使用可以帮助有效和高效地利用数据。帕尔希卡尔 Palshikar将数据分析技术分为两大类(统计模型、时间序列分析、聚类分类、异常检测匹配算法)和人工智能(AI)技术(数据挖掘、专家系统、模式识别、机器学习技术、神经网络)。<ref>Palshikar, G. K., [http://www.intelligententerprise.com//020528/509feat3_1.jhtml The Hidden Truth], Intelligent Enterprise, May 2002.</ref>

Bolton & Hand define statistical data analysis as either supervised or unsupervised methods.<ref>Bolton, R. J. & Hand, D. J., Statistical Fraud Detection: A Review, Statistical Science, 2002, 17(3), pp. 235-255.</ref> [[Supervised learning|Supervised learning methods]] require that rules are defined within the system to establish what is expected or unexpected behavior. [[Unsupervised learning|Unsupervised learning methods]] review data in comparison to the norm and detect statistical outliers. Supervised learning methods are limited in the scenarios that can be handled as this method requires that training rules are established based on previous patterns. Unsupervised learning methods can provide detection of broader issues, however, may result in a higher false-positive ratio if the behavioral norm is not well established or understood.

Bolton & Hand define statistical data analysis as either supervised or unsupervised methods. Supervised learning methods require that rules are defined within the system to establish what is expected or unexpected behavior. Unsupervised learning methods review data in comparison to the norm and detect statistical outliers. Supervised learning methods are limited in the scenarios that can be handled as this method requires that training rules are established based on previous patterns. Unsupervised learning methods can provide detection of broader issues, however, may result in a higher false-positive ratio if the behavioral norm is not well established or understood.

博尔顿 Bolton &汉德 Hand 将统计数据分析定义为有监督或无监督的方法。<ref>Bolton, R. J. & Hand, D. J., Statistical Fraud Detection: A Review, Statistical Science, 2002, 17(3), pp. 235-255.</ref>'''监督式学习方法 Supervised Learning Methods'''要求在系统中有明确的规则来指出什么是预期行为，什么是意外行为。'''非监督式学习方法 Unsupervised Learning Methods'''在审视数据时，通过将数据与正常值的比较，来发现统计异常值。监督式学习方法能处理的场景是有限的，因为这种方法需要基于以前的模式建立训练规则。非监督式学习方法可以检测更广泛的问题。但是，如果数据的行为规范没有很好的建立或被机器理解 --[[用户:Ryan|Ryan]]（[[用户讨论:Ryan|讨论]]）该句存疑，其结果可能会导致较高的假阳性率（本身不是正常值，但识别为正常值，说明算法预测了“正确”或“有”的判断，但却判断错误了）。
--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）可能会导致较高的误报率

Data itself has inherent issues including integrity (or lack of) and continuous changes. Data may contain “errors of omission and commission because of faulty collection or handling, and when entities are actively attempting to deceive and/or conceal their actions”.<ref name="Link Analysis Workbench"/> Sparrow<ref>Sparrow M.K. 1991. Network Vulnerabilities and Strategic Intelligence in Law Enforcement’, [[International Journal of Intelligence and Counterintelligence]] Vol. 5 #3.</ref> highlights incompleteness (inevitability of missing data or links), fuzzy boundaries (subjectivity in deciding what to include) and dynamic changes (recognition that data is ever-changing) as the three primary problems with data analysis.<ref name=Krebs/>

Data itself has inherent issues including integrity (or lack of) and continuous changes. Data may contain '''“errors of omission and commission because of faulty collection or handling, and when entities are actively attempting to deceive and/or conceal their actions”.''' Sparrow highlights incompleteness (inevitability of missing data or links), fuzzy boundaries (subjectivity in deciding what to include) and dynamic changes (recognition that data is ever-changing) as the three primary problems with data analysis.

数据本身存在固有的问题，包括完整性(或缺失性)和持续的改变。数据可能包含'''“由于收集或处理不当，以及当实体积极试图欺骗和/或隐瞒其行为，而造成的遗漏和委托错误”。''' <ref name="Link Analysis Workbench"/> Sparrow<ref>“Sparrow<ref>Sparrow M.K. 1991. Network Vulnerabilities and Strategic Intelligence in Law Enforcement’, [[International Journal of Intelligence and Counterintelligence]] Vol. 5 #3.</ref> 强调了数据分析中三个主要的问题，不完整性(数据或链路缺失的必然性)、模糊边界(边界确定的主观性)和动态变化(数据的持续变化性)。

--[[用户:Vicky|Vicky]]（[[用户讨论:Vicky|讨论]]）标绿这句翻译大体上没有问题，表达可以更简练一点，因收集或处理不当，以及试图欺骗或隐瞒其行为而造成的遗漏和委托错误。

Once data is transformed into a usable format, open texture and cross referencing issues may arise. [[Open texture]] was defined by [[Friedrich Waismann|Waismann]] as the unavoidable uncertainty in meaning when empirical terms are used in different contexts.<ref>Friedrich Waismann, Verifiability (1945), p.2.</ref> Uncertainty in meaning of terms presents problems when attempting to search and cross reference data from multiple sources.<ref>Lyons, D., [http://ssrn.com/abstract=212328 Open Texture and the Possibility of Legal Interpretation (2000)].</ref>

Once data is transformed into a usable format, open texture and cross referencing issues may arise. Open texture was defined by Waismann as the unavoidable uncertainty in meaning when empirical terms are used in different contexts. Uncertainty in meaning of terms presents problems when attempting to search and cross reference data from multiple sources.

一旦数据转换成可用的格式，就会出现开放结构和交叉引用问题。魏斯曼 Waismann将''' 开放结构 Open Texture'''定义为在不同语境中使用经验词汇时不可避免的语义不确定性。<ref>Friedrich Waismann, Verifiability (1945), p.2.</ref>当试图从多个数据源搜索和交叉引用数据时，术语含义的不确定性带来了问题。<ref>Lyons, D., [http://ssrn.com/abstract=212328 Open Texture and the Possibility of Legal Interpretation (2000)].</ref>

The primary method for resolving data analysis issues is reliance on [[domain knowledge]] from an expert. This is a very time-consuming and costly method of conducting link analysis and has inherent problems of its own. McGrath et al. conclude that the layout and presentation of a network diagram have a significant impact on the user’s “perceptions of the existence of groups in networks”.<ref>McGrath, C., Blythe, J., Krackhardt, D., [http://www.andrew.cmu.edu/user/cm3t/groups.html Seeing Groups in Graph Layouts].</ref> Even using domain experts may result in differing conclusions as analysis may be subjective.

The primary method for resolving data analysis issues is reliance on domain knowledge from an expert. This is a very time-consuming and costly method of conducting link analysis and has inherent problems of its own. McGrath et al. conclude that the layout and presentation of a network diagram have a significant impact on the user’s “perceptions of the existence of groups in networks”. Even using domain experts may result in differing conclusions as analysis may be subjective.

目前，解决数据分析中这些问题的主要方法是依赖专家的领域知识。如此进行链路分析是非常耗时和昂贵的，并且无法排除其自身固有的问题。麦格拉斯 McGrath 等人得出结论：网络图的分布和表示方式对用户的“对存在在网络中群体的感知”有重大影响。<ref>McGrath, C., Blythe, J., Krackhardt, D., [http://www.andrew.cmu.edu/user/cm3t/groups.html Seeing Groups in Graph Layouts].</ref> 即使是领域内的专家也可能得出不同的结论，因为他们的分析可能是很主观的。

===Prosecution vs. crime prevention===

Link analysis techniques have primarily been used for prosecution, as it is far easier to review historical data for patterns than it is to attempt to predict future actions.

Link analysis techniques have primarily been used for prosecution, as it is far easier to review historical data for patterns than it is to attempt to predict future actions.

目前，链路分析技术主要用于经营，因为回顾历史数据以期从中获得模式，要比预测未来的行动容易得多。

Krebs demonstrated the use of an association matrix and link chart of the terrorist network associated with the 19 hijackers responsible for the [[September 11 attacks|September 11th attacks]] by mapping publicly available details made available following the attacks.<ref name=Krebs/> Even with the advantages of hindsight and publicly available information on people, places and transactions, it is clear that there is missing data.

Krebs demonstrated the use of an association matrix and link chart of the terrorist network associated with the 19 hijackers responsible for the September 11th attacks by mapping publicly available details made available following the attacks. Even with the advantages of hindsight and publicly available information on people, places and transactions, it is clear that there is missing data.

克雷布斯 Krebs基于袭击后的详细公开资料进行绘图，展示了与9月11日袭击事件的19名劫机者有关的恐怖分子关系网的关联矩阵和链路图。<ref name=Krebs/>即使有事后诸葛亮的优势--[[用户:Ryan|Ryan]]（[[用户讨论:Ryan|讨论]]），以及关于人员、地点和交易的公开可用信息，做出的结果图很明显仍然缺少数据。

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）即使有事后诸葛亮的优势如果进行了意译应标注讨论出来
--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）或许可以翻译成后见之明？

Alternatively, Picarelli argued that use of link analysis techniques could have been used to identify and potentially prevent illicit activities within the [[Aum Shinrikyo]] network.<ref>Picarelli, J. T., [http://kdl.cs.umass.edu/events/aila1998/picarelli.ps Transnational Threat Indications and Warning: The Utility of Network Analysis, Military and Intelligence Analysis Group].</ref> “We must be careful of ‘guilt by association’. Being linked to a terrorist does not prove guilt – but it does invite investigation.”<ref name=Krebs/> Balancing the legal concepts of [[probable cause]], [[right to privacy]] and [[freedom of association]] become challenging when reviewing potentially sensitive data with the objective to prevent crime or illegal activity that has not yet occurred.

Alternatively, Picarelli argued that use of link analysis techniques could have been used to identify and potentially prevent illicit activities within the Aum Shinrikyo network. “We must be careful of ‘guilt by association’. Being linked to a terrorist does not prove guilt – but it does invite investigation.” Balancing the legal concepts of probable cause, right to privacy and freedom of association become challenging when reviewing potentially sensitive data with the objective to prevent crime or illegal activity that has not yet occurred.

另外，皮卡雷利 Picarelli认为，使用链路分析技术可以用来查明并有可能防止奥姆真理教的非法活动。<ref>Picarelli, J. T., [http://kdl.cs.umass.edu/events/aila1998/picarelli.ps Transnational Threat Indications and Warning: The Utility of Network Analysis, Military and Intelligence Analysis Group].</ref>“我们必须小心‘牵连犯罪’。与恐怖分子有联系并不能证明有罪——但确实应该进行调查。”<ref name=Krebs/>如何在审查潜在敏感数据以防止尚未发生的犯罪或非法活动时不违背合理依据、隐私权和结社自由等法律概念将会变得很困难。

==Proposed solutions==

There are four categories of proposed link analysis solutions:<ref>Schroeder et al., Automated Criminal Link Analysis Based on Domain Knowledge, Journal of the American Society for Information Science and Technology, 58:6 (842), 2007.</ref>

There are four categories of proposed link analysis solutions:

有四类拟议的链路分析解决方案:<ref>Schroeder et al., Automated Criminal Link Analysis Based on Domain Knowledge, Journal of the American Society for Information Science and Technology, 58:6 (842), 2007.</ref>

# [[Heuristic|Heuristic-based]]

Heuristic-based

基于启发式的

# Template-based

Template-based

基于模板的

# Similarity-based

Similarity-based

基于相似性的

# [[Statistical]]

Statistical

统计方法

Heuristic-based tools utilize decision rules that are distilled from expert knowledge using structured data. Template-based tools employ [[Natural language processing|Natural Language Processing (NLP)]] to extract details from [[unstructured data]] that are matched to pre-defined templates. Similarity-based approaches use weighted [[Score (statistics)|scoring]] to compare attributes and identify potential links. Statistical approaches identify potential links based on lexical statistics.

Heuristic-based tools utilize decision rules that are distilled from expert knowledge using structured data. Template-based tools employ Natural Language Processing (NLP) to extract details from unstructured data that are matched to pre-defined templates. Similarity-based approaches use weighted scoring to compare attributes and identify potential links. Statistical approaches identify potential links based on lexical statistics.

基于启发式的工具利用结构化数据从专家知识中提取决策规则。基于模板的工具使用'''自然语言处理 Natural Language Processing'''从非结构化数据中提取与预定义模板匹配的具体信息。基于相似度的方法使用加权评分来比较属性和识别潜在的链路。统计方法基于词汇统计识别潜在的链路。

===CrimeNet explorer===

J.J. Xu and H. Chen propose a framework for automated network analysis and visualization called CrimeNet Explorer.<ref name=Xu>Xu, J.J. & Chen, H., CrimeNet Explorer: A Framework for Criminal Network Knowledge Discovery, ACM Transactions on Information Systems, 23(2), April 2005, pp. 201-226.</ref> This framework includes the following elements:

J.J. Xu and H. Chen propose a framework for automated network analysis and visualization called CrimeNet Explorer. This framework includes the following elements:

J.J.Xu和H.Chen 提出了一个自动化网络分析和可视化的框架，叫做 CrimeNet Explorer。<ref name=Xu>Xu, J.J. & Chen, H., CrimeNet Explorer: A Framework for Criminal Network Knowledge Discovery, ACM Transactions on Information Systems, 23(2), April 2005, pp. 201-226.</ref> 这一框架包括以下内容:

* Network Creation through a concept space approach that uses “[[Co-occurrence networks|co-occurrence]] weight to measure the frequency with which two words or phrases appear in the same document. The more frequently two words or phrases appear together, the more likely it will be that they are related”.<ref name=Xu/>

通过概念空间方法创建网络，该方法使用“共现网络”来衡量两个单词或短语在同一文档中出现的频率。两个单词或短语在一起出现的频率越高，它们关联的可能性就越大。<ref name=Xu/>

* Network Partition using “hierarchical clustering to partition a network into subgroups based on relational strength”.<ref name=Xu/>

网络分区通过“根据关系强度的分层聚类，将网络划分为子组”而实现。<ref name=Xu/>

* Structural Analysis through “three centrality measures (degree, betweenness, and closeness) to identify central members in a given subgroup.<ref name=Xu/> CrimeNet Explorer employed [[Dijkstra's algorithm|Dijkstra’s shortest-path algorithm]] to calculate the betweenness and closeness from a single node to all other nodes in the subgroup.

通过“三种中心性度量（度中心性，中介中心性和接近中心性）来识别给定子集中的中心成员”进行结构分析。CrimeNet Explorer使用''' 迪杰斯特拉最短路径算法 Dijkstra’s shortest-path algorithm'''来计算从单个节点到子组中所有其他节点的中介数和紧密程度。

* Network Visualization using Torgerson’s metric [[Multidimensional scaling|multidimensional scaling (MDS)]] algorithm.
使用托格森的度量多维标度（MDS）算法进行网络可视化。

==References==

==参考==





!-参见 http: / / en.wikipedia. org / wiki / wikipedia: 如何使用标记创建引用的脚注，这些标记将自动出现在这里 --

{{reflist|colwidth=30em}}

==External links==

==外部链接==

* {{cite book | last1 = Bartolini | first1 = I | last2 = Ciaccia | first2 = P. | title = Imagination: Accurate Image Annotation Using Link-Analysis Techniques | citeseerx = 10.1.1.63.2453 }}

* [https://fightfinancialcrimes.com/2015/12/17/link-analysis-and-fraud/ Link Analysis and Crime - An Examination]

* [https://www.ncbi.nlm.nih.gov/pubmed/9039449 Elink Schuurman MW, Srisaenpang S, Pinitsoontorn S, Bijleveld I, Vaeteewoothacharn K, Methapat C., The rapid village survey in tuberculosis control, Tuber Lung Dis. 1996 Dec;77(6):549-54.]

* [https://www.cs.cmu.edu/~gunhee/publish/cvpr08_gunhee.pdf Gunhee, K., Faloutsos, C, Hebert, M, Unsupervised Modeling of Object Categories Using Link Analysis Techniques.]

* [https://web.archive.org/web/20110928070620/http://www.blythe.org/Intelligence/readme/72sum McGehee, R., Intelligence Report.]

* [https://web.archive.org/web/20061107040453/http://www.hsaj.org/pages/volume2/issue2/pdfs/2.2.8.pdf Ressler, S., Social Network Analysis as an Approach to Combat Terrorism: Past, Present and Future Research.]

* [http://www.rff.com/link_analysis.htm RFFlow, How to Draw a Link Analysis Diagram.]

* [http://www-03.ibm.com/software/products/en/analysts-notebook-premium IBM i2 Analyst's Notebook Premium]

* {{cite journal | last1 = Silberschatz | first1 = A. | title = What Makes Patterns Interesting in Knowledge Discovery Systems | journal = IEEE Transactions on Knowledge and Data Engineering | volume = 8 | issue = 6 | pages = 970–974 | citeseerx = 10.1.1.53.2780 | year = 1996 | doi = 10.1109/69.553165 }}

* [http://www.intelcenter.com/trlaf.html Terrorist & Rebel Link Analysis Feed (TR-LAF)]

* [http://kt.ijs.si/dunja/LinkKDD2006/ Workshop on Link Analysis: Dynamics and Static of Large Networks (LinkKDD2006) August 20, 2006]

* [http://www.cluemaker.com ClueMaker]

* [http://www.datawalk.com Data Walk]

[[Category:Network theory]]

Category:Network theory

范畴: 网络理论

<noinclude>

This page was moved from [[wikipedia:en:Link analysis]]. Its edit history can be viewed at [[链路分析/edithistory]]</noinclude>

[[Category:待整理页面]]

链路分析

2020-12-20T15:32:04Z

WildBoar：

本词条由Ryan初步翻译，已由WildBoar审校

In [[network theory]], '''link analysis''' is a [[data-analysis]] technique used to evaluate relationships (connections) between nodes. Relationships may be identified among various types of nodes (objects), including [[organization]]s, [[people]] and [[Financial transaction|transactions]]. Link analysis has been used for investigation of criminal activity ([[fraud detection]], [[counterterrorism]], and [[Intelligence (information gathering)|intelligence]]), [[Computer security|computer security analysis]], [[search engine optimization]], [[market research]], [[medical research]], and art.

In network theory, link analysis is a data-analysis technique used to evaluate relationships (connections) between nodes. Relationships may be identified among various types of nodes (objects), including organizations, people and transactions. Link analysis has been used for investigation of criminal activity (fraud detection, counterterrorism, and intelligence), computer security analysis, search engine optimization, market research, medical research, and art.

在''' 网络理论 Network Theory'''中，''' 链路分析 Link Analysis'''是一种用于评估节点之间关系（连接）的''' 数据分析 Data Analysis'''技术。该技术可以鉴别各种类型节点（对象）之间的关系，包括组织、人和金融交易。链路分析已被应用于诸多领域，如打击犯罪活动(如欺诈侦查、反恐和情报)、计算机安全分析、搜索引擎优化、市场调查、医学研究和艺术。

==Knowledge discovery==

==知识发现==

[[Knowledge discovery]] is an [[Iteration|iterative]] and [[interactive]] process used to [[Identification (information)|identify]], analyze and visualize patterns in data.<ref>{{cite web|url=https://www.torproject.org/about/overview.html.en|title=Tor Project: Overview|first=The Tor Project|last=Inc.|publisher=}}</ref> Network analysis, link analysis and [[social network analysis]] are all methods of knowledge discovery, each a corresponding subset of the prior method. Most knowledge discovery methods follow these steps (at the highest level):<ref>Ahonen, H., [http://www.cs.helsinki.fi/u/hahonen/features.txt Features of Knowledge Discovery Systems].</ref>

Knowledge discovery is an iterative and interactive process used to identify, analyze and visualize patterns in data. Network analysis, link analysis and social network analysis are all methods of knowledge discovery, each a corresponding subset of the prior method. Most knowledge discovery methods follow these steps (at the highest level):

''' 知识发现 Knowledge Discovery'''，是指不断地识别、分析和可视化数据中的内在模式，这是一个持续迭代和交互的过程。<ref>{{cite web|url=https://www.torproject.org/about/overview.html.en|title=Tor Project: Overview|first=The Tor Project|last=Inc.|publisher=}}</ref>网络分析、链路分析和'''社会网络分析 Social Network Analysis'''都是知识发现的方法，它们都是属于''' 先验方法 Prior Method'''。大多数知识发现方法遵循以下几个步骤('''在最高级别''' at the highest level) :<ref>Ahonen, H., [http://www.cs.helsinki.fi/u/hahonen/features.txt Features of Knowledge Discovery Systems].</ref>
--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）遇到拿不准的专业名词翻译可从cnki翻译助手检索一下该名词，下为链接http://dict.cnki.net/dict_result.aspx 选取引用量较高的释义进行翻译譬如Knowledge Discovery 可以暂时定为知识发现后续专家审校进行反馈再核实其准不准确

# [[Data processing]]

Data processing

数据处理

# [[Data transformation|Transformation]]

Transformation

数据转换

# [[Data analysis|Analysis]]

Analysis

数据分析

# [[Data visualization|Visualization]]

Visualization

数据可视化

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）这里很棒补充出“数据”这个限定词

Data gathering and processing requires access to data and has several inherent issues, including [[information overload]] and data errors. Once data is collected, it will need to be transformed into a format that can be effectively used by both human and computer analyzers. Manual or computer-generated visualizations tools may be mapped from the data, including network charts. Several algorithms exist to help with analysis of data – [[Dijkstra's algorithm|Dijkstra’s algorithm]], [[breadth-first search]], and [[depth-first search]].

Data gathering and processing requires access to data and has several inherent issues, including information overload and data errors. Once data is collected, it will need to be transformed into a format that can be effectively used by both human and computer analyzers. Manual or computer-generated visualizations tools may be mapped from the data, including network charts. Several algorithms exist to help with analysis of data – Dijkstra’s algorithm, breadth-first search, and depth-first search.

数据的收集和处理需要访问数据，但此过程存在一些固有的问题，包括'''信息超载 Information Overload'''和数据错误等。在数据被收集后，它将转换成一种人和计算机分析程序都能有效使用的格式。之后基于数据，可使用计算机生成的或人工操作的可视化工具进行作图（如网络图）。目前有几种算法可以帮助人类进行数据分析-'''迪杰斯特算法 Dijkstra’s algorithm'''，'''广度优先搜索 Breadth-First Search'''和''' 深度优先搜索 Depth-First Search'''。

Link analysis focuses on analysis of relationships among nodes through [[Visualization (computer graphics)|visualization methods]] ([[network charts]], association matrix). Here is an example of the relationships that may be mapped for crime investigations:<ref name=Krebs>Krebs, V. E. 2001, [http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf Mapping networks of terrorist cells] {{webarchive|url=https://web.archive.org/web/20110720000539/http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf |date=2011-07-20 }}, Connections 24, 43–52.</ref>

Link analysis focuses on analysis of relationships among nodes through visualization methods (network charts, association matrix). Here is an example of the relationships that may be mapped for crime investigations:

链路分析主要通过可视化方法(网络图、关联矩阵)分析节点之间的关系。这里有一个基于犯罪侦查绘制网图的例子:<ref name=Krebs>Krebs, V. E. 2001, [http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf Mapping networks of terrorist cells] {{webarchive|url=https://web.archive.org/web/20110720000539/http://vlado.fmf.uni-lj.si/pub/networks/doc/Seminar/Krebs.pdf |date=2011-07-20 }}, Connections 24, 43–52.</ref>

{| class="wikitable"

{| class="wikitable"

{ | class“ wikitable”

|-

|-

|-

! Relationship/Network !! Data Sources

! Relationship/Network !! Data Sources

!关系/网络 !! 数据来源

|-

|-

|-

| 1. Trust || Prior contacts in family, neighborhood, school, military, club or organization. Public and court records. Data may only be available in suspect's native country.

| 1. Trust || Prior contacts in family, neighborhood, school, military, club or organization. Public and court records. Data may only be available in suspect's native country.

| 1.信任 || 嫌疑人在家庭、社区、学校、军队、俱乐部或组织中已有的关系；公开信息及法庭纪录；只能在嫌疑人本国使用的数据。

|-

|-

|-

| 2. Task || Logs and records of phone calls, electronic mail, chat rooms, instant messages, Web site visits. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 2. Task || Logs and records of phone calls, electronic mail, chat rooms, instant messages, Web site visits. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 2.任务 || 电话、电子邮件、聊天室、即时消息、网站访问的日志和记录；出入境纪录；人工智能: 观察会议和出席公共活动。

|-

|-

|-

| 3. Money & Resources || Bank account and money transfer records. Pattern and location of credit card use. Prior court records. Human intelligence: observation of visits to alternate banking resources such as [[Hawala]].

| 3. Money & Resources || Bank account and money transfer records. Pattern and location of credit card use. Prior court records. Human intelligence: observation of visits to alternate banking resources such as Hawala.

| 3.资金和资源 || 银行账户和汇款记录；信用卡使用地点及使用习惯；以前的法庭记录。'''人工智能: 访问其他银行资源的观察，如 Hawala。'''Human intelligence: observation of visits to alternate banking resources such as Hawala.

|-

|-

|-

| 4. Strategy & Goals || Web sites. Videos and encrypted disks delivered by courier. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 4. Strategy & Goals || Web sites. Videos and encrypted disks delivered by courier. Travel records. Human intelligence: observation of meetings and attendance at common events.

| 4.策略与目标 || 网站；由快递公司递送的视频和加密光盘；出入境纪录；人工智能: 观察会议和出席公共活动。

|}

|}

|}

Link analysis is used for 3 primary purposes:<ref name="Link Analysis Workbench">[https://docs.google.com/viewer?a=v&q=cache:R4_7k-udkxMJ:www.fas.org/irp/eprint/law.pdf+%22link+analysis%22&hl=en&gl=uk&pid=bl&srcid=ADGEESjUVRJFP2O2eMGzSuW4WtGgujUHVeuUYDQ9wqOkJUeVMHOwpagPa65ypDM5Fgma2AlwDyFBblZwXNMoYDCHwCQuTQvK-HnmqbW-z5A-MOwMKLy8nk6_uHLa0CiUAql-kAilAYcd&sig=AHIEtbRgGVNE4PMZ0a2vipzlDTd6OLX4fA Link Analysis Workbench], Air Force Research Laboratory Information Directorate, Rome Research Site, Rome, New York, September 2004.</ref>

Link analysis is used for 3 primary purposes:

链路分析主要有3个作用:<ref name="Link Analysis Workbench">[https://docs.google.com/viewer?a=v&q=cache:R4_7k-udkxMJ:www.fas.org/irp/eprint/law.pdf+%22link+analysis%22&hl=en&gl=uk&pid=bl&srcid=ADGEESjUVRJFP2O2eMGzSuW4WtGgujUHVeuUYDQ9wqOkJUeVMHOwpagPa65ypDM5Fgma2AlwDyFBblZwXNMoYDCHwCQuTQvK-HnmqbW-z5A-MOwMKLy8nk6_uHLa0CiUAql-kAilAYcd&sig=AHIEtbRgGVNE4PMZ0a2vipzlDTd6OLX4fA Link Analysis Workbench], Air Force Research Laboratory Information Directorate, Rome Research Site, Rome, New York, September 2004.</ref>

# Find matches in data for known patterns of interest;

Find matches in data for known patterns of interest;

在数据中寻找已知兴趣模式的匹配;

# Find anomalies where known patterns are violated;

Find anomalies where known patterns are violated;

发现与已知模式不相符的异常数据;

# Discover new patterns of interest (social network analysis, [[data mining]]).

Discover new patterns of interest (social network analysis, data mining).

发现新的兴趣模式(社会网络分析、数据挖掘)。

==History==

==历史==

Klerks categorized link analysis tools into 3 generations.<ref>{{cite journal | last = Klerks | first = P. | year = 2001 | title = The network paradigm applied to criminal organizations: Theoretical nitpicking or a relevant doctrine for investigators? Recent developments in the Netherlands | citeseerx = 10.1.1.129.4720 | journal = Connections | volume = 24 | pages = 53–65 }}</ref> The first generation was introduced in 1975 as the Anacpapa Chart of Harper and Harris.<ref>Harper and Harris, The Analysis of Criminal Intelligence, Human Factors and Ergonomics Society Annual Meeting Proceedings, 19(2), 1975, pp. 232-238.</ref> This method requires that a domain expert review data files, identify associations by constructing an association matrix, create a link chart for visualization and finally analyze the network chart to identify patterns of interest. This method requires extensive domain knowledge and is extremely time-consuming when reviewing vast amounts of data.

[[File:Association Matrix.png|thumb|
图1：Association Matrix 关联矩阵]]
--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）点击编辑后会发现[[File: 开头关于图片的语法该图注需要进行翻译且遵循格式【图1：英文原文＋翻译内容】

Klerks categorized link analysis tools into 3 generations. The first generation was introduced in 1975 as the Anacpapa Chart of Harper and Harris. This method requires that a domain expert review data files, identify associations by constructing an association matrix, create a link chart for visualization and finally analyze the network chart to identify patterns of interest. This method requires extensive domain knowledge and is extremely time-consuming when reviewing vast amounts of data.

Klerks把链路分析工具分为三代。<ref>{{cite journal | last = Klerks | first = P. | year = 2001 | title = The network paradigm applied to criminal organizations: Theoretical nitpicking or a relevant doctrine for investigators? Recent developments in the Netherlands | citeseerx = 10.1.1.129.4720 | journal = Connections | volume = 24 | pages = 53–65 }}</ref>第一代是由哈珀 Harper和哈里斯 Harris在1975年引入的''' 阿纳卡帕图 Anacpapa Chart'''。<ref>Harper and Harris, The Analysis of Criminal Intelligence, Human Factors and Ergonomics Society Annual Meeting Proceedings, 19(2), 1975, pp. 232-238.</ref>这种方法需要一个领域专家来查看数据文件，通过构造一个关联矩阵来识别关联，然后创建一个用于可视化的链路图，最后通过分析网络图来识别兴趣模式。这种方法需要广泛的领域知识，且因要审查大量数据，所以非常耗时。

In addition to the association matrix, the activities matrix can be used to produce actionable information, which has practical value and use to law-enforcement. The activities matrix, as the term might imply, centers on the actions and activities of people with respect to locations. Whereas the association matrix focuses on the relationships between people, organizations, and/or properties. The distinction between these two types of matrices, while minor, is nonetheless significant in terms of the output of the analysis completed or rendered.<ref>{{cite web|url=http://www.globalsecurity.org/military/library/policy/army/fm/3-07-22/app-f.htm|title=FMI 3-07.22 Appendix F Intelligence Analysis Tools and Indicators|first=John|last=Pike|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm Social Network Analysis and Other Analytical Tools] {{webarchive|url=https://web.archive.org/web/20140308233614/https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm |date=2014-03-08 }}</ref><ref>{{cite web|url=http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/Aeronautics_Activity_Matrices.html|title=Aeronautics Educator Guide - Activity Matrices|first=Rebecca Whitaker|last=MSFC|date=10 July 2009|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm Personality/Activity Matrix] {{webarchive|url=https://web.archive.org/web/20140308234135/https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm |date=2014-03-08 }}</ref>

In addition to the association matrix, the activities matrix can be used to produce actionable information, which has practical value and use to law-enforcement. The activities matrix, as the term might imply, centers on the actions and activities of people with respect to locations. Whereas the association matrix focuses on the relationships between people, organizations, and/or properties. The distinction between these two types of matrices, while minor, is nonetheless significant in terms of the output of the analysis completed or rendered.

除了关联矩阵外，活动矩阵也可用于生成对执法具有实用和使用价值的可操作的信息。正如这个术语可能暗示的那样，活动矩阵关注的是人们基于地点的行动和活动。而关联矩阵关注的是人，组织和/或属性之间的关系。这两类矩阵之间的区别虽然很小，但就完成或提供的数据来看，这些区别还是很重要的。<ref>{{cite web|url=http://www.globalsecurity.org/military/library/policy/army/fm/3-07-22/app-f.htm|title=FMI 3-07.22 Appendix F Intelligence Analysis Tools and Indicators|first=John|last=Pike|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm Social Network Analysis and Other Analytical Tools] {{webarchive|url=https://web.archive.org/web/20140308233614/https://rdl.train.army.mil/catalog/view/100.ATSC/41449AB4-E8E0-46C4-8443-E4276B6F0481-1274576841878/3-24/appb.htm |date=2014-03-08 }}</ref><ref>{{cite web|url=http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/Aeronautics_Activity_Matrices.html|title=Aeronautics Educator Guide - Activity Matrices|first=Rebecca Whitaker|last=MSFC|date=10 July 2009|publisher=}}</ref><ref>[https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm Personality/Activity Matrix] {{webarchive|url=https://web.archive.org/web/20140308234135/https://rdl.train.army.mil/catalog/view/100.ATSC/0EF89CA1-2680-4782-B103-D2F5DC941188-1274309335668/7-98-1/chap2l6.htm |date=2014-03-08 }}</ref>

Second generation tools consist of automatic graphics-based analysis tools such as IBM i2 Analyst’s Notebook, Netmap, [[ClueMaker]] and Watson. These tools offer the ability to automate the construction and updates of the link chart once an association matrix is manually created, however, analysis of the resulting charts and graphs still requires an expert with extensive domain knowledge.

Second generation tools consist of automatic graphics-based analysis tools such as IBM i2 Analyst’s Notebook, Netmap, ClueMaker and Watson. These tools offer the ability to automate the construction and updates of the link chart once an association matrix is manually created, however, analysis of the resulting charts and graphs still requires an expert with extensive domain knowledge.

第二代工具包括基于图形的自动分析工具，如 IBM i2 Analyst’s Notebook、Netmap、 ClueMaker和Watson。在手动创建关联矩阵的情况下，这些工具提供了自动构建和更新链路图表的能力。然而，对结果图表的分析仍然需要在该领域具有广泛知识的专家。

The third generation of link-analysis tools like DataWalk allow the automatic visualization of linkages between elements in a data set, that can then serve as the canvas for further exploration or manual updates.

The third generation of link-analysis tools like DataWalk allow the automatic visualization of linkages between elements in a data set, that can then serve as the canvas for further exploration or manual updates.

第三代链路分析工具（例如DataWalk）可以自动显示数据集中元素之间的链路，然后可以在此基础上进一步探索或手动更新、。

==Applications ==

==应用 ==

* [[ViCAP|FBI Violent Criminal Apprehension Program (ViCAP)]]
联邦调查局暴力刑事逮捕程序

* Iowa State Sex Crimes Analysis System
爱荷华州性犯罪分析系统

* Minnesota State Sex Crimes Analysis System (MIN/SCAP)
明尼苏达州性犯罪分析系统

* Washington State Homicide Investigation Tracking System (HITS)<ref>{{cite web|url=http://www.atg.wa.gov/HITS.aspx |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101021005202/http://atg.wa.gov/HITS.aspx |archivedate=2010-10-21 }}</ref>
华盛顿州凶杀案调查追踪系统<ref>{{cite web|url=http://www.atg.wa.gov/HITS.aspx |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101021005202/http://atg.wa.gov/HITS.aspx |archivedate=2010-10-21 }}</ref>

* New York State Homicide Investigation & Lead Tracking (HALT)
纽约州凶杀案调查和线索追踪系统

* New Jersey Homicide Evaluation & Assessment Tracking (HEAT)<ref>{{cite web|url=http://www.state.nj.us/njsp/divorg/invest/invest.html |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20090325004722/http://www.state.nj.us/njsp/divorg/invest/invest.html |archivedate=2009-03-25 }}</ref>
新泽西州凶杀案评估与测评跟踪系统<ref>{{cite web|url=http://www.state.nj.us/njsp/divorg/invest/invest.html |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20090325004722/http://www.state.nj.us/njsp/divorg/invest/invest.html |archivedate=2009-03-25 }}</ref>

* Pennsylvania State ATAC Program.
宾夕法尼亚州ATAC程序

* Violent Crime Linkage Analysis System (ViCLAS)<ref>{{cite web|url=http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101202144141/http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |archivedate=2010-12-02 }}</ref>
暴力犯罪联系分析系统<ref>{{cite web|url=http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |title=Archived copy |accessdate=2010-10-31 |url-status=dead |archiveurl=https://web.archive.org/web/20101202144141/http://www.rcmp-grc.gc.ca/tops-opst/bs-sc/viclas-salvac-eng.htm |archivedate=2010-12-02 }}</ref>

==Issues with link analysis==

==链路分析的问题==

===Information overload===

===信息过载===

With the vast amounts of data and information that are stored electronically, users are confronted with multiple unrelated sources of information available for analysis. Data analysis techniques are required to make effective and efficient use of the data. Palshikar classifies data analysis techniques into two categories – ([[Statistics|statistical]] [[Models of computation|models]], [[Time series analysis|time-series analysis]], [[Clustering coefficient|clustering]] and [[Statistical classification|classification]], matching algorithms to detect anomalies) and [[Artificial intelligence|artificial intelligence (AI)]] techniques (data mining, [[expert systems]], [[pattern recognition]], [[Machine learning|machine learning techniques]], [[neural network]]s).<ref>Palshikar, G. K., [http://www.intelligententerprise.com//020528/509feat3_1.jhtml The Hidden Truth], Intelligent Enterprise, May 2002.</ref>

With the vast amounts of data and information that are stored electronically, users are confronted with multiple unrelated sources of information available for analysis. Data analysis techniques are required to make effective and efficient use of the data. Palshikar classifies data analysis techniques into two categories – (statistical models, time-series analysis, clustering and classification, matching algorithms to detect anomalies) and artificial intelligence (AI) techniques (data mining, expert systems, pattern recognition, machine learning techniques, neural networks).

由于大量数据和信息以电子形式存储，用户可能会面临拥有多种不相关的信息来源却不知如何分析的难题。数据分析技术的使用可以帮助有效和高效地利用数据。帕尔希卡尔 Palshikar将数据分析技术分为两大类(统计模型、时间序列分析、聚类分类、异常检测匹配算法)和人工智能(AI)技术(数据挖掘、专家系统、模式识别、机器学习技术、神经网络)。<ref>Palshikar, G. K., [http://www.intelligententerprise.com//020528/509feat3_1.jhtml The Hidden Truth], Intelligent Enterprise, May 2002.</ref>

Bolton & Hand define statistical data analysis as either supervised or unsupervised methods.<ref>Bolton, R. J. & Hand, D. J., Statistical Fraud Detection: A Review, Statistical Science, 2002, 17(3), pp. 235-255.</ref> [[Supervised learning|Supervised learning methods]] require that rules are defined within the system to establish what is expected or unexpected behavior. [[Unsupervised learning|Unsupervised learning methods]] review data in comparison to the norm and detect statistical outliers. Supervised learning methods are limited in the scenarios that can be handled as this method requires that training rules are established based on previous patterns. Unsupervised learning methods can provide detection of broader issues, however, may result in a higher false-positive ratio if the behavioral norm is not well established or understood.

Bolton & Hand define statistical data analysis as either supervised or unsupervised methods. Supervised learning methods require that rules are defined within the system to establish what is expected or unexpected behavior. Unsupervised learning methods review data in comparison to the norm and detect statistical outliers. Supervised learning methods are limited in the scenarios that can be handled as this method requires that training rules are established based on previous patterns. Unsupervised learning methods can provide detection of broader issues, however, may result in a higher false-positive ratio if the behavioral norm is not well established or understood.

博尔顿 Bolton &汉德 Hand 将统计数据分析定义为有监督或无监督的方法。<ref>Bolton, R. J. & Hand, D. J., Statistical Fraud Detection: A Review, Statistical Science, 2002, 17(3), pp. 235-255.</ref>'''监督式学习方法 Supervised Learning Methods'''要求在系统中有明确的规则来指出什么是预期行为，什么是意外行为。'''非监督式学习方法 Unsupervised Learning Methods'''在审视数据时，通过将数据与正常值的比较，来发现统计异常值。监督式学习方法能处理的场景是有限的，因为这种方法需要基于以前的模式建立训练规则。非监督式学习方法可以检测更广泛的问题。但是，如果数据的行为规范没有很好的建立或被机器理解 --[[用户:Ryan|Ryan]]（[[用户讨论:Ryan|讨论]]）该句存疑，其结果可能会导致较高的假阳性率（本身不是正常值，但识别为正常值，说明算法预测了“正确”或“有”的判断，但却判断错误了）。
--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）可能会导致较高的误报率

Data itself has inherent issues including integrity (or lack of) and continuous changes. Data may contain “errors of omission and commission because of faulty collection or handling, and when entities are actively attempting to deceive and/or conceal their actions”.<ref name="Link Analysis Workbench"/> Sparrow<ref>Sparrow M.K. 1991. Network Vulnerabilities and Strategic Intelligence in Law Enforcement’, [[International Journal of Intelligence and Counterintelligence]] Vol. 5 #3.</ref> highlights incompleteness (inevitability of missing data or links), fuzzy boundaries (subjectivity in deciding what to include) and dynamic changes (recognition that data is ever-changing) as the three primary problems with data analysis.<ref name=Krebs/>

Data itself has inherent issues including integrity (or lack of) and continuous changes. Data may contain '''“errors of omission and commission because of faulty collection or handling, and when entities are actively attempting to deceive and/or conceal their actions”.''' Sparrow highlights incompleteness (inevitability of missing data or links), fuzzy boundaries (subjectivity in deciding what to include) and dynamic changes (recognition that data is ever-changing) as the three primary problems with data analysis.

数据本身存在固有的问题，包括完整性(或缺失性)和持续的改变。数据可能包含'''“由于收集或处理不当，以及当实体积极试图欺骗和/或隐瞒其行为，而造成的遗漏和委托错误”。''' <ref name="Link Analysis Workbench"/> Sparrow<ref>“Sparrow<ref>Sparrow M.K. 1991. Network Vulnerabilities and Strategic Intelligence in Law Enforcement’, [[International Journal of Intelligence and Counterintelligence]] Vol. 5 #3.</ref> 强调了数据分析中三个主要的问题，不完整性(数据或链路缺失的必然性)、模糊边界(边界确定的主观性)和动态变化(数据的持续变化性)。

Once data is transformed into a usable format, open texture and cross referencing issues may arise. [[Open texture]] was defined by [[Friedrich Waismann|Waismann]] as the unavoidable uncertainty in meaning when empirical terms are used in different contexts.<ref>Friedrich Waismann, Verifiability (1945), p.2.</ref> Uncertainty in meaning of terms presents problems when attempting to search and cross reference data from multiple sources.<ref>Lyons, D., [http://ssrn.com/abstract=212328 Open Texture and the Possibility of Legal Interpretation (2000)].</ref>

Once data is transformed into a usable format, open texture and cross referencing issues may arise. Open texture was defined by Waismann as the unavoidable uncertainty in meaning when empirical terms are used in different contexts. Uncertainty in meaning of terms presents problems when attempting to search and cross reference data from multiple sources.

一旦数据转换成可用的格式，就会出现开放结构和交叉引用问题。魏斯曼 Waismann将''' 开放结构 Open Texture'''定义为在不同语境中使用经验词汇时不可避免的语义不确定性。<ref>Friedrich Waismann, Verifiability (1945), p.2.</ref>当试图从多个数据源搜索和交叉引用数据时，术语含义的不确定性带来了问题。<ref>Lyons, D., [http://ssrn.com/abstract=212328 Open Texture and the Possibility of Legal Interpretation (2000)].</ref>

The primary method for resolving data analysis issues is reliance on [[domain knowledge]] from an expert. This is a very time-consuming and costly method of conducting link analysis and has inherent problems of its own. McGrath et al. conclude that the layout and presentation of a network diagram have a significant impact on the user’s “perceptions of the existence of groups in networks”.<ref>McGrath, C., Blythe, J., Krackhardt, D., [http://www.andrew.cmu.edu/user/cm3t/groups.html Seeing Groups in Graph Layouts].</ref> Even using domain experts may result in differing conclusions as analysis may be subjective.

The primary method for resolving data analysis issues is reliance on domain knowledge from an expert. This is a very time-consuming and costly method of conducting link analysis and has inherent problems of its own. McGrath et al. conclude that the layout and presentation of a network diagram have a significant impact on the user’s “perceptions of the existence of groups in networks”. Even using domain experts may result in differing conclusions as analysis may be subjective.

目前，解决数据分析中这些问题的主要方法是依赖专家的领域知识。如此进行链路分析是非常耗时和昂贵的，并且无法排除其自身固有的问题。麦格拉斯 McGrath 等人得出结论：网络图的分布和表示方式对用户的“对存在在网络中群体的感知”有重大影响。<ref>McGrath, C., Blythe, J., Krackhardt, D., [http://www.andrew.cmu.edu/user/cm3t/groups.html Seeing Groups in Graph Layouts].</ref> 即使是领域内的专家也可能得出不同的结论，因为他们的分析可能是很主观的。

===Prosecution vs. crime prevention===

Link analysis techniques have primarily been used for prosecution, as it is far easier to review historical data for patterns than it is to attempt to predict future actions.

Link analysis techniques have primarily been used for prosecution, as it is far easier to review historical data for patterns than it is to attempt to predict future actions.

目前，链路分析技术主要用于经营，因为回顾历史数据以期从中获得模式，要比预测未来的行动容易得多。

Krebs demonstrated the use of an association matrix and link chart of the terrorist network associated with the 19 hijackers responsible for the [[September 11 attacks|September 11th attacks]] by mapping publicly available details made available following the attacks.<ref name=Krebs/> Even with the advantages of hindsight and publicly available information on people, places and transactions, it is clear that there is missing data.

Krebs demonstrated the use of an association matrix and link chart of the terrorist network associated with the 19 hijackers responsible for the September 11th attacks by mapping publicly available details made available following the attacks. Even with the advantages of hindsight and publicly available information on people, places and transactions, it is clear that there is missing data.

克雷布斯 Krebs基于袭击后的详细公开资料进行绘图，展示了与9月11日袭击事件的19名劫机者有关的恐怖分子关系网的关联矩阵和链路图。<ref name=Krebs/>即使有事后诸葛亮的优势--[[用户:Ryan|Ryan]]（[[用户讨论:Ryan|讨论]]），以及关于人员、地点和交易的公开可用信息，做出的结果图很明显仍然缺少数据。

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）即使有事后诸葛亮的优势如果进行了意译应标注讨论出来
--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）或许可以翻译成后见之明？

Alternatively, Picarelli argued that use of link analysis techniques could have been used to identify and potentially prevent illicit activities within the [[Aum Shinrikyo]] network.<ref>Picarelli, J. T., [http://kdl.cs.umass.edu/events/aila1998/picarelli.ps Transnational Threat Indications and Warning: The Utility of Network Analysis, Military and Intelligence Analysis Group].</ref> “We must be careful of ‘guilt by association’. Being linked to a terrorist does not prove guilt – but it does invite investigation.”<ref name=Krebs/> Balancing the legal concepts of [[probable cause]], [[right to privacy]] and [[freedom of association]] become challenging when reviewing potentially sensitive data with the objective to prevent crime or illegal activity that has not yet occurred.

Alternatively, Picarelli argued that use of link analysis techniques could have been used to identify and potentially prevent illicit activities within the Aum Shinrikyo network. “We must be careful of ‘guilt by association’. Being linked to a terrorist does not prove guilt – but it does invite investigation.” Balancing the legal concepts of probable cause, right to privacy and freedom of association become challenging when reviewing potentially sensitive data with the objective to prevent crime or illegal activity that has not yet occurred.

另外，皮卡雷利 Picarelli认为，使用链路分析技术可以用来查明并有可能防止奥姆真理教的非法活动。<ref>Picarelli, J. T., [http://kdl.cs.umass.edu/events/aila1998/picarelli.ps Transnational Threat Indications and Warning: The Utility of Network Analysis, Military and Intelligence Analysis Group].</ref>“我们必须小心‘牵连犯罪’。与恐怖分子有联系并不能证明有罪——但确实应该进行调查。”<ref name=Krebs/>如何在审查潜在敏感数据以防止尚未发生的犯罪或非法活动时不违背合理依据、隐私权和结社自由等法律概念将会变得很困难。

==Proposed solutions==

There are four categories of proposed link analysis solutions:<ref>Schroeder et al., Automated Criminal Link Analysis Based on Domain Knowledge, Journal of the American Society for Information Science and Technology, 58:6 (842), 2007.</ref>

There are four categories of proposed link analysis solutions:

有四类拟议的链路分析解决方案:<ref>Schroeder et al., Automated Criminal Link Analysis Based on Domain Knowledge, Journal of the American Society for Information Science and Technology, 58:6 (842), 2007.</ref>

# [[Heuristic|Heuristic-based]]

Heuristic-based

基于启发式的

# Template-based

Template-based

基于模板的

# Similarity-based

Similarity-based

基于相似性的

# [[Statistical]]

Statistical

统计方法

Heuristic-based tools utilize decision rules that are distilled from expert knowledge using structured data. Template-based tools employ [[Natural language processing|Natural Language Processing (NLP)]] to extract details from [[unstructured data]] that are matched to pre-defined templates. Similarity-based approaches use weighted [[Score (statistics)|scoring]] to compare attributes and identify potential links. Statistical approaches identify potential links based on lexical statistics.

Heuristic-based tools utilize decision rules that are distilled from expert knowledge using structured data. Template-based tools employ Natural Language Processing (NLP) to extract details from unstructured data that are matched to pre-defined templates. Similarity-based approaches use weighted scoring to compare attributes and identify potential links. Statistical approaches identify potential links based on lexical statistics.

基于启发式的工具利用结构化数据从专家知识中提取决策规则。基于模板的工具使用'''自然语言处理 Natural Language Processing'''从非结构化数据中提取与预定义模板匹配的具体信息。基于相似度的方法使用加权评分来比较属性和识别潜在的链路。统计方法基于词汇统计识别潜在的链路。

===CrimeNet explorer===

J.J. Xu and H. Chen propose a framework for automated network analysis and visualization called CrimeNet Explorer.<ref name=Xu>Xu, J.J. & Chen, H., CrimeNet Explorer: A Framework for Criminal Network Knowledge Discovery, ACM Transactions on Information Systems, 23(2), April 2005, pp. 201-226.</ref> This framework includes the following elements:

J.J. Xu and H. Chen propose a framework for automated network analysis and visualization called CrimeNet Explorer. This framework includes the following elements:

J.J.Xu和H.Chen 提出了一个自动化网络分析和可视化的框架，叫做 CrimeNet Explorer。<ref name=Xu>Xu, J.J. & Chen, H., CrimeNet Explorer: A Framework for Criminal Network Knowledge Discovery, ACM Transactions on Information Systems, 23(2), April 2005, pp. 201-226.</ref> 这一框架包括以下内容:

* Network Creation through a concept space approach that uses “[[Co-occurrence networks|co-occurrence]] weight to measure the frequency with which two words or phrases appear in the same document. The more frequently two words or phrases appear together, the more likely it will be that they are related”.<ref name=Xu/>

通过概念空间方法创建网络，该方法使用“共现网络”来衡量两个单词或短语在同一文档中出现的频率。两个单词或短语在一起出现的频率越高，它们关联的可能性就越大。<ref name=Xu/>

* Network Partition using “hierarchical clustering to partition a network into subgroups based on relational strength”.<ref name=Xu/>

网络分区通过“根据关系强度的分层聚类，将网络划分为子组”而实现。<ref name=Xu/>

* Structural Analysis through “three centrality measures (degree, betweenness, and closeness) to identify central members in a given subgroup.<ref name=Xu/> CrimeNet Explorer employed [[Dijkstra's algorithm|Dijkstra’s shortest-path algorithm]] to calculate the betweenness and closeness from a single node to all other nodes in the subgroup.

通过“三种中心性度量（度中心性，中介中心性和接近中心性）来识别给定子集中的中心成员”进行结构分析。CrimeNet Explorer使用''' 迪杰斯特拉最短路径算法 Dijkstra’s shortest-path algorithm'''来计算从单个节点到子组中所有其他节点的中介数和紧密程度。

* Network Visualization using Torgerson’s metric [[Multidimensional scaling|multidimensional scaling (MDS)]] algorithm.
使用托格森的度量多维标度（MDS）算法进行网络可视化。

==References==

==参考==





!-参见 http: / / en.wikipedia. org / wiki / wikipedia: 如何使用标记创建引用的脚注，这些标记将自动出现在这里 --

{{reflist|colwidth=30em}}

==External links==

==外部链接==

* {{cite book | last1 = Bartolini | first1 = I | last2 = Ciaccia | first2 = P. | title = Imagination: Accurate Image Annotation Using Link-Analysis Techniques | citeseerx = 10.1.1.63.2453 }}

* [https://fightfinancialcrimes.com/2015/12/17/link-analysis-and-fraud/ Link Analysis and Crime - An Examination]

* [https://www.ncbi.nlm.nih.gov/pubmed/9039449 Elink Schuurman MW, Srisaenpang S, Pinitsoontorn S, Bijleveld I, Vaeteewoothacharn K, Methapat C., The rapid village survey in tuberculosis control, Tuber Lung Dis. 1996 Dec;77(6):549-54.]

* [https://www.cs.cmu.edu/~gunhee/publish/cvpr08_gunhee.pdf Gunhee, K., Faloutsos, C, Hebert, M, Unsupervised Modeling of Object Categories Using Link Analysis Techniques.]

* [https://web.archive.org/web/20110928070620/http://www.blythe.org/Intelligence/readme/72sum McGehee, R., Intelligence Report.]

* [https://web.archive.org/web/20061107040453/http://www.hsaj.org/pages/volume2/issue2/pdfs/2.2.8.pdf Ressler, S., Social Network Analysis as an Approach to Combat Terrorism: Past, Present and Future Research.]

* [http://www.rff.com/link_analysis.htm RFFlow, How to Draw a Link Analysis Diagram.]

* [http://www-03.ibm.com/software/products/en/analysts-notebook-premium IBM i2 Analyst's Notebook Premium]

* {{cite journal | last1 = Silberschatz | first1 = A. | title = What Makes Patterns Interesting in Knowledge Discovery Systems | journal = IEEE Transactions on Knowledge and Data Engineering | volume = 8 | issue = 6 | pages = 970–974 | citeseerx = 10.1.1.53.2780 | year = 1996 | doi = 10.1109/69.553165 }}

* [http://www.intelcenter.com/trlaf.html Terrorist & Rebel Link Analysis Feed (TR-LAF)]

* [http://kt.ijs.si/dunja/LinkKDD2006/ Workshop on Link Analysis: Dynamics and Static of Large Networks (LinkKDD2006) August 20, 2006]

* [http://www.cluemaker.com ClueMaker]

* [http://www.datawalk.com Data Walk]

[[Category:Network theory]]

Category:Network theory

范畴: 网络理论

<noinclude>

This page was moved from [[wikipedia:en:Link analysis]]. Its edit history can be viewed at [[链路分析/edithistory]]</noinclude>

[[Category:待整理页面]]

人群模拟

2020-12-15T01:45:00Z

WildBoar：

此词条暂由彩云小译翻译，未经人工整理和审校，带来阅读不便，请见谅。
已由WIldBoar审校
{{technical|date=October 2016}}

{{3D computer graphics}}

'''Crowd simulation''' is the process of simulating the movement (or '''{{vanchor|dynamics|CROWD_DYNAMICS}}''') of a large number of entities or characters.<ref>{{cite book |doi=10.1007/978-3-319-08234-9_69-1 |chapter=Crowd Simulation |title=Encyclopedia of Computer Graphics and Games |pages=1–8 |year=2016 |last1=Thalmann |first1=Daniel |isbn=978-3-319-08234-9 }}</ref> It is commonly used to create [[virtual scene]]s for visual media like films and [[video game]]s, and is also used in crisis training,<ref>http://cc.ist.psu.edu/BRIMS/archives/2007/papers/07-BRIMS-025.pdf Jérôme Comptdaer, Emmanuel Chiva, Stéphane Delorme, Henri Morlaye, Jérôme Volpoët, Multi-scale behavioral models for urban crisis training simulation.</ref> architecture and urban planning,<ref>{{cite journal |doi=10.1162/pres.16.3.318 |title=Design and Evaluation of a Real-World Virtual Environment for Architecture and Urban Planning |journal=Presence: Teleoperators and Virtual Environments |volume=16 |issue=3 |pages=318–32 |year=2007 |last1=Drettakis |first1=George |last2=Roussou |first2=Maria |last3=Reche |first3=Alex |last4=Tsingos |first4=Nicolas |url=https://hal.inria.fr/inria-00607261/file/DRRT07.pdf }}</ref> and evacuation simulation.<ref>{{cite journal |doi=10.1016/S0360-1323(98)00057-2 |title=A review of the methodologies used in the computer simulation of evacuation from the built environment |journal=Building and Environment |volume=34 |issue=6 |pages=741–9 |year=1999 |last1=Gwynne |first1=S. |last2=Galea |first2=E.R. |last3=Owen |first3=M. |last4=Lawrence |first4=P.J. |last5=Filippidis |first5=L. }}</ref>

Crowd simulation is the process of simulating the movement (or ) of a large number of entities or characters. It is commonly used to create virtual scenes for visual media like films and video games, and is also used in crisis training, architecture and urban planning, and evacuation simulation.

''' 人群模拟 Crowd simulation'''是对大量实体或人物的运动进行模拟的过程。<ref>{{cite book |doi=10.1007/978-3-319-08234-9_69-1 |chapter=Crowd Simulation |title=Encyclopedia of Computer Graphics and Games |pages=1–8 |year=2016 |last1=Thalmann |first1=Daniel |isbn=978-3-319-08234-9 }}</ref>它常用于电影和视频游戏等视觉媒体中创建虚拟场景，也用于危机培训、<ref>http://cc.ist.psu.edu/BRIMS/archives/2007/papers/07-BRIMS-025.pdf Jérôme Comptdaer, Emmanuel Chiva, Stéphane Delorme, Henri Morlaye, Jérôme Volpoët, Multi-scale behavioral models for urban crisis training simulation.</ref>建筑和城市规划<ref>{{cite journal |doi=10.1162/pres.16.3.318 |title=Design and Evaluation of a Real-World Virtual Environment for Architecture and Urban Planning |journal=Presence: Teleoperators and Virtual Environments |volume=16 |issue=3 |pages=318–32 |year=2007 |last1=Drettakis |first1=George |last2=Roussou |first2=Maria |last3=Reche |first3=Alex |last4=Tsingos |first4=Nicolas |url=https://hal.inria.fr/inria-00607261/file/DRRT07.pdf }}</ref> 以及''' 人群疏散模拟 Evacuation Simulations'''。<ref>{{cite journal |doi=10.1016/S0360-1323(98)00057-2 |title=A review of the methodologies used in the computer simulation of evacuation from the built environment |journal=Building and Environment |volume=34 |issue=6 |pages=741–9 |year=1999 |last1=Gwynne |first1=S. |last2=Galea |first2=E.R. |last3=Owen |first3=M. |last4=Lawrence |first4=P.J. |last5=Filippidis |first5=L. }}</ref>

Crowd simulation may focus on aspects that target different applications. For realistic and fast [[rendering (computer graphics)|rendering]] of a crowd for visual media or [[virtual cinematography]], reduction of the complexity of the [[3D scene]] and [[image-based rendering]] are used,<ref>{{cite journal |doi=10.1111/1467-8659.00633 |title=Visualizing Crowds in Real-Time |journal=Computer Graphics Forum |volume=21 |issue=4 |pages=753–65 |year=2002 |last1=Tecchia |first1=Franco |last2=Loscos |first2=Celine |last3=Chrysanthou |first3=Yiorgos }}</ref> while variations in appearance help present a realistic population.<ref name="Thalmann et al 2009">{{cite book |doi=10.1109/CW.2009.23 |chapter=Challenges in Crowd Simulation |title=2009 International Conference on CyberWorlds |pages=1–12 |year=2009 |last1=Thalmann |first1=Daniel |last2=Grillon |first2=Helena |last3=Maim |first3=Jonathan |last4=Yersin |first4=Barbara |isbn=978-1-4244-4864-7 |citeseerx=10.1.1.365.5045 }}</ref><ref name="Maim et al 2009">{{cite journal |doi=10.1109/MCG.2009.129 |pmid=24806782 |title=Unique Character Instances for Crowds |journal=IEEE Computer Graphics and Applications |volume=29 |issue=6 |pages=82–90 |year=2009 |last1=Maim |first1=J. |last2=Yersin |first2=B. |last3=Thalmann |first3=D. }}</ref>

Crowd simulation may focus on aspects that target different applications. For realistic and fast rendering of a crowd for visual media or virtual cinematography, reduction of the complexity of the 3D scene and image-based rendering are used, while variations in appearance help present a realistic population.

人群模拟专注的方面可以针对不同应用。为了对''' 视觉媒体 visual media'''或''' 虚拟摄影 virtual cinematography'''中的人群进行真实和快速渲染，可以减少 3D 场景的复杂性和基于图像的渲染，<ref>{{cite journal |doi=10.1111/1467-8659.00633 |title=Visualizing Crowds in Real-Time |journal=Computer Graphics Forum |volume=21 |issue=4 |pages=753–65 |year=2002 |last1=Tecchia |first1=Franco |last2=Loscos |first2=Celine |last3=Chrysanthou |first3=Yiorgos }}</ref> 而外观的变化有助于展现一个真实的人群。<ref name="Thalmann et al 2009">{{cite book |doi=10.1109/CW.2009.23 |chapter=Challenges in Crowd Simulation |title=2009 International Conference on CyberWorlds |pages=1–12 |year=2009 |last1=Thalmann |first1=Daniel |last2=Grillon |first2=Helena |last3=Maim |first3=Jonathan |last4=Yersin |first4=Barbara |isbn=978-1-4244-4864-7 |citeseerx=10.1.1.365.5045 }}</ref><ref name="Maim et al 2009">{{cite journal |doi=10.1109/MCG.2009.129 |pmid=24806782 |title=Unique Character Instances for Crowds |journal=IEEE Computer Graphics and Applications |volume=29 |issue=6 |pages=82–90 |year=2009 |last1=Maim |first1=J. |last2=Yersin |first2=B. |last3=Thalmann |first3=D. }}</ref>

In games and applications intended to replicate real-life [[human]] crowd movement, like in evacuation simulations, simulated agents may need to navigate towards a goal, avoid collisions, and exhibit other human-like behavior. Many crowd steering algorithms have been developed to lead simulated crowds to their goals realistically. Some more general systems are researched that can support different kinds of agents (like cars and pedestrians),<ref>{{cite journal |doi=10.1002/cav.1654 |title=Vehicle-pedestrian interaction for mixed traffic simulation |journal=Computer Animation and Virtual Worlds |volume=26 |issue=3–4 |pages=405–12 |year=2015 |last1=Chao |first1=Qianwen |last2=Deng |first2=Zhigang |last3=Jin |first3=Xiaogang }}</ref> different levels of abstraction(like individual and continuum),<ref>{{cite journal |doi=10.1145/2070781.2024169 |title=Interactive hybrid simulation of large-scale traffic |journal=ACM Transactions on Graphics |volume=30 |issue=6 |pages=1 |year=2011 |last1=Sewall |first1=Jason |last2=Wilkie |first2=David |last3=Lin |first3=Ming C. }}</ref> agents interacting with smart objects,<ref>{{cite book |doi=10.1007/978-3-7091-6375-7_6 |chapter=Modeling Objects for Interaction Tasks |title=Computer Animation and Simulation '98 |pages=73–86 |series=Eurographics |year=1999 |last1=Kallmann |first1=Marcelo |last2=Thalmann |first2=Daniel |isbn=978-3-211-83257-8 |citeseerx=10.1.1.550.2013 }}</ref> and more complex physical and social dynamics.<ref>http://dl.acm.org/citation.cfm?id=1272705 Pelechano, N. and Allbeck, J. M. and Badler, N. I. Controlling individual agents in high-density crowd simulation. In Proceedings of the 2007 ACM SIGGRAPH/Eurographics Symposium on Computer Animation. {{ISBN|978-1-59593-624-0}}</ref>

In games and applications intended to replicate real-life human crowd movement, like in evacuation simulations, simulated agents may need to navigate towards a goal, avoid collisions, and exhibit other human-like behavior. Many crowd steering algorithms have been developed to lead simulated crowds to their goals realistically. Some more general systems are researched that can support different kinds of agents (like cars and pedestrians), different levels of abstraction(like individual and continuum), agents interacting with smart objects, and more complex physical and social dynamics.

在模拟真实人群运动的游戏和应用程序，比如人群疏散模拟中，''' 模拟的主体 Simulated Agents'''可能需要到达某个目标，避免碰撞，并表现出其他类似人的行为。现在已经有很多种''' 人群引导算法 Crowd Steering Algorithms'''能实际地引导模拟人群到达他们的目标。一些更普通的系统被研发出来支持不同的主体类型(如汽车和行人)，<ref>{{cite journal |doi=10.1002/cav.1654 |title=Vehicle-pedestrian interaction for mixed traffic simulation |journal=Computer Animation and Virtual Worlds |volume=26 |issue=3–4 |pages=405–12 |year=2015 |last1=Chao |first1=Qianwen |last2=Deng |first2=Zhigang |last3=Jin |first3=Xiaogang }}</ref>不同的抽象层次(如个体和''' 连续体 Continuum''')，<ref>{{cite journal |doi=10.1145/2070781.2024169 |title=Interactive hybrid simulation of large-scale traffic |journal=ACM Transactions on Graphics |volume=30 |issue=6 |pages=1 |year=2011 |last1=Sewall |first1=Jason |last2=Wilkie |first2=David |last3=Lin |first3=Ming C. }}</ref>可以和智能对象交互的主体，<ref>{{cite book |doi=10.1007/978-3-7091-6375-7_6 |chapter=Modeling Objects for Interaction Tasks |title=Computer Animation and Simulation '98 |pages=73–86 |series=Eurographics |year=1999 |last1=Kallmann |first1=Marcelo |last2=Thalmann |first2=Daniel |isbn=978-3-211-83257-8 |citeseerx=10.1.1.550.2013 }}</ref>以及更复杂的物理和社会动态。<ref>http://dl.acm.org/citation.cfm?id=1272705 Pelechano, N. and Allbeck, J. M. and Badler, N. I. Controlling individual agents in high-density crowd simulation. In Proceedings of the 2007 ACM SIGGRAPH/Eurographics Symposium on Computer Animation. {{ISBN|978-1-59593-624-0}}</ref>

== History 历史==

There has always been a deep-seated interest in the understanding and gaining control of motional and behavior of crowds of people. Many major advancements have taken place since the beginnings of research within the realm of crowd simulation. Evidently many new findings are continually made and published following these which improve the scalability, flexibility, applicability, and realism of simulations:

There has always been a deep-seated interest in the understanding and gaining control of motional and behavior of crowds of people. Many major advancements have taken place since the beginnings of research within the realm of crowd simulation. Evidently many new findings are continually made and published following these which improve the scalability, flexibility, applicability, and realism of simulations:

理解和控制人群的运动和行为一直是人们的兴趣所在。人群模拟领域的研究开始以来，人们已经取得了许多重大进展。显然，许多新发现正不断地被提出、被发表。这些发现提高了仿真模拟的可扩展性、灵活性、适用性和真实性 :

In 1987, behavioral animation was introduced and developed by [[Craig Reynolds (computer graphics)|Craig Reynolds]].<ref>{{Cite book|last=Reynolds|first=Craig|year=1987|title=Flocks, herds, and schools: A distributed behavior model.|url=|journal=Proceedings of ACM SIGGRAPH 87|volume=July 1987|pages=25–34|doi=10.1145/37401.37406|citeseerx=10.1.1.103.7187|isbn=978-0897912273}}</ref> He had simulated flocks of birds alongside schools of fish for the purpose of studying group intuition and movement. All agents within these simulations were given direct access to the respective positions and velocities of their surrounding agents. The theorization and study set forth by Reynolds was improved and built upon in 1994 by [[Xiaoyuan Tu]], [[Demetri Terzopoulos]] and Radek Grzeszczuk.<ref>{{cite journal |doi=10.1162/artl.1994.1.4.327 |title=Artificial Fishes: Autonomous Locomotion, Perception, Behavior, and Learning in a Simulated Physical World |journal=Artificial Life |volume=1 |issue=4 |pages=327–51 |year=1994 |last1=Terzopoulos |first1=Demetri |last2=Tu |first2=Xiaoyuan |last3=Grzeszczuk |first3=Radek |citeseerx=10.1.1.33.8131 }}</ref> The realistic quality of simulation was engaged with as the individual agents were equipped with synthetic vision and a general view of the environment within which they resided, allowing for a perceptual awareness within their dynamic habitats.

In 1987, behavioral animation was introduced and developed by Craig Reynolds. He had simulated flocks of birds alongside schools of fish for the purpose of studying group intuition and movement. All agents within these simulations were given direct access to the respective positions and velocities of their surrounding agents. The theorization and study set forth by Reynolds was improved and built upon in 1994 by Xiaoyuan Tu, Demetri Terzopoulos and Radek Grzeszczuk. The realistic quality of simulation was engaged with as the individual agents were equipped with synthetic vision and a general view of the environment within which they resided, allowing for a perceptual awareness within their dynamic habitats.

1987年，克雷格·雷诺兹 Craig Reynolds引入并发展了''' 行为动画 behavioral animation'''。<ref>{{Cite book|last=Reynolds|first=Craig|year=1987|title=Flocks, herds, and schools: A distributed behavior model.|url=|journal=Proceedings of ACM SIGGRAPH 87|volume=July 1987|pages=25–34|doi=10.1145/37401.37406|citeseerx=10.1.1.103.7187|isbn=978-0897912273}}</ref>为了研究群体直觉和运动，他模拟了一群鸟和一群鱼。在这些模拟中的所有主体都可以直接访问它们周围各个主体的位置和速度。雷诺兹建立的理论和研究是在Xiaoyuan Tu、特佐普洛斯 Demetri Terzopoulos和格兹兹丘克 Radek Grzeszczuk1994年的研究之上改进和发展的。.<ref>{{cite journal |doi=10.1162/artl.1994.1.4.327 |title=Artificial Fishes: Autonomous Locomotion, Perception, Behavior, and Learning in a Simulated Physical World |journal=Artificial Life |volume=1 |issue=4 |pages=327–51 |year=1994 |last1=Terzopoulos |first1=Demetri |last2=Tu |first2=Xiaoyuan |last3=Grzeszczuk |first3=Radek |citeseerx=10.1.1.33.8131 }}</ref> 该模拟的真实性是有保证的，因为个体主体拥有合成视觉并对它们的居住环境有总体了解，从而可以对动态的栖息地有感性的认识。

--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） The realistic quality of simulation... 这一句话分成两句看，并且加入了一些个人理解，不知含义是否正确

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）这句不太通

--[[用户:Vicky|Vicky]]（[[用户讨论:Vicky|讨论]]） as后面引导了一个原因状语从句

Initial research in the field of crowd simulation began in 1997 with [[Daniel Thalmann]]'s supervision of Soraia Raupp Musse's PhD thesis. These two present a new model of crowd behavior in order to create a simulation of generic populations.<ref>{{Cite book|url=https://books.google.com/?id=3Adh_2ZNGLAC&pg=PR8&dq=history+of+crowd+simulation#v=onepage&q=history%20of%20crowd%20simulation&f=false|title=Crowd Simulation|last=Thalmann|first=Daniel|last2=Musse|first2=Soraia Raupp|date=2012-10-04|publisher=Springer Science & Business Media|isbn=978-1-4471-4449-6|language=en}}</ref> Here a relation is drawn between the autonomous behavior of the individual within the crowd and the emergent behavior originating from this.<ref>{{cite book |doi=10.1007/978-3-7091-6874-5_3 |chapter=A Model of Human Crowd Behavior : Group Inter-Relationship and Collision Detection Analysis |title=Computer Animation and Simulation '97 |pages=39–51 |series=Eurographics |year=1997 |last1=Musse |first1=S. R. |last2=Thalmann |first2=D. |isbn=978-3-211-83048-2 |citeseerx=10.1.1.14.7049 }}</ref>

Initial research in the field of crowd simulation began in 1997 with Daniel Thalmann's supervision of Soraia Raupp Musse's PhD thesis. These two present a new model of crowd behavior in order to create a simulation of generic populations. Here a relation is drawn between the autonomous behavior of the individual within the crowd and the emergent behavior originating from this.

