Complex cyber-physical networks: From cybersecurity to security control

Complex cyber-physical network refers to a new generation of complex networks whose normal functioning significantly relies on tight interactions between its physical and cyber components. Many modern critical infrastructures can be appropriately modelled as complex cyber-physical networks. Typical examples of such infrastructures are electrical power grids, WWW, public transportation systems, state financial networks, and the Internet. These critical facilities play important roles in ensuring the stability of society as well as the development of economy. Advances in information and communication technology open opportunities for malicious attackers to launch coordinated attacks on cyber-physical critical facilities in networked infrastructures from any Internet-accessible place. Cybersecurity of complex cyber-physical networks has emerged as a hot topic within this context. In practice, it is also very crucial to understand the interplay between the evolution of underlying network structures and the collective dynamics on these complex networks and consequently to design efficient security control strategies to protect the evolution of these networks. In this paper, cybersecurity of complex cyber-physical networks is first outlined and then some security enhancing techniques, with particular emphasis on safety communications, attack detection and fault-tolerant control, are suggested. Furthermore, a new class of efficient secure control strategies are proposed for guaranteeing the achievement of desirable pinning synchronization behaviors in complex cyber-physical networks against malicious attacks on nodes. The authors hope that this paper motivates to design enhanced security strategies for complex cyber-physical network systems, to realize resilient and secure critical infrastructures.     

动态影响力下网络舆论传播的计算实验研究

基于以往研究较少考虑影响力的即时动态更新,对于网络舆论传播的某些现象,可以融入这一因素进行分析.借鉴Krause有界信任的思想,引入Festinger的认知不一致理论对观点交互条件进行改进,并对信任阈值的作用进行了重新认识.本文认为,信任阈值并非判定个体是否交互的分界线,而是决定影响力增大或减小的分割线.进一步,对影响力的动态性进行了深入研究,引入短记忆过程和惩罚机制,从而构建动态影响力下的网络舆论传播模型,进行了计算实验分析.结果表明:随着群体信任闽值的提高,观点分化程度降低.群体观点演化也受初始影响力分布影响,初始影响力较高,网络群体更容易形成稳定的观点,且收敛速度更快.而投入干预个体的影响作用与群体信任阈值负相关,与干预个体所占的比例正相关.     

企业社会责任负面事件网络舆情演化与政企合作研究

企业社会责任负面事件网络舆情演化具有主体行为复杂性,是动态的复杂网络系统,把握舆情演化过程中主体的行为特征和互动关系有助于舆情管理.本文以企业、政府、民众、媒体和意见领袖五个主体为节点,以不同主体之间交互关系为路径,构建了企业社会责任负面事件网络舆情演化的多主体模型.选取"百度魏则西"为基础事件,采用系统动力学理论和方法,探究了企业社会责任负面事件网络舆情的演化过程和系统结构中的动力学行为.研究结果表明:企业社会责任负面事件网络舆情演化总体呈现了诱发、扩散和消退三个阶段的周期性过程.企业与利益相关者之间的交互作用是推动舆情演化的主要动因,其中企业和政府作为两个重要的行为主体,在联动的时点选择上,按照政府调控行为在先、企业应对行为在后的方式,能有效发挥政府的调控作用和企业的主观能动性,缓解舆论危机.     

多层同步网络在舆情仿真研究中的应用

为统筹考虑线上社交网络与线下社交网络在舆情传播中的作用,首次提出了一种包含"媒体层-线上层-线下层"的多层同步网络模型,并在此基础上搭建了舆情仿真系统框架.基于对人类社交网络拓扑结构的已有研究成果,给出了多层同步网络的缺省设定.通过案例仿真,分析了线上网络与线下网络之间的相互影响,对比了舆情事件目击者数量在多媒体传播、自媒体传播这两种舆论传播模式中的作用差异.最后,讨论了多层同步网络模型的兼容性与可扩展性,并指出了该模型改进的方向.     

