复杂用户网络在移动通信方面的应用研究

在传统的移动蜂窝系统研究中,所有用户都假设具有相同的行为,即他们以相等的概率打出/接听电话,以及他们以相同的移动性在网络内移动. 还有,基础用户网络假设为一个全互联的网络, 这暗示着所有的用户都互相认识,且以同一概率进行相互通讯. 但在现实的环境中,每个用户有各自的熟人(包括家人、亲戚、朋友和同事)通讯录,其通讯录的大小也视乎个别用户而有所不同. 此外,由于用户的移动性取决于各种各样的因素(如工作性质等),不同用户的移动程度也不尽相同. 为了估计移动系统更接近实际的性能,我们使用无尺度网络作为潜在的用户网络模型,即一个用户的熟人数目服从幂律分布,并且研究在3种移动性(即零移动性、相同移动性和幂律移动性)下的移动系统.最后, 通过计算机仿真来估计系统的性能指标(如承载话务量和阻塞率等).结果表明, 用户网络结构以及用户移动性都会对移动系统的性能产生影响.      

Phase transition in evolution of traffic flow with scale-free property

This paper investigates the behaviour of traffic flow in traffic systems with a new model based on the NaSch model and cluster approximation of mean-field theory. The proposed model aims at constructing a mapping relationship between the microcosmic behaviour and the macroscopic property of traffic flow. Results demonstrate that scale-free phenomenon of the evolution network becomes obvious when the density value of traffic flow reaches at the critical point of phase transition from free flow to traffic congestion, and jamming is limited in this scale-free structure.     

Flat-head power-law, size-independent clustering, and scaling of coevolutionary scale-free networks

Scale-free topology and high clustering coexist in some real networks, and keep invariant for growing sizes of the systems. Previous models could hardly give out size-independent clustering with selforganized mechanism when succeeded in producing power-law degree distributions. Always ignored, some empirical statistic results display flat-head power-law behaviors. We modify our recent coevolutionary model to explain such phenomena with the inert property of nodes to retain small portion of unfavorable links in self-organized rewiring process. Flat-head power-law and size-independent clustering are induced as the new characteristics by this modification. In addition, a new scaling relation is found as the result of interplay between node state growth and adaptive variation of connections.     

BA无标度网络中的SIR模型

网络化是现代世界的一个重要特征,不仅包括互联网,还包括航空网,人际关系网,而它们都是很典型的无标度网络.在BA无标度网中,结合经典的SIR模型,建立了新的SIR模型,并对模型进行了研究,得到了BA无标度网络对传染病与计算机病毒传播具有脆弱性的结论.     

Weighted scale-free networks induced by group preferential mechanism

Based on the BBV model [A. Barrat, M. Barthelemy, A. Vespignani, Phys. Rev. Lett. 92 (22) (2004)], we propose a weighted group preferential model, which is generated by the group preferential mechanism. We derive analytically the various statistical properties, such as the distribution of degree, strength and weight, the degree-strength relationship. Finally, we provide a contrast with the BBV model on the synchronization robustness and fragility through numerical simulation.     

一门崭新的交叉科学:网络科学(上)

本文试图比较系统地概括和评述正在兴起的一门崭新的交叉科学—网络科学,内容涉及网络科学的发展简史,基本概念,网络分类,主要理论模型及其特性,目前国内外该领域的若干重要课题的研究进展概况。全文结构分为:序言,主体部分共12章,最后是结束语,分别概述和涵盖网络科学的主要课题的研究成果和近年的进展,特别是着重介绍和总结了我们"一院二校"(原子能科研院、上海交大和北京师大)国家自然科学基金重点项目联合研究组开展的复杂网络研究所取得的若干成果和进展。分两期发表,下篇请见《物理学进展》27卷4期。     

Delay of Social Search on Small-World Graphs

This article introduces an analytical framework for two small-world network models and studies the delay of targeted social search by considering messages traveling between source and target individuals in these networks. In particular, by considering graphs constructed on different network domains, such as rectangular, circular, and spherical network domains, analytical solutions for the average social search delay and the delay distribution are obtained as functions of source–target separation, distribution of the number of long-range connections and geometrical properties of network domains. Derived analytical formulas are first verified by agent-based simulations and then compared with empirical observations in small-world experiments. These formulas indicate that individuals tend to communicate with one another only through their short-range contacts and the average social search delay rises linearly, when the separation between the source and target is small. As this separation increases long-range connections are more commonly used, and the average social search delay rapidly saturates to a constant value and stays almost the same for all large values of the separation. These results do not require the dimensionality of the social space to be identical to the decay exponent of long-range social connections and are qualitatively consistent with experimental observations made by Travers and Milgram in 1969 Travers , J. , &; Milgram , S. ( 1969 ). An experimental study of the small world problem . Sociometry , 32 , 425 – 443 .[Crossref] , [Google Scholar] as well as by others. Moreover, analytical distributions for the delay of social search predicted by the models introduced in this article are also compared with corresponding empirical distributions, and good statistical matches between them are observed. Other somewhat surprising conclusions of the article are that hubs have limited effect in reducing the delay of social search and variation in node degree distribution adversely affects this delay.     

Co-evolution of the brand effect and competitiveness in evolving networks

The principle that ‘the brand effect is attractive’ underlies the preferential attachment. Here we show that the brand effect is just one dimension of attractiveness. Another dimension is competitiveness. We firstly introduce a general framework that allows us to investigate the competitive aspect of real networks, instead of simply preferring popular nodes. Our model accurately describes the evolution of social and technological networks. The phenomenon that more competitive nodes become richer can help us to understand the evolution of many competitive systems in nature and society. In general,the paper provides an explicit analytical expression of degree distributions of the network. In particular, the model yields a nontrivial time evolution of nodes’ properties and the scale-free behavior with exponents depending on the microscopic parameters characterizing the competition rules. Secondly, through theoretical analyses and numerical simulations, we reveal that our model has not only the universality for the homogeneous weighted network, but also the character for the heterogeneous weighted network. Thirdly, we also develop a model based on the profit-driven mechanism. It can better describe the observed phenomenon in enterprise cooperation networks. We show that the standard preferential attachment,the growing random graph, the initial attractiveness model, the fitness model, and weighted networks can all be seen as degenerate cases of our model.     

肿瘤免疫无标度网络模型平衡点存在性及应用

应用无标度网络,建立肿瘤-免疫网络模型,来刻画免疫效应细胞、肿瘤细胞与细胞因子相互作用的机理。研究了网络模型的肿瘤平衡点在免疫效应细胞与细胞因子度关联与度非关联两种情况下的存在条件.得到了根据所得到的肿瘤平衡点存在的临界值,根据临界值提出免疫途径与方法,为抑制或预测肿瘤生长提供的理论参考.     

An evolving network model with modular growth

In this paper, we propose an evolving network model growing fast in units of module, according to the analysis of the evolution characteristics in real complex networks. Each module is a small-world network containing several interconnected nodes and the nodes between the modules are linked by preferential attachment on degree of nodes. We study the modularity measure of the proposed model, which can be adjusted by changing the ratio of the number of inner-module edges and the number of inter-module edges. In view of the mean-field theory, we develop an analytical function of the degree distribution, which is verified by a numerical example and indicates that the degree distribution shows characteristics of the small-world network and the scale-free network distinctly at different segments. The clustering coefficient and the average path length of the network are simulated numerically, indicating that the network shows the small-world property and is affected little by the randomness of the new module.