最初的人群模拟领域研究始于1997年丹尼尔·塔尔曼 Daniel Thalmann指导苏拉娅·劳普·米塞尔 Soraia Raupp Musse的博士论文。他们两人提出了一个新的人群行为模型，以创建一个一般人群的仿真模拟。<ref>{{Cite book|url=https://books.google.com/?id=3Adh_2ZNGLAC&pg=PR8&dq=history+of+crowd+simulation#v=onepage&q=history%20of%20crowd%20simulation&f=false|title=Crowd Simulation|last=Thalmann|first=Daniel|last2=Musse|first2=Soraia Raupp|date=2012-10-04|publisher=Springer Science & Business Media|isbn=978-1-4471-4449-6|language=en}}</ref> 在这个模型中，他们给出了群体中个体的自主行为和由此产生的行为之间的一种关系。<ref>{{cite book |doi=10.1007/978-3-7091-6874-5_3 |chapter=A Model of Human Crowd Behavior : Group Inter-Relationship and Collision Detection Analysis |title=Computer Animation and Simulation '97 |pages=39–51 |series=Eurographics |year=1997 |last1=Musse |first1=S. R. |last2=Thalmann |first2=D. |isbn=978-3-211-83048-2 |citeseerx=10.1.1.14.7049 }}</ref>

In 1999, individualistic navigation began its course within the realm of crowd simulation via continued research of Craig Reynolds.<ref>{{Cite web|url=http://www.red3d.com/cwr/papers/1999/gdc99steer.html|title=Steering Behaviors For Autonomous Characters|website=www.red3d.com|access-date=2016-12-17}}</ref> Steering behaviors are proven to play a large role in the process of automating agents within a simulation. Reynolds states the processes of low-level locomotion to be dependent and reliant on mid-level steering behaviors and higher-level goal states and path finding strategies. Building off of the advanced work of Reynolds, Musse and Thalmann began to study the modeling of [[real-time simulation|real time simulation]]s of these crowds, and their applications to human behavior. The control of human crowds was designated as a hierarchical organization with levels of autonomy amongst agents. This marks the beginnings of modeling individual behavior in its most elementary form on humanoid agents.<ref>{{cite journal |doi=10.1109/2945.928167 |title=Hierarchical model for real time simulation of virtual human crowds |journal=IEEE Transactions on Visualization and Computer Graphics |volume=7 |issue=2 |pages=152–64 |year=2001 |last1=Musse |first1=S.R. |last2=Thalmann |first2=D. |url=http://infoscience.epfl.ch/record/98931 |type=Submitted manuscript }}</ref>

In 1999, individualistic navigation began its course within the realm of crowd simulation via continued research of Craig Reynolds. Steering behaviors are proven to play a large role in the process of automating agents within a simulation. Reynolds states the processes of low-level locomotion to be dependent and reliant on mid-level steering behaviors and higher-level goal states and path finding strategies. Building off of the advanced work of Reynolds, Musse and Thalmann began to study the modeling of real time simulations of these crowds, and their applications to human behavior. The control of human crowds was designated as a hierarchical organization with levels of autonomy amongst agents. This marks the beginnings of modeling individual behavior in its most elementary form on humanoid agents.

1999年，通过雷诺兹的持续研究，''' 个人主义导航 individualistic navigation'''开始了它在人群模拟领域的进程。<ref>{{Cite web|url=http://www.red3d.com/cwr/papers/1999/gdc99steer.html|title=Steering Behaviors For Autonomous Characters|website=www.red3d.com|access-date=2016-12-17}}</ref>仿真中，''' 指导行为Steering Behaviors'''在自动化主体过程中起着重要的作用。雷诺兹指出，低水平运动的过程依赖中等水平的指导行为和高水平的目标状态以及''' 路径寻找策略 Path Finding Strategies'''。在雷诺兹工作的基础之上，米塞尔和塔尔曼开始研究人群的实时模拟模型，以及它们在人类行为中的应用。对人群的控制被指定为一个具有不同主体自治水平的等级组织。这标志着在类人主体上以最基本的形式建立个体行为模型的开始。<ref>{{cite journal |doi=10.1109/2945.928167 |title=Hierarchical model for real time simulation of virtual human crowds |journal=IEEE Transactions on Visualization and Computer Graphics |volume=7 |issue=2 |pages=152–64 |year=2001 |last1=Musse |first1=S.R. |last2=Thalmann |first2=D. |url=http://infoscience.epfl.ch/record/98931 |type=Submitted manuscript }}</ref>

Coinciding with publications regarding human behavior models and simulations of group behaviors, Matt Anderson, Eric McDaniel, and Stephen Chenney's proposal of constraints on behavior<ref>{{Cite article|author1=Matt Anderson|author2=Eric McDaniel|author3=Stephen Chenney|title=Constrained animation of flocks|publisher=SCA '03 Proceedings of the 2003 ACM SIGGRAPH/Eurographics symposium on Computer animation |pages= 286–297|date=July 26–27, 2003 |ISBN=1-58113-659-5 }}</ref> gained popularity. The positioning of constraints on group animations was presented to be able to be done at any time within the simulation. This process of applying constraints to the behavioral model is undergone in a two-fold manner, by first determining the initial set of goal trajectories coinciding with the constraints, and then applying behavioral rules to these paths to select those which do not violate them.

Coinciding with publications regarding human behavior models and simulations of group behaviors, Matt Anderson, Eric McDaniel, and Stephen Chenney's proposal of constraints on behavior gained popularity. The positioning of constraints on group animations was presented to be able to be done at any time within the simulation. This process of applying constraints to the behavioral model is undergone in a two-fold manner, by first determining the initial set of goal trajectories coinciding with the constraints, and then applying behavioral rules to these paths to select those which do not violate them.

和人类行为模型和群体行为模拟的论文发表恰巧同一时期，马特•安德森 Matt Anderson、埃里克•麦克丹尼尔 Eric McDaniel和史蒂芬·切尼Stephen Chenney关于行为约束的研究计划<ref>{{Cite article|author1=Matt Anderson|author2=Eric McDaniel|author3=Stephen Chenney|title=Constrained animation of flocks|publisher=SCA '03 Proceedings of the 2003 ACM SIGGRAPH/Eurographics symposium on Computer animation |pages= 286–297|date=July 26–27, 2003 |ISBN=1-58113-659-5 }}</ref>大受欢迎。他们展示了对''' 群体动画 Group Animations'''约束的定位能够在程序模拟中的任何时候完成。将约束应用到行为模型的过程分为两步: 首先，确定与约束条件一致的初始的''' 目标轨迹 goal trajectories'''集；然后，将行为规则应用到这些路径上，去选择那些不违反约束条件的路径。

Correlating and building off of the findings proposed in his work with Musse, Thalmann, working alongside Bratislava Ulicny and Pablo de Heras Ciechomski, proposed a new model which allowed for interactive authoring of agents at the level of an individual, a group of agents and the entirety of a crowd. A brush metaphor is introduced to distribute, model and control crowd members in real-time with immediate feedback.<ref>{{cite book |doi=10.1145/1028523.1028555 |chapter=Crowdbrush |title=Proceedings of the 2004 ACM SIGGRAPH/Eurographics symposium on Computer animation – SCA '04 |pages=243–52 |year=2004 |last1=Ulicny |first1=Branislav |last2=Ciechomski |first2=Pablo de Heras |last3=Thalmann |first3=Daniel |isbn=978-3-905673-14-2 }}</ref>

Correlating and building off of the findings proposed in his work with Musse, Thalmann, working alongside Bratislava Ulicny and Pablo de Heras Ciechomski, proposed a new model which allowed for interactive authoring of agents at the level of an individual, a group of agents and the entirety of a crowd. A brush metaphor is introduced to distribute, model and control crowd members in real-time with immediate feedback.

塔尔曼基于他和米塞尔合作中提出的研究成果，和布拉迪斯拉发·乌利奇尼 Bratislava Ulicny以及巴勃罗·德·赫拉斯·切科姆斯基 Pablo de Heras Ciechomski提出了一种新的模型。这种模型允许在个人、一个群组和整个群体的层面上进行主体的''' 交互式创作 Interactive Authoring'''。他们引入了一个刷子隐喻，在即时反馈的情况下来进行实时分配、建模和控制人群成员。.<ref>{{cite book |doi=10.1145/1028523.1028555 |chapter=Crowdbrush |title=Proceedings of the 2004 ACM SIGGRAPH/Eurographics symposium on Computer animation – SCA '04 |pages=243–52 |year=2004 |last1=Ulicny |first1=Branislav |last2=Ciechomski |first2=Pablo de Heras |last3=Thalmann |first3=Daniel |isbn=978-3-905673-14-2 }}</ref>

== Crowd dynamics 人群动态==

One of the major goals in crowd simulation is to steer crowds realistically and recreate human dynamic behaviors.

One of the major goals in crowd simulation is to steer crowds realistically and recreate human dynamic behaviors.

人群模拟的主要目标之一是真实地引导人群并重现人类的动态行为。

There exists several overarching approaches to crowd simulation and AI, each one providing advantages and disadvantages based on crowd size and time scale. Time scale refers to how the objective of the simulation also affects the length of the simulation. For example, researching social questions such as how ideologies are spread amongst a population will result in a much longer running simulation since such an event can span up to months or years. Using those two characteristics, researchers have attempted to apply classifications to better evaluate and organize existing crowd simulators.<ref>{{cite journal |doi=10.1145/1842722.1842725 |title=Crowd modeling and simulation technologies |journal=ACM Transactions on Modeling and Computer Simulation |volume=20 |issue=4 |pages=1–35 |year=2010 |last1=Zhou |first1=Suiping |last2=Chen |first2=Dan |last3=Cai |first3=Wentong |last4=Luo |first4=Linbo |last5=Low |first5=Malcolm Yoke Hean |last6=Tian |first6=Feng |last7=Tay |first7=Victor Su-Han |last8=Ong |first8=Darren Wee Sze |last9=Hamilton |first9=Benjamin D. |hdl=10149/118022 |url=https://research.tees.ac.uk/ws/files/6477586/Accepted_manuscript.pdf }}</ref>

There exists several overarching approaches to crowd simulation and AI, each one providing advantages and disadvantages based on crowd size and time scale. Time scale refers to how the objective of the simulation also affects the length of the simulation. For example, researching social questions such as how ideologies are spread amongst a population will result in a much longer running simulation since such an event can span up to months or years. Using those two characteristics, researchers have attempted to apply classifications to better evaluate and organize existing crowd simulators.

人群模拟和人工智能有几种主要的方法，每种方法根据人群规模和时间尺度具有不同的优缺点。时间尺度是指仿真的目标如何也会影响仿真的时间长度。例如，研究诸如意识形态在人群中的分布等社会问题将导致模拟运行的时间更长，因为意识形态分布这样的事件可能长达数月或数年。利用这两个特点，研究人员已经试图分类现有的人群模拟器，以更好地评估和组织它们。<ref>{{cite journal |doi=10.1145/1842722.1842725 |title=Crowd modeling and simulation technologies |journal=ACM Transactions on Modeling and Computer Simulation |volume=20 |issue=4 |pages=1–35 |year=2010 |last1=Zhou |first1=Suiping |last2=Chen |first2=Dan |last3=Cai |first3=Wentong |last4=Luo |first4=Linbo |last5=Low |first5=Malcolm Yoke Hean |last6=Tian |first6=Feng |last7=Tay |first7=Victor Su-Han |last8=Ong |first8=Darren Wee Sze |last9=Hamilton |first9=Benjamin D. |hdl=10149/118022 |url=https://research.tees.ac.uk/ws/files/6477586/Accepted_manuscript.pdf }}</ref>

;Flow-based Approach: Flow based crowd simulations focus on the crowd as a whole rather than its components. As such individuals do not have any distinctive behaviors that occur due to input from their surroundings and behavioral factors are largely reduced.<ref name="Degond">{{cite journal|title= Congestion in a macroscopic model of self-driven particles modeling gregariousness| last1=Degond| first1=Pierre| last2=Navoret| first2=Laurent| last3=Bon| first3=Richard| last4=Sanchez| first4=David| journal=[[Journal of Statistical Physics]]| volume=138| issue=1–3| year=2010| pages=85–125| publisher=[[Springer Publishing|Springer]]| doi=10.1007/s10955-009-9879-x| arxiv=0908.1817| bibcode=2010JSP...138...85D}}</ref> This model is mainly used to estimate the flow of movement of a large and dense crowd in a given environment. Best used in studying large crowd, short time objectives.

Flow-based Approach: Flow based crowd simulations focus on the crowd as a whole rather than its components. As such individuals do not have any distinctive behaviors that occur due to input from their surroundings and behavioral factors are largely reduced. This model is mainly used to estimate the flow of movement of a large and dense crowd in a given environment. Best used in studying large crowd, short time objectives.

''' 基于流的方法 Flow-based Approach''': 基于流的人群模拟关注于人群作为一个整体，而不是人群的各种组成部分。这样人群中的个体没有任何独特的行为是由于他们周围的环境引起的，行为因素在很大程度上被减少了。<ref name="Degond">{{cite journal|title= Congestion in a macroscopic model of self-driven particles modeling gregariousness| last1=Degond| first1=Pierre| last2=Navoret| first2=Laurent| last3=Bon| first3=Richard| last4=Sanchez| first4=David| journal=[[Journal of Statistical Physics]]| volume=138| issue=1–3| year=2010| pages=85–125| publisher=[[Springer Publishing|Springer]]| doi=10.1007/s10955-009-9879-x| arxiv=0908.1817| bibcode=2010JSP...138...85D}}</ref>该模型主要用于估计给定环境下大型密集人群的'''运动流 the flow of movement'''。最适用于研究人群大、时间短的目标。

;Entity-based Approach: Models that implement a set of physical, predefined, and global laws meant to simulate social/psychological factors that occur in individuals that are a part of a crowd fall under this category. Entities in this case do not have the capacity to, in a sense, think for themselves. All movements are determined by the global laws being enforced on them. Simulations that use this model often do so to research crowd dynamics such as jamming and flocking. Small to medium-sized crowds with short term objectives fit this approach best.

Entity-based Approach: Models that implement a set of physical, predefined, and global laws meant to simulate social/psychological factors that occur in individuals that are a part of a crowd fall under this category. Entities in this case do not have the capacity to, in a sense, think for themselves. All movements are determined by the global laws being enforced on them. Simulations that use this model often do so to research crowd dynamics such as jamming and flocking. Small to medium-sized crowds with short term objectives fit this approach best.

''' 基于实体的方法 Entity-based Approach''': 属于这种类别方法的模型会实施一系列物理的、预先确定的整体规则，这些规则旨在模拟发生在属于群体的个人身上的社会/心理因素。在这类模型中，实体在某种意义上没有自己思考的能力。他们所有运动都是由整体规则决定的。这个模型的仿真模拟经常用来研究人群动态，例如拥挤jamming和聚集。中小型群体和较短时间的目标适合使用这种方法。

;Agent-based Approach: Characterized by autonomous, interacting individuals. Each agent of a crowd in this approach, is given a degree of intelligence; they can react to each situation on their own based on a set of decision rules. Information used to decide on an action is obtained locally from the agent's' surroundings. Most often, this approach is used for simulating realistic crowd behavior as the researcher is given complete freedom to implement any behaviors.

Agent-based Approach: Characterized by autonomous, interacting individuals. Each agent of a crowd in this approach, is given a degree of intelligence; they can react to each situation on their own based on a set of decision rules. Information used to decide on an action is obtained locally from the agent's' surroundings. Most often, this approach is used for simulating realistic crowd behavior as the researcher is given complete freedom to implement any behaviors.

''' 基于主体的方法 Agent-based Approach''': 该方法的特点是拥有自治的、互动的个体。在这种方法中，人群中的每个主体都被赋予了一定程度的智能; 他们可以根据一组决策规则自行对每个情况做出反应。主体用来决定一个行动的信息是从其周围获得的局部信息。这种方法最常见是被用来模拟现实的人群行为，因为研究人员可以完全自由地执行任何行为。

== Particle systems 粒子系统==

One way to simulate virtual crowds is to use a [[particle system]]. Particle systems were first introduced in computer graphics by W. T. Reeves in 1983.<ref>{{cite journal |doi=10.1117/12.261175 |title=From crowd simulation to airbag deployment: Particle systems, a new paradigm of simulation |journal=Journal of Electronic Imaging |volume=6 |pages=94–107 |year=1997 |last1=Cohen |first1=Eyal |last2=Cohen |first2=Eyal |last3=Najman |first3=Laurent |bibcode=1997JEI.....6...94B }}</ref> A particle system is a collection of a number of individual elements or ''particles''. Each particle is able to act autonomously and is assigned a set of physical attributes (such as color, size and velocity).

One way to simulate virtual crowds is to use a particle system. Particle systems were first introduced in computer graphics by W. T. Reeves in 1983. A particle system is a collection of a number of individual elements or particles. Each particle is able to act autonomously and is assigned a set of physical attributes (such as color, size and velocity).

一种模拟虚拟人群的方法是使用'''粒子系统 Particle System'''。1983年，W·T·里夫斯 W. T. Reeves 在'''计算机图形学 Computer Graphics'''中首次引入了粒子系统。<ref>{{cite journal |doi=10.1117/12.261175 |title=From crowd simulation to airbag deployment: Particle systems, a new paradigm of simulation |journal=Journal of Electronic Imaging |volume=6 |pages=94–107 |year=1997 |last1=Cohen |first1=Eyal |last2=Cohen |first2=Eyal |last3=Najman |first3=Laurent |bibcode=1997JEI.....6...94B }}</ref>粒子系统是很多单个元素或粒子的集合。每个粒子都能够自主行动，并被赋予一组物理属性(如颜色、大小和速度)。

A particle system is dynamic, in that the movements of the particles change over time. A particle system's movement is what makes it so desirable and easy to implement. Calculating the movements of these particles takes very little time. It simply involves physics: the sum of all the forces acting on a particle determines its motion. Forces such as gravity, friction and force from a collision, and social forces like the attractive force of a goal.

A particle system is dynamic, in that the movements of the particles change over time. A particle system's movement is what makes it so desirable and easy to implement. Calculating the movements of these particles takes very little time. It simply involves physics: the sum of all the forces acting on a particle determines its motion. Forces such as gravity, friction and force from a collision, and social forces like the attractive force of a goal.

粒子系统是动态的，因为粒子的运动随着时间而改变。粒子系统的运动使这种方法很理想，且易于实现。计算这些粒子的运动只需要很少的时间。它仅仅涉及到物理学: 作用在一个粒子上的所有力的总和决定了它的运动。力包括了诸如重力、摩擦力、碰撞产生的力，以及诸如目标的吸引力之类的社会力。

Usually each particle has a [[velocity vector]] and a [[position vector]], containing information about the particle's current velocity and position respectively. The particles next position is calculated by adding its velocity vector to its position vector. A very simple operation (again why particle systems are so desirable). Its velocity vector changes over time, in response to the forces acting on the particle. For example, a collision with another particle will cause it to change direction.

Usually each particle has a velocity vector and a position vector, containing information about the particle's current velocity and position respectively. The particles next position is calculated by adding its velocity vector to its position vector. A very simple operation (again why particle systems are so desirable). Its velocity vector changes over time, in response to the forces acting on the particle. For example, a collision with another particle will cause it to change direction.

通常每个粒子都有一个速度矢量和一个位置矢量，分别包含粒子当前的速度和位置信息。将粒子的速度矢量加到其位置矢量上，从而计算粒子的下一个位置。这是一个非常简单的操作(并再次说明了为什么粒子系统如此理想)。速度矢量在作用力影响下随时间变化。例如，与另一个粒子的碰撞将导致一个粒子改变方向。

Particles systems have been widely used in films for effects such as explosions, for water effects in the 2000 movie ''[[The Perfect Storm (film)|The Perfect Storm]]'', and simulated gas in the 1994 film ''[[The Mask (1994 film)|the Mask]]''.

Particles systems have been widely used in films for effects such as explosions, for water effects in the 2000 movie The Perfect Storm, and simulated gas in the 1994 film the Mask.

粒子系统已经广泛应用于电影，如制作爆炸特效。具体的例子包括2000年的电影《完美风暴 The Perfect Storm》的水特效，以及1994年的电影《面具 Mask》的模拟气体特效等。

Particles systems, however, do have some drawbacks. It can be a bad idea to use a particle system to simulate agents in a crowd that the director will move on command, as determining which particles belong to the agent and which do not is very difficult.

Particles systems, however, do have some drawbacks. It can be a bad idea to use a particle system to simulate agents in a crowd that the director will move on command, as determining which particles belong to the agent and which do not is very difficult.

然而，粒子系统确实有一些缺点。使用粒子系统模拟那些领导会根据指令行动行动的人群中的主体，可能是个坏主意，因为确定哪些粒子属于主体，哪些不属于主体是非常困难的。

--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） crowd that the director will move on command 不确定是否是“根据领导的指令统一行动的人群”这个意思

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]） crowd that the director will move on command 领导会根据指令行动的人群

=== Algorithm by Patil and Van Den Berg, 帕蒂尔 Patil和范登博格 Van Den Berg的算法===

This algorithm was designed for relatively simplistic crowds, where each agent in the crowd only desires to get to its own goal destination while also avoiding obstacles.<ref>{{cite journal |doi=10.1109/TVCG.2010.33 |pmid=21149879 |title=Directing Crowd Simulations Using Navigation Fields |journal=IEEE Transactions on Visualization and Computer Graphics |volume=17 |issue=2 |pages=244–54 |year=2011 |last1=Patil |first1=Sachin |last2=Van Den Berg |first2=Jur |last3=Curtis |first3=Sean |last4=Lin |first4=Ming C |last5=Manocha |first5=Dinesh |citeseerx=10.1.1.183.7823 }}</ref> This algorithm could be used for simulating a crowd in Times Square.

This algorithm was designed for relatively simplistic crowds, where each agent in the crowd only desires to get to its own goal destination while also avoiding obstacles. This algorithm could be used for simulating a crowd in Times Square.

帕蒂尔 Patil和范登博格 Van Den Berg的算法是针对相对简单的群体设计的，群体中的每个主体只希望到达自己的目的地，同时避开障碍物。<ref>{{cite journal |doi=10.1109/TVCG.2010.33 |pmid=21149879 |title=Directing Crowd Simulations Using Navigation Fields |journal=IEEE Transactions on Visualization and Computer Graphics |volume=17 |issue=2 |pages=244–54 |year=2011 |last1=Patil |first1=Sachin |last2=Van Den Berg |first2=Jur |last3=Curtis |first3=Sean |last4=Lin |first4=Ming C |last5=Manocha |first5=Dinesh |citeseerx=10.1.1.183.7823 }}</ref> 这个算法可以用来模拟时代广场 Times Square的人群。

Patils algorithm's most important and distinctive feature is that it utilizes the concept of ''navigation fields'' for directing agents. This is different from a guidance field; a guidance field is an area around the agent in which the agent is capable of "seeing"/detecting information. Guidance fields are typically used for avoiding obstacles, dynamic obstacles (obstacles that move) in particular. Every agent possesses its own guidance field. A navigation field, on the other hand, is a vector field which calculates the minimum cost path for every agent so that every agent arrives at its own goal position.

Patils algorithm's most important and distinctive feature is that it utilizes the concept of navigation fields for directing agents. This is different from a guidance field; a guidance field is an area around the agent in which the agent is capable of "seeing"/detecting information. Guidance fields are typically used for avoiding obstacles, dynamic obstacles (obstacles that move) in particular. Every agent possesses its own guidance field. A navigation field, on the other hand, is a vector field which calculates the minimum cost path for every agent so that every agent arrives at its own goal position.

帕蒂尔算法最重要且具有区分性的特征是它利用了''' 导航场 Navigation Fields'''的概念来指导主体。这不同于''' 指导场 Guidance Field'''; 指导场是主体周围的一个区域，主体可以在其中“看到”或检测到信息。指导场通常用于避开障碍物，特别是动态障碍物（移动的障碍物）。每个主体都有自己的指导场。另一方面，导航场是一个''' 向量场 vector field'''，它为每个主体计算''' 最小代价路径 minimum cost path'''，使每个主体到达自己的目标位置。

The navigation field can only be used properly when a path exists from every free (non-obstacle) position in the environment to one of the goal positions. The navigation field is computed using coordinates of the static objects in the environment, goal positions for each agent, and the guidance field for each agent. In order to guarantee that every agent reaches its own goal the navigation field must be free of local minima, except for the presence of sinks at the specified goals.

The navigation field can only be used properly when a path exists from every free (non-obstacle) position in the environment to one of the goal positions. The navigation field is computed using coordinates of the static objects in the environment, goal positions for each agent, and the guidance field for each agent. In order to guarantee that every agent reaches its own goal the navigation field must be free of local minima, except for the presence of sinks at the specified goals.

只有当从环境中的每一个''' 自由（无障碍）位置 free (non-obstacle) position'''到某一目标位置的路径存在时，导航场才能被正确使用。导航场是使用环境中静态对象的坐标、每个主体的目标位置和指导场计算的。为了保证每个主体达到自己的目标，导航场必须不受''' 局部极小值 local minima'''的限制，除非在特定目标处存在''' 汇 sinks'''。

The running time of computing the navigation field is <math>O(m*n*log(mn))</math>, where m × n is the grid dimension (similar to [[Dijkstra's algorithm]]). Thus, the algorithm is only dependent on the grid resolution and not dependent on the number of agents in the environment. However, this algorithm has a high memory cost.

The running time of computing the navigation field is <math>O(m*n*log(mn))</math>, where m × n is the grid dimension (similar to Dijkstra's algorithm). Thus, the algorithm is only dependent on the grid resolution and not dependent on the number of agents in the environment. However, this algorithm has a high memory cost.

计算导航场的运行时间的公式是
<math>O(m*n*log(mn))</math>，
其中 m × n 是网格维数(类似于迪杰斯特拉算法)。因此，该算法仅依赖于网格分辨率，而不依赖于环境中的主体数量。但是，这种算法的内存消耗很大。

=== Individual behavior modelling 个体行为建模===

One set of techniques for AI-based crowd simulation is to model crowd behavior by advanced simulation of individual agent motivations and decision-making. Generally, this means each agent is assigned some set of variables that measure various traits or statuses such as stress, personality, or different goals. This results in more realistic crowd behavior though may be more computationally intensive than simpler techniques.

One set of techniques for AI-based crowd simulation is to model crowd behavior by advanced simulation of individual agent motivations and decision-making. Generally, this means each agent is assigned some set of variables that measure various traits or statuses such as stress, personality, or different goals. This results in more realistic crowd behavior though may be more computationally intensive than simpler techniques.

基于AI的群体建模的技术之一，是通过对个体动机和决策的高级模拟来建立群体行为模型。一般来说，这意味着每个主体都被分配了一组变量来衡量不同的特征或状态，比如压力、人格或不同的目标。这导致更真实的群体行为，虽然可能比使用简单的技术计算量更大。

==== Personality-based models 基于人格的模型====

One method of creating individualistic behavior for crowd agents is through the use of personality traits.<ref>{{cite book |doi=10.1145/2019406.2019413 |chapter=Simulating heterogeneous crowd behaviors using personality trait theory |title=Proceedings of the 2011 ACM SIGGRAPH/Eurographics Symposium on Computer Animation – SCA '11 |pages=43–52 |year=2011 |last1=Guy |first1=Stephen J. |last2=Kim |first2=Sujeong |last3=Lin |first3=Ming C. |last4=Manocha |first4=Dinesh |isbn=978-1-4503-0923-3 }}</ref> Each agent may have certain aspects of their personality tuned based on a formula that associates aspects such as aggressiveness or impulsiveness with variables that govern the agents' behavior. One way this association can be found is through a subjective study in which agents are randomly assigned values for these variables and participants are asked to describe each agent in terms of these personality traits. A regression may then be done to determine a correlation between these traits and the agent variables. The personality traits can then be tuned and have an appropriate effect on agent behavior.

One method of creating individualistic behavior for crowd agents is through the use of personality traits. Each agent may have certain aspects of their personality tuned based on a formula that associates aspects such as aggressiveness or impulsiveness with variables that govern the agents' behavior. One way this association can be found is through a subjective study in which agents are randomly assigned values for these variables and participants are asked to describe each agent in terms of these personality traits. A regression may then be done to determine a correlation between these traits and the agent variables. The personality traits can then be tuned and have an appropriate effect on agent behavior.

为人群的主体创建个体行为模型的一种方法是使用人格特质。<ref>{{cite book |doi=10.1145/2019406.2019413 |chapter=Simulating heterogeneous crowd behaviors using personality trait theory |title=Proceedings of the 2011 ACM SIGGRAPH/Eurographics Symposium on Computer Animation – SCA '11 |pages=43–52 |year=2011 |last1=Guy |first1=Stephen J. |last2=Kim |first2=Sujeong |last3=Lin |first3=Ming C. |last4=Manocha |first4=Dinesh |isbn=978-1-4503-0923-3 }}</ref> 每个主体可能会根据一个公式调整他们个性的某些方面，这个公式将侵略性或冲动性等方面与控制主体行为的变量联系起来。发现这种联系的一个方法是通过一个主观的研究，在这个研究中主体被随机分配这些变量的值，参与者被要求用这些人格特征来描述每个主体。然后可以进行回归，以确定这些特征和主体变量之间的相关性。人格特征可以被调整，并对主体行为产生适当的影响。

The [[Big Five personality traits|OCEAN personality model]] has been used to define a mapping between personality traits and crowd simulation parameters. Automating crowd parameter tuning with personality traits provides easy authoring of scenarios with heterogeneous crowds.<ref>{{cite journal|last1=Durupinar|first1=Funda|last2=Pelechano|first2=Nuria|last3=Allbeck|first3=Jan|last4=Gudukbay|first4=Ugur|last5=Badler|first5=Norman I.|title=How the Ocean Personality Model Affects the Perception of Crowds|journal=IEEE Computer Graphics and Applications|date=2011|volume=31|issue=3|pages=22–31|doi=10.1109/MCG.2009.105|pmid=24808089|hdl=11693/11800|hdl-access=free}}</ref>

The OCEAN personality model has been used to define a mapping between personality traits and crowd simulation parameters. Automating crowd parameter tuning with personality traits provides easy authoring of scenarios with heterogeneous crowds.

''' 五大人格特征模型 Big Five personality traits/OCEAN personality model'''定义了人格特质与人群模拟参数之间的映射关系。自动调整人群的人格特征参数使得能够在错杂的人群中简便地创作场景。<ref>{{cite journal|last1=Durupinar|first1=Funda|last2=Pelechano|first2=Nuria|last3=Allbeck|first3=Jan|last4=Gudukbay|first4=Ugur|last5=Badler|first5=Norman I.|title=How the Ocean Personality Model Affects the Perception of Crowds|journal=IEEE Computer Graphics and Applications|date=2011|volume=31|issue=3|pages=22–31|doi=10.1109/MCG.2009.105|pmid=24808089|hdl=11693/11800|hdl-access=free}}</ref>

==== Stress-based model 基于压力的模型====

The behavior of crowds in high-stress situations can be modeled using [[General adaptation syndrome|General Adaptation Syndrome]] theory.<ref>{{cite book |doi=10.1145/2159616.2159626 |chapter=Interactive simulation of dynamic crowd behaviors using general adaptation syndrome theory |title=Proceedings of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games – I3D '12 |pages=55–62 |year=2012 |last1=Kim |first1=Sujeong |last2=Guy |first2=Stephen J. |last3=Manocha |first3=Dinesh |last4=Lin |first4=Ming C. |isbn=978-1-4503-1194-6 |citeseerx=10.1.1.673.3693 }}</ref> Agent behavior is affected by various stressors from their environment categorized into four prototypes: time pressure, area pressure, positional stressors, and interpersonal stressors, each with associated mathematical models.

The behavior of crowds in high-stress situations can be modeled using General Adaptation Syndrome theory.l Agent behavior is affected by various stressors from their environment categorized into four prototypes: time pressure, area pressure, positional stressors, and interpersonal stressors, each with associated mathematical models.

高压状态下的人群行为可以用''' 一般适应综合症理论 General Adaptation Syndrome theory'''来模拟。<ref>{{cite book |doi=10.1145/2159616.2159626 |chapter=Interactive simulation of dynamic crowd behaviors using general adaptation syndrome theory |title=Proceedings of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games – I3D '12 |pages=55–62 |year=2012 |last1=Kim |first1=Sujeong |last2=Guy |first2=Stephen J. |last3=Manocha |first3=Dinesh |last4=Lin |first4=Ming C. |isbn=978-1-4503-1194-6 |citeseerx=10.1.1.673.3693 }}</ref> 主体行为受到来自所处环境的各种压力源的影响，包括''' 时间压力 time pressure'''、''' 区域压力 area pressure'''、''' 位置压力 positional stressors'''和''' 人际压力 interpersonal stressors'''四个原型，每个原型都有相关的数学模型。

''Time pressure'' refers to stressors related to a time limit in reaching a particular goal. An example would be a street crossing with a timed walk signal or boarding a train before the doors are closed. This prototype is modeled by the following formula:

Time pressure refers to stressors related to a time limit in reaching a particular goal. An example would be a street crossing with a timed walk signal or boarding a train before the doors are closed. This prototype is modeled by the following formula:

时间压力是和达到特定目标的时间限制有关的压力源。例如，一个设有限时步行信号的十字路口，或在车门关闭前上车。这个原型是按照以下公式建模的:

<math>I_t = max(t_e - t_a, 0)</math>

where <math display="inline">I_t</math> is the intensity of the time pressure as a function of the estimated time to reach the goal <math display="inline">t_e</math> and a time constraint <math>t_a</math>.

where <math display="inline">I_t</math> is the intensity of the time pressure as a function of the estimated time to reach the goal <math display="inline">t_e</math> and a time constraint <math>t_a</math>.

其中 <math display="inline">I_t</math> 是时间压力强度，它是关于达到目标的估计时间<math display="inline">t_e</math>和时间限制 <math>t_a</math>的函数。

''Area pressure'' refers to stessors as a result of an environmental condition. Examples would be noise or heat in an area. The intensity of this stressor is constant over a particular area and is modeled by the following formula:

Area pressure refers to stessors as a result of an environmental condition. Examples would be noise or heat in an area. The intensity of this stressor is constant over a particular area and is modeled by the following formula:

区域压力是指由于环境条件而产生的压力。例如某个地区的噪音或热量。这种压力源的强度在某一特定地区是恒定的，其模型如下:

<math>I_a = \begin{cases} c & \text{if }p_a\in A \\ 0 & \text{if }p_a\not\in A \end{cases}</math>

where <math display="inline">I_a</math> is the intensity of the area pressure, <math display="inline">p_a</math> is the position of the agent in an area <math>A</math>, and <math>c</math> is a constant.

where <math display="inline">I_a</math> is the intensity of the area pressure, <math display="inline">p_a</math> is the position of the agent in an area <math>A</math>, and <math>c</math> is a constant.

其中<math display="inline">I_a</math>是区域压力强度，<math display="inline">p_a</math> 是主体在A区的位置，c是一个常数。

''Positional stressors'' refer to stressors associated with a local source of stress. The intensity of this stressor increases as an agent approaches the source of the stress. An example would be a fire or a dynamic object such as an assailant. It can be modeled by the following formula:

Positional stressors refer to stressors associated with a local source of stress. The intensity of this stressor increases as an agent approaches the source of the stress. An example would be a fire or a dynamic object such as an assailant. It can be modeled by the following formula:

位置压力是指与局部压力源相关的压力源。这种压力源的强度随着主体接近压力源而增加。一个例子就是火灾，或运动的物体比如攻击者。它可以用下面的公式来模拟:

<math>I_p = \lVert p_a - p_s \rVert</math>

where <math>I_p</math> is the intensity of the positional stressor, <math>p_a</math> is the position of the agent and <math>p_s</math> is the position of the stressor. Alternatively, stressors that generate high stress over a large area (such as a fire) can be modeled using a Gaussian distribution with standard deviation <math>\sigma</math>:

where <math>I_p</math> is the intensity of the positional stressor, <math>p_a</math> is the position of the agent and <math>p_s</math> is the position of the stressor. Alternatively, stressors that generate high stress over a large area (such as a fire) can be modeled using a Gaussian distribution with standard deviation <math>\sigma</math>:

其中 <math>I_p</math> 是位置压力源的强度，<math>p_a</math> 是主体的位置，<math>p_s</math> 是压力源的位置。另外，在一个大的区域产生高压力的压力源(如火灾)，可以用一个带有正态分布的标准差<math>\sigma</math>的模型来模拟:

<math>I_p = \mathcal{N}(p_a - p_s, \sigma)</math>

''Interpersonal stressors'' are stressors as a result of crowding by nearby agents. It can be modeled by the following formula:

Interpersonal stressors are stressors as a result of crowding by nearby agents. It can be modeled by the following formula:

人际压力源是由邻近主体的拥挤程度而产生的压力源。它可以用下面的公式来模拟:

<math>I_i = max(n_c - n_p, 0)</math>

where <math>I_i</math> is the intensity of the interpersonal stressor, <math>n_c</math> is the current number of neighbors within a unit space and <math>n_p</math> is the preferred number of neighbors within a unit space for that particular agent.

where <math>I_i</math> is the intensity of the interpersonal stressor, <math>n_c</math> is the current number of neighbors within a unit space and <math>n_p</math> is the preferred number of neighbors within a unit space for that particular agent.

其中<math>I_i</math>表示人际压力源的强度，<math>n_c</math> 表示当前单位空间内邻居的数量，<math>n_p</math> 表示单位空间内该特定主体理想的邻居数量。

The ''perceived stress'' follows [[Stevens' law|Steven's Law]] and is modeled by the formula:

The perceived stress follows Steven's Law and is modeled by the formula:

感知到的压力遵循'''史蒂芬定律 Steven's Law '''，并可以用下面的公式模拟:

<math>\psi(I) = kI^n</math>

where <math>\psi(I)</math> is the perceived stress for a stress level <math>I</math>, <math>k</math> is a scale factor, and <math>n</math> is an exponent depending on the stressor type.

where <math>\psi(I)</math> is the perceived stress for a stress level <math>I</math>, <math>k</math> is a scale factor, and <math>n</math> is an exponent depending on the stressor type.

其中<math>\psi(I)</math>是感知到的压力水平，<math>I</math>是客观的压力水平，<math>k</math> 是一个比例系数，<math>n</math>是一个取决于压力源类型的指数。

An agent's ''stress response'' can be found with the following formula:

An agent's stress response can be found with the following formula:

一个主体的压力反应可以通过以下公式得出:

<math>{dS \over dt} = \begin{cases} \alpha & \text{if } \psi > S \\ (-\alpha \leq {d\psi \over dt} \leq \alpha) & \text{if } \psi = S\\ -\alpha & \text{if } \psi < S\end{cases}</math>

where <math>S</math> is the stress response capped at a maximum value of <math>\beta</math> and <math>\alpha</math> is the maximum rate at which an agent's stress response can change.

where <math>S</math> is the stress response capped at a maximum value of <math>\beta</math> and <math>\alpha</math> is the maximum rate at which an agent's stress response can change.

其中，<math>S</math>是压力反应，它受到最大<math>\beta</math>值的限制，<math>\alpha</math>是主体的压力反应可以改变的最大速率。

Examples of notable crowd AI simulation can be seen in [[New Line Cinema]]'s ''[[The Lord of the Rings (film series)|The Lord of the Rings]]'' films, where AI armies of thousands of characters battle each other. This crowd simulation was done using [[Weta Digital]]'s [[Massive (software)|Massive software]].

Examples of notable crowd AI simulation can be seen in New Line Cinema's The Lord of the Rings films, where AI armies of thousands of characters battle each other. This crowd simulation was done using Weta Digital's Massive software.

值得注意的AI模拟例子可以在'''新线电影公司 New Line Cinema'''的《指环王 Lord of the Rings》系列电影中看到。在这部电影中，成千上万的AI角色互相争斗。这个人群模拟是用威塔数码公司 Weta Digital的Massive软件完成的。

=== Sociology 社会学===

''Crowd simulation'' can also refer to simulations based on [[group dynamics]] and [[crowd psychology]], often in public safety planning. In this case, the focus is just the behavior of the crowd, and not the visual realism of the simulation. Crowds have been studied as a scientific interest since the end of the 19th Century. A lot of research has focused on the collective social behavior of people at social gatherings, assemblies, protests, rebellions, concerts, sporting events and religious ceremonies. Gaining insight into natural human behavior under varying types of stressful situations will allow better models to be created which can be used to develop crowd controlling strategies.

Crowd simulation can also refer to simulations based on group dynamics and crowd psychology, often in public safety planning. In this case, the focus is just the behavior of the crowd, and not the visual realism of the simulation. Crowds have been studied as a scientific interest since the end of the 19th Century. A lot of research has focused on the collective social behavior of people at social gatherings, assemblies, protests, rebellions, concerts, sporting events and religious ceremonies. Gaining insight into natural human behavior under varying types of stressful situations will allow better models to be created which can be used to develop crowd controlling strategies.

人群模拟也可以指基于'''群体动力学 Group Dynamics'''和'''群体心理学 Crowd Psychology'''的模拟，通常用于'''公共安全规划 Public Safety Planning'''。在这种情况下，研究的焦点只是人群的行为，而不是模拟的视觉真实性。自19世纪末以来，人们一直将人群作为一种科学兴趣进行研究。许多研究都关注人们在社会聚会、集会、抗议、叛乱、音乐会、体育赛事和宗教仪式上的集体社会行为。了解不同类型压力情况下的人类自然行为将创建更好的、可用于发展人群控制策略的模型。

''Emergency response teams'' such as policemen, the National Guard, military and even volunteers must undergo some type of crowd control training. Using researched principles of human behavior in crowds can give disaster training designers more elements to incorporate to create realistic simulated disasters. Crowd behavior can be observed during panic and non-panic conditions. When natural and unnatural events toss social ideals into a twisting chaotic bind, such as the events of 9/11 and hurricane Katrina, humanity's social capabilities are truly put to the test. Military programs are looking more towards simulated training, involving emergency responses, due to their cost-effective technology as well as how effective the learning can be transferred to the real world.{{Citation needed|date=October 2012}} Many events that may start out controlled can have a twisting event that turns them into catastrophic situations, where decisions need to be made on the spot. It is these situations in which crowd dynamical understanding would play a vital role in reducing the potential for anarchy.

Emergency response teams such as policemen, the National Guard, military and even volunteers must undergo some type of crowd control training. Using researched principles of human behavior in crowds can give disaster training designers more elements to incorporate to create realistic simulated disasters. Crowd behavior can be observed during panic and non-panic conditions. When natural and unnatural events toss social ideals into a twisting chaotic bind, such as the events of 9/11 and hurricane Katrina, humanity's social capabilities are truly put to the test. Military programs are looking more towards simulated training, involving emergency responses, due to their cost-effective technology as well as how effective the learning can be transferred to the real world. Many events that may start out controlled can have a twisting event that turns them into catastrophic situations, where decisions need to be made on the spot. It is these situations in which crowd dynamical understanding would play a vital role in reducing the potential for anarchy.

警察、国民警卫队、军队甚至志愿者等紧急反应小组都必须接受某种形式的人群控制培训。运用研究出的群体中人类的行为原则，灾难训练设计者可以有更多元素来创造更逼真的模拟灾难。在恐慌和非恐慌情况下可以观察到群体行为。当自然和非自然的事件使社会理想状况陷入扭曲混乱的局面，比如“911”和飓风卡特里娜事件时，人类的社会能力就在真正地接受考验。军事项目更倾向于以模拟形式进行训练和应急反应，因为它们是成本低效益高的形式，并且能够有效地将所学转移到现实世界。许多事件一开始可能受到控制，但后来反转发展成为灾难性情况，因此需要当场做出决定。正是在这些情况下，对人群的动态理解将发挥重要作用，以减少出现混乱的可能性。

''Modeling'' techniques of crowds vary from holistic or network approaches to understanding individualistic or behavioral aspects of each agent. For example, the Social Force Model describes a need for individuals to find a balance between social interaction and physical interaction. An approach that incorporates both aspects, and is able to adapt depending on the situation, would better describe natural human behavior, always incorporating some measure of unpredictability. With the use of multi-agent models understanding these complex behaviors has become a much more comprehensible task. With the use of this type of software, systems can now be tested under extreme conditions, and simulate conditions over long periods of time in the matter of seconds.

Modeling techniques of crowds vary from holistic or network approaches to understanding individualistic or behavioral aspects of each agent. For example, the Social Force Model describes a need for individuals to find a balance between social interaction and physical interaction. An approach that incorporates both aspects, and is able to adapt depending on the situation, would better describe natural human behavior, always incorporating some measure of unpredictability. With the use of multi-agent models understanding these complex behaviors has become a much more comprehensible task. With the use of this type of software, systems can now be tested under extreme conditions, and simulate conditions over long periods of time in the matter of seconds.

群体的建模技术从整体或网络到理解每个主体的个人或行为方面都各不相同。例如，'''社会力模型 Social Force Model'''描述了个体在社会互动和物理互动之间寻求平衡的需求。一种结合了这两个方面，并且能够根据具体情境进行调整的方法，将更好地描述自然的人类行为，并总是包含一些对不可预测性的测量。随着多主体模型的使用，理解这些复杂的行为已经成为一个易懂的任务。利用这种类型的软件，现在研究人员可以在极端条件下测试系统，也可以在几秒钟内模拟长期的情况变化。

In some situations, the behavior of swarms of non-human animals can be used as an experimental model of crowd behavior. The panic behavior of ants when exposed to a [[Insect repellent|repellent]] chemical in a confined space with limited exit routes has been found to have both similarities and differences to equivalent human behavior.<ref>N. Shiwakoti et al., "Animal dynamics based approach for modeling pedestrian crowd egress under panic conditions", Transportation Research Part B 45 (2011) 1433-1449.</ref><ref>S. Wang et al., "Behavior of Ants Escaping from a Single-Exit Room", PLoS One. 2015; 10(6): e0131784.</ref>

In some situations, the behavior of swarms of non-human animals can be used as an experimental model of crowd behavior. The panic behavior of ants when exposed to a repellent chemical in a confined space with limited exit routes has been found to have both similarities and differences to equivalent human behavior.

在某些情况下，非人类动物群体的行为可以作为群体行为的一个实验模型。人们发现，蚂蚁在出口有限且封闭的空间里暴露于令人反感的化学物质中时产生的惊慌行为，与同样情况下的人类行为既有相似之处，也有不同之处。<ref>N. Shiwakoti et al., "Animal dynamics based approach for modeling pedestrian crowd egress under panic conditions", Transportation Research Part B 45 (2011) 1433-1449.</ref><ref>S. Wang et al., "Behavior of Ants Escaping from a Single-Exit Room", PLoS One. 2015; 10(6): e0131784.</ref>

=== Modeling individual behaviors 个体行为建模===

Helbing proposed a model based on physics using a particle system and socio-psychological forces in order to describe human crowd behavior in panic situation, this is now called the Helbing Model. His work is based on how the average person would react in a certain situation. Although this is a good model, there are always different types of people present in the crowd and they each have their own individual characteristics as well as how they act in a group structure. For instance, one person may not react to a panic situation, while another may stops walking and interfere in the crowd dynamics as a whole. Furthermore, depending on the group structure, the individual action can change because the agent is part of a group, for example, returning to a dangerous place in order to rescue a member of that group. Helbing's model can be generalized incorporating individualism, as proposed by Braun, Musse, Oliveira and Bodmann.<ref name=":0" />

Helbing proposed a model based on physics using a particle system and socio-psychological forces in order to describe human crowd behavior in panic situation, this is now called the Helbing Model. His work is based on how the average person would react in a certain situation. Although this is a good model, there are always different types of people present in the crowd and they each have their own individual characteristics as well as how they act in a group structure. For instance, one person may not react to a panic situation, while another may stops walking and interfere in the crowd dynamics as a whole. Furthermore, depending on the group structure, the individual action can change because the agent is part of a group, for example, returning to a dangerous place in order to rescue a member of that group. Helbing's model can be generalized incorporating individualism, as proposed by Braun, Musse, Oliveira and Bodmann.

赫尔本 Helbing 提出了一个基于物理学的模型，使用粒子系统和社会心理力量来描述人群在恐慌情况下的行为，这个模型现在被称为''' 赫尔本模型 Helbing Model'''。他的工作基于在特定情况下普通人如何反应。虽然这是一个很好的模式，但是在人群中总是有不同类型的人，他们每个人都有自己的个人特点和在群体结构中的行为方式。例如，一个人可能不会对恐慌的情况做出反应，而另一个人可能会停下脚步并干扰整个人群的运动。此外，根据群体结构的不同，作为群体的一部分主体的个人行为可能会发生变化。例如，为了拯救该群体的一个成员而返回到一个危险的地方。如布劳恩 Braun, Musse,奥利韦拉 Oliveira和布罗德曼 Bodmann 提出的那样，赫尔本的模型可以概括为融入个人主义。<ref name=":0" />

In order to tackle this problem, individuality should be assigned to each agent, allowing to deal with different types of behaviors. Another aspect to tackle this problem is the possibility to group people, forming these group causes people to change their behavior as a function of part of the group structure. Each agent (individual) can be defined according to the following parameters:

In order to tackle this problem, individuality should be assigned to each agent, allowing to deal with different types of behaviors. Another aspect to tackle this problem is the possibility to group people, forming these group causes people to change their behavior as a function of part of the group structure. Each agent (individual) can be defined according to the following parameters:

为了解决这个问题，应该给每个主体分配个性，从而允许模型处理不同类型的行为。解决这个问题的另一个方法是把人们分组，形成这样的群体会使人们作为群体结构的一部分而改变他们的行为。

--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]）我觉得原文Another aspect……到forming these group……再到 part of the group structure，应该是两句，是从forming处分开的两句话）

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）我觉得原文和翻译都没有问题

每个主体(个体)可以根据以下参数定义:

# Id – Agent identifier

Id – Agent identifier

Id：主体标识符

# IdFamily – Identifier of the family. A family is a predefined group formed by agents who know each other

IdFamily – Identifier of the family. A family is a predefined group formed by agents who know each other

IdFamily：家族标识符。家族是由相互认识的主体组成的一个预先设定的组。

# DE – Dependence level of the agent which mimics the need for help. Values [0,1]

DE – Dependence level of the agent which mimics the need for help. Values [0,1]

DE：主体的'''依赖水平 Dependence level'''，用来模拟主体对他人帮助的需求。取值范围：[0,1]

# AL – Altruism level representing the tendency to help other agents. Values [0,1]

AL – Altruism level representing the tendency to help other agents. Values [0,1]

AL：'''利他主义水平 Altruism Level'''，代表了帮助他人的倾向。取值范围：[0,1]

# vi – Speed of the agent

vi – Speed of the agent

vi ：主体的速度

To model the effect of the dependence parameter with ''individual agents'', the equation is defined as:

To model the effect of the dependence parameter with individual agents, the equation is defined as:

为了模拟单个主体的因变量参数的效应方程定义为:

: <math>v_i = (1-DE)v_{max}</math>

<math>v_i = (1-DE)v_{max}</math>

<math>v_i = (1-DE)v_{max}</math>

When evaluating the speed of the agent, it is clear that if the value of the dependence factor, DE, is equal to one, then the person would be fully disabled making him unable to move. If the dependence factor is equal to zero, then the person is able to run at his max speed.

When evaluating the speed of the agent, it is clear that if the value of the dependence factor, DE, is equal to one, then the person would be fully disabled making him unable to move. If the dependence factor is equal to zero, then the person is able to run at his max speed.

在评估主体的速度时，很明显，如果依赖因子 DE 的值等于1，则表示该主体完全丧失行动能力。如果依赖因子等于0，那么该主体能够以其最大速度运动。

Group formation is related to the Altruism force which is implemented as an interaction force between two or more agents who are part of the same family. Mathematically, it is described as the following:

Group formation is related to the Altruism force which is implemented as an interaction force between two or more agents who are part of the same family. Mathematically, it is described as the following:

群体的形成与利他主义力有关。利他主义力是同一家族中两个或两个以上成员之间的相互作用力。用数学方法，它被描述为:

: <math>F\overline{a}_i = K\sum \left ( AL_iDE_j \times \left | d_{ij}-d_{ip} \right | \times e_{ij} \right ) </math>

<math>F\overline{a}_i = K\sum \left ( AL_iDE_j \times \left | d_{ij}-d_{ip} \right | \times e_{ij} \right ) </math>

<math>F\overline{a}_i = K\sum \left ( AL_iDE_j \times \left | d_{ij}-d_{ip} \right | \times e_{ij} \right ) </math>

where:

where:

其中:

: {{math|''dij''}} represents the distance between two agents with the origin at the position of the agent;

: {{math|''dij''}} represents the distance between two agents with the origin at the position of the agent;

{{math|''dij''}}表示两个主体之间的距离，原点设在主体的位置;

: {{math|''dip''}} is the distance vector point from the agents to the door's position {{math|''p''}} of the simulation environment;

: {{math|''dip''}} is the distance vector point from the agents to the door's position of the simulation environment;

{{math|''dip''}}是模拟环境中从主体到门的位置的距离矢量点;

: {{math|''K''}} is a constant;

: {{math|''K''}} is a constant;

{{math|''K''}}是一个常数

: {{math|''eij''}} is the unitary vector with the origin at position i.

: {{math|''eij''}} is the unitary vector with the origin at position i.

{{math|''eij''}}是原点位于i处的酉向量。

Consequently, the greater the parameter {{math|''ALi''}} of agent {{math|''i''}}, the bigger will be {{math|''Fāi''}} which points to the agent {{math|''j''}} and has the high level of {{math|''DEj''}}. When both agents are close enough to each other, the one with high {{math|''DE''}} (agent {{math|''j''}} in this example) adopts the value of agent {{math|''i''}} (<math>DE_j = DE_i</math>). This means that the evacuation ability of agent {{math|''i''}} is shared with agent {{math|''j''}} and both start moving together.

Consequently, the greater the parameter of agent , the bigger will be which points to the agent and has the high level of . When both agents are close enough to each other, the one with high (agent in this example) adopts the value of agent (<math>DE_j = DE_i</math>). This means that the evacuation ability of agent is shared with agent and both start moving together.

因此，主体{{math|''i''}}的利他主义水平{{math|''ALi''}}越高，指向主体{{math|''j''}}的{{math|''Fāi''}}就越大，{{math|''j''}}也具有较高的依赖水平{{math|''DEj''}}。当两个代理彼此足够接近时，具有较高依赖水平的主体(本例中的主体{{math|''j''}})就采用主体{{math|''i''}}依赖水平(<math>DE_j = DE_i</math>)。这意味着主体{{math|''i''}}与主体{{math|''j''}}共享疏散能力，两者一起开始移动。

By using these applying these equations in model testing using a normally distributed population, the results are fairly similar to the Helbing Model.

By using these applying these equations in model testing using a normally distributed population, the results are fairly similar to the Helbing Model.

将这些方程应用于正态分布人口的模型检验，结果与赫尔本模型非常相似。

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）这句前半句英文的结构我没太懂，中文的翻译也不知道是否准确

--[[用户:Vicky|Vicky]]（[[用户讨论:Vicky|讨论]]）By using these (applying these) equations in model testing (using a normally distributed population)

The places where this would be helpful would be in an evacuation scenario. Take for example, an evacuation of a building in the case of a fire. Taking into account the characteristics of individual agents and their group performances, determining the outcome of how the crowd would exit the building is critically important in creating the layout of the building.<ref name=":0">{{cite book |doi=10.1109/CASA.2003.1199317 |chapter=Modeling individual behaviors in crowd simulation |title=Proceedings 11th IEEE International Workshop on Program Comprehension |pages=143–8 |year=2003 |last1=Braun |first1=A. |last2=Musse |first2=S.R. |last3=De Oliveira |first3=L.P.L. |last4=Bodmann |first4=B.E.J. |isbn=978-0-7695-1934-0 }}</ref>

The places where this would be helpful would be in an evacuation scenario. Take for example, an evacuation of a building in the case of a fire. Taking into account the characteristics of individual agents and their group performances, determining the outcome of how the crowd would exit the building is critically important in creating the layout of the building.

这种模型会对疏散场景有所帮助。以发生火灾的建筑物疏散为例，考虑到个体的特点和他们在团队的表现从而确定人群会如何离开建筑的结果，对于设计建筑的布局至关重要。<ref name=":0">{{cite book |doi=10.1109/CASA.2003.1199317 |chapter=Modeling individual behaviors in crowd simulation |title=Proceedings 11th IEEE International Workshop on Program Comprehension |pages=143–8 |year=2003 |last1=Braun |first1=A. |last2=Musse |first2=S.R. |last3=De Oliveira |first3=L.P.L. |last4=Bodmann |first4=B.E.J. |isbn=978-0-7695-1934-0 }}</ref>

=== Leader behavior during evacuation simulations 疏散模拟中的领导者行为===

As described earlier, the '''Helbing Model''' is used as the basics for crowd behavior. This same type of behavior model is used for evacuation simulations.

As described earlier, the Helbing Model is used as the basics for crowd behavior. This same type of behavior model is used for evacuation simulations.

如前所述，赫尔本模型被用作群体行为的基础。同样类型的行为模型也同样被用于疏散模拟。

In general, the first thing that has to be assumed is that not everyone has knowledge about the environment or where there are and aren't hazards. From this assumption we can create three types of agents. The first type is a trained leader, this agent knows about the environment and is able to spread knowledge to other agents so they know how to exit from an environment. The next type of agent is an untrained leader, this agent does not know about the environment, however, as the agent explores the environment and gets information from other types of leaders, the agent is able to spread the knowledge about the environment. The last type of agent is a follower, this type of agent can only take information from other leaders and not be able to share the information with other agents.

In general, the first thing that has to be assumed is that not everyone has knowledge about the environment or where there are and aren't hazards. From this assumption we can create three types of agents. The first type is a trained leader, this agent knows about the environment and is able to spread knowledge to other agents so they know how to exit from an environment. The next type of agent is an untrained leader, this agent does not know about the environment, however, as the agent explores the environment and gets information from other types of leaders, the agent is able to spread the knowledge about the environment. The last type of agent is a follower, this type of agent can only take information from other leaders and not be able to share the information with other agents.

一般来说，首先需要假定的是，并不是每个人都了解环境或了解哪里有没有危险。根据这个假设，我们可以创建三种类型的主体。第一种类型是训练有素的领导者，这种主体了解环境并能够将知识传播给其他主体，因此他们知道如何从这种环境中退出。第二种类型的主体是未经训练的领导者。他们不了解环境，但是当这种主体探索环境并从其他类型的领导者那里获得信息时，他们能够传播有关环境的知识。最后一种类型是跟随者，这种类型的主体只能从其他领导者那里获取信息，不能与其他主体共享信息。

The implementation of these types of agents is fairly straightforward. The leaders in the environment have a map of the environment saved as one of their attributes. An untrained leader and followers will start out with an empty map as their attribute. Untrained leaders and followers will start exploring an environment by themselves and create a map of walkable and unwalkable locations. Leaders and untrained leaders (once they have the knowledge), will share information with other agents depending on their proximity. They will share information about which points on the grid are blocked, the local sub-graphs and the dangers in the area.

The implementation of these types of agents is fairly straightforward. The leaders in the environment have a map of the environment saved as one of their attributes. An untrained leader and followers will start out with an empty map as their attribute. Untrained leaders and followers will start exploring an environment by themselves and create a map of walkable and unwalkable locations. Leaders and untrained leaders (once they have the knowledge), will share information with other agents depending on their proximity. They will share information about which points on the grid are blocked, the local sub-graphs and the dangers in the area.

实现这些主体类型的方法相当简单直接。对于领导者，环境地图被保存为他们的属性之一。未经训练的领导者和追随者具有一张空地图的属性。未经训练的领导者和追随者将自己开始探索环境，并创建一个具有适合和不适合走地点信息的地图。领导者和未受过训练的领导者(一旦他们掌握了知识) ，会根据与其他主体的接近程度来分享信息。他们分享的信息包括网格上哪些点被阻塞，局部子地图和该地区的危险。

There were two types of searching algorithms tried out for this implementation. There was the random search and the depth first search. A random search is where each of the agents go in any direction through the environment and try to find a pathway out. The depth first search is where agents follow one path as far as it can go then return and try another path if the path they traversed does not contain an exit. If was found that depth first search gave a speed up of 15 times versus a random search.<ref>{{cite journal |doi=10.1109/MCG.2006.133 |pmid=17120916 |title=Modeling Crowd and Trained Leader Behavior during Building Evacuation |journal=IEEE Computer Graphics and Applications |volume=26 |issue=6 |pages=80–6 |year=2006 |last1=Pelechano |first1=Nuria |last2=Badler |first2=Norman |hdl=2117/10047 |hdl-access=free }}</ref>

There were two types of searching algorithms tried out for this implementation. There was the random search and the depth first search. A random search is where each of the agents go in any direction through the environment and try to find a pathway out. The depth first search is where agents follow one path as far as it can go then return and try another path if the path they traversed does not contain an exit. If was found that depth first search gave a speed up of 15 times versus a random search.

有两种类型的搜索算法试验了这种模型：''' 随机搜索 Random Search'''和'''深度优先搜索 Depth First Search'''。随机搜索是指每个主体在环境中朝任意方向前进，并试图找到一条出路。深度优先搜索是指主体尽可能沿着一条路径搜索，如果它们所经过的路径不包含出口则返回并尝试另一条路径。结果发现，深度优先搜索比随机搜索的速度快15倍。

=== Scalable simulations 可伸缩的模拟===

--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） Scalable 翻译为“可变的”会不会好一点？此处的搭配包括Scalable Agents，Scalable architecture 和Scalable simulations

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]） Scalable 好像没有“可变的”含义，可以是“可扩展的”

--[[用户:Vicky|Vicky]]（[[用户讨论:Vicky|讨论]]）可伸缩模拟或者可扩展模拟都可以

There are many different case situations that come into play in crowd simulations.<ref>{{cite book |doi=10.1109/ICPP.2008.20 |chapter=A Scalable Architecture for Crowd Simulation: Implementing a Parallel Action Server |title=2008 37th International Conference on ParallelProcessing |pages=430–7 |year=2008 |last1=Vigueras |first1=G. |last2=Lozano |first2=M. |last3=Pérez |first3=C. |last4=Orduña |first4=J.M. }}</ref> Recently, crowd simulation has been essential for the many virtual environment applications such as education, training, and entertainment. Many situations are based on the environment of the simulation or the behavior of the group of local agents. In virtual reality applications, every agent interacts with many other agents in the environment, calling for complex real-time interactions. Agents must have continuous changes in the environment since agent behaviors allow complex interactions. Scalable architecture can manage large crowds through the behavior and interactive rates. These situations will indicate how the crowds will act in multiple complex scenarios while several different situations are being applied. A situation can be any circumstance that has typical local behaviors. We can categorize all situations into two different kinds.

There are many different case situations that come into play in crowd simulations. Recently, crowd simulation has been essential for the many virtual environment applications such as education, training, and entertainment. Many situations are based on the environment of the simulation or the behavior of the group of local agents. In virtual reality applications, every agent interacts with many other agents in the environment, calling for complex real-time interactions. Agents must have continuous changes in the environment since agent behaviors allow complex interactions. Scalable architecture can manage large crowds through the behavior and interactive rates. These situations will indicate how the crowds will act in multiple complex scenarios while several different situations are being applied. A situation can be any circumstance that has typical local behaviors. We can categorize all situations into two different kinds.

在人群模拟中有许多不同的情况出现。<ref>{{cite book |doi=10.1109/ICPP.2008.20 |chapter=A Scalable Architecture for Crowd Simulation: Implementing a Parallel Action Server |title=2008 37th International Conference on Parallel Processing |pages=430–7 |year=2008 |last1=Vigueras |first1=G. |last2=Lozano |first2=M. |last3=Pérez |first3=C. |last4=Orduña |first4=J.M. }}</ref>近年来，人群模拟已经成为教育、训练、娱乐等虚拟环境应用中不可缺少的一部分。许多情况下的人群模拟是基于模拟的环境或一组局部主体的行为。在虚拟现实应用程序中，每个主体与环境中的许多其他主体进行交互，需要复杂的实时交互。由于主体行为允许复杂交互的特性，主体必须在环境中能够连续变化。'''可伸缩的架构 Scalable architecture'''可以通过行为和交互速率来管理大的人群。当应用几种不同的情境时，可以揭示人群在复杂的情况下的运动行为。情境可以是任何具有典型局部行为的环境。

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）这两句说不通，situation到底指什么？

--[[用户:Vicky|Vick]]（[[用户讨论:Vicky|讨论]]）英语表达有些重复，可以省略第一个situation的翻译

我们可以把所有的情境分为两种不同的类型。

''Spatial situation'' is a situation that has a region where the environment affects the local agents. For instance, a crowd waiting in line for a ticket booth would be displaying a spatial situation. Other examples may be a bus stop or an ATM where characters act upon their environment. Therefore, we would consider 'bus stop' as the situation if the behavior of the agents are to be getting on or off a bus.

Spatial situation is a situation that has a region where the environment affects the local agents. For instance, a crowd waiting in line for a ticket booth would be displaying a spatial situation. Other examples may be a bus stop or an ATM where characters act upon their environment. Therefore, we would consider 'bus stop' as the situation if the behavior of the agents are to be getting on or off a bus.

'''空间情境 Spatial Situation'''是指环境影响局部主体的区域。例如，一个售票亭前排队等候的人群就展示可一个空间情境。其他的例子，可能是一个公交车总站或者一个ATM机，在那里人依据其环境做出行动。因此，如果主体的行为可以是上车或下车，我们就可以把“公交车站”看作是一种空间情境。

''Non-Spatial situation'' has no region in the environment because this only involves the behavior of the crowd. The relationship of the local agents is an important factor to consider when determining behavior. An example would be a group of friends walking together. Typical behavior of characters that are friends would all move along with each other. This means that 'friendship' would be the situation among the typical behavior of walking together.

Non-Spatial situation has no region in the environment because this only involves the behavior of the crowd. The relationship of the local agents is an important factor to consider when determining behavior. An example would be a group of friends walking together. Typical behavior of characters that are friends would all move along with each other. This means that 'friendship' would be the situation among the typical behavior of walking together.

'''非空间情境 Non-Spatial situation'''是没有空间区域的环境，因为它只涉及到人群的行为。在决定行为时，局部主体之间的关系是一个重要的因素。一个例子是一群朋友一起散步。朋友的典型行为是各个主体都会互相影响。这意味着“友谊”是作为一起散步的典型行为的情境。

The structure of any situation is built upon four components, Behavior functions, Sensors, States, and Event Rules. Behavior functions represent what the characters behaviors are specific to the situation. Sensors are the sensing capability for agents to see and respond to events. States are the different motions and state transitions used only for the local behaviors. Event rule is the way to connect different events to their specific behaviors. While a character is being put into a situation, these four components are considered at the same time. For spatial situations, the components are added when the individual initially enters the environment that influences the character. For non-spatial situations, the character is affected only once the user assigns the situation to the character. The four components are removed when the agent is taken away from its situations region or the situation itself is removed. The dynamic adding and removing of the situations lets us achieve scalable agents.

The structure of any situation is built upon four components, Behavior functions, Sensors, States, and Event Rules. Behavior functions represent what the characters behaviors are specific to the situation. Sensors are the sensing capability for agents to see and respond to events. States are the different motions and state transitions used only for the local behaviors. Event rule is the way to connect different events to their specific behaviors. While a character is being put into a situation, these four components are considered at the same time. For spatial situations, the components are added when the individual initially enters the environment that influences the character. For non-spatial situations, the character is affected only once the user assigns the situation to the character. The four components are removed when the agent is taken away from its situations region or the situation itself is removed. The dynamic adding and removing of the situations lets us achieve scalable agents.

任何情境的结构都建立在四个组件之上: '''行为函数 Behavior Functions'''、'''传感器 Sensors'''、'''状态 States'''和'''事件规则 Event Rules'''。行为函数表示特定情况下的特定行为。传感器是一种感知能力，可以让主体看到并对事件做出反应。状态是仅用于局部行为的不同运动和状态转移。事件规则是将不同的事件与其特定的行为联系起来的方法。当一个角色被置于一个情境中时，这四个组件将被同时考虑。对于空间情景，当个体最初进入影响角色的环境时就添加组件。对于非空间情境，只有当用户将情境赋给角色时，角色才会受到影响。当主体被带离情境区域或情境本身被移除时，这四个组件被移除。动态地添加和删除这些情境使我们能够实现'''可伸缩的主体 Scalable Agents'''。

== Human-like behaviors and crowd AI 类人行为和群体人工智能==

[[File:Crowd simulation, Covent Garden.jpg|thumb|A crowd simulation of [[Covent Garden square]], London, showing a crowd of pedestrian agents reacting to a street performer]]

A crowd simulation of [[Covent Garden square, London, showing a crowd of pedestrian agents reacting to a street performer]]

一个人群模拟[[ Covent Garden 广场，伦敦，显示了一群行人主体对街头艺人的反应]]

{{Main|Swarm intelligence}}

To simulate more aspects of human activities in a crowd, more is needed than path and motion planning. Complex social interactions, smart object manipulation, and hybrid models are challenges in this area.Simulated crowd behavior is inspired by the flow of real-world crowds. Behavioral patterns, movement speeds and densities, and anomalies are [[crowd analysis|analyzed]] across many environments and building types. Individuals are [[crowd tracking|tracked]] and their movements are documented such that algorithms can be derived and implemented into crowd simulations.

To simulate more aspects of human activities in a crowd, more is needed than path and motion planning. Complex social interactions, smart object manipulation, and hybrid models are challenges in this area.Simulated crowd behavior is inspired by the flow of real-world crowds. Behavioral patterns, movement speeds and densities, and anomalies are analyzed across many environments and building types. Individuals are tracked and their movements are documented such that algorithms can be derived and implemented into crowd simulations.

为了模拟在人群中人类活动的更多方面，我们需要路径和运动规划以外的更多东西。复杂的社会交互、智能对象操纵和混合模型是这一领域的挑战。模拟人群行为的灵感来自于现实世界中的人群流。研究者分析了人群在许多环境和建筑类型中的行为模式、运动速度和密度以及异常情况。个体的行动被跟踪记录下来，这样就可以得到算法并应用到人群模拟中。

Individual entities in a crowd are also called [[Software agent|agents]]. In order for a crowd to behave realistically each agent should act autonomously (be capable of acting independently of the other agents). This idea is referred to as an ''agent-based model.'' Moreover, it is usually desired that the agents act with some degree of intelligence (i.e. the agents should not perform actions that would cause them to harm themselves). For agents to make intelligent and realistic decisions, they should act in accordance with their surrounding environment, react to its changes, and react to the other agents.

Individual entities in a crowd are also called agents. In order for a crowd to behave realistically each agent should act autonomously (be capable of acting independently of the other agents). This idea is referred to as an agent-based model. Moreover, it is usually desired that the agents act with some degree of intelligence (i.e. the agents should not perform actions that would cause them to harm themselves). For agents to make intelligent and realistic decisions, they should act in accordance with their surrounding environment, react to its changes, and react to the other agents.