A complex systems science perspective on wireless networks

The paper targets a future world where all wireless networks are self-organising entities and in which the predominant mode of spectrum access is dynamic. The paper explores whether the behaviour of a collection of autonomous self-organising wireless systems can be treated as a complex system and whether complex systems science can shed light on the design and deployment of these networks. The authors focus on networks that self-organise from a frequency perspective to understand the behaviour of a collection of wireless self-organising nodes. Each autonomous network is modelled as a cell in a lattice and follows a simple set of self-organisation rules. Two scenarios are considered, one in which each cell is based on cellular automata and which provides an abstracted view of interference and a second in which each cell uses a self-organising technique which more accurately accounts for interference. The authors use excess entropy to measure complexity and in combination with entropy gain an understanding of the structure emerging in the lattice for the self-organising networks. The authors show that the self-organising systems presented here do exhibit complex behaviour. Finally, the authors look at the robustness of these complex systems and show that they are robust against changes in the environment.     

Statistical Identification of Important Nodes in Biological Systems

Biological systems can be modeled and described by biological networks. Biological networks are typical complex networks with widely real-world applications. Many problems arising in biological systems can be boiled down to the identification of important nodes. For example, biomedical researchers frequently need to identify important genes that potentially leaded to disease phenotypes in animal and explore crucial genes that were responsible for stress responsiveness in plants. To facilitate the identification of important nodes in biological systems, one needs to know network structures or behavioral data of nodes(such as gene expression data). If network topology was known, various centrality measures can be developed to solve the problem; while if only behavioral data of nodes were given, some sophisticated statistical methods can be employed. This paper reviewed some of the recent works on statistical identification of important nodes in biological systems from three aspects, that is,1) in general complex networks based on complex networks theory and epidemic dynamic models; 2)in biological networks based on network motifs; and 3) in plants based on RNA-seq data. The identification of important nodes in a complex system can be seen as a mapping from the system to the ranking score vector of nodes, such mapping is not necessarily with explicit form. The three aspects reflected three typical approaches on ranking nodes in biological systems and can be integrated into one general framework. This paper also proposed some challenges and future works on the related topics. The associated investigations have potential real-world applications in the control of biological systems, network medicine and new variety cultivation of crops.     

基于复合边权重的加权复杂网络级联抗毁性优化

针对加权网络级联抗毁性问题,融合对级联失效动力学过程有重要影响的节点度和介数两种指标,提出一种节点度和介数相关的边权重模型,该模型通过定义调整两种指标占边权比重的参数,以及调整网络异质度的权重参数,使得边对故障引起的额外负载的承载能力更强。理论分析与仿真结果表明，存在某一权重参数以及比重系数取值使得BA无标度网络和NW小世界网络鲁棒性达到最强;相比单一指标边权方法,提出的模型能够更加有效地提升网络级联抗毁性能。     

基于数据爬虫与动态社会网络的公众环保行为演化研究

本文运用数据爬虫技术与社会网络分析方法对一个豆瓣公众环境保护小组的信息交互及相应的动态社会网络演化过程进行刻画,并在基于计划行为理论的绿色出行行为意愿模型的基础上:对嵌入在动态社会网络中的公众环保行为演化规律进行了研究.结果表明:在公众环境保护小组的社会网络形成过程中,社会网络的拓扑结构由最初的小世界网络特征迅速演变成为无标度网络特征;降低社会网络中行为主体的信息交互阈值、公众环保信息的差异程度、行为主体的易受影响程度将有利于公众环保豆瓣小组社会网络中信息的有效传播,行为主体对于公众环保信息的掌握与认知将能演化达到更加理想的状态,也将有利于促进公众环保行为的推广.     

