网络弧生长对网络可靠性的影响

人们普遍认为,对于一般的网络图而言,当网络弧在生长时将有益于网络可靠性的增强。然而事实证明该论断并不完全正确。对于某些注重最短路径长度的网络而言:(1) 当网络>G受到随机攻击时,以网络最短路熵作为网络可靠性的判断依据,分别计算在增加一条弧前后网络结点或网络弧受到攻击而失效时的网络最短路熵,比较网络最短路熵的大小,熵值越大,可靠性越弱;(2) 当网络G受到恶意攻击时,根据悲观原则定义了一种新的可靠性指标,该指标值越大,网络可靠性越强。结果表明:(1) 当G与G'的最短路径长度相等时,G'的可靠性不弱于G;(2)当G与G'的最短路径长度不相等时,G与G'的可靠性相对大小关系不唯一。对该问题的研究有助于人们清楚的认识到网络弧生长对网络可靠性的影响。最后用简化的江苏省城市间高速公路网络图为例来说明该研究的有效性与实用性。

The Impact of Network Arc's Growth on the Network Reliabiligy

It is commonly recognized that, as to a general network, the network reliability will be increasingly enhanced when network arcs are growing. However, this argument is not entirely correct. For some researches on networks that mainly focus on shortest path length, the conclusions can be got as follows. First, if network G suffers from random attacks, the network shortest path entropy is utilized as a criterion judging the network reliability and will be computed before and after an extra arc is added when the network node or arc is attacked and thus fails. In this case, the larger the entropy value is, the weaker the reliability becomes. Second, if network G suffers from malicious attacks, a newly-defined reliability indicator is applied in accordance with pessimistic principle, which is positively correlated with network reliability. The result further shows that: when G is identical to G' in the shortest path length, then the reliability of G' is not weaker than G's; when G is not equal to G' in the shortest path length, their reliability's relative value is not unique. This study helps cultivate an in-depth understanding of the influence of network arc's growth on the network's reliability. Finally, a simplified inter-city expressway network graph of Jiangsu province is exemplified to demonstrate the effectiveness and practicability of this approach.