群体中的独立的个体也称为主体。为了让一个群体真实地行动，每个主体应该自主地(能够独立于其他主体地)行动。这个想法被称为'''基于主体的模型 Agent-based Model'''。此外，人们通常希望主体的行为具有一定程度的智慧(即，主体不应采取伤害自己的行动)。为了使主体做出明智和真实的决定，他们应该根据他们周围的环境采取行动，对环境变化作出反应，并对其他主体作出反应。

=== Rule-based AI 基于规则的人工智能===

[[File:MaslowsHierarchyOfNeeds.svg|alt=Maslow's Hierarchy of Needs|thumb|Maslow's Hierarchy of Needs]]

Maslow's Hierarchy of Needs

马斯洛的需求层次理论

In rule-based AI, virtual agents follow scripts: "if this happens, do that". This is a good approach to take if agents with different roles are required, such as a main character and several background characters. This type of AI is usually implemented with a hierarchy, such as in [[Maslow's hierarchy of needs]], where the lower the need lies in the hierarchy, the stronger it is.

In rule-based AI, virtual agents follow scripts: "if this happens, do that". This is a good approach to take if agents with different roles are required, such as a main character and several background characters. This type of AI is usually implemented with a hierarchy, such as in Maslow's hierarchy of needs, where the lower the need lies in the hierarchy, the stronger it is.

在'''基于规则的人工智能 Rule-based AI'''中，虚拟主体遵循以下规则: “如果发生了这种情况，就那样做”。如果需要具有不同角色的主体，比如一个主角和几个背景角色，那么这是一个很好的方法。这种类型的人工智能通常是用层次结构来实现的，例如在'''马斯洛的需求层次结构 Maslow's hierarchy of needs'''中，需求层级越低，需求就越强。

For example, consider a student walking to class who encounters an explosion and runs away. The theory behind this is initially the first four levels of his needs are met, and the student is acting according to his need for self-actualization. When the explosion happens his safety is threatened which is a much stronger need, causing him to act according to that need.

For example, consider a student walking to class who encounters an explosion and runs away. The theory behind this is initially the first four levels of his needs are met, and the student is acting according to his need for self-actualization. When the explosion happens his safety is threatened which is a much stronger need, causing him to act according to that need.

例如，假设一个学生在走向教室的路上遭遇了爆炸并逃跑了。这背后的理论是他的前4个层次的需求得到了满足，并且学生是具有'''自我实现 self-actualization'''的需求并依次按照需求来行动。当爆炸发生时，他的安全受到威胁，这是一个比自我实现更强烈的需要，使他按照这种需要行事。

This approach is scalable, and can be applied to crowds with a large number of agents. Rule-based AI, however, does have some drawbacks. Most notably the behavior of the agents can become very predictable, which may cause a crowd to behave unrealistically.

This approach is scalable, and can be applied to crowds with a large number of agents. Rule-based AI, however, does have some drawbacks. Most notably the behavior of the agents can become very predictable, which may cause a crowd to behave unrealistically.

这种方法是可扩展的，可以应用于拥有大量主体的人群。然而，基于规则的人工智能确实有一些缺点。最值得注意的缺点是，主体的行为会变得可预测性很强，这可能导致群体的行为不现实。

=== Learning AI 学习型人工智能===

In learning AI, virtual characters behave in ways that have been tested to help them achieve their goals. Agents experiment with their environment or a sample environment which is similar to their real one.

In learning AI, virtual characters behave in ways that have been tested to help them achieve their goals. Agents experiment with their environment or a sample environment which is similar to their real one.

在'''学习型人工智能 Learning AI'''中，虚拟角色用一种经过了测试的方式帮助他们自己实现目标。主体用他们的环境或者一个类似于他们真实环境的样本环境进行测试。

Agents perform a variety of actions and learn from their mistakes. Each agent alters its behavior in response to rewards and punishments it receives from the environment. Over time, each agent would develop behaviors that are consistently more likely to earn high rewards.

Agents perform a variety of actions and learn from their mistakes. Each agent alters its behavior in response to rewards and punishments it receives from the environment. Over time, each agent would develop behaviors that are consistently more likely to earn high rewards.

主体进行各种各样的行动并从他们的错误中吸取经验。每个主体根据从环境中得到的奖励和惩罚改变其行为。随着时间的推移，每个主体都会发展更有可能获得高回报的行为。

If this approach is used, along with a large number of possible behaviors and a complex environment agents will act in a realistic and unpredictable fashion.

If this approach is used, along with a large number of possible behaviors and a complex environment agents will act in a realistic and unpredictable fashion.

如果使用这种方法，加上大量可能的行为和复杂的环境，主体将以一种现实的和不可预测的方式行事。

==== Algorithms 算法====

There are a wide variety of machine learning algorithms that can be applied to crowd simulations.

There are a wide variety of machine learning algorithms that can be applied to crowd simulations.

人群模拟现在已经有各种各样可以应用的机器学习算法。

Q-Learning is an algorithm residing under machine learning's sub field known as reinforcement learning. A basic overview of the algorithm is that each action is assigned a Q value and each agent is given the directive to always perform the action with the highest Q value. In this case learning applies to the way in which Q values are assigned, which is entirely reward based. When an agent comes in contact with a state, s, and action, a, the algorithm then estimates the total reward value that an agent would receive for performing that state action pair. After calculating this data, it is then stored in the agent's knowledge and the agent proceeds to act from there.

Q-Learning is an algorithm residing under machine learning's sub field known as reinforcement learning. A basic overview of the algorithm is that each action is assigned a Q value and each agent is given the directive to always perform the action with the highest Q value. In this case learning applies to the way in which Q values are assigned, which is entirely reward based. When an agent comes in contact with a state, s, and action, a, the algorithm then estimates the total reward value that an agent would receive for performing that state action pair. After calculating this data, it is then stored in the agent's knowledge and the agent proceeds to act from there.

Q-Learning是机器学习的子领域强化学习中的一个算法。一个对该算法的基本描述：每个动作都被分配了一个Q值，每个主体都被赋予一个总是执行Q值最高的动作的指令。在这种情况下，学习效果取决于分配Q值的方式，这完全是基于奖励的。当一个主体接触到一个状态 s 和一个动作 a 时，算法就会估计这个主体执行这个'''状态动作对 state action pair'''所能得到的总回报值。在计算这些数据之后，它们被存储在主体的知识中，主体依据这些知识开始行动。

（--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） learning applies to the way in which Q values are assigned 翻译为学习效果取决于分配 q 值的方式，不知是否正确）

（--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）我觉得应该不是学习效果，应该是学习的内容）

The agent will constantly alter its behavior depending on the best Q value available to it. And as it explores more and more of the environment, it will eventually learn the most optimal state action pairs to perform in almost every situation.

The agent will constantly alter its behavior depending on the best Q value available to it. And as it explores more and more of the environment, it will eventually learn the most optimal state action pairs to perform in almost every situation.

主体会根据最佳Q值不断地改变自己的行为。随着它对环境的探索越来越多，它最终将学习到几乎每种情况下最佳状态动作对。

The following function outlines the bulk of the algorithm:

The following function outlines the bulk of the algorithm:

下面的函数概括了算法的大部分内容:

:''Q(s, a) ←− r + maxaQ(s', a')''

Q(s, a) ←− r + maxaQ(s', a')

Q(s, a) ←− r + maxaQ(s', a')

Given a state s and action a, r and s’ are the reward and state after performing (s,a), and a' is the range over all the actions.<ref>Torrey, L. Crowd Simulation Via Multi-agent Reinforcement Learning. In: ''Proceedings of the Sixth AAAI Conference On Artificial Intelligence and Interactive Digital Entertainment''. AAAI Press, Menlo Park (2010)</ref>

Given a state s and action a, r and s’ are the reward and state after performing (s,a), and a' is the range over all the actions.

给定一个状态s和动作a，r和s’是执行(s,a)后的奖励和状态，a'动作集。<ref>Torrey, L. Crowd Simulation Via Multi-agent Reinforcement Learning. In: ''Proceedings of the Sixth AAAI Conference On Artificial Intelligence and Interactive Digital Entertainment''. AAAI Press, Menlo Park (2010)</ref>

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）r和s这句，我觉得s应该是s’吧

--[[用户:Vicky|Vicky]]（[[用户讨论:Vicky|讨论]]）同意S'

== Crowd rendering and animation 人群渲染和动画==

Rendering and animating a large number of agents realistically, especially in real time, is challenging. To reduce the complexity of 3D rendering of large-scale crowds, techniques like culling (discarding unimportant objects), impostors(image-based rendering) and decreasing levels of detail have been used.<ref>{{cite journal |doi=10.1109/76.825720 |title=Real-time display of virtual humans: Levels of details and impostors |journal=IEEE Transactions on Circuits and Systems for Video Technology |volume=10 |issue=2 |pages=207–17 |year=2000 |last1=Aubel |first1=A. |last2=Boulic |first2=R. |last3=Thalmann |first3=D. }}</ref>

Rendering and animating a large number of agents realistically, especially in real time, is challenging. To reduce the complexity of 3D rendering of large-scale crowds, techniques like culling (discarding unimportant objects), impostors(image-based rendering) and decreasing levels of detail have been used.

对大量主体进行真实地、特别是实时地渲染和动画绘制，是具有挑战性的。为了降低大规模人群3D渲染的复杂性，人们使用了剔除（舍弃不重要的物体）、顶替（基于图像的渲染）和降低细节的级别等技术。<ref>{{cite journal |doi=10.1109/76.825720 |title=Real-time display of virtual humans: Levels of details and impostors |journal=IEEE Transactions on Circuits and Systems for Video Technology |volume=10 |issue=2 |pages=207–17 |year=2000 |last1=Aubel |first1=A. |last2=Boulic |first2=R. |last3=Thalmann |first3=D. }}</ref>

Variations in appearance, body shape and size, accessories and behavior(social or cultural) exist in real crowds, and lack of variety affects the realism of visual simulations. Existing systems can create virtual crowds with varying texture,<ref name="Maim et al 2009"/> color,<ref>{{cite book |last1=Gosselin |first1=David R. |last2=Sander |first2=Pedro V. |last3=Mitchell |first3=Jason L. |chapter=Drawing a Crowd |editor1-first=Wolfgang |editor1-last=Engel |title=ShaderX3: Advanced Rendering Techniques in DirectX and OpenGL |publisher=Charles River Media |location=Cambridge, MA |year=2004 |pages=505–17 }}</ref> size, shape and animation.<ref name="Thalmann et al 2009"/>

Variations in appearance, body shape and size, accessories and behavior(social or cultural) exist in real crowds, and lack of variety affects the realism of visual simulations. Existing systems can create virtual crowds with varying texture, size, shape and animation.

真实的人群中存在着外貌、体型大小、附件和（社会的或文化的）行为的差异，缺乏多样性的模型会影响视觉模拟的真实性。现有的系统可以创建具有不同肌理、<ref name="Maim et al 2009"/> 颜色、<ref>{{cite book |last1=Gosselin |first1=David R. |last2=Sander |first2=Pedro V. |last3=Mitchell |first3=Jason L. |chapter=Drawing a Crowd |editor1-first=Wolfgang |editor1-last=Engel |title=ShaderX3: Advanced Rendering Techniques in DirectX and OpenGL |publisher=Charles River Media |location=Cambridge, MA |year=2004 |pages=505–17 }}</ref> 大小、形状和动画的虚拟人群。<ref name="Thalmann et al 2009"/>

（--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]）最后一个animation译为运动画面了，译为“动画”呢？存疑）

（--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）动画吧）

== Real world applications 在真实世界的应用==

=== Virtual cinematography 虚拟电影摄影===

Crowd simulations have been used widely across films as a cost-effective and realistic alternative from hiring actors and capturing shots that would otherwise be unrealistic. A significant example of its use lies in [[The Lord of the Rings (film series)]]. One of the most glaring problems for the production team in the initial stages were large-scale battles, as the author of the novels, J. R. R. Tolkien, envisioned them to have at least 50,000 participants. Such a number was unrealistic had they decided to only attempt to hire real actors and actresses. Instead they decided to use CG to simulate these scenes through the use of the Multiple Agent Simulation System in a Virtual Environment, otherwise known as MASSIVE. The Human Logic Engine based [[Autodesk Maya|Maya]] plugin for crowd simulation, [[Miarmy]], was used for the development of these sequences. The software allowed the filmmakers to provide each character model an agent based A.I. that could utilize a library of 350 animations. Based on sight, hearing, and touch parameters generated from the simulation, agents would react uniquely to each situation. Thus each simulation of the scene was unpredictable. The final product clearly displayed the advantages to using crowd simulation software.<ref>http://people.ucalgary.ca/~far/Lectures/SENG697/PDF/tutorials/2002/Multiple_Agent_Simulation_System_in_a_Virtual_Environment.pdf Davis Guy. Multiple Agent Simulation System in a Virtual Environment.</ref>

Crowd simulations have been used widely across films as a cost-effective and realistic alternative from hiring actors and capturing shots that would otherwise be unrealistic. A significant example of its use lies in The Lord of the Rings (film series). One of the most glaring problems for the production team in the initial stages were large-scale battles, as the author of the novels, J. R. R. Tolkien, envisioned them to have at least 50,000 participants. Such a number was unrealistic had they decided to only attempt to hire real actors and actresses. Instead they decided to use CG to simulate these scenes through the use of the Multiple Agent Simulation System in a Virtual Environment, otherwise known as MASSIVE. The Human Logic Engine based Maya plugin for crowd simulation, Miarmy, was used for the development of these sequences. The software allowed the filmmakers to provide each character model an agent based A.I. that could utilize a library of 350 animations. Based on sight, hearing, and touch parameters generated from the simulation, agents would react uniquely to each situation. Thus each simulation of the scene was unpredictable. The final product clearly displayed the advantages to using crowd simulation software.

人群模拟已经被广泛应用于电影中，它是一种相较雇佣演员和捕捉镜头来说更加低成本高收益且现实的替代方式，使用其他方法将是不真实的。电影《指环王》系列就是一个重要的例子。最初，制作团队面临最突出的问题之一是大规模的战斗，因为小说的作者约翰·罗纳德·瑞尔·托尔金 J. R. R. Tolkien设想这些战斗至少有50,000名参与者。如果制作团队决定只雇佣真人演员，这么多参与者是不现实的。他们决定使用CG来代替模拟这些场景，使用虚拟环境中的'''多主体仿真系统 Multiple Agent Simulation System'''，也就是众所周知的 MASSIVE 。'''群集动画 Miarmy'''，一个基于'''人类逻辑引擎 Human Logic Engine'''的人群模拟 Maya 插件，被用于开发这些动作序列。该软件允许制片人为每个角色提供一个基于主体的人工智能模型，这个模型可以利用一个有350个动画的数据库。基于通过模拟产生的视觉、听觉和触觉参数，主体将对每种不同的情况做出特定反应。因此，每个场景的模拟都是不可预知的。最终作品清晰地展示了使用人群模拟软件的优势。<ref>http://people.ucalgary.ca/~far/Lectures/SENG697/PDF/tutorials/2002/Multiple_Agent_Simulation_System_in_a_Virtual_Environment.pdf Davis Guy. Multiple Agent Simulation System in a Virtual Environment.</ref>

=== Urban planning 城市规划===

The development of crowd simulation software has become a modern and useful tool in designing urban environments. Whereas the traditional method of urban planning relies on maps and abstract sketches, a digital simulation is more capable of conveying both form and intent of design from architect to pedestrian. For example, street signs and traffic lights are localized visual cues that influence pedestrians to move and behave accordingly. Following this logic, a person is able to move from point A to point B in a way that is efficient and that a collective group of people can operate more effectively as a result. In a broader sense, bus systems and roadside restaurants serve a spatial purpose in their locations through an understanding of human movement patterns.<ref>http://papers.cumincad.org/data/works/att/ecaade2008_160.content.pdf Aschwanden, Gideon. Halatsch, Jan. Schmitt, Gerhard. Crowd Simulation for Urban Planning.</ref> The [[SimCity]] video game series exemplifies this concept in a more simplistic manner. In this series, the player assigns city development in designated zones while maintaining a healthy budget. The progression from empty land to a bustling city is fully controlled by the player's choices and the digital citizens behave as according to the city's design and events.

The development of crowd simulation software has become a modern and useful tool in designing urban environments. Whereas the traditional method of urban planning relies on maps and abstract sketches, a digital simulation is more capable of conveying both form and intent of design from architect to pedestrian. For example, street signs and traffic lights are localized visual cues that influence pedestrians to move and behave accordingly. Following this logic, a person is able to move from point A to point B in a way that is efficient and that a collective group of people can operate more effectively as a result. In a broader sense, bus systems and roadside restaurants serve a spatial purpose in their locations through an understanding of human movement patterns. The SimCity video game series exemplifies this concept in a more simplistic manner. In this series, the player assigns city development in designated zones while maintaining a healthy budget. The progression from empty land to a bustling city is fully controlled by the player's choices and the digital citizens behave as according to the city's design and events.

人群模拟软件的发展为现代城市环境设计提供了一个有用的工具。传统的城市规划方法依赖于地图和抽象的草图，而数字仿真更能将设计的形式和意图从建筑设计师传达给行人。例如，街道标志和交通灯是局部视觉线索，能够影响行人的移动和相应的行为。按照这个逻辑，如果一个人能够以一种高效的方式从 a 点移动到 b 点，一群人就能够高效地运作。在更广泛的意义上，公交系统和路边餐馆通过对人类运动模式的理解，在其位置起到空间上的作用。<ref>http://papers.cumincad.org/data/works/att/ecaade2008_160.content.pdf Aschwanden, Gideon. Halatsch, Jan. Schmitt, Gerhard. Crowd Simulation for Urban Planning.</ref>模拟城市SimCity视频游戏系列以一种更简单的方式举例说明了这个概念。在这个系列中，玩家在指定的区域指导城市的发展，同时保持平衡的收支。从空地到繁华城市的过程完全由玩家的选择来控制，而数字市民的行为则根据城市的设计和事件而定。

=== Evacuation and riot handling 疏散和暴乱处理===

Simulated realistic crowds can be used in training for riots handling, architecture, safety science (evacuation planning).

Simulated realistic crowds can be used in training for riots handling, architecture, safety science (evacuation planning).

模拟真实的人群可用于训练暴乱处理、建筑、安全科学（疏散计划 Evacuation ）。

=== Military 军队===

Being that crowd simulations are so prevalent in use for public planning and general order with regards to chaotic situations, many applications can be drawn for governmental and military simulations. Crowd modeling is essential in police and military simulation in order to train officers and soldiers to deal with mass gatherings of people. Not only do offensive combatants prove to be difficult for these individuals to handle, but noncombatant crowds play significant roles in making these aggressive situations more out of control. Game technology is used in order to simulate these situations for soldiers and technicians to practice their skills.<ref>{{cite journal |doi=10.1177/1046878107308092 |title=Integrating crowd-behavior modeling into military simulation using game technology |journal=Simulation & Gaming |volume=39 |pages=10–38 |year=2007 |last1=McKenzie |first1=F. D. |last2=Petty |first2=M. D. |last3=Kruszewski |first3=P. A. |last4=Gaskins |first4=R. C. |last5=Nguyen |first5=Q.-A. H. |last6=Seevinck |first6=J. |last7=Weisel |first7=E. W. }}</ref>

Being that crowd simulations are so prevalent in use for public planning and general order with regards to chaotic situations, many applications can be drawn for governmental and military simulations. Crowd modeling is essential in police and military simulation in order to train officers and soldiers to deal with mass gatherings of people. Not only do offensive combatants prove to be difficult for these individuals to handle, but noncombatant crowds play significant roles in making these aggressive situations more out of control. Game technology is used in order to simulate these situations for soldiers and technicians to practice their skills.

由于人群模拟是如此普遍地应用于公共规划和建立混乱情境中的一般秩序，许多应用程序可以用于绘制政府的和军队的模拟。为了训练官兵对群众集会的应对能力，人群模型在警察和军队推演中是必不可少的。在这些模拟中，不仅进攻性的战斗人员很难处理，非战斗人员也在使这些斗争场景更加失控的方面发挥了重要的作用。因此游戏技术被用来模拟这些情境，以使士兵和技术人员实践他们的技能。<ref>{{cite journal |doi=10.1177/1046878107308092 |title=Integrating crowd-behavior modeling into military simulation using game technology |journal=Simulation & Gaming |volume=39 |pages=10–38 |year=2007 |last1=McKenzie |first1=F. D. |last2=Petty |first2=M. D. |last3=Kruszewski |first3=P. A. |last4=Gaskins |first4=R. C. |last5=Nguyen |first5=Q.-A. H. |last6=Seevinck |first6=J. |last7=Weisel |first7=E. W. }}</ref>

=== Sociology 社会学===

The behavior of a modeled crowd plays a prominent role in analytical matters. These dynamics rely on the physical behaviors of individual agents within a crowd rather than the visual reality of the model itself. The social behaviors of people within these constructs have been of interest for many years, and the sociological concepts which underpin these interactions are constantly studied. The simulation of crowds in different situations allows for sociological study of real life gatherings in a variety of arrangements and locations. The variations in human behavior in situations varying in stress-levels allows for the further development and creation of crowd control strategies which can be more specifically applied to situations rather than generalized.

The behavior of a modeled crowd plays a prominent role in analytical matters. These dynamics rely on the physical behaviors of individual agents within a crowd rather than the visual reality of the model itself. The social behaviors of people within these constructs have been of interest for many years, and the sociological concepts which underpin these interactions are constantly studied. The simulation of crowds in different situations allows for sociological study of real life gatherings in a variety of arrangements and locations. The variations in human behavior in situations varying in stress-levels allows for the further development and creation of crowd control strategies which can be more specifically applied to situations rather than generalized.

模型群体的行为在分析问题时有重要的作用。这些动画依赖于独立主体在群体中的物理行为，而不是模型本身的视觉现实。多年来，人们在这些结构中的社会行为一直是研究者感兴趣的问题，支撑这些互动的社会学概念也被持续地研究。不同情境下的人群模拟使现实生活中不同场景地点集会的社会学研究得以进行。人类在压力水平不同的情境下的行为差异可以用来进一步发展和创造人群控制策略，这种策略可以更具体而不是空泛地应用于所有情况。

== See also 参见==

* [[3D computer graphics]] 3D计算机图形学

* [[Artificial intelligence]] 人工智能

* [[Crowd analysis]] 人群分析

* [[Emergent behavior]] 涌现行为

* [[Multi-agent system]] 多主体系统

* [[Particle system]] 粒子系统

== Crowd simulation software 人群模拟软件==

* Alice Software by the [[Moving Picture Company]]

* [[Golaem Crowd]]

* [[Massive (software)]]

* [[Miarmy]]

* [[Quadstone Paramics]]

* [[VISSIM]]

== References 参考文献==

{{Reflist|30em}}

== External links 外部链接==





! ——维基百科不是公司或产品的外部链接目录——

* [https://web.archive.org/web/20130627102118/http://steersuite.cse.yorku.ca/ SteerSuite], An open-source framework for developing and evaluating crowd simulation algorithms

* {{cite journal |doi=10.1111/j.1467-8659.2004.00783.x |title=Scalable behaviors for crowd simulation |journal=Computer Graphics Forum |volume=23 |issue=3 |pages=519–28 |year=2004 |last1=Sung |first1=Mankyu |last2=Gleicher |first2=Michael |last3=Chenney |first3=Stephen |citeseerx=10.1.1.10.2516 }}

{{Animation}}

{{collective animal behaviour}}

[[Category:Crowds]]

Category:Crowds

类别: Crowds

[[Category:Computer animation]]

Category:Computer animation

类别: 电脑动画

[[Category:3D computer graphics]]

Category:3D computer graphics

类别: 三维计算机图形

[[Category:Social physics]]

Category:Social physics

类别: 社会物理学

<noinclude>

This page was moved from [[wikipedia:en:Crowd simulation]]. Its edit history can be viewed at [[人群模拟/edithistory]]</noinclude>

[[Category:待整理页面]]

== 编者推荐 ==
=== 集智课程推荐 ===
[https://campus.swarma.org/course/592 群体模拟与Netlogo] 在本节课程中我们将从理论回到现实中学习到实际的本领：关于Netlogo的操作。

[https://campus.swarma.org/course/1095 NetLogo多主体建模入门] 本课程通过数个案例教会大家如何去动手搭建一个多主体仿真模型，以及如何利用NetLogo去实现。从生命游戏到人工鸟群，从模拟经济系统到病毒沿网络的传播，通过循序渐进的案例，该课程带你逐步走入NetLogo多主体建模的神奇世界。

[https://campus.swarma.org/course/1112 复杂性思维2020] 本课程中，张江老师将用一套自己搭建的“复杂性阶梯”的框架串联起众多复杂性科学概念，包括混沌、秩序、自催化网络、涌现、混沌边缘、热力学第二定律、分形、网络、自指等等。

=== 书籍推荐 ===
[https://book.douban.com/subject/11549281/ 人群模拟 Crowd Simulation]本书由提出人群模拟概念的Daniel Thalmann 和 Soraia Raupp Musse 编著，包括人群建模和评价模型的方法。本书在2013年有最新版本(第二版)，尚无中文译本。

人群模拟

2020-12-14T03:53:12Z

WildBoar：

此词条暂由彩云小译翻译，未经人工整理和审校，带来阅读不便，请见谅。
已由WIldBoar审校
{{technical|date=October 2016}}

{{3D computer graphics}}

'''Crowd simulation''' is the process of simulating the movement (or '''{{vanchor|dynamics|CROWD_DYNAMICS}}''') of a large number of entities or characters.<ref>{{cite book |doi=10.1007/978-3-319-08234-9_69-1 |chapter=Crowd Simulation |title=Encyclopedia of Computer Graphics and Games |pages=1–8 |year=2016 |last1=Thalmann |first1=Daniel |isbn=978-3-319-08234-9 }}</ref> It is commonly used to create [[virtual scene]]s for visual media like films and [[video game]]s, and is also used in crisis training,<ref>http://cc.ist.psu.edu/BRIMS/archives/2007/papers/07-BRIMS-025.pdf Jérôme Comptdaer, Emmanuel Chiva, Stéphane Delorme, Henri Morlaye, Jérôme Volpoët, Multi-scale behavioral models for urban crisis training simulation.</ref> architecture and urban planning,<ref>{{cite journal |doi=10.1162/pres.16.3.318 |title=Design and Evaluation of a Real-World Virtual Environment for Architecture and Urban Planning |journal=Presence: Teleoperators and Virtual Environments |volume=16 |issue=3 |pages=318–32 |year=2007 |last1=Drettakis |first1=George |last2=Roussou |first2=Maria |last3=Reche |first3=Alex |last4=Tsingos |first4=Nicolas |url=https://hal.inria.fr/inria-00607261/file/DRRT07.pdf }}</ref> and evacuation simulation.<ref>{{cite journal |doi=10.1016/S0360-1323(98)00057-2 |title=A review of the methodologies used in the computer simulation of evacuation from the built environment |journal=Building and Environment |volume=34 |issue=6 |pages=741–9 |year=1999 |last1=Gwynne |first1=S. |last2=Galea |first2=E.R. |last3=Owen |first3=M. |last4=Lawrence |first4=P.J. |last5=Filippidis |first5=L. }}</ref>

Crowd simulation is the process of simulating the movement (or ) of a large number of entities or characters. It is commonly used to create virtual scenes for visual media like films and video games, and is also used in crisis training, architecture and urban planning, and evacuation simulation.

''' 人群模拟 Crowd simulation'''是对大量实体或人物的运动进行模拟的过程。<ref>{{cite book |doi=10.1007/978-3-319-08234-9_69-1 |chapter=Crowd Simulation |title=Encyclopedia of Computer Graphics and Games |pages=1–8 |year=2016 |last1=Thalmann |first1=Daniel |isbn=978-3-319-08234-9 }}</ref>它常用于电影和视频游戏等视觉媒体中创建虚拟场景，也用于危机培训、<ref>http://cc.ist.psu.edu/BRIMS/archives/2007/papers/07-BRIMS-025.pdf Jérôme Comptdaer, Emmanuel Chiva, Stéphane Delorme, Henri Morlaye, Jérôme Volpoët, Multi-scale behavioral models for urban crisis training simulation.</ref>建筑和城市规划<ref>{{cite journal |doi=10.1162/pres.16.3.318 |title=Design and Evaluation of a Real-World Virtual Environment for Architecture and Urban Planning |journal=Presence: Teleoperators and Virtual Environments |volume=16 |issue=3 |pages=318–32 |year=2007 |last1=Drettakis |first1=George |last2=Roussou |first2=Maria |last3=Reche |first3=Alex |last4=Tsingos |first4=Nicolas |url=https://hal.inria.fr/inria-00607261/file/DRRT07.pdf }}</ref> 以及''' 人群疏散模拟 Evacuation Simulations'''。<ref>{{cite journal |doi=10.1016/S0360-1323(98)00057-2 |title=A review of the methodologies used in the computer simulation of evacuation from the built environment |journal=Building and Environment |volume=34 |issue=6 |pages=741–9 |year=1999 |last1=Gwynne |first1=S. |last2=Galea |first2=E.R. |last3=Owen |first3=M. |last4=Lawrence |first4=P.J. |last5=Filippidis |first5=L. }}</ref>

Crowd simulation may focus on aspects that target different applications. For realistic and fast [[rendering (computer graphics)|rendering]] of a crowd for visual media or [[virtual cinematography]], reduction of the complexity of the [[3D scene]] and [[image-based rendering]] are used,<ref>{{cite journal |doi=10.1111/1467-8659.00633 |title=Visualizing Crowds in Real-Time |journal=Computer Graphics Forum |volume=21 |issue=4 |pages=753–65 |year=2002 |last1=Tecchia |first1=Franco |last2=Loscos |first2=Celine |last3=Chrysanthou |first3=Yiorgos }}</ref> while variations in appearance help present a realistic population.<ref name="Thalmann et al 2009">{{cite book |doi=10.1109/CW.2009.23 |chapter=Challenges in Crowd Simulation |title=2009 International Conference on CyberWorlds |pages=1–12 |year=2009 |last1=Thalmann |first1=Daniel |last2=Grillon |first2=Helena |last3=Maim |first3=Jonathan |last4=Yersin |first4=Barbara |isbn=978-1-4244-4864-7 |citeseerx=10.1.1.365.5045 }}</ref><ref name="Maim et al 2009">{{cite journal |doi=10.1109/MCG.2009.129 |pmid=24806782 |title=Unique Character Instances for Crowds |journal=IEEE Computer Graphics and Applications |volume=29 |issue=6 |pages=82–90 |year=2009 |last1=Maim |first1=J. |last2=Yersin |first2=B. |last3=Thalmann |first3=D. }}</ref>

Crowd simulation may focus on aspects that target different applications. For realistic and fast rendering of a crowd for visual media or virtual cinematography, reduction of the complexity of the 3D scene and image-based rendering are used, while variations in appearance help present a realistic population.

人群模拟专注的方面可以针对不同应用。为了对''' 视觉媒体 visual media'''或''' 虚拟摄影 virtual cinematography'''中的人群进行真实和快速渲染，可以减少 3D 场景的复杂性和基于图像的渲染，<ref>{{cite journal |doi=10.1111/1467-8659.00633 |title=Visualizing Crowds in Real-Time |journal=Computer Graphics Forum |volume=21 |issue=4 |pages=753–65 |year=2002 |last1=Tecchia |first1=Franco |last2=Loscos |first2=Celine |last3=Chrysanthou |first3=Yiorgos }}</ref> 而外观的变化有助于展现一个真实的人群。<ref name="Thalmann et al 2009">{{cite book |doi=10.1109/CW.2009.23 |chapter=Challenges in Crowd Simulation |title=2009 International Conference on CyberWorlds |pages=1–12 |year=2009 |last1=Thalmann |first1=Daniel |last2=Grillon |first2=Helena |last3=Maim |first3=Jonathan |last4=Yersin |first4=Barbara |isbn=978-1-4244-4864-7 |citeseerx=10.1.1.365.5045 }}</ref><ref name="Maim et al 2009">{{cite journal |doi=10.1109/MCG.2009.129 |pmid=24806782 |title=Unique Character Instances for Crowds |journal=IEEE Computer Graphics and Applications |volume=29 |issue=6 |pages=82–90 |year=2009 |last1=Maim |first1=J. |last2=Yersin |first2=B. |last3=Thalmann |first3=D. }}</ref>

In games and applications intended to replicate real-life [[human]] crowd movement, like in evacuation simulations, simulated agents may need to navigate towards a goal, avoid collisions, and exhibit other human-like behavior. Many crowd steering algorithms have been developed to lead simulated crowds to their goals realistically. Some more general systems are researched that can support different kinds of agents (like cars and pedestrians),<ref>{{cite journal |doi=10.1002/cav.1654 |title=Vehicle-pedestrian interaction for mixed traffic simulation |journal=Computer Animation and Virtual Worlds |volume=26 |issue=3–4 |pages=405–12 |year=2015 |last1=Chao |first1=Qianwen |last2=Deng |first2=Zhigang |last3=Jin |first3=Xiaogang }}</ref> different levels of abstraction(like individual and continuum),<ref>{{cite journal |doi=10.1145/2070781.2024169 |title=Interactive hybrid simulation of large-scale traffic |journal=ACM Transactions on Graphics |volume=30 |issue=6 |pages=1 |year=2011 |last1=Sewall |first1=Jason |last2=Wilkie |first2=David |last3=Lin |first3=Ming C. }}</ref> agents interacting with smart objects,<ref>{{cite book |doi=10.1007/978-3-7091-6375-7_6 |chapter=Modeling Objects for Interaction Tasks |title=Computer Animation and Simulation '98 |pages=73–86 |series=Eurographics |year=1999 |last1=Kallmann |first1=Marcelo |last2=Thalmann |first2=Daniel |isbn=978-3-211-83257-8 |citeseerx=10.1.1.550.2013 }}</ref> and more complex physical and social dynamics.<ref>http://dl.acm.org/citation.cfm?id=1272705 Pelechano, N. and Allbeck, J. M. and Badler, N. I. Controlling individual agents in high-density crowd simulation. In Proceedings of the 2007 ACM SIGGRAPH/Eurographics Symposium on Computer Animation. {{ISBN|978-1-59593-624-0}}</ref>

In games and applications intended to replicate real-life human crowd movement, like in evacuation simulations, simulated agents may need to navigate towards a goal, avoid collisions, and exhibit other human-like behavior. Many crowd steering algorithms have been developed to lead simulated crowds to their goals realistically. Some more general systems are researched that can support different kinds of agents (like cars and pedestrians), different levels of abstraction(like individual and continuum), agents interacting with smart objects, and more complex physical and social dynamics.

在模拟真实人群运动的游戏和应用程序，比如人群疏散模拟中，''' 模拟的主体 Simulated Agents'''可能需要到达某个目标，避免碰撞，并表现出其他类似人的行为。现在已经有很多种''' 人群引导算法 Crowd Steering Algorithms'''能实际地引导模拟人群到达他们的目标。一些更普通的系统被研发出来支持不同的主体类型(如汽车和行人)，<ref>{{cite journal |doi=10.1002/cav.1654 |title=Vehicle-pedestrian interaction for mixed traffic simulation |journal=Computer Animation and Virtual Worlds |volume=26 |issue=3–4 |pages=405–12 |year=2015 |last1=Chao |first1=Qianwen |last2=Deng |first2=Zhigang |last3=Jin |first3=Xiaogang }}</ref>不同的抽象层次(如个体和''' 连续体 Continuum''')，<ref>{{cite journal |doi=10.1145/2070781.2024169 |title=Interactive hybrid simulation of large-scale traffic |journal=ACM Transactions on Graphics |volume=30 |issue=6 |pages=1 |year=2011 |last1=Sewall |first1=Jason |last2=Wilkie |first2=David |last3=Lin |first3=Ming C. }}</ref>可以和智能对象交互的主体，<ref>{{cite book |doi=10.1007/978-3-7091-6375-7_6 |chapter=Modeling Objects for Interaction Tasks |title=Computer Animation and Simulation '98 |pages=73–86 |series=Eurographics |year=1999 |last1=Kallmann |first1=Marcelo |last2=Thalmann |first2=Daniel |isbn=978-3-211-83257-8 |citeseerx=10.1.1.550.2013 }}</ref>以及更复杂的物理和社会动态。<ref>http://dl.acm.org/citation.cfm?id=1272705 Pelechano, N. and Allbeck, J. M. and Badler, N. I. Controlling individual agents in high-density crowd simulation. In Proceedings of the 2007 ACM SIGGRAPH/Eurographics Symposium on Computer Animation. {{ISBN|978-1-59593-624-0}}</ref>

== History 历史==

There has always been a deep-seated interest in the understanding and gaining control of motional and behavior of crowds of people. Many major advancements have taken place since the beginnings of research within the realm of crowd simulation. Evidently many new findings are continually made and published following these which improve the scalability, flexibility, applicability, and realism of simulations:

There has always been a deep-seated interest in the understanding and gaining control of motional and behavior of crowds of people. Many major advancements have taken place since the beginnings of research within the realm of crowd simulation. Evidently many new findings are continually made and published following these which improve the scalability, flexibility, applicability, and realism of simulations:

理解和控制人群的运动和行为一直是人们的兴趣所在。人群模拟领域的研究开始以来，人们已经取得了许多重大进展。显然，许多新发现正不断地被提出、被发表。这些发现提高了仿真模拟的可扩展性、灵活性、适用性和真实性 :

In 1987, behavioral animation was introduced and developed by [[Craig Reynolds (computer graphics)|Craig Reynolds]].<ref>{{Cite book|last=Reynolds|first=Craig|year=1987|title=Flocks, herds, and schools: A distributed behavior model.|url=|journal=Proceedings of ACM SIGGRAPH 87|volume=July 1987|pages=25–34|doi=10.1145/37401.37406|citeseerx=10.1.1.103.7187|isbn=978-0897912273}}</ref> He had simulated flocks of birds alongside schools of fish for the purpose of studying group intuition and movement. All agents within these simulations were given direct access to the respective positions and velocities of their surrounding agents. The theorization and study set forth by Reynolds was improved and built upon in 1994 by [[Xiaoyuan Tu]], [[Demetri Terzopoulos]] and Radek Grzeszczuk.<ref>{{cite journal |doi=10.1162/artl.1994.1.4.327 |title=Artificial Fishes: Autonomous Locomotion, Perception, Behavior, and Learning in a Simulated Physical World |journal=Artificial Life |volume=1 |issue=4 |pages=327–51 |year=1994 |last1=Terzopoulos |first1=Demetri |last2=Tu |first2=Xiaoyuan |last3=Grzeszczuk |first3=Radek |citeseerx=10.1.1.33.8131 }}</ref> The realistic quality of simulation was engaged with as the individual agents were equipped with synthetic vision and a general view of the environment within which they resided, allowing for a perceptual awareness within their dynamic habitats.

In 1987, behavioral animation was introduced and developed by Craig Reynolds. He had simulated flocks of birds alongside schools of fish for the purpose of studying group intuition and movement. All agents within these simulations were given direct access to the respective positions and velocities of their surrounding agents. The theorization and study set forth by Reynolds was improved and built upon in 1994 by Xiaoyuan Tu, Demetri Terzopoulos and Radek Grzeszczuk. '''The realistic quality of simulation was engaged with as the individual agents were equipped with synthetic vision and a general view of the environment within which they resided, allowing for a perceptual awareness within their dynamic habitats.
'''

1987年，雷诺兹 Craig Reynolds引入并发展了''' 行为动画 behavioral animation'''。<ref>{{Cite book|last=Reynolds|first=Craig|year=1987|title=Flocks, herds, and schools: A distributed behavior model.|url=|journal=Proceedings of ACM SIGGRAPH 87|volume=July 1987|pages=25–34|doi=10.1145/37401.37406|citeseerx=10.1.1.103.7187|isbn=978-0897912273}}</ref>为了研究群体直觉和运动Group Movement'''，他模拟了一群鸟和一群鱼。在这些模拟中的所有主体都可以直接访问它们周围各个主体的位置和速度。雷诺兹建立的理论和研究是在Xiaoyuan Tu、特佐普洛斯 Demetri Terzopoulos和格兹兹丘克 Radek Grzeszczuk1994年的研究之上改进和发展的。.<ref>{{cite journal |doi=10.1162/artl.1994.1.4.327 |title=Artificial Fishes: Autonomous Locomotion, Perception, Behavior, and Learning in a Simulated Physical World |journal=Artificial Life |volume=1 |issue=4 |pages=327–51 |year=1994 |last1=Terzopoulos |first1=Demetri |last2=Tu |first2=Xiaoyuan |last3=Grzeszczuk |first3=Radek |citeseerx=10.1.1.33.8131 }}</ref> '''仿真模拟的真实性和每个主体都有合成视觉和对生存环境的总体观点有关。这一点允许每个主体在动态栖息地内具有知觉意识。'''

--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） The realistic quality of simulation... 这一句话分成两句看，并且加入了一些个人理解，不知含义是否正确

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）这句不太通

Initial research in the field of crowd simulation began in 1997 with [[Daniel Thalmann]]'s supervision of Soraia Raupp Musse's PhD thesis. These two present a new model of crowd behavior in order to create a simulation of generic populations.<ref>{{Cite book|url=https://books.google.com/?id=3Adh_2ZNGLAC&pg=PR8&dq=history+of+crowd+simulation#v=onepage&q=history%20of%20crowd%20simulation&f=false|title=Crowd Simulation|last=Thalmann|first=Daniel|last2=Musse|first2=Soraia Raupp|date=2012-10-04|publisher=Springer Science & Business Media|isbn=978-1-4471-4449-6|language=en}}</ref> Here a relation is drawn between the autonomous behavior of the individual within the crowd and the emergent behavior originating from this.<ref>{{cite book |doi=10.1007/978-3-7091-6874-5_3 |chapter=A Model of Human Crowd Behavior : Group Inter-Relationship and Collision Detection Analysis |title=Computer Animation and Simulation '97 |pages=39–51 |series=Eurographics |year=1997 |last1=Musse |first1=S. R. |last2=Thalmann |first2=D. |isbn=978-3-211-83048-2 |citeseerx=10.1.1.14.7049 }}</ref>

Initial research in the field of crowd simulation began in 1997 with Daniel Thalmann's supervision of Soraia Raupp Musse's PhD thesis. These two present a new model of crowd behavior in order to create a simulation of generic populations. Here a relation is drawn between the autonomous behavior of the individual within the crowd and the emergent behavior originating from this.

最初的人群模拟领域研究始于1997年丹尼尔·塔尔曼 Daniel Thalmann指导苏拉娅·劳普·米塞尔 Soraia Raupp Musse的博士论文。他们两人提出了一个新的人群行为模型，以创建一个一般人群的仿真模拟。<ref>{{Cite book|url=https://books.google.com/?id=3Adh_2ZNGLAC&pg=PR8&dq=history+of+crowd+simulation#v=onepage&q=history%20of%20crowd%20simulation&f=false|title=Crowd Simulation|last=Thalmann|first=Daniel|last2=Musse|first2=Soraia Raupp|date=2012-10-04|publisher=Springer Science & Business Media|isbn=978-1-4471-4449-6|language=en}}</ref> 在这个模型中，他们给出了群体中个体的自主行为和由此产生的行为之间的一种关系。<ref>{{cite book |doi=10.1007/978-3-7091-6874-5_3 |chapter=A Model of Human Crowd Behavior : Group Inter-Relationship and Collision Detection Analysis |title=Computer Animation and Simulation '97 |pages=39–51 |series=Eurographics |year=1997 |last1=Musse |first1=S. R. |last2=Thalmann |first2=D. |isbn=978-3-211-83048-2 |citeseerx=10.1.1.14.7049 }}</ref>

In 1999, individualistic navigation began its course within the realm of crowd simulation via continued research of Craig Reynolds.<ref>{{Cite web|url=http://www.red3d.com/cwr/papers/1999/gdc99steer.html|title=Steering Behaviors For Autonomous Characters|website=www.red3d.com|access-date=2016-12-17}}</ref> Steering behaviors are proven to play a large role in the process of automating agents within a simulation. Reynolds states the processes of low-level locomotion to be dependent and reliant on mid-level steering behaviors and higher-level goal states and path finding strategies. Building off of the advanced work of Reynolds, Musse and Thalmann began to study the modeling of [[real-time simulation|real time simulation]]s of these crowds, and their applications to human behavior. The control of human crowds was designated as a hierarchical organization with levels of autonomy amongst agents. This marks the beginnings of modeling individual behavior in its most elementary form on humanoid agents.<ref>{{cite journal |doi=10.1109/2945.928167 |title=Hierarchical model for real time simulation of virtual human crowds |journal=IEEE Transactions on Visualization and Computer Graphics |volume=7 |issue=2 |pages=152–64 |year=2001 |last1=Musse |first1=S.R. |last2=Thalmann |first2=D. |url=http://infoscience.epfl.ch/record/98931 |type=Submitted manuscript }}</ref>

In 1999, individualistic navigation began its course within the realm of crowd simulation via continued research of Craig Reynolds. Steering behaviors are proven to play a large role in the process of automating agents within a simulation. Reynolds states the processes of low-level locomotion to be dependent and reliant on mid-level steering behaviors and higher-level goal states and path finding strategies. Building off of the advanced work of Reynolds, Musse and Thalmann began to study the modeling of real time simulations of these crowds, and their applications to human behavior. The control of human crowds was designated as a hierarchical organization with levels of autonomy amongst agents. This marks the beginnings of modeling individual behavior in its most elementary form on humanoid agents.

1999年，通过雷诺兹的持续研究，''' 个人主义导航 individualistic navigation'''开始了它在人群模拟领域的进程。<ref>{{Cite web|url=http://www.red3d.com/cwr/papers/1999/gdc99steer.html|title=Steering Behaviors For Autonomous Characters|website=www.red3d.com|access-date=2016-12-17}}</ref>仿真中，''' 指导行为Steering Behaviors'''在自动化主体过程中起着重要的作用。雷诺兹指出，低水平运动的过程依赖中等水平的指导行为和高水平的目标状态以及''' 路径寻找策略 Path Finding Strategies'''。在雷诺兹工作的基础之上，米塞尔和塔尔曼开始研究人群的实时模拟模型，以及它们在人类行为中的应用。对人群的控制被指定为一个具有不同主体自治水平的等级组织。这标志着在类人主体上以最基本的形式建立个体行为模型的开始。<ref>{{cite journal |doi=10.1109/2945.928167 |title=Hierarchical model for real time simulation of virtual human crowds |journal=IEEE Transactions on Visualization and Computer Graphics |volume=7 |issue=2 |pages=152–64 |year=2001 |last1=Musse |first1=S.R. |last2=Thalmann |first2=D. |url=http://infoscience.epfl.ch/record/98931 |type=Submitted manuscript }}</ref>

Coinciding with publications regarding human behavior models and simulations of group behaviors, Matt Anderson, Eric McDaniel, and Stephen Chenney's proposal of constraints on behavior<ref>{{Cite article|author1=Matt Anderson|author2=Eric McDaniel|author3=Stephen Chenney|title=Constrained animation of flocks|publisher=SCA '03 Proceedings of the 2003 ACM SIGGRAPH/Eurographics symposium on Computer animation |pages= 286–297|date=July 26–27, 2003 |ISBN=1-58113-659-5 }}</ref> gained popularity. The positioning of constraints on group animations was presented to be able to be done at any time within the simulation. This process of applying constraints to the behavioral model is undergone in a two-fold manner, by first determining the initial set of goal trajectories coinciding with the constraints, and then applying behavioral rules to these paths to select those which do not violate them.

Coinciding with publications regarding human behavior models and simulations of group behaviors, Matt Anderson, Eric McDaniel, and Stephen Chenney's proposal of constraints on behavior gained popularity. The positioning of constraints on group animations was presented to be able to be done at any time within the simulation. This process of applying constraints to the behavioral model is undergone in a two-fold manner, by first determining the initial set of goal trajectories coinciding with the constraints, and then applying behavioral rules to these paths to select those which do not violate them.

和人类行为模型和群体行为模拟的论文发表恰巧同一时期，马特•安德森 Matt Anderson、埃里克•麦克丹尼尔 Eric McDaniel和史蒂芬·切尼Stephen Chenney关于行为约束的研究计划<ref>{{Cite article|author1=Matt Anderson|author2=Eric McDaniel|author3=Stephen Chenney|title=Constrained animation of flocks|publisher=SCA '03 Proceedings of the 2003 ACM SIGGRAPH/Eurographics symposium on Computer animation |pages= 286–297|date=July 26–27, 2003 |ISBN=1-58113-659-5 }}</ref>大受欢迎。他们展示了对''' 群体动画 Group Animations'''约束的定位能够在程序模拟中的任何时候完成。将约束应用到行为模型的过程分为两步: 首先，确定与约束条件一致的初始的''' 目标轨迹 goal trajectories'''集；然后，将行为规则应用到这些路径上，去选择那些不违反约束条件的路径。

Correlating and building off of the findings proposed in his work with Musse, Thalmann, working alongside Bratislava Ulicny and Pablo de Heras Ciechomski, proposed a new model which allowed for interactive authoring of agents at the level of an individual, a group of agents and the entirety of a crowd. A brush metaphor is introduced to distribute, model and control crowd members in real-time with immediate feedback.<ref>{{cite book |doi=10.1145/1028523.1028555 |chapter=Crowdbrush |title=Proceedings of the 2004 ACM SIGGRAPH/Eurographics symposium on Computer animation – SCA '04 |pages=243–52 |year=2004 |last1=Ulicny |first1=Branislav |last2=Ciechomski |first2=Pablo de Heras |last3=Thalmann |first3=Daniel |isbn=978-3-905673-14-2 }}</ref>

Correlating and building off of the findings proposed in his work with Musse, Thalmann, working alongside Bratislava Ulicny and Pablo de Heras Ciechomski, proposed a new model which allowed for interactive authoring of agents at the level of an individual, a group of agents and the entirety of a crowd. A brush metaphor is introduced to distribute, model and control crowd members in real-time with immediate feedback.

塔尔曼基于他和米塞尔合作中提出的研究成果，和布拉迪斯拉发·乌利奇尼 Bratislava Ulicny以及巴勃罗·德·赫拉斯·切科姆斯基 Pablo de Heras Ciechomski提出了一种新的模型。这种模型允许在个人、一个群组和整个群体的层面上进行主体的''' 交互式创作 Interactive Authoring'''。他们引入了一个刷子隐喻，在即时反馈的情况下来进行实时分配、建模和控制人群成员。.<ref>{{cite book |doi=10.1145/1028523.1028555 |chapter=Crowdbrush |title=Proceedings of the 2004 ACM SIGGRAPH/Eurographics symposium on Computer animation – SCA '04 |pages=243–52 |year=2004 |last1=Ulicny |first1=Branislav |last2=Ciechomski |first2=Pablo de Heras |last3=Thalmann |first3=Daniel |isbn=978-3-905673-14-2 }}</ref>

== Crowd dynamics 人群动态==

One of the major goals in crowd simulation is to steer crowds realistically and recreate human dynamic behaviors.

One of the major goals in crowd simulation is to steer crowds realistically and recreate human dynamic behaviors.

人群模拟的主要目标之一是真实地引导人群并重现人类的动态行为。

There exists several overarching approaches to crowd simulation and AI, each one providing advantages and disadvantages based on crowd size and time scale. Time scale refers to how the objective of the simulation also affects the length of the simulation. For example, researching social questions such as how ideologies are spread amongst a population will result in a much longer running simulation since such an event can span up to months or years. Using those two characteristics, researchers have attempted to apply classifications to better evaluate and organize existing crowd simulators.<ref>{{cite journal |doi=10.1145/1842722.1842725 |title=Crowd modeling and simulation technologies |journal=ACM Transactions on Modeling and Computer Simulation |volume=20 |issue=4 |pages=1–35 |year=2010 |last1=Zhou |first1=Suiping |last2=Chen |first2=Dan |last3=Cai |first3=Wentong |last4=Luo |first4=Linbo |last5=Low |first5=Malcolm Yoke Hean |last6=Tian |first6=Feng |last7=Tay |first7=Victor Su-Han |last8=Ong |first8=Darren Wee Sze |last9=Hamilton |first9=Benjamin D. |hdl=10149/118022 |url=https://research.tees.ac.uk/ws/files/6477586/Accepted_manuscript.pdf }}</ref>

There exists several overarching approaches to crowd simulation and AI, each one providing advantages and disadvantages based on crowd size and time scale. Time scale refers to how the objective of the simulation also affects the length of the simulation. For example, researching social questions such as how ideologies are spread amongst a population will result in a much longer running simulation since such an event can span up to months or years. Using those two characteristics, researchers have attempted to apply classifications to better evaluate and organize existing crowd simulators.

人群模拟和人工智能有几种主要的方法，每种方法根据人群规模和时间尺度具有不同的优缺点。时间尺度是指仿真的目标如何也会影响仿真的时间长度。例如，研究诸如意识形态在人群中的分布等社会问题将导致模拟运行的时间更长，因为意识形态分布这样的事件可能长达数月或数年。利用这两个特点，研究人员已经试图分类现有的人群模拟器，以更好地评估和组织它们。<ref>{{cite journal |doi=10.1145/1842722.1842725 |title=Crowd modeling and simulation technologies |journal=ACM Transactions on Modeling and Computer Simulation |volume=20 |issue=4 |pages=1–35 |year=2010 |last1=Zhou |first1=Suiping |last2=Chen |first2=Dan |last3=Cai |first3=Wentong |last4=Luo |first4=Linbo |last5=Low |first5=Malcolm Yoke Hean |last6=Tian |first6=Feng |last7=Tay |first7=Victor Su-Han |last8=Ong |first8=Darren Wee Sze |last9=Hamilton |first9=Benjamin D. |hdl=10149/118022 |url=https://research.tees.ac.uk/ws/files/6477586/Accepted_manuscript.pdf }}</ref>

;Flow-based Approach: Flow based crowd simulations focus on the crowd as a whole rather than its components. As such individuals do not have any distinctive behaviors that occur due to input from their surroundings and behavioral factors are largely reduced.<ref name="Degond">{{cite journal|title= Congestion in a macroscopic model of self-driven particles modeling gregariousness| last1=Degond| first1=Pierre| last2=Navoret| first2=Laurent| last3=Bon| first3=Richard| last4=Sanchez| first4=David| journal=[[Journal of Statistical Physics]]| volume=138| issue=1–3| year=2010| pages=85–125| publisher=[[Springer Publishing|Springer]]| doi=10.1007/s10955-009-9879-x| arxiv=0908.1817| bibcode=2010JSP...138...85D}}</ref> This model is mainly used to estimate the flow of movement of a large and dense crowd in a given environment. Best used in studying large crowd, short time objectives.

Flow-based Approach: Flow based crowd simulations focus on the crowd as a whole rather than its components. As such individuals do not have any distinctive behaviors that occur due to input from their surroundings and behavioral factors are largely reduced. This model is mainly used to estimate the flow of movement of a large and dense crowd in a given environment. Best used in studying large crowd, short time objectives.

''' 基于流的方法 Flow-based Approach''': 基于流的人群模拟关注于人群作为一个整体，而不是人群的各种组成部分。这样人群中的个体没有任何独特的行为是由于他们周围的环境引起的，行为因素在很大程度上被减少了。<ref name="Degond">{{cite journal|title= Congestion in a macroscopic model of self-driven particles modeling gregariousness| last1=Degond| first1=Pierre| last2=Navoret| first2=Laurent| last3=Bon| first3=Richard| last4=Sanchez| first4=David| journal=[[Journal of Statistical Physics]]| volume=138| issue=1–3| year=2010| pages=85–125| publisher=[[Springer Publishing|Springer]]| doi=10.1007/s10955-009-9879-x| arxiv=0908.1817| bibcode=2010JSP...138...85D}}</ref>该模型主要用于估计给定环境下大型密集人群的'''运动流 the flow of movement'''。最适用于研究人群大、时间短的目标。

;Entity-based Approach: Models that implement a set of physical, predefined, and global laws meant to simulate social/psychological factors that occur in individuals that are a part of a crowd fall under this category. Entities in this case do not have the capacity to, in a sense, think for themselves. All movements are determined by the global laws being enforced on them. Simulations that use this model often do so to research crowd dynamics such as jamming and flocking. Small to medium-sized crowds with short term objectives fit this approach best.

Entity-based Approach: Models that implement a set of physical, predefined, and global laws meant to simulate social/psychological factors that occur in individuals that are a part of a crowd fall under this category. Entities in this case do not have the capacity to, in a sense, think for themselves. All movements are determined by the global laws being enforced on them. Simulations that use this model often do so to research crowd dynamics such as jamming and flocking. Small to medium-sized crowds with short term objectives fit this approach best.

''' 基于实体的方法 Entity-based Approach''': 属于这种类别方法的模型会实施一系列物理的、预先确定的整体规则，这些规则旨在模拟发生在属于群体的个人身上的社会/心理因素。在这类模型中，实体在某种意义上没有自己思考的能力。他们所有运动都是由整体规则决定的。这个模型的仿真模拟经常用来研究人群动态，例如拥挤jamming和聚集。中小型群体和较短时间的目标适合使用这种方法。

;Agent-based Approach: Characterized by autonomous, interacting individuals. Each agent of a crowd in this approach, is given a degree of intelligence; they can react to each situation on their own based on a set of decision rules. Information used to decide on an action is obtained locally from the agent's' surroundings. Most often, this approach is used for simulating realistic crowd behavior as the researcher is given complete freedom to implement any behaviors.

Agent-based Approach: Characterized by autonomous, interacting individuals. Each agent of a crowd in this approach, is given a degree of intelligence; they can react to each situation on their own based on a set of decision rules. Information used to decide on an action is obtained locally from the agent's' surroundings. Most often, this approach is used for simulating realistic crowd behavior as the researcher is given complete freedom to implement any behaviors.

''' 基于主体的方法 Agent-based Approach''': 该方法的特点是拥有自治的、互动的个体。在这种方法中，人群中的每个主体都被赋予了一定程度的智能; 他们可以根据一组决策规则自行对每个情况做出反应。主体用来决定一个行动的信息是从其周围获得的局部信息。这种方法最常见是被用来模拟现实的人群行为，因为研究人员可以完全自由地执行任何行为。

== Particle systems 粒子系统==

One way to simulate virtual crowds is to use a [[particle system]]. Particle systems were first introduced in computer graphics by W. T. Reeves in 1983.<ref>{{cite journal |doi=10.1117/12.261175 |title=From crowd simulation to airbag deployment: Particle systems, a new paradigm of simulation |journal=Journal of Electronic Imaging |volume=6 |pages=94–107 |year=1997 |last1=Cohen |first1=Eyal |last2=Cohen |first2=Eyal |last3=Najman |first3=Laurent |bibcode=1997JEI.....6...94B }}</ref> A particle system is a collection of a number of individual elements or ''particles''. Each particle is able to act autonomously and is assigned a set of physical attributes (such as color, size and velocity).

One way to simulate virtual crowds is to use a particle system. Particle systems were first introduced in computer graphics by W. T. Reeves in 1983. A particle system is a collection of a number of individual elements or particles. Each particle is able to act autonomously and is assigned a set of physical attributes (such as color, size and velocity).

一种模拟虚拟人群的方法是使用'''粒子系统 Particle System'''。1983年，W·T·里夫斯 W. T. Reeves 在'''计算机图形学 Computer Graphics'''中首次引入了粒子系统。<ref>{{cite journal |doi=10.1117/12.261175 |title=From crowd simulation to airbag deployment: Particle systems, a new paradigm of simulation |journal=Journal of Electronic Imaging |volume=6 |pages=94–107 |year=1997 |last1=Cohen |first1=Eyal |last2=Cohen |first2=Eyal |last3=Najman |first3=Laurent |bibcode=1997JEI.....6...94B }}</ref>粒子系统是很多单个元素或粒子的集合。每个粒子都能够自主行动，并被赋予一组物理属性(如颜色、大小和速度)。

A particle system is dynamic, in that the movements of the particles change over time. A particle system's movement is what makes it so desirable and easy to implement. Calculating the movements of these particles takes very little time. It simply involves physics: the sum of all the forces acting on a particle determines its motion. Forces such as gravity, friction and force from a collision, and social forces like the attractive force of a goal.

A particle system is dynamic, in that the movements of the particles change over time. A particle system's movement is what makes it so desirable and easy to implement. Calculating the movements of these particles takes very little time. It simply involves physics: the sum of all the forces acting on a particle determines its motion. Forces such as gravity, friction and force from a collision, and social forces like the attractive force of a goal.

粒子系统是动态的，因为粒子的运动随着时间而改变。粒子系统的运动使这种方法很理想，且易于实现。计算这些粒子的运动只需要很少的时间。它仅仅涉及到物理学: 作用在一个粒子上的所有力的总和决定了它的运动。力包括了诸如重力、摩擦力、碰撞产生的力，以及诸如目标的吸引力之类的社会力。

Usually each particle has a [[velocity vector]] and a [[position vector]], containing information about the particle's current velocity and position respectively. The particles next position is calculated by adding its velocity vector to its position vector. A very simple operation (again why particle systems are so desirable). Its velocity vector changes over time, in response to the forces acting on the particle. For example, a collision with another particle will cause it to change direction.

Usually each particle has a velocity vector and a position vector, containing information about the particle's current velocity and position respectively. The particles next position is calculated by adding its velocity vector to its position vector. A very simple operation (again why particle systems are so desirable). Its velocity vector changes over time, in response to the forces acting on the particle. For example, a collision with another particle will cause it to change direction.

通常每个粒子都有一个速度矢量和一个位置矢量，分别包含粒子当前的速度和位置信息。将粒子的速度矢量加到其位置矢量上，从而计算粒子的下一个位置。这是一个非常简单的操作(并再次说明了为什么粒子系统如此理想)。速度矢量在作用力影响下随时间变化。例如，与另一个粒子的碰撞将导致一个粒子改变方向。

Particles systems have been widely used in films for effects such as explosions, for water effects in the 2000 movie ''[[The Perfect Storm (film)|The Perfect Storm]]'', and simulated gas in the 1994 film ''[[The Mask (1994 film)|the Mask]]''.

Particles systems have been widely used in films for effects such as explosions, for water effects in the 2000 movie The Perfect Storm, and simulated gas in the 1994 film the Mask.

粒子系统已经广泛应用于电影，如制作爆炸特效。具体的例子包括2000年的电影《完美风暴 The Perfect Storm》的水特效，以及1994年的电影《面具 Mask》的模拟气体特效等。

Particles systems, however, do have some drawbacks. It can be a bad idea to use a particle system to simulate agents in a crowd that the director will move on command, as determining which particles belong to the agent and which do not is very difficult.

Particles systems, however, do have some drawbacks. It can be a bad idea to use a particle system to simulate agents in a crowd that the director will move on command, as determining which particles belong to the agent and which do not is very difficult.

然而，粒子系统确实有一些缺点。使用粒子系统模拟那些领导会根据指令行动行动的人群中的主体，可能是个坏主意，因为确定哪些粒子属于主体，哪些不属于主体是非常困难的。
--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） crowd that the director will move on command 不确定是否是“根据领导的指令统一行动的人群”这个意思

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]） crowd that the director will move on command 领导会根据指令行动的人群

=== Algorithm by Patil and Van Den Berg, 帕蒂尔 Patil和范登博格 Van Den Berg的算法===

This algorithm was designed for relatively simplistic crowds, where each agent in the crowd only desires to get to its own goal destination while also avoiding obstacles.<ref>{{cite journal |doi=10.1109/TVCG.2010.33 |pmid=21149879 |title=Directing Crowd Simulations Using Navigation Fields |journal=IEEE Transactions on Visualization and Computer Graphics |volume=17 |issue=2 |pages=244–54 |year=2011 |last1=Patil |first1=Sachin |last2=Van Den Berg |first2=Jur |last3=Curtis |first3=Sean |last4=Lin |first4=Ming C |last5=Manocha |first5=Dinesh |citeseerx=10.1.1.183.7823 }}</ref> This algorithm could be used for simulating a crowd in Times Square.

This algorithm was designed for relatively simplistic crowds, where each agent in the crowd only desires to get to its own goal destination while also avoiding obstacles. This algorithm could be used for simulating a crowd in Times Square.

帕蒂尔 Patil和范登博格 Van Den Berg的算法是针对相对简单的群体设计的，群体中的每个主体只希望到达自己的目的地，同时避开障碍物。<ref>{{cite journal |doi=10.1109/TVCG.2010.33 |pmid=21149879 |title=Directing Crowd Simulations Using Navigation Fields |journal=IEEE Transactions on Visualization and Computer Graphics |volume=17 |issue=2 |pages=244–54 |year=2011 |last1=Patil |first1=Sachin |last2=Van Den Berg |first2=Jur |last3=Curtis |first3=Sean |last4=Lin |first4=Ming C |last5=Manocha |first5=Dinesh |citeseerx=10.1.1.183.7823 }}</ref> 这个算法可以用来模拟'''时代广场 Times Square'''的人群。

Patils algorithm's most important and distinctive feature is that it utilizes the concept of ''navigation fields'' for directing agents. This is different from a guidance field; a guidance field is an area around the agent in which the agent is capable of "seeing"/detecting information. Guidance fields are typically used for avoiding obstacles, dynamic obstacles (obstacles that move) in particular. Every agent possesses its own guidance field. A navigation field, on the other hand, is a vector field which calculates the minimum cost path for every agent so that every agent arrives at its own goal position.

Patils algorithm's most important and distinctive feature is that it utilizes the concept of navigation fields for directing agents. This is different from a guidance field; a guidance field is an area around the agent in which the agent is capable of "seeing"/detecting information. Guidance fields are typically used for avoiding obstacles, dynamic obstacles (obstacles that move) in particular. Every agent possesses its own guidance field. A navigation field, on the other hand, is a vector field which calculates the minimum cost path for every agent so that every agent arrives at its own goal position.

帕蒂尔算法最重要且具有区分性的特征是它利用了''' 导航场 Navigation Fields'''的概念来指导主体。这不同于''' 指导场 Guidance Field'''; 指导场是主体周围的一个区域，主体可以在其中“看到”或检测到信息。指导场通常用于避开障碍物，特别是动态障碍物（移动的障碍物）。每个主体都有自己的指导场。另一方面，导航场是一个''' 向量场 vector field'''，它为每个主体计算''' 最小代价路径 minimum cost path'''，使每个主体到达自己的目标位置。

The navigation field can only be used properly when a path exists from every free (non-obstacle) position in the environment to one of the goal positions. The navigation field is computed using coordinates of the static objects in the environment, goal positions for each agent, and the guidance field for each agent. In order to guarantee that every agent reaches its own goal the navigation field must be free of local minima, except for the presence of sinks at the specified goals.

The navigation field can only be used properly when a path exists from every free (non-obstacle) position in the environment to one of the goal positions. The navigation field is computed using coordinates of the static objects in the environment, goal positions for each agent, and the guidance field for each agent. In order to guarantee that every agent reaches its own goal the navigation field must be free of local minima, except for the presence of sinks at the specified goals.

只有当从环境中的每一个''' 自由（无障碍）位置 free (non-obstacle) position'''到某一目标位置的路径存在时，导航场才能被正确使用。导航场是使用环境中静态对象的坐标、每个主体的目标位置和指导场计算的。为了保证每个主体达到自己的目标，导航场必须不受''' 局部极小值 local minima'''的限制，除非在特定目标处存在''' 汇 sinks'''。

The running time of computing the navigation field is <math>O(m*n*log(mn))</math>, where m × n is the grid dimension (similar to [[Dijkstra's algorithm]]). Thus, the algorithm is only dependent on the grid resolution and not dependent on the number of agents in the environment. However, this algorithm has a high memory cost.

The running time of computing the navigation field is <math>O(m*n*log(mn))</math>, where m × n is the grid dimension (similar to Dijkstra's algorithm). Thus, the algorithm is only dependent on the grid resolution and not dependent on the number of agents in the environment. However, this algorithm has a high memory cost.

计算导航场的运行时间的公式是
<math>O(m*n*log(mn))</math>，
其中 m × n 是网格维数(类似于迪杰斯特拉算法)。因此，该算法仅依赖于网格分辨率，而不依赖于环境中的主体数量。但是，这种算法的内存消耗很大。

=== Individual behavior modelling 个体行为建模===

One set of techniques for AI-based crowd simulation is to model crowd behavior by advanced simulation of individual agent motivations and decision-making. Generally, this means each agent is assigned some set of variables that measure various traits or statuses such as stress, personality, or different goals. This results in more realistic crowd behavior though may be more computationally intensive than simpler techniques.

One set of techniques for AI-based crowd simulation is to model crowd behavior by advanced simulation of individual agent motivations and decision-making. Generally, this means each agent is assigned some set of variables that measure various traits or statuses such as stress, personality, or different goals. This results in more realistic crowd behavior though may be more computationally intensive than simpler techniques.

基于AI的群体建模的技术之一，是通过对个体动机和决策的高级模拟来建立群体行为模型。一般来说，这意味着每个主体都被分配了一组变量来衡量不同的特征或状态，比如压力、人格或不同的目标。这导致更真实的群体行为，虽然可能比使用简单的技术计算量更大。

==== Personality-based models 基于人格的模型====

One method of creating individualistic behavior for crowd agents is through the use of personality traits.<ref>{{cite book |doi=10.1145/2019406.2019413 |chapter=Simulating heterogeneous crowd behaviors using personality trait theory |title=Proceedings of the 2011 ACM SIGGRAPH/Eurographics Symposium on Computer Animation – SCA '11 |pages=43–52 |year=2011 |last1=Guy |first1=Stephen J. |last2=Kim |first2=Sujeong |last3=Lin |first3=Ming C. |last4=Manocha |first4=Dinesh |isbn=978-1-4503-0923-3 }}</ref> Each agent may have certain aspects of their personality tuned based on a formula that associates aspects such as aggressiveness or impulsiveness with variables that govern the agents' behavior. One way this association can be found is through a subjective study in which agents are randomly assigned values for these variables and participants are asked to describe each agent in terms of these personality traits. A regression may then be done to determine a correlation between these traits and the agent variables. The personality traits can then be tuned and have an appropriate effect on agent behavior.

One method of creating individualistic behavior for crowd agents is through the use of personality traits. Each agent may have certain aspects of their personality tuned based on a formula that associates aspects such as aggressiveness or impulsiveness with variables that govern the agents' behavior. One way this association can be found is through a subjective study in which agents are randomly assigned values for these variables and participants are asked to describe each agent in terms of these personality traits. A regression may then be done to determine a correlation between these traits and the agent variables. The personality traits can then be tuned and have an appropriate effect on agent behavior.

为人群的主体创建个体行为模型的一种方法是使用人格特质。<ref>{{cite book |doi=10.1145/2019406.2019413 |chapter=Simulating heterogeneous crowd behaviors using personality trait theory |title=Proceedings of the 2011 ACM SIGGRAPH/Eurographics Symposium on Computer Animation – SCA '11 |pages=43–52 |year=2011 |last1=Guy |first1=Stephen J. |last2=Kim |first2=Sujeong |last3=Lin |first3=Ming C. |last4=Manocha |first4=Dinesh |isbn=978-1-4503-0923-3 }}</ref> 每个主体可能会根据一个公式调整他们个性的某些方面，这个公式将侵略性或冲动性等方面与控制主体行为的变量联系起来。发现这种联系的一个方法是通过一个主观的研究，在这个研究中主体被随机分配这些变量的值，参与者被要求用这些人格特征来描述每个主体。然后可以进行回归，以确定这些特征和主体变量之间的相关性。人格特征可以被调整，并对主体行为产生适当的影响。

The [[Big Five personality traits|OCEAN personality model]] has been used to define a mapping between personality traits and crowd simulation parameters. Automating crowd parameter tuning with personality traits provides easy authoring of scenarios with heterogeneous crowds.<ref>{{cite journal|last1=Durupinar|first1=Funda|last2=Pelechano|first2=Nuria|last3=Allbeck|first3=Jan|last4=Gudukbay|first4=Ugur|last5=Badler|first5=Norman I.|title=How the Ocean Personality Model Affects the Perception of Crowds|journal=IEEE Computer Graphics and Applications|date=2011|volume=31|issue=3|pages=22–31|doi=10.1109/MCG.2009.105|pmid=24808089|hdl=11693/11800|hdl-access=free}}</ref>

The OCEAN personality model has been used to define a mapping between personality traits and crowd simulation parameters. Automating crowd parameter tuning with personality traits provides easy authoring of scenarios with heterogeneous crowds.

