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[[File:Network representation of brain connectivity.JPG|thumb|right|

[[File:Network representation of brain connectivity.JPG|thumb|right|

图1：Network representation of brain connectivity. Hubs are highlighted 表示大脑连接性的网络，其中枢纽节点被突出显示]]

图1：Network representation of brain connectivity. Hubs are highlighted  

表示大脑连接性的网络，其中枢纽节点被突出显示]]

[[File:Internet map 4096.png|thumb|150px|right|

[[File:Internet map 4096.png|thumb|150px|right|

图2:Partial map of the Internet based on the January 15, 2005. Hubs are highlighted 2005年1月15日的因特网局部图，枢纽节点被突出显示]]

图2:Partial map of the Internet based on the January 15, 2005. Hubs are highlighted  

2005年1月15日的因特网局部图，枢纽节点被突出显示]]

A hub is a component of a network with a high-degree [[Vertex (graph theory)|node]]. Hubs have a significantly larger number of links in comparison with other nodes in the network. The number of links ([[Degree (graph theory)|degrees]]) for a hub in a scale-free network is much higher than for the biggest node in a random network, keeping the size ''N'' of the network and average degree ''<k>'' constant. The existence of hubs is the biggest difference between random networks and scale-free networks. In random networks, the degree ''k'' is comparable for every node; it is therefore not possible for hubs to emerge. In scale-free networks, a few nodes (hubs) have a high degree ''k'' while the other nodes have a small number of links.

A hub is a component of a network with a high-degree [[Vertex (graph theory)|node]]. Hubs have a significantly larger number of links in comparison with other nodes in the network. The number of links ([[Degree (graph theory)|degrees]]) for a hub in a scale-free network is much higher than for the biggest node in a random network, keeping the size ''N'' of the network and average degree ''<k>'' constant. The existence of hubs is the biggest difference between random networks and scale-free networks. In random networks, the degree ''k'' is comparable for every node; it is therefore not possible for hubs to emerge. In scale-free networks, a few nodes (hubs) have a high degree ''k'' while the other nodes have a small number of links.

[[Image:Scale-free network sample.png|thumb|Example of a random network and a scale-free network|400px|right|

[[Image:Scale-free network sample.png|thumb|Example of a random network and a scale-free network|400px|right|

图3：Random network (a) and scale-free network (b). In the scale-free network, the larger hubs are highlighted. 随机网络（a）和无标度网络（b），在无标度网络中，大型枢纽被突出显示]]

图3：Random network (a) and scale-free network (b). In the scale-free network, the larger hubs are highlighted.  

随机网络（a）和无标度网络（b），在无标度网络中，大型枢纽被突出显示]]

[[File:Barabasi Albert model.gif|thumb|300px|

[[File:Barabasi Albert model.gif|thumb|300px|

图4：The steps of the growth of the network according to the Barabasi–Albert model (<math>m_0=m=2</math>) 根据 Barabasi-Albert 模型 <math>m_0=m=2</math> 分析了网络生长的步骤]]

图4：The steps of the growth of the network according to the Barabasi–Albert model (<math>m_0=m=2</math>)  

根据 Barabasi-Albert 模型 <math>m_0=m=2</math> 分析了网络生长的步骤]]