双环网络直径的对称性及应用

双环网络是计算机互连网络、大规模并行处理系统和通讯系统的一类重要拓扑结构。双环网络有效性的一个重要参数是信息的传输延迟,它可以用其图的直径来度量。文中从双环网络的图论模型出发,证明了双环网络中一个被广泛关注的问题,即双环网络直径的对称性,并给出了一些应用。     

双环网络直径的对称性及应用

双环网络是计算机互连网络、大规模并行处理系统和通讯系统的一类重要拓扑结构。双环网络有效性的一个重要参数是信息的传输延迟，它可以用其图的直径来度量。文中从双环网络的图论模型出发，证明了双环网络中一个被广泛关注的问题，即双环网络直径的对称性，并给出了一些应用。     

双环网络直径的对称性及其仿真算法

双环网络有效性的一个重要参数是信息的传输延迟,它可以用其图的直径来度量.从双环网络的图论模型出发,首次使用矩阵原理证明了双环网络直径的对称性,根据对称性,使搜寻最优或紧优G(N;s)的范围可以减少一半;给出了双环网络直径的仿真算法;并利用C#作为编程语言、SQL Server2000作为数据库实现了该算法.     

有向双环网和无向双环网直径规律的对比

近年内双环网络越来越广泛地被应用于局域网中.目前得到广泛的认同的是双环网络最小直径的几种求解方法,即是指对于任意给定N,而2≤S≤N-1的这样一族双环网络中找到任意节点对间的最小距离中的最大者.在可以轻松计算出双环网络直径以后,文中将给出一个新的行之有效的算法来比较有向双环网和无向双环网直径的规律.     

双环Petersen网络直径公式及最优路由算法

双环Petersen图互联网络DLCPG（k）是双环网络与Petersen图的笛卡尔积;它具有良好的可扩展性、较短的网络直径和简单的拓扑结构等特性。通过研究其拓扑结构;得到了DLCPG（k）直径的显式公式;并给出了该网络的最优单播路由算法。     

双优双环网络G(N; 1, s)的分布仿真

在直角坐标系下的一族有向双环网络 中,研究双优双环网络 的L形图形特征及其分布特性。该网络的直径、平均距离均达到最小值。计算4≤N≤1 000中任意N存在的双优双环网络个数 ,仿真4≤N≤1 000的n-N紧优分布图,发现n-N分布呈现平稳的波动特性, 不随 递增。     

无向双环网络G(N;±1,±s)的直径求解算法

提出无向双环网络G(N;±1,±s)的直径求解算法,利用VB6.0作为编程语言、SQL Server2000作为数据库来实现这一算法,对任意给定N,而2≤s≤N-1的这样一族无向双环网络的直径都可以计算出来,结果存入数据库,并且利用VB6.0的控件MSChart来模拟显示计算结果.找出了该族无向双环网络直径的分布特点:具有最大值、最小值和中间对称性;对任意N,有不少s使得G(N;±1,±s)紧优或几乎紧优.验证了Boesch和Wang等提出的无向双环网络G(N;±1,±s)的直径下界,给出了一个新的直径上界公式.     

无向双环网络G(N;±1,±s)的直径求解算法

提出无向双环网络G(N;±1,±s)的直径求解算法,利用VB6.0作为编程语言、SQLServer2000作为数据库来实现这一算法,对任意给定N,而2≤s≤N-1的这样一族无向双环网络的直径都可以计算出来,结果存入数据库,并且利用VB6.0的控件MSChart来模拟显示计算结果。找出了该族无向双环网络直径的分布特点:具有最大值、最小值和中间对称性;对任意N,有不少s使得G(N;±1,±s)紧优或几乎紧优。验证了Boesch和Wang等提出的无向双环网络G(N;±1,±s)的直径下界,给出了一个新的直径上界公式。     