''' 五大人格特征模型 Big Five personality traits/OCEAN personality model'''定义了人格特质与人群模拟参数之间的映射关系。自动调整人群的人格特征参数使得能够在错杂的人群中简便地创作场景。<ref>{{cite journal|last1=Durupinar|first1=Funda|last2=Pelechano|first2=Nuria|last3=Allbeck|first3=Jan|last4=Gudukbay|first4=Ugur|last5=Badler|first5=Norman I.|title=How the Ocean Personality Model Affects the Perception of Crowds|journal=IEEE Computer Graphics and Applications|date=2011|volume=31|issue=3|pages=22–31|doi=10.1109/MCG.2009.105|pmid=24808089|hdl=11693/11800|hdl-access=free}}</ref>

==== Stress-based model 基于压力的模型====

The behavior of crowds in high-stress situations can be modeled using [[General adaptation syndrome|General Adaptation Syndrome]] theory.<ref>{{cite book |doi=10.1145/2159616.2159626 |chapter=Interactive simulation of dynamic crowd behaviors using general adaptation syndrome theory |title=Proceedings of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games – I3D '12 |pages=55–62 |year=2012 |last1=Kim |first1=Sujeong |last2=Guy |first2=Stephen J. |last3=Manocha |first3=Dinesh |last4=Lin |first4=Ming C. |isbn=978-1-4503-1194-6 |citeseerx=10.1.1.673.3693 }}</ref> Agent behavior is affected by various stressors from their environment categorized into four prototypes: time pressure, area pressure, positional stressors, and interpersonal stressors, each with associated mathematical models.

The behavior of crowds in high-stress situations can be modeled using General Adaptation Syndrome theory.l Agent behavior is affected by various stressors from their environment categorized into four prototypes: time pressure, area pressure, positional stressors, and interpersonal stressors, each with associated mathematical models.

高压状态下的人群行为可以用''' 一般适应综合症理论 General Adaptation Syndrome theory'''来模拟。<ref>{{cite book |doi=10.1145/2159616.2159626 |chapter=Interactive simulation of dynamic crowd behaviors using general adaptation syndrome theory |title=Proceedings of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games – I3D '12 |pages=55–62 |year=2012 |last1=Kim |first1=Sujeong |last2=Guy |first2=Stephen J. |last3=Manocha |first3=Dinesh |last4=Lin |first4=Ming C. |isbn=978-1-4503-1194-6 |citeseerx=10.1.1.673.3693 }}</ref> 主体行为受到来自所处环境的各种压力源的影响，包括''' 时间压力 time pressure'''、''' 区域压力 area pressure'''、''' 位置压力 positional stressors'''和''' 人际压力 interpersonal stressors'''四个原型，每个原型都有相关的数学模型。

''Time pressure'' refers to stressors related to a time limit in reaching a particular goal. An example would be a street crossing with a timed walk signal or boarding a train before the doors are closed. This prototype is modeled by the following formula:

Time pressure refers to stressors related to a time limit in reaching a particular goal. An example would be a street crossing with a timed walk signal or boarding a train before the doors are closed. This prototype is modeled by the following formula:

时间压力是和达到特定目标的时间限制有关的压力源。例如，一个设有限时步行信号的十字路口，或在车门关闭前上车。这个原型是按照以下公式建模的:

<math>I_t = max(t_e - t_a, 0)</math>

where <math display="inline">I_t</math> is the intensity of the time pressure as a function of the estimated time to reach the goal <math display="inline">t_e</math> and a time constraint <math>t_a</math>.

where <math display="inline">I_t</math> is the intensity of the time pressure as a function of the estimated time to reach the goal <math display="inline">t_e</math> and a time constraint <math>t_a</math>.

其中 <math display="inline">I_t</math> 是时间压力强度，它是关于达到目标的估计时间<math display="inline">t_e</math>和时间限制 <math>t_a</math>的函数。

''Area pressure'' refers to stessors as a result of an environmental condition. Examples would be noise or heat in an area. The intensity of this stressor is constant over a particular area and is modeled by the following formula:

Area pressure refers to stessors as a result of an environmental condition. Examples would be noise or heat in an area. The intensity of this stressor is constant over a particular area and is modeled by the following formula:

区域压力是指由于环境条件而产生的压力。例如某个地区的噪音或热量。这种压力源的强度在某一特定地区是恒定的，其模型如下:

<math>I_a = \begin{cases} c & \text{if }p_a\in A \\ 0 & \text{if }p_a\not\in A \end{cases}</math>

where <math display="inline">I_a</math> is the intensity of the area pressure, <math display="inline">p_a</math> is the position of the agent in an area <math>A</math>, and <math>c</math> is a constant.

where <math display="inline">I_a</math> is the intensity of the area pressure, <math display="inline">p_a</math> is the position of the agent in an area <math>A</math>, and <math>c</math> is a constant.

其中<math display="inline">I_a</math>是区域压力强度，<math display="inline">p_a</math> 是主体在A区的位置，c是一个常数。

''Positional stressors'' refer to stressors associated with a local source of stress. The intensity of this stressor increases as an agent approaches the source of the stress. An example would be a fire or a dynamic object such as an assailant. It can be modeled by the following formula:

Positional stressors refer to stressors associated with a local source of stress. The intensity of this stressor increases as an agent approaches the source of the stress. An example would be a fire or a dynamic object such as an assailant. It can be modeled by the following formula:

位置压力是指与局部压力源相关的压力源。这种压力源的强度随着主体接近压力源而增加。一个例子就是火灾，或运动的物体比如攻击者。它可以用下面的公式来模拟:

<math>I_p = \lVert p_a - p_s \rVert</math>

where <math>I_p</math> is the intensity of the positional stressor, <math>p_a</math> is the position of the agent and <math>p_s</math> is the position of the stressor. Alternatively, stressors that generate high stress over a large area (such as a fire) can be modeled using a Gaussian distribution with standard deviation <math>\sigma</math>:

where <math>I_p</math> is the intensity of the positional stressor, <math>p_a</math> is the position of the agent and <math>p_s</math> is the position of the stressor. Alternatively, stressors that generate high stress over a large area (such as a fire) can be modeled using a Gaussian distribution with standard deviation <math>\sigma</math>:

其中 <math>I_p</math> 是位置压力源的强度，<math>p_a</math> 是主体的位置，<math>p_s</math> 是压力源的位置。另外，在一个大的区域产生高压力的压力源(如火灾)，可以用一个带有正态分布的标准差<math>\sigma</math>的模型来模拟:

<math>I_p = \mathcal{N}(p_a - p_s, \sigma)</math>

''Interpersonal stressors'' are stressors as a result of crowding by nearby agents. It can be modeled by the following formula:

Interpersonal stressors are stressors as a result of crowding by nearby agents. It can be modeled by the following formula:

人际压力源是由邻近主体的拥挤程度而产生的压力源。它可以用下面的公式来模拟:

<math>I_i = max(n_c - n_p, 0)</math>

where <math>I_i</math> is the intensity of the interpersonal stressor, <math>n_c</math> is the current number of neighbors within a unit space and <math>n_p</math> is the preferred number of neighbors within a unit space for that particular agent.

where <math>I_i</math> is the intensity of the interpersonal stressor, <math>n_c</math> is the current number of neighbors within a unit space and <math>n_p</math> is the preferred number of neighbors within a unit space for that particular agent.

其中<math>I_i</math>表示人际压力源的强度，<math>n_c</math> 表示当前单位空间内邻居的数量，<math>n_p</math> 表示单位空间内该特定主体理想的邻居数量。

The ''perceived stress'' follows [[Stevens' law|Steven's Law]] and is modeled by the formula:

The perceived stress follows Steven's Law and is modeled by the formula:

感知到的压力遵循'''史蒂芬定律 Steven's Law '''，并可以用下面的公式模拟:

<math>\psi(I) = kI^n</math>

where <math>\psi(I)</math> is the perceived stress for a stress level <math>I</math>, <math>k</math> is a scale factor, and <math>n</math> is an exponent depending on the stressor type.

where <math>\psi(I)</math> is the perceived stress for a stress level <math>I</math>, <math>k</math> is a scale factor, and <math>n</math> is an exponent depending on the stressor type.

其中<math>\psi(I)</math>是感知到的压力水平，<math>I</math>是客观的压力水平，<math>k</math> 是一个比例系数，<math>n</math>是一个取决于压力源类型的指数。

An agent's ''stress response'' can be found with the following formula:

An agent's stress response can be found with the following formula:

一个主体的压力反应可以通过以下公式得出:

<math>{dS \over dt} = \begin{cases} \alpha & \text{if } \psi > S \\ (-\alpha \leq {d\psi \over dt} \leq \alpha) & \text{if } \psi = S\\ -\alpha & \text{if } \psi < S\end{cases}</math>

where <math>S</math> is the stress response capped at a maximum value of <math>\beta</math> and <math>\alpha</math> is the maximum rate at which an agent's stress response can change.

where <math>S</math> is the stress response capped at a maximum value of <math>\beta</math> and <math>\alpha</math> is the maximum rate at which an agent's stress response can change.

其中，<math>S</math>是压力反应，它受到最大<math>\beta</math>值的限制，<math>\alpha</math>是主体的压力反应可以改变的最大速率。

Examples of notable crowd AI simulation can be seen in [[New Line Cinema]]'s ''[[The Lord of the Rings (film series)|The Lord of the Rings]]'' films, where AI armies of thousands of characters battle each other. This crowd simulation was done using [[Weta Digital]]'s [[Massive (software)|Massive software]].

Examples of notable crowd AI simulation can be seen in New Line Cinema's The Lord of the Rings films, where AI armies of thousands of characters battle each other. This crowd simulation was done using Weta Digital's Massive software.

值得注意的AI模拟例子可以在'''新线电影公司 New Line Cinema'''的《指环王 Lord of the Rings》系列电影中看到。在这部电影中，成千上万的AI角色互相争斗。这个人群模拟是用威塔数码公司 Weta Digital的Massive软件完成的。

=== Sociology 社会学===

''Crowd simulation'' can also refer to simulations based on [[group dynamics]] and [[crowd psychology]], often in public safety planning. In this case, the focus is just the behavior of the crowd, and not the visual realism of the simulation. Crowds have been studied as a scientific interest since the end of the 19th Century. A lot of research has focused on the collective social behavior of people at social gatherings, assemblies, protests, rebellions, concerts, sporting events and religious ceremonies. Gaining insight into natural human behavior under varying types of stressful situations will allow better models to be created which can be used to develop crowd controlling strategies.

Crowd simulation can also refer to simulations based on group dynamics and crowd psychology, often in public safety planning. In this case, the focus is just the behavior of the crowd, and not the visual realism of the simulation. Crowds have been studied as a scientific interest since the end of the 19th Century. A lot of research has focused on the collective social behavior of people at social gatherings, assemblies, protests, rebellions, concerts, sporting events and religious ceremonies. Gaining insight into natural human behavior under varying types of stressful situations will allow better models to be created which can be used to develop crowd controlling strategies.

人群模拟也可以指基于'''群体动力学 Group Dynamics'''和'''群体心理学 Crowd Psychology'''的模拟，通常用于'''公共安全规划 Public Safety Planning'''。在这种情况下，研究的焦点只是人群的行为，而不是模拟的视觉真实性。自19世纪末以来，人们一直将人群作为一种科学兴趣进行研究。许多研究都关注人们在社会聚会、集会、抗议、叛乱、音乐会、体育赛事和宗教仪式上的集体社会行为。了解不同类型压力情况下的人类自然行为将创建更好的、可用于发展人群控制策略的模型。

''Emergency response teams'' such as policemen, the National Guard, military and even volunteers must undergo some type of crowd control training. Using researched principles of human behavior in crowds can give disaster training designers more elements to incorporate to create realistic simulated disasters. Crowd behavior can be observed during panic and non-panic conditions. When natural and unnatural events toss social ideals into a twisting chaotic bind, such as the events of 9/11 and hurricane Katrina, humanity's social capabilities are truly put to the test. Military programs are looking more towards simulated training, involving emergency responses, due to their cost-effective technology as well as how effective the learning can be transferred to the real world.{{Citation needed|date=October 2012}} Many events that may start out controlled can have a twisting event that turns them into catastrophic situations, where decisions need to be made on the spot. It is these situations in which crowd dynamical understanding would play a vital role in reducing the potential for anarchy.

Emergency response teams such as policemen, the National Guard, military and even volunteers must undergo some type of crowd control training. Using researched principles of human behavior in crowds can give disaster training designers more elements to incorporate to create realistic simulated disasters. Crowd behavior can be observed during panic and non-panic conditions. When natural and unnatural events toss social ideals into a twisting chaotic bind, such as the events of 9/11 and hurricane Katrina, humanity's social capabilities are truly put to the test. Military programs are looking more towards simulated training, involving emergency responses, due to their cost-effective technology as well as how effective the learning can be transferred to the real world. Many events that may start out controlled can have a twisting event that turns them into catastrophic situations, where decisions need to be made on the spot. It is these situations in which crowd dynamical understanding would play a vital role in reducing the potential for anarchy.

警察、国民警卫队、军队甚至志愿者等紧急反应小组都必须接受某种形式的人群控制培训。运用研究出的群体中人类的行为原则，灾难训练设计者可以有更多元素来创造更逼真的模拟灾难。在恐慌和非恐慌情况下可以观察到群体行为。当自然和非自然的事件使社会理想状况陷入扭曲混乱的局面，比如“911”和飓风卡特里娜事件时，人类的社会能力就在真正地接受考验。军事项目更倾向于以模拟形式进行训练和应急反应，因为它们是成本低效益高的形式，并且能够有效地将所学转移到现实世界。许多事件一开始可能受到控制，但后来反转发展成为灾难性情况，因此需要当场做出决定。正是在这些情况下，对人群的动态理解将发挥重要作用，以减少出现混乱的可能性。

''Modeling'' techniques of crowds vary from holistic or network approaches to understanding individualistic or behavioral aspects of each agent. For example, the Social Force Model describes a need for individuals to find a balance between social interaction and physical interaction. An approach that incorporates both aspects, and is able to adapt depending on the situation, would better describe natural human behavior, always incorporating some measure of unpredictability. With the use of multi-agent models understanding these complex behaviors has become a much more comprehensible task. With the use of this type of software, systems can now be tested under extreme conditions, and simulate conditions over long periods of time in the matter of seconds.

Modeling techniques of crowds vary from holistic or network approaches to understanding individualistic or behavioral aspects of each agent. For example, the Social Force Model describes a need for individuals to find a balance between social interaction and physical interaction. An approach that incorporates both aspects, and is able to adapt depending on the situation, would better describe natural human behavior, always incorporating some measure of unpredictability. With the use of multi-agent models understanding these complex behaviors has become a much more comprehensible task. With the use of this type of software, systems can now be tested under extreme conditions, and simulate conditions over long periods of time in the matter of seconds.

群体的建模技术从整体或网络到理解每个主体的个人或行为方面都各不相同。例如，'''社会力模型 Social Force Model'''描述了个体在社会互动和物理互动之间寻求平衡的需求。一种结合了这两个方面，并且能够根据具体情境进行调整的方法，将更好地描述自然的人类行为，并总是包含一些对不可预测性的测量。随着多主体模型的使用，理解这些复杂的行为已经成为一个易懂的任务。利用这种类型的软件，现在研究人员可以在极端条件下测试系统，也可以在几秒钟内模拟长期的情况变化。

In some situations, the behavior of swarms of non-human animals can be used as an experimental model of crowd behavior. The panic behavior of ants when exposed to a [[Insect repellent|repellent]] chemical in a confined space with limited exit routes has been found to have both similarities and differences to equivalent human behavior.<ref>N. Shiwakoti et al., "Animal dynamics based approach for modeling pedestrian crowd egress under panic conditions", Transportation Research Part B 45 (2011) 1433-1449.</ref><ref>S. Wang et al., "Behavior of Ants Escaping from a Single-Exit Room", PLoS One. 2015; 10(6): e0131784.</ref>

In some situations, the behavior of swarms of non-human animals can be used as an experimental model of crowd behavior. The panic behavior of ants when exposed to a repellent chemical in a confined space with limited exit routes has been found to have both similarities and differences to equivalent human behavior.

在某些情况下，非人类动物群体的行为可以作为群体行为的一个实验模型。人们发现，蚂蚁在出口有限且封闭的空间里暴露于令人反感的化学物质中时产生的惊慌行为，与同样情况下的人类行为既有相似之处，也有不同之处。<ref>N. Shiwakoti et al., "Animal dynamics based approach for modeling pedestrian crowd egress under panic conditions", Transportation Research Part B 45 (2011) 1433-1449.</ref><ref>S. Wang et al., "Behavior of Ants Escaping from a Single-Exit Room", PLoS One. 2015; 10(6): e0131784.</ref>

=== Modeling individual behaviors 个体行为建模===

Helbing proposed a model based on physics using a particle system and socio-psychological forces in order to describe human crowd behavior in panic situation, this is now called the Helbing Model. His work is based on how the average person would react in a certain situation. Although this is a good model, there are always different types of people present in the crowd and they each have their own individual characteristics as well as how they act in a group structure. For instance, one person may not react to a panic situation, while another may stops walking and interfere in the crowd dynamics as a whole. Furthermore, depending on the group structure, the individual action can change because the agent is part of a group, for example, returning to a dangerous place in order to rescue a member of that group. Helbing's model can be generalized incorporating individualism, as proposed by Braun, Musse, Oliveira and Bodmann.<ref name=":0" />

Helbing proposed a model based on physics using a particle system and socio-psychological forces in order to describe human crowd behavior in panic situation, this is now called the Helbing Model. His work is based on how the average person would react in a certain situation. Although this is a good model, there are always different types of people present in the crowd and they each have their own individual characteristics as well as how they act in a group structure. For instance, one person may not react to a panic situation, while another may stops walking and interfere in the crowd dynamics as a whole. Furthermore, depending on the group structure, the individual action can change because the agent is part of a group, for example, returning to a dangerous place in order to rescue a member of that group. Helbing's model can be generalized incorporating individualism, as proposed by Braun, Musse, Oliveira and Bodmann.

赫尔本 Helbing 提出了一个基于物理学的模型，使用粒子系统和社会心理力量来描述人群在恐慌情况下的行为，这个模型现在被称为''' 赫尔本模型 Helbing Model'''。他的工作基于在特定情况下普通人如何反应。虽然这是一个很好的模式，但是在人群中总是有不同类型的人，他们每个人都有自己的个人特点和在群体结构中的行为方式。例如，一个人可能不会对恐慌的情况做出反应，而另一个人可能会停下脚步并干扰整个人群的运动。此外，根据群体结构的不同，作为群体的一部分主体的个人行为可能会发生变化。例如，为了拯救该群体的一个成员而返回到一个危险的地方。如布劳恩 Braun, Musse,奥利韦拉 Oliveira和布罗德曼 Bodmann 提出的那样，赫尔本的模型可以概括为融入个人主义。<ref name=":0" />

In order to tackle this problem, individuality should be assigned to each agent, allowing to deal with different types of behaviors. Another aspect to tackle this problem is the possibility to group people, forming these group causes people to change their behavior as a function of part of the group structure. Each agent (individual) can be defined according to the following parameters:

In order to tackle this problem, individuality should be assigned to each agent, allowing to deal with different types of behaviors. Another aspect to tackle this problem is the possibility to group people, forming these group causes people to change their behavior as a function of part of the group structure. Each agent (individual) can be defined according to the following parameters:

为了解决这个问题，应该给每个主体分配个性，从而允许模型处理不同类型的行为。解决这个问题的另一个方法是把人们分组，形成这样的群体会使人们作为群体结构的一部分而改变他们的行为。
--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]）我觉得原文Another aspect……到forming these group……再到 part of the group structure，应该是两句，是从forming处分开的两句话）

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）我觉得原文和翻译都没有问题

每个主体(个体)可以根据以下参数定义:

# Id – Agent identifier

Id – Agent identifier

Id：主体标识符

# IdFamily – Identifier of the family. A family is a predefined group formed by agents who know each other

IdFamily – Identifier of the family. A family is a predefined group formed by agents who know each other

IdFamily：家族标识符。家族是由相互认识的主体组成的一个预先设定的组。

# DE – Dependence level of the agent which mimics the need for help. Values [0,1]

DE – Dependence level of the agent which mimics the need for help. Values [0,1]

DE：主体的'''依赖水平 Dependence level'''，用来模拟主体对他人帮助的需求。取值范围：[0,1]

# AL – Altruism level representing the tendency to help other agents. Values [0,1]

AL – Altruism level representing the tendency to help other agents. Values [0,1]

AL：'''利他主义水平 Altruism Level'''，代表了帮助他人的倾向。取值范围：[0,1]

# vi – Speed of the agent

vi – Speed of the agent

vi ：主体的速度

To model the effect of the dependence parameter with ''individual agents'', the equation is defined as:

To model the effect of the dependence parameter with individual agents, the equation is defined as:

为了模拟单个主体的因变量参数的效应方程定义为:

: <math>v_i = (1-DE)v_{max}</math>

<math>v_i = (1-DE)v_{max}</math>

<math>v_i = (1-DE)v_{max}</math>

When evaluating the speed of the agent, it is clear that if the value of the dependence factor, DE, is equal to one, then the person would be fully disabled making him unable to move. If the dependence factor is equal to zero, then the person is able to run at his max speed.

When evaluating the speed of the agent, it is clear that if the value of the dependence factor, DE, is equal to one, then the person would be fully disabled making him unable to move. If the dependence factor is equal to zero, then the person is able to run at his max speed.

在评估主体的速度时，很明显，如果依赖因子 DE 的值等于1，则表示该主体完全丧失行动能力。如果依赖因子等于0，那么该主体能够以其最大速度运动。

Group formation is related to the Altruism force which is implemented as an interaction force between two or more agents who are part of the same family. Mathematically, it is described as the following:

Group formation is related to the Altruism force which is implemented as an interaction force between two or more agents who are part of the same family. Mathematically, it is described as the following:

群体的形成与利他主义力有关。利他主义力是同一家族中两个或两个以上成员之间的相互作用力。用数学方法，它被描述为:

: <math>F\overline{a}_i = K\sum \left ( AL_iDE_j \times \left | d_{ij}-d_{ip} \right | \times e_{ij} \right ) </math>

<math>F\overline{a}_i = K\sum \left ( AL_iDE_j \times \left | d_{ij}-d_{ip} \right | \times e_{ij} \right ) </math>

<math>F\overline{a}_i = K\sum \left ( AL_iDE_j \times \left | d_{ij}-d_{ip} \right | \times e_{ij} \right ) </math>

where:

where:

其中:

: {{math|''dij''}} represents the distance between two agents with the origin at the position of the agent;

: {{math|''dij''}} represents the distance between two agents with the origin at the position of the agent;

{{math|''dij''}}表示两个主体之间的距离，原点设在主体的位置;

: {{math|''dip''}} is the distance vector point from the agents to the door's position {{math|''p''}} of the simulation environment;

: {{math|''dip''}} is the distance vector point from the agents to the door's position of the simulation environment;

{{math|''dip''}}是模拟环境中从主体到门的位置的距离矢量点;

: {{math|''K''}} is a constant;

: {{math|''K''}} is a constant;

{{math|''K''}}是一个常数

: {{math|''eij''}} is the unitary vector with the origin at position i.

: {{math|''eij''}} is the unitary vector with the origin at position i.

{{math|''eij''}}是原点位于i处的酉向量。

Consequently, the greater the parameter {{math|''ALi''}} of agent {{math|''i''}}, the bigger will be {{math|''Fāi''}} which points to the agent {{math|''j''}} and has the high level of {{math|''DEj''}}. When both agents are close enough to each other, the one with high {{math|''DE''}} (agent {{math|''j''}} in this example) adopts the value of agent {{math|''i''}} (<math>DE_j = DE_i</math>). This means that the evacuation ability of agent {{math|''i''}} is shared with agent {{math|''j''}} and both start moving together.

Consequently, the greater the parameter of agent , the bigger will be which points to the agent and has the high level of . When both agents are close enough to each other, the one with high (agent in this example) adopts the value of agent (<math>DE_j = DE_i</math>). This means that the evacuation ability of agent is shared with agent and both start moving together.

因此，主体{{math|''i''}}的利他主义水平{{math|''ALi''}}越高，指向主体{{math|''j''}}的{{math|''Fāi''}}就越大，{{math|''j''}}也具有较高的依赖水平{{math|''DEj''}}。当两个代理彼此足够接近时，具有较高依赖水平的主体(本例中的主体{{math|''j''}})就采用主体{{math|''i''}}依赖水平(<math>DE_j = DE_i</math>)。这意味着主体{{math|''i''}}与主体{{math|''j''}}共享疏散能力，两者一起开始移动。

By using these applying these equations in model testing using a normally distributed population, the results are fairly similar to the Helbing Model.

'''By using these applying these equations in model testing using a normally distributed population, the results are fairly similar to the Helbing Model.
'''

'''通过将这些方程应用于模型试验并采取正态分布的总体，结果与赫尔本模型非常相似。'''
--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）这句前半句英文的结构我没太懂，中文的翻译也不知道是否准确

The places where this would be helpful would be in an evacuation scenario. Take for example, an evacuation of a building in the case of a fire. Taking into account the characteristics of individual agents and their group performances, determining the outcome of how the crowd would exit the building is critically important in creating the layout of the building.<ref name=":0">{{cite book |doi=10.1109/CASA.2003.1199317 |chapter=Modeling individual behaviors in crowd simulation |title=Proceedings 11th IEEE International Workshop on Program Comprehension |pages=143–8 |year=2003 |last1=Braun |first1=A. |last2=Musse |first2=S.R. |last3=De Oliveira |first3=L.P.L. |last4=Bodmann |first4=B.E.J. |isbn=978-0-7695-1934-0 }}</ref>

The places where this would be helpful would be in an evacuation scenario. Take for example, an evacuation of a building in the case of a fire. Taking into account the characteristics of individual agents and their group performances, determining the outcome of how the crowd would exit the building is critically important in creating the layout of the building.

这种模型会对疏散场景有所帮助。以发生火灾的建筑物疏散为例，考虑到个体的特点和他们在团队的表现从而确定人群会如何离开建筑的结果，对于设计建筑的布局至关重要。<ref name=":0">{{cite book |doi=10.1109/CASA.2003.1199317 |chapter=Modeling individual behaviors in crowd simulation |title=Proceedings 11th IEEE International Workshop on Program Comprehension |pages=143–8 |year=2003 |last1=Braun |first1=A. |last2=Musse |first2=S.R. |last3=De Oliveira |first3=L.P.L. |last4=Bodmann |first4=B.E.J. |isbn=978-0-7695-1934-0 }}</ref>

=== Leader behavior during evacuation simulations 疏散模拟中的领导者行为===

As described earlier, the '''Helbing Model''' is used as the basics for crowd behavior. This same type of behavior model is used for evacuation simulations.

As described earlier, the Helbing Model is used as the basics for crowd behavior. This same type of behavior model is used for evacuation simulations.

如前所述，赫尔本模型被用作群体行为的基础。同样类型的行为模型也同样被用于疏散模拟。

In general, the first thing that has to be assumed is that not everyone has knowledge about the environment or where there are and aren't hazards. From this assumption we can create three types of agents. The first type is a trained leader, this agent knows about the environment and is able to spread knowledge to other agents so they know how to exit from an environment. The next type of agent is an untrained leader, this agent does not know about the environment, however, as the agent explores the environment and gets information from other types of leaders, the agent is able to spread the knowledge about the environment. The last type of agent is a follower, this type of agent can only take information from other leaders and not be able to share the information with other agents.

In general, the first thing that has to be assumed is that not everyone has knowledge about the environment or where there are and aren't hazards. From this assumption we can create three types of agents. The first type is a trained leader, this agent knows about the environment and is able to spread knowledge to other agents so they know how to exit from an environment. The next type of agent is an untrained leader, this agent does not know about the environment, however, as the agent explores the environment and gets information from other types of leaders, the agent is able to spread the knowledge about the environment. The last type of agent is a follower, this type of agent can only take information from other leaders and not be able to share the information with other agents.

一般来说，首先需要假定的是，并不是每个人都了解环境或了解哪里有没有危险。根据这个假设，我们可以创建三种类型的主体。第一种类型是训练有素的领导者，这种主体了解环境并能够将知识传播给其他主体，因此他们知道如何从这种环境中退出。第二种类型的主体是未经训练的领导者。他们不了解环境，但是当这种主体探索环境并从其他类型的领导者那里获得信息时，他们能够传播有关环境的知识。最后一种类型是跟随者，这种类型的主体只能从其他领导者那里获取信息，不能与其他主体共享信息。

The implementation of these types of agents is fairly straightforward. The leaders in the environment have a map of the environment saved as one of their attributes. An untrained leader and followers will start out with an empty map as their attribute. Untrained leaders and followers will start exploring an environment by themselves and create a map of walkable and unwalkable locations. Leaders and untrained leaders (once they have the knowledge), will share information with other agents depending on their proximity. They will share information about which points on the grid are blocked, the local sub-graphs and the dangers in the area.

The implementation of these types of agents is fairly straightforward. The leaders in the environment have a map of the environment saved as one of their attributes. An untrained leader and followers will start out with an empty map as their attribute. Untrained leaders and followers will start exploring an environment by themselves and create a map of walkable and unwalkable locations. Leaders and untrained leaders (once they have the knowledge), will share information with other agents depending on their proximity. They will share information about which points on the grid are blocked, the local sub-graphs and the dangers in the area.

实现这些主体类型的方法相当简单直接。对于领导者，环境地图被保存为他们的属性之一。未经训练的领导者和追随者具有一张空地图的属性。未经训练的领导者和追随者将自己开始探索环境，并创建一个具有适合和不适合走地点信息的地图。领导者和未受过训练的领导者(一旦他们掌握了知识) ，会根据与其他主体的接近程度来分享信息。他们分享的信息包括网格上哪些点被阻塞，局部子地图和该地区的危险。

There were two types of searching algorithms tried out for this implementation. There was the random search and the depth first search. A random search is where each of the agents go in any direction through the environment and try to find a pathway out. The depth first search is where agents follow one path as far as it can go then return and try another path if the path they traversed does not contain an exit. If was found that depth first search gave a speed up of 15 times versus a random search.<ref>{{cite journal |doi=10.1109/MCG.2006.133 |pmid=17120916 |title=Modeling Crowd and Trained Leader Behavior during Building Evacuation |journal=IEEE Computer Graphics and Applications |volume=26 |issue=6 |pages=80–6 |year=2006 |last1=Pelechano |first1=Nuria |last2=Badler |first2=Norman |hdl=2117/10047 |hdl-access=free }}</ref>

There were two types of searching algorithms tried out for this implementation. There was the random search and the depth first search. A random search is where each of the agents go in any direction through the environment and try to find a pathway out. The depth first search is where agents follow one path as far as it can go then return and try another path if the path they traversed does not contain an exit. If was found that depth first search gave a speed up of 15 times versus a random search.

有两种类型的搜索算法试验了这种模型：''' 随机搜索 Random Search'''和'''深度优先搜索 Depth First Search'''。随机搜索是指每个主体在环境中朝任意方向前进，并试图找到一条出路。深度优先搜索是指主体尽可能沿着一条路径搜索，如果它们所经过的路径不包含出口则返回并尝试另一条路径。结果发现，深度优先搜索比随机搜索的速度快15倍。

=== Scalable simulations 可伸缩的模拟===

--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） Scalable 翻译为“可变的”会不会好一点？此处的搭配包括Scalable Agents，Scalable architecture 和Scalable simulations

--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar树|讨论]]） Scalable 好像没有“可变的”含义，可以是“可扩展的”

There are many different case situations that come into play in crowd simulations.<ref>{{cite book |doi=10.1109/ICPP.2008.20 |chapter=A Scalable Architecture for Crowd Simulation: Implementing a Parallel Action Server |title=2008 37th International Conference on ParallelProcessing |pages=430–7 |year=2008 |last1=Vigueras |first1=G. |last2=Lozano |first2=M. |last3=Pérez |first3=C. |last4=Orduña |first4=J.M. }}</ref> Recently, crowd simulation has been essential for the many virtual environment applications such as education, training, and entertainment. Many situations are based on the environment of the simulation or the behavior of the group of local agents. In virtual reality applications, every agent interacts with many other agents in the environment, calling for complex real-time interactions. Agents must have continuous changes in the environment since agent behaviors allow complex interactions. Scalable architecture can manage large crowds through the behavior and interactive rates. These situations will indicate how the crowds will act in multiple complex scenarios while several different situations are being applied. A situation can be any circumstance that has typical local behaviors. We can categorize all situations into two different kinds.

There are many different case situations that come into play in crowd simulations. Recently, crowd simulation has been essential for the many virtual environment applications such as education, training, and entertainment. Many situations are based on the environment of the simulation or the behavior of the group of local agents. In virtual reality applications, every agent interacts with many other agents in the environment, calling for complex real-time interactions. Agents must have continuous changes in the environment since agent behaviors allow complex interactions. Scalable architecture can manage large crowds through the behavior and interactive rates.'''These situations will indicate how the crowds will act in multiple complex scenarios while several different situations are being applied. A situation can be any circumstance that has typical local behaviors.''' We can categorize all situations into two different kinds.

在人群模拟中有许多不同的情况出现。<ref>{{cite book |doi=10.1109/ICPP.2008.20 |chapter=A Scalable Architecture for Crowd Simulation: Implementing a Parallel Action Server |title=2008 37th International Conference on Parallel Processing |pages=430–7 |year=2008 |last1=Vigueras |first1=G. |last2=Lozano |first2=M. |last3=Pérez |first3=C. |last4=Orduña |first4=J.M. }}</ref>近年来，人群模拟已经成为教育、训练、娱乐等虚拟环境应用中不可缺少的一部分。许多情况下的人群模拟是基于模拟的环境或一组局部主体的行为。在虚拟现实应用程序中，每个主体与环境中的许多其他主体进行交互，需要复杂的实时交互。由于主体行为允许复杂交互的特性，主体必须在环境中能够连续变化。'''可伸缩的架构 Scalable architecture'''可以通过行为和交互速率来管理大的人群。'''这些情况将表明人群在多个复杂情境下将如何采取行动，而几个不同的情况正在被应用。情境可以是任何具有典型局部行为的环境。'''--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar树|讨论]]）这两句说不通，situation到底指什么？
我们可以把所有的情境分为两种不同的类型。

''Spatial situation'' is a situation that has a region where the environment affects the local agents. For instance, a crowd waiting in line for a ticket booth would be displaying a spatial situation. Other examples may be a bus stop or an ATM where characters act upon their environment. Therefore, we would consider 'bus stop' as the situation if the behavior of the agents are to be getting on or off a bus.

Spatial situation is a situation that has a region where the environment affects the local agents. For instance, a crowd waiting in line for a ticket booth would be displaying a spatial situation. Other examples may be a bus stop or an ATM where characters act upon their environment. Therefore, we would consider 'bus stop' as the situation if the behavior of the agents are to be getting on or off a bus.

'''空间情境 Spatial Situation'''是指环境影响局部主体的区域。例如，一个售票亭前排队等候的人群就展示可一个空间情境。其他的例子，可能是一个公交车总站或者一个ATM机，在那里人依据其环境做出行动。因此，如果主体的行为可以是上车或下车，我们就可以把“公交车站”看作是一种空间情境。

''Non-Spatial situation'' has no region in the environment because this only involves the behavior of the crowd. The relationship of the local agents is an important factor to consider when determining behavior. An example would be a group of friends walking together. Typical behavior of characters that are friends would all move along with each other. This means that 'friendship' would be the situation among the typical behavior of walking together.

Non-Spatial situation has no region in the environment because this only involves the behavior of the crowd. The relationship of the local agents is an important factor to consider when determining behavior. An example would be a group of friends walking together. Typical behavior of characters that are friends would all move along with each other. This means that 'friendship' would be the situation among the typical behavior of walking together.

'''非空间情境 Non-Spatial situation'''是没有空间区域的环境，因为它只涉及到人群的行为。在决定行为时，局部主体之间的关系是一个重要的因素。一个例子是一群朋友一起散步。朋友的典型行为是各个主体都会互相影响。这意味着“友谊”是作为一起散步的典型行为的情境。

The structure of any situation is built upon four components, Behavior functions, Sensors, States, and Event Rules. Behavior functions represent what the characters behaviors are specific to the situation. Sensors are the sensing capability for agents to see and respond to events. States are the different motions and state transitions used only for the local behaviors. Event rule is the way to connect different events to their specific behaviors. While a character is being put into a situation, these four components are considered at the same time. For spatial situations, the components are added when the individual initially enters the environment that influences the character. For non-spatial situations, the character is affected only once the user assigns the situation to the character. The four components are removed when the agent is taken away from its situations region or the situation itself is removed. The dynamic adding and removing of the situations lets us achieve scalable agents.

The structure of any situation is built upon four components, Behavior functions, Sensors, States, and Event Rules. Behavior functions represent what the characters behaviors are specific to the situation. Sensors are the sensing capability for agents to see and respond to events. States are the different motions and state transitions used only for the local behaviors. Event rule is the way to connect different events to their specific behaviors. While a character is being put into a situation, these four components are considered at the same time. For spatial situations, the components are added when the individual initially enters the environment that influences the character. For non-spatial situations, the character is affected only once the user assigns the situation to the character. The four components are removed when the agent is taken away from its situations region or the situation itself is removed. The dynamic adding and removing of the situations lets us achieve scalable agents.

任何情境的结构都建立在四个组件之上: '''行为函数 Behavior Functions'''、'''传感器 Sensors'''、'''状态 States'''和'''事件规则 Event Rules'''。行为函数表示特定情况下的特定行为。传感器是一种感知能力，可以让主体看到并对事件做出反应。状态是仅用于局部行为的不同运动和状态转移。事件规则是将不同的事件与其特定的行为联系起来的方法。当一个角色被置于一个情境中时，这四个组件将被同时考虑。对于空间情景，当个体最初进入影响角色的环境时就添加组件。对于非空间情境，只有当用户将情境赋给角色时，角色才会受到影响。当主体被带离情境区域或情境本身被移除时，这四个组件被移除。动态地添加和删除这些情境使我们能够实现'''可伸缩的主体 Scalable Agents'''。

== Human-like behaviors and crowd AI 似人行为和群体人工智能==

[[File:Crowd simulation, Covent Garden.jpg|thumb|A crowd simulation of [[Covent Garden square]], London, showing a crowd of pedestrian agents reacting to a street performer]]

A crowd simulation of [[Covent Garden square, London, showing a crowd of pedestrian agents reacting to a street performer]]

一个人群模拟[[ Covent Garden 广场，伦敦，显示了一群行人主体对街头艺人的反应]]

{{Main|Swarm intelligence}}

To simulate more aspects of human activities in a crowd, more is needed than path and motion planning. Complex social interactions, smart object manipulation, and hybrid models are challenges in this area.Simulated crowd behavior is inspired by the flow of real-world crowds. Behavioral patterns, movement speeds and densities, and anomalies are [[crowd analysis|analyzed]] across many environments and building types. Individuals are [[crowd tracking|tracked]] and their movements are documented such that algorithms can be derived and implemented into crowd simulations.

To simulate more aspects of human activities in a crowd, more is needed than path and motion planning. Complex social interactions, smart object manipulation, and hybrid models are challenges in this area.Simulated crowd behavior is inspired by the flow of real-world crowds. Behavioral patterns, movement speeds and densities, and anomalies are analyzed across many environments and building types. Individuals are tracked and their movements are documented such that algorithms can be derived and implemented into crowd simulations.

为了模拟在人群中人类活动的更多方面，我们需要路径和运动规划以外的更多东西。复杂的社会交互、智能对象操纵和混合模型是这一领域的挑战。模拟人群行为的灵感来自于现实世界中的人群流。研究者分析了人群在许多环境和建筑类型中的行为模式、运动速度和密度以及异常情况。个体的行动被跟踪记录下来，这样就可以得到算法并应用到人群模拟中。

Individual entities in a crowd are also called [[Software agent|agents]]. In order for a crowd to behave realistically each agent should act autonomously (be capable of acting independently of the other agents). This idea is referred to as an ''agent-based model.'' Moreover, it is usually desired that the agents act with some degree of intelligence (i.e. the agents should not perform actions that would cause them to harm themselves). For agents to make intelligent and realistic decisions, they should act in accordance with their surrounding environment, react to its changes, and react to the other agents.

Individual entities in a crowd are also called agents. In order for a crowd to behave realistically each agent should act autonomously (be capable of acting independently of the other agents). This idea is referred to as an agent-based model. Moreover, it is usually desired that the agents act with some degree of intelligence (i.e. the agents should not perform actions that would cause them to harm themselves). For agents to make intelligent and realistic decisions, they should act in accordance with their surrounding environment, react to its changes, and react to the other agents.

群体中的独立的个体也称为主体。为了让一个群体真实地行动，每个主体应该自主地(能够独立于其他主体地)行动。这个想法被称为'''基于主体的模型 Agent-based Model'''。此外，人们通常希望主体的行为具有一定程度的智慧(即，主体不应采取伤害自己的行动)。为了使主体做出明智和真实的决定，他们应该根据他们周围的环境采取行动，对环境变化作出反应，并对其他主体作出反应。

=== Rule-based AI 基于规则的人工智能===

[[File:MaslowsHierarchyOfNeeds.svg|alt=Maslow's Hierarchy of Needs|thumb|Maslow's Hierarchy of Needs]]

Maslow's Hierarchy of Needs

马斯洛的需求层次理论

In rule-based AI, virtual agents follow scripts: "if this happens, do that". This is a good approach to take if agents with different roles are required, such as a main character and several background characters. This type of AI is usually implemented with a hierarchy, such as in [[Maslow's hierarchy of needs]], where the lower the need lies in the hierarchy, the stronger it is.

In rule-based AI, virtual agents follow scripts: "if this happens, do that". This is a good approach to take if agents with different roles are required, such as a main character and several background characters. This type of AI is usually implemented with a hierarchy, such as in Maslow's hierarchy of needs, where the lower the need lies in the hierarchy, the stronger it is.

在'''基于规则的人工智能 Rule-based AI'''中，虚拟主体遵循以下规则: “如果发生了这种情况，就那样做”。如果需要具有不同角色的主体，比如一个主角和几个背景角色，那么这是一个很好的方法。这种类型的人工智能通常是用层次结构来实现的，例如在'''马斯洛的需求层次结构 Maslow's hierarchy of needs'''中，需求层级越低，需求就越强。

For example, consider a student walking to class who encounters an explosion and runs away. The theory behind this is initially the first four levels of his needs are met, and the student is acting according to his need for self-actualization. When the explosion happens his safety is threatened which is a much stronger need, causing him to act according to that need.

For example, consider a student walking to class who encounters an explosion and runs away. The theory behind this is initially the first four levels of his needs are met, and the student is acting according to his need for self-actualization. When the explosion happens his safety is threatened which is a much stronger need, causing him to act according to that need.

例如，假设一个学生在走向教室的路上遭遇了爆炸并逃跑了。这背后的理论是他的前4个层次的需求得到了满足，并且学生是具有'''自我实现 self-actualization'''的需求并依次按照需求来行动。当爆炸发生时，他的安全受到威胁，这是一个比自我实现更强烈的需要，使他按照这种需要行事。

This approach is scalable, and can be applied to crowds with a large number of agents. Rule-based AI, however, does have some drawbacks. Most notably the behavior of the agents can become very predictable, which may cause a crowd to behave unrealistically.

This approach is scalable, and can be applied to crowds with a large number of agents. Rule-based AI, however, does have some drawbacks. Most notably the behavior of the agents can become very predictable, which may cause a crowd to behave unrealistically.

这种方法是可扩展的，可以应用于拥有大量主体的人群。然而，基于规则的人工智能确实有一些缺点。最值得注意的缺点是，主体的行为会变得可预测性很强，这可能导致群体的行为不现实。

=== Learning AI 学习型人工智能===

In learning AI, virtual characters behave in ways that have been tested to help them achieve their goals. Agents experiment with their environment or a sample environment which is similar to their real one.

In learning AI, virtual characters behave in ways that have been tested to help them achieve their goals. Agents experiment with their environment or a sample environment which is similar to their real one.

在'''学习型人工智能 Learning AI'''中，虚拟角色用一种经过了测试的方式帮助他们自己实现目标。主体用他们的环境或者一个类似于他们真实环境的样本环境进行测试。

Agents perform a variety of actions and learn from their mistakes. Each agent alters its behavior in response to rewards and punishments it receives from the environment. Over time, each agent would develop behaviors that are consistently more likely to earn high rewards.

Agents perform a variety of actions and learn from their mistakes. Each agent alters its behavior in response to rewards and punishments it receives from the environment. Over time, each agent would develop behaviors that are consistently more likely to earn high rewards.

主体进行各种各样的行动并从他们的错误中吸取经验。每个主体根据从环境中得到的奖励和惩罚改变其行为。随着时间的推移，每个主体都会发展更有可能获得高回报的行为。

If this approach is used, along with a large number of possible behaviors and a complex environment agents will act in a realistic and unpredictable fashion.

If this approach is used, along with a large number of possible behaviors and a complex environment agents will act in a realistic and unpredictable fashion.

如果使用这种方法，加上大量可能的行为和复杂的环境，主体将以一种现实的和不可预测的方式行事。

==== Algorithms 算法====

There are a wide variety of machine learning algorithms that can be applied to crowd simulations.

There are a wide variety of machine learning algorithms that can be applied to crowd simulations.

人群模拟现在已经有各种各样可以应用的机器学习算法。

Q-Learning is an algorithm residing under machine learning's sub field known as reinforcement learning. A basic overview of the algorithm is that each action is assigned a Q value and each agent is given the directive to always perform the action with the highest Q value. In this case learning applies to the way in which Q values are assigned, which is entirely reward based. When an agent comes in contact with a state, s, and action, a, the algorithm then estimates the total reward value that an agent would receive for performing that state action pair. After calculating this data, it is then stored in the agent's knowledge and the agent proceeds to act from there.

Q-Learning is an algorithm residing under machine learning's sub field known as reinforcement learning. A basic overview of the algorithm is that each action is assigned a Q value and each agent is given the directive to always perform the action with the highest Q value. In this case learning applies to the way in which Q values are assigned, which is entirely reward based. When an agent comes in contact with a state, s, and action, a, the algorithm then estimates the total reward value that an agent would receive for performing that state action pair. After calculating this data, it is then stored in the agent's knowledge and the agent proceeds to act from there.

Q-Learning是机器学习的子领域强化学习中的一个算法。一个对该算法的基本描述：每个动作都被分配了一个Q值，每个主体都被赋予一个总是执行Q值最高的动作的指令。在这种情况下，学习效果取决于分配Q值的方式，这完全是基于奖励的。当一个主体接触到一个状态 s 和一个动作 a 时，算法就会估计这个主体执行这个'''状态动作对 state action pair'''所能得到的总回报值。在计算这些数据之后，它们被存储在主体的知识中，主体依据这些知识开始行动。

（--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]） learning applies to the way in which Q values are assigned 翻译为学习效果取决于分配 q 值的方式，不知是否正确）

（--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）我觉得应该不是学习效果，应该是学习的内容）

The agent will constantly alter its behavior depending on the best Q value available to it. And as it explores more and more of the environment, it will eventually learn the most optimal state action pairs to perform in almost every situation.

The agent will constantly alter its behavior depending on the best Q value available to it. And as it explores more and more of the environment, it will eventually learn the most optimal state action pairs to perform in almost every situation.

主体会根据最佳Q值不断地改变自己的行为。随着它对环境的探索越来越多，它最终将学习到几乎每种情况下最佳状态动作对。

The following function outlines the bulk of the algorithm:

The following function outlines the bulk of the algorithm:

下面的函数概括了算法的大部分内容:

:''Q(s, a) ←− r + maxaQ(s', a')''

Q(s, a) ←− r + maxaQ(s', a')

Q(s, a) ←− r + maxaQ(s', a')

Given a state s and action a, r and s are the reward and state after performing (s,a), and a' is the range over all the actions.<ref>Torrey, L. Crowd Simulation Via Multi-agent Reinforcement Learning. In: ''Proceedings of the Sixth AAAI Conference On Artificial Intelligence and Interactive Digital Entertainment''. AAAI Press, Menlo Park (2010)</ref>

Given a state s and action a, r and s are the reward and state after performing (s,a), and a' is the range over all the actions.

给定一个状态s和动作a，r和s是执行(s,a)后的奖励和状态，
a'动作集。<ref>Torrey, L. Crowd Simulation Via Multi-agent Reinforcement Learning. In: ''Proceedings of the Sixth AAAI Conference On Artificial Intelligence and Interactive Digital Entertainment''. AAAI Press, Menlo Park (2010)</ref>
--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）r和s这句，我觉得s应该是s’吧

== Crowd rendering and animation 人群渲染和动画==

Rendering and animating a large number of agents realistically, especially in real time, is challenging. To reduce the complexity of 3D rendering of large-scale crowds, techniques like culling (discarding unimportant objects), impostors(image-based rendering) and decreasing levels of detail have been used.<ref>{{cite journal |doi=10.1109/76.825720 |title=Real-time display of virtual humans: Levels of details and impostors |journal=IEEE Transactions on Circuits and Systems for Video Technology |volume=10 |issue=2 |pages=207–17 |year=2000 |last1=Aubel |first1=A. |last2=Boulic |first2=R. |last3=Thalmann |first3=D. }}</ref>

Rendering and animating a large number of agents realistically, especially in real time, is challenging. To reduce the complexity of 3D rendering of large-scale crowds, techniques like culling (discarding unimportant objects), impostors(image-based rendering) and decreasing levels of detail have been used.

对大量主体进行真实地、特别是实时地渲染和动画绘制，是具有挑战性的。为了降低大规模人群3D渲染的复杂性，人们使用了剔除（舍弃不重要的物体）、顶替（基于图像的渲染）和降低细节的级别等技术。<ref>{{cite journal |doi=10.1109/76.825720 |title=Real-time display of virtual humans: Levels of details and impostors |journal=IEEE Transactions on Circuits and Systems for Video Technology |volume=10 |issue=2 |pages=207–17 |year=2000 |last1=Aubel |first1=A. |last2=Boulic |first2=R. |last3=Thalmann |first3=D. }}</ref>

Variations in appearance, body shape and size, accessories and behavior(social or cultural) exist in real crowds, and lack of variety affects the realism of visual simulations. Existing systems can create virtual crowds with varying texture,<ref name="Maim et al 2009"/> color,<ref>{{cite book |last1=Gosselin |first1=David R. |last2=Sander |first2=Pedro V. |last3=Mitchell |first3=Jason L. |chapter=Drawing a Crowd |editor1-first=Wolfgang |editor1-last=Engel |title=ShaderX3: Advanced Rendering Techniques in DirectX and OpenGL |publisher=Charles River Media |location=Cambridge, MA |year=2004 |pages=505–17 }}</ref> size, shape and animation.<ref name="Thalmann et al 2009"/>

Variations in appearance, body shape and size, accessories and behavior(social or cultural) exist in real crowds, and lack of variety affects the realism of visual simulations. Existing systems can create virtual crowds with varying texture, size, shape and animation.

真实的人群中存在着外貌、体型大小、附件和（社会的或文化的）行为的差异，缺乏多样性的模型会影响视觉模拟的真实性。现有的系统可以创建具有不同肌理、<ref name="Maim et al 2009"/> 颜色、<ref>{{cite book |last1=Gosselin |first1=David R. |last2=Sander |first2=Pedro V. |last3=Mitchell |first3=Jason L. |chapter=Drawing a Crowd |editor1-first=Wolfgang |editor1-last=Engel |title=ShaderX3: Advanced Rendering Techniques in DirectX and OpenGL |publisher=Charles River Media |location=Cambridge, MA |year=2004 |pages=505–17 }}</ref> 大小、形状和运动画面的虚拟人群。<ref name="Thalmann et al 2009"/>

（--[[用户:嘉树|嘉树]]（[[用户讨论:嘉树|讨论]]）最后一个animation译为运动画面了，译为“动画”呢？存疑）

（--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）动画吧

== Real world applications 在真实世界的应用==

=== Virtual cinematography 虚拟电影摄影===

Crowd simulations have been used widely across films as a cost-effective and realistic alternative from hiring actors and capturing shots that would otherwise be unrealistic. A significant example of its use lies in [[The Lord of the Rings (film series)]]. One of the most glaring problems for the production team in the initial stages were large-scale battles, as the author of the novels, J. R. R. Tolkien, envisioned them to have at least 50,000 participants. Such a number was unrealistic had they decided to only attempt to hire real actors and actresses. Instead they decided to use CG to simulate these scenes through the use of the Multiple Agent Simulation System in a Virtual Environment, otherwise known as MASSIVE. The Human Logic Engine based [[Autodesk Maya|Maya]] plugin for crowd simulation, [[Miarmy]], was used for the development of these sequences. The software allowed the filmmakers to provide each character model an agent based A.I. that could utilize a library of 350 animations. Based on sight, hearing, and touch parameters generated from the simulation, agents would react uniquely to each situation. Thus each simulation of the scene was unpredictable. The final product clearly displayed the advantages to using crowd simulation software.<ref>http://people.ucalgary.ca/~far/Lectures/SENG697/PDF/tutorials/2002/Multiple_Agent_Simulation_System_in_a_Virtual_Environment.pdf Davis Guy. Multiple Agent Simulation System in a Virtual Environment.</ref>

Crowd simulations have been used widely across films as a cost-effective and realistic alternative from hiring actors and capturing shots that would otherwise be unrealistic. A significant example of its use lies in The Lord of the Rings (film series). One of the most glaring problems for the production team in the initial stages were large-scale battles, as the author of the novels, J. R. R. Tolkien, envisioned them to have at least 50,000 participants. Such a number was unrealistic had they decided to only attempt to hire real actors and actresses. Instead they decided to use CG to simulate these scenes through the use of the Multiple Agent Simulation System in a Virtual Environment, otherwise known as MASSIVE. The Human Logic Engine based Maya plugin for crowd simulation, Miarmy, was used for the development of these sequences. The software allowed the filmmakers to provide each character model an agent based A.I. that could utilize a library of 350 animations. Based on sight, hearing, and touch parameters generated from the simulation, agents would react uniquely to each situation. Thus each simulation of the scene was unpredictable. The final product clearly displayed the advantages to using crowd simulation software.

人群模拟已经被广泛应用于电影中，它是一种相较雇佣演员和捕捉镜头来说更加低成本高收益且现实的替代方式，使用其他方法将是不真实的。电影《指环王》系列就是一个重要的例子。最初，制作团队面临最突出的问题之一是大规模的战斗，因为小说的作者约翰·罗纳德·瑞尔·托尔金 J. R. R. Tolkien设想这些战斗至少有50,000名参与者。如果制作团队决定只雇佣真人演员，这么多参与者是不现实的。他们决定使用CG来代替模拟这些场景，使用虚拟环境中的'''多主体仿真系统 Multiple Agent Simulation System'''，也就是众所周知的 MASSIVE 。'''群集动画 Miarmy'''，一个基于'''人类逻辑引擎 Human Logic Engine'''的人群模拟 Maya 插件，被用于开发这些动作序列。该软件允许制片人为每个角色提供一个基于主体的人工智能模型，这个模型可以利用一个有350个动画的数据库。基于通过模拟产生的视觉、听觉和触觉参数，主体将对每种不同的情况做出特定反应。因此，每个场景的模拟都是不可预知的。最终作品清晰地展示了使用人群模拟软件的优势。<ref>http://people.ucalgary.ca/~far/Lectures/SENG697/PDF/tutorials/2002/Multiple_Agent_Simulation_System_in_a_Virtual_Environment.pdf Davis Guy. Multiple Agent Simulation System in a Virtual Environment.</ref>

=== Urban planning 城市规划===

The development of crowd simulation software has become a modern and useful tool in designing urban environments. Whereas the traditional method of urban planning relies on maps and abstract sketches, a digital simulation is more capable of conveying both form and intent of design from architect to pedestrian. For example, street signs and traffic lights are localized visual cues that influence pedestrians to move and behave accordingly. Following this logic, a person is able to move from point A to point B in a way that is efficient and that a collective group of people can operate more effectively as a result. In a broader sense, bus systems and roadside restaurants serve a spatial purpose in their locations through an understanding of human movement patterns.<ref>http://papers.cumincad.org/data/works/att/ecaade2008_160.content.pdf Aschwanden, Gideon. Halatsch, Jan. Schmitt, Gerhard. Crowd Simulation for Urban Planning.</ref> The [[SimCity]] video game series exemplifies this concept in a more simplistic manner. In this series, the player assigns city development in designated zones while maintaining a healthy budget. The progression from empty land to a bustling city is fully controlled by the player's choices and the digital citizens behave as according to the city's design and events.

The development of crowd simulation software has become a modern and useful tool in designing urban environments. Whereas the traditional method of urban planning relies on maps and abstract sketches, a digital simulation is more capable of conveying both form and intent of design from architect to pedestrian. For example, street signs and traffic lights are localized visual cues that influence pedestrians to move and behave accordingly. Following this logic, a person is able to move from point A to point B in a way that is efficient and that a collective group of people can operate more effectively as a result. In a broader sense, bus systems and roadside restaurants serve a spatial purpose in their locations through an understanding of human movement patterns. The SimCity video game series exemplifies this concept in a more simplistic manner. In this series, the player assigns city development in designated zones while maintaining a healthy budget. The progression from empty land to a bustling city is fully controlled by the player's choices and the digital citizens behave as according to the city's design and events.

人群模拟软件的发展为现代城市环境设计提供了一个有用的工具。传统的城市规划方法依赖于地图和抽象的草图，而数字仿真更能将设计的形式和意图从建筑设计师传达给行人。例如，街道标志和交通灯是局部视觉线索，能够影响行人的移动和相应的行为。按照这个逻辑，如果一个人能够以一种高效的方式从 a 点移动到 b 点，一群人就能够高效地运作。在更广泛的意义上，公交系统和路边餐馆通过对人类运动模式的理解，在其位置起到空间上的作用。<ref>http://papers.cumincad.org/data/works/att/ecaade2008_160.content.pdf Aschwanden, Gideon. Halatsch, Jan. Schmitt, Gerhard. Crowd Simulation for Urban Planning.</ref>模拟城市SimCity视频游戏系列以一种更简单的方式举例说明了这个概念。在这个系列中，玩家在指定的区域指导城市的发展，同时保持平衡的收支。从空地到繁华城市的过程完全由玩家的选择来控制，而数字市民的行为则根据城市的设计和事件而定。

=== Evacuation and riot handling 疏散和暴乱处理===

Simulated realistic crowds can be used in training for riots handling, architecture, safety science (evacuation planning).

Simulated realistic crowds can be used in training for riots handling, architecture, safety science (evacuation planning).

模拟真实的人群可用于训练暴乱处理、建筑、安全科学（疏散计划 Evacuation ）。

=== Military 军队===

Being that crowd simulations are so prevalent in use for public planning and general order with regards to chaotic situations, many applications can be drawn for governmental and military simulations. Crowd modeling is essential in police and military simulation in order to train officers and soldiers to deal with mass gatherings of people. Not only do offensive combatants prove to be difficult for these individuals to handle, but noncombatant crowds play significant roles in making these aggressive situations more out of control. Game technology is used in order to simulate these situations for soldiers and technicians to practice their skills.<ref>{{cite journal |doi=10.1177/1046878107308092 |title=Integrating crowd-behavior modeling into military simulation using game technology |journal=Simulation & Gaming |volume=39 |pages=10–38 |year=2007 |last1=McKenzie |first1=F. D. |last2=Petty |first2=M. D. |last3=Kruszewski |first3=P. A. |last4=Gaskins |first4=R. C. |last5=Nguyen |first5=Q.-A. H. |last6=Seevinck |first6=J. |last7=Weisel |first7=E. W. }}</ref>

Being that crowd simulations are so prevalent in use for public planning and general order with regards to chaotic situations, many applications can be drawn for governmental and military simulations. Crowd modeling is essential in police and military simulation in order to train officers and soldiers to deal with mass gatherings of people. Not only do offensive combatants prove to be difficult for these individuals to handle, but noncombatant crowds play significant roles in making these aggressive situations more out of control. Game technology is used in order to simulate these situations for soldiers and technicians to practice their skills.

由于人群模拟是如此普遍地应用于公共规划和建立混乱情境中的一般秩序，许多应用程序可以用于绘制政府的和军队的模拟。为了训练官兵对群众集会的应对能力，人群模型在警察和军队推演中是必不可少的。在这些模拟中，不仅进攻性的战斗人员很难处理，非战斗人员也在使这些斗争场景更加失控的方面发挥了重要的作用。因此游戏技术被用来模拟这些情境，以使士兵和技术人员实践他们的技能。<ref>{{cite journal |doi=10.1177/1046878107308092 |title=Integrating crowd-behavior modeling into military simulation using game technology |journal=Simulation & Gaming |volume=39 |pages=10–38 |year=2007 |last1=McKenzie |first1=F. D. |last2=Petty |first2=M. D. |last3=Kruszewski |first3=P. A. |last4=Gaskins |first4=R. C. |last5=Nguyen |first5=Q.-A. H. |last6=Seevinck |first6=J. |last7=Weisel |first7=E. W. }}</ref>

=== Sociology 社会学===

The behavior of a modeled crowd plays a prominent role in analytical matters. These dynamics rely on the physical behaviors of individual agents within a crowd rather than the visual reality of the model itself. The social behaviors of people within these constructs have been of interest for many years, and the sociological concepts which underpin these interactions are constantly studied. The simulation of crowds in different situations allows for sociological study of real life gatherings in a variety of arrangements and locations. The variations in human behavior in situations varying in stress-levels allows for the further development and creation of crowd control strategies which can be more specifically applied to situations rather than generalized.

The behavior of a modeled crowd plays a prominent role in analytical matters. These dynamics rely on the physical behaviors of individual agents within a crowd rather than the visual reality of the model itself. The social behaviors of people within these constructs have been of interest for many years, and the sociological concepts which underpin these interactions are constantly studied. The simulation of crowds in different situations allows for sociological study of real life gatherings in a variety of arrangements and locations. The variations in human behavior in situations varying in stress-levels allows for the further development and creation of crowd control strategies which can be more specifically applied to situations rather than generalized.

模型群体的行为在分析问题时有重要的作用。这些动画依赖于独立主体在群体中的物理行为，而不是模型本身的视觉现实。多年来，人们在这些结构中的社会行为一直是研究者感兴趣的问题，支撑这些互动的社会学概念也被持续地研究。不同情境下的人群模拟使现实生活中不同场景地点集会的社会学研究得以进行。人类在压力水平不同的情境下的行为差异可以用来进一步发展和创造人群控制策略，这种策略可以更具体而不是空泛地应用于所有情况。

== See also 参见==

* [[3D computer graphics]] 3D计算机图形学

* [[Artificial intelligence]] 人工智能

* [[Crowd analysis]] 人群分析

* [[Emergent behavior]] 涌现行为

* [[Multi-agent system]] 多主体系统

* [[Particle system]] 粒子系统

== Crowd simulation software 人群模拟软件==

* Alice Software by the [[Moving Picture Company]]

* [[Golaem Crowd]]

* [[Massive (software)]]

* [[Miarmy]]

* [[Quadstone Paramics]]

* [[VISSIM]]

== References 参考文献==

{{Reflist|30em}}

== External links 外部链接==





! ——维基百科不是公司或产品的外部链接目录——

* [https://web.archive.org/web/20130627102118/http://steersuite.cse.yorku.ca/ SteerSuite], An open-source framework for developing and evaluating crowd simulation algorithms

* {{cite journal |doi=10.1111/j.1467-8659.2004.00783.x |title=Scalable behaviors for crowd simulation |journal=Computer Graphics Forum |volume=23 |issue=3 |pages=519–28 |year=2004 |last1=Sung |first1=Mankyu |last2=Gleicher |first2=Michael |last3=Chenney |first3=Stephen |citeseerx=10.1.1.10.2516 }}

{{Animation}}

{{collective animal behaviour}}

[[Category:Crowds]]

Category:Crowds

类别: Crowds

[[Category:Computer animation]]

Category:Computer animation

类别: 电脑动画

[[Category:3D computer graphics]]

Category:3D computer graphics

类别: 三维计算机图形

[[Category:Social physics]]

Category:Social physics

类别: 社会物理学

<noinclude>

This page was moved from [[wikipedia:en:Crowd simulation]]. Its edit history can be viewed at [[人群模拟/edithistory]]</noinclude>

[[Category:待整理页面]]

== 编者推荐 ==
=== 集智课程推荐 ===
[https://campus.swarma.org/course/592 群体模拟与Netlogo] 在本节课程中我们将从理论回到现实中学习到实际的本领：关于Netlogo的操作。

[https://campus.swarma.org/course/1095 NetLogo多主体建模入门] 本课程通过数个案例教会大家如何去动手搭建一个多主体仿真模型，以及如何利用NetLogo去实现。从生命游戏到人工鸟群，从模拟经济系统到病毒沿网络的传播，通过循序渐进的案例，该课程带你逐步走入NetLogo多主体建模的神奇世界。

[https://campus.swarma.org/course/1112 复杂性思维2020] 本课程中，张江老师将用一套自己搭建的“复杂性阶梯”的框架串联起众多复杂性科学概念，包括混沌、秩序、自催化网络、涌现、混沌边缘、热力学第二定律、分形、网络、自指等等。

=== 书籍推荐 ===
[https://book.douban.com/subject/11549281/ 人群模拟 Crowd Simulation]本书由提出人群模拟概念的Daniel Thalmann 和 Soraia Raupp Musse 编著，包括人群建模和评价模型的方法。本书在2013年有最新版本(第二版)，尚无中文译本。

级联失效

2020-12-07T14:24:59Z

WildBoar：

本词条由11初步翻译，已由WildBoar完成审校

{{short description|System of interconnected parts in which the failure of one or few parts can trigger the failure of others}}

[[Image:Networkfailure.gif|thumb|right|An animation demonstrating how a single failure may result in other failures throughout a network.]]

[[Image:Networkfailure.gif|thumb|right|演示单个故障如何导致整个网络中其他故障的动画]]

An animation demonstrating how a single failure may result in other failures throughout a network.

演示单个故障如何导致整个网络中其他故障的动画。

A cascading failure is a process in a system of [[interconnection|interconnected]] parts in which the failure of one or few parts can trigger the failure of other parts and so on. Such a failure may happen in many types of systems, including power transmission, computer networking, finance, transportation systems, organisms, the human body, and ecosystems.

A cascading failure is a process in a system of interconnected parts in which the failure of one or few parts can trigger the failure of other parts and so on. Such a failure may happen in many types of systems, including power transmission, computer networking, finance, transportation systems, organisms, the human body, and ecosystems.

在一个部件相互连接的系统中，一个或几个部件的故障会引发其他部件的故障的过程就是''' 级联失效 Cascading Failure'''（也可译为级联故障）。这种故障可能发生在许多类型的系统中，包括电力输送、计算机网络、金融、交通系统、生物体、人体和生态系统。

Cascading failures may occur when one part of the system fails. When this happens, other parts must then compensate for the failed component. This in turn overloads these nodes, causing them to fail as well, prompting additional nodes to fail one after another.

Cascading failures may occur when one part of the system fails. When this happens, other parts must then compensate for the failed component. This in turn overloads these nodes, causing them to fail as well, prompting additional nodes to fail one after another.

当系统的一部分发生故障时，可能会发生级联失效。当这种情况发生时，其他部分必须对发生故障的部分进行补偿，这反过来又会使这些节点超载，使它们也发生故障，导致更多的节点相继发生故障。

== In power transmission ==
在电力输送中

Cascading failure is common in [[power grid]]s when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in [[high voltage]] systems, where a [[single point of failure]] (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

Cascading failure is common in power grids when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in high voltage systems, where a single point of failure (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

级联失效在电网中很常见，当其中一个元件(完全或部分)发生故障并将其负荷转移到系统中附近的元件时，就会推动那些附近的元件超出其容量，从而过载，并将其负荷转移到其他元件上。级联失效在高压系统中也很常见，在一个满载或轻度过载的系统中，一个''' 单点故障 Single Point of Failure (SPF)'''会导致系统所有节点突然出现尖峰。这种''' 浪涌电流 Surge Current'''可能会导致已经过载的节点发生故障，引发更多过载，从而在很短的时间内使整个系统瘫痪。

This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer.

This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer.

这个故障过程就像池塘上的涟漪一样，在系统的各个元件之间蔓延，直到系统中的所有元件都受到损害和/或系统在功能上与负载源断开。例如，在某些情况下，一个大型电网可能因为单个变压器的故障而崩溃。

Monitoring the operation of a system, in [[real-time computing|real-time]], and judicious disconnection of parts can help stop a cascade. Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures.<ref name="chao">{{cite arXiv |last1=Zhai |first1=Chao |title=Modeling and Identification of Worst-Case Cascading Failures in Power Systems |eprint=1703.05232 |class=cs.SY |year=2017}}</ref>

Monitoring the operation of a system, in real-time, and judicious disconnection of parts can help stop a cascade. Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures.

实时监测系统的运行情况，并明智地断开部件的连接，有助于阻止级联。另一种常见的技术是通过计算机模拟可能发生的故障来计算系统的安全边际，确定安全运行水平，在此水平之下，计算出的任何一种情况都不会引起级联失效，并确定网络中最有可能引起级联失效的部分。<ref name="chao">{{cite arXiv |last1=Zhai |first1=Chao |title=Modeling and Identification of Worst-Case Cascading Failures in Power Systems |eprint=1703.05232 |class=cs.SY |year=2017}}</ref>

One of the primary problems with preventing electrical grid failures is that the speed of the control signal is no faster than the speed of the propagating power overload, i.e. since both the control signal and the electrical power are moving at the same speed, it is not possible to isolate the outage by sending a warning ahead to isolate the element.

One of the primary problems with preventing electrical grid failures is that the speed of the control signal is no faster than the speed of the propagating power overload, i.e. since both the control signal and the electrical power are moving at the same speed, it is not possible to isolate the outage by sending a warning ahead to isolate the element.

