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将一个疏松多孔的材料放入水中, 水能否渗入材料中呢? 1957年, 布鲁德本特(Broadbent)和哈默斯利(Hammersley)给出了一个简单的模型用以讨论这个问题, 即所谓的逾渗模型(percolation model)。如图1所示, 他们的模型建立在一个二维的方格子上。模型中的节点表示材料中的空隙。为了模拟材料中空隙的连通, 假设方格子中相邻节点(每个节点有四个邻居)以概率p(0<p<1)相连。模型中, 一对相邻节点相连称为占据相应的边。如图1所示, 如果只标出占据边, 原系统就被分为若干个由占据边连接的节点集团, 一般称为连通集团。一个连通集团中的节点数称为该集团的大小。如果水能渗入材料中, 模型中必然会有一个与原系统大小相当的连通集团贯穿整个二维格子, 这样的集团一般称为巨分量(giant component)。这样, 水能否渗入材料的问题就简化为占据概率p与巨分量存在性的关系问题。 相似文献
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Effects of inforination asymmetry on cooperation in the prisoners' dilemma game are investigated. The amplitude A is introduced to describe the degree of information asymmetry. It is found that there exists an optimal value of amplitude Aopt at which the fraction of cooperation reaches its maximal value. The reason lies in that cooperators on the two-dimensional grid form large clusters at Aopt. In addition, the theoretical analysis in terms of the mean- field theory is used to understand this kind of phenomenon. It is confirmed that the information asymmetry plays an important role in the dynamics of the dilemma games of spatial prisoners. 相似文献
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In real-world network evolution, the aging effect is universal. We propose a microscopic model for aging networks,which suggests that the activity of a vertex is the result of the competition of two factors: pullulatlon and decrepitude. By incorporating the pullulation factor into previous models of aging networks, both the global and individual aging effect curves in our model are single peaked, which agrees with the empirical data well. This model can generate networks with scale-free degree distribution, large clustering coefficient and small average distance when the decrepitude intensity is small and the network size not very large. The results of our model show that pullulation may be one of the most important factors affecting the structure and function of aging networks and should not be neglected at all. 相似文献
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如何用定量分析的方法识别超大规模网络中哪些节点最重要, 或者评价某个节点相对于其他一个或多个节点的重要程度, 这是复杂网络研究中亟待解决的重要问题之一. 本文分别从网络结构和传播动力学的角度, 对现有的复杂网络中节点重要性排序方法进行了系统的回顾,总结了节点重要性排序方法的最新研究进展, 并对不同的节点重要性排序指标的优缺点以及适用环境进行了分析, 最后指出了这一领域中几个有待解决的问题及可能的发展方向.
关键词:
复杂网络
节点重要性
网络结构
传播动力学 相似文献
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We consider the effect of clustering coefficient on the synchronizability of coupled oscillators located on scale-free networks. The analytic result for the value of clustering coefficient aiming at a highly clustered scale-free network model, the Holme-Kim model is obtained, and the relationship between network synchronizability and clustering coefficient is reported. The simulation results strongly suggest that the more clustered the network, the poorer the synchronizability. 相似文献
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基于Takens的相空间延迟坐标重构,研究了用于混沌信号预测的三阶Volterra滤波器的一种乘积耦合近似实现结构,并应用于典型的低维混沌时间序列和具有高维混沌特性的EEG信号的预测.数值研究表明:这种滤波器结构对于低维混沌时间序列的预测精度可以比二阶Volterra滤波器提高103倍,而且能够较好地对一些具有高维混沌特性的EEG信号进行预测
关键词:
混沌
非线性自适应预测
三阶Volterra滤波器
electroencephalography信号 相似文献
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Excitation Properties of the Biological Neurons with Side-Inhibition Mechanism in Small-World Networks 总被引:3,自引:0,他引:3 下载免费PDF全文
We have studied the excitation properties of biophysical Hodgkin-Huxley neurons with the side-inhibition mechanism in small-world networks. The result shows that the excitation properties in the networks are preferably consistent with the characteristic properties of a brain neural system under external constant stimuli, such as fatigue effect, extreme excitation principle, and the brain neural excitation response induced by different in- tensity of noise and coupling. The results of the study might shed some light on the study of the brain nerve electrophysiology and epistemological science. 相似文献