In order to evaluate the node importance in complex network, considering the disadvantages of node deletion method, node contraction method and betweenness method, through defining the node efficiency and the node importance evaluation matrix, a method to find the vital node in complex networks is proposed by using the node importance evaluation matrix. Considered in this method are the node efficiency, node degree and adjacent node importance contributions, and used adjacent node degree and efficiency value to characterize the contribution of their importance. Finally, an optimized algorithm whose time complexity was O(Rn2) is provided. Experiments show that this method is effective and feasible, and it is applicable to large scale complex networks.
This paper investigates the synchronization of directed networks whose coupling matrices are reducible and asymmetrical by pinning-controlled schemes. A strong sufficient condition is obtained to guarantee that the synchronization of the kind of networks can be achieved. For the weakly connected network, a method is presented in detail to solve two challenging fundamental problems arising in pinning control of complex networks: 1) How many nodes should be pinned? 2) How large should the coupling strength be used in a fixed complex network to realize synchronization? Then, we show the answer to the question that why all the diagonal block matrices of Perron-Frobenius normal matrices should be pinned? Besides, we find out the relation between the Perron-Frobenius normal form of coupling matrix and the differences of two synchronization conditions for strongly connected networks and weakly connected ones with linear coupling configuration. Moreover, we propose adaptive feedback algorithms to make the coupling strength as small as possible. Finally, numerical simulations are given to verify our theoretical analysis.
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