防止电网故障的主要困难之一是控制信号的速度比传播电力过载的速度慢，即由于控制信号和电力都以同样的速度运动，所以无法通过提前发出警告来隔离元件从而隔离故障。

The question if power grid failures are correlated have been studied in Daqing Li et al.<ref>{{Cite journal|last=Daqing|first=Li|last2=Yinan|first2=Jiang|last3=Rui|first3=Kang|last4=Havlin|first4=Shlomo|date=2014-06-20|title=Spatial correlation analysis of cascading failures: Congestions and Blackouts|journal=Scientific Reports|language=En|volume=4|issue=1|pages=5381|doi=10.1038/srep05381|pmid=24946927|pmc=4064325|issn=2045-2322|bibcode=2014NatSR...4E5381D}}</ref> as well as by Paul DH Hines et al.<ref>{{Cite journal|last=Hines|first=Paul D. H.|last2=Dobson|first2=Ian|last3=Rezaei|first3=Pooya|date=2016|title=Cascading Power Outages Propagate Locally in an Influence Graph that is not the Actual Grid Topology|arxiv=1508.01775|journal=IEEE Transactions on Power Systems|pages=1|doi=10.1109/TPWRS.2016.2578259|issn=0885-8950}}</ref>

The question if power grid failures are correlated have been studied in Daqing Li et al. as well as by Paul DH Hines et al.

电网故障是否具有相关性的问题，李大庆 Daqing Li等人<ref>{{Cite journal|last=Daqing|first=Li|last2=Yinan|first2=Jiang|last3=Rui|first3=Kang|last4=Havlin|first4=Shlomo|date=2014-06-20|title=Spatial correlation analysis of cascading failures: Congestions and Blackouts|journal=Scientific Reports|language=En|volume=4|issue=1|pages=5381|doi=10.1038/srep05381|pmid=24946927|pmc=4064325|issn=2045-2322|bibcode=2014NatSR...4E5381D}}</ref> 以及保罗·DH·海恩斯 Paul DH Hines等人都有研究。<ref>{{Cite journal|last=Hines|first=Paul D. H.|last2=Dobson|first2=Ian|last3=Rezaei|first3=Pooya|date=2016|title=Cascading Power Outages Propagate Locally in an Influence Graph that is not the Actual Grid Topology|arxiv=1508.01775|journal=IEEE Transactions on Power Systems|pages=1|doi=10.1109/TPWRS.2016.2578259|issn=0885-8950}}</ref>

=== Examples ===
案例

Cascading failure caused the following [[power outage]]s:

Cascading failure caused the following power outages:

级联失效曾导致以下停电:

* [[Northeast blackout of 1965|Blackout in Northeast America in 1965]]
* [[1965年东北大停电|1965年美国东北大停电]]

* [[1999 Southern Brazil blackout|Blackout in Southern Brazil in 1999]]
* [[1999年巴西南部停电|1999年巴西南部停电]]

* [[Northeast blackout of 2003|Blackout in Northeast America in 2003]]
* [[2003年东北大停电|2003年美国东北大停电]]

* [[2003 Italy blackout|Blackout in Italy in 2003]]
* [[2003年意大利停电|2003年意大利停电]]

* [[2003 London blackout|Blackout in London in 2003]]
* [[2003年伦敦大停电|2003年伦敦大停电]]

* [[2006 European blackout|European Blackout in 2006]]
* [[2006年欧洲停电|2006年欧洲停电]]

* [[2012 northern India power grid failure|Blackout in Northern India in 2012]]
* [[2012年印度北部电网故障|2012年印度北部停电]]

* [[2016 South Australian blackout|Blackout in South Australia in 2016]]
* [[2016年南澳停电|2016年南澳停电]]

* [[2019 Argentina, Paraguay and Uruguay blackout|Blackout in southeast South America in 2019]]
* [[2019年阿根廷、巴拉圭和乌拉圭停电|2019年南美洲东南部停电]]

== In computer networks ==
在计算机网络中

Cascading failures can also occur in [[computer network]]s (such as the [[Internet]]) in which [[Network traffic control|network traffic]] is severely impaired or halted to or between larger sections of the network, caused by failing or disconnected hardware or software. In this context, the cascading failure is known by the term '''cascade failure'''. A cascade failure can affect large groups of people and systems.

Cascading failures can also occur in computer networks (such as the Internet) in which network traffic is severely impaired or halted to or between larger sections of the network, caused by failing or disconnected hardware or software. In this context, the cascading failure is known by the term cascade failure. A cascade failure can affect large groups of people and systems.

级联失效也可能发生在计算机网络(如因特网)中，由于硬件或软件的故障或断开，导致网络中较大部分的网络通信严重受损或停止。在这种情况下，级联失效被称为术语 “cascade failure”。级联失效会影响到大批人员和系统。

The cause of a cascade failure is usually the overloading of a single, crucial [[Router (computing)|router]] or node, which causes the node to go down, even briefly. It can also be caused by taking a node down for maintenance or upgrades. In either case, traffic is [[routing|routed]] to or through another (alternative) path. This alternative path, as a result, becomes overloaded, causing it to go down, and so on. It will also affect systems which depend on the node for regular operation.

The cause of a cascade failure is usually the overloading of a single, crucial router or node, which causes the node to go down, even briefly. It can also be caused by taking a node down for maintenance or upgrades. In either case, traffic is routed to or through another (alternative) path. This alternative path, as a result, becomes overloaded, causing it to go down, and so on. It will also affect systems which depend on the node for regular operation.

级联失效的原因通常是一个单个关键的路由器或节点的超载，导致节点宕机即使是短暂地宕机。它也可能是由于为了维护或升级而关闭一个节点引起的。在这两种情况下，流量都被路由到达或通过另一条(替代)路径。结果，这条替代路径变得过载，导致宕机，等等。它还会影响依赖该节点正常运行的系统。

=== Symptoms ===
症状

The symptoms of a cascade failure include: [[packet loss]] and high network [[lag|latency]], not just to single systems, but to whole sections of a network or the internet. The high latency and packet loss is caused by the nodes that fail to operate due to [[congestion collapse]], which causes them to still be present in the network but without much or any useful communication going through them. As a result, routes can still be considered valid, without them actually providing communication.

The symptoms of a cascade failure include: packet loss and high network latency, not just to single systems, but to whole sections of a network or the internet. The high latency and packet loss is caused by the nodes that fail to operate due to congestion collapse, which causes them to still be present in the network but without much or any useful communication going through them. As a result, routes can still be considered valid, without them actually providing communication.

级联失效的症状包括: 数据包丢失和高网络延迟，不仅仅是对单个系统，而是对整个网络或互联网。高延迟和数包丢失是由于网络 拥塞崩溃 congestion collapse导致节点无法正常运行，这使得数据仍然存在于网络中，但是没有太多或任何有用的通道来传输它们。因此，路由仍然可被认为是有效的，而实际上它们并没有提供通信。

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）“级联失效的症状”中的症状是不是可以思考换一下词语印象中症状一般形容人换成“表现”或其他是否更好
--[[用户:WildBoar|WildBoar]]（[[用户讨论:WildBoar|讨论]]）我觉得两种表达都可以

If enough routes go down because of a cascade failure, a complete section of the network or internet can become unreachable. Although undesired, this can help speed up the recovery from this failure as connections will time out, and other nodes will give up trying to establish connections to the section(s) that have become cut off, decreasing load on the involved nodes.

If enough routes go down because of a cascade failure, a complete section of the network or internet can become unreachable. Although undesired, this can help speed up the recovery from this failure as connections will time out, and other nodes will give up trying to establish connections to the section(s) that have become cut off, decreasing load on the involved nodes.

如果有够多的路由因为级联失效而中断，网络或互联网的一个完整部分就会无法访问。尽管我们不希望出现这种情况，但这有助于加快从故障中恢复，因为连接会超时，其他节点会放弃尝试与被切断的部分建立连接，从而减少相关节点的负载。

A common occurrence during a cascade failure is a '''walking failure''', where sections go down, causing the next section to fail, after which the first section comes back up. This '''ripple''' can make several passes through the same sections or connecting nodes before stability is restored.

A common occurrence during a cascade failure is a walking failure, where sections go down, causing the next section to fail, after which the first section comes back up. This ripple can make several passes through the same sections or connecting nodes before stability is restored.

在级联失效中，一个常见的现象是行走故障，即各段下行，导致下一段故障，之后第一段回升。在恢复稳定之前，这种波纹可能会在相同的区段或连接节点上进行多次传递。

=== History ===
历史

Cascade failures are a relatively recent development, with the massive increase in traffic and the high interconnectivity between systems and networks. The term was first applied in this context in the late 1990s by a Dutch IT professional and has slowly become a relatively common term for this kind of large-scale failure.{{Citation needed|date=January 2009}}

Cascade failures are a relatively recent development, with the massive increase in traffic and the high interconnectivity between systems and networks. The term was first applied in this context in the late 1990s by a Dutch IT professional and has slowly become a relatively common term for this kind of large-scale failure.

级联故障是最近随着流量的大量增加以及系统和网络之间的高互联性而出现的。这个术语最早是在90年代末由一位荷兰的IT专业人员在这样的背景下使用的，后来慢慢成为一个形容这种大规模故障的比较常见的术语。

=== Example ===
案例

Network failures typically start when a single network node fails. Initially, the traffic that would normally go through the node is stopped. Systems and users get errors about not being able to reach hosts. Usually, the redundant systems of an ISP respond very quickly, choosing another path through a different backbone. The routing path through this alternative route is longer, with more [[Hop (telecommunications)|hops]] and subsequently going through more systems that normally do not process the amount of traffic suddenly offered.

Network failures typically start when a single network node fails. Initially, the traffic that would normally go through the node is stopped. Systems and users get errors about not being able to reach hosts. Usually, the redundant systems of an ISP respond very quickly, choosing another path through a different backbone. The routing path through this alternative route is longer, with more hops and subsequently going through more systems that normally do not process the amount of traffic suddenly offered.

网络故障通常始于单个网络节点故障。首先，正常经过该节点的流量停止，系统和用户会得到流量无法到达主机的错误提示。通常，ISP的冗余系统会很快做出反应，选择另一条通过不同骨干网的路径。这条替代路径通过的路由路径更长，跳数更多，随后还要经过更多的系统，而这些系统通常不会处理突发的流量。

This can cause one or more systems along the alternative route to go down, creating similar problems of their own.

This can cause one or more systems along the alternative route to go down, creating similar problems of their own.

这可能会导致替代路线上的一个或多个系统瘫痪，造成类似故障系统的问题。

Also, related systems are affected in this case. As an example, [[Domain name system|DNS]] resolution might fail and what would normally cause systems to be interconnected, might break connections that are not even directly involved in the actual systems that went down. This, in turn, may cause seemingly unrelated nodes to develop problems, that can cause another cascade failure all on its own.

Also, related systems are affected in this case. As an example, DNS resolution might fail and what would normally cause systems to be interconnected, might break connections that are not even directly involved in the actual systems that went down. This, in turn, may cause seemingly unrelated nodes to develop problems, that can cause another cascade failure all on its own.

此外，在这种情况下，相关系统也会受到影响。例如，DNS解析可能会失败，那些通常会造成系统互连的情况可能会破坏一些连接，这些连接甚至没有直接参与实际发生故障的系统。而这又可能导致看似不相关的节点出现问题，从而导致另一个级联失效的发生。

In December 2012, a partial loss (40%) of [[Gmail]] service occurred globally, for 18 minutes. This loss of service was caused by a routine update of load balancing software which contained faulty logic—in this case, the error was caused by logic using an [https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ inappropriate ''all'' instead of the more appropriate ''some''.] The cascading error was fixed by fully updating a single node in the network instead of partially updating all nodes at one time.

In December 2012, a partial loss (40%) of Gmail service occurred globally, for 18 minutes. This loss of service was caused by a routine update of load balancing software which contained faulty logic—in this case, the error was caused by logic using an [https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ inappropriate all instead of the more appropriate some.] The cascading error was fixed by fully updating a single node in the network instead of partially updating all nodes at one time.

2012年12月，Gmail服务在全球范围内出现了部分损失(40%)，持续了18分钟。这次服务损失是由包含错误逻辑的负载平衡软件的例行更新引起的——在这种情况下，该错误是由使用[https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ 不合适的all而不是更合适的some]的逻辑引起的。通过完全更新网络中的一个节点，而不是部分更新所有节点，修复了级联失效。

== Cascading structural failure ==
级联结构失效

Certain load-bearing structures with discrete structural components can be subject to the "zipper effect", where the failure of a single structural member increases the load on adjacent members. In the case of the [[Hyatt Regency walkway collapse]], a suspended walkway (which was already overstressed due to an error in construction) failed when a single vertical suspension rod failed, overloading the neighboring rods which failed sequentially (i.e. like a [[zipper]]). A bridge that can have such a failure is called fracture critical, and numerous bridge collapses have been caused by the failure of a single part. Properly designed structures use an adequate [[factor of safety]] and/or alternate load paths to prevent this type of mechanical cascade failure.<ref name="petroski">{{cite book| title=To Engineer Is Human: The Role of Failure in Structural Design| first=Henry| last=Petroski| year=1992| isbn=978-0-679-73416-1| publisher=Vintage| place=| url-access=registration| url=https://archive.org/details/toengineerishuma00petr}}</ref>

Certain load-bearing structures with discrete structural components can be subject to the "zipper effect", where the failure of a single structural member increases the load on adjacent members. In the case of the Hyatt Regency walkway collapse, a suspended walkway (which was already overstressed due to an error in construction) failed when a single vertical suspension rod failed, overloading the neighboring rods which failed sequentially (i.e. like a zipper). A bridge that can have such a failure is called fracture critical, and numerous bridge collapses have been caused by the failure of a single part. Properly designed structures use an adequate factor of safety and/or alternate load paths to prevent this type of mechanical cascade failure.

某些具有离散结构构件的承重结构可能会出现 "拉链效应"，即单个结构构件的失效会增加相邻构件的荷载。在凯悦酒店人行道坍塌事件中，当单根垂直悬杆失效时，悬空的人行道（由于施工中的错误，人行道已经过度受力）倒塌，使相邻的悬杆超载，相邻的悬杆依次失效（像拉链一样）。一座可能发生这种倒塌的桥梁被称为断裂临界桥梁，许多桥梁的坍塌都是由单一部件的故障引起的。正确设计的结构使用足够安全系数的和/或交替的荷载路径来防止这种类型的机械级联失效。<ref name="petroski">{{cite book| title=To Engineer Is Human: The Role of Failure in Structural Design| first=Henry| last=Petroski| year=1992| isbn=978-0-679-73416-1| publisher=Vintage| place=| url-access=registration| url=https://archive.org/details/toengineerishuma00petr}}</ref>

== Other examples ==
其他例子

=== Biology ===
生物

[[Biochemical cascade]]s exist in biology, where a small reaction can have system-wide implications. One negative example is [[ischemic cascade]], in which a small [[ischemia|ischemic]] attack releases [[toxin]]s which kill off far more cells than the initial damage, resulting in more toxins being released. Current research is to find a way to block this cascade in [[stroke]] patients to minimize the damage.

Biochemical cascades exist in biology, where a small reaction can have system-wide implications. One negative example is ischemic cascade, in which a small ischemic attack releases toxins which kill off far more cells than the initial damage, resulting in more toxins being released. Current research is to find a way to block this cascade in stroke patients to minimize the damage.

生物学中存在着生化级联，一个小的反应就会对整个系统产生影响。一个负面的例子是缺血性级联反应，在这种反应中，一个小的脑缺血发作释放出的毒素比最初的损伤杀死更多的细胞，导致更多的毒素被释放。目前的研究正在寻找一种方法来阻断中风患者的这种级联反应，以最大限度地减少损伤。

In the study of extinction, sometimes the extinction of one species will cause many other extinctions to happen. Such a species is known as a [[keystone species]].

In the study of extinction, sometimes the extinction of one species will cause many other extinctions to happen. Such a species is known as a keystone species.

在物种灭绝的研究中，有时一个物种的灭绝会导致许多其他物种的灭绝。这样的物种被称为 关键种 keystone species。

=== Electronics ===
电子学

Another example is the [[Cockcroft–Walton generator]], which can also experience cascade failures wherein one failed [[diode]] can result in all the diodes failing in a fraction of a second.

Another example is the Cockcroft–Walton generator, which can also experience cascade failures wherein one failed diode can result in all the diodes failing in a fraction of a second.

另一个例子是Cockcroft-Walton发电机，它也会发生级联失效，其中一个故障的二极管会导致所有二极管在顷刻间发生故障。

Yet another example of this effect in a scientific experiment was the [[Implosion (mechanical process)|implosion]] in 2001 of several thousand fragile glass photomultiplier tubes used in the [[Super-Kamiokande]] experiment, where the shock wave caused by the failure of a single detector appears to have triggered the implosion of the other detectors in a chain reaction.

Yet another example of this effect in a scientific experiment was the implosion in 2001 of several thousand fragile glass photomultiplier tubes used in the Super-Kamiokande experiment, where the shock wave caused by the failure of a single detector appears to have triggered the implosion of the other detectors in a chain reaction.

在科学实验中，这种效应的另一个例子是2001年用于超级神冈探测器实验中的几千支易碎的玻璃光电倍增管发生内爆，其中一个探测器的故障造成的冲击波似乎引发了其他探测器的内爆，形成了连锁反应。

=== Finance ===
金融

{{main|Systemic risk}} {{main|Cascades in financial networks}}
{{主要}系统性风险}} {{主要}金融网络中的级联}}}

In [[finance]], the risk of cascading failures of financial institutions is referred to as ''[[systemic risk]]:'' the failure of one financial institution may cause other financial institutions (its [[Counterparty|counterparties]]) to fail, cascading throughout the system.<ref name="HuangVodenska2013">{{cite journal|last1=Huang|first1=Xuqing|last2=Vodenska|first2=Irena|last3=Havlin|first3=Shlomo|last4=Stanley|first4=H. Eugene|title=Cascading Failures in Bi-partite Graphs: Model for Systemic Risk Propagation|journal=Scientific Reports|volume=3|pages=1219|year=2013|issn=2045-2322|doi=10.1038/srep01219|pmid=23386974|pmc=3564037|arxiv=1210.4973|bibcode=2013NatSR...3E1219H}}</ref>

In finance, the risk of cascading failures of financial institutions is referred to as systemic risk: the failure of one financial institution may cause other financial institutions (its counterparties) to fail, cascading throughout the system.

在金融领域，金融机构连锁倒闭的风险被称为系统性风险：一家金融机构的倒闭可能会引起其他金融机构（其交易对手）的倒闭，在整个系统中连锁倒闭。<ref name="HuangVodenska2013">{{cite journal|last1=Huang|first1=Xuqing|last2=Vodenska|first2=Irena|last3=Havlin|first3=Shlomo|last4=Stanley|first4=H. Eugene|title=Cascading Failures in Bi-partite Graphs: Model for Systemic Risk Propagation|journal=Scientific Reports|volume=3|pages=1219|year=2013|issn=2045-2322|doi=10.1038/srep01219|pmid=23386974|pmc=3564037|arxiv=1210.4973|bibcode=2013NatSR...3E1219H}}</ref>

Institutions that are believed to pose systemic risk are deemed either "[[too big to fail]]" (TBTF) or "too interconnected to fail" (TICTF), depending on why they appear to pose a threat.

Institutions that are believed to pose systemic risk are deemed either "too big to fail" (TBTF) or "too interconnected to fail" (TICTF), depending on why they appear to pose a threat.

那些被认为构成系统性风险的机构要么被视为“太大而不能倒”(TBTF) ，要么被视为“太相关而不能倒闭”(TICTF) ，这取决于它们为什么会构成威胁。

Note however that systemic risk is not due to individual institutions per se, but due to the interconnections. For detailed models in economics and finance, see Elliott et al. (2014) and Acemoglu et al. (2015).<ref name="Acemoglu Ozdaglar Tahbaz-Salehi 2015 pp. 564–608">{{cite journal | last=Acemoglu | first=Daron | last2=Ozdaglar | first2=Asuman | last3=Tahbaz-Salehi | first3=Alireza | title=Systemic Risk and Stability in Financial Networks | journal=American Economic Review | publisher=American Economic Association | volume=105 | issue=2 | year=2015 | issn=0002-8282 | doi=10.1257/aer.20130456 | pages=564–608| hdl=1721.1/100979 | hdl-access=free }}</ref><ref name="Elliott Golub Jackson 2014 pp. 3115–3153">{{cite journal | last=Elliott | first=Matthew | last2=Golub | first2=Benjamin | last3=Jackson | first3=Matthew O. | title=Financial Networks and Contagion | journal=American Economic Review | publisher=American Economic Association | volume=104 | issue=10 | year=2014 | issn=0002-8282 | doi=10.1257/aer.104.10.3115 | pages=3115–3153}}</ref>

Note however that systemic risk is not due to individual institutions per se, but due to the interconnections. For detailed models in economics and finance, see Elliott et al. (2014) and Acemoglu et al. (2015).

但请注意，系统性风险不是由于单个机构本身造成的，而是由于它们相互之间的联系。关于经济学和金融学的详细模型，请参阅艾略特 Elliott等人（2014）和阿西莫格鲁 Acemoglu等人（2015）的文章。<ref name="Acemoglu Ozdaglar Tahbaz-Salehi 2015 pp. 564–608">{{cite journal | last=Acemoglu | first=Daron | last2=Ozdaglar | first2=Asuman | last3=Tahbaz-Salehi | first3=Alireza | title=Systemic Risk and Stability in Financial Networks | journal=American Economic Review | publisher=American Economic Association | volume=105 | issue=2 | year=2015 | issn=0002-8282 | doi=10.1257/aer.20130456 | pages=564–608| hdl=1721.1/100979 | hdl-access=free }}</ref><ref name="Elliott Golub Jackson 2014 pp. 3115–3153">{{cite journal | last=Elliott | first=Matthew | last2=Golub | first2=Benjamin | last3=Jackson | first3=Matthew O. | title=Financial Networks and Contagion | journal=American Economic Review | publisher=American Economic Association | volume=104 | issue=10 | year=2014 | issn=0002-8282 | doi=10.1257/aer.104.10.3115 | pages=3115–3153}}</ref>

A related (though distinct) type of cascading failure in finance occurs in the stock market, exemplified by the [[2010 Flash Crash]].

A related (though distinct) type of cascading failure in finance occurs in the stock market, exemplified by the 2010 Flash Crash.

金融领域的一种相关的（但不同的）级联失效发生在股票市场，2010年的闪电崩盘就是一个例子。

For another framework to study and predict the effect of cascading failures in finance see<ref>{{cite journal|last1=Li|first1=W|last2=Kenett|first2=DY|last3=Yamasaki|first3=K|last4=Stanley|first4=HE|last5=Havlin|first5=S|title=Ranking the economic importance of countries and industries|journal=Journal of Network Theory in Finance|volume=3|pages=1–17|year=2017|issn=2055-7795|doi=10.21314/JNTF.2017.031|arxiv=1408.0443}}</ref><ref name="HuangVodenska2013"/>

For another framework to study and predict the effect of cascading failures in finance see

有关研究和预测金融连锁反应影响的另一个框架，请参见<ref>{{cite journal|last1=Li|first1=W|last2=Kenett|first2=DY|last3=Yamasaki|first3=K|last4=Stanley|first4=HE|last5=Havlin|first5=S|title=Ranking the economic importance of countries and industries|journal=Journal of Network Theory in Finance|volume=3|pages=1–17|year=2017|issn=2055-7795|doi=10.21314/JNTF.2017.031|arxiv=1408.0443}}</ref><ref name="HuangVodenska2013"/>

== Interdependent cascading failures ==
相互依赖的级联失效

[[File:Interdependent_relationship_among_different_infrastructures.tif|thumb|right|Fig. 1: Illustration of the interdependent relationship among different infrastructures]]

Fig. 1: Illustration of the interdependent relationship among different infrastructures

图1: 不同基础设施之间的相互依存关系的说明

[[File:Schematic_demonstration_of_first-_and_second-order_percolation_transitions.tif|thumb|right|Fig. 2. Schematic demonstration of first- and second-order percolation transitions. In the second-order case, the giant component is continuously approaching zero at the percolation threshold p = p_c. In the first-order case, the giant component approaches zero discontinuously]]

Fig. 2. Schematic demonstration of first- and second-order percolation transitions. In the second-order case, the giant component is continuously approaching zero at the percolation threshold p = p_c. In the first-order case, the giant component approaches zero discontinuously

图2：一阶和二阶渗流过渡的示意图。在二阶情况下，'''最大连通分支giant component'''在渗流阈值p=p_c时不断接近零。在一阶情况下，最大连通分支不连续地接近零。

Diverse [[infrastructure]]s such as [[water supply]], [[transportation]], fuel and [[power station]]s are coupled together and depend on each other for functioning, see Fig. 1. Owing to this coupling, interdependent networks are extremely sensitive to random failures, and in particular to [[Targeted threat|targeted attacks]], such that a failure of a small fraction of nodes in one network can triger an iterative cascade of failures in several interdependent networks.<ref>{{cite web|title=Report of the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack|url=http://empcommission.org/docs/A2473-EMP_Commission-7MB.pdf}}</ref><ref>{{Cite journal|last=Rinaldi|first=S.M.|last2=Peerenboom|first2=J.P.|last3=Kelly|first3=T.K.|date=2001|title=Identifying, understanding, and analyzing critical infrastructure interdependencies|url=|journal= IEEE Control Systems Magazine|volume=21|pages=11–25|via=}}</ref> [[Power outage|Electrical blackouts]] frequently result from a cascade of failures between interdependent networks, and the problem has been dramatically exemplified by the several large-scale blackouts that have occurred in recent years. Blackouts are a fascinating demonstration of the important role played by the dependencies between networks. For example, the [[2003 Italy blackout]] resulted in a widespread failure of the [[Rail transport|railway network]], [[Health system|health care systems]], and [[financial services]] and, in addition, severely influenced the [[telecommunication network]]s. The partial failure of the communication system in turn further impaired the [[electrical grid]] management system, thus producing a positive feedback on the power grid.<ref>{{cite journal|last=V. Rosato |first=Issacharoff, L., Tiriticco, F., Meloni, S., Porcellinis, S.D., & Setola, R. |title=Modelling interdependent infrastructures using interacting dynamical models |journal=International Journal of Critical Infrastructures |year=2008 |volume=4 |pages=63–79 |doi=10.1504/IJCIS.2008.016092 }}</ref> This example emphasizes how inter-dependence can significantly magnify the damage in an interacting network system. A framework to study the cascading failures between coupled networks based on percolation theory was developed recently.<ref>{{cite journal|last=S. V. Buldyrev|first=R. Parshani, G. Paul, H. E. Stanley, S. Havlin|title=Catastrophic cascade of failures in interdependent networks|journal=Nature|year=2010|volume=464|pages=1025–8|doi=10.1038/nature08932|url=http://havlin.biu.ac.il/Publications.php?keyword=Catastrophic+cascade+of+failures+in+interdependent+networks&year=*&match=all|pmid=20393559|issue=7291|arxiv=1012.0206|bibcode=2010Natur.464.1025B}}</ref> The cascading failures can lead to abrupt collapse compare to percolation in a single network where the breakdown of the network is continuous, see Fig. 2. Cascading failures in spatially embedded systems have been shown to lead to extreme vulnerability.<ref name="BashanBerezin2013">{{cite journal|last1=Bashan|first1=Amir|last2=Berezin|first2=Yehiel|last3=Buldyrev|first3=Sergey V.|last4=Havlin|first4=Shlomo|title=The extreme vulnerability of interdependent spatially embedded networks|journal=Nature Physics|year=2013|issn=1745-2473|doi=10.1038/nphys2727|volume=9|issue=10|pages=667–672|arxiv=1206.2062|bibcode=2013NatPh...9..667B}}</ref> For the dynamic process of cascading failures see ref.<ref>{{Cite journal|last=Zhou|first=D.|last2=Bashan|first2=A.|last3=Cohen|first3=R.|last4=Berezin|first4=Y.|last5=Shnerb|first5=N.|last6=Havlin|first6=S.|date=2014|title=Simultaneous first- and second-order percolation transitions in interdependent networks|url=|journal=Phys. Rev. E|volume=90|issue=1|pages=012803|bibcode=2014PhRvE..90a2803Z|doi=10.1103/PhysRevE.90.012803|pmid=25122338|arxiv=1211.2330}}</ref> A model for repairing failures in order to avoid cascading failures was developed by Di Muro et al.<ref>{{Cite journal|last=Di Muro|first=M. A.|last2=La Rocca|first2=C. E.|last3=Stanley|first3=H. E.|last4=Havlin|first4=S.|last5=Braunstein|first5=L. A.|date=2016-03-09|title=Recovery of Interdependent Networks|journal=Scientific Reports|language=En|volume=6|issue=1|pages=22834|doi=10.1038/srep22834|pmid=26956773|pmc=4783785|issn=2045-2322|arxiv=1512.02555|bibcode=2016NatSR...622834D}}</ref>

Diverse infrastructures such as water supply, transportation, fuel and power stations are coupled together and depend on each other for functioning, see Fig. 1. Owing to this coupling, interdependent networks are extremely sensitive to random failures, and in particular to targeted attacks, such that a failure of a small fraction of nodes in one network can triger an iterative cascade of failures in several interdependent networks. Electrical blackouts frequently result from a cascade of failures between interdependent networks, and the problem has been dramatically exemplified by the several large-scale blackouts that have occurred in recent years. Blackouts are a fascinating demonstration of the important role played by the dependencies between networks. For example, the 2003 Italy blackout resulted in a widespread failure of the railway network, health care systems, and financial services and, in addition, severely influenced the telecommunication networks. The partial failure of the communication system in turn further impaired the electrical grid management system, thus producing a positive feedback on the power grid. This example emphasizes how inter-dependence can significantly magnify the damage in an interacting network system. A framework to study the cascading failures between coupled networks based on percolation theory was developed recently. The cascading failures can lead to abrupt collapse compare to percolation in a single network where the breakdown of the network is continuous, see Fig. 2. Cascading failures in spatially embedded systems have been shown to lead to extreme vulnerability. For the dynamic process of cascading failures see ref. A model for repairing failures in order to avoid cascading failures was developed by Di Muro et al.

诸如供水、运输、燃料和发电站等多种基础设施都是耦合在一起的，并相互依赖着运行，见图1。由于这种耦合，相互依存的网络对随机故障，特别是对有针对性的攻击极为敏感，因此，一个网络中一小部分节点的故障就会导致几个相互依存的网络中出现一连串的故障。<ref>{{cite web|title=Report of the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack|url=http://empcommission.org/docs/A2473-EMP_Commission-7MB.pdf}}</ref><ref>{{Cite journal|last=Rinaldi|first=S.M.|last2=Peerenboom|first2=J.P.|last3=Kelly|first3=T.K.|date=2001|title=Identifying, understanding, and analyzing critical infrastructure interdependencies|url=|journal= IEEE Control Systems Magazine|volume=21|pages=11–25|via=}}</ref> 电气停电经常是由相互依赖的网络之间的故障级联造成的，近年来发生的几次大规模停电事件就极大地说明了这个问题。停电是网络之间的依存关系所起的重要作用的一个很好的证明。例如，2003年意大利大停电导致铁路网、医疗系统、金融服务大面积瘫痪，此外，还严重影响了电信网络。通信系统的部分故障又进一步损害了电网管理系统，从而对电网产生了正反馈。<ref>{{cite journal|last=V. Rosato |first=Issacharoff, L., Tiriticco, F., Meloni, S., Porcellinis, S.D., & Setola, R. |title=Modelling interdependent infrastructures using interacting dynamical models |journal=International Journal of Critical Infrastructures |year=2008 |volume=4 |pages=63–79 |doi=10.1504/IJCIS.2008.016092 }}</ref>这个例子强调了在一个相互影响的网络系统中，相互依赖是如何显著放大损害的。基于''' 渗流理论 Percolation Theory'''，最近发展了一个研究耦合网络之间级联失效的框架。<ref>{{cite journal|last=S. V. Buldyrev|first=R. Parshani, G. Paul, H. E. Stanley, S. Havlin|title=Catastrophic cascade of failures in interdependent networks|journal=Nature|year=2010|volume=464|pages=1025–8|doi=10.1038/nature08932|url=http://havlin.biu.ac.il/Publications.php?keyword=Catastrophic+cascade+of+failures+in+interdependent+networks&year=*&match=all|pmid=20393559|issue=7291|arxiv=1012.0206|bibcode=2010Natur.464.1025B}}</ref> 与连续崩溃的单一网络的渗流相比，级联失效会导致网络的突然崩溃，见图2。空间嵌入式系统中的级联失效已经被证明会导致系统特别脆弱。<ref name="BashanBerezin2013">{{cite journal|last1=Bashan|first1=Amir|last2=Berezin|first2=Yehiel|last3=Buldyrev|first3=Sergey V.|last4=Havlin|first4=Shlomo|title=The extreme vulnerability of interdependent spatially embedded networks|journal=Nature Physics|year=2013|issn=1745-2473|doi=10.1038/nphys2727|volume=9|issue=10|pages=667–672|arxiv=1206.2062|bibcode=2013NatPh...9..667B}}</ref>关于级联失效的动态过程见参考文献。<ref>{{Cite journal|last=Zhou|first=D.|last2=Bashan|first2=A.|last3=Cohen|first3=R.|last4=Berezin|first4=Y.|last5=Shnerb|first5=N.|last6=Havlin|first6=S.|date=2014|title=Simultaneous first- and second-order percolation transitions in interdependent networks|url=|journal=Phys. Rev. E|volume=90|issue=1|pages=012803|bibcode=2014PhRvE..90a2803Z|doi=10.1103/PhysRevE.90.012803|pmid=25122338|arxiv=1211.2330}}</ref>迪•姆洛 Di Muro等人开发了一个修复故障的模型，以避免级联失效。<ref>{{Cite journal|last=Di Muro|first=M. A.|last2=La Rocca|first2=C. E.|last3=Stanley|first3=H. E.|last4=Havlin|first4=S.|last5=Braunstein|first5=L. A.|date=2016-03-09|title=Recovery of Interdependent Networks|journal=Scientific Reports|language=En|volume=6|issue=1|pages=22834|doi=10.1038/srep22834|pmid=26956773|pmc=4783785|issn=2045-2322|arxiv=1512.02555|bibcode=2016NatSR...622834D}}</ref>

Furthermore, it was shown that such systems when embedded in space are extremely vulnerable to localized attacks or failures. Above a critical radius of damage, the failure may spread to the entire system.<ref>{{Cite journal|last=Berezin|first=Yehiel|last2=Bashan|first2=Amir|last3=Danziger|first3=Michael M.|last4=Li|first4=Daqing|last5=Havlin|first5=Shlomo|date=2015-03-11|title=Localized attacks on spatially embedded networks with dependencies|journal=Scientific Reports|language=en|volume=5|issue=1|pages=8934|doi=10.1038/srep08934|pmid=25757572|pmc=4355725|issn=2045-2322|bibcode=2015NatSR...5E8934B}}</ref>

Furthermore, it was shown that such systems when embedded in space are extremely vulnerable to localized attacks or failures. Above a critical radius of damage, the failure may spread to the entire system.

此外，研究表明，当这种系统嵌入空间时，极易受到局部攻击或故障的影响。超过临界损伤半径，故障可能扩散到整个系统。<ref>{{Cite journal|last=Berezin|first=Yehiel|last2=Bashan|first2=Amir|last3=Danziger|first3=Michael M.|last4=Li|first4=Daqing|last5=Havlin|first5=Shlomo|date=2015-03-11|title=Localized attacks on spatially embedded networks with dependencies|journal=Scientific Reports|language=en|volume=5|issue=1|pages=8934|doi=10.1038/srep08934|pmid=25757572|pmc=4355725|issn=2045-2322|bibcode=2015NatSR...5E8934B}}</ref>

== Model for overload cascading failures ==
过载级联失效模型

A model for cascading failures due to overload propagation is the Motter–Lai model.<ref>{{Cite journal|last=Motter|first=A. E.|last2=Lai|first2=Y. C.|date=2002|title=Cascade-based attacks on complex networks|url=|journal=Phys. Rev. E|volume=66|issue=6 Pt 2|pages=065102|doi=10.1103/PhysRevE.66.065102|pmid=12513335|bibcode=2002PhRvE..66f5102M|arxiv=cond-mat/0301086}}</ref> The tempo-spatial propagation of such failures have been studied by Jichang Zhao et al.<ref>{{Cite journal|last=Zhao|first=J.|last2=Li|first2=D.|last3=Sanhedrai|first3=H.|last4=Cohen|first4=R.|last5=Havlin|first5=S.|date=2016|title=Spatio-temporal propagation of cascading overload failures in spatially embedded networks|url=|journal=Nature Communications|volume=7|pages=10094|bibcode=2016NatCo...710094Z|doi=10.1038/ncomms10094|pmid=26754065|pmc=4729926}}</ref>

A model for cascading failures due to overload propagation is the Motter–Lai model. The tempo-spatial propagation of such failures have been studied by Jichang Zhao et al.

过载传播导致的级联失效的模型是Motter-Lai模型。赵继昌 Jichang Zhao等人对这种故障的时空传播进行了研究。

== See also ==
请参阅

{{div col}}

* [[Power outage|Blackouts]]
*[[停电|停电]]。

* [[Brittle system]]
* [[ 脆性系统 Brittle system]]

* [[Butterfly effect]]
* [[ 蝴蝶效应 Butterfly effect]]

* [[Byzantine failure]]
* [[拜占庭故障 Byzantine failure]]

* [[Cascading rollback]]
* [[ 级联回滚 Cascading rollback]]

* [[Chain reaction]]
* [[ 连锁反应 Chain reaction]]

* [[Chaos theory]]
* [[ 混沌理论 Chaos theory]]

* [[Cache stampede]]
* [[ 缓存雪崩 Cache stampede]]

* [[Congestion collapse]]
* [[拥塞崩溃]]

* [[Domino effect]]
* [[ 多米诺效应 Domino effect]]

* [[For Want of a Nail (proverb)]]
* [[因小失大（谚语）]]

* [[Interdependent networks]]
* [[相互依赖的网络]]

* [[Kessler Syndrome]]
* [[ 凯斯勒现象 Kessler Syndrome]]

* [[Percolation theory]]
* [[渗流理论]]

* [[Progressive collapse]]
* [[ 连续性倒塌 Progressive collapse]]

* [[Virtuous circle and vicious circle]]
*[[良性循环和恶性循环]]

* [[Wicked problem]]
* [[ 抗解问题 Wicked problem]]

{{div col end}}

== References ==
参考

{{reflist}}

== Further reading ==
进一步阅读

* {{cite web
|url=http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf
|title=Comparison of defense strategies for cascade breakdown on SF networks with degree correlations
|author=Toshiyuki Miyazaki
|date=1 March 2005
|url-status=dead
|archiveurl=https://web.archive.org/web/20090220024018/http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf
|archivedate=2009-02-20
}}

* {{cite web
|url=http://redmondmag.com/columns/print.asp?EditorialsID=1000
|title=(In)Secure Shell?
|accessdate=2007-09-08
|author=Russ Cooper
|date=1 June 2005
|publisher=RedmondMag.com
|archiveurl=https://web.archive.org/web/20070928164525/http://redmondmag.com/columns/print.asp?EditorialsID=1000
|archivedate=2007-09-28
|url-status=dead
}}

* {{cite web
|url=http://www.chds.us/?research/software&d=list
|title=Cascade Net (simulation program)
|accessdate=2007-09-08
|author=US Department of Homeland Security
|date=5 February 2007
|publisher=Center for Homeland Defense and Security
|url-status=dead
|archiveurl=https://web.archive.org/web/20081228044520/http://www.chds.us/?research%2Fsoftware&d=list
|archivedate=2008-12-28
}}

== External links ==

* [https://web.archive.org/web/20060827050151/http://www.windows.ucar.edu/spaceweather/blackout.html Space Weather: Blackout — Massive Power Grid Failure]

* [https://web.archive.org/web/20071022110507/http://vlab.infotech.monash.edu.au/simulations/networks/cascading-failure/ Cascading failure demo applet] (Monash University's Virtual Lab)

* A. E. Motter and Y.-C. Lai, [http://chaos1.la.asu.edu/~yclai/papers/PRE_02_ML_3.pdf ''Cascade-based attacks on complex networks,''] Physical Review E (Rapid Communications) 66, 065102 (2002).

* P. Crucitti, V. Latora and M. Marchiori, [https://pdfs.semanticscholar.org/aeda/97ccce03a5979dd4196fb7544ee0dc546f18.pdf ''Model for cascading failures in complex networks,''] Physical Review E (Rapid Communications) 69, 045104 (2004).

* [https://web.archive.org/web/20040704132003/http://www.epri.com/programHigh.asp?objid=261741 Protection Strategies for Cascading Grid Failures — A Shortcut Approach]

* I. Dobson, B. A. Carreras, and D. E. Newman, [https://web.archive.org/web/20060222073252/http://eceserv0.ece.wisc.edu/~dobson/PAPERS/dobsonPEIS05.pdf preprint] A loading-dependent model of probabilistic cascading failure, Probability in the Engineering and Informational Sciences, vol. 19, no. 1, January 2005, pp. 15–32.

* [https://www.pbs.org/wgbh/nova/transcripts/3105_aircrash.html Nova: Crash of Flight 111] on September 2, 1998. [[Swissair Flight 111]] flying from New York to Geneva slammed into the Atlantic Ocean off the coast of Nova Scotia with 229 people aboard. Originally believed a terrorist act. After $39 million investigation, insurance settlement of $1.5 billion and more than four years, investigators unravel the puzzle: cascading failure. What is the legacy of Swissair 111? "We have a window into the internal structure of design, checks and balances, protection, and safety." -David Evans, Editor-in-Chief of Air Safety Week.

* PhysicsWeb story: [http://physicsweb.org/articles/news/5/11/9 Accident grounds neutrino lab]

* [http://necsi.edu/affiliates/braha/StructureandDynamics.htm The Structure and Dynamics of Large Scale Organizational Networks (Dan Braha, New England Complex Systems Institute)]

*From Single Network to Network of Networks http://havlin.biu.ac.il/Pdf/Bremen070715a.pdf

{{Electricity delivery}}

[[Category:Failure]]

Category:Failure

类别: 故障

[[Category:Reliability engineering]]

Category:Reliability engineering

类别: 可靠性工程

[[Category:Electric power transmission]]

Category:Electric power transmission

类别: 输电系统

[[Category:Systemic risk]]

Category:Systemic risk

类别: 系统性风险

[[Category:Systems science]]

Category:Systems science

类别: 系统科学

<noinclude>

This page was moved from [[wikipedia:en:Cascading failure]]. Its edit history can be viewed at [[级联失效/edithistory]]</noinclude>

[[Category:待整理页面]]

级联失效

2020-12-04T07:10:31Z

WildBoar：

本词条由11初步翻译，已由WildBoar完成审校

{{short description|System of interconnected parts in which the failure of one or few parts can trigger the failure of others}}

[[Image:Networkfailure.gif|thumb|right|An animation demonstrating how a single failure may result in other failures throughout a network.]]

[[Image:Networkfailure.gif|thumb|right|演示单个故障如何导致整个网络中其他故障的动画]]

An animation demonstrating how a single failure may result in other failures throughout a network.

演示单个故障如何导致整个网络中其他故障的动画。

A cascading failure is a process in a system of [[interconnection|interconnected]] parts in which the failure of one or few parts can trigger the failure of other parts and so on. Such a failure may happen in many types of systems, including power transmission, computer networking, finance, transportation systems, organisms, the human body, and ecosystems.

A cascading failure is a process in a system of interconnected parts in which the failure of one or few parts can trigger the failure of other parts and so on. Such a failure may happen in many types of systems, including power transmission, computer networking, finance, transportation systems, organisms, the human body, and ecosystems.

在一个部件相互连接的系统中，一个或几个部件的故障会引发其他部件的故障的过程就是''' 级联失效 Cascading Failure'''（也可译为级联故障）。这种故障可能发生在许多类型的系统中，包括电力输送、计算机网络、金融、交通系统、生物体、人体和生态系统。

Cascading failures may occur when one part of the system fails. When this happens, other parts must then compensate for the failed component. This in turn overloads these nodes, causing them to fail as well, prompting additional nodes to fail one after another.

Cascading failures may occur when one part of the system fails. When this happens, other parts must then compensate for the failed component. This in turn overloads these nodes, causing them to fail as well, prompting additional nodes to fail one after another.

当系统的一部分发生故障时，可能会发生级联失效。当这种情况发生时，其他部分必须对发生故障的部分进行补偿，这反过来又会使这些节点超载，使它们也发生故障，导致更多的节点相继发生故障。

== In power transmission ==
在电力输送中

Cascading failure is common in [[power grid]]s when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in [[high voltage]] systems, where a [[single point of failure]] (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

Cascading failure is common in power grids when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in high voltage systems, where a single point of failure (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

级联失效在电网中很常见，当其中一个元件(完全或部分)发生故障并将其负荷转移到系统中附近的元件时，就会推动那些附近的元件超出其容量，从而过载，并将其负荷转移到其他元件上。级联失效在高压系统中也很常见，在一个满载或轻度过载的系统中，一个''' 单点故障 Single Point of Failure (SPF)'''会导致系统所有节点突然出现尖峰。这种''' 浪涌电流 Surge Current'''可能会导致已经过载的节点发生故障，引发更多过载，从而在很短的时间内使整个系统瘫痪。

This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer.

This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer.

这个故障过程就像池塘上的涟漪一样，在系统的各个元件之间蔓延，直到系统中的所有元件都受到损害和/或系统在功能上与负载源断开。例如，在某些情况下，一个大型电网可能因为单个变压器的故障而崩溃。

Monitoring the operation of a system, in [[real-time computing|real-time]], and judicious disconnection of parts can help stop a cascade. Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures.<ref name="chao">{{cite arXiv |last1=Zhai |first1=Chao |title=Modeling and Identification of Worst-Case Cascading Failures in Power Systems |eprint=1703.05232 |class=cs.SY |year=2017}}</ref>

Monitoring the operation of a system, in real-time, and judicious disconnection of parts can help stop a cascade. Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures.

实时监测系统的运行情况，并明智地断开部件的连接，有助于阻止级联。另一种常见的技术是通过计算机模拟可能发生的故障来计算系统的安全边际，确定安全运行水平，在此水平之下，计算出的任何一种情况都不会引起级联失效，并确定网络中最有可能引起级联失效的部分。<ref name="chao">{{cite arXiv |last1=Zhai |first1=Chao |title=Modeling and Identification of Worst-Case Cascading Failures in Power Systems |eprint=1703.05232 |class=cs.SY |year=2017}}</ref>

One of the primary problems with preventing electrical grid failures is that the speed of the control signal is no faster than the speed of the propagating power overload, i.e. since both the control signal and the electrical power are moving at the same speed, it is not possible to isolate the outage by sending a warning ahead to isolate the element.

One of the primary problems with preventing electrical grid failures is that the speed of the control signal is no faster than the speed of the propagating power overload, i.e. since both the control signal and the electrical power are moving at the same speed, it is not possible to isolate the outage by sending a warning ahead to isolate the element.

防止电网故障的主要困难之一是控制信号的速度比传播电力过载的速度慢，即由于控制信号和电力都以同样的速度运动，所以无法通过提前发出警告来隔离元件从而隔离故障。

The question if power grid failures are correlated have been studied in Daqing Li et al.<ref>{{Cite journal|last=Daqing|first=Li|last2=Yinan|first2=Jiang|last3=Rui|first3=Kang|last4=Havlin|first4=Shlomo|date=2014-06-20|title=Spatial correlation analysis of cascading failures: Congestions and Blackouts|journal=Scientific Reports|language=En|volume=4|issue=1|pages=5381|doi=10.1038/srep05381|pmid=24946927|pmc=4064325|issn=2045-2322|bibcode=2014NatSR...4E5381D}}</ref> as well as by Paul DH Hines et al.<ref>{{Cite journal|last=Hines|first=Paul D. H.|last2=Dobson|first2=Ian|last3=Rezaei|first3=Pooya|date=2016|title=Cascading Power Outages Propagate Locally in an Influence Graph that is not the Actual Grid Topology|arxiv=1508.01775|journal=IEEE Transactions on Power Systems|pages=1|doi=10.1109/TPWRS.2016.2578259|issn=0885-8950}}</ref>

The question if power grid failures are correlated have been studied in Daqing Li et al. as well as by Paul DH Hines et al.

电网故障是否具有相关性的问题，李大庆 Daqing Li等人以及保罗·DH·海恩斯 Paul DH Hines等人都有研究。

=== Examples ===
案例

Cascading failure caused the following [[power outage]]s:

Cascading failure caused the following power outages:

级联失效曾导致以下停电:

* [[Northeast blackout of 1965|Blackout in Northeast America in 1965]]
* [[1965年东北大停电|1965年美国东北大停电]]

* [[1999 Southern Brazil blackout|Blackout in Southern Brazil in 1999]]
* [[1999年巴西南部停电|1999年巴西南部停电]]

* [[Northeast blackout of 2003|Blackout in Northeast America in 2003]]
* [[2003年东北大停电|2003年美国东北大停电]]

* [[2003 Italy blackout|Blackout in Italy in 2003]]
* [[2003年意大利停电|2003年意大利停电]]

* [[2003 London blackout|Blackout in London in 2003]]
* [[2003年伦敦大停电|2003年伦敦大停电]]

* [[2006 European blackout|European Blackout in 2006]]
* [[2006年欧洲停电|2006年欧洲停电]]

* [[2012 northern India power grid failure|Blackout in Northern India in 2012]]
* [[2012年印度北部电网故障|2012年印度北部停电]]

* [[2016 South Australian blackout|Blackout in South Australia in 2016]]
* [[2016年南澳停电|2016年南澳停电]]

* [[2019 Argentina, Paraguay and Uruguay blackout|Blackout in southeast South America in 2019]]
* [[2019年阿根廷、巴拉圭和乌拉圭停电|2019年南美洲东南部停电]]

== In computer networks ==
在计算机网络中

Cascading failures can also occur in [[computer network]]s (such as the [[Internet]]) in which [[Network traffic control|network traffic]] is severely impaired or halted to or between larger sections of the network, caused by failing or disconnected hardware or software. In this context, the cascading failure is known by the term '''cascade failure'''. A cascade failure can affect large groups of people and systems.

Cascading failures can also occur in computer networks (such as the Internet) in which network traffic is severely impaired or halted to or between larger sections of the network, caused by failing or disconnected hardware or software. In this context, the cascading failure is known by the term cascade failure. A cascade failure can affect large groups of people and systems.

级联失效也可能发生在计算机网络(如因特网)中，由于硬件或软件的故障或断开，导致网络中较大部分的网络通信严重受损或停止。在这种情况下，级联失效被称为术语 “cascade failure”。级联失效会影响到大批人员和系统。

The cause of a cascade failure is usually the overloading of a single, crucial [[Router (computing)|router]] or node, which causes the node to go down, even briefly. It can also be caused by taking a node down for maintenance or upgrades. In either case, traffic is [[routing|routed]] to or through another (alternative) path. This alternative path, as a result, becomes overloaded, causing it to go down, and so on. It will also affect systems which depend on the node for regular operation.

The cause of a cascade failure is usually the overloading of a single, crucial router or node, which causes the node to go down, even briefly. It can also be caused by taking a node down for maintenance or upgrades. In either case, traffic is routed to or through another (alternative) path. This alternative path, as a result, becomes overloaded, causing it to go down, and so on. It will also affect systems which depend on the node for regular operation.

级联失效的原因通常是一个单个关键的路由器或节点的超载，导致节点宕机即使是短暂地宕机。它也可能是由于为了维护或升级而关闭一个节点引起的。在这两种情况下，流量都被路由到达或通过另一条(替代)路径。结果，这条替代路径变得过载，导致宕机，等等。它还会影响依赖该节点正常运行的系统。

=== Symptoms ===
症状

The symptoms of a cascade failure include: [[packet loss]] and high network [[lag|latency]], not just to single systems, but to whole sections of a network or the internet. The high latency and packet loss is caused by the nodes that fail to operate due to [[congestion collapse]], which causes them to still be present in the network but without much or any useful communication going through them. As a result, routes can still be considered valid, without them actually providing communication.

The symptoms of a cascade failure include: packet loss and high network latency, not just to single systems, but to whole sections of a network or the internet. The high latency and packet loss is caused by the nodes that fail to operate due to congestion collapse, which causes them to still be present in the network but without much or any useful communication going through them. As a result, routes can still be considered valid, without them actually providing communication.

级联失效的症状包括: 数据包丢失和高网络延迟，不仅仅是对单个系统，而是对整个网络或互联网。高延迟和数包丢失是由于网络 拥塞崩溃 congestion collapse导致节点无法正常运行，这使得数据仍然存在于网络中，但是没有太多或任何有用的通道来传输它们。因此，路由仍然可被认为是有效的，而实际上它们并没有提供通信。

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）“级联失效的症状”中的症状是不是可以思考换一下词语印象中症状一般形容人换成“表现”或其他是否更好

If enough routes go down because of a cascade failure, a complete section of the network or internet can become unreachable. Although undesired, this can help speed up the recovery from this failure as connections will time out, and other nodes will give up trying to establish connections to the section(s) that have become cut off, decreasing load on the involved nodes.

If enough routes go down because of a cascade failure, a complete section of the network or internet can become unreachable. Although undesired, this can help speed up the recovery from this failure as connections will time out, and other nodes will give up trying to establish connections to the section(s) that have become cut off, decreasing load on the involved nodes.

如果有够多的路由因为级联失效而中断，网络或互联网的一个完整部分就会无法访问。尽管我们不希望出现这种情况，但这有助于加快从故障中恢复，因为连接会超时，其他节点会放弃尝试与被切断的部分建立连接，从而减少相关节点的负载。

A common occurrence during a cascade failure is a '''walking failure''', where sections go down, causing the next section to fail, after which the first section comes back up. This '''ripple''' can make several passes through the same sections or connecting nodes before stability is restored.

A common occurrence during a cascade failure is a walking failure, where sections go down, causing the next section to fail, after which the first section comes back up. This ripple can make several passes through the same sections or connecting nodes before stability is restored.

在级联失效中，一个常见的现象是行走故障，即各段下行，导致下一段故障，之后第一段回升。在恢复稳定之前，这种波纹可能会在相同的区段或连接节点上进行多次传递。

=== History ===
历史

Cascade failures are a relatively recent development, with the massive increase in traffic and the high interconnectivity between systems and networks. The term was first applied in this context in the late 1990s by a Dutch IT professional and has slowly become a relatively common term for this kind of large-scale failure.{{Citation needed|date=January 2009}}

Cascade failures are a relatively recent development, with the massive increase in traffic and the high interconnectivity between systems and networks. The term was first applied in this context in the late 1990s by a Dutch IT professional and has slowly become a relatively common term for this kind of large-scale failure.

级联失效是一个相对较新的发展，随着流量的大量增加和系统与网络之间的高度互连性而出现。这个术语最早是在90年代末由一位荷兰的IT专业人员在此情况下使用的，后来慢慢成为这种大规模故障的一个比较常见的术语。

=== Example ===
案例

Network failures typically start when a single network node fails. Initially, the traffic that would normally go through the node is stopped. Systems and users get errors about not being able to reach hosts. Usually, the redundant systems of an ISP respond very quickly, choosing another path through a different backbone. The routing path through this alternative route is longer, with more [[Hop (telecommunications)|hops]] and subsequently going through more systems that normally do not process the amount of traffic suddenly offered.

Network failures typically start when a single network node fails. Initially, the traffic that would normally go through the node is stopped. Systems and users get errors about not being able to reach hosts. Usually, the redundant systems of an ISP respond very quickly, choosing another path through a different backbone. The routing path through this alternative route is longer, with more hops and subsequently going through more systems that normally do not process the amount of traffic suddenly offered.

网络故障通常始于单个网络节点故障。首先，正常情况下会经过该节点的流量被停止。系统和用户会得到流量无法到达主机的错误。通常，ISP的冗余系统会很快做出反应，选择另一条通过不同骨干网的路径。通过这条替代路径的路由路径更长，跳数更多，随后要经过更多的系统，而这些系统通常不会处理突然提供的流量。

This can cause one or more systems along the alternative route to go down, creating similar problems of their own.

This can cause one or more systems along the alternative route to go down, creating similar problems of their own.

这可能会导致替代路线上的一个或多个系统瘫痪，造成类似故障系统的问题。

Also, related systems are affected in this case. As an example, [[Domain name system|DNS]] resolution might fail and what would normally cause systems to be interconnected, might break connections that are not even directly involved in the actual systems that went down. This, in turn, may cause seemingly unrelated nodes to develop problems, that can cause another cascade failure all on its own.

Also, related systems are affected in this case. As an example, DNS resolution might fail and what would normally cause systems to be interconnected, might break connections that are not even directly involved in the actual systems that went down. This, in turn, may cause seemingly unrelated nodes to develop problems, that can cause another cascade failure all on its own.

此外，在这种情况下，相关系统也会受到影响。例如，DNS解析可能会失败，那些通常会造成系统互连的情况可能会破坏一些连接，这些连接甚至没有直接参与实际发生故障的系统。而这又可能导致看似不相关的节点出现问题，从而导致另一个级联失效的发生。

In December 2012, a partial loss (40%) of [[Gmail]] service occurred globally, for 18 minutes. This loss of service was caused by a routine update of load balancing software which contained faulty logic—in this case, the error was caused by logic using an [https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ inappropriate ''all'' instead of the more appropriate ''some''.] The cascading error was fixed by fully updating a single node in the network instead of partially updating all nodes at one time.

In December 2012, a partial loss (40%) of Gmail service occurred globally, for 18 minutes. This loss of service was caused by a routine update of load balancing software which contained faulty logic—in this case, the error was caused by logic using an [https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ inappropriate all instead of the more appropriate some.] The cascading error was fixed by fully updating a single node in the network instead of partially updating all nodes at one time.

2012年12月，Gmail服务在全球范围内出现了部分损失(40%)，持续了18分钟。这次服务损失是由包含错误逻辑的负载平衡软件的例行更新引起的——在这种情况下，该错误是由使用[https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ 不合适的all而不是更合适的some]的逻辑引起的。通过完全更新网络中的一个节点，而不是部分更新所有节点，修复了级联失效。
--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）“The cascading error”可以思考一下级联错误与级联失效是否一样

== Cascading structural failure ==
级联结构失效

Certain load-bearing structures with discrete structural components can be subject to the "zipper effect", where the failure of a single structural member increases the load on adjacent members. In the case of the [[Hyatt Regency walkway collapse]], a suspended walkway (which was already overstressed due to an error in construction) failed when a single vertical suspension rod failed, overloading the neighboring rods which failed sequentially (i.e. like a [[zipper]]). A bridge that can have such a failure is called fracture critical, and numerous bridge collapses have been caused by the failure of a single part. Properly designed structures use an adequate [[factor of safety]] and/or alternate load paths to prevent this type of mechanical cascade failure.<ref name="petroski">{{cite book| title=To Engineer Is Human: The Role of Failure in Structural Design| first=Henry| last=Petroski| year=1992| isbn=978-0-679-73416-1| publisher=Vintage| place=| url-access=registration| url=https://archive.org/details/toengineerishuma00petr}}</ref>

Certain load-bearing structures with discrete structural components can be subject to the "zipper effect", where the failure of a single structural member increases the load on adjacent members. In the case of the Hyatt Regency walkway collapse, a suspended walkway (which was already overstressed due to an error in construction) failed when a single vertical suspension rod failed, overloading the neighboring rods which failed sequentially (i.e. like a zipper). A bridge that can have such a failure is called fracture critical, and numerous bridge collapses have been caused by the failure of a single part. Properly designed structures use an adequate factor of safety and/or alternate load paths to prevent this type of mechanical cascade failure.

某些具有离散结构构件的承重结构可能会出现 "拉链效应"，即单个结构构件的失效会增加相邻构件的荷载。在凯悦酒店人行道坍塌事件中，当单根垂直悬杆失效时，悬空的人行道（由于施工中的错误，人行道已经过度受力）倒塌，使相邻的悬杆超载，相邻的悬杆依次失效（像拉链一样）。一座可能发生这种倒塌的桥梁被称为断裂临界桥梁，许多桥梁的坍塌都是由单一部件的故障引起的。正确设计的结构使用足够安全系数的和/或交替的荷载路径来防止这种类型的机械级联失效。<ref name="petroski">{{cite book| title=To Engineer Is Human: The Role of Failure in Structural Design| first=Henry| last=Petroski| year=1992| isbn=978-0-679-73416-1| publisher=Vintage| place=| url-access=registration| url=https://archive.org/details/toengineerishuma00petr}}</ref>

== Other examples ==
其他例子

=== Biology ===
生物

[[Biochemical cascade]]s exist in biology, where a small reaction can have system-wide implications. One negative example is [[ischemic cascade]], in which a small [[ischemia|ischemic]] attack releases [[toxin]]s which kill off far more cells than the initial damage, resulting in more toxins being released. Current research is to find a way to block this cascade in [[stroke]] patients to minimize the damage.

Biochemical cascades exist in biology, where a small reaction can have system-wide implications. One negative example is ischemic cascade, in which a small ischemic attack releases toxins which kill off far more cells than the initial damage, resulting in more toxins being released. Current research is to find a way to block this cascade in stroke patients to minimize the damage.

生物学中存在着生化级联，一个小的反应就会对整个系统产生影响。一个负面的例子是缺血性级联反应，在这种反应中，一个小的脑缺血发作释放出的毒素比最初的损伤杀死更多的细胞，导致更多的毒素被释放。目前的研究正在寻找一种方法来阻断中风患者的这种级联反应，以最大限度地减少损伤。

In the study of extinction, sometimes the extinction of one species will cause many other extinctions to happen. Such a species is known as a [[keystone species]].

In the study of extinction, sometimes the extinction of one species will cause many other extinctions to happen. Such a species is known as a keystone species.

在物种灭绝的研究中，有时一个物种的灭绝会导致许多其他物种的灭绝。这样的物种被称为 关键种 keystone species。

=== Electronics ===
电子学

Another example is the [[Cockcroft–Walton generator]], which can also experience cascade failures wherein one failed [[diode]] can result in all the diodes failing in a fraction of a second.

Another example is the Cockcroft–Walton generator, which can also experience cascade failures wherein one failed diode can result in all the diodes failing in a fraction of a second.

另一个例子是Cockcroft-Walton发电机，它也会发生级联失效，其中一个故障的二极管会导致所有二极管在顷刻间发生故障。

Yet another example of this effect in a scientific experiment was the [[Implosion (mechanical process)|implosion]] in 2001 of several thousand fragile glass photomultiplier tubes used in the [[Super-Kamiokande]] experiment, where the shock wave caused by the failure of a single detector appears to have triggered the implosion of the other detectors in a chain reaction.

Yet another example of this effect in a scientific experiment was the implosion in 2001 of several thousand fragile glass photomultiplier tubes used in the Super-Kamiokande experiment, where the shock wave caused by the failure of a single detector appears to have triggered the implosion of the other detectors in a chain reaction.

在科学实验中，这种效应的另一个例子是2001年用于超级神冈探测器实验中的几千支易碎的玻璃光电倍增管发生内爆，其中一个探测器的故障造成的冲击波似乎引发了其他探测器的内爆，形成了连锁反应。

=== Finance ===
金融

{{main|Systemic risk}} {{main|Cascades in financial networks}}
{{主要}系统性风险}} {{主要}金融网络中的级联}}}

In [[finance]], the risk of cascading failures of financial institutions is referred to as ''[[systemic risk]]:'' the failure of one financial institution may cause other financial institutions (its [[Counterparty|counterparties]]) to fail, cascading throughout the system.<ref name="HuangVodenska2013">{{cite journal|last1=Huang|first1=Xuqing|last2=Vodenska|first2=Irena|last3=Havlin|first3=Shlomo|last4=Stanley|first4=H. Eugene|title=Cascading Failures in Bi-partite Graphs: Model for Systemic Risk Propagation|journal=Scientific Reports|volume=3|pages=1219|year=2013|issn=2045-2322|doi=10.1038/srep01219|pmid=23386974|pmc=3564037|arxiv=1210.4973|bibcode=2013NatSR...3E1219H}}</ref>

In finance, the risk of cascading failures of financial institutions is referred to as systemic risk: the failure of one financial institution may cause other financial institutions (its counterparties) to fail, cascading throughout the system.

在金融领域，金融机构连锁倒闭的风险被称为系统性风险：一家金融机构的倒闭可能会引起其他金融机构（其交易对手）的倒闭，在整个系统中连锁倒闭。<ref name="HuangVodenska2013">{{cite journal|last1=Huang|first1=Xuqing|last2=Vodenska|first2=Irena|last3=Havlin|first3=Shlomo|last4=Stanley|first4=H. Eugene|title=Cascading Failures in Bi-partite Graphs: Model for Systemic Risk Propagation|journal=Scientific Reports|volume=3|pages=1219|year=2013|issn=2045-2322|doi=10.1038/srep01219|pmid=23386974|pmc=3564037|arxiv=1210.4973|bibcode=2013NatSR...3E1219H}}</ref>

Institutions that are believed to pose systemic risk are deemed either "[[too big to fail]]" (TBTF) or "too interconnected to fail" (TICTF), depending on why they appear to pose a threat.

Institutions that are believed to pose systemic risk are deemed either "too big to fail" (TBTF) or "too interconnected to fail" (TICTF), depending on why they appear to pose a threat.

那些被认为构成系统性风险的机构要么被视为“太大而不能倒”(TBTF) ，要么被视为“太相关而不能倒闭”(TICTF) ，这取决于它们为什么会构成威胁。

Note however that systemic risk is not due to individual institutions per se, but due to the interconnections. For detailed models in economics and finance, see Elliott et al. (2014) and Acemoglu et al. (2015).<ref name="Acemoglu Ozdaglar Tahbaz-Salehi 2015 pp. 564–608">{{cite journal | last=Acemoglu | first=Daron | last2=Ozdaglar | first2=Asuman | last3=Tahbaz-Salehi | first3=Alireza | title=Systemic Risk and Stability in Financial Networks | journal=American Economic Review | publisher=American Economic Association | volume=105 | issue=2 | year=2015 | issn=0002-8282 | doi=10.1257/aer.20130456 | pages=564–608| hdl=1721.1/100979 | hdl-access=free }}</ref><ref name="Elliott Golub Jackson 2014 pp. 3115–3153">{{cite journal | last=Elliott | first=Matthew | last2=Golub | first2=Benjamin | last3=Jackson | first3=Matthew O. | title=Financial Networks and Contagion | journal=American Economic Review | publisher=American Economic Association | volume=104 | issue=10 | year=2014 | issn=0002-8282 | doi=10.1257/aer.104.10.3115 | pages=3115–3153}}</ref>

Note however that systemic risk is not due to individual institutions per se, but due to the interconnections. For detailed models in economics and finance, see Elliott et al. (2014) and Acemoglu et al. (2015).

但请注意，系统性风险不是由于单个机构本身造成的，而是由于它们相互之间的联系。关于经济学和金融学的详细模型，请参阅艾略特 Elliott等人（2014）和阿西莫格鲁 Acemoglu等人（2015）的文章。<ref name="Acemoglu Ozdaglar Tahbaz-Salehi 2015 pp. 564–608">{{cite journal | last=Acemoglu | first=Daron | last2=Ozdaglar | first2=Asuman | last3=Tahbaz-Salehi | first3=Alireza | title=Systemic Risk and Stability in Financial Networks | journal=American Economic Review | publisher=American Economic Association | volume=105 | issue=2 | year=2015 | issn=0002-8282 | doi=10.1257/aer.20130456 | pages=564–608| hdl=1721.1/100979 | hdl-access=free }}</ref><ref name="Elliott Golub Jackson 2014 pp. 3115–3153">{{cite journal | last=Elliott | first=Matthew | last2=Golub | first2=Benjamin | last3=Jackson | first3=Matthew O. | title=Financial Networks and Contagion | journal=American Economic Review | publisher=American Economic Association | volume=104 | issue=10 | year=2014 | issn=0002-8282 | doi=10.1257/aer.104.10.3115 | pages=3115–3153}}</ref>

A related (though distinct) type of cascading failure in finance occurs in the stock market, exemplified by the [[2010 Flash Crash]].

A related (though distinct) type of cascading failure in finance occurs in the stock market, exemplified by the 2010 Flash Crash.