基于贝叶斯学习的复杂系统研制风险演化分析

大型复杂装备的系统结构和研制流程呈现网络化特征,研究风险演化机理有助于控制风险、降低复杂性.通过系统动态过程建模仿真获取数据样本,运用贝叶斯学习从仿真数据样本中提炼风险演化网络,识别不同风险等级的节点之间存在的关联关系,降低了仅凭经验构建风险网络的主观性.对贝叶斯学习获得的风险网络进行概率推理,在总体高风险等级下计算风险网络节点的风险后验概率分布,进而确定风险演化关键节点和传播链路.最后,通过与复杂网络特征指标评估下的静态特征进行对比分析,研究风险网络动态特征与静态特征的差异性,结果表明网络结构特征和风险传播的动态特征共同决定了风险演化关键节点和传播链路.     

泛在媒体环境下的网络舆情传播控制模型

正逐步形成的泛在媒体环境深刻影响着网络舆情的传播与控制.将传统的传染病模型推广到泛在媒体环境这样一个开放系统中, 建立了新的带直接免疫的SEIR舆情传播控制模型, 新模型克服了已有网络舆情传播模型存在的对网民个体状态处理过于简单, 对舆情传播媒介的处理过于简化等缺陷.证明了模型的传播平衡点及稳定性, 提出了从网络舆情传播环境入手, 在舆情形成初期进行干预的控制方法.据此, 构建了基于Wiki技术的网络舆情传播控制平台, 对该平台的舆情传播控制效能做了仿真剖析, 验证了控制方法的有效性.     

基于用户相对权重的在线社交网络舆情传播控制模型

在线社交网络(online social networks,OSN)中舆情传播干预时机的选择对网络舆情的管控具有重要意义.通过分析用户的网络地位、社会强化效应与用户感知价值等影响网络舆情传播控制的关键因素,以研究舆情管控的合理干预时机为目的,构建了基于用户相对权重的网络舆情传播控制模型.基于该模型,针对两类OSN开展仿真研究.研究发现,网络舆情传播与信息初始传播源的网络地位密切相关;在开放式OSN中,存在与干预时机选择关系密切的关键相变点;用户活跃度随社会强化效应强度的增大而下降,随干预时机的提前而降低,并存在有效干预时机区间;"悖民意"成本是干预时机选择的重要衡量指标.并据此,提出了相应现实干预时机选择的对策建议.     

基于超网络的舆论演化动态模型

针对舆论演化过程中的复杂动力学问题,提出了超网络视觉下的舆论演化动态模型,该模型包括节点的添加、重新连接链路、超边的添加以及节点的老化4个过程,其中节点代表关键词,超边代表关键词所构成的话题。其次,利用非均匀网络的演化机制,分别对该动态演化模型的超度、节点自身关注度与节点间影响力两个因素的超度进行了详细的理论分析,分析结果表明节点超度完全符合幂律分布。最后,通过Matlab仿真模拟,分析了不同参数对节点超度分布变化的影响,并进一步验证了结果是遵循幂律分布的。     

元胞自动机舆论模型中人员移动对传播的影响

为了研究舆论系统中人员的移动以及存在态度坚定者的因素对舆论形成和演化的影响,建立了相应的元胞自动机舆论模型．在假设人员态度的改变方式遵守少数服从多数的规则下,通过计算机模拟给出了二维四方格子两种影响领域(5邻居、9邻居)在周期性边界条件下的舆论传播行为．模拟给出了模型的演化趋势,以及在不同赞成率的随机初始状态中,模型演化随立场坚定者密度变化的行为．结果表明人员的移动将加快舆论的形成．     

基于不确定微分方程的网络舆情传播模型研究

不确定微分方程是由典范过程驱动的一类微分方程,是一种描述不确定过程或不确定动态系统的新型数学工具.本文在研究网络舆情传播过程和传播类型的基础上,充分考虑网络舆情传播过程中存在的一些不确定因素,根据网络舆情传播的不同阶段提出相应的基于不确定微分方程的网络舆情传播模型.最后结合甘肃兰州自来水苯含量超标事件给出了衰退阶段模型的数值计算实例,预测结果与实际传播情况基本吻合.     