双环网络存取控制的参量分析

本文通过数学分析,导出双环网络采用最快访问信道方式与最短路径方式的主要工作特性参量的计算公式,并举出典型实例,对上述两种存取控制方式作定性比较。     

无向双环网络G（N；±1，±s）的直径求解改进算法

利用计算机算法研究无向双环网络直径在国内外文献中尚不多见,文献[1]中提出了一种算法,并成功实现,其不足之处是利用数据库存取中间结果,严重影响了计算速度,当N值很大时需要计算的时间过长。针对这一不足,提出利用数组取代数据库来存取中间结果的改进算法。实验结果表明该算法较文献[1]算法极大地提高了运算速度,并列出了两个N大值直径分布图。     

Avoiding Energy Holes in Wireless Sensor Networks with Nonuniform Node Distribution

In this paper, we investigate the theoretical aspects of the nonuniform node distribution strategy used to mitigate the energy hole problem in wireless sensor networks (WSNs). We conclude that in a circular multihop sensor network (modeled as concentric coronas) with nonuniform node distribution and constant data reporting, the unbalanced energy depletion among all the nodes in the network is unavoidable. Even if the nodes in the inner coronas of the network have used up their energy simultaneously, the ones in the outermost corona may still have unused energy. This is due to the intrinsic many-to-one traffic pattern of WSNs. Nevertheless, nearly balanced energy depletion in the network is possible if the number of nodes increases in geometric progression from the outer coronas to the inner ones except the outermost one. Based on the analysis, we propose a novel nonuniform node distribution strategy to achieve nearly balanced energy depletion in the network. We regulate the number of nodes in each corona and derive the ratio between the node densities in the adjacent (i + 1)th and ith coronas by the strategy. Finally, we propose (q-switch routing, a distributed shortest path routing algorithm tailored for the proposed nonuniform node distribution strategy. Extensive simulations have been performed to validate the analysis.     

无线传感器网络中节点非均匀分布的能量空洞问题

节点非均匀分布策略能缓解无线传感器网络中的能量空洞问题.文中从理论上探讨这种策略,证明在节点非均匀分布的圆形网络中,如果节点持续向Sink节点发送数据,能量空洞现象将无法避免,而当节点数目满足一定关系时,网络中能够实现次优能耗均衡.文中提出一种节点非均匀分布策略及相应的路由算法用于实现这种次优能耗均衡.模拟结果显示网络生存周期终止时,处于网络内部的节点几乎达到了能耗均衡.     

基于差分蜂群算法的无线传感器网络节点分布优化

针对无线传感器网络节点分布优化问题,在保证节点间相互连通的情况下建立节点分布优化模型,提出了一种有效的差分蜂群优化算法,从而实现了同构无线传感器网络节点对目标区域的高效覆盖。改进算法将差分进化操作引入蜂群算法中雇佣蜂的搜索方式,以提高雇佣蜂搜索的多样性和避免计算量的浪费。差分蜂群算法在无线传感器网络节点分布优化问题上进行了测试,并与差分进化、人工蜂群两种算法进行了仿真对比。从3种算法的网络覆盖率迭代曲线可以看出,差分蜂群算法整体的探索能力及收敛速度较之其他2种算法都有所提升。除此之外,3种算法对无线传感器网络覆盖优化问题进行了100次试验,覆盖率统计结果进一步验证了所提算法的有效性。     

On the Bisection Width and Expansion of Butterfly Networks

This paper proves tight bounds on the bisection width and expansion of butterfly networks with and without wraparound. We show that the bisection width of an n -input butterfly network is without wraparound, and n with wraparound. The former result is surprising, since it contradicts the prior ``folklore' belief that the bisection width is n . We also show that every set of k nodes has at least (k/(2 log k))(1-o(1)) neighbors in a butterfly without wraparound, and at least (k/log k)(1-o(1)) neighbors in a butterfly with wraparound, if k is and o(n) , respectively. Received September 30, 1997, and in final form July 30, 2001. Online publication November 23, 2001.     

Sorting and Counting Networks of Arbitrary Width and Small Depth

We present the first construction for sorting and counting networks of arbitrary width that requires both small depth and small constant factors in the depth expression. Let w be the product w = p ₀ ⋅ p ₁ ⋅s p _n-1 , whose factors are not necessarily prime. We present a novel network construction of width w and depth O(n ² ) = O(log ² w) , using comparators (or balancers) of width less than or equal to max(p _i ) . This construction is practical in the sense that the asymptotic notation does not hide any large constants. An interesting aspect of this construction is that it establishes a family of sorting and counting networks of width w , one for each distinct factorization of w . A factorization in which max(p _i ) is large and n is small yields a network that trades small depth for large comparators (or balancers), and a factorization where max(p _i ) is small and n is large makes the opposite tradeoff. Received June 18, 2001. Online publication October 30, 2001.     

