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本文主要对随机流网络的d-下界点进行了研究。首先,根据随机流网络的最大流,对容量向量进行了分类,并讨论了不同类之间的关系,给出了d-下界点与d-上界点的另一种定义方式。其次,改进了容量向量中寻找极小元(极大元)的算法,也是求d-下(上)界点的方法。 相似文献
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通信网络的可靠性评估 总被引:13,自引:1,他引:12
通信网络的可靠性评估是一个难题。目前人们只对环型网和树型网进行可靠性分析。本文首先定义了通信网络的可靠性,依据图论提出了网络生成树的计算方法,以及网络可靠度的估算公式。最后给出了一个栅格型网的可靠度估算示例。 相似文献
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工业以太网冗余技术分析 总被引:3,自引:0,他引:3
为了满足工业以太网对网络的可靠性要求,减少因网络故障造成的损失,网络冗余容错技术的提出增加了网络的可靠性和稳定性。文中介绍了网络冗余技术国内外研究的总体情况,讨论了多种网络冗余解决方案,包括生成树协议、快速生成树协议、环网冗余协议和分布式冗余网络协议,以及其他的网络冗余技术,着重讨论了分布式冗余网络协议,’最后对多种网络冗余解决方案进行了比较,特别指出了它们的局限性。 相似文献
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周继鹏 《微电子学与计算机》1993,10(11):7-10
语法分析器应用文法规则生成语法树来表示一名句子的语法结构。本文讨论用概念图表示自然语言的语义,描述一个从语法树开始生成概念图来解释句子语义的方法,生成过程是由语法树引导,把与每一个输入词相关的概念图连接成一个较大的概念图表示整修句子的语义。 相似文献
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计算无圈有向网络ST可靠性的一个新方法 总被引:4,自引:1,他引:3
本文考虑计算无圈有向网络的ST可靠性问题(至少存在一条从源点s到汇点t的正常运行道路的概率)。文章引进了深度优先搜索(Depth-FirstSearch)有序根树的概念并提出一个新的计算无圈有向网络ST可靠性的拓扑公式。以该公式为基础,我们利用DFS方法提出一个新的计算无圈有向网络ST可靠性算法,它能生成简洁的可靠性表达式,进而有效地计算无圈有向网络的ST可靠性。两个例子例证了我们的结论 相似文献
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讨论了目前可靠性评估的常用方法和相应的测度指标,指出了当前可靠性评估技术的缺点和不足。针对以添加链路的形式扩展通信网络的过程,提出了一种基于生成树的通信网络扩展的优化方法,并且利用这种方法进行了某种网络拓扑结构扩展的仿真计算,与现存的其它方法的比较表明,这种基于生成树的优化方法设计合理、计算快速,可以有效地应用于实际的通信网络扩展的优化过程中。 相似文献
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有线电视用户分配网络由放大器、电缆、分支器和分配器等组成。分配网络的作用是给每个用户终端提供一个适当的信号电平。通常的设计是在放大器输出端设置一个或两个分配器,将放大器的输出分为若干路,每一路就是一条分支电缆,每条分支电缆上串接若干分支器或串接单元,将信号送到每一个用户终端。 相似文献
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本文提出了求通信网络总可靠度的状态空间树法。它直接产生网络图的一个不交化树多层多项式,优点是计算量较小[计算时间复杂度为0(?),(?)为边数,n_1为叶数],所得表达式较短。在此基础上应用超图理论提出了求通信网络总可靠度的精确分解算法。用它进行网络图的m次分解,一台计算机所能计算的通信网络规模可以扩大m倍。 相似文献
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Reliability of a stochastic-flow network with unreliable branches & nodes, under budget constraints 总被引:2,自引:0,他引:2
Yi-Kuei Lin 《Reliability, IEEE Transactions on》2004,53(3):381-387
System reliability evaluation for flow networks is an important issue in quality management. This paper concentrates on a stochastic-flow network in which nodes as well as branches have several possible capacities, and can fail. The possibility is evaluated that a given amount of messages can be transmitted through the stochastic-flow network under the budget constraint. Such a possibility, system reliability, is a performance index for a stochastic-flow network. A minimal path, an order sequence of nodes & branches from the source to the sink without cycles, is used to assign the flow to each component (branch or node). A lower boundary point for (d, C) is a minimal capacity vector, which enables the system to transmit d messages under the budget C. Based on minimal paths, an efficient algorithm is proposed to generate all lower boundary points for (d, C). The system reliability can then be calculated in terms of all lower boundary points for (d, C) by applying the inclusion-exclusion rule. Simulation shows that the implicit enumeration (step 1) of the proposed algorithm can be executed efficiently. 相似文献
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Improvement of the reliability of a communication network is an optimal problem that finds some links to add to the network such that the reliability of the network reaches a given level and the total cost of these links is minimized. A decomposition method based on branch and bound is used for solving the problem. In order to speed up the solution procedure, an upper bound on system reliability in terms of node degrees is applied. Specially, when the threshold Po is large enough, a new algorithm, the cut tree algorithm, can more effectively give the optimal solution. 相似文献
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In a probabilistic network, source-to-multiple-terminal reliability (SMT reliability) is the probability that a specified vertex can reach every other vertex. This paper derives a new topological formula for the SMT reliability of probabilistic networks. The formula generates only non-cancelling terms. The non-cancelling terms in the reliability expression correspond one-to-one with the acyclic t-subgraphs of the network. An acyclic t-subgraph is an acyclic graph in which every link is in at least one spanning rooted tree of the graph. The sign to be associated with each term is easily computed by counting the vertices and links in the corresponding subgraph. Overall reliability is the probability that every vertex can reach every other vertex in the network. For an undirected network, it is shown the SMT reliability is equal to the overall reliability. The formula is general and applies to networks containing directed or undirected links. Furthermore link failures in the network can be s-dependent. An algorithm is presented for generating all acyclic t-subgraphs and computing the reliability of the network. The reliability expression is obtained in symbolic factored form. 相似文献