舆情传播与应急决策的结构化描述及其相互作用规律

运用多案例分析方法从属性层次提出了舆情传播和应急决策的结构化描述方法,进而借助"情景-应对"研究范式,刻画了二者的相互作用机制,分析了二者的博弈关系.然后,考虑到博弈双方的行为具有动态性、多目标、目标偏好和公平偏好,引入演化博弈论方法研究了舆情传播和应急决策之间的相互作用规律.进一步,运用实际案例验证了理论研究的有效性,并运用仿真方法考查了该案例中博弈双方的目标偏好行为和公平偏好行为对演化博弈稳定性的影响.     

基于二分图的城市公交网络拓扑性质研究

以北京市公交系统为例,用二分图模型对其进行描述,分别构建出公交站点网络和公交线路网络,对二分图、公交站点网络和公交线路网络进行了度的分布、集聚系数以及平均路径长度等拓扑参数的计算,并与规则网络和随机网络进行了比较,发现北京市公交系统具有"小世界"网络的性质.最后深入地研究了公交线路网络与公交站点网络拓扑参数形成的机理.     

基于超网络的线上线下舆情演化模型研究

舆情交互存在于现实空间与虚拟空间,为具体研究两空间中舆情的演化,首先分析了舆情在不同空间中传播演化的特点及演化过程中相互间的联系.随后,结合改进的有界信任机制构建基于超网络的线上线下舆情演化模型,并针对该模型提出了包括模型初始化模块、信息传播与交互影响模块与双空间同步模块三部分的仿真系统框架.根据同步方向,提出"现实空间-虚拟空间"和"虚拟空间-现实空间"两种同步率,并通过对比仿真实验研究了同步率与空间速度比对舆情演化的影响.     

Preventing rumor spreading on small-world networks

Since the spreading of harmful rumors can deeply endanger a society, it is valuable to investigate strategies that can efficiently prevent hazardous rumor propagation. To conduct this investigation, the authors modify the SIR model to describe rumor propagation on networks, and apply two major immunization strategies, namely, the random immunization and the targeted immunization to the rumor model on a small-world network. The authors find that when the average degree of the network is small, both two strategies are effective and when the average degree is large, neither strategy is efficient in preventing rumor propagation. In the latter case, the authors propose a new strategy by decreasing the credibility of the rumor and applying either the random or the targeted immunization at the same time. Numerical simulations indicate that this strategy is effective in preventing rumor spreading on the small-world network with large average degree.     

Adaptive Control of the Structural Balance for a Class of Complex Dynamical Networks

In social networks, the structural balance is a state of a group of individuals(nodes) with established mutual relationships(connection relationships) between them. It is easy to see that a social network can be described by a complex dynamical network model composed of the nodes subsystem(NS) and the connection relationships subsystem(CS), where the two subsystems are usually coupled with each other. It implies that the dynamic changes of nodes' states may cause the structural balance in CS. However, few papers have discussed the relationship between the structural balance and the specific dynamic changes of the nodes' states. This paper proposes a model of complex dynamical networks, and mainly focuses on the dynamic changes of states in NS which can lead to the structural balance in CS. It is proved that if each state in NS is doing a specific dynamic motion via the controller with the parameter adaptive law, then the CS can track a given structural balance matrix via the effective coupling and the structural balance can be achieved. Such a result can be regarded as an explanation of the relationship between the structural balance and the specific dynamic changes of the nodes' states. Finally, the simulations verify the effectiveness of the proposed method.     

双层社会网络上的舆情传播动力学分析

本文构建了由线上社交网络和线下物理接触网络构成的双层社会网络模型,通过理论分析计算出稳态时的舆情传播者比例,得到双层社会网络上的舆情传播阈值大于单层线上网络舆情传播阈值,而小于单层线下网络舆情传播阈值.仿真实验结果表明,在线社交网络能够扩大舆情传播范围、加快舆情传播速度.各层子网的传播率对另一层网络中传播者比例几乎没有影响.此外,来自于线下网络的传播者转移率对舆情传播过程的影响作用小于来自于线上网络的传播者转移率.