金融领域的一种相关的（但不同的）级联失效发生在股票市场，2010年的闪电崩盘就是一个例子。

For another framework to study and predict the effect of cascading failures in finance see<ref>{{cite journal|last1=Li|first1=W|last2=Kenett|first2=DY|last3=Yamasaki|first3=K|last4=Stanley|first4=HE|last5=Havlin|first5=S|title=Ranking the economic importance of countries and industries|journal=Journal of Network Theory in Finance|volume=3|pages=1–17|year=2017|issn=2055-7795|doi=10.21314/JNTF.2017.031|arxiv=1408.0443}}</ref><ref name="HuangVodenska2013"/>

For another framework to study and predict the effect of cascading failures in finance see

有关研究和预测金融连锁反应影响的另一个框架，请参见<ref>{{cite journal|last1=Li|first1=W|last2=Kenett|first2=DY|last3=Yamasaki|first3=K|last4=Stanley|first4=HE|last5=Havlin|first5=S|title=Ranking the economic importance of countries and industries|journal=Journal of Network Theory in Finance|volume=3|pages=1–17|year=2017|issn=2055-7795|doi=10.21314/JNTF.2017.031|arxiv=1408.0443}}</ref><ref name="HuangVodenska2013"/>

== Interdependent cascading failures ==
相互依赖的级联失效

[[File:Interdependent_relationship_among_different_infrastructures.tif|thumb|right|Fig. 1: Illustration of the interdependent relationship among different infrastructures]]

Fig. 1: Illustration of the interdependent relationship among different infrastructures

图1: 不同基础设施之间的相互依存关系的说明

[[File:Schematic_demonstration_of_first-_and_second-order_percolation_transitions.tif|thumb|right|Fig. 2. Schematic demonstration of first- and second-order percolation transitions. In the second-order case, the giant component is continuously approaching zero at the percolation threshold p = p_c. In the first-order case, the giant component approaches zero discontinuously]]

Fig. 2. Schematic demonstration of first- and second-order percolation transitions. In the second-order case, the giant component is continuously approaching zero at the percolation threshold p = p_c. In the first-order case, the giant component approaches zero discontinuously

图2：一阶和二阶渗流过渡的示意图。在二阶情况下，'''最大连通分支giant component'''在渗流阈值p=p_c时不断接近零。在一阶情况下，最大连通分支不连续地接近零。

Diverse [[infrastructure]]s such as [[water supply]], [[transportation]], fuel and [[power station]]s are coupled together and depend on each other for functioning, see Fig. 1. Owing to this coupling, interdependent networks are extremely sensitive to random failures, and in particular to [[Targeted threat|targeted attacks]], such that a failure of a small fraction of nodes in one network can triger an iterative cascade of failures in several interdependent networks.<ref>{{cite web|title=Report of the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack|url=http://empcommission.org/docs/A2473-EMP_Commission-7MB.pdf}}</ref><ref>{{Cite journal|last=Rinaldi|first=S.M.|last2=Peerenboom|first2=J.P.|last3=Kelly|first3=T.K.|date=2001|title=Identifying, understanding, and analyzing critical infrastructure interdependencies|url=|journal= IEEE Control Systems Magazine|volume=21|pages=11–25|via=}}</ref> [[Power outage|Electrical blackouts]] frequently result from a cascade of failures between interdependent networks, and the problem has been dramatically exemplified by the several large-scale blackouts that have occurred in recent years. Blackouts are a fascinating demonstration of the important role played by the dependencies between networks. For example, the [[2003 Italy blackout]] resulted in a widespread failure of the [[Rail transport|railway network]], [[Health system|health care systems]], and [[financial services]] and, in addition, severely influenced the [[telecommunication network]]s. The partial failure of the communication system in turn further impaired the [[electrical grid]] management system, thus producing a positive feedback on the power grid.<ref>{{cite journal|last=V. Rosato |first=Issacharoff, L., Tiriticco, F., Meloni, S., Porcellinis, S.D., & Setola, R. |title=Modelling interdependent infrastructures using interacting dynamical models |journal=International Journal of Critical Infrastructures |year=2008 |volume=4 |pages=63–79 |doi=10.1504/IJCIS.2008.016092 }}</ref> This example emphasizes how inter-dependence can significantly magnify the damage in an interacting network system. A framework to study the cascading failures between coupled networks based on percolation theory was developed recently.<ref>{{cite journal|last=S. V. Buldyrev|first=R. Parshani, G. Paul, H. E. Stanley, S. Havlin|title=Catastrophic cascade of failures in interdependent networks|journal=Nature|year=2010|volume=464|pages=1025–8|doi=10.1038/nature08932|url=http://havlin.biu.ac.il/Publications.php?keyword=Catastrophic+cascade+of+failures+in+interdependent+networks&year=*&match=all|pmid=20393559|issue=7291|arxiv=1012.0206|bibcode=2010Natur.464.1025B}}</ref> The cascading failures can lead to abrupt collapse compare to percolation in a single network where the breakdown of the network is continuous, see Fig. 2. Cascading failures in spatially embedded systems have been shown to lead to extreme vulnerability.<ref name="BashanBerezin2013">{{cite journal|last1=Bashan|first1=Amir|last2=Berezin|first2=Yehiel|last3=Buldyrev|first3=Sergey V.|last4=Havlin|first4=Shlomo|title=The extreme vulnerability of interdependent spatially embedded networks|journal=Nature Physics|year=2013|issn=1745-2473|doi=10.1038/nphys2727|volume=9|issue=10|pages=667–672|arxiv=1206.2062|bibcode=2013NatPh...9..667B}}</ref> For the dynamic process of cascading failures see ref.<ref>{{Cite journal|last=Zhou|first=D.|last2=Bashan|first2=A.|last3=Cohen|first3=R.|last4=Berezin|first4=Y.|last5=Shnerb|first5=N.|last6=Havlin|first6=S.|date=2014|title=Simultaneous first- and second-order percolation transitions in interdependent networks|url=|journal=Phys. Rev. E|volume=90|issue=1|pages=012803|bibcode=2014PhRvE..90a2803Z|doi=10.1103/PhysRevE.90.012803|pmid=25122338|arxiv=1211.2330}}</ref> A model for repairing failures in order to avoid cascading failures was developed by Di Muro et al.<ref>{{Cite journal|last=Di Muro|first=M. A.|last2=La Rocca|first2=C. E.|last3=Stanley|first3=H. E.|last4=Havlin|first4=S.|last5=Braunstein|first5=L. A.|date=2016-03-09|title=Recovery of Interdependent Networks|journal=Scientific Reports|language=En|volume=6|issue=1|pages=22834|doi=10.1038/srep22834|pmid=26956773|pmc=4783785|issn=2045-2322|arxiv=1512.02555|bibcode=2016NatSR...622834D}}</ref>

Diverse infrastructures such as water supply, transportation, fuel and power stations are coupled together and depend on each other for functioning, see Fig. 1. Owing to this coupling, interdependent networks are extremely sensitive to random failures, and in particular to targeted attacks, such that a failure of a small fraction of nodes in one network can triger an iterative cascade of failures in several interdependent networks. Electrical blackouts frequently result from a cascade of failures between interdependent networks, and the problem has been dramatically exemplified by the several large-scale blackouts that have occurred in recent years. Blackouts are a fascinating demonstration of the important role played by the dependencies between networks. For example, the 2003 Italy blackout resulted in a widespread failure of the railway network, health care systems, and financial services and, in addition, severely influenced the telecommunication networks. The partial failure of the communication system in turn further impaired the electrical grid management system, thus producing a positive feedback on the power grid. This example emphasizes how inter-dependence can significantly magnify the damage in an interacting network system. A framework to study the cascading failures between coupled networks based on percolation theory was developed recently. The cascading failures can lead to abrupt collapse compare to percolation in a single network where the breakdown of the network is continuous, see Fig. 2. Cascading failures in spatially embedded systems have been shown to lead to extreme vulnerability. For the dynamic process of cascading failures see ref. A model for repairing failures in order to avoid cascading failures was developed by Di Muro et al.

诸如供水、运输、燃料和发电站等多种基础设施都是耦合在一起的，并相互依赖着运行，见图1。由于这种耦合，相互依存的网络对随机故障，特别是对有针对性的攻击极为敏感，因此，一个网络中一小部分节点的故障就会导致几个相互依存的网络中出现一连串的故障。<ref>{{cite web|title=Report of the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack|url=http://empcommission.org/docs/A2473-EMP_Commission-7MB.pdf}}</ref><ref>{{Cite journal|last=Rinaldi|first=S.M.|last2=Peerenboom|first2=J.P.|last3=Kelly|first3=T.K.|date=2001|title=Identifying, understanding, and analyzing critical infrastructure interdependencies|url=|journal= IEEE Control Systems Magazine|volume=21|pages=11–25|via=}}</ref> 电气停电经常是由相互依赖的网络之间的故障级联造成的，近年来发生的几次大规模停电事件就极大地说明了这个问题。停电是网络之间的依存关系所起的重要作用的一个很好的证明。例如，2003年意大利大停电导致铁路网、医疗系统、金融服务大面积瘫痪，此外，还严重影响了电信网络。通信系统的部分故障又进一步损害了电网管理系统，从而对电网产生了正反馈。<ref>{{cite journal|last=V. Rosato |first=Issacharoff, L., Tiriticco, F., Meloni, S., Porcellinis, S.D., & Setola, R. |title=Modelling interdependent infrastructures using interacting dynamical models |journal=International Journal of Critical Infrastructures |year=2008 |volume=4 |pages=63–79 |doi=10.1504/IJCIS.2008.016092 }}</ref>这个例子强调了在一个相互影响的网络系统中，相互依赖是如何显著放大损害的。基于''' 渗流理论 Percolation Theory'''，最近发展了一个研究耦合网络之间级联失效的框架。<ref>{{cite journal|last=S. V. Buldyrev|first=R. Parshani, G. Paul, H. E. Stanley, S. Havlin|title=Catastrophic cascade of failures in interdependent networks|journal=Nature|year=2010|volume=464|pages=1025–8|doi=10.1038/nature08932|url=http://havlin.biu.ac.il/Publications.php?keyword=Catastrophic+cascade+of+failures+in+interdependent+networks&year=*&match=all|pmid=20393559|issue=7291|arxiv=1012.0206|bibcode=2010Natur.464.1025B}}</ref> 与连续崩溃的单一网络的渗流相比，级联失效会导致网络的突然崩溃，见图2。空间嵌入式系统中的级联失效已经被证明会导致系统特别脆弱。<ref name="BashanBerezin2013">{{cite journal|last1=Bashan|first1=Amir|last2=Berezin|first2=Yehiel|last3=Buldyrev|first3=Sergey V.|last4=Havlin|first4=Shlomo|title=The extreme vulnerability of interdependent spatially embedded networks|journal=Nature Physics|year=2013|issn=1745-2473|doi=10.1038/nphys2727|volume=9|issue=10|pages=667–672|arxiv=1206.2062|bibcode=2013NatPh...9..667B}}</ref>关于级联失效的动态过程见参考文献。<ref>{{Cite journal|last=Zhou|first=D.|last2=Bashan|first2=A.|last3=Cohen|first3=R.|last4=Berezin|first4=Y.|last5=Shnerb|first5=N.|last6=Havlin|first6=S.|date=2014|title=Simultaneous first- and second-order percolation transitions in interdependent networks|url=|journal=Phys. Rev. E|volume=90|issue=1|pages=012803|bibcode=2014PhRvE..90a2803Z|doi=10.1103/PhysRevE.90.012803|pmid=25122338|arxiv=1211.2330}}</ref>迪•姆洛 Di Muro等人开发了一个修复故障的模型，以避免级联失效。<ref>{{Cite journal|last=Di Muro|first=M. A.|last2=La Rocca|first2=C. E.|last3=Stanley|first3=H. E.|last4=Havlin|first4=S.|last5=Braunstein|first5=L. A.|date=2016-03-09|title=Recovery of Interdependent Networks|journal=Scientific Reports|language=En|volume=6|issue=1|pages=22834|doi=10.1038/srep22834|pmid=26956773|pmc=4783785|issn=2045-2322|arxiv=1512.02555|bibcode=2016NatSR...622834D}}</ref>

Furthermore, it was shown that such systems when embedded in space are extremely vulnerable to localized attacks or failures. Above a critical radius of damage, the failure may spread to the entire system.<ref>{{Cite journal|last=Berezin|first=Yehiel|last2=Bashan|first2=Amir|last3=Danziger|first3=Michael M.|last4=Li|first4=Daqing|last5=Havlin|first5=Shlomo|date=2015-03-11|title=Localized attacks on spatially embedded networks with dependencies|journal=Scientific Reports|language=en|volume=5|issue=1|pages=8934|doi=10.1038/srep08934|pmid=25757572|pmc=4355725|issn=2045-2322|bibcode=2015NatSR...5E8934B}}</ref>

Furthermore, it was shown that such systems when embedded in space are extremely vulnerable to localized attacks or failures. Above a critical radius of damage, the failure may spread to the entire system.

此外，研究表明，当这种系统嵌入空间时，极易受到局部攻击或故障的影响。超过临界损伤半径，故障可能扩散到整个系统。<ref>{{Cite journal|last=Berezin|first=Yehiel|last2=Bashan|first2=Amir|last3=Danziger|first3=Michael M.|last4=Li|first4=Daqing|last5=Havlin|first5=Shlomo|date=2015-03-11|title=Localized attacks on spatially embedded networks with dependencies|journal=Scientific Reports|language=en|volume=5|issue=1|pages=8934|doi=10.1038/srep08934|pmid=25757572|pmc=4355725|issn=2045-2322|bibcode=2015NatSR...5E8934B}}</ref>

== Model for overload cascading failures ==
过载级联失效模型

A model for cascading failures due to overload propagation is the Motter–Lai model.<ref>{{Cite journal|last=Motter|first=A. E.|last2=Lai|first2=Y. C.|date=2002|title=Cascade-based attacks on complex networks|url=|journal=Phys. Rev. E|volume=66|issue=6 Pt 2|pages=065102|doi=10.1103/PhysRevE.66.065102|pmid=12513335|bibcode=2002PhRvE..66f5102M|arxiv=cond-mat/0301086}}</ref> The tempo-spatial propagation of such failures have been studied by Jichang Zhao et al.<ref>{{Cite journal|last=Zhao|first=J.|last2=Li|first2=D.|last3=Sanhedrai|first3=H.|last4=Cohen|first4=R.|last5=Havlin|first5=S.|date=2016|title=Spatio-temporal propagation of cascading overload failures in spatially embedded networks|url=|journal=Nature Communications|volume=7|pages=10094|bibcode=2016NatCo...710094Z|doi=10.1038/ncomms10094|pmid=26754065|pmc=4729926}}</ref>

A model for cascading failures due to overload propagation is the Motter–Lai model. The tempo-spatial propagation of such failures have been studied by Jichang Zhao et al.

过载传播导致的级联失效的模型是Motter-Lai模型。赵继昌 Jichang Zhao等人对这种故障的时空传播进行了研究。

== See also ==
请参阅

{{div col}}

* [[Power outage|Blackouts]]
*[[停电|停电]]。

* [[Brittle system]]
* [[ 脆性系统 Brittle system]]

* [[Butterfly effect]]
* [[ 蝴蝶效应 Butterfly effect]]

* [[Byzantine failure]]
* [[拜占庭故障 Byzantine failure]]

* [[Cascading rollback]]
* [[ 级联回滚 Cascading rollback]]

* [[Chain reaction]]
* [[ 连锁反应 Chain reaction]]

* [[Chaos theory]]
* [[ 混沌理论 Chaos theory]]

* [[Cache stampede]]
* [[ 缓存雪崩 Cache stampede]]

* [[Congestion collapse]]
* [[拥塞崩溃]]

* [[Domino effect]]
* [[ 多米诺效应 Domino effect]]

* [[For Want of a Nail (proverb)]]
* [[因小失大（谚语）]]

* [[Interdependent networks]]
* [[相互依赖的网络]]

* [[Kessler Syndrome]]
* [[ 凯斯勒现象 Kessler Syndrome]]

* [[Percolation theory]]
* [[渗流理论]]

* [[Progressive collapse]]
* [[ 连续性倒塌 Progressive collapse]]

* [[Virtuous circle and vicious circle]]
*[[良性循环和恶性循环]]

* [[Wicked problem]]
* [[ 抗解问题 Wicked problem]]

{{div col end}}

== References ==
参考

{{reflist}}

== Further reading ==
进一步阅读

* {{cite web
|url=http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf
|title=Comparison of defense strategies for cascade breakdown on SF networks with degree correlations
|author=Toshiyuki Miyazaki
|date=1 March 2005
|url-status=dead
|archiveurl=https://web.archive.org/web/20090220024018/http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf
|archivedate=2009-02-20
}}

* {{cite web
|url=http://redmondmag.com/columns/print.asp?EditorialsID=1000
|title=(In)Secure Shell?
|accessdate=2007-09-08
|author=Russ Cooper
|date=1 June 2005
|publisher=RedmondMag.com
|archiveurl=https://web.archive.org/web/20070928164525/http://redmondmag.com/columns/print.asp?EditorialsID=1000
|archivedate=2007-09-28
|url-status=dead
}}

* {{cite web
|url=http://www.chds.us/?research/software&d=list
|title=Cascade Net (simulation program)
|accessdate=2007-09-08
|author=US Department of Homeland Security
|date=5 February 2007
|publisher=Center for Homeland Defense and Security
|url-status=dead
|archiveurl=https://web.archive.org/web/20081228044520/http://www.chds.us/?research%2Fsoftware&d=list
|archivedate=2008-12-28
}}

== External links ==

* [https://web.archive.org/web/20060827050151/http://www.windows.ucar.edu/spaceweather/blackout.html Space Weather: Blackout — Massive Power Grid Failure]

* [https://web.archive.org/web/20071022110507/http://vlab.infotech.monash.edu.au/simulations/networks/cascading-failure/ Cascading failure demo applet] (Monash University's Virtual Lab)

* A. E. Motter and Y.-C. Lai, [http://chaos1.la.asu.edu/~yclai/papers/PRE_02_ML_3.pdf ''Cascade-based attacks on complex networks,''] Physical Review E (Rapid Communications) 66, 065102 (2002).

* P. Crucitti, V. Latora and M. Marchiori, [https://pdfs.semanticscholar.org/aeda/97ccce03a5979dd4196fb7544ee0dc546f18.pdf ''Model for cascading failures in complex networks,''] Physical Review E (Rapid Communications) 69, 045104 (2004).

* [https://web.archive.org/web/20040704132003/http://www.epri.com/programHigh.asp?objid=261741 Protection Strategies for Cascading Grid Failures — A Shortcut Approach]

* I. Dobson, B. A. Carreras, and D. E. Newman, [https://web.archive.org/web/20060222073252/http://eceserv0.ece.wisc.edu/~dobson/PAPERS/dobsonPEIS05.pdf preprint] A loading-dependent model of probabilistic cascading failure, Probability in the Engineering and Informational Sciences, vol. 19, no. 1, January 2005, pp. 15–32.

* [https://www.pbs.org/wgbh/nova/transcripts/3105_aircrash.html Nova: Crash of Flight 111] on September 2, 1998. [[Swissair Flight 111]] flying from New York to Geneva slammed into the Atlantic Ocean off the coast of Nova Scotia with 229 people aboard. Originally believed a terrorist act. After $39 million investigation, insurance settlement of $1.5 billion and more than four years, investigators unravel the puzzle: cascading failure. What is the legacy of Swissair 111? "We have a window into the internal structure of design, checks and balances, protection, and safety." -David Evans, Editor-in-Chief of Air Safety Week.

* PhysicsWeb story: [http://physicsweb.org/articles/news/5/11/9 Accident grounds neutrino lab]

* [http://necsi.edu/affiliates/braha/StructureandDynamics.htm The Structure and Dynamics of Large Scale Organizational Networks (Dan Braha, New England Complex Systems Institute)]

*From Single Network to Network of Networks http://havlin.biu.ac.il/Pdf/Bremen070715a.pdf

{{Electricity delivery}}

[[Category:Failure]]

Category:Failure

类别: 故障

[[Category:Reliability engineering]]

Category:Reliability engineering

类别: 可靠性工程

[[Category:Electric power transmission]]

Category:Electric power transmission

类别: 输电系统

[[Category:Systemic risk]]

Category:Systemic risk

类别: 系统性风险

[[Category:Systems science]]

Category:Systems science

类别: 系统科学

<noinclude>

This page was moved from [[wikipedia:en:Cascading failure]]. Its edit history can be viewed at [[级联失效/edithistory]]</noinclude>

[[Category:待整理页面]]

级联故障

2020-12-04T03:01:43Z

WildBoar：WildBoar移动页面级联故障至级联失效

#重定向 [[级联失效]]

级联失效

2020-12-04T03:01:26Z

WildBoar：WildBoar移动页面级联故障至级联失效

本词条由11初步翻译

{{short description|System of interconnected parts in which the failure of one or few parts can trigger the failure of others}}

[[Image:Networkfailure.gif|thumb|right|An animation demonstrating how a single failure may result in other failures throughout a network.]]

[[Image:Networkfailure.gif|thumb|right|演示单个故障如何导致整个网络中其他故障的动画]]

An animation demonstrating how a single failure may result in other failures throughout a network.

演示单个故障如何导致整个网络中其他故障的动画。

A cascading failure is a process in a system of [[interconnection|interconnected]] parts in which the failure of one or few parts can trigger the failure of other parts and so on. Such a failure may happen in many types of systems, including power transmission, computer networking, finance, transportation systems, organisms, the human body, and ecosystems.

A cascading failure is a process in a system of interconnected parts in which the failure of one or few parts can trigger the failure of other parts and so on. Such a failure may happen in many types of systems, including power transmission, computer networking, finance, transportation systems, organisms, the human body, and ecosystems.

''' 级联故障 Cascading Failure'''是一个相互连接的部件系统中的一个或几个部件的故障可以引发其他部件的故障等过程。这种故障可能发生在许多类型的系统中，包括电力输送、计算机网络、金融、交通系统、微生物、人体和生态系统。

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）“''' 级联故障 Cascading Failure'''是一个相互连接的部件系统中的一个或几个部件的故障可以引发其他部件的故障等过程”有点不太顺

Cascading failures may occur when one part of the system fails. When this happens, other parts must then compensate for the failed component. This in turn overloads these nodes, causing them to fail as well, prompting additional nodes to fail one after another.

Cascading failures may occur when one part of the system fails. When this happens, other parts must then compensate for the failed component. This in turn overloads these nodes, causing them to fail as well, prompting additional nodes to fail one after another.

当系统的一部分发生故障时，可能会发生级联故障。当这种情况发生时，其他部分必须对发生故障的部分进行补偿，这反过来又使这些节点超载，导致它们也发生故障，促使更多的节点相继发生故障。

== In power transmission ==
在电力输送中

Cascading failure is common in [[power grid]]s when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in [[high voltage]] systems, where a [[single point of failure]] (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

Cascading failure is common in power grids when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in high voltage systems, where a single point of failure (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

级联故障在电网中很常见，当其中一个元件(完全或部分)发生故障并将其负荷转移到系统中附近的元件时，就会推动那些附近的元件超出其容量，从而过载，并将其负荷转移到其他元件上。级联故障在高压系统中也很常见，在一个满载或轻度过载的系统中，一个''' 单点故障 Single Point of Failure (SPF)'''会导致系统所有节点突然出现尖峰。这种''' 浪涌电流
Surge Current'''可能会导致已经超载的节点发生故障，引发更多过载，从而在很短的时间内使整个系统瘫痪。

This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer.

This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer.

这个故障过程就像池塘上的涟漪一样，在系统的各个元件中层层叠加，直到系统中的所有元件都受到损害和/或系统在功能上与负载源断开。例如，在某些情况下，一个大型电网可能因为单个变压器的故障而崩溃。

Monitoring the operation of a system, in [[real-time computing|real-time]], and judicious disconnection of parts can help stop a cascade. Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures.<ref name="chao">{{cite arXiv |last1=Zhai |first1=Chao |title=Modeling and Identification of Worst-Case Cascading Failures in Power Systems |eprint=1703.05232 |class=cs.SY |year=2017}}</ref>

Monitoring the operation of a system, in real-time, and judicious disconnection of parts can help stop a cascade. Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures.

实时监测系统的运行情况，并明智地断开部件的连接，有助于阻止级联。另一种常见的技术是通过计算机模拟可能发生的故障来计算系统的安全边际，确定安全运行水平，在此水平之下，预计计算出的任何一种情况都不会引起级联故障，并确定网络中最有可能引起级联故障的部分。

One of the primary problems with preventing electrical grid failures is that the speed of the control signal is no faster than the speed of the propagating power overload, i.e. since both the control signal and the electrical power are moving at the same speed, it is not possible to isolate the outage by sending a warning ahead to isolate the element.

One of the primary problems with preventing electrical grid failures is that the speed of the control signal is no faster than the speed of the propagating power overload, i.e. since both the control signal and the electrical power are moving at the same speed, it is not possible to isolate the outage by sending a warning ahead to isolate the element.

防止电网故障的主要问题之一是，控制信号的速度不快于传播功率过载的速度，即由于控制信号和电力都以同样的速度运动，所以无法通过提前发出警告来隔离元件从而隔离停电。

The question if power grid failures are correlated have been studied in Daqing Li et al.<ref>{{Cite journal|last=Daqing|first=Li|last2=Yinan|first2=Jiang|last3=Rui|first3=Kang|last4=Havlin|first4=Shlomo|date=2014-06-20|title=Spatial correlation analysis of cascading failures: Congestions and Blackouts|journal=Scientific Reports|language=En|volume=4|issue=1|pages=5381|doi=10.1038/srep05381|pmid=24946927|pmc=4064325|issn=2045-2322|bibcode=2014NatSR...4E5381D}}</ref> as well as by Paul DH Hines et al.<ref>{{Cite journal|last=Hines|first=Paul D. H.|last2=Dobson|first2=Ian|last3=Rezaei|first3=Pooya|date=2016|title=Cascading Power Outages Propagate Locally in an Influence Graph that is not the Actual Grid Topology|arxiv=1508.01775|journal=IEEE Transactions on Power Systems|pages=1|doi=10.1109/TPWRS.2016.2578259|issn=0885-8950}}</ref>

The question if power grid failures are correlated have been studied in Daqing Li et al. as well as by Paul DH Hines et al.

电网故障是否具有相关性的问题，李大庆等人以及Paul DH Hines等人都有研究。

=== Examples ===
案例

Cascading failure caused the following [[power outage]]s:

Cascading failure caused the following power outages:

级联故障曾导致以下停电:

* [[Northeast blackout of 1965|Blackout in Northeast America in 1965]]
* [[1965年东北大停电|1965年美国东北大停电]]

* [[1999 Southern Brazil blackout|Blackout in Southern Brazil in 1999]]
* [[1999年巴西南部停电|1999年巴西南部停电]]

* [[Northeast blackout of 2003|Blackout in Northeast America in 2003]]
* [[2003年东北大停电|2003年美国东北大停电]]

* [[2003 Italy blackout|Blackout in Italy in 2003]]
* [[2003年意大利停电|2003年意大利停电]]

* [[2003 London blackout|Blackout in London in 2003]]
* [[2003年伦敦大停电|2003年伦敦大停电]]

* [[2006 European blackout|European Blackout in 2006]]
* [[2006年欧洲停电|2006年欧洲停电]]

* [[2012 northern India power grid failure|Blackout in Northern India in 2012]]
* [[2012年印度北部电网故障|2012年印度北部停电]]

* [[2016 South Australian blackout|Blackout in South Australia in 2016]]
* [[2016年南澳停电|2016年南澳停电]]

* [[2019 Argentina, Paraguay and Uruguay blackout|Blackout in southeast South America in 2019]]
* [[2019年阿根廷、巴拉圭和乌拉圭停电|2019年南美洲东南部停电]]

== In computer networks ==
在计算机网络中

Cascading failures can also occur in [[computer network]]s (such as the [[Internet]]) in which [[Network traffic control|network traffic]] is severely impaired or halted to or between larger sections of the network, caused by failing or disconnected hardware or software. In this context, the cascading failure is known by the term '''cascade failure'''. A cascade failure can affect large groups of people and systems.

Cascading failures can also occur in computer networks (such as the Internet) in which network traffic is severely impaired or halted to or between larger sections of the network, caused by failing or disconnected hardware or software. In this context, the cascading failure is known by the term cascade failure. A cascade failure can affect large groups of people and systems.

级联故障也可能发生在计算机网络(如因特网)中，由于硬件或软件的故障或断开，导致网络中较大部分的网络通信严重受损或停止。在这种情况下，级联故障被称为术语级联故障。级联故障会影响到大批人员和系统。

The cause of a cascade failure is usually the overloading of a single, crucial [[Router (computing)|router]] or node, which causes the node to go down, even briefly. It can also be caused by taking a node down for maintenance or upgrades. In either case, traffic is [[routing|routed]] to or through another (alternative) path. This alternative path, as a result, becomes overloaded, causing it to go down, and so on. It will also affect systems which depend on the node for regular operation.

The cause of a cascade failure is usually the overloading of a single, crucial router or node, which causes the node to go down, even briefly. It can also be caused by taking a node down for maintenance or upgrades. In either case, traffic is routed to or through another (alternative) path. This alternative path, as a result, becomes overloaded, causing it to go down, and so on. It will also affect systems which depend on the node for regular operation.

级联故障的原因通常是一个单个关键的路由器或节点的超载，导致节点宕机或短暂地宕机。它也可能是由于为了维护或升级而关闭一个节点引起的。在这两种情况下，流量都被路由到或通过另一条(替代)路径。结果，这条替代路径变得过载，导致它宕机，等等。它还会影响依赖该节点正常运行的系统。

=== Symptoms ===
症状

The symptoms of a cascade failure include: [[packet loss]] and high network [[lag|latency]], not just to single systems, but to whole sections of a network or the internet. The high latency and packet loss is caused by the nodes that fail to operate due to [[congestion collapse]], which causes them to still be present in the network but without much or any useful communication going through them. As a result, routes can still be considered valid, without them actually providing communication.

The symptoms of a cascade failure include: packet loss and high network latency, not just to single systems, but to whole sections of a network or the internet. The high latency and packet loss is caused by the nodes that fail to operate due to congestion collapse, which causes them to still be present in the network but without much or any useful communication going through them. As a result, routes can still be considered valid, without them actually providing communication.

级联故障的症状包括: 数据包丢失和高网络延迟，不仅仅是对单个系统，而是对整个网络或互联网部分。高延迟和数据包丢失是由于网络拥塞崩溃导致节点无法正常运行，这使得它们仍然存在于网络中，但是没有太多或任何有用的通信通过它们。因此，路由仍然可被认为是有效的，而实际上它们并没有提供通信。

--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）“级联故障的症状” 中的症状是不是可以思考换一下词语印象中症状一般形容人换成“表现”或其他是否更好

If enough routes go down because of a cascade failure, a complete section of the network or internet can become unreachable. Although undesired, this can help speed up the recovery from this failure as connections will time out, and other nodes will give up trying to establish connections to the section(s) that have become cut off, decreasing load on the involved nodes.

If enough routes go down because of a cascade failure, a complete section of the network or internet can become unreachable. Although undesired, this can help speed up the recovery from this failure as connections will time out, and other nodes will give up trying to establish connections to the section(s) that have become cut off, decreasing load on the involved nodes.

如果有足够多的路由因为级联故障而中断，网络或互联网的一个完整部分就会无法访问。尽管我们不希望出现这种情况，但这有助于加快从故障中恢复的速度，因为连接会超时，其他节点会放弃尝试与被切断的部分建立连接，从而减少相关节点的负载。

A common occurrence during a cascade failure is a '''walking failure''', where sections go down, causing the next section to fail, after which the first section comes back up. This '''ripple''' can make several passes through the same sections or connecting nodes before stability is restored.

A common occurrence during a cascade failure is a walking failure, where sections go down, causing the next section to fail, after which the first section comes back up. This ripple can make several passes through the same sections or connecting nodes before stability is restored.

在级联故障中，一个常见的现象是行走故障，即各段下行，导致下一段故障，之后第一段回升。在恢复稳定之前，这种波纹可能会在相同的区段或连接节点上进行多次传递。

=== History ===
历史

Cascade failures are a relatively recent development, with the massive increase in traffic and the high interconnectivity between systems and networks. The term was first applied in this context in the late 1990s by a Dutch IT professional and has slowly become a relatively common term for this kind of large-scale failure.{{Citation needed|date=January 2009}}

Cascade failures are a relatively recent development, with the massive increase in traffic and the high interconnectivity between systems and networks. The term was first applied in this context in the late 1990s by a Dutch IT professional and has slowly become a relatively common term for this kind of large-scale failure.

级联故障是一个相对较新的发展，随着流量的大量增加和系统与网络之间的高度互连性而出现。这个术语最早是在90年代末由一位荷兰的IT专业人员在此情况下使用的，后来慢慢成为这种大规模故障的一个比较常见的术语。

=== Example ===
案例

Network failures typically start when a single network node fails. Initially, the traffic that would normally go through the node is stopped. Systems and users get errors about not being able to reach hosts. Usually, the redundant systems of an ISP respond very quickly, choosing another path through a different backbone. The routing path through this alternative route is longer, with more [[Hop (telecommunications)|hops]] and subsequently going through more systems that normally do not process the amount of traffic suddenly offered.

Network failures typically start when a single network node fails. Initially, the traffic that would normally go through the node is stopped. Systems and users get errors about not being able to reach hosts. Usually, the redundant systems of an ISP respond very quickly, choosing another path through a different backbone. The routing path through this alternative route is longer, with more hops and subsequently going through more systems that normally do not process the amount of traffic suddenly offered.

网络故障通常在单个网络节点故障时开始。最初，正常情况下会经过该节点的流量被停止。系统和用户会得到无法到达主机的错误。通常，ISP的冗余系统会很快做出反应，选择另一条通过不同骨干网的路径。通过这条替代路径的路由路径更长，跳数更多，随后要经过更多的系统，而这些系统通常不会处理突然提供的流量。

This can cause one or more systems along the alternative route to go down, creating similar problems of their own.

This can cause one or more systems along the alternative route to go down, creating similar problems of their own.

这可能会导致替代路线上的一个或多个系统瘫痪，造成自身的类似问题。

Also, related systems are affected in this case. As an example, [[Domain name system|DNS]] resolution might fail and what would normally cause systems to be interconnected, might break connections that are not even directly involved in the actual systems that went down. This, in turn, may cause seemingly unrelated nodes to develop problems, that can cause another cascade failure all on its own.

Also, related systems are affected in this case. As an example, DNS resolution might fail and what would normally cause systems to be interconnected, might break connections that are not even directly involved in the actual systems that went down. This, in turn, may cause seemingly unrelated nodes to develop problems, that can cause another cascade failure all on its own.

此外，在这种情况下，相关系统也会受到影响。例如，DNS解析可能会失败，通常会导致系统互连的情况可能会破坏甚至没有直接参与实际系统故障的连接。而这又可能导致看似不相关的节点出现问题，从而导致另一个级联故障的发生。

In December 2012, a partial loss (40%) of [[Gmail]] service occurred globally, for 18 minutes. This loss of service was caused by a routine update of load balancing software which contained faulty logic—in this case, the error was caused by logic using an [https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ inappropriate ''all'' instead of the more appropriate ''some''.] The cascading error was fixed by fully updating a single node in the network instead of partially updating all nodes at one time.

In December 2012, a partial loss (40%) of Gmail service occurred globally, for 18 minutes. This loss of service was caused by a routine update of load balancing software which contained faulty logic—in this case, the error was caused by logic using an [https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ inappropriate all instead of the more appropriate some.] The cascading error was fixed by fully updating a single node in the network instead of partially updating all nodes at one time.

2012年12月，Gmail服务在全球范围内出现了部分损失(40%)，持续了18分钟。这次服务损失是由包含错误逻辑的负载平衡软件的例行更新引起的--在这种情况下，该错误是由使用[https://arstechnica.com/information-technology/2012/12/why-gmail-went-down-google-misconfigured-chromes-sync-server/ 不合适的all而不是更合适的some]的逻辑引起的。通过完全更新网络中的一个节点，而不是一次部分更新所有节点，修复了级联错误。
--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]）“The cascading error”可以思考一下级联错误与级联故障是否一样

== Cascading structural failure ==
级联结构故障

Certain load-bearing structures with discrete structural components can be subject to the "zipper effect", where the failure of a single structural member increases the load on adjacent members. In the case of the [[Hyatt Regency walkway collapse]], a suspended walkway (which was already overstressed due to an error in construction) failed when a single vertical suspension rod failed, overloading the neighboring rods which failed sequentially (i.e. like a [[zipper]]). A bridge that can have such a failure is called fracture critical, and numerous bridge collapses have been caused by the failure of a single part. Properly designed structures use an adequate [[factor of safety]] and/or alternate load paths to prevent this type of mechanical cascade failure.<ref name="petroski">{{cite book| title=To Engineer Is Human: The Role of Failure in Structural Design| first=Henry| last=Petroski| year=1992| isbn=978-0-679-73416-1| publisher=Vintage| place=| url-access=registration| url=https://archive.org/details/toengineerishuma00petr}}</ref>

Certain load-bearing structures with discrete structural components can be subject to the "zipper effect", where the failure of a single structural member increases the load on adjacent members. In the case of the Hyatt Regency walkway collapse, a suspended walkway (which was already overstressed due to an error in construction) failed when a single vertical suspension rod failed, overloading the neighboring rods which failed sequentially (i.e. like a zipper). A bridge that can have such a failure is called fracture critical, and numerous bridge collapses have been caused by the failure of a single part. Properly designed structures use an adequate factor of safety and/or alternate load paths to prevent this type of mechanical cascade failure.

某些具有离散结构构件的承重结构可能会出现 "拉链效应"，即单个结构构件的失效会增加相邻构件的荷载。在凯悦酒店人行道坍塌事件中，当单根垂直悬杆失效时，悬空的人行道（由于施工中的错误，人行道已经过度受力）失效，使相邻的悬杆超载，相邻的悬杆依次失效（像拉链一样）。一座可能发生这种破坏的桥梁被称为断裂临界桥梁，许多桥梁的坍塌都是由单一部件的故障引起的。正确设计的结构使用足够的安全系数和/或交替的荷载路径来防止这种类型的机械级联失效。

== Other examples ==
其他例子

=== Biology ===
生物

[[Biochemical cascade]]s exist in biology, where a small reaction can have system-wide implications. One negative example is [[ischemic cascade]], in which a small [[ischemia|ischemic]] attack releases [[toxin]]s which kill off far more cells than the initial damage, resulting in more toxins being released. Current research is to find a way to block this cascade in [[stroke]] patients to minimize the damage.

Biochemical cascades exist in biology, where a small reaction can have system-wide implications. One negative example is ischemic cascade, in which a small ischemic attack releases toxins which kill off far more cells than the initial damage, resulting in more toxins being released. Current research is to find a way to block this cascade in stroke patients to minimize the damage.

生物学中存在着生化级联，一个小的反应就会对整个系统产生影响。一个负面的例子是缺血性级联反应，在这种反应中，一个小的缺血性发作释放出的毒素比最初的损伤杀死更多的细胞，导致更多的毒素被释放。目前的研究正在寻找一种方法来阻断中风患者的这种级联反应，以最大限度地减少损伤。

In the study of extinction, sometimes the extinction of one species will cause many other extinctions to happen. Such a species is known as a [[keystone species]].

In the study of extinction, sometimes the extinction of one species will cause many other extinctions to happen. Such a species is known as a keystone species.

在物种灭绝的研究中，有时一个物种的灭绝会导致许多其他物种的灭绝。这样的物种被称为关键物种。

=== Electronics ===
电子学

Another example is the [[Cockcroft–Walton generator]], which can also experience cascade failures wherein one failed [[diode]] can result in all the diodes failing in a fraction of a second.

Another example is the Cockcroft–Walton generator, which can also experience cascade failures wherein one failed diode can result in all the diodes failing in a fraction of a second.

另一个例子是Cockcroft-Walton发电机，它也会发生级联故障，其中一个故障的二极管会导致所有二极管在几分之一秒内发生故障。

Yet another example of this effect in a scientific experiment was the [[Implosion (mechanical process)|implosion]] in 2001 of several thousand fragile glass photomultiplier tubes used in the [[Super-Kamiokande]] experiment, where the shock wave caused by the failure of a single detector appears to have triggered the implosion of the other detectors in a chain reaction.

Yet another example of this effect in a scientific experiment was the implosion in 2001 of several thousand fragile glass photomultiplier tubes used in the Super-Kamiokande experiment, where the shock wave caused by the failure of a single detector appears to have triggered the implosion of the other detectors in a chain reaction.

在科学实验中，这种效应的另一个例子是2001年用于超级神冈探测器实验中使用的几千支易碎的玻璃光电倍增管发生内爆，其中一个探测器的故障造成的冲击波似乎引发了连锁反应中其他探测器的内爆。

=== Finance ===
金融

{{main|Systemic risk}} {{main|Cascades in financial networks}}
{{主要}系统性风险}} {{主要}金融网络中的级联}}}

In [[finance]], the risk of cascading failures of financial institutions is referred to as ''[[systemic risk]]:'' the failure of one financial institution may cause other financial institutions (its [[Counterparty|counterparties]]) to fail, cascading throughout the system.<ref name="HuangVodenska2013">{{cite journal|last1=Huang|first1=Xuqing|last2=Vodenska|first2=Irena|last3=Havlin|first3=Shlomo|last4=Stanley|first4=H. Eugene|title=Cascading Failures in Bi-partite Graphs: Model for Systemic Risk Propagation|journal=Scientific Reports|volume=3|pages=1219|year=2013|issn=2045-2322|doi=10.1038/srep01219|pmid=23386974|pmc=3564037|arxiv=1210.4973|bibcode=2013NatSR...3E1219H}}</ref>

In finance, the risk of cascading failures of financial institutions is referred to as systemic risk: the failure of one financial institution may cause other financial institutions (its counterparties) to fail, cascading throughout the system.

在金融领域，金融机构连锁倒闭的风险被称为系统性风险：一家金融机构的倒闭可能会引起其他金融机构（其交易对手）的倒闭，在整个系统中连锁倒闭。

Institutions that are believed to pose systemic risk are deemed either "[[too big to fail]]" (TBTF) or "too interconnected to fail" (TICTF), depending on why they appear to pose a threat.

Institutions that are believed to pose systemic risk are deemed either "too big to fail" (TBTF) or "too interconnected to fail" (TICTF), depending on why they appear to pose a threat.

那些被认为构成系统性风险的机构要么被视为“太大而不能倒”(TBTF) ，要么被视为“太相关而不能倒闭”(TICTF) ，这取决于它们为什么会构成威胁。

Note however that systemic risk is not due to individual institutions per se, but due to the interconnections. For detailed models in economics and finance, see Elliott et al. (2014) and Acemoglu et al. (2015).<ref name="Acemoglu Ozdaglar Tahbaz-Salehi 2015 pp. 564–608">{{cite journal | last=Acemoglu | first=Daron | last2=Ozdaglar | first2=Asuman | last3=Tahbaz-Salehi | first3=Alireza | title=Systemic Risk and Stability in Financial Networks | journal=American Economic Review | publisher=American Economic Association | volume=105 | issue=2 | year=2015 | issn=0002-8282 | doi=10.1257/aer.20130456 | pages=564–608| hdl=1721.1/100979 | hdl-access=free }}</ref><ref name="Elliott Golub Jackson 2014 pp. 3115–3153">{{cite journal | last=Elliott | first=Matthew | last2=Golub | first2=Benjamin | last3=Jackson | first3=Matthew O. | title=Financial Networks and Contagion | journal=American Economic Review | publisher=American Economic Association | volume=104 | issue=10 | year=2014 | issn=0002-8282 | doi=10.1257/aer.104.10.3115 | pages=3115–3153}}</ref>

Note however that systemic risk is not due to individual institutions per se, but due to the interconnections. For detailed models in economics and finance, see Elliott et al. (2014) and Acemoglu et al. (2015).

但请注意，系统性风险不是由于单个机构本身造成的，而是由于它们相互之间的联系。关于经济学和金融学的详细模型，请参阅Elliott等人（2014）和Acemoglu等人（2015）的文章。

A related (though distinct) type of cascading failure in finance occurs in the stock market, exemplified by the [[2010 Flash Crash]].

A related (though distinct) type of cascading failure in finance occurs in the stock market, exemplified by the 2010 Flash Crash.

金融领域的一种相关的（但不同的）级联失败发生在股票市场，2010年的闪电崩盘就是一个例子。

For another framework to study and predict the effect of cascading failures in finance see <ref>{{cite journal|last1=Li|first1=W|last2=Kenett|first2=DY|last3=Yamasaki|first3=K|last4=Stanley|first4=HE|last5=Havlin|first5=S|title=Ranking the economic importance of countries and industries|journal=Journal of Network Theory in Finance|volume=3|pages=1–17|year=2017|issn=2055-7795|doi=10.21314/JNTF.2017.031|arxiv=1408.0443}}</ref><ref name="HuangVodenska2013"/>

For another framework to study and predict the effect of cascading failures in finance see

有关研究和预测金融连锁反应影响的另一个框架，请参见

== Interdependent cascading failures ==
相互依赖的级联故障

[[File:Interdependent_relationship_among_different_infrastructures.tif|thumb|right|Fig. 1: Illustration of the interdependent relationship among different infrastructures]]

Fig. 1: Illustration of the interdependent relationship among different infrastructures

图1: 不同基础设施之间的相互依存关系的说明

[[File:Schematic_demonstration_of_first-_and_second-order_percolation_transitions.tif|thumb|right|Fig. 2. Schematic demonstration of first- and second-order percolation transitions. In the second-order case, the giant component is continuously approaching zero at the percolation threshold p = p_c. In the first-order case, the giant component approaches zero discontinuously]]

Fig. 2. Schematic demonstration of first- and second-order percolation transitions. In the second-order case, the giant component is continuously approaching zero at the percolation threshold p = p_c. In the first-order case, the giant component approaches zero discontinuously

图2：一阶和二阶渗流过渡的示意图。在二阶情况下，'''最大连通分支 giant component'''在渗流阈值p=p_c时不断接近零。在一阶情况下，最大连通分支不连续地接近零。

Diverse [[infrastructure]]s such as [[water supply]], [[transportation]], fuel and [[power station]]s are coupled together and depend on each other for functioning, see Fig. 1. Owing to this coupling, interdependent networks are extremely sensitive to random failures, and in particular to [[Targeted threat|targeted attacks]], such that a failure of a small fraction of nodes in one network can triger an iterative cascade of failures in several interdependent networks.<ref>{{cite web|title=Report of the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack|url=http://empcommission.org/docs/A2473-EMP_Commission-7MB.pdf}}</ref><ref>{{Cite journal|last=Rinaldi|first=S.M.|last2=Peerenboom|first2=J.P.|last3=Kelly|first3=T.K.|date=2001|title=Identifying, understanding, and analyzing critical infrastructure interdependencies|url=|journal= IEEE Control Systems Magazine|volume=21|pages=11–25|via=}}</ref> [[Power outage|Electrical blackouts]] frequently result from a cascade of failures between interdependent networks, and the problem has been dramatically exemplified by the several large-scale blackouts that have occurred in recent years. Blackouts are a fascinating demonstration of the important role played by the dependencies between networks. For example, the [[2003 Italy blackout]] resulted in a widespread failure of the [[Rail transport|railway network]], [[Health system|health care systems]], and [[financial services]] and, in addition, severely influenced the [[telecommunication network]]s. The partial failure of the communication system in turn further impaired the [[electrical grid]] management system, thus producing a positive feedback on the power grid.<ref>{{cite journal|last=V. Rosato |first=Issacharoff, L., Tiriticco, F., Meloni, S., Porcellinis, S.D., & Setola, R. |title=Modelling interdependent infrastructures using interacting dynamical models |journal=International Journal of Critical Infrastructures |year=2008 |volume=4 |pages=63–79 |doi=10.1504/IJCIS.2008.016092 }}</ref> This example emphasizes how inter-dependence can significantly magnify the damage in an interacting network system. A framework to study the cascading failures between coupled networks based on percolation theory was developed recently.<ref>{{cite journal|last=S. V. Buldyrev|first=R. Parshani, G. Paul, H. E. Stanley, S. Havlin|title=Catastrophic cascade of failures in interdependent networks|journal=Nature|year=2010|volume=464|pages=1025–8|doi=10.1038/nature08932|url=http://havlin.biu.ac.il/Publications.php?keyword=Catastrophic+cascade+of+failures+in+interdependent+networks&year=*&match=all|pmid=20393559|issue=7291

Diverse infrastructures such as water supply, transportation, fuel and power stations are coupled together and depend on each other for functioning, see Fig. 1. Owing to this coupling, interdependent networks are extremely sensitive to random failures, and in particular to targeted attacks, such that a failure of a small fraction of nodes in one network can triger an iterative cascade of failures in several interdependent networks. Electrical blackouts frequently result from a cascade of failures between interdependent networks, and the problem has been dramatically exemplified by the several large-scale blackouts that have occurred in recent years. Blackouts are a fascinating demonstration of the important role played by the dependencies between networks. For example, the 2003 Italy blackout resulted in a widespread failure of the railway network, health care systems, and financial services and, in addition, severely influenced the telecommunication networks. The partial failure of the communication system in turn further impaired the electrical grid management system, thus producing a positive feedback on the power grid. This example emphasizes how inter-dependence can significantly magnify the damage in an interacting network system. A framework to study the cascading failures between coupled networks based on percolation theory was developed recently.<ref>{{cite journal|last=S. V. Buldyrev|first=R. Parshani, G. Paul, H. E. Stanley, S. Havlin|title=Catastrophic cascade of failures in interdependent networks|journal=Nature|year=2010|volume=464|pages=1025–8|doi=10.1038/nature08932|url=http://havlin.biu.ac.il/Publications.php?keyword=Catastrophic+cascade+of+failures+in+interdependent+networks&year=*&match=all|pmid=20393559|issue=7291

诸如供水、运输、燃料和发电站等多种基础设施都是耦合在一起的，并相互依赖着运行，见图1。由于这种耦合，相互依存的网络对随机故障，特别是对有针对性的攻击极为敏感，因此，一个网络中一小部分节点的故障就会导致几个相互依存的网络中出现一连串的故障。电气停电经常是由相互依赖的网络之间的故障级联造成的，近年来发生的几次大规模停电事件就极大地说明了这个问题。停电是网络之间的依存关系所起的重要作用的一个引人入胜的证明。例如，2003年意大利大停电导致铁路网、医疗系统、金融服务大面积瘫痪，此外，还严重影响了电信网络。通信系统的部分故障又进一步损害了电网管理系统，从而对电网产生了正反馈。这个例子强调了在一个相互影响的网络系统中，相互依赖性是如何显著放大损害的。基于''' 渗流理论 Percolation Theory'''，最近发展了一个研究耦合网络之间级联故障的框架。1 = r.在相互依赖的网络中灾难性的级联故障 | 杂志 = 自然 | 年 = 2010 | 卷 = 464 | 页 = 1025-8 | doi = 10.1038/nature08932 | url = http://Havlin.biu.ac.il/publications.php?keyword=Catastrophic+cascade+of+failures+in+interdependent+networks&year=*&match=all|pmid=20393559|issue=7291

|arxiv=1012.0206|bibcode=2010Natur.464.1025B}}</ref> The cascading failures can lead to abrupt collapse compare to percolation in a single network where the breakdown of the network is continuous, see Fig. 2.

|arxiv=1012.0206|bibcode=2010Natur.464.1025B}}</ref> The cascading failures can lead to abrupt collapse compare to percolation in a single network where the breakdown of the network is continuous, see Fig. 2.

与级联故障可能会导致突然崩溃相比，在单一网络中，网络的崩溃是连续的，见图2。

Cascading failures in spatially embedded systems have been

Cascading failures in spatially embedded systems have been

空间嵌入式系统中的级联故障已经成为当前研究的热点。

shown to lead to extreme vulnerability.<ref name="BashanBerezin2013">{{cite journal|last1=Bashan|first1=Amir|last2=Berezin|first2=Yehiel|last3=Buldyrev|first3=Sergey V.|last4=Havlin|first4=Shlomo|title=The extreme vulnerability of interdependent spatially embedded networks|journal=Nature Physics|year=2013|issn=1745-2473|doi=10.1038/nphys2727|volume=9|issue=10|pages=667–672|arxiv=1206.2062|bibcode=2013NatPh...9..667B}}</ref> For the dynamic process of cascading failures see ref.<ref>{{Cite journal|last=Zhou|first=D.|last2=Bashan|first2=A.|last3=Cohen|first3=R.|last4=Berezin|first4=Y.|last5=Shnerb|first5=N.|last6=Havlin|first6=S.|date=2014|title=Simultaneous first- and second-order percolation transitions in interdependent networks|url=|journal=Phys. Rev. E|volume=90|issue=1|pages=012803|bibcode=2014PhRvE..90a2803Z|doi=10.1103/PhysRevE.90.012803|pmid=25122338|arxiv=1211.2330}}</ref> A model for repairing failures in order to avoid cascading failures was developed by Di Muro et al.<ref>{{Cite journal|last=Di Muro|first=M. A.|last2=La Rocca|first2=C. E.|last3=Stanley|first3=H. E.|last4=Havlin|first4=S.|last5=Braunstein|first5=L. A.|date=2016-03-09|title=Recovery of Interdependent Networks|journal=Scientific Reports|language=En|volume=6|issue=1|pages=22834|doi=10.1038/srep22834|pmid=26956773|pmc=4783785|issn=2045-2322|arxiv=1512.02555|bibcode=2016NatSR...622834D}}</ref>

shown to lead to extreme vulnerability. For the dynamic process of cascading failures see ref. A model for repairing failures in order to avoid cascading failures was developed by Di Muro et al.

显示会导致极端的脆弱性。关于级联故障的动态过程见参考文献。Di Muro等人开发了一个修复故障的模型，以避免级联故障。

Furthermore, it was shown that such systems when embedded in space are extremely vulnerable to localized attacks or failures. Above a critical radius of damage, the failure may spread to the entire system.<ref>{{Cite journal|last=Berezin|first=Yehiel|last2=Bashan|first2=Amir|last3=Danziger|first3=Michael M.|last4=Li|first4=Daqing|last5=Havlin|first5=Shlomo|date=2015-03-11|title=Localized attacks on spatially embedded networks with dependencies|journal=Scientific Reports|language=en|volume=5|issue=1|pages=8934|doi=10.1038/srep08934|pmid=25757572|pmc=4355725|issn=2045-2322|bibcode=2015NatSR...5E8934B}}</ref>

Furthermore, it was shown that such systems when embedded in space are extremely vulnerable to localized attacks or failures. Above a critical radius of damage, the failure may spread to the entire system.

此外，研究表明，当这种系统嵌入空间时，极易受到局部攻击或故障的影响。超过临界损伤半径，故障可能扩散到整个系统。

== Model for overload cascading failures ==
过载级联故障模型

A model for cascading failures due to overload propagation is the Motter–Lai model.<ref>{{Cite journal|last=Motter|first=A. E.|last2=Lai|first2=Y. C.|date=2002|title=Cascade-based attacks on complex networks|url=|journal=Phys. Rev. E|volume=66|issue=6 Pt 2|pages=065102|doi=10.1103/PhysRevE.66.065102|pmid=12513335|bibcode=2002PhRvE..66f5102M|arxiv=cond-mat/0301086}}</ref> The tempo-spatial propagation of such failures have been studied by Jichang Zhao et al.<ref>{{Cite journal|last=Zhao|first=J.|last2=Li|first2=D.|last3=Sanhedrai|first3=H.|last4=Cohen|first4=R.|last5=Havlin|first5=S.|date=2016|title=Spatio-temporal propagation of cascading overload failures in spatially embedded networks|url=|journal=Nature Communications|volume=7|pages=10094|bibcode=2016NatCo...710094Z|doi=10.1038/ncomms10094|pmid=26754065|pmc=4729926}}</ref>

A model for cascading failures due to overload propagation is the Motter–Lai model. The tempo-spatial propagation of such failures have been studied by Jichang Zhao et al.

过载传播导致的级联故障的模型是Motter-Lai模型。赵继昌等人对这种故障的速度空间传播进行了研究。

== See also ==
请参阅

{{div col}}

* [[Power outage|Blackouts]]
*[[停电|停电]]。

* [[Brittle system]]
* [[脆性系统]]

* [[Butterfly effect]]
* [[蝴蝶效应]]

* [[Byzantine failure]]
* [[拜占庭故障]]

* [[Cascading rollback]]
* [[级联回滚]]

* [[Chain reaction]]
* [[连锁反应]]

* [[Chaos theory]]
* [[混沌理论]]

* [[Cache stampede]]
* [[缓存雪崩]]

* [[Congestion collapse]]
* [[拥堵崩溃]]

* [[Domino effect]]
* [[多米诺效应]]

* [[For Want of a Nail (proverb)]]
* [[只因少了一颗钉子（谚语）]]

* [[Interdependent networks]]
* [[相互依赖的网络]]

* [[Kessler Syndrome]]
* [[凯斯勒综合症]]

* [[Percolation theory]]
* [[渗流理论]]

* [[Progressive collapse]]
* [[渐进式崩溃]]

* [[Virtuous circle and vicious circle]]
*[[良性循环和恶性循环]]

* [[Wicked problem]]
* [[抗解问题]]

{{div col end}}

== References ==
参考

{{reflist}}

== Further reading ==
进一步阅读

* {{cite web

|url=http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf

|url=http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf

Http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf

|title=Comparison of defense strategies for cascade breakdown on SF networks with degree correlations

|title=Comparison of defense strategies for cascade breakdown on SF networks with degree correlations

具有度相关性的 SF 网络级联故障的防御策略比较

|author=Toshiyuki Miyazaki

|author=Toshiyuki Miyazaki

|author=Toshiyuki Miyazaki

|date=1 March 2005

|date=1 March 2005

日期 = 2005年3月1日

|url-status=dead

|url-status=dead

地位 = 死亡

|archiveurl=https://web.archive.org/web/20090220024018/http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf

|archiveurl=https://web.archive.org/web/20090220024018/http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf

2012年3月24日 | archiveurl = https://web.archive.org/web/20090220024018/http://www.jaist.ac.jp/library/thesis/ks-master-2005/abstract/tmiyazak/abstract.pdf

|archivedate=2009-02-20

|archivedate=2009-02-20

| archivedate = 2009-02-20

}}

}}

}}

* {{cite web

|url=http://redmondmag.com/columns/print.asp?EditorialsID=1000

|url=http://redmondmag.com/columns/print.asp?EditorialsID=1000

1000 http://redmondmag.com/columns/print.asp

|title=(In)Secure Shell?

|title=(In)Secure Shell?

| title = (In) Secure Shell? ？

|accessdate=2007-09-08

|accessdate=2007-09-08

2007-09-08

|author=Russ Cooper

|author=Russ Cooper

作者: Russ Cooper

|date=1 June 2005

|date=1 June 2005

日期 = 2005年6月1日

|publisher=RedmondMag.com

|publisher=RedmondMag.com

| publisher = RedmondMag.com

|archiveurl=https://web.archive.org/web/20070928164525/http://redmondmag.com/columns/print.asp?EditorialsID=1000

|archiveurl=https://web.archive.org/web/20070928164525/http://redmondmag.com/columns/print.asp?EditorialsID=1000

1000 https://web.archive.org/web/20070928164525/http://redmondmag.com/columns/print.asp

|archivedate=2007-09-28

|archivedate=2007-09-28

| archivedate = 2007-09-28

|url-status=dead

|url-status=dead

地位 = 死亡

}}

}}

}}

* {{cite web

|url=http://www.chds.us/?research/software&d=list

|url=http://www.chds.us/?research/software&d=list

Http://www.chds.us/?research/software&d=list

|title=Cascade Net (simulation program)

|title=Cascade Net (simulation program)

| title = Cascade Net (仿真程序)

|accessdate=2007-09-08

|accessdate=2007-09-08

2007-09-08

|author=US Department of Homeland Security

|author=US Department of Homeland Security

美国国土安全部

|date=5 February 2007

|date=5 February 2007

| 日期 = 2007年2月5日

|publisher=Center for Homeland Defense and Security

|publisher=Center for Homeland Defense and Security

| publisher = 国土安全防御中心

|url-status=dead

|url-status=dead

地位 = 死亡

|archiveurl=https://web.archive.org/web/20081228044520/http://www.chds.us/?research%2Fsoftware&d=list

|archiveurl=https://web.archive.org/web/20081228044520/http://www.chds.us/?research%2Fsoftware&d=list

2012年3月24日 | archiveurl = https://web.archive.org/web/20081228044520/http://www.chds.us/?research%2fsoftware&d=list

|archivedate=2008-12-28

|archivedate=2008-12-28

| archivedate = 2008-12-28

}}

}}

}}

== External links ==

* [https://web.archive.org/web/20060827050151/http://www.windows.ucar.edu/spaceweather/blackout.html Space Weather: Blackout — Massive Power Grid Failure]

* [https://web.archive.org/web/20071022110507/http://vlab.infotech.monash.edu.au/simulations/networks/cascading-failure/ Cascading failure demo applet] (Monash University's Virtual Lab)

* A. E. Motter and Y.-C. Lai, [http://chaos1.la.asu.edu/~yclai/papers/PRE_02_ML_3.pdf ''Cascade-based attacks on complex networks,''] Physical Review E (Rapid Communications) 66, 065102 (2002).

* P. Crucitti, V. Latora and M. Marchiori, [https://pdfs.semanticscholar.org/aeda/97ccce03a5979dd4196fb7544ee0dc546f18.pdf ''Model for cascading failures in complex networks,''] Physical Review E (Rapid Communications) 69, 045104 (2004).

* [https://web.archive.org/web/20040704132003/http://www.epri.com/programHigh.asp?objid=261741 Protection Strategies for Cascading Grid Failures — A Shortcut Approach]

* I. Dobson, B. A. Carreras, and D. E. Newman, [https://web.archive.org/web/20060222073252/http://eceserv0.ece.wisc.edu/~dobson/PAPERS/dobsonPEIS05.pdf preprint] A loading-dependent model of probabilistic cascading failure, Probability in the Engineering and Informational Sciences, vol. 19, no. 1, January 2005, pp. 15–32.

* [https://www.pbs.org/wgbh/nova/transcripts/3105_aircrash.html Nova: Crash of Flight 111] on September 2, 1998. [[Swissair Flight 111]] flying from New York to Geneva slammed into the Atlantic Ocean off the coast of Nova Scotia with 229 people aboard. Originally believed a terrorist act. After $39 million investigation, insurance settlement of $1.5 billion and more than four years, investigators unravel the puzzle: cascading failure. What is the legacy of Swissair 111? "We have a window into the internal structure of design, checks and balances, protection, and safety." -David Evans, Editor-in-Chief of Air Safety Week.

* PhysicsWeb story: [http://physicsweb.org/articles/news/5/11/9 Accident grounds neutrino lab]

* [http://necsi.edu/affiliates/braha/StructureandDynamics.htm The Structure and Dynamics of Large Scale Organizational Networks (Dan Braha, New England Complex Systems Institute)]

*From Single Network to Network of Networks http://havlin.biu.ac.il/Pdf/Bremen070715a.pdf

{{Electricity delivery}}

[[Category:Failure]]

Category:Failure

类别: 失败

[[Category:Reliability engineering]]

Category:Reliability engineering

类别: 可靠度

[[Category:Electric power transmission]]

Category:Electric power transmission

类别: 输电系统

[[Category:Systemic risk]]

Category:Systemic risk

类别: 系统性风险

[[Category:Systems science]]

Category:Systems science

类别: 系统科学

<noinclude>

This page was moved from [[wikipedia:en:Cascading failure]]. Its edit history can be viewed at [[级联故障/edithistory]]</noinclude>

[[Category:待整理页面]]

多米诺效应

2020-11-30T08:51:16Z

WildBoar：

此词条暂由Henry翻译。已由WildBoar完成审校

{{other uses|Domino Effect (disambiguation)}}

[[Image:Domino 01.jpg|thumb|Domino effect events]]

Domino effect events

 多米诺效应 Domino effect事件

[[Image:Domino effect.jpg|thumb|upright|(Top) Dominoes are standing. (Bottom) Dominoes are in motion.]]

(Top) Dominoes are standing. (Bottom) Dominoes are in motion.

(上图)多米诺骨牌竖立着。(下图)多米诺骨牌正在运动。

A '''domino effect''' or '''[[chain reaction]]''' is the cumulative effect produced when one event sets off a chain of similar events.<ref>{{cite web|title=domino effect|url=http://www.thefreedictionary.com/domino+effect|website=The Free Dictionary|publisher=Farlex, Inc.|accessdate=29 September 2014}}</ref> The term is best known as a mechanical effect and is used as an analogy to a [[Domino show|falling row]] of [[dominoes]]. It typically refers to a linked sequence of events where the time between successive events is relatively small. It can be used literally (an observed series of actual collisions) or metaphorically (causal linkages within systems such as global finance or politics). The term ''domino effect'' is used both to imply that an event is inevitable or highly likely (as it has already started to happen), and conversely to imply that an event is impossible or highly unlikely (the one domino left standing).

A domino effect or chain reaction is the cumulative effect produced when one event sets off a chain of similar events. The term is best known as a mechanical effect and is used as an analogy to a falling row of dominoes. It typically refers to a linked sequence of events where the time between successive events is relatively small. It can be used literally (an observed series of actual collisions) or metaphorically (causal linkages within systems such as global finance or politics). The term domino effect is used both to imply that an event is inevitable or highly likely (as it has already started to happen), and conversely to imply that an event is impossible or highly unlikely (the one domino left standing).

 多米诺效应 Domino effect或连锁反应是一个事件引发一连串类似事件时所产生的累积效应。<ref>{{cite web|title=domino effect|url=http://www.thefreedictionary.com/domino+effect|website=The Free Dictionary|publisher=Farlex, Inc.|accessdate=29 September 2014}}</ref>这个术语最广为人知的就是机械效应，它可以类比为一排正在倒下的多米诺骨牌。它通常指相邻事件之间的时间间隔相对较小的一系列事件。它可以按字面意思使用(观察到的一系列实际碰撞) ，也可以隐喻性地使用(例如全球金融或政治系统中的因果联系)。术语“多米诺效应”既用来暗示某一事件是不可避免或极有可能发生的(因为第一块多米诺骨牌已经倒了) ，也可用来反过来暗示某一事件是不可能发生的或极不可能发生的(第一个多米诺骨牌还站着 )。

== Demonstration of the effect ==
效应展示

The domino effect can easily be visualized by placing a row of [[dominoes]] upright, each separated by a small distance. Upon pushing the first domino, the next domino in line will be knocked over, and so on, thus firing a linear chain in which each domino's fall is triggered by the domino immediately preceding it. The effect is the same regardless of the length of the chain. The energy used in this chain reaction is the [[potential energy]] of the dominoes due to them being in a [[metastable]] state; when the first domino is toppled, the energy transferred by the fall is greater than the energy needed to knock over the following domino, and so on.

The domino effect can easily be visualized by placing a row of dominoes upright, each separated by a small distance. Upon pushing the first domino, the next domino in line will be knocked over, and so on, thus firing a linear chain in which each domino's fall is triggered by the domino immediately preceding it. The effect is the same regardless of the length of the chain. The energy used in this chain reaction is the potential energy of the dominoes due to them being in a metastable state; when the first domino is toppled, the energy transferred by the fall is greater than the energy needed to knock over the following domino, and so on.

将一排多米诺骨牌竖立起来，每个骨牌之间相隔一小段距离，就可以很容易地看到多米诺骨牌效应。在推倒第一张多米诺骨牌后，下一张多米诺骨牌就会被推倒，如此循环往复，这样就形成了一个线性链，每一张多米诺骨牌的倒下都是由之前的多米诺骨牌触发的。不管链的长度如何，效果都是一样的。这种连锁反应所使用的能量是多米诺骨牌处于亚稳态时的势能; 当第一个多米诺骨牌被推倒时，下落所转移的能量大于推倒下一个多米诺骨牌所需要的能量，以此类推。

The domino effect is exploited in [[Rube Goldberg machine]]s.

The domino effect is exploited in Rube Goldberg machines.

多米诺效应在 鲁布·戈德堡机械 Rube Goldberg machine
中应用。

==Appearances in media==
媒体中的表现
*''[[Domino Day]]'' – world record attempt for the highest number of toppling domino stones.

多米诺日--世界纪录推倒最多多米诺骨牌的尝试

==See also==
参阅

*[[Ripple effect]]
 波及反应 Ripple effect
*[[Rube Goldberg machine]]
 鲁布·戈德堡机械

Relevant physical theory:

Relevant physical theory:

相关物理理论:

*[[Butterfly effect]]
 蝴蝶效应 Butterfly effect

[[Cascading failure]]
 连锁故障 Cascading failure
*[[Causality]]
 因果律 Causality
*[[Chain reaction]]
 连锁反应 Chain reaction
*[[Snowball effect]]
 雪球效应 Snowball effect

Mathematical theory

Mathematical theory

数学理论

*[[Mathematical induction]]
 数学归纳法 Mathematical induction

Political theory

Political theory

政治理论

*[[Domino theory]]
 多米诺理论Domino theory

Social

Social

社交

*[[Chinese whispers]]
三人成虎
*[[Behavioral contagion]]
行为传染
*[[Copycat crime]]
模仿犯罪

==References==
参考
{{Reflist}}

{{commons category}}

==Further reading==
深度阅读
*''Impact Mechanics'', W. J. Stronge, Cambridge University Press, 2004, {{ISBN|0-521-60289-0}}, {{ISBN|978-0-521-60289-1}}

{{DEFAULTSORT:Domino Effect}}

[[Category:Metaphors referring to objects]]

Category:Metaphors referring to objects

类别: 指事物的隐喻

[[Category:Causality]]

Category:Causality

分类: 因果关系

<noinclude>

This page was moved from [[wikipedia:en:Domino effect]]. Its edit history can be viewed at [[多米诺效应/edithistory]]</noinclude>

[[Category:待整理页面]]

反馈

2020-11-29T17:15:29Z

WildBoar：

本词条由11初步翻译

https://wiki.swarma.org/index.php?title=%E5%B9%B3%E8%A1%A1%E7%90%86%E8%AE%BA#:~:text=%E6%9C%AC%E8%AF%8D%E6%9D%A1%E7%94%B1,11%E5%88%9D%E6%AD%A5%E7%BF%BB%E8%AF%91

{{Other uses}}
其他用途

{{short description|Process where information about current status is used to influence future status}}
简述|利用当前状态信息影响未来状态的过程

{{Use dmy dates|date=September 2020}}
使用dmy日期|日期=2020年9月

{{Complex systems}}[[File:General Feedback Loop.svg|thumb|A feedback loop where all outputs of a process are available as causal inputs to that process]]

A feedback loop where all outputs of a process are available as causal inputs to that process

一个反馈回路过程的所有输出都可作为该过程的因果输入。

'''Feedback''' occurs when outputs of a system are routed back as inputs as part of a [[Signal chain (signal processing chain)|chain]] of [[Causality|cause-and-effect]] that forms a circuit or loop.<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref> The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:

Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:

当一个系统的输出作为输入被送回，并作为形成回路或循环的因果链的一部分时，就会产生 反馈 feedback。<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref>这个系统可以说是反馈到了自身。在因果关系应用于反馈系统时，必须谨慎处理其概念。

{{quote
|text=Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole.
|author=Karl Johan Åström and Richard M.Murray
|title=''Feedback Systems: An Introduction for Scientists and Engineers''<ref>{{cite book |title=Feedback Systems: An Introduction for Scientists and Engineers |author1=Karl Johan Åström |author2=Richard M. Murray |chapter=§1.1: What is feedback? |chapter-url=https://books.google.com/books?id=cdG9fNqTDS8C&q=%22This+makes+reasoning+based+on+cause+and+effect+tricky%22&pg=PA1 |isbn= 9781400828739 |year=2008 |page=1 |publisher=Princeton University Press}} Online version found [http://authors.library.caltech.edu/25062/1/Feedback08.pdf here].</ref>}}

{{quote
|text=Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole.
|author=Karl Johan Åström and Richard M.Murray
|title=Feedback Systems: An Introduction for Scientists and Engineers}}

{{引用
对于一个反馈系统，很难进行简单的因果推理，因为第一个系统影响第二个系统，第二个系统影响第一个系统，产生了一个循环论证。这就使得基于因果关系的推理变得很困难，因此有必要将系统作为一个整体进行分析。
|作者:卡尔·约翰·阿斯特洛姆 · 马丁 Karl Johan Åström和查德 · M · 默里 Richard M.Murray
| title = 反馈系统: 科学家和工程师介绍<ref>{{cite book |title=Feedback Systems: An Introduction for Scientists and Engineers |author1=Karl Johan Åström |author2=Richard M. Murray |chapter=§1.1: What is feedback? |chapter-url=https://books.google.com/books?id=cdG9fNqTDS8C&q=%22This+makes+reasoning+based+on+cause+and+effect+tricky%22&pg=PA1 |isbn= 9781400828739 |year=2008 |page=1 |publisher=Princeton University Press}} Online version found [http://authors.library.caltech.edu/25062/1/Feedback08.pdf here].</ref>}

==History==
历史

Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter [[Economics|economic theory]] in Britain by the 18th century, but it was not at that time recognized as a universal abstraction and so did not have a name.<ref name=mayr>{{Cite book |author= Otto Mayr|title=Authority, liberty, & automatic machinery in early modern Europe |year=1989 |isbn=978-0-8018-3939-9 | publisher=Johns Hopkins University Press |author-link=Otto Mayr }}</ref>

Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter economic theory in Britain by the 18th century, but it was not at that time recognized as a universal abstraction and so did not have a name.

自我调节机制自古以来就存在，直到18世纪，反馈的概念开始进入英国的经济理论，但当时它还不是一个普遍的抽象概念，因此没有名称。<ref name=mayr>{{Cite book |author= Otto Mayr|title=Authority, liberty, & automatic machinery in early modern Europe |year=1989 |isbn=978-0-8018-3939-9 | publisher=Johns Hopkins University Press |author-link=Otto Mayr }}</ref>

The first ever known artificial feedback device was a [[Ballcock|float valve]], for maintaining water at a constant level, invented in 270 BC in [[Alexandria]], [[Ancient Egypt|Egypt]].<ref name=":0">{{Cite book|title=Designing Kinetics for Architectural Facades|last=Moloney|first=Jules|publisher=Routledge|year=2011|isbn=978-0415610346}}</ref> This device illustrated the principle of feedback: a low water level opens the valve, the rising water then provides feedback into the system, closing the valve when the required level is reached. This then reoccurs in a circular fashion as the water level fluctuates.<ref name=":0" />

The first ever known artificial feedback device was a float valve, for maintaining water at a constant level, invented in 270 BC in Alexandria, Egypt. This device illustrated the principle of feedback: a low water level opens the valve, the rising water then provides feedback into the system, closing the valve when the required level is reached. This then reoccurs in a circular fashion as the water level fluctuates.