面向复杂网络的节点相似性度量

在复杂网络中,度量节点之间的相似性是一项基础且具有挑战性的工作。基于邻域节点的相似性度量仅考虑了节点的邻域信息。基于路径的相似性度量考虑了节点之间的路径信息,使得多数节点与大度节点相似。为了更准确地度量节点之间的相似性且避免多数节点与大度节点相似,定义了每个节点的距离分布,并在此基础上采用相对熵和距离分布提出了一种节点相似性度量方法(DDRE)。DDRE方法通过节点之间的最短路径生成每个节点的距离分布,根据距离分布计算节点之间的相对熵,进而得到节点之间的相似性。6个真实网络数据集的对比实验结果表明,DDRE方法在对称性以及SIR模型中影响其他节点的能力这两方面表现较好。     

Secure Node Discovery in Ad-hoc Networks and Applications

Designing secure protocols over ad-hoc networks has proved to be a very challenging task, due to various features of such networks, such as partial connectivity, node mobility, and resource constraints. Furthermore, their lack of physical infrastructures deprives their users of even basic network functions such as message routing, for which nodes are themselves responsible.In this paper we consider a very basic network function, node discovery, in ad-hoc networks, where a node with limited network information would like to establish a session with a given number of other nodes in the network (of which the node may not be aware about). We formally define correctness, security and efficiency properties of node discovery protocols, and investigate the problem of designing such protocols under appropriate network topology assumptions. Here, the security of these protocols is against Byzantine adversaries that can corrupt up to a limited number of nodes in the network and make them arbitrarily deviate from their protocol. After presenting some secure node discovery protocols, we show their application to secure service architectures in ad-hoc networks.     

Nonlinear Graph Learning-Convolutional Networks for Node Classification

Neural Processing Letters - Graph Convolutional Networks have been widely used for node classification. Since the original data usually contains nonlinear relationships that are difficult to...     

On Node Criticality in Air Transportation Networks

In this study, we analyze the criticality of nodes in air transportation using techniques from three different domains, and thus, three essentially different perspectives of criticality. First, we examine the unweighted structure of air transportation networks, using recent methods from control theory (maximum matching and minimum dominating set). Second, complex network metrics (betweenness and closeness) are used with passenger traffic as weights. Third, ticket data-level analysis (origin-destination betweenness and outbound traffic with transit threshold) is performed. Remarkably, all techniques identify a different set of critical nodes; while, in general, giving preference to the selection of high-degree nodes. Our evaluation on the international air transportation country network suggests that some countries, e.g., United States, France, and Germany, are critical from all three perspectives. Other countries, e.g., United Arab Emirates and Panama, have a very specific influence, by controlling the passenger traffic of their neighborhood countries. Furthermore, we assess the criticality of the country network using Multi-Criteria Decision Analysis (MCDA) techniques. United States, Great Britain, Germany, and United Arab Emirates are identified as non-dominated countries; Sensitivity analysis shows that United Arab Emirates is most sensitive to the preference information on the outbound traffic. Our work gears towards a better understanding of node criticality in air transportation networks. This study also stipulates future research possibilities on criticality in general transportation networks.     

无线传感器网络中移动节点定位算法研究

提出一种利用临时锚节点的蒙特卡罗箱定位算法.该算法是基于蒙特卡罗定位方法之上,通过引入节点平均速率来获取临时锚节点,并利用一跳范围内的临时锚节点构建最小锚盒、增强样本过滤条件,从而加速了采样和样本过滤.此外,在样本的获取上采用了非随机采样的均衡采样方法,有效地降低了采样次数.仿真结果表明:该算法同蒙特卡罗定位算法等相比,提高了节点的定位精度,降低了节点的能耗.