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This paper considers optimization of two networks with a reliability constraint. The objective is to find some links to connect two networks, at a minimal cost, under the constraint that the system reliability of the resultant network is not less than a given level. A decomposition method based on branch and bound is used for solving the problem. In order to speed up the solution procedure, an upper bound on system reliability in terms of node degrees is applied. In particular, when the threshold Po is large enough, a new algorithm, the cut tree algorithm, can more effectively give an optimal solution. 相似文献
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A Simple Technique for Computing Network Reliability 总被引:1,自引:0,他引:1
A tree construction technique to compute a reliability expression of a network is derived. The technique is straight forward and good for both directed and undirected graphs. It gives mutually disjoint success branches. The reliability expression of each branch can be directly written by a set of rules. The reliability of the network can then be obtained by taking the direct sum of the reliabilities of the branches. It involves fewer multiplications than other known techniques. For a moderately complex network it is very easy to use this technique for evaluating reliability. 相似文献
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The terminal-pair reliabilities, between the root and a leaf, of the two-center binary tree, the X-tree, and the ring-tree are computed; the beheaded binary tree is used as a benchmark. A building block is identified in the two-center binary tree from which a decomposition method is formulated. Another building block is identified for the X-tree and ring-tree from which a truss-transformation method is obtained. Computation has been carried out using algorithms based on the analysis. Although the ring-tree is the most reliable at all practical ranges of link and mode reliabilities, the X-tree and two-center binary tree are also good candidates because link reliability over 0.95 is quite common, and node reliability can be kept very high. The X-tree in particular is quite desirable due to its lower connectivity at each node and hence a lower implementation complexity. Three computational methods are presented. The simplicity of the two-center binary-tree algorithm blends with the hierarchical structure of the network itself because the states directly show that the level of computation can be summarized by some reliability subcomponents 相似文献
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Network reliability is extensively used to measure the degree of stability of the quality of infrastructure services. The performance of an infrastructure network and its components degrades over time in real situations. Multi-state reliability modeling that allows a finite number of different states for the performance of the network and its components is more appropriate for the reliability assessment, and provides a more realistic view of the network performance than the traditional binary reliability modeling. Due to the computational complexity of the enumerative methods in evaluating the multi-state reliability, the problem can be reduced to searching lower boundary points, and using them to evaluate reliability. Lower boundary points can be used to compute the exact reliability value and reliability bounds. We present an algorithm to search for lower boundary points. The proposed algorithm has considerable improvement in terms of computational efficiency by significantly reducing the number of iterations to obtain lower reliability bounds. 相似文献
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黄汝激 《电子科学学刊(英文版)》1990,7(4):296-305
First,the state space tree method for finding communication network overall re-liability is presented.It directly generates one disjoint tree multilevel polynomial of a networkgraph.Its advantages are smaller computational effort(its computing time complexity is O(en_l),where e is the number of edges and n_l is the number of leaves)and shorter resulting expression.Second,based on it an exact decomposition algorithm for finding communication network overallreliability is presented by applying the hypergraph theory.If we use it to carry out the m-timedecomposition of a network graph,the communication network scale which can be analyzed by acomputer can be extended to m-fold. 相似文献
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本文提出一种树型电力网单一故障分支的识别方法零泛器替代法。这种方法的特点是诊断所需要的端口变量易于测量,对于短路和断线故障都适用,测后计算量较少。适用于多分支的树型电力网单一故障分支的识别。经计算机模拟,证明了所提识别方法是有效的。 相似文献