第一个已知的人工反馈装置是公元前270年在埃及亚历山大发明的用于保持水位恒定的浮阀。<ref name=":0">{{Cite book|title=Designing Kinetics for Architectural Facades|last=Moloney|first=Jules|publisher=Routledge|year=2011|isbn=978-0415610346}}</ref>这个装置说明了反馈的原理：低水位打开阀门，上升的水位向系统提供反馈，达到所需水位时关闭阀门。然后，这种情况会随着水位的波动循环地重复发生。<ref name=":0" />

[[Centrifugal governor]]s were used to regulate the distance and pressure between [[millstone]]s in [[windmill]]s since the 17th century. In 1788, [[James Watt]] designed his first centrifugal governor following a suggestion from his business partner [[Matthew Boulton]], for use in the [[steam engine]]s of their production. Early steam engines employed a purely [[reciprocating motion]], and were used for pumping water – an application that could tolerate variations in the working speed, but the use of steam engines for other applications called for more precise control of the speed.

Centrifugal governors were used to regulate the distance and pressure between millstones in windmills since the 17th century. In 1788, James Watt designed his first centrifugal governor following a suggestion from his business partner Matthew Boulton, for use in the steam engines of their production. Early steam engines employed a purely reciprocating motion, and were used for pumping water – an application that could tolerate variations in the working speed, but the use of steam engines for other applications called for more precise control of the speed.

自17世纪以来，[[离心调速器]]被用于调节[[风车]]中[[磨石]]之间的距离和压力。1788年，詹姆斯·瓦特 James Watt根据他的商业伙伴马修·布尔顿 Matthew Boulton的建议，设计了他的第一个离心调速器，应用于他们生产的[[蒸汽机]]。早期的蒸汽机采用纯粹的[[往复运动]]，用于抽水——这种应用不受工作速度变化的影响，但蒸汽机在其他应用中的使用需要更精确的速度控制。

In [[1868]], [[James Clerk Maxwell]] wrote a famous paper, "On governors", that is widely considered a classic in feedback control theory.<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=free}}</ref> This was a landmark paper on [[control theory]] and the mathematics of feedback.

In 1868, James Clerk Maxwell wrote a famous paper, "On governors", that is widely considered a classic in feedback control theory.This was a landmark paper on [[control theory]] and the mathematics of feedback.

在1868年，詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell写了一篇著名的论文《论调速器》，这个论文被广泛认为是反馈控制理论的经典之作。<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=free}}</ref>这是一篇关于控制理论和反馈数学的里程碑式的论文。

The verb phrase ''to feed back'', in the sense of returning to an earlier position in a mechanical process, was in use in the US by the 1860s,<ref>''"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..."'' HH Cole, "Improvement in Fluting-Machines", [http://www.google.co.nz/patents/US55469 US Patent 55,469 (1866)] accessed 23 March 2012.</ref><ref>''"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..."'' JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", [http://www.google.co.nz/patents/US47769 US Patent 47,769 (1865)] accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error</ref> and in 1909, Nobel laureate [[Karl Ferdinand Braun]] used the term "feed-back" as a noun to refer to (undesired) [[Coupling (electronics)|coupling]] between components of an [[electronic circuit]].<ref>''"...as far as possible the circuit has no feed-back into the system being investigated."''
An example of a negative feedback loop with goals
[http://www.cdvandtext2.org/Braun-Nobel-lecture%201909.pdf]
A positive feedback loop example
Karl Ferdinand Braun, [https://www.nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.html "Electrical oscillations and wireless telegraphy"], Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.</ref>

The verb phrase to feed back, in the sense of returning to an earlier position in a mechanical process, was in use in the US by the 1860s, and in 1909, Nobel laureate Karl Ferdinand Braun used the term "feed-back" as a noun to refer to (undesired) coupling between components of an electronic circuit.

19世纪60年代，美国开始使用动词短语反馈，意思是在机械过程中回到原来的位置。<ref>''"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..."'' HH Cole, "Improvement in Fluting-Machines", [http://www.google.co.nz/patents/US55469 US Patent 55,469 (1866)] accessed 23 March 2012.</ref><ref>''"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..."'' JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", [http://www.google.co.nz/patents/US47769 US Patent 47,769 (1865)] accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error</ref> 1909年，诺贝尔奖获得者卡尔·费迪南德·布劳恩 Karl Ferdinand Braun用名词“反馈”来指电子电路元件之间的(不希望有的)耦合。<ref>''"...as far as possible the circuit has no feed-back into the system being investigated."''
An example of a negative feedback loop with goals
[http://www.cdvandtext2.org/Braun-Nobel-lecture%201909.pdf]
A positive feedback loop example
Karl Ferdinand Braun, [https://www.nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.html "Electrical oscillations and wireless telegraphy"], Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.</ref>

By the end of 1912, researchers using early electronic amplifiers ([[audion tube|audions]]) had discovered that deliberately coupling part of the output signal back to the input circuit would boost the amplification (through [[Regenerative circuit|regeneration]]), but would also cause the audion to howl or sing.<ref name="bennett">{{Cite book|url=http://worldcat.org/isbn/0-906-04807-9|title=A history of control engineering, 1800–1930|author=Stuart Bennett|publisher=Peregrinus for the Institution of Electrical Engineers|year=1979|isbn=978-0-906048-07-8|location=Stevenage; New York}} </ref> This action of feeding back of the signal from output to input gave rise to the use of the term "feedback" as a distinct word by 1920.<ref name=bennett/>

By the end of 1912, researchers using early electronic amplifiers (audions) had discovered that deliberately coupling part of the output signal back to the input circuit would boost the amplification (through regeneration), but would also cause the audion to howl or sing. This action of feeding back of the signal from output to input gave rise to the use of the term "feedback" as a distinct word by 1920.

到1912年底，研究人员利用早期电子放大器(三极管)发现，故意将部分输出信号耦合回输入电路，会提高放大率(形成再生回路)，但也会使三极管发生啸叫。<ref name="bennett">{{Cite book|url=http://worldcat.org/isbn/0-906-04807-9|title=A history of control engineering, 1800–1930|author=Stuart Bennett|publisher=Peregrinus for the Institution of Electrical Engineers|year=1979|isbn=978-0-906048-07-8|location=Stevenage; New York}} </ref>这种将信号从输出反馈到输入的行为使得 "反馈 "一词在1920年被作为一个独立的词汇使用。<ref name=bennett/>

Over the years there has been some dispute as to the best definition of feedback. According to [[William Ross Ashby|Ashby]] (1956), mathematicians and theorists interested in the principles of feedback mechanisms prefer the definition of "circularity of action", which keeps the theory simple and consistent. For those with more practical aims, feedback should be a deliberate effect via some more tangible connection.

Over the years there has been some dispute as to the best definition of feedback. According to Ashby (1956), mathematicians and theorists interested in the principles of feedback mechanisms prefer the definition of "circularity of action", which keeps the theory simple and consistent. For those with more practical aims, feedback should be a deliberate effect via some more tangible connection.

多年来，关于反馈的最佳定义一直存在一些争议。根据阿什比 Ashby(1956)的说法。对反馈机制原理感兴趣的数学家和理论家倾向于用 "作用的循环性 "来定义反馈，这使理论保持简洁和一致。对于那些有更实际目的的人来说，反馈应该是具体过程产生的特定的影响。

{{Quote|[Practical experimenters] object to the mathematician's definition, pointing out that this would force them to say that feedback was present in the ordinary pendulum ... between its position and its momentum—a "feedback" that, from the practical point of view, is somewhat mystical. To this the mathematician retorts that if feedback is to be considered present only when there is an actual wire or nerve to represent it, then the theory becomes chaotic and riddled with irrelevancies.<ref name=Ashby>。{{cite book |author=W. Ross Ashby |title=An introduction to cybernetics |publisher=Chapman & Hall |year=1957 |url=http://pcp.vub.ac.be/books/IntroCyb.pdf}}</ref>{{rp|page=54}}}}

{{引言|[实际实验者]反对数学家的定义，指出这将迫使他们说普通的摆.中存在反馈.....在其位置和动量之间——这种 "反馈"，从实际的角度看，有些神秘。对此，数学家反驳说，如果只有用实际的导线或神经来表示反馈时，才认为反馈是存在的，那么这个理论就会变得混乱，充满了无关紧要的东西<ref name=Ashby>。{{cite book |author=W. Ross Ashby |title=An introduction to cybernetics |publisher=Chapman & Hall |year=1957 |url=http://pcp.vub.ac.be/books/IntroCyb.pdf}}</ref>{{rp|page=54}}}}

Focusing on uses in management theory, Ramaprasad (1983) defines feedback generally as "...information about the gap between the actual level and the reference level of a system parameter" that is used to "alter the gap in some way". He emphasizes that the information by itself is not feedback unless translated into action.<ref name="Ramaprasad">{{Cite journal | doi=10.1002/bs.3830280103|title = On the definition of feedback| journal=Behavioral Science| volume=28| pages=4–13|year = 1983|last1 = Ramaprasad|first1 = Arkalgud}}</ref>

Focusing on uses in management theory, Ramaprasad (1983) defines feedback generally as "...information about the gap between the actual level and the reference level of a system parameter" that is used to "alter the gap in some way". He emphasizes that the information by itself is not feedback unless translated into action.

拉马普拉萨德 Ramaprasad (1983)侧重于反馈在管理理论中的用途，他通常将反馈定义为"……关于系统参数的实际水平与参考水平之间差距的信息"，用于 "以某种方式改变差距"。他强调，信息本身不是反馈，转化为行动才是。<ref name="Ramaprasad">{{Cite journal | doi=10.1002/bs.3830280103|title = On the definition of feedback| journal=Behavioral Science| volume=28| pages=4-13|year = 1983|last1 = Ramaprasad|first1 = Arkalgud}}</ref>。

==Types==
类型

===Positive and negative feedback===
正反馈和负反馈

{{Main|Negative feedback|Positive feedback}}
主要|消极反馈|积极反馈

[[File:Set-point control.png|thumb|350px|Maintaining a desired system performance despite disturbance using negative feedback to reduce system error]]

[[File:Set-point control.png|thumb|350px|利用负反馈减少系统误差，在受到干扰的情况下仍能保持理想的系统性能]]

[[File:Outcome Feedback Negative Feedback Loop.png|thumb|An example of a negative feedback loop with goals]]

[[[File:Outcome Feedback Negative Feedback Loop.png|thumb|拇指|目标负反馈循环的示例]]

[[File:Process Feedback Loop.png|thumb|A positive feedback loop example]]
[[File：Process Feedback Loop.png | thumb |正反馈循环示例]]

Positive feedback: If the signal fed back from output is in phase with the input signal, the feedback is called positive feedback.

 正反馈 Positive feedback: 如果输出的反馈信号与输入信号同相，则称为正反馈。

Negative feedback: If the signal fed back is of opposite polarity or out of phase by 180° with respect to input signal, the feedback is called as negative feedback.

 负反馈 Negative feedback: 如果反馈信号与输入信号的极性相反或相位相差180°，则称为负反馈。

As an example of negative feedback, the diagram might represent a cruise control system in a car, for example, that matches a target speed such as the speed limit. The controlled system is the car; its input includes the combined torque from the engine and from the changing slope of the road (the disturbance). The car's speed (status) is measured by a speedometer. The error signal is the departure of the speed as measured by the speedometer from the target speed (set point). This measured error is interpreted by the controller to adjust the accelerator, commanding the fuel flow to the engine (the effector). The resulting change in engine torque, the feedback, combines with the torque exerted by the changing road grade to reduce the error in speed, minimizing the road disturbance.

该图表示的汽车中的巡航控制系统可以作为负反馈的一个例子，它使车速与目标速度(如车速限制)匹配。受控系统是汽车，其输入包括来自发动机和来自路面变化的坡度(干扰)的组合扭矩。汽车的速度(状态)由速度表测量。误差信号是速度计测量的速度与目标速度（设定点）的偏差。这个测量的误差由控制器来解译并以此来调整加速器，控制燃料流到发动机(效应器)。由此产生的发动机扭矩的变化，即反馈，与路面变化的坡度所施加的扭矩相结合，以减少速度误差，减少道路干扰。

The terms "positive" and "negative" were first applied to feedback prior to WWII. The idea of positive feedback was already current in the 1920s with the introduction of the [[regenerative circuit]].<ref name=mindell>{{Cite book|author=David A. Mindell|title=Between Human and Machine : Feedback, Control, and Computing before Cybernetics.|year= 2002|publisher=Johns Hopkins University Press|location=Baltimore, MD, US|url=https://books.google.com/books?id=sExvSbe9MSsC|isbn=9780801868955}}</ref>Friis and Jensen (1924) described regeneration in a set of electronic amplifiers as a case where ''the "feed-back" action is positive'' in contrast to negative feed-back action, which they mention only in passing.<ref name=friis>Friis, H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181–205.</ref> [[Harold Stephen Black]]'s classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:

The terms "positive" and "negative" were first applied to feedback prior to WWII. The idea of positive feedback was already current in the 1920s with the introduction of the regenerative circuit. Friis and Jensen (1924) described regeneration in a set of electronic amplifiers as a case where the "feed-back" action is positive in contrast to negative feed-back action, which they mention only in passing. Harold Stephen Black's classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:

“正面”和“负面”这两个词在第二次世界大战之前首次用于反馈。20世纪20年代，随着再生电路的引入，正反馈的概念已经流行起来。<ref name=mindell>{{Cite book|author=David A. Mindell|title=Between Human and Machine : Feedback, Control, and Computing before Cybernetics.|year= 2002|publisher=Johns Hopkins University Press|location=Baltimore, MD, US|url=https://books.google.com/books?id=sExvSbe9MSsC|isbn=9780801868955}}</ref> 弗里斯 Friis和延森 Jensen(1924)将一套电子放大器中的再生回路描述为"反馈"作用是正的例子，以此和他们顺便提及的负反馈作用相区别。<ref name=friis>Friis, H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181–205.</ref>哈罗德·史蒂芬·布莱克 Harold Stephen Black1934年的经典论文首次详细阐述了负反馈在电子放大器中的应用。布莱克认为:

{{Quote|Positive feed-back increases the gain of the amplifier, negative feed-back reduces it.<ref name=black>H.S. Black, "Stabilized feed-back amplifiers", ''Electrical Engineering'', vol. 53, pp. 114–120, January 1934.</ref>}}

{{Quote|正反馈增加放大器的增益，负反馈降低增益。<ref name=black>H.S. Black, "Stabilized feed-back amplifiers", ''Electrical Engineering'', vol. 53, pp. 114–120, January 1934.</ref>}}

According to Mindell (2002) confusion in the terms arose shortly after this:

据Mindell(2002年)说，在这之后不久就出现了术语上的混乱。

{{Quote|...Friis and Jensen had made the same distinction Black used between "positive feed-back" and "negative feed-back", based not on the sign of the feedback itself but rather on its effect on the amplifier's gain. In contrast, Nyquist and Bode, when they built on Black's work, referred to negative feedback as that with the sign reversed. Black had trouble convincing others of the utility of his invention in part because confusion existed over basic matters of definition.<ref name=mindell/>{{rp|page=121}}}}

{{Quote|...Friis和Jensen对Black在 "正反馈 "和 "负反馈 "之间的区分是一样的，不是基于反馈本身的符号，而是基于它对放大器增益的影响。相反，Nyquist和Bode在Black的工作基础上，将负反馈称为符号相反的反馈。布莱克难以说服其他人相信他的发明的实用性，因为再基本的概念上存在混乱。<ref name=mindell/>{{rp|page=121}}}}

Even prior to the terms being applied, [[James Clerk Maxwell]] had described several kinds of "component motions" associated with the [[centrifugal governor]]s used in steam engines, distinguishing between those that lead to a continual ''increase'' in a disturbance or the amplitude of an oscillation, and those that lead to a ''decrease'' of the same.<ref name=maxwell>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|url=http://en.wikipedia.org/wiki/File:On_Governors.pdf|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283|doi=10.1098/rspl.1867.0055|s2cid=51751195}}</ref>

Even prior to the terms being applied, James Clerk Maxwell had described several kinds of "component motions" associated with the centrifugal governors used in steam engines, distinguishing between those that lead to a continual ''increase'' in a disturbance or the amplitude of an oscillation, and those that lead to a ''decrease'' of the same.

甚至在这些术语被应用之前，詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell就已经描述了几种与蒸汽机中使用的离心式调速器相关的 "运动分量"，并区分了那些导致扰动或振荡幅度持续''增加''的运动和那些导致其减少的运动。 <ref name=maxwell>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|url=http://en.wikipedia.org/wiki/File:On_Governors.pdf|journal=Proceedings of the Royal Society of London|volume=16|year=1868|pages=270-283|doi=10.1098/rspl.1867}。 .0055|s2cid=51751195}}</ref>

====Terminology====
术语

The terms positive and negative feedback are defined in different ways within different disciplines.

正反馈和负反馈在不同的学科中有不同的定义。

# the altering of the ''gap'' between reference and actual values of a parameter, based on whether the gap is ''widening'' (positive) or ''narrowing'' (negative).<ref name="Ramaprasad" />

#the altering of the gap between reference and actual values of a parameter, based on whether the gap is widening (positive) or narrowing (negative).

# 根据差距是扩大（正）还是缩小（负）改变一个参数的参考值和实际值之间的差距；<ref name="Ramaprasad" />

# the [[Valence (psychology)|valence]] of the ''action'' or ''effect'' that alters the gap, based on whether it has a ''happy'' (positive) or ''unhappy'' (negative) emotional connotation to the recipient or observer.<ref name=herold1977>Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.</ref>

# the valence of the ''action'' or ''effect'' that alters the gap, based on whether it has a ''happy'' (positive) or ''unhappy'' (negative) emotional connotation to the recipient or observer.

#改变差距的行动或效果的 效价 valence，基于它对接受者或观察者是否具有''快乐''（积极）或''不快乐''（消极）的情感内涵。<ref name=herold1977>Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.</ref>

The two definitions may cause confusion, such as when an incentive (reward) is used to boost poor performance (narrow a gap). Referring to definition 1, some authors use alternative terms, replacing ''positive/negative'' with ''self-reinforcing/self-correcting'',<ref name="senge">{{Cite book|author=Peter M. Senge|title=The Fifth Discipline: The Art and Practice of the Learning Organization|year=1990|publisher=Doubleday|location=New York |isbn=978-0-385-26094-7|page=424|url=https://archive.org/details/fifthdisciplineasen00seng}}
</ref> ''reinforcing/balancing'',<ref name="sterman">John D. Sterman, ''Business Dynamics: Systems Thinking and Modeling for a Complex World'', McGraw Hill/Irwin, 2000. {{ISBN|978-0-07-238915-9}}</ref> ''discrepancy-enhancing/discrepancy-reducing''<ref name="carver">Charles S. Carver, Michael F. Scheier: ''On the Self-Regulation of Behavior'' Cambridge University Press, 2001 </ref> or ''regenerative/degenerative''<ref>Hermann A Haus and Richard B. Adler, ''Circuit Theory of Linear Noisy Networks'', MIT Press, 1959</ref>respectively. And for definition 2, some authors advocate describing the action or effect as positive/negative ''[[Reinforcement#Reinforcement|reinforcement]]'' or ''[[Reinforcement#Punishment|punishment]]'' rather than feedback.<ref name="Ramaprasad" /><ref name="skinner">BF Skinner, ''The Experimental Analysis of Behavior'', American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371</ref>Yet even within a single discipline an example of feedback can be called either positive or negative, depending on how values are measured or referenced.<ref>"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
For feedback in the educational context, see corrective feedback.
Ralph L. Levine, Hiram E. Fitzgerald. ''Analysis of the dynamic psychological systems: methods and applications'', {{ISBN|978-0306437465}} (1992) page 123</ref>

The two definitions may cause confusion, such as when an incentive (reward) is used to boost poor performance (narrow a gap). Referring to definition 1, some authors use alternative terms, replacing positive/negative with self-reinforcing/self-correcting, reinforcing/balancing, discrepancy-enhancing/discrepancy-reducing or regenerative/degenerative respectively. And for definition 2, some authors advocate describing the action or effect as positive/negative reinforcement or punishment rather than feedback. Yet even within a single discipline an example of feedback can be called either positive or negative, depending on how values are measured or referenced.

这两种定义可能会引起混淆，比如当激励(奖励)被用来提高糟糕的表现(缩小差距)。针对定义1，一些作者使用了替代术语，分别用自强化/自纠正<ref name="senge">{{Cite book|author=Peter M. Senge|title=The Fifth Discipline: The Art and Practice of the Learning Organization|year=1990|publisher=Doubleday|location=New York |isbn=978-0-385-26094-7|page=424|url=https://archive.org/details/fifthdisciplineasen00seng}}
</ref>、强化/平衡<ref name="sterman">John D. Sterman, ''Business Dynamics: Systems Thinking and Modeling for a Complex World'', McGraw Hill/Irwin, 2000. {{ISBN|978-0-07-238915-9}}</ref>、离散增强/离散减少<ref name="carver">Charles S. Carver, Michael F. Scheier: ''On the Self-Regulation of Behavior'' Cambridge University Press, 2001 </ref>或再生/退化<ref>Hermann A Haus and Richard B. Adler, ''Circuit Theory of Linear Noisy Networks'', MIT Press, 1959</ref>来替代正/负。对于定义2，一些作者主张将行为或效果描述为积极/消极的强化或惩罚，而不是反馈。<ref name="Ramaprasad" /><ref name="skinner">BF Skinner, ''The Experimental Analysis of Behavior'', American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371</ref>然而，即使是在一个单一的学科中，反馈的例子也可以被称为正的或负的，这取决于如何衡量或引用其含义。<ref>"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
For feedback in the educational context, see corrective feedback.
Ralph L. Levine, Hiram E. Fitzgerald. ''Analysis of the dynamic psychological systems: methods and applications'', {{ISBN|978-0306437465}} (1992) page 123</ref>

This confusion may arise because feedback can be used for either ''informational'' or ''motivational'' purposes, and often has both a ''[[Qualitative property|qualitative]]'' and a ''[[Quantitative property|quantitative]]'' component. As Connellan and Zemke (1993) put it:

This confusion may arise because feedback can be used for either informational or motivational purposes, and often has both a qualitative and a quantitative component. As Connellan and Zemke (1993) put it:

这种混淆可能会出现，因为反馈既可以用于信息的目的，也可以用于激励的目的，而且往往同时具有定性和定量的成分。正如康奈兰 Connellan和泽姆克 Zemke(1993)所言:

{{Quote|''Quantitative'' feedback tells us how much and how many. ''Qualitative'' feedback tells us how good, bad or indifferent.<ref name=Connellan>Thomas K. Connellan and Ron Zemke, "Sustaining Knock Your Socks Off Service" AMACOM, 1 July 1993. {{ISBN|0-8144-7824-7}}</ref>{{rp|page=102}}}}

{{Quote|''定量''反馈告诉我们多少。''定性''反馈告诉我们多好、多坏或二者之间。<ref name=Connellan>Thomas K. Connellan and Ron Zemke, "Sustaining Knock Your Socks Off Service" AMACOM, 1 July 1993. {{ISBN|0-8144-7824-7}}</ref>{{rp|page=102}}}}

====Limitations of negative and positive feedback====
正反馈和负反馈的限制

While simple systems can sometimes be described as one or the other type, many systems with feedback loops cannot be so easily designated as simply positive or negative, and this is especially true when multiple loops are present.

虽然单一系统有时可以被描述为一种或另一种类型，但许多具有反馈回路的系统不能简单地指定为正或负，尤其是存在多个回路时。

{{Quote|When there are only two parts joined so that each affects the other, the properties of the feedback give important and useful information about the properties of the whole. But when the parts rise to even as few as four, if every one affects the other three, then twenty circuits can be traced through them; and knowing the properties of all the twenty circuits does not give complete information about the system.<ref name=Ashby/>{{rp|page=54}}}}

{{Quote|当只有两个部分连接在一起，以至于每个部分都会影响到另一个部分时，反馈的属性就能提供关于整体属性的重要有用信息。但是，当部分增加到即使只有四个时，如果每一个都影响其他三个，那么就可以通过它们找到二十个回路；而知道所有这二十个回路的特性并不能提供有关系统的完整信息。<ref name=Ashby/>{{rp|page=54}}}}

===Other types of feedback===
其他反馈类型

In general, feedback systems can have many signals fed back and the feedback loop frequently contain mixtures of positive and negative feedback where positive and negative feedback can dominate at different frequencies or different points in the state space of a system.

一般来说，反馈系统可以有许多信号反馈，反馈回路中经常包含混合在一起的正反馈和负反馈，其中正反馈和负反馈可以在系统状态空间的不同频率或不同点占主导地位。

The term bipolar feedback has been coined to refer to biological systems where positive and negative feedback systems can interact, the output of one affecting the input of another, and vice versa.<ref name = Smit>{{cite book |title=Introduction to Bioregulatory Medicine |author1=Alta Smit |author2=Arturo O'Byrne |chapter-url=https://books.google.com/books?id=RzXAOUnCM3oC&pg=PA6 |page=6 |chapter=Bipolar feedback |isbn=9783131469717 |year=2011 |publisher=Thieme}}</ref>

术语 双极反馈 bipolar feedback 是指生物系统中正反馈系统和负反馈系统可以相互作用，一个系统的输出会影响另一个系统的输入，反之亦然。<ref name = Smit>{{cite book |title=Introduction to Bioregulatory Medicine |author1=Alta Smit |author2=Arturo O'Byrne |chapter-url=https://books.google.com/books?id=RzXAOUnCM3oC&pg=PA6 |page=6 |chapter=Bipolar feedback |isbn=9783131469717 |year=2011 |publisher=Thieme}}</ref>

Some systems with feedback can have very complex behaviors such as [[Chaos theory|chaotic behaviors]] in non-linear systems, while others have much more predictable behaviors, such as those that are used to make and design digital systems.

Some systems with feedback can have very complex behaviors such as chaotic behaviors in non-linear systems, while others have much more predictable behaviors, such as those that are used to make and design digital systems.

一些带有反馈的系统会有非常复杂的行为，比如非线性系统中的混沌行为，而另一些系统则有更多可预测的行为，比如那些用于制造和设计数字系统的系统。

Feedback is used extensively in digital systems. For example, binary counters and similar devices employ feedback where the current state and inputs are used to calculate a new state which is then fed back and clocked back into the device to update it.

反馈在数字系统中得到了广泛的应用。例如，二进制计数器和类似的设备采用了反馈，即利用当前的状态和输入来计算一个新的状态，然后反馈到设备并计时更新它。

==Applications==
应用

===Mathematics and dynamical systems===
数学和动力系统

[[File:Mandel zoom 00 mandelbrot set.jpg|322px|thumb|Feedback can give rise to incredibly complex behaviors. The [[Mandelbrot set]] (black) within a continuously colored environment is plotted by repeatedly feeding back values through a simple equation and recording the points on the imaginary plane that fail to diverge|alt=]]

[[File:Mandel zoom 00 mandelbrot set.jpg|322px|thumb|反馈可以产生令人难以置信的复杂行为。通过一个简单的方程反复反馈数值，并记录虚平面上未能偏离的点，绘制出连续着色环境中的 曼德尔布罗特集（布莱克） Mandelbrot set]] (black)。

{{Main|Dynamical system|Chaos theory|Edge of chaos|Control theory}}

{{主要|动力系统|混沌理论|混沌边缘|控制理论}}

By using feedback properties, the behavior of a system can be altered to meet the needs of an application; systems can be made stable, responsive or held constant. It is shown that dynamical systems with a feedback experience an adaptation to the [[edge of chaos]].<ref>{{cite journal|last1=Wotherspoon|first1=T.|last2=Hubler|first2=A.|title=Adaptation to the edge of chaos with random-wavelet feedback|journal=J. Phys. Chem. A|date=2009|doi=10.1021/jp804420g|pmid=19072712|volume=113|issue=1|pages=19–22|bibcode=2009JPCA..113...19W}}</ref>

By using feedback properties, the behavior of a system can be altered to meet the needs of an application; systems can be made stable, responsive or held constant. It is shown that dynamical systems with a feedback experience an adaptation to the edge of chaos.

通过使用反馈属性，可以更改系统的行为以满足应用程序的需求；可以使系统稳定、响应迅速或保持恒定。结果表明，具有反馈的动力系统会适应混沌边缘现象。<ref>{{cite journal|last1=Wotherspoon|first1=T.|last2=Hubler|first2=A.|title=Adaptation to the edge of chaos with random-wavelet feedback|journal=J. Phys. Chem. A|date=2009|doi=10.1021/jp804420g|pmid=19072712|volume=113|issue=1|pages=19–22|bibcode=2009JPCA..113...19W}}</ref>

===Biology===
生物

{{See also|Homeostasis|Allostasis}}
{{另请参见|内环境稳态|稳态}}

In [[biology|biological]] systems such as [[organism]]s, [[ecosystem]]s, or the [[biosphere]], most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal value of the controlled parameter can result from the changes in internal and external environments. A change of some of the environmental conditions may also require change of that range to change for the system to function. The value of the parameter to maintain is recorded by a reception system and conveyed to a regulation module via an information channel. An example of this is [[insulin oscillation]]s.

In biological systems such as organisms, ecosystems, or the biosphere, most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal value of the controlled parameter can result from the changes in internal and external environments. A change of some of the environmental conditions may also require change of that range to change for the system to function. The value of the parameter to maintain is recorded by a reception system and conveyed to a regulation module via an information channel. An example of this is insulin oscillations.

在生物体、生态系统或生物圈等生物系统中，大多数参数必须在特定环境下保持在以最佳水平为中心的小范围内。受控参数和最佳值之间的偏差可能是由于内外部环境的变化造成的。环境条件的变化，也需要改变参数变化的范围来维持系统的运行。受控参数的值由接收系统记录下来，并通过信息通道传达给调节模块。胰岛素振荡就是一个例子。

Biological systems contain many types of regulatory circuits, both positive and negative. As in other contexts, positive and negative do not imply that the feedback causes good or bad effects. A negative feedback loop is one that tends to slow down a process, whereas the positive feedback loop tends to accelerate it. The mirror neurons are part of a social feedback system, when an observed action is "mirrored" by the brain—like a self-performed action.

生物系统包含许多类型的调节回路，包括正向和负向。与其他情况一样，正负并不意味着反馈会造成好的或坏的影响。负反馈回路是一种倾向于减缓过程的回路，而正反馈回路则倾向于加速过程。镜像神经元是社会反馈系统的一部分，当观察到的行为被大脑“镜像”——就像一个自导自演的行为。

Normal tissue integrity is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted molecules that act as mediators; failure of key feedback mechanisms in cancer disrupts tissue function.<ref>{{cite journal|last1=Vlahopoulos|first1=SA|last2=Cen|first2=O|last3=Hengen|first3=N|last4=Agan|first4=J|last5=Moschovi|first5=M|last6=Critselis|first6=E|last7=Adamaki|first7=M|last8=Bacopoulou|first8=F|last9=Copland|first9=JA|last10=Boldogh|first10=I|last11=Karin|first11=M|last12=Chrousos|first12=GP|title=Dynamic aberrant NF-κB spurs tumorigenesis: A new model encompassing the microenvironment.|journal=Cytokine & Growth Factor Reviews|date=20 June 2015|pmid=26119834|doi=10.1016/j.cytogfr.2015.06.001|volume=26|issue=4|pages=389–403|pmc=4526340}}</ref> In an injured or infected tissue, inflammatory mediators elicit feedback responses in cells, which alter gene expression, and change the groups of molecules expressed and secreted, including molecules that induce diverse cells to cooperate and restore tissue structure and function. This type of feedback is important because it enables coordination of immune responses and recovery from infections and injuries. During cancer, key elements of this feedback fail. This disrupts tissue function and immunity.<ref>{{cite journal | last1 = Vlahopoulos | first1 = SA | title = Aberrant control of NF-κB in cancer permits transcriptional and phenotypic plasticity, to curtail dependence on host tissue: molecular mode. | journal = Cancer Biology & Medicine | date = August 2017 | pmid = 28884042 | doi = 10.20892/j.issn.2095-3941.2017.0029 | volume = 14 | issue = 3 | pages = 254–270 | pmc = 5570602}}</ref><ref>{{cite journal|last1=Korneev|first1=KV|last2=Atretkhany|first2=KN|last3=Drutskaya|first3=MS|last4=Grivennikov|first4=SI|last5=Kuprash|first5=DV|last6=Nedospasov|first6=SA|title=TLR-signaling and proinflammatory cytokines as drivers of tumorigenesis.|journal=Cytokine|date=January 2017|volume=89|pages=127–135|doi=10.1016/j.cyto.2016.01.021|pmid=26854213}}</ref>

Normal tissue integrity is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted molecules that act as mediators; failure of key feedback mechanisms in cancer disrupts tissue function.In an injured or infected tissue, inflammatory mediators elicit feedback responses in cells, which alter gene expression, and change the groups of molecules expressed and secreted, including molecules that induce diverse cells to cooperate and restore tissue structure and function. This type of feedback is important because it enables coordination of immune responses and recovery from infections and injuries. During cancer, key elements of this feedback fail. This disrupts tissue function and immunity.

正常组织的完整性是通过粘附分子和作为介质的分泌分子介导的不同细胞类型之间的反馈相互作用来保持的；癌症中关键反馈机制的失效会破坏组织功能。.<ref>{{cite journal|last1=Vlahopoulos|first1=SA|last2=Cen|first2=O|last3=Hengen|first3=N|last4=Agan|first4=J|last5=Moschovi|first5=M|last6=Critselis|first6=E|last7=Adamaki|first7=M|last8=Bacopoulou|first8=F|last9=Copland|first9=JA|last10=Boldogh|first10=I|last11=Karin|first11=M|last12=Chrousos|first12=GP|title=Dynamic aberrant NF-κB spurs tumorigenesis: A new model encompassing the microenvironment.|journal=Cytokine & Growth Factor Reviews|date=20 June 2015|pmid=26119834|doi=10.1016/j.cytogfr.2015.06.001|volume=26|issue=4|pages=389–403|pmc=4526340}}</ref>在受伤或感染的组织中，炎症介质会引起细胞的反馈反应，改变基因表达，改变细胞表达和分泌的分子群，包括诱导不同细胞合作的分子和恢复组织结构和功能的分子。这种类型的反馈很重要，因为它能够协调免疫反应、使机体从感染和损伤中恢复。在癌症过程中，这种反馈的关键要素会失效，进而破坏组织功能和免疫力。<ref>{{cite journal | last1 = Vlahopoulos | first1 = SA | title = Aberrant control of NF-κB in cancer permits transcriptional and phenotypic plasticity, to curtail dependence on host tissue: molecular mode. | journal = Cancer Biology & Medicine | date = August 2017 | pmid = 28884042 | doi = 10.20892/j.issn.2095-3941.2017.0029 | volume = 14 | issue = 3 | pages = 254–270 | pmc = 5570602}}</ref><ref>{{cite journal|last1=Korneev|first1=KV|last2=Atretkhany|first2=KN|last3=Drutskaya|first3=MS|last4=Grivennikov|first4=SI|last5=Kuprash|first5=DV|last6=Nedospasov|first6=SA|title=TLR-signaling and proinflammatory cytokines as drivers of tumorigenesis.|journal=Cytokine|date=January 2017|volume=89|pages=127–135|doi=10.1016/j.cyto.2016.01.021|pmid=26854213}}</ref>

Mechanisms of feedback were first elucidated in bacteria, where a nutrient elicits changes in some of their metabolic functions.<ref>{{cite journal|last1= Sanwal|first1=BD| title= Allosteric controls of amphilbolic pathways in bacteria.|journal= Bacteriol. Rev.|date=March 1970|volume=34|issue=1|pages=20–39 |pmid=4315011 |pmc=378347|doi=10.1128/MMBR.34.1.20-39.1970}}</ref>Feedback is also central to the operations of [[gene]]s and [[gene regulatory network]]s. [[Repressor protein|Repressor]] (see [[Lac repressor]]) and [[activator protein|activator]] [[protein]]s are used to create genetic [[operon]]s, which were identified by [[Francois Jacob]] and [[Jacques Monod]] in 1961 as ''feedback loops''.<ref>{{cite journal|last1= Jacob|first1=F|last2=Monod|first2=J|title= Genetic regulatory mechanisms in the synthesis of proteins.|journal= J Mol Biol|date=June 1961|volume=3|issue=3|pages=318–356 |pmid=13718526|doi=10.1016/S0022-2836(61)80072-7}}</ref> These feedback loops may be positive (as in the case of the coupling between a sugar molecule and the proteins that import sugar into a bacterial cell), or negative (as is often the case in [[metabolic]] consumption).

Mechanisms of feedback were first elucidated in bacteria, where a nutrient elicits changes in some of their metabolic functions.Feedback is also central to the operations of genes and gene regulatory networks. Repressor (see Lac repressor) and activator proteins are used to create genetic operons, which were identified by Francois Jacob and Jacques Monod in 1961 as feedback loops. These feedback loops may be positive (as in the case of the coupling between a sugar molecule and the proteins that import sugar into a bacterial cell), or negative (as is often the case in metabolic consumption).

反馈机制首次在细菌中得到阐明，是一种营养物质会引起其部分代谢功能的变化的机制。<ref>{{cite journal|last1= Sanwal|first1=BD| title= Allosteric controls of amphilbolic pathways in bacteria.|journal= Bacteriol. Rev.|date=March 1970|volume=34|issue=1|pages=20–39 |pmid=4315011 |pmc=378347|doi=10.1128/MMBR.34.1.20-39.1970}}</ref>反馈也是基因和基因调控网络运作的中心。用 阻遏蛋白 Repressor(参见 Lac 阻遏蛋白)和 激活蛋白 activator protein来创造 基因操纵子 genetic operons protein，这被弗朗索瓦·雅各布 Francois Jacob 和雅克·莫诺德 Jacques Monod 在1961年确定为反馈回路。<ref>{{cite journal|last1= Jacob|first1=F|last2=Monod|first2=J|title= Genetic regulatory mechanisms in the synthesis of proteins.|journal= J Mol Biol|date=June 1961|volume=3|issue=3|pages=318–356 |pmid=13718526|doi=10.1016/S0022-2836(61)80072-7}}</ref>这些反馈回路可能是正的(例如糖分子和将糖输入细菌细胞的蛋白质之间的结合) ，也可能是负的(例如代谢消耗中经常出现的情况)。

On a larger scale, feedback can have a stabilizing effect on animal populations even when profoundly affected by external changes, although time lags in feedback response can give rise to [[Lotka–Volterra equation|predator-prey cycles]].<ref>CS Holling. "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics 4:1-23. 1973</ref>

On a larger scale, feedback can have a stabilizing effect on animal populations even when profoundly affected by external changes, although time lags in feedback response can give rise to predator-prey cycles.

尽管反馈反应的时间滞后可能引起捕食者-猎物循环，在受到外部变化的深刻影响的情况下，反馈也能对动物种群产生稳定作用。<ref>CS Holling. "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics 4:1-23. 1973</ref>

In [[fermentation (biochemistry)|zymology]], feedback serves as regulation of activity of an enzyme by its direct {{Not a typo|product(s)}} or downstream {{Not a typo|metabolite(s)}} in the metabolic pathway (see [[Allosteric regulation]]).

In zymology, feedback serves as regulation of activity of an enzyme by its direct product(s) or downstream metabolite(s) in the metabolic pathway (see Allosteric regulation).

在酶学中，反馈在代谢途径中通过直接产物或的下游代谢产物来调节酶的活性(见''' 变构调节allosteric regulation ''')。

The [[hypothalamic–pituitary–adrenal axis]] is largely controlled by positive and negative feedback, much of which is still unknown.

The hypothalamic–pituitary–adrenal axis is largely controlled by positive and negative feedback, much of which is still unknown.

下丘脑-垂体-肾上腺在很大程度上受到正反馈和负反馈的控制，其中的机制很大程度上仍然未知。

In [[psychology]], the body receives a stimulus from the environment or internally that causes the release of [[hormone]]s. Release of hormones then may cause more of those hormones to be released, causing a positive feedback loop. This cycle is also found in certain behaviour. For example, "shame loops" occur in people who blush easily. When they realize that they are blushing, they become even more embarrassed, which leads to further blushing, and so on.<ref>{{cite magazine|last=Scheff |first=Thomas |url=http://www.psychologytoday.com/blog/lets-connect/200909/the-emotionalrelational-world |title=The Emotional/Relational World |magazine=Psychology Today |date=2009-09-02 |accessdate=2013-07-10}}</ref>

In psychology, the body receives a stimulus from the environment or internally that causes the release of hormones. Release of hormones then may cause more of those hormones to be released, causing a positive feedback loop. This cycle is also found in certain behaviour. For example, "shame loops" occur in people who blush easily. When they realize that they are blushing, they become even more embarrassed, which leads to further blushing, and so on.

在心理学中，身体接受来自环境或内部的刺激，从而导致激素的释放。然后，激素的释放可能会导致更多的激素被释放，从而形成正反馈循环。这种循环也存在于某些行为中。例如，容易脸红的人就会出现 "羞耻循环"。当他们意识到自己脸红的时候，他们会变得更加尴尬，从而导致进一步的脸红，等等。<ref>{{cite magazine|last=Scheff |first=Thomas |url=http://www.psychologytoday.com/blog/lets-connect/200909/the-emotionalrelational-world |title=The Emotional/Relational World |magazine=Psychology Today |date=2009-09-02 |accessdate=2013-07-10}}</ref>

===Climate science===
气候科学

{{Main|Climate change feedback}}
{{主要|气候变化反馈}}

The climate system is characterized by strong positive and negative feedback loops between processes that affect the state of the atmosphere, ocean, and land. A simple example is the [[Ice-albedo feedback|ice-albedo positive feedback]] loop whereby melting snow exposes more dark ground (of lower [[albedo]]), which in turn absorbs heat and causes more snow to melt.

The climate system is characterized by strong positive and negative feedback loops between processes that affect the state of the atmosphere, ocean, and land. A simple example is the ice-albedo positive feedback loop whereby melting snow exposes more dark ground (of lower albedo), which in turn absorbs heat and causes more snow to melt.

气候系统的特点是，影响大气、海洋和陆地状态的过程之间存在着强烈的正负反馈回路。一个简单的例子是冰-反射率正反馈环路，即雪的融化使更多的黑暗地面(反射率较低)暴露出来，反过来吸收热量，使更多的雪融化。

===Control theory===
控制理论

{{Main|Control theory}}
{{主要|控制理论}}

Feedback is extensively used in control theory, using a variety of methods including [[state space (controls)]], [[full state feedback]], and so forth. Note that in the context of control theory, "feedback" is traditionally assumed to specify "negative feedback".<ref name=mees>''"There is a tradition in control theory that one deals with a ''negative feedback loop'' in which a negative sign is included in the feedback loop..."'' A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981. {{ISBN|0-471-27822-X}}. p69</ref>

Feedback is extensively used in control theory, using a variety of methods including state space (controls), full state feedback, and so forth. Note that in the context of control theory, "feedback" is traditionally assumed to specify "negative feedback".

反馈广泛应用于控制理论中，使用的方法很多，包括状态矢量空间（控制）、全状态反馈等。需要注意的是，在控制理论的背景下，“反馈”通常特指“负反馈”。<ref name=mees>''"There is a tradition in control theory that one deals with a ''negative feedback loop'' in which a negative sign is included in the feedback loop..."'' A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981. {{ISBN|0-471-27822-X}}. p69</ref>

{{Further|PID controller}}

{{进一步|PID控制器}}。、

The most common general-purpose [[controller (control theory)|controller]] using a control-loop feedback mechanism is a [[PID controller|proportional-integral-derivative]] (PID) controller. Heuristically, the terms of a PID controller can be interpreted as corresponding to time: the proportional term depends on the ''present'' error, the integral term on the accumulation of ''past'' errors, and the derivative term is a prediction of ''future'' error, based on current rate of change.<ref>{{Citation | url = http://www.eolss.net/ebooks/Sample%20Chapters/C18/E6-43-03-03.pdf | title = PID Control | last = Araki | first = M. }}</ref>

The most common general-purpose controller using a control-loop feedback mechanism is a proportional-integral-derivative (PID) controller. Heuristically, the terms of a PID controller can be interpreted as corresponding to time: the proportional term depends on the present error, the integral term on the accumulation of past errors, and the derivative term is a prediction of future error, based on current rate of change.

最常见的采用控制回路反馈机制的通用控制器是比例-积分-导数（PID）控制器。从启发式的角度看，PID控制器的项可以解释为与时间相对应：比例项取决于现在的误差，积分项取决于过去误差的积累，而导数项则是根据当前的变化率，对未来误差进行预测。<ref>{{Citation | url = http://www.eolss.net/ebooks/Sample%20Chapters/C18/E6-43-03-03.pdf | title = PID Control | last = Araki | first = M. }}</ref>

===Education===
教育

For feedback in the educational context, see [[corrective feedback]].
For feedback in the educational context, see corrective feedback.

关于教育方面的反馈，见纠正性反馈。

===Mechanical engineering===
机械工程

In ancient times, the [[float valve]] was used to regulate the flow of water in Greek and Roman [[water clock]]s; similar float valves are used to regulate fuel in a [[carburettor]] and also used to regulate tank water level in the [[flush toilet]].

In ancient times, the float valve was used to regulate the flow of water in Greek and Roman water clocks; similar float valves are used to regulate fuel in a carburettor and also used to regulate tank water level in the flush toilet.

在古代，浮阀被用来调节希腊和罗马水钟的水流; 类似的浮阀被用来调节化油器的燃料，也被用来调节抽水马桶的水位。

The Dutch inventor [[Cornelius Drebbel]] (1572-1633) built thermostats (c1620) to control the temperature of chicken incubators and chemical furnaces. In 1745, the windmill was improved by blacksmith Edmund Lee, who added a [[windmill fantail|fantail]] to keep the face of the windmill pointing into the wind. In 1787, [[Tom Mead]] regulated the rotation speed of a windmill by using a [[conical pendulum|centrifugal pendulum]] to adjust the distance between the bedstone and the runner stone (i.e., to adjust the load).

The Dutch inventor Cornelius Drebbel (1572-1633) built thermostats (c1620) to control the temperature of chicken incubators and chemical furnaces. In 1745, the windmill was improved by blacksmith Edmund Lee, who added a fantail to keep the face of the windmill pointing into the wind. In 1787, Tom Mead regulated the rotation speed of a windmill by using a centrifugal pendulum to adjust the distance between the bedstone and the runner stone (i.e., to adjust the load).

荷兰发明家克尼利厄斯·雅布斯纵·戴博尔 Cornelius Drebbel (1572-1633)制造了恒温器(c1620)用于控制鸡的孵化器和化学炉的温度。1745年，铁匠埃德蒙·李 Edmund Lee对风车进行了改进，他增加了一个扇形尾翼，使风车的正面始终面向风。1787年，汤姆·米德Tom Mead通过使用离心摆调节基石和动石之间的距离(即调节负荷)来调节风车的转速。

The use of the [[centrifugal governor]] by [[James Watt]] in 1788 to regulate the speed of his [[steam engine]] was one factor leading to the [[Industrial Revolution]]. Steam engines also use float valves and [[relief valve|pressure release valves]] as mechanical regulation devices. A [[mathematical analysis]] of Watt's governor was done by [[James Clerk Maxwell]] in 1868.<ref name=maxwell/>

The use of the centrifugal governor by James Watt in 1788 to regulate the speed of his steam engine was one factor leading to the Industrial Revolution. Steam engines also use float valves and pressure release valves as mechanical regulation devices. A mathematical analysis of Watt's governor was done by James Clerk Maxwell in 1868.

1788年，詹姆斯·瓦特 James Watt 使用离心调速器来调节他的蒸汽机的速度是导致工业革命的一个因素。蒸汽发动机也使用浮阀和泄压阀作为机械调节装置。詹姆斯·克拉克·麦克斯韦 James Clerk Maxwell在1868年对Watt的调节器进行了数学分析。<ref name=maxwell/>

The ''[[SS Great Eastern|Great Eastern]]'' was one of the largest steamships of its time and employed a steam powered rudder with feedback mechanism designed in 1866 by [[John McFarlane Gray]]. [[Joseph Farcot]] coined the word ''[[Servomechanism|servo]]'' in 1873 to describe steam-powered steering systems. Hydraulic servos were later used to position guns. [[Elmer Ambrose Sperry]] of the [[Sperry Corporation]] designed the first [[autopilot]] in 1912. [[Nicolas Minorsky]] published a theoretical analysis of automatic ship steering in 1922 and described the [[PID controller]].<ref name="Minorsky">{{cite journal |author=Minorsky, Nicolas |year=1922 |title=Directional stability of automatically steered bodies |journal=J. Amer. Soc of Naval Engineers |volume=34 |issue= 2|pages=280–309 |doi= 10.1111/j.1559-3584.1922.tb04958.x}}</ref>

The 'Great Eastern'' was one of the largest steamships of its time and employed a steam powered rudder with feedback mechanism designed in 1866 by John McFarlane Gray. Joseph Farcot coined the word ''servo'' in 1873 to describe steam-powered steering systems. Hydraulic servos were later used to position guns. Elmer Ambrose Sperry of the Sperry Corporation designed the first autopilot in 1912. Nicolas Minorsky published a theoretical analysis of automatic ship steering in 1922 and described the PID controller.

“Great Eastern”是当时最大的汽轮之一，采用了由[[约翰·麦克法兰·格雷 John McFarlane Gray]]在1866年设计的带有反馈机制的蒸汽舵。约瑟夫·法尔科 [Joseph Farcot在1873年创造了“ 伺服系统 servo”一词来描述蒸汽动力转向系统，后来伺服系统被用来定位喷枪。斯佩里公司 Sperry Corporatio的[埃尔默·安布罗斯·斯佩里Elmer Ambrose Sperry在1912年设计了的第一台自动驾驶仪 autopilot。尼古拉斯·米诺尔斯基 Nicolas Minorsky在1922年发表了关于自动船舶操纵的理论分析，并描述了PID控制器。<ref name="Minorsky">{{cite journal |author=Minorsky, Nicolas |year=1922 |title=Directional stability of automatically steered bodies |journal=J. Amer. Soc of Naval Engineers |volume=34 |issue= 2|pages=280–309 |doi= 10.1111/j.1559-3584.1922.tb04958.x}}</ref>

Internal combustion engines of the late 20th century employed mechanical feedback mechanisms such as the [[Ignition timing#Vacuum timing advance|vacuum timing advance]] but mechanical feedback was replaced by electronic [[engine control unit|engine management systems]] once small, robust and powerful single-chip [[microcontroller]]s became affordable.

Internal combustion engines of the late 20th century employed mechanical feedback mechanisms such as the vacuum timing advance but mechanical feedback was replaced by electronic engine management systems once small, robust and powerful single-chip microcontrollers became affordable.

20世纪后期的内燃机采用了机械反馈机制，如真空定时推进，但当小型、坚固和功能强大的单片机变得经济实惠后，机械反馈就被电子发动机管理系统所取代。

===Electronic engineering===
电子工程

[[File:Ideal feedback model.svg|thumb|The simplest form of a feedback amplifier can be represented by the ''ideal block diagram'' made up of [https://www.google.com/search?tbo=p&tbm=bks&q=%22A+unilateral+block+or+network+is+one+in+which+power+may+be+transmitted+in+one+direction+only.%22&num=10&gws_rd=ssl unilateral elements].<ref name="Chen">{{cite book|title=Circuit Analysis and Feedback Amplifier Theory|author=Wai-Kai Chen|publisher=CRC Press|year=2005|isbn=9781420037272|location=423825181|pages=13–1|chapter=Chapter 13: General feedback theory|quote=[In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.|chapter-url=https://books.google.com/books?id=ZlJM1OLDQx0C&pg=SA13-PA1}}
</ref>|280px|right]]

[[File:Ideal feedback model.svg|thumb|反馈放大器的最简单形式可以用由单向元件组成的“理想框图”来表示。<ref name="Chen">{{cite book|title=Circuit Analysis and Feedback Amplifier Theory|author=Wai-Kai Chen|publisher=CRC Press|year=2005|isbn=9781420037272|location=423825181|pages=13–1|chapter=Chapter 13: General feedback theory|quote=[In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.|chapter-url=https://books.google.com/books?id=ZlJM1OLDQx0C&pg=SA13-PA1}}
</ref>|280px|right]]

The use of feedback is widespread in the design of [[electronics|electronic]] components such as [[amplifier]]s, [[oscillator]]s, and stateful [[logic circuit]] elements such as [[flip-flop (electronics)|flip-flop]]s and [[counter (digital)|counter]]s. Electronic feedback systems are also very commonly used to control mechanical, thermal and other physical processes.

The use of feedback is widespread in the design of electronic components such as amplifiers, oscillators, and stateful logic circuit elements such as flip-flops and counters. Electronic feedback systems are also very commonly used to control mechanical, thermal and other physical processes.

反馈在电子元件设计中的应用非常广泛，例如放大器、振荡器和有状态逻辑电路元件，例如触发器和计数器。电子反馈系统也常用于控制机械，热和其他物理过程。

If the signal is inverted on its way round the control loop, the system is said to have ''[[negative feedback amplifier|negative feedback]]'';<ref name=KalS>{{cite book |title=Basic Electronics: Devices, Circuits and IT Fundamentals |author=Santiram Kal |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+called+negative+feedback%22+%22if+the+feedback+signal+reduces+the+input+signal%22&pg=PA191 |quote=If the feedback signal reduces the input signal, ''i.e.'' it is out of phase with the input [signal], it is called negative feedback. |isbn=9788120319523 |year=2009 |publisher=PHI Learning Pvt. Ltd |page=191}}</ref> otherwise, the feedback is said to be ''positive''. Negative feedback is often deliberately introduced to increase the [[BIBO stability|stability]] and accuracy of a system by correcting or reducing the influence of unwanted changes. This scheme can fail if the input changes faster than the system can respond to it. When this happens, the lag in arrival of the correcting signal can result in over-correction, causing the output to [[oscillation|oscillate]] or "hunt".<ref>With mechanical devices, hunting can be severe enough to destroy the device.</ref> While often an unwanted consequence of system behaviour, this effect is used deliberately in electronic oscillators.

If the signal is inverted on its way round the control loop, the system is said to have negative feedback; otherwise, the feedback is said to be positive. Negative feedback is often deliberately introduced to increase the stability and accuracy of a system by correcting or reducing the influence of unwanted changes. This scheme can fail if the input changes faster than the system can respond to it. When this happens, the lag in arrival of the correcting signal can result in over-correction, causing the output to oscillate or "hunt". While often an unwanted consequence of system behaviour, this effect is used deliberately in electronic oscillators.

如果信号在绕过控制环路的过程中发生了反转，则称系统有负反馈；<ref name=KalS>{{cite book |title=Basic Electronics: Devices, Circuits and IT Fundamentals |author=Santiram Kal |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+called+negative+feedback%22+%22if+the+feedback+signal+reduces+the+input+signal%22&pg=PA191 |quote=If the feedback signal reduces the input signal, ''i.e.'' it is out of phase with the input [signal], it is called negative feedback. |isbn=9788120319523 |year=2009 |publisher=PHI Learning Pvt. Ltd |page=191}}</ref>否则，称反馈为正反馈。负反馈常常被刻意引入，通过纠正或减少不需要的变化的影响来提高系统的稳定性和准确性如果输入的变化速度快于系统对它的响应速度，这种方案就会失效。当这种情况发生时，校正信号到达的滞后可能导致过度校正，导致输出振荡或“捕获”。<ref>With mechanical devices, hunting can be severe enough to destroy the device.</ref>虽然这种效应通常是系统行为不希望出现的结果，但它却被有意地用于电子振荡器中。

[[Harry Nyquist]] at [[Bell Labs]] derived the [[Nyquist stability criterion]] for determining the stability of feedback systems. An easier method, but less general, is to use [[Bode plot]]s developed by [[Hendrik Wade Bode|Hendrik Bode]] to determine the [[Gain margin|gain margin and phase margin]]. Design to ensure stability often involves [[frequency compensation]] to control the location of the [[pole (complex analysis)|pole]]s of the amplifier.

Harry Nyquist at Bell Labs derived the Nyquist stability criterion for determining the stability of feedback systems. An easier method, but less general, is to use Bode plots developed by Hendrik Bode to determine the gain margin and phase margin. Design to ensure stability often involves frequency compensation to control the location of the poles of the amplifier.

贝尔实验室的哈里·奈奎斯特 Harry Nyquist 推导出了判定反馈系统稳定性的 奈奎斯特稳定判据 Nyquist stability criterion Chaos theory。一个比较简单但不太常用的方法是使用亨德里克博德 Hendrikbode 开发的 Bode 图来确定增益裕度和相位裕度。保证稳定性的设计往往使用频率补偿来控制放大器的极点位置。

Electronic feedback loops are used to control the output of [[electronics|electronic]] devices, such as [[amplifiers]]. A feedback loop is created when all or some portion of the output is fed back to the input. A device is said to be operating ''open loop'' if no output feedback is being employed and ''closed loop'' if feedback is being used.<ref>P. Horowitz & W. Hill, ''The Art of Electronics'', Cambridge University Press (1980), Chapter 3, relating to operational amplifiers.</ref>

Electronic feedback loops are used to control the output of electronic devices, such as amplifiers. A feedback loop is created when all or some portion of the output is fed back to the input. A device is said to be operating open loop if no output feedback is being employed and closed loop if feedback is being used.

电子反馈回路用于控制电子设备的输出，如放大器。当所有或部分输出反馈到输入时，就形成了一个反馈回路。如果没有采用输出反馈，则称为开环运行，如果采用反馈，则称为闭环运行。<ref>P. Horowitz & W. Hill, ''The Art of Electronics'', Cambridge University Press (1980), Chapter 3, relating to operational amplifiers.</ref>

When two or more amplifiers are cross-coupled using positive feedback, complex behaviors can be created. These ''[[multivibrator]]s'' are widely used and include:

When two or more amplifiers are cross-coupled using positive feedback, complex behaviors can be created. These multivibrators are widely used and include:

当两个或两个以上的放大器使用正反馈进行交叉耦合时，可以产生复杂的行为。这些多谐振荡器被广泛使用，包括:

* astable circuits, which act as oscillators
*非稳态电路，作为振荡器使用

* monostable circuits, which can be pushed into a state, and will return to the stable state after some time
* 单稳态电路，可以将其推入一个状态，并在一段时间后恢复到稳定状态。

* bistable circuits, which have two stable states that the circuit can be switched between
* 双稳态电路，它有两个稳定的状态，电路可以在这两个状态之间切换。

====Negative feedback====
负反馈

A Negative feedback occurs when the fed-back output signal has a relative phase of 180° with respect to the input signal (upside down). This situation is sometimes referred to as being ''out of phase'', but that term also is used to indicate other phase separations, as in "90° out of phase". Negative feedback can be used to correct output errors or to desensitize a system to unwanted fluctuations.<ref name=Bhattacharya>For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}</ref> In feedback amplifiers, this correction is generally for waveform [[distortion]] reduction{{citation needed|date=October 2014}} or to establish a specified [[Gain (electronics)|gain]] level. A general expression for the gain of a negative feedback amplifier is the [[asymptotic gain model]].

A Negative feedback occurs when the fed-back output signal has a relative phase of 180° with respect to the input signal (upside down). This situation is sometimes referred to as being out of phase, but that term also is used to indicate other phase separations, as in "90° out of phase". Negative feedback can be used to correct output errors or to desensitize a system to unwanted fluctuations. In feedback amplifiers, this correction is generally for waveform distortion reduction or to establish a specified gain level. A general expression for the gain of a negative feedback amplifier is the asymptotic gain model.

当反馈的输出信号相对于输入信号有180°的相对相位（上下颠倒）时，就会出现负反馈。这种情况有时被称为失相，但该术语也用于表示其他相位分离，如 "90°失相"。负反馈可用于纠正输出误差或使系统对不需要的波动脱敏。<ref name=Bhattacharya>For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}</ref>在反馈放大器中，这种校正一般是为了减少波形失真或建立一个指定的增益水平。负反馈放大器的增益的一般表达式是渐进增益模型。

====Positive feedback====
正反馈

Positive feedback occurs when the fed-back signal is in phase with the input signal. Under certain gain conditions, positive feedback reinforces the input signal to the point where the output of the device [[oscillates]] between its maximum and minimum possible states. Positive feedback may also introduce [[hysteresis]] into a circuit. This can cause the circuit to ignore small signals and respond only to large ones. It is sometimes used to eliminate noise from a digital signal. Under some circumstances, positive feedback may cause a device to latch, i.e., to reach a condition in which the output is locked to its maximum or minimum state. This fact is very widely used in digital electronics to make [[Flip-flop (electronics)|bistable]] circuits for volatile storage of information.

Positive feedback occurs when the fed-back signal is in phase with the input signal. Under certain gain conditions, positive feedback reinforces the input signal to the point where the output of the device oscillates between its maximum and minimum possible states. Positive feedback may also introduce hysteresis into a circuit. This can cause the circuit to ignore small signals and respond only to large ones. It is sometimes used to eliminate noise from a digital signal. Under some circumstances, positive feedback may cause a device to latch, i.e., to reach a condition in which the output is locked to its maximum or minimum state. This fact is very widely used in digital electronics to make bistable circuits for volatile storage of information.

当反馈信号与输入信号同相时，就会产生正反馈。在一定的增益条件下，正反馈增强输入信号，使器件的输出在其最大和最小可能状态之间振荡。正反馈也可能在电路中引入滞后现象。这会导致电路忽略小信号，只响应大信号。它有时被用来消除数字信号中的噪声。在某些情况下，正反馈可能导致设备闭锁，即，达到将输出锁定到其最大或最小状态的条件。这个功能在数字电子产品中被广泛应用于制作双稳态电路，用于信息的易失性存储。

The loud squeals that sometimes occurs in [[audio system]]s, [[public address system|PA systems]], and [[rock music]] are known as [[audio feedback]]. If a microphone is in front of a loudspeaker that it is connected to, sound that the microphone picks up comes out of the speaker, and is picked up by the microphone and re-amplified. If the [[loop gain]] is sufficient, howling or squealing at the maximum power of the amplifier is possible.

The loud squeals that sometimes occurs in audio systems, PA systems, and rock music are known as audio feedback. If a microphone is in front of a loudspeaker that it is connected to, sound that the microphone picks up comes out of the speaker, and is picked up by the microphone and re-amplified. If the loop gain is sufficient, howling or squealing at the maximum power of the amplifier is possible.

音响系统、扩音系统和摇滚音乐中有时会出现的响亮的尖叫声，这就是所谓的音频反馈。如果话筒在它所连接的扬声器前，话筒接收的声音就会从扬声器中传出，并被话筒结束并再次放大。如果环路增益足够，在放大器的最大功率下就可以发出啸叫或尖叫声。

====Oscillator====
振荡器

[[File:OpAmpHystereticOscillator.svg|thumb|A popular [[Relaxation oscillator#Comparator–based electronic relaxation oscillator|op-amp relaxation oscillator]].]]

[[File:OpAmpHystereticOscillator.svg|thumb|一个流行的运放弛缓振荡器]]。

An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. Oscillators convert direct current (DC) from a power supply to an alternating current signal. They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, and the sounds produced by electronic beepers and video games.

电子振荡器是一种产生周期性的、振荡信号的电子电路，通常是正弦波或方波。振荡器将电源中的直流电（DC）转换为交流信号。振荡器被广泛应用于许多电子设备中。振荡器产生的信号的常见例子包括无线电和电视发射机广播的信号，调节计算机和石英钟的时钟信号，以及电子传呼机和视频游戏产生的声音。

====Lactches and flip-flops====

A 4-bit [[ring counter using D-type flip flops]]

4位的使用d型触发器的环形计数器

A latch or a flip-flop is a circuit that has two stable states and can be used to store state information. They typically constructed using feedback that crosses over between two arms of the circuit, to provide the circuit with a state. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic. Latches and flip-flops are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems.

锁存器或触发器是具有两个稳定状态的电路，可用于存储状态信息。它们通常利用两臂电路之间交叉的反馈来构造，为电路提供一个状态。该电路可以通过施加到一个或多个控制输入的信号来改变状态，产生一个或两个输出。它是时序逻辑电路的基本存储元素。锁存器和触发器是用于计算机、通信和许多其他类型系统的数字电子系统的基本构件。

Latches and flip-flops are used as data storage elements. Such data storage can be used for storage of state, and such a circuit is described as sequential logic. When used in a finite-state machine, the output and next state depend not only on its current input, but also on its current state (and hence, previous inputs). It can also be used for counting of pulses, and for synchronizing variably-timed input signals to some reference timing signal.

锁存器和触发器用作数据存储元件。这样的数据存储可以用来存储状态，这样的电路被描述为时序逻辑电路。当用于有限状态机时，输出和下一状态不仅取决于其当前输入，还取决于其当前状态(因而也取决于以前的输入)。它也可用于脉冲的计数，以及将可变时序输入信号同步到某个参考时序信号。

Flip-flops can be either simple (transparent or opaque) or clocked (synchronous or edge-triggered). Although the term flip-flop has historically referred generically to both simple and clocked circuits, in modern usage it is common to reserve the term flip-flop exclusively for discussing clocked circuits; the simple ones are commonly called latches.

触发器可以是简单的(透明的或者不透明的)或者是计时的(同步的或者边缘触发的)。虽然触发器这个术语在历史上一直泛指简单电路和时钟电路，但在现代用法中，通常将触发器这个术语专门用于讨论时钟电路，简单的电路通常称为锁存电路。

Using this terminology, a latch is level-sensitive, whereas a flip-flop is edge-sensitive. That is, when a latch is enabled it becomes transparent, while a flip flop's output only changes on a single type (positive going or negative going) of clock edge.

使用这个术语，锁存器是电平敏感的，而触发器是边缘敏感的。也就是说，当锁存器启用时，它变得透明，而触发器的输出只在时钟边缘的单一类型(正向或负向)上发生变化。

Feedback loops provide generic mechanisms for controlling the running, maintenance, and evolution of software and computing systems. Feedback-loops are important models in the engineering of adaptive software, as they define the behaviour of the interactions among the control elements over the adaptation process, to guarantee system properties at run-time. Feedback loops and foundations of control theory have been successfully applied to computing systems. In particular, they have been applied to the development of products such as IBM's Universal Database server and IBM Tivoli. From a software perspective, the autonomic (MAPE, monitor analyze plan execute) loop proposed by researchers of IBM is another valuable contribution to the application of feedback loops to the control of dynamic properties and the design and evolution of autonomic software systems.

反馈回路为控制软件和计算系统的运行、维护和升级提供了通用机制。反馈回路是自适应软件工程中的重要模型，它定义了自适应过程中控制元件之间相互作用的行为，以保证系统在运行时的性能。反馈环路和控制理论基础已成功地应用于计算系统。特别是，它们已经应用于产品的开发，如IBM的Universal Database server和IBM Tivoli。从软件的角度来看，IBM 研究人员提出的自主(MAPE，monitor analyze plan execute)回路是对反馈回路应用于动态特性控制和自主软件系统设计与演化的又一宝贵贡献。

Feedback is also a useful design principle for designing user interfaces.

反馈也是设计用户界面时一个有用的设计原则。

Video feedback is the video equivalent of acoustic feedback. It involves a loop between a video camera input and a video output, e.g., a television screen or monitor. Aiming the camera at the display produces a complex video image based on the feedback.

视频反馈是相当于声音反馈的视频。它涉及到摄像机输入和视频输出（如电视屏幕或显示器）之间的循环。将摄像机对准显示器，会生成基于反馈的复杂的视频图像。

The stock market is an example of a system prone to oscillatory "hunting", governed by positive and negative feedback resulting from cognitive and emotional factors among market participants. For example:

股市是一个易于出现振荡 "捕猎"的系统的例子，它受市场参与者之间的认知和情感因素所产生的正负反馈所支配。例如：

George Soros used the word reflexivity, to describe feedback in the financial markets and developed an investment theory based on this principle.

乔治•索罗斯 George Soros 用“ 反身性 reflexivity servo”一词来描述金融市场的反馈，并根据这一原则发展了一套投资理论。

The conventional economic equilibrium model of supply and demand supports only ideal linear negative feedback and was heavily criticized by Paul Ormerod in his book The Death of Economics, which, in turn, was criticized by traditional economists. This book was part of a change of perspective as economists started to recognise that chaos theory applied to nonlinear feedback systems including financial markets.

传统的经济供求平衡模型只支持理想的线性负反馈，保罗·奥默罗德 Paul Ormerod在他的《经济学之死》一书中对这个模型提出了严厉的批评，而传统经济学家也对她提出了批评。随着经济学家开始认识到混沌理论适用于包括金融市场在内的非线性反馈系统，这本书成为了转变观点的一部分。

反馈

2020-11-29T16:41:28Z

WildBoar：

本词条由11初步翻译

https://wiki.swarma.org/index.php?title=%E5%B9%B3%E8%A1%A1%E7%90%86%E8%AE%BA#:~:text=%E6%9C%AC%E8%AF%8D%E6%9D%A1%E7%94%B1,11%E5%88%9D%E6%AD%A5%E7%BF%BB%E8%AF%91

{{Other uses}}
其他用途

{{short description|Process where information about current status is used to influence future status}}
简述|利用当前状态信息影响未来状态的过程

{{Use dmy dates|date=September 2020}}
使用dmy日期|日期=2020年9月

{{Complex systems}}[[File:General Feedback Loop.svg|thumb|A feedback loop where all outputs of a process are available as causal inputs to that process]]

A feedback loop where all outputs of a process are available as causal inputs to that process

一个过程的所有输出都可作为该过程的因果输入的反馈回路。

'''Feedback''' occurs when outputs of a system are routed back as inputs as part of a [[Signal chain (signal processing chain)|chain]] of [[Causality|cause-and-effect]] that forms a circuit or loop.<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref> The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:

Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:

当一个系统的输出作为输入被送回，并作为形成回路或循环的因果链的一部分时，就会产生 反馈 feedback。<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref>这个系统可以说是反馈到了自身。在应用于反馈系统时，必须谨慎处理因果关系的概念。

{{quote
|text=Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole.
|author=Karl Johan Åström and Richard M.Murray
|title=''Feedback Systems: An Introduction for Scientists and Engineers''<ref>{{cite book |title=Feedback Systems: An Introduction for Scientists and Engineers |author1=Karl Johan Åström |author2=Richard M. Murray |chapter=§1.1: What is feedback? |chapter-url=https://books.google.com/books?id=cdG9fNqTDS8C&q=%22This+makes+reasoning+based+on+cause+and+effect+tricky%22&pg=PA1 |isbn= 9781400828739 |year=2008 |page=1 |publisher=Princeton University Press}} Online version found [http://authors.library.caltech.edu/25062/1/Feedback08.pdf here].</ref>}}

{{quote
|text=Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole.
|author=Karl Johan Åström and Richard M.Murray
|title=Feedback Systems: An Introduction for Scientists and Engineers}}

{{引用
对于一个反馈系统，很难进行简单的因果推理，因为第一个系统影响第二个系统，第二个系统影响第一个系统，导致了一个循环论证。这就使得基于因果关系的推理变得很困难，因此有必要将系统作为一个整体进行分析。
|作者:卡尔·约翰·阿斯特洛姆 · 马丁 Karl Johan Åström和查德 · M · 默里 Richard M.Murray
| title = 反馈系统: 科学家和工程师介绍<ref>{{cite book |title=Feedback Systems: An Introduction for Scientists and Engineers |author1=Karl Johan Åström |author2=Richard M. Murray |chapter=§1.1: What is feedback? |chapter-url=https://books.google.com/books?id=cdG9fNqTDS8C&q=%22This+makes+reasoning+based+on+cause+and+effect+tricky%22&pg=PA1 |isbn= 9781400828739 |year=2008 |page=1 |publisher=Princeton University Press}} Online version found [http://authors.library.caltech.edu/25062/1/Feedback08.pdf here].</ref>}

==History==
历史

Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter [[Economics|economic theory]] in Britain by the 18th century, but it was not at that time recognized as a universal abstraction and so did not have a name.<ref name=mayr>{{Cite book |author= Otto Mayr|title=Authority, liberty, & automatic machinery in early modern Europe |year=1989 |isbn=978-0-8018-3939-9 | publisher=Johns Hopkins University Press |author-link=Otto Mayr }}</ref>

Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter economic theory in Britain by the 18th century, but it was not at that time recognized as a universal abstraction and so did not have a name.

自我调节机制自古以来就存在，直到18世纪，反馈的概念开始进入英国的经济理论，但当时它还不是一个普遍的抽象概念，因此没有名称。<ref name=mayr>{{Cite book |author= Otto Mayr|title=Authority, liberty, & automatic machinery in early modern Europe |year=1989 |isbn=978-0-8018-3939-9 | publisher=Johns Hopkins University Press |author-link=Otto Mayr }}</ref>

The first ever known artificial feedback device was a [[Ballcock|float valve]], for maintaining water at a constant level, invented in 270 BC in [[Alexandria]], [[Ancient Egypt|Egypt]].<ref name=":0">{{Cite book|title=Designing Kinetics for Architectural Facades|last=Moloney|first=Jules|publisher=Routledge|year=2011|isbn=978-0415610346}}</ref> This device illustrated the principle of feedback: a low water level opens the valve, the rising water then provides feedback into the system, closing the valve when the required level is reached. This then reoccurs in a circular fashion as the water level fluctuates.<ref name=":0" />

The first ever known artificial feedback device was a float valve, for maintaining water at a constant level, invented in 270 BC in Alexandria, Egypt. This device illustrated the principle of feedback: a low water level opens the valve, the rising water then provides feedback into the system, closing the valve when the required level is reached. This then reoccurs in a circular fashion as the water level fluctuates.

第一个已知的人工反馈装置是公元前270年在埃及亚历山大发明的用于保持水位恒定的浮阀。<ref name=":0">{{Cite book|title=Designing Kinetics for Architectural Facades|last=Moloney|first=Jules|publisher=Routledge|year=2011|isbn=978-0415610346}}</ref>这个装置说明了反馈的原理：低水位打开阀门，上升的水位向系统提供反馈，达到所需水位时关闭阀门。然后，这种情况会随着水位的波动循环地重复发生。<ref name=":0" />

[[Centrifugal governor]]s were used to regulate the distance and pressure between [[millstone]]s in [[windmill]]s since the 17th century. In 1788, [[James Watt]] designed his first centrifugal governor following a suggestion from his business partner [[Matthew Boulton]], for use in the [[steam engine]]s of their production. Early steam engines employed a purely [[reciprocating motion]], and were used for pumping water – an application that could tolerate variations in the working speed, but the use of steam engines for other applications called for more precise control of the speed.

Centrifugal governors were used to regulate the distance and pressure between millstones in windmills since the 17th century. In 1788, James Watt designed his first centrifugal governor following a suggestion from his business partner Matthew Boulton, for use in the steam engines of their production. Early steam engines employed a purely reciprocating motion, and were used for pumping water – an application that could tolerate variations in the working speed, but the use of steam engines for other applications called for more precise control of the speed.

自17世纪以来，[[离心调速器]]被用于调节[[风车]]中[[磨石]]之间的距离和压力。1788年，詹姆斯·瓦特 James Watt根据他的商业伙伴马修·布尔顿 Matthew Boulton的建议，设计了他的第一个离心调速器，用于他们生产的[[蒸汽机]]。早期的蒸汽机采用纯粹的[[往复运动]]，用于抽水——这种应用不受工作速度变化的影响，但蒸汽机在其他应用中的使用需要更精确的速度控制。

In [[1868]], [[James Clerk Maxwell]] wrote a famous paper, "On governors", that is widely considered a classic in feedback control theory.<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=free}}</ref> This was a landmark paper on [[control theory]] and the mathematics of feedback.

In 1868, James Clerk Maxwell wrote a famous paper, "On governors", that is widely considered a classic in feedback control theory.This was a landmark paper on [[control theory]] and the mathematics of feedback.

在1868年，詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell写了一篇著名的论文《论调速器》，这个论文被广泛认为是反馈控制理论的经典之作。<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=free}}</ref>这是一篇关于控制理论和反馈数学的里程碑式的论文。

The verb phrase ''to feed back'', in the sense of returning to an earlier position in a mechanical process, was in use in the US by the 1860s,<ref>''"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..."'' HH Cole, "Improvement in Fluting-Machines", [http://www.google.co.nz/patents/US55469 US Patent 55,469 (1866)] accessed 23 March 2012.</ref><ref>''"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..."'' JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", [http://www.google.co.nz/patents/US47769 US Patent 47,769 (1865)] accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error</ref> and in 1909, Nobel laureate [[Karl Ferdinand Braun]] used the term "feed-back" as a noun to refer to (undesired) [[Coupling (electronics)|coupling]] between components of an [[electronic circuit]].<ref>''"...as far as possible the circuit has no feed-back into the system being investigated."''
An example of a negative feedback loop with goals
[http://www.cdvandtext2.org/Braun-Nobel-lecture%201909.pdf]
A positive feedback loop example
Karl Ferdinand Braun, [https://www.nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.html "Electrical oscillations and wireless telegraphy"], Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.</ref>

The verb phrase to feed back, in the sense of returning to an earlier position in a mechanical process, was in use in the US by the 1860s, and in 1909, Nobel laureate Karl Ferdinand Braun used the term "feed-back" as a noun to refer to (undesired) coupling between components of an electronic circuit.

19世纪60年代，美国开始使用动词短语反馈，意思是在机械过程中回到原来的位置。<ref>''"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..."'' HH Cole, "Improvement in Fluting-Machines", [http://www.google.co.nz/patents/US55469 US Patent 55,469 (1866)] accessed 23 March 2012.</ref><ref>''"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..."'' JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", [http://www.google.co.nz/patents/US47769 US Patent 47,769 (1865)] accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error</ref> 1909年，诺贝尔奖获得者卡尔·费迪南德·布劳恩 Karl Ferdinand Braun用名词“反馈”来指电子电路元件之间的(不希望有的)耦合。<ref>''"...as far as possible the circuit has no feed-back into the system being investigated."''
An example of a negative feedback loop with goals
[http://www.cdvandtext2.org/Braun-Nobel-lecture%201909.pdf]
A positive feedback loop example
Karl Ferdinand Braun, [https://www.nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.html "Electrical oscillations and wireless telegraphy"], Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.</ref>

By the end of 1912, researchers using early electronic amplifiers ([[audion tube|audions]]) had discovered that deliberately coupling part of the output signal back to the input circuit would boost the amplification (through [[Regenerative circuit|regeneration]]), but would also cause the audion to howl or sing.<ref name="bennett">{{Cite book|url=http://worldcat.org/isbn/0-906-04807-9|title=A history of control engineering, 1800–1930|author=Stuart Bennett|publisher=Peregrinus for the Institution of Electrical Engineers|year=1979|isbn=978-0-906048-07-8|location=Stevenage; New York}} </ref> This action of feeding back of the signal from output to input gave rise to the use of the term "feedback" as a distinct word by 1920.<ref name=bennett/>

By the end of 1912, researchers using early electronic amplifiers (audions) had discovered that deliberately coupling part of the output signal back to the input circuit would boost the amplification (through regeneration), but would also cause the audion to howl or sing. This action of feeding back of the signal from output to input gave rise to the use of the term "feedback" as a distinct word by 1920.

到1912年底，研究人员利用早期电子放大器(三极管)发现，故意将部分输出信号耦合回输入电路，会提高放大率(形成再生回路)，但也会使三极管发生啸叫。<ref name="bennett">{{Cite book|url=http://worldcat.org/isbn/0-906-04807-9|title=A history of control engineering, 1800–1930|author=Stuart Bennett|publisher=Peregrinus for the Institution of Electrical Engineers|year=1979|isbn=978-0-906048-07-8|location=Stevenage; New York}} </ref>这种将信号从输出反馈到输入的行为使得 "反馈 "一词在1920年被作为一个独立的词汇使用。<ref name=bennett/>

Over the years there has been some dispute as to the best definition of feedback. According to [[William Ross Ashby|Ashby]] (1956), mathematicians and theorists interested in the principles of feedback mechanisms prefer the definition of "circularity of action", which keeps the theory simple and consistent. For those with more practical aims, feedback should be a deliberate effect via some more tangible connection.

Over the years there has been some dispute as to the best definition of feedback. According to Ashby (1956), mathematicians and theorists interested in the principles of feedback mechanisms prefer the definition of "circularity of action", which keeps the theory simple and consistent. For those with more practical aims, feedback should be a deliberate effect via some more tangible connection.

多年来，关于反馈的最佳定义一直存在一些争议。根据阿什比 Ashby(1956)的说法。对反馈机制原理感兴趣的数学家和理论家倾向于用 "作用的循环性 "来定义反馈，这使理论保持简洁和一致。对于那些有目的更实际的人来说，反馈应该是具体过程产生的一种有意的影响。

{{Quote|[Practical experimenters] object to the mathematician's definition, pointing out that this would force them to say that feedback was present in the ordinary pendulum ... between its position and its momentum—a "feedback" that, from the practical point of view, is somewhat mystical. To this the mathematician retorts that if feedback is to be considered present only when there is an actual wire or nerve to represent it, then the theory becomes chaotic and riddled with irrelevancies.<ref name=Ashby>。{{cite book |author=W. Ross Ashby |title=An introduction to cybernetics |publisher=Chapman & Hall |year=1957 |url=http://pcp.vub.ac.be/books/IntroCyb.pdf}}</ref>{{rp|page=54}}}}

{{引言|[实际实验者]反对数学家的定义，指出这将迫使他们说普通的摆.中存在反馈.....在其位置和动量之间——这种 "反馈"，从实际的角度看，有些神秘。对此，数学家反驳说，如果只有用实际的导线或神经来表示反馈时，才认为反馈是存在的，那么这个理论就会变得混乱，充满了无关紧要的东西<ref name=Ashby>。{{cite book |author=W. Ross Ashby |title=An introduction to cybernetics |publisher=Chapman & Hall |year=1957 |url=http://pcp.vub.ac.be/books/IntroCyb.pdf}}</ref>{{rp|page=54}}}}

Focusing on uses in management theory, Ramaprasad (1983) defines feedback generally as "...information about the gap between the actual level and the reference level of a system parameter" that is used to "alter the gap in some way". He emphasizes that the information by itself is not feedback unless translated into action.<ref name="Ramaprasad">{{Cite journal | doi=10.1002/bs.3830280103|title = On the definition of feedback| journal=Behavioral Science| volume=28| pages=4–13|year = 1983|last1 = Ramaprasad|first1 = Arkalgud}}</ref>

Focusing on uses in management theory, Ramaprasad (1983) defines feedback generally as "...information about the gap between the actual level and the reference level of a system parameter" that is used to "alter the gap in some way". He emphasizes that the information by itself is not feedback unless translated into action.

拉马普拉萨德 Ramaprasad (1983)侧重于反馈在管理理论中的用途，他通常将反馈定义为"……关于系统参数的实际水平与参考水平之间差距的信息"，用于 "以某种方式改变差距"。他强调，信息本身不是反馈，转化为行动才是。<ref name="Ramaprasad">{{Cite journal | doi=10.1002/bs.3830280103|title = On the definition of feedback| journal=Behavioral Science| volume=28| pages=4-13|year = 1983|last1 = Ramaprasad|first1 = Arkalgud}}</ref>。

==Types==
类型

===Positive and negative feedback===
正反馈和负反馈

{{Main|Negative feedback|Positive feedback}}
主要|消极反馈|积极反馈

[[File:Set-point control.png|thumb|350px|Maintaining a desired system performance despite disturbance using negative feedback to reduce system error]]

[[File:Set-point control.png|thumb|350px|利用负反馈减少系统误差，在受到干扰的情况下仍能保持理想的系统性能]]

[[File:Outcome Feedback Negative Feedback Loop.png|thumb|An example of a negative feedback loop with goals]]

[[[File:Outcome Feedback Negative Feedback Loop.png|thumb|拇指|目标负反馈循环的示例]]

[[File:Process Feedback Loop.png|thumb|A positive feedback loop example]]
[[File：Process Feedback Loop.png | thumb |正反馈循环示例]]

Positive feedback: If the signal fed back from output is in phase with the input signal, the feedback is called positive feedback.

 正反馈 Positive feedback: 如果输出的反馈信号与输入信号同相，则称为正反馈。

Negative feedback: If the signal fed back is of opposite polarity or out of phase by 180° with respect to input signal, the feedback is called as negative feedback.

 负反馈 Negative feedback: 如果反馈信号与输入信号的极性相反或相位相差180°，则称为负反馈。

As an example of negative feedback, the diagram might represent a cruise control system in a car, for example, that matches a target speed such as the speed limit. The controlled system is the car; its input includes the combined torque from the engine and from the changing slope of the road (the disturbance). The car's speed (status) is measured by a speedometer. The error signal is the departure of the speed as measured by the speedometer from the target speed (set point). This measured error is interpreted by the controller to adjust the accelerator, commanding the fuel flow to the engine (the effector). The resulting change in engine torque, the feedback, combines with the torque exerted by the changing road grade to reduce the error in speed, minimizing the road disturbance.

该图表示的汽车中的巡航控制系统可以作为负反馈的一个例子，它使车速与目标速度(如车速限制)匹配。受控系统是汽车，其输入包括来自发动机和来自路面变化的坡度(干扰)的组合扭矩。汽车的速度(状态)由速度表测量。误差信号是速度计测量的速度与目标速度（设定点）的偏差。这个测量的误差由控制器来解译并以此来调整加速器，控制燃料流到发动机(效应器)。由此产生的发动机扭矩的变化，即反馈，与路面变化的坡度所施加的扭矩相结合，以减少速度误差，减少道路干扰。

The terms "positive" and "negative" were first applied to feedback prior to WWII. The idea of positive feedback was already current in the 1920s with the introduction of the [[regenerative circuit]].<ref name=mindell>{{Cite book|author=David A. Mindell|title=Between Human and Machine : Feedback, Control, and Computing before Cybernetics.|year= 2002|publisher=Johns Hopkins University Press|location=Baltimore, MD, US|url=https://books.google.com/books?id=sExvSbe9MSsC|isbn=9780801868955}}</ref>Friis and Jensen (1924) described regeneration in a set of electronic amplifiers as a case where ''the "feed-back" action is positive'' in contrast to negative feed-back action, which they mention only in passing.<ref name=friis>Friis, H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181–205.</ref> [[Harold Stephen Black]]'s classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:

The terms "positive" and "negative" were first applied to feedback prior to WWII. The idea of positive feedback was already current in the 1920s with the introduction of the regenerative circuit. Friis and Jensen (1924) described regeneration in a set of electronic amplifiers as a case where the "feed-back" action is positive in contrast to negative feed-back action, which they mention only in passing. Harold Stephen Black's classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:

“正面”和“负面”这两个词在第二次世界大战之前首次用于反馈。20世纪20年代，随着再生电路的引入，正反馈的概念已经流行起来。<ref name=mindell>{{Cite book|author=David A. Mindell|title=Between Human and Machine : Feedback, Control, and Computing before Cybernetics.|year= 2002|publisher=Johns Hopkins University Press|location=Baltimore, MD, US|url=https://books.google.com/books?id=sExvSbe9MSsC|isbn=9780801868955}}</ref> 弗里斯 Friis和延森 Jensen(1924)将一套电子放大器中的再生回路描述为"反馈"作用是正的例子，以此和他们顺便提及的负反馈作用相区别。<ref name=friis>Friis, H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181–205.</ref>哈罗德·史蒂芬·布莱克 Harold Stephen Black1934年的经典论文首次详细阐述了负反馈在电子放大器中的应用。布莱克认为:

{{Quote|Positive feed-back increases the gain of the amplifier, negative feed-back reduces it.<ref name=black>H.S. Black, "Stabilized feed-back amplifiers", ''Electrical Engineering'', vol. 53, pp. 114–120, January 1934.</ref>}}

{{Quote|正反馈增加放大器的增益，负反馈降低增益。<ref name=black>H.S. Black, "Stabilized feed-back amplifiers", ''Electrical Engineering'', vol. 53, pp. 114–120, January 1934.</ref>}}

According to Mindell (2002) confusion in the terms arose shortly after this:

据Mindell(2002年)说，在这之后不久就出现了术语上的混乱。

{{Quote|...Friis and Jensen had made the same distinction Black used between "positive feed-back" and "negative feed-back", based not on the sign of the feedback itself but rather on its effect on the amplifier's gain. In contrast, Nyquist and Bode, when they built on Black's work, referred to negative feedback as that with the sign reversed. Black had trouble convincing others of the utility of his invention in part because confusion existed over basic matters of definition.<ref name=mindell/>{{rp|page=121}}}}

{{Quote|...Friis和Jensen对Black在 "正反馈 "和 "负反馈 "之间的区分是一样的，不是基于反馈本身的符号，而是基于它对放大器增益的影响。相反，Nyquist和Bode在Black的工作基础上，将负反馈称为符号相反的反馈。布莱克难以说服其他人相信他的发明的实用性，因为再基本的概念上存在混乱。<ref name=mindell/>{{rp|page=121}}}}

Even prior to the terms being applied, [[James Clerk Maxwell]] had described several kinds of "component motions" associated with the [[centrifugal governor]]s used in steam engines, distinguishing between those that lead to a continual ''increase'' in a disturbance or the amplitude of an oscillation, and those that lead to a ''decrease'' of the same.<ref name=maxwell>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|url=http://en.wikipedia.org/wiki/File:On_Governors.pdf|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283|doi=10.1098/rspl.1867.0055|s2cid=51751195}}</ref>

Even prior to the terms being applied, James Clerk Maxwell had described several kinds of "component motions" associated with the centrifugal governors used in steam engines, distinguishing between those that lead to a continual ''increase'' in a disturbance or the amplitude of an oscillation, and those that lead to a ''decrease'' of the same.

甚至在这些术语被应用之前，詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell就已经描述了几种与蒸汽机中使用的离心式调速器相关的 "运动分量"，并区分了那些导致扰动或振荡幅度持续''增加''的运动和那些导致其''减少''的运动。 <ref name=maxwell>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|url=http://en.wikipedia.org/wiki/File:On_Governors.pdf|journal=Proceedings of the Royal Society of London|volume=16|year=1868|pages=270-283|doi=10.1098/rspl.1867}。 .0055|s2cid=51751195}}</ref>

====Terminology====
术语

The terms positive and negative feedback are defined in different ways within different disciplines.

正反馈和负反馈在不同的学科中有不同的定义。

# the altering of the ''gap'' between reference and actual values of a parameter, based on whether the gap is ''widening'' (positive) or ''narrowing'' (negative).<ref name="Ramaprasad" />

#the altering of the gap between reference and actual values of a parameter, based on whether the gap is widening (positive) or narrowing (negative).

# 根据差距是扩大（正）还是缩小（负）改变一个参数的参考值和实际值之间的差距；<ref name="Ramaprasad" />

# the [[Valence (psychology)|valence]] of the ''action'' or ''effect'' that alters the gap, based on whether it has a ''happy'' (positive) or ''unhappy'' (negative) emotional connotation to the recipient or observer.<ref name=herold1977>Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.</ref>

# the valence of the ''action'' or ''effect'' that alters the gap, based on whether it has a ''happy'' (positive) or ''unhappy'' (negative) emotional connotation to the recipient or observer.

#改变差距的''行动''或''效果''的[[ 效价 valence，基于它对接受者或观察者是否具有''快乐''（积极）或''不快乐''（消极）的情感内涵。<ref name=herold1977>Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.</ref>

The two definitions may cause confusion, such as when an incentive (reward) is used to boost poor performance (narrow a gap). Referring to definition 1, some authors use alternative terms, replacing ''positive/negative'' with ''self-reinforcing/self-correcting'',<ref name="senge">{{Cite book|author=Peter M. Senge|title=The Fifth Discipline: The Art and Practice of the Learning Organization|year=1990|publisher=Doubleday|location=New York |isbn=978-0-385-26094-7|page=424|url=https://archive.org/details/fifthdisciplineasen00seng}}
</ref> ''reinforcing/balancing'',<ref name="sterman">John D. Sterman, ''Business Dynamics: Systems Thinking and Modeling for a Complex World'', McGraw Hill/Irwin, 2000. {{ISBN|978-0-07-238915-9}}</ref> ''discrepancy-enhancing/discrepancy-reducing''<ref name="carver">Charles S. Carver, Michael F. Scheier: ''On the Self-Regulation of Behavior'' Cambridge University Press, 2001 </ref> or ''regenerative/degenerative''<ref>Hermann A Haus and Richard B. Adler, ''Circuit Theory of Linear Noisy Networks'', MIT Press, 1959</ref>respectively. And for definition 2, some authors advocate describing the action or effect as positive/negative ''[[Reinforcement#Reinforcement|reinforcement]]'' or ''[[Reinforcement#Punishment|punishment]]'' rather than feedback.<ref name="Ramaprasad" /><ref name="skinner">BF Skinner, ''The Experimental Analysis of Behavior'', American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371</ref>Yet even within a single discipline an example of feedback can be called either positive or negative, depending on how values are measured or referenced.<ref>"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
For feedback in the educational context, see corrective feedback.
Ralph L. Levine, Hiram E. Fitzgerald. ''Analysis of the dynamic psychological systems: methods and applications'', {{ISBN|978-0306437465}} (1992) page 123</ref>

The two definitions may cause confusion, such as when an incentive (reward) is used to boost poor performance (narrow a gap). Referring to definition 1, some authors use alternative terms, replacing positive/negative with self-reinforcing/self-correcting, reinforcing/balancing, discrepancy-enhancing/discrepancy-reducing or regenerative/degenerative respectively. And for definition 2, some authors advocate describing the action or effect as positive/negative reinforcement or punishment rather than feedback. Yet even within a single discipline an example of feedback can be called either positive or negative, depending on how values are measured or referenced.

这两种定义可能会引起混淆，比如当激励(奖励)被用来提高糟糕的表现(缩小差距)。针对定义1，一些作者使用了替代术语，分别用自强化/自纠正<ref name="senge">{{Cite book|author=Peter M. Senge|title=The Fifth Discipline: The Art and Practice of the Learning Organization|year=1990|publisher=Doubleday|location=New York |isbn=978-0-385-26094-7|page=424|url=https://archive.org/details/fifthdisciplineasen00seng}}
</ref>、强化/平衡<ref name="sterman">John D. Sterman, ''Business Dynamics: Systems Thinking and Modeling for a Complex World'', McGraw Hill/Irwin, 2000. {{ISBN|978-0-07-238915-9}}</ref>、离散增强/离散减少<ref name="carver">Charles S. Carver, Michael F. Scheier: ''On the Self-Regulation of Behavior'' Cambridge University Press, 2001 </ref>或再生/退化<ref>Hermann A Haus and Richard B. Adler, ''Circuit Theory of Linear Noisy Networks'', MIT Press, 1959</ref>来替代正/负。对于定义2，一些作者主张将行为或效果描述为积极/消极的强化或惩罚，而不是反馈。<ref name="Ramaprasad" /><ref name="skinner">BF Skinner, ''The Experimental Analysis of Behavior'', American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371</ref>然而，即使是在一个单一的学科中，反馈的例子也可以被称为正的或负的，这取决于如何衡量或引用其含义。<ref>"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
For feedback in the educational context, see corrective feedback.
Ralph L. Levine, Hiram E. Fitzgerald. ''Analysis of the dynamic psychological systems: methods and applications'', {{ISBN|978-0306437465}} (1992) page 123</ref>

This confusion may arise because feedback can be used for either ''informational'' or ''motivational'' purposes, and often has both a ''[[Qualitative property|qualitative]]'' and a ''[[Quantitative property|quantitative]]'' component. As Connellan and Zemke (1993) put it:

This confusion may arise because feedback can be used for either informational or motivational purposes, and often has both a qualitative and a quantitative component. As Connellan and Zemke (1993) put it:

这种混淆可能会出现，因为反馈既可以用于信息的目的，也可以用于激励的目的，而且往往同时具有定性和定量的成分。正如康奈兰 Connellan和泽姆克 Zemke(1993)所言:

{{Quote|''Quantitative'' feedback tells us how much and how many. ''Qualitative'' feedback tells us how good, bad or indifferent.<ref name=Connellan>Thomas K. Connellan and Ron Zemke, "Sustaining Knock Your Socks Off Service" AMACOM, 1 July 1993. {{ISBN|0-8144-7824-7}}</ref>{{rp|page=102}}}}

{{Quote|''定量''反馈告诉我们多少。''定性''反馈告诉我们多好、多坏或二者之间。<ref name=Connellan>Thomas K. Connellan and Ron Zemke, "Sustaining Knock Your Socks Off Service" AMACOM, 1 July 1993. {{ISBN|0-8144-7824-7}}</ref>{{rp|page=102}}}}

====Limitations of negative and positive feedback====
正反馈和负反馈的限制

While simple systems can sometimes be described as one or the other type, many systems with feedback loops cannot be so easily designated as simply positive or negative, and this is especially true when multiple loops are present.

虽然单一系统有时可以被描述为一种或另一种类型，但许多具有反馈回路的系统不能简单地指定为正或负，尤其是存在多个回路时。

{{Quote|When there are only two parts joined so that each affects the other, the properties of the feedback give important and useful information about the properties of the whole. But when the parts rise to even as few as four, if every one affects the other three, then twenty circuits can be traced through them; and knowing the properties of all the twenty circuits does not give complete information about the system.<ref name=Ashby/>{{rp|page=54}}}}

{{Quote|当只有两个部分连接在一起，以至于每个部分都会影响到另一个部分时，反馈的属性就能提供关于整体属性的重要有用信息。但是，当部分增加到即使只有四个时，如果每一个都影响其他三个，那么就可以通过它们找到二十个回路；而知道所有这二十个回路的特性并不能提供有关系统的完整信息。<ref name=Ashby/>{{rp|page=54}}}}

===Other types of feedback===
其他反馈类型

In general, feedback systems can have many signals fed back and the feedback loop frequently contain mixtures of positive and negative feedback where positive and negative feedback can dominate at different frequencies or different points in the state space of a system.

一般来说，反馈系统可以有许多信号反馈，反馈回路中经常包含混合在一起的正反馈和负反馈，其中正反馈和负反馈可以在系统状态空间的不同频率或不同点占主导地位。

The term bipolar feedback has been coined to refer to biological systems where positive and negative feedback systems can interact, the output of one affecting the input of another, and vice versa.<ref name = Smit>{{cite book |title=Introduction to Bioregulatory Medicine |author1=Alta Smit |author2=Arturo O'Byrne |chapter-url=https://books.google.com/books?id=RzXAOUnCM3oC&pg=PA6 |page=6 |chapter=Bipolar feedback |isbn=9783131469717 |year=2011 |publisher=Thieme}}</ref>

术语 双极反馈 bipolar feedback 是指生物系统中正反馈系统和负反馈系统可以相互作用，一个系统的输出会影响另一个系统的输入，反之亦然。<ref name = Smit>{{cite book |title=Introduction to Bioregulatory Medicine |author1=Alta Smit |author2=Arturo O'Byrne |chapter-url=https://books.google.com/books?id=RzXAOUnCM3oC&pg=PA6 |page=6 |chapter=Bipolar feedback |isbn=9783131469717 |year=2011 |publisher=Thieme}}</ref>

Some systems with feedback can have very complex behaviors such as [[Chaos theory|chaotic behaviors]] in non-linear systems, while others have much more predictable behaviors, such as those that are used to make and design digital systems.

Some systems with feedback can have very complex behaviors such as chaotic behaviors in non-linear systems, while others have much more predictable behaviors, such as those that are used to make and design digital systems.

一些带有反馈的系统会有非常复杂的行为，比如非线性系统中的混沌行为，而另一些系统则有更多可预测的行为，比如那些用于制造和设计数字系统的系统。

Feedback is used extensively in digital systems. For example, binary counters and similar devices employ feedback where the current state and inputs are used to calculate a new state which is then fed back and clocked back into the device to update it.

反馈在数字系统中得到了广泛的应用。例如，二进制计数器和类似的设备采用了反馈，即利用当前的状态和输入来计算一个新的状态，然后反馈到设备并计时更新它。

Feedback can give rise to incredibly complex behaviors. The [[Mandelbrot set (black) within a continuously colored environment is plotted by repeatedly feeding back values through a simple equation and recording the points on the imaginary plane that fail to diverge|alt=

。

==Applications==
应用

===Mathematics and dynamical systems===
数学和动力系统

[[File:Mandel zoom 00 mandelbrot set.jpg|322px|thumb|Feedback can give rise to incredibly complex behaviors. The [[Mandelbrot set]] (black) within a continuously colored environment is plotted by repeatedly feeding back values through a simple equation and recording the points on the imaginary plane that fail to diverge|alt=]]

[[File:Mandel zoom 00 mandelbrot set.jpg|322px|thumb|反馈可以产生令人难以置信的复杂行为。通过一个简单的方程反复反馈数值，并记录虚平面上未能偏离的点，绘制出连续着色环境中的 曼德尔布罗特集（布莱克） Mandelbrot set]] (black)。]]

{{Main|Dynamical system|Chaos theory|Edge of chaos|Control theory}}

{{主要|动力系统|混沌理论|混沌边缘|控制理论}}

By using feedback properties, the behavior of a system can be altered to meet the needs of an application; systems can be made stable, responsive or held constant. It is shown that dynamical systems with a feedback experience an adaptation to the [[edge of chaos]].<ref>{{cite journal|last1=Wotherspoon|first1=T.|last2=Hubler|first2=A.|title=Adaptation to the edge of chaos with random-wavelet feedback|journal=J. Phys. Chem. A|date=2009|doi=10.1021/jp804420g|pmid=19072712|volume=113|issue=1|pages=19–22|bibcode=2009JPCA..113...19W}}</ref>

By using feedback properties, the behavior of a system can be altered to meet the needs of an application; systems can be made stable, responsive or held constant. It is shown that dynamical systems with a feedback experience an adaptation to the edge of chaos.

通过使用反馈属性，可以更改系统的行为以满足应用程序的需求；可以使系统稳定、响应迅速或保持恒定。结果表明，具有反馈的动力系统会适应混沌边缘现象。<ref>{{cite journal|last1=Wotherspoon|first1=T.|last2=Hubler|first2=A.|title=Adaptation to the edge of chaos with random-wavelet feedback|journal=J. Phys. Chem. A|date=2009|doi=10.1021/jp804420g|pmid=19072712|volume=113|issue=1|pages=19–22|bibcode=2009JPCA..113...19W}}</ref>

===Biology===
生物

{{See also|Homeostasis|Allostasis}}
{{另请参见|内环境稳态|稳态}}

In [[biology|biological]] systems such as [[organism]]s, [[ecosystem]]s, or the [[biosphere]], most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal value of the controlled parameter can result from the changes in internal and external environments. A change of some of the environmental conditions may also require change of that range to change for the system to function. The value of the parameter to maintain is recorded by a reception system and conveyed to a regulation module via an information channel. An example of this is [[insulin oscillation]]s.

In biological systems such as organisms, ecosystems, or the biosphere, most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal value of the controlled parameter can result from the changes in internal and external environments. A change of some of the environmental conditions may also require change of that range to change for the system to function. The value of the parameter to maintain is recorded by a reception system and conveyed to a regulation module via an information channel. An example of this is insulin oscillations.

在生物体、生态系统或生物圈等生物系统中，大多数参数必须在特定环境下保持在围绕最佳水平的狭窄范围内。受控参数和最佳值之间的偏差可能是由于内外部环境的变化造成的。环境条件的变化，也能需要改变参数变化的范围来维持系统的运行。受控参数的值由接收系统记录下来，并通过信息通道传达给调节模块。胰岛素振荡就是一个例子。

Biological systems contain many types of regulatory circuits, both positive and negative. As in other contexts, positive and negative do not imply that the feedback causes good or bad effects. A negative feedback loop is one that tends to slow down a process, whereas the positive feedback loop tends to accelerate it. The mirror neurons are part of a social feedback system, when an observed action is "mirrored" by the brain—like a self-performed action.

生物系统包含许多类型的调节回路，包括正向和负向。与其他情况一样，正负并不意味着反馈会造成好的或坏的影响。负反馈回路是一种倾向于减缓过程的回路，而正反馈回路则倾向于加速过程。镜像神经元是社会反馈系统的一部分，当观察到的行为被大脑“镜像”——就像一个自导自演的行为。

Normal tissue integrity is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted molecules that act as mediators; failure of key feedback mechanisms in cancer disrupts tissue function.<ref>{{cite journal|last1=Vlahopoulos|first1=SA|last2=Cen|first2=O|last3=Hengen|first3=N|last4=Agan|first4=J|last5=Moschovi|first5=M|last6=Critselis|first6=E|last7=Adamaki|first7=M|last8=Bacopoulou|first8=F|last9=Copland|first9=JA|last10=Boldogh|first10=I|last11=Karin|first11=M|last12=Chrousos|first12=GP|title=Dynamic aberrant NF-κB spurs tumorigenesis: A new model encompassing the microenvironment.|journal=Cytokine & Growth Factor Reviews|date=20 June 2015|pmid=26119834|doi=10.1016/j.cytogfr.2015.06.001|volume=26|issue=4|pages=389–403|pmc=4526340}}</ref> In an injured or infected tissue, inflammatory mediators elicit feedback responses in cells, which alter gene expression, and change the groups of molecules expressed and secreted, including molecules that induce diverse cells to cooperate and restore tissue structure and function. This type of feedback is important because it enables coordination of immune responses and recovery from infections and injuries. During cancer, key elements of this feedback fail. This disrupts tissue function and immunity.<ref>{{cite journal | last1 = Vlahopoulos | first1 = SA | title = Aberrant control of NF-κB in cancer permits transcriptional and phenotypic plasticity, to curtail dependence on host tissue: molecular mode. | journal = Cancer Biology & Medicine | date = August 2017 | pmid = 28884042 | doi = 10.20892/j.issn.2095-3941.2017.0029 | volume = 14 | issue = 3 | pages = 254–270 | pmc = 5570602}}</ref><ref>{{cite journal|last1=Korneev|first1=KV|last2=Atretkhany|first2=KN|last3=Drutskaya|first3=MS|last4=Grivennikov|first4=SI|last5=Kuprash|first5=DV|last6=Nedospasov|first6=SA|title=TLR-signaling and proinflammatory cytokines as drivers of tumorigenesis.|journal=Cytokine|date=January 2017|volume=89|pages=127–135|doi=10.1016/j.cyto.2016.01.021|pmid=26854213}}</ref>

Normal tissue integrity is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted molecules that act as mediators; failure of key feedback mechanisms in cancer disrupts tissue function.In an injured or infected tissue, inflammatory mediators elicit feedback responses in cells, which alter gene expression, and change the groups of molecules expressed and secreted, including molecules that induce diverse cells to cooperate and restore tissue structure and function. This type of feedback is important because it enables coordination of immune responses and recovery from infections and injuries. During cancer, key elements of this feedback fail. This disrupts tissue function and immunity.

正常组织的完整性是通过粘附分子和作为介质的分泌分子介导的不同细胞类型之间的反馈相互作用来保持的；癌症中关键反馈机制的失效会破坏组织功能。.<ref>{{cite journal|last1=Vlahopoulos|first1=SA|last2=Cen|first2=O|last3=Hengen|first3=N|last4=Agan|first4=J|last5=Moschovi|first5=M|last6=Critselis|first6=E|last7=Adamaki|first7=M|last8=Bacopoulou|first8=F|last9=Copland|first9=JA|last10=Boldogh|first10=I|last11=Karin|first11=M|last12=Chrousos|first12=GP|title=Dynamic aberrant NF-κB spurs tumorigenesis: A new model encompassing the microenvironment.|journal=Cytokine & Growth Factor Reviews|date=20 June 2015|pmid=26119834|doi=10.1016/j.cytogfr.2015.06.001|volume=26|issue=4|pages=389–403|pmc=4526340}}</ref>在受伤或感染的组织中，炎症介质会引起细胞的反馈反应，改变基因表达，改变细胞表达和分泌的分子群，包括诱导不同细胞合作的分子和恢复组织结构和功能的分子。这种类型的反馈很重要，因为它能够协调免疫反应、使机体从感染和损伤中恢复。在癌症过程中，这种反馈的关键要素会失效，进而破坏组织功能和免疫力。<ref>{{cite journal | last1 = Vlahopoulos | first1 = SA | title = Aberrant control of NF-κB in cancer permits transcriptional and phenotypic plasticity, to curtail dependence on host tissue: molecular mode. | journal = Cancer Biology & Medicine | date = August 2017 | pmid = 28884042 | doi = 10.20892/j.issn.2095-3941.2017.0029 | volume = 14 | issue = 3 | pages = 254–270 | pmc = 5570602}}</ref><ref>{{cite journal|last1=Korneev|first1=KV|last2=Atretkhany|first2=KN|last3=Drutskaya|first3=MS|last4=Grivennikov|first4=SI|last5=Kuprash|first5=DV|last6=Nedospasov|first6=SA|title=TLR-signaling and proinflammatory cytokines as drivers of tumorigenesis.|journal=Cytokine|date=January 2017|volume=89|pages=127–135|doi=10.1016/j.cyto.2016.01.021|pmid=26854213}}</ref>

Mechanisms of feedback were first elucidated in bacteria, where a nutrient elicits changes in some of their metabolic functions.<ref>{{cite journal|last1= Sanwal|first1=BD| title= Allosteric controls of amphilbolic pathways in bacteria.|journal= Bacteriol. Rev.|date=March 1970|volume=34|issue=1|pages=20–39 |pmid=4315011 |pmc=378347|doi=10.1128/MMBR.34.1.20-39.1970}}</ref>Feedback is also central to the operations of [[gene]]s and [[gene regulatory network]]s. [[Repressor protein|Repressor]] (see [[Lac repressor]]) and [[activator protein|activator]] [[protein]]s are used to create genetic [[operon]]s, which were identified by [[Francois Jacob]] and [[Jacques Monod]] in 1961 as ''feedback loops''.<ref>{{cite journal|last1= Jacob|first1=F|last2=Monod|first2=J|title= Genetic regulatory mechanisms in the synthesis of proteins.|journal= J Mol Biol|date=June 1961|volume=3|issue=3|pages=318–356 |pmid=13718526|doi=10.1016/S0022-2836(61)80072-7}}</ref> These feedback loops may be positive (as in the case of the coupling between a sugar molecule and the proteins that import sugar into a bacterial cell), or negative (as is often the case in [[metabolic]] consumption).

Mechanisms of feedback were first elucidated in bacteria, where a nutrient elicits changes in some of their metabolic functions.Feedback is also central to the operations of genes and gene regulatory networks. Repressor (see Lac repressor) and activator proteins are used to create genetic operons, which were identified by Francois Jacob and Jacques Monod in 1961 as feedback loops. These feedback loops may be positive (as in the case of the coupling between a sugar molecule and the proteins that import sugar into a bacterial cell), or negative (as is often the case in metabolic consumption).

反馈机制首次在细菌中得到阐明，是一种营养物质会引起其部分代谢功能的变化。<ref>{{cite journal|last1= Sanwal|first1=BD| title= Allosteric controls of amphilbolic pathways in bacteria.|journal= Bacteriol. Rev.|date=March 1970|volume=34|issue=1|pages=20–39 |pmid=4315011 |pmc=378347|doi=10.1128/MMBR.34.1.20-39.1970}}</ref>反馈也是基因和基因调控网络运作的中心。用 阻遏蛋白 Repressor(参见 Lac 阻遏蛋白)和 激活蛋白 activator protein来创造 基因操纵子 genetic operons protein，这被弗朗索瓦·雅各布 Francois Jacob 和雅克·莫诺德 Jacques Monod 在1961年确定为反馈回路。<ref>{{cite journal|last1= Jacob|first1=F|last2=Monod|first2=J|title= Genetic regulatory mechanisms in the synthesis of proteins.|journal= J Mol Biol|date=June 1961|volume=3|issue=3|pages=318–356 |pmid=13718526|doi=10.1016/S0022-2836(61)80072-7}}</ref>这些反馈回路可能是正的(例如糖分子和将糖输入细菌细胞的蛋白质之间的结合) ，也可能是负的(例如代谢消耗中经常出现的情况)。

On a larger scale, feedback can have a stabilizing effect on animal populations even when profoundly affected by external changes, although time lags in feedback response can give rise to [[Lotka–Volterra equation|predator-prey cycles]].<ref>CS Holling. "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics 4:1-23. 1973</ref>

On a larger scale, feedback can have a stabilizing effect on animal populations even when profoundly affected by external changes, although time lags in feedback response can give rise to predator-prey cycles.

尽管反馈反应的时间滞后可能引起捕食者-猎物循环，在受到外部变化的深刻影响的情况下，反馈也能对动物种群产生稳定作用。<ref>CS Holling. "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics 4:1-23. 1973</ref>

In [[fermentation (biochemistry)|zymology]], feedback serves as regulation of activity of an enzyme by its direct {{Not a typo|product(s)}} or downstream {{Not a typo|metabolite(s)}} in the metabolic pathway (see [[Allosteric regulation]]).

In zymology, feedback serves as regulation of activity of an enzyme by its direct product(s) or downstream metabolite(s) in the metabolic pathway (see Allosteric regulation).

在酶学中，反馈在代谢途径中通过直接产物或的下游代谢产物来调节酶的活性(见''' 变构调节allosteric regulation ''')。

The [[hypothalamic–pituitary–adrenal axis]] is largely controlled by positive and negative feedback, much of which is still unknown.

The hypothalamic–pituitary–adrenal axis is largely controlled by positive and negative feedback, much of which is still unknown.

下丘脑-垂体-肾上腺在很大程度上受到正反馈和负反馈的控制，其中的机制很大程度上仍然未知。

In [[psychology]], the body receives a stimulus from the environment or internally that causes the release of [[hormone]]s. Release of hormones then may cause more of those hormones to be released, causing a positive feedback loop. This cycle is also found in certain behaviour. For example, "shame loops" occur in people who blush easily. When they realize that they are blushing, they become even more embarrassed, which leads to further blushing, and so on.<ref>{{cite magazine|last=Scheff |first=Thomas |url=http://www.psychologytoday.com/blog/lets-connect/200909/the-emotionalrelational-world |title=The Emotional/Relational World |magazine=Psychology Today |date=2009-09-02 |accessdate=2013-07-10}}</ref>

In psychology, the body receives a stimulus from the environment or internally that causes the release of hormones. Release of hormones then may cause more of those hormones to be released, causing a positive feedback loop. This cycle is also found in certain behaviour. For example, "shame loops" occur in people who blush easily. When they realize that they are blushing, they become even more embarrassed, which leads to further blushing, and so on.

在心理学中，身体接受来自环境或内部的刺激，从而导致激素的释放。然后，激素的释放可能会导致更多的激素被释放，从而形成正反馈循环。这种循环也存在于某些行为中。例如，容易脸红的人就会出现 "羞耻循环"。当他们意识到自己脸红的时候，他们会变得更加尴尬，从而导致进一步的脸红，等等。<ref>{{cite magazine|last=Scheff |first=Thomas |url=http://www.psychologytoday.com/blog/lets-connect/200909/the-emotionalrelational-world |title=The Emotional/Relational World |magazine=Psychology Today |date=2009-09-02 |accessdate=2013-07-10}}</ref>

===Climate science===
气候科学

{{Main|Climate change feedback}}
{{主要|气候变化反馈}}

The climate system is characterized by strong positive and negative feedback loops between processes that affect the state of the atmosphere, ocean, and land. A simple example is the [[Ice-albedo feedback|ice-albedo positive feedback]] loop whereby melting snow exposes more dark ground (of lower [[albedo]]), which in turn absorbs heat and causes more snow to melt.

The climate system is characterized by strong positive and negative feedback loops between processes that affect the state of the atmosphere, ocean, and land. A simple example is the ice-albedo positive feedback loop whereby melting snow exposes more dark ground (of lower albedo), which in turn absorbs heat and causes more snow to melt.

气候系统的特点是，影响大气、海洋和陆地状态的过程之间存在着强烈的正负反馈回路。一个简单的例子是冰-反射率正反馈环路，即雪的融化使更多的黑暗地面(反射率较低)暴露出来，反过来吸收热量，使更多的雪融化。

===Control theory===
控制理论

{{Main|Control theory}}
{{主要|控制理论}}

Feedback is extensively used in control theory, using a variety of methods including [[state space (controls)]], [[full state feedback]], and so forth. Note that in the context of control theory, "feedback" is traditionally assumed to specify "negative feedback".<ref name=mees>''"There is a tradition in control theory that one deals with a ''negative feedback loop'' in which a negative sign is included in the feedback loop..."'' A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981. {{ISBN|0-471-27822-X}}. p69</ref>

Feedback is extensively used in control theory, using a variety of methods including state space (controls), full state feedback, and so forth. Note that in the context of control theory, "feedback" is traditionally assumed to specify "negative feedback".

反馈广泛应用于控制理论中，使用的方法很多，包括状态矢量空间（控制）、全状态反馈等。需要注意的是，在控制理论的背景下，“反馈”通常特指“负反馈”。<ref name=mees>''"There is a tradition in control theory that one deals with a ''negative feedback loop'' in which a negative sign is included in the feedback loop..."'' A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981. {{ISBN|0-471-27822-X}}. p69</ref>

{{Further|PID controller}}

{{进一步|PID控制器}}。、

The most common general-purpose [[controller (control theory)|controller]] using a control-loop feedback mechanism is a [[PID controller|proportional-integral-derivative]] (PID) controller. Heuristically, the terms of a PID controller can be interpreted as corresponding to time: the proportional term depends on the ''present'' error, the integral term on the accumulation of ''past'' errors, and the derivative term is a prediction of ''future'' error, based on current rate of change.<ref>{{Citation | url = http://www.eolss.net/ebooks/Sample%20Chapters/C18/E6-43-03-03.pdf | title = PID Control | last = Araki | first = M. }}</ref>

The most common general-purpose controller using a control-loop feedback mechanism is a proportional-integral-derivative (PID) controller. Heuristically, the terms of a PID controller can be interpreted as corresponding to time: the proportional term depends on the present error, the integral term on the accumulation of past errors, and the derivative term is a prediction of future error, based on current rate of change.

最常见的采用控制回路反馈机制的通用控制器是比例-积分-导数（PID）控制器。从启发式的角度看，PID控制器的项可以解释为与时间相对应：比例项取决于现在的误差，积分项取决于过去误差的积累，而导数项则是根据当前的变化率，对未来误差进行预测。<ref>{{Citation | url = http://www.eolss.net/ebooks/Sample%20Chapters/C18/E6-43-03-03.pdf | title = PID Control | last = Araki | first = M. }}</ref>

===Education===
教育

For feedback in the educational context, see [[corrective feedback]].
For feedback in the educational context, see corrective feedback.

关于教育方面的反馈，见纠正性反馈。

The loud squeals that sometimes occurs in audio systems, PA systems, and rock music are known as audio feedback. If a microphone is in front of a loudspeaker that it is connected to, sound that the microphone picks up comes out of the speaker, and is picked up by the microphone and re-amplified. If the loop gain is sufficient, howling or squealing at the maximum power of the amplifier is possible.

音响系统、扩音系统和摇滚音乐中有时会出现的响亮的尖叫声，这就是所谓的音频反馈。如果话筒在它所连接的扬声器前，话筒接收的声音就会从扬声器中传出，并被话筒结束并再次放大。如果环路增益足够，在放大器的最大功率下就可以发出啸叫或尖叫声。

===Mechanical engineering===
机械工程

In ancient times, the [[float valve]] was used to regulate the flow of water in Greek and Roman [[water clock]]s; similar float valves are used to regulate fuel in a [[carburettor]] and also used to regulate tank water level in the [[flush toilet]].

In ancient times, the float valve was used to regulate the flow of water in Greek and Roman water clocks; similar float valves are used to regulate fuel in a carburettor and also used to regulate tank water level in the flush toilet.

在古代，浮阀被用来调节希腊和罗马水钟的水流; 类似的浮阀被用来调节化油器的燃料，也被用来调节抽水马桶的水位。

The Dutch inventor [[Cornelius Drebbel]] (1572-1633) built thermostats (c1620) to control the temperature of chicken incubators and chemical furnaces. In 1745, the windmill was improved by blacksmith Edmund Lee, who added a [[windmill fantail|fantail]] to keep the face of the windmill pointing into the wind. In 1787, [[Tom Mead]] regulated the rotation speed of a windmill by using a [[conical pendulum|centrifugal pendulum]] to adjust the distance between the bedstone and the runner stone (i.e., to adjust the load).

The Dutch inventor Cornelius Drebbel (1572-1633) built thermostats (c1620) to control the temperature of chicken incubators and chemical furnaces. In 1745, the windmill was improved by blacksmith Edmund Lee, who added a fantail to keep the face of the windmill pointing into the wind. In 1787, Tom Mead regulated the rotation speed of a windmill by using a centrifugal pendulum to adjust the distance between the bedstone and the runner stone (i.e., to adjust the load).

荷兰发明家克尼利厄斯·雅布斯纵·戴博尔 Cornelius Drebbel (1572-1633)制造了恒温器(c1620)用于控制鸡的孵化器和化学炉的温度。1745年，铁匠埃德蒙·李 Edmund Lee对风车进行了改进，他增加了一个扇形尾翼，使风车的正面始终面向风。1787年，汤姆·米德Tom Mead通过使用离心摆调节基石和动石之间的距离(即调节负荷)来调节风车的转速。

The use of the [[centrifugal governor]] by [[James Watt]] in 1788 to regulate the speed of his [[steam engine]] was one factor leading to the [[Industrial Revolution]]. Steam engines also use float valves and [[relief valve|pressure release valves]] as mechanical regulation devices. A [[mathematical analysis]] of Watt's governor was done by [[James Clerk Maxwell]] in 1868.<ref name=maxwell/>

The use of the centrifugal governor by James Watt in 1788 to regulate the speed of his steam engine was one factor leading to the Industrial Revolution. Steam engines also use float valves and pressure release valves as mechanical regulation devices. A mathematical analysis of Watt's governor was done by James Clerk Maxwell in 1868.

1788年，詹姆斯·瓦特 James Watt 使用离心调速器来调节他的蒸汽机的速度是导致工业革命的一个因素。蒸汽发动机也使用浮阀和泄压阀作为机械调节装置。詹姆斯·克拉克·麦克斯韦 James Clerk Maxwell在1868年对瓦特的调节器进行了数学分析。<ref name=maxwell/>

The ''[[SS Great Eastern|Great Eastern]]'' was one of the largest steamships of its time and employed a steam powered rudder with feedback mechanism designed in 1866 by [[John McFarlane Gray]]. [[Joseph Farcot]] coined the word ''[[Servomechanism|servo]]'' in 1873 to describe steam-powered steering systems. Hydraulic servos were later used to position guns. [[Elmer Ambrose Sperry]] of the [[Sperry Corporation]] designed the first [[autopilot]] in 1912. [[Nicolas Minorsky]] published a theoretical analysis of automatic ship steering in 1922 and described the [[PID controller]].<ref name="Minorsky">{{cite journal |author=Minorsky, Nicolas |year=1922 |title=Directional stability of automatically steered bodies |journal=J. Amer. Soc of Naval Engineers |volume=34 |issue= 2|pages=280–309 |doi= 10.1111/j.1559-3584.1922.tb04958.x}}</ref>

The 'Great Eastern'' was one of the largest steamships of its time and employed a steam powered rudder with feedback mechanism designed in 1866 by John McFarlane Gray. Joseph Farcot coined the word ''servo'' in 1873 to describe steam-powered steering systems. Hydraulic servos were later used to position guns. Elmer Ambrose Sperry of the Sperry Corporation designed the first autopilot in 1912. Nicolas Minorsky published a theoretical analysis of automatic ship steering in 1922 and described the PID controller.

“Great Eastern”是当时最大的汽轮之一，并采用了由[[约翰·麦克法兰·格雷 John McFarlane Gray]]在1866年设计的带有反馈机制的蒸汽舵。约瑟夫·法尔科 [Joseph Farcot在1873年创造了“ 伺服系统 servo”一词来描述蒸汽动力转向系统，后来伺服系统被用来定位喷枪。斯佩里公司 Sperry Corporatio的[埃尔默·安布罗斯·斯佩里Elmer Ambrose Sperry在1912年设计了的第一台自动驾驶仪 autopilot。尼古拉斯·米诺尔斯基 Nicolas Minorsky在1922年发表了关于自动船舶操纵的理论分析，并描述了PID控制器]。<ref name="Minorsky">{{cite journal |author=Minorsky, Nicolas |year=1922 |title=Directional stability of automatically steered bodies |journal=J. Amer. Soc of Naval Engineers |volume=34 |issue= 2|pages=280–309 |doi= 10.1111/j.1559-3584.1922.tb04958.x}}</ref>

Internal combustion engines of the late 20th century employed mechanical feedback mechanisms such as the [[Ignition timing#Vacuum timing advance|vacuum timing advance]] but mechanical feedback was replaced by electronic [[engine control unit|engine management systems]] once small, robust and powerful single-chip [[microcontroller]]s became affordable.

Internal combustion engines of the late 20th century employed mechanical feedback mechanisms such as the vacuum timing advance but mechanical feedback was replaced by electronic engine management systems once small, robust and powerful single-chip microcontrollers became affordable.

20世纪后期的内燃机采用了机械反馈机制，如真空定时推进，但当小型、坚固和功能强大的单片机变得经济实惠，机械反馈就被电子发动机管理系统所取代。

===Electronic engineering===
电子工程

[[File:Ideal feedback model.svg|thumb|The simplest form of a feedback amplifier can be represented by the ''ideal block diagram'' made up of [https://www.google.com/search?tbo=p&tbm=bks&q=%22A+unilateral+block+or+network+is+one+in+which+power+may+be+transmitted+in+one+direction+only.%22&num=10&gws_rd=ssl unilateral elements].<ref name="Chen">{{cite book|title=Circuit Analysis and Feedback Amplifier Theory|author=Wai-Kai Chen|publisher=CRC Press|year=2005|isbn=9781420037272|location=423825181|pages=13–1|chapter=Chapter 13: General feedback theory|quote=[In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.|chapter-url=https://books.google.com/books?id=ZlJM1OLDQx0C&pg=SA13-PA1}}
</ref>|280px|right]]

[[File:Ideal feedback model.svg|thumb|反馈放大器的最简单形式可以用由单向元件组成的“理想框图”来表示。<ref name="Chen">{{cite book|title=Circuit Analysis and Feedback Amplifier Theory|author=Wai-Kai Chen|publisher=CRC Press|year=2005|isbn=9781420037272|location=423825181|pages=13–1|chapter=Chapter 13: General feedback theory|quote=[In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.|chapter-url=https://books.google.com/books?id=ZlJM1OLDQx0C&pg=SA13-PA1}}
</ref>|280px|right]]

The use of feedback is widespread in the design of [[electronics|electronic]] components such as [[amplifier]]s, [[oscillator]]s, and stateful [[logic circuit]] elements such as [[flip-flop (electronics)|flip-flop]]s and [[counter (digital)|counter]]s. Electronic feedback systems are also very commonly used to control mechanical, thermal and other physical processes.

The use of feedback is widespread in the design of electronic components such as amplifiers, oscillators, and stateful logic circuit elements such as flip-flops and counters. Electronic feedback systems are also very commonly used to control mechanical, thermal and other physical processes.

反馈在电子元件设计中的应用非常广泛，例如放大器、振荡器和有状态逻辑电路元件，例如触发器和计数器。电子反馈系统也非常常用于控制机械，热和其他物理过程。

If the signal is inverted on its way round the control loop, the system is said to have ''[[negative feedback amplifier|negative feedback]]'';<ref name=KalS>{{cite book |title=Basic Electronics: Devices, Circuits and IT Fundamentals |author=Santiram Kal |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+called+negative+feedback%22+%22if+the+feedback+signal+reduces+the+input+signal%22&pg=PA191 |quote=If the feedback signal reduces the input signal, ''i.e.'' it is out of phase with the input [signal], it is called negative feedback. |isbn=9788120319523 |year=2009 |publisher=PHI Learning Pvt. Ltd |page=191}}</ref> otherwise, the feedback is said to be ''positive''. Negative feedback is often deliberately introduced to increase the [[BIBO stability|stability]] and accuracy of a system by correcting or reducing the influence of unwanted changes. This scheme can fail if the input changes faster than the system can respond to it. When this happens, the lag in arrival of the correcting signal can result in over-correction, causing the output to [[oscillation|oscillate]] or "hunt".<ref>With mechanical devices, hunting can be severe enough to destroy the device.</ref> While often an unwanted consequence of system behaviour, this effect is used deliberately in electronic oscillators.

If the signal is inverted on its way round the control loop, the system is said to have negative feedback; otherwise, the feedback is said to be positive. Negative feedback is often deliberately introduced to increase the stability and accuracy of a system by correcting or reducing the influence of unwanted changes. This scheme can fail if the input changes faster than the system can respond to it. When this happens, the lag in arrival of the correcting signal can result in over-correction, causing the output to oscillate or "hunt". While often an unwanted consequence of system behaviour, this effect is used deliberately in electronic oscillators.

如果信号在绕过控制环路的过程中发生了反转，则称系统有负反馈；<ref name=KalS>{{cite book |title=Basic Electronics: Devices, Circuits and IT Fundamentals |author=Santiram Kal |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+called+negative+feedback%22+%22if+the+feedback+signal+reduces+the+input+signal%22&pg=PA191 |quote=If the feedback signal reduces the input signal, ''i.e.'' it is out of phase with the input [signal], it is called negative feedback. |isbn=9788120319523 |year=2009 |publisher=PHI Learning Pvt. Ltd |page=191}}</ref>否则，称反馈为正反馈。负反馈常常被刻意引入，通过纠正或减少不需要的变化的影响来提高系统的稳定性和准确性如果输入的变化速度快于系统对它的响应速度，这种方案就会失效。当这种情况发生时，校正信号到达的滞后可能导致过度校正，导致输出振荡或“捕获”。<ref>With mechanical devices, hunting can be severe enough to destroy the device.</ref>虽然这种效应通常是系统行为不希望出现的结果，但它却被有意地用于电子振荡器中。

[[Harry Nyquist]] at [[Bell Labs]] derived the [[Nyquist stability criterion]] for determining the stability of feedback systems. An easier method, but less general, is to use [[Bode plot]]s developed by [[Hendrik Wade Bode|Hendrik Bode]] to determine the [[Gain margin|gain margin and phase margin]]. Design to ensure stability often involves [[frequency compensation]] to control the location of the [[pole (complex analysis)|pole]]s of the amplifier.

Harry Nyquist at Bell Labs derived the Nyquist stability criterion for determining the stability of feedback systems. An easier method, but less general, is to use Bode plots developed by Hendrik Bode to determine the gain margin and phase margin. Design to ensure stability often involves frequency compensation to control the location of the poles of the amplifier.

贝尔实验室的哈里·奈奎斯特 Harry Nyquist 推导出了判定反馈系统稳定性的 奈奎斯特稳定判据 Nyquist stability criterion Chaos theory。一个比较简单但不太常用的方法是使用亨德里克博德 Hendrikbode 开发的 Bode 图来确定增益裕度和相位裕度。保证稳定性的设计往往使用频率补偿来控制放大器的极点位置。

Electronic feedback loops are used to control the output of [[electronics|electronic]] devices, such as [[amplifiers]]. A feedback loop is created when all or some portion of the output is fed back to the input. A device is said to be operating ''open loop'' if no output feedback is being employed and ''closed loop'' if feedback is being used.<ref>P. Horowitz & W. Hill, ''The Art of Electronics'', Cambridge University Press (1980), Chapter 3, relating to operational amplifiers.</ref>

Electronic feedback loops are used to control the output of electronic devices, such as amplifiers. A feedback loop is created when all or some portion of the output is fed back to the input. A device is said to be operating open loop if no output feedback is being employed and closed loop if feedback is being used.

电子反馈回路用于控制电子设备的输出，如放大器。当所有或部分输出反馈到输入时，就形成了一个反馈回路。如果没有采用输出反馈，则称为开环运行，如果采用反馈，则称为闭环运行。<ref>P. Horowitz & W. Hill, ''The Art of Electronics'', Cambridge University Press (1980), Chapter 3, relating to operational amplifiers.</ref>

When two or more amplifiers are cross-coupled using positive feedback, complex behaviors can be created. These ''[[multivibrator]]s'' are widely used and include:

When two or more amplifiers are cross-coupled using positive feedback, complex behaviors can be created. These multivibrators are widely used and include:

当两个或两个以上的放大器使用正反馈进行交叉耦合时，可以产生复杂的行为。这些多谐振荡器被广泛使用，包括:

* astable circuits, which act as oscillators
*非稳态电路，作为振荡器使用

* monostable circuits, which can be pushed into a state, and will return to the stable state after some time
* 单稳态电路，可以将其推入一个状态，并在一段时间后恢复到稳定状态。

* bistable circuits, which have two stable states that the circuit can be switched between
* 双稳态电路，它有两个稳定的状态，电路可以在这两个状态之间切换。

====Negative feedback====
负反馈

A Negative feedback occurs when the fed-back output signal has a relative phase of 180° with respect to the input signal (upside down). This situation is sometimes referred to as being ''out of phase'', but that term also is used to indicate other phase separations, as in "90° out of phase". Negative feedback can be used to correct output errors or to desensitize a system to unwanted fluctuations.<ref name=Bhattacharya>For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}</ref> In feedback amplifiers, this correction is generally for waveform [[distortion]] reduction{{citation needed|date=October 2014}} or to establish a specified [[Gain (electronics)|gain]] level. A general expression for the gain of a negative feedback amplifier is the [[asymptotic gain model]].

A Negative feedback occurs when the fed-back output signal has a relative phase of 180° with respect to the input signal (upside down). This situation is sometimes referred to as being out of phase, but that term also is used to indicate other phase separations, as in "90° out of phase". Negative feedback can be used to correct output errors or to desensitize a system to unwanted fluctuations. In feedback amplifiers, this correction is generally for waveform distortion reduction or to establish a specified gain level. A general expression for the gain of a negative feedback amplifier is the asymptotic gain model.

当反馈的输出信号相对于输入信号有180°的相对相位（上下颠倒）时，就会出现负反馈。这种情况有时被称为失相，但该术语也用于表示其他相位分离，如 "90°失相"。负反馈可用于纠正输出误差或使系统对不需要的波动脱敏。<ref name=Bhattacharya>For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}</ref>在反馈放大器中，这种校正一般是为了减少波形失真或建立一个指定的增益水平。负反馈放大器的增益的一般表达式是渐进增益模型。

====Positive feedback====
正反馈

Positive feedback occurs when the fed-back signal is in phase with the input signal. Under certain gain conditions, positive feedback reinforces the input signal to the point where the output of the device [[oscillates]] between its maximum and minimum possible states. Positive feedback may also introduce [[hysteresis]] into a circuit. This can cause the circuit to ignore small signals and respond only to large ones. It is sometimes used to eliminate noise from a digital signal. Under some circumstances, positive feedback may cause a device to latch, i.e., to reach a condition in which the output is locked to its maximum or minimum state. This fact is very widely used in digital electronics to make [[Flip-flop (electronics)|bistable]] circuits for volatile storage of information.

Positive feedback occurs when the fed-back signal is in phase with the input signal. Under certain gain conditions, positive feedback reinforces the input signal to the point where the output of the device oscillates between its maximum and minimum possible states. Positive feedback may also introduce hysteresis into a circuit. This can cause the circuit to ignore small signals and respond only to large ones. It is sometimes used to eliminate noise from a digital signal. Under some circumstances, positive feedback may cause a device to latch, i.e., to reach a condition in which the output is locked to its maximum or minimum state. This fact is very widely used in digital electronics to make bistable circuits for volatile storage of information.

当反馈信号与输入信号同相时，就会产生正反馈。在一定的增益条件下，正反馈增强输入信号，使器件的输出在其最大和最小可能状态之间振荡。正反馈也可能在电路中引入滞后现象。这会导致电路忽略小信号，只响应大信号。它有时被用来消除数字信号中的噪声。在某些情况下，正反馈可能导致设备闭锁，即，达到将输出锁定到其最大或最小状态的条件。这个功能在数字电子产品中被广泛应用于制作双稳态电路，用于信息的易失性存储。

The loud squeals that sometimes occurs in [[audio system]]s, [[public address system|PA systems]], and [[rock music]] are known as [[audio feedback]]. If a microphone is in front of a loudspeaker that it is connected to, sound that the microphone picks up comes out of the speaker, and is picked up by the microphone and re-amplified. If the [[loop gain]] is sufficient, howling or squealing at the maximum power of the amplifier is possible.

The loud squeals that sometimes occurs in audio systems, PA systems, and rock music are known as audio feedback. If a microphone is in front of a loudspeaker that it is connected to, sound that the microphone picks up comes out of the speaker, and is picked up by the microphone and re-amplified. If the loop gain is sufficient, howling or squealing at the maximum power of the amplifier is possible.

音响系统、扩音系统和摇滚音乐中有时会出现的响亮的尖叫声，这就是所谓的音频反馈。如果话筒在它所连接的扬声器前，话筒接收的声音就会从扬声器中传出，并被话筒结束并再次放大。如果环路增益足够，在放大器的最大功率下就可以发出啸叫或尖叫声。

====Oscillator====
振荡器

[[File:OpAmpHystereticOscillator.svg|thumb|A popular [[Relaxation oscillator#Comparator–based electronic relaxation oscillator|op-amp relaxation oscillator]].]]

[[File:OpAmpHystereticOscillator.svg|thumb|一个流行的运放弛缓振荡器]]。

An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. Oscillators convert direct current (DC) from a power supply to an alternating current signal. They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, and the sounds produced by electronic beepers and video games.

电子振荡器是一种产生周期性的、振荡信号的电子电路，通常是正弦波或方波。振荡器将电源中的直流电（DC）转换为交流信号。振荡器被广泛应用于许多电子设备中。振荡器产生的信号的常见例子包括无线电和电视发射机广播的信号，调节计算机和石英钟的时钟信号，以及电子传呼机和视频游戏产生的声音。

====Lactches and flip-flops====

A 4-bit [[ring counter using D-type flip flops]]

4位的使用d型触发器的环形计数器

A latch or a flip-flop is a circuit that has two stable states and can be used to store state information. They typically constructed using feedback that crosses over between two arms of the circuit, to provide the circuit with a state. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic. Latches and flip-flops are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems.

锁存器或触发器是具有两个稳定状态的电路，可用于存储状态信息。它们通常利用两臂电路之间交叉的反馈来构造，为电路提供一个状态。该电路可以通过施加到一个或多个控制输入的信号来改变状态，产生一个或两个输出。它是时序逻辑电路的基本存储元素。锁存器和触发器是用于计算机、通信和许多其他类型系统的数字电子系统的基本构件。

Latches and flip-flops are used as data storage elements. Such data storage can be used for storage of state, and such a circuit is described as sequential logic. When used in a finite-state machine, the output and next state depend not only on its current input, but also on its current state (and hence, previous inputs). It can also be used for counting of pulses, and for synchronizing variably-timed input signals to some reference timing signal.

锁存器和触发器用作数据存储元件。这样的数据存储可以用来存储状态，这样的电路被描述为时序逻辑电路。当用于有限状态机时，输出和下一状态不仅取决于其当前输入，还取决于其当前状态(因而也取决于以前的输入)。它也可用于脉冲的计数，以及将可变时序输入信号同步到某个参考时序信号。

Flip-flops can be either simple (transparent or opaque) or clocked (synchronous or edge-triggered). Although the term flip-flop has historically referred generically to both simple and clocked circuits, in modern usage it is common to reserve the term flip-flop exclusively for discussing clocked circuits; the simple ones are commonly called latches.

触发器可以是简单的(透明的或者不透明的)或者是计时的(同步的或者边缘触发的)。虽然触发器这个术语在历史上一直泛指简单电路和时钟电路，但在现代用法中，通常将触发器这个术语专门用于讨论时钟电路，简单的电路通常称为锁存电路。

Using this terminology, a latch is level-sensitive, whereas a flip-flop is edge-sensitive. That is, when a latch is enabled it becomes transparent, while a flip flop's output only changes on a single type (positive going or negative going) of clock edge.

使用这个术语，锁存器是电平敏感的，而触发器是边缘敏感的。也就是说，当锁存器启用时，它变得透明，而触发器的输出只在时钟边缘的单一类型(正向或负向)上发生变化。

Feedback loops provide generic mechanisms for controlling the running, maintenance, and evolution of software and computing systems. Feedback-loops are important models in the engineering of adaptive software, as they define the behaviour of the interactions among the control elements over the adaptation process, to guarantee system properties at run-time. Feedback loops and foundations of control theory have been successfully applied to computing systems. In particular, they have been applied to the development of products such as IBM's Universal Database server and IBM Tivoli. From a software perspective, the autonomic (MAPE, monitor analyze plan execute) loop proposed by researchers of IBM is another valuable contribution to the application of feedback loops to the control of dynamic properties and the design and evolution of autonomic software systems.

反馈回路为控制软件和计算系统的运行、维护和升级提供了通用机制。反馈回路是自适应软件工程中的重要模型，它定义了自适应过程中控制元件之间相互作用的行为，以保证系统在运行时的性能。反馈环路和控制理论基础已成功地应用于计算系统。特别是，它们已经应用于产品的开发，如IBM的Universal Database server和IBM Tivoli。从软件的角度来看，IBM 研究人员提出的自主(MAPE，monitor analyze plan execute)回路是对反馈回路应用于动态特性控制和自主软件系统设计与演化的又一宝贵贡献。

Feedback is also a useful design principle for designing user interfaces.

反馈也是设计用户界面时一个有用的设计原则。

Video feedback is the video equivalent of acoustic feedback. It involves a loop between a video camera input and a video output, e.g., a television screen or monitor. Aiming the camera at the display produces a complex video image based on the feedback.

视频反馈是相当于声音反馈的视频。它涉及到摄像机输入和视频输出（如电视屏幕或显示器）之间的循环。将摄像机对准显示器，会生成基于反馈的复杂的视频图像。

The stock market is an example of a system prone to oscillatory "hunting", governed by positive and negative feedback resulting from cognitive and emotional factors among market participants. For example:

股市是一个易于出现振荡 "捕猎"的系统的例子，它受市场参与者之间的认知和情感因素所产生的正负反馈所支配。例如：

George Soros used the word reflexivity, to describe feedback in the financial markets and developed an investment theory based on this principle.

乔治•索罗斯 George Soros 用“ 反身性 reflexivity servo”一词来描述金融市场的反馈，并根据这一原则发展了一套投资理论。

The conventional economic equilibrium model of supply and demand supports only ideal linear negative feedback and was heavily criticized by Paul Ormerod in his book The Death of Economics, which, in turn, was criticized by traditional economists. This book was part of a change of perspective as economists started to recognise that chaos theory applied to nonlinear feedback systems including financial markets.

传统的经济供求平衡模型只支持理想的线性负反馈，保罗·奥默罗德 Paul Ormerod在他的《经济学之死》一书中对这个模型提出了严厉的批评，而传统经济学家也对她提出了批评。随着经济学家开始认识到混沌理论适用于包括金融市场在内的非线性反馈系统，这本书成为了转变观点的一部分。