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22.
Wide Diameters of Cartesian Product Graphs and Digraphs 总被引:1,自引:1,他引:1
Jun-Ming Xu 《Journal of Combinatorial Optimization》2004,8(2):171-181
In graph theory and study of fault tolerance and transmission delay of networks, connectivity and diameter of a graph are two very important parameters and have been deeply studied by many authors. Wide diameter combining connectivity with diameter is a more important parameter to measure fault tolerance and efficiency of parallel processing computer networks and has received much attention in the recent years. Diameter with width k of a graph G is defined as the minimum integer d for which between any two distinct vertices in G there exist at least k internally disjoint paths of length at most d. In the present paper, the tight upper bounds of wide diameter of the Cartesian product graphs are obtained. Some known results can be deduced or improved from ours. 相似文献
23.
Probabilistic risk assessment (PRA) is a useful tool to assess complex interconnected systems. This article leverages the capabilities of PRA tools developed for industrial and nuclear risk analysis in community resilience evaluations by modeling the food security of a community in terms of its built environment as an integrated system. To this end, we model the performance of Gilroy, CA, a moderate‐size town, with regard to disruptions in its food supply caused by a severe earthquake. The food retailers of Gilroy, along with the electrical power network, water network elements, and bridges are considered as components of a system. Fault and event trees are constructed to model the requirements for continuous food supply to community residents and are analyzed efficiently using binary decision diagrams (BDDs). The study also identifies shortcomings in approximate classical system analysis methods in assessing community resilience. Importance factors are utilized to rank the importance of various factors to the overall risk of food insecurity. Finally, the study considers the impact of various sources of uncertainties in the hazard modeling and performance of infrastructure on food security measures. The methodology can be applicable for any existing critical infrastructure system and has potential extensions to other hazards. 相似文献
24.
《Risk analysis》2018,38(8):1576-1584
Fault trees are used in reliability modeling to create logical models of fault combinations that can lead to undesirable events. The output of a fault tree analysis (the top event probability) is expressed in terms of the failure probabilities of basic events that are input to the model. Typically, the basic event probabilities are not known exactly, but are modeled as probability distributions: therefore, the top event probability is also represented as an uncertainty distribution. Monte Carlo methods are generally used for evaluating the uncertainty distribution, but such calculations are computationally intensive and do not readily reveal the dominant contributors to the uncertainty. In this article, a closed‐form approximation for the fault tree top event uncertainty distribution is developed, which is applicable when the uncertainties in the basic events of the model are lognormally distributed. The results of the approximate method are compared with results from two sampling‐based methods: namely, the Monte Carlo method and the Wilks method based on order statistics. It is shown that the closed‐form expression can provide a reasonable approximation to results obtained by Monte Carlo sampling, without incurring the computational expense. The Wilks method is found to be a useful means of providing an upper bound for the percentiles of the uncertainty distribution while being computationally inexpensive compared with full Monte Carlo sampling. The lognormal approximation method and Wilks’s method appear attractive, practical alternatives for the evaluation of uncertainty in the output of fault trees and similar multilinear models. 相似文献
25.
《Risk analysis》2018,38(8):1634-1655
The work in the article presents the development of an application guide based on feedback and comments stemming from various railway actors on their practices of SIL allocation to railway safety‐related functions. The initial generic methodology for SIL allocation has been updated to be applied to railway rolling stock safety‐related functions in order to solve the SIL concept application issues. Various actors dealing with railway SIL allocation problems are the intended target of the methodology; its principles will be summarized in this article with a focus on modifications and precisions made in order to establish a practical guide for railway safety authorities. The methodology is based on the flowchart formalism used in CSM (common safety method) European regulation. It starts with the use of quantitative safety requirements, particularly tolerable hazard rates (THR). THR apportioning rules are applied. On the one hand, the rules are related to classical logical combinations of safety‐related functions preventing hazard occurrence. On the other hand, to take into account technical conditions (last safety weak link, functional dependencies, technological complexity, etc.), specific rules implicitly used in existing practices are defined for readjusting some THR values. SIL allocation process based on apportioned and validated THR values is finally illustrated through the example of “emergency brake” subsystems. Some specific SIL allocation rules are also defined and illustrated. 相似文献
26.
本文针对污水处理项目运营风险高、企业偷排行为控制难问题,首先依据排污信息和排污价格的波动与否,构建了4种计算实验情景;然后针对各种情景分别设计了污水处理价格形成机制、居民和企业社会属性与行为的变化规则,分析了经济压力、社会影响以及政府监管对排污价格形成、排污者行为变化的影响;最后运用计算实验方法模拟了污水处理项目运营与排污者行为在4种情景下的动态变化。结果表明:合理的静态定价策略要优于运营商动态定价策略;动态外部环境既给污水处理项目的运营带来风险,又给政府对企业的监管带来不便;单纯的市场价格机制或政府监管机制很难有效控制偷排现象,也不一定能实现居民的节水减排,企业和运营商的逐利行为可能会使得目标落空。 相似文献
27.
《Journal of Statistical Computation and Simulation》2012,82(3):628-643
This article deals with the construction of an X? control chart using the Bayesian perspective. We obtain new control limits for the X? chart for exponentially distributed data-generating processes through the sequential use of Bayes’ theorem and credible intervals. Construction of the control chart is illustrated using a simulated data example. The performance of the proposed, standard, tolerance interval, exponential cumulative sum (CUSUM) and exponential exponentially weighted moving average (EWMA) control limits are examined and compared via a Monte Carlo simulation study. The proposed Bayesian control limits are found to perform better than standard, tolerance interval, exponential EWMA and exponential CUSUM control limits for exponentially distributed processes. 相似文献
28.
以有杆抽油系统动力学行为分析为基础,将基础理论研究和应用技术有机地结合起来,建立了考虑悬挂系统弹性的直井和定向井有杆抽油系统诊断模型,研究了基于B/S(Brower/Server)模式的有杆抽油系统故障诊断方法,利用Internet技术和Web技术开发了相应的软件系统, 通过浏览器即可实现对有杆抽油系统快速、准确的故障诊断,并给出了诊断算例,诊断结果验证了该系统的有效性。基于B/S模式的有杆抽油系统故障诊断对避免井下作业的盲目性,提高系统效率,降低采油成本,实现油田企业信息化和提高油井的科学管理水平具有重要意义。 相似文献
29.
温建辉 《聊城大学学报(社会科学版)》2011,(3):93-98
从古到今,司法证明方法变动不居。而证据是司法证明方法历史兴替的标志,证明方法的各种属性是司法证明方法历史兴替的根据。发源析流,知古鉴今,人类社会的司法证明方法已然经历过两次重大的转变,当代基于各种现代技术手段和仪器测试而取得的各种各样的心理证据的出现预示着司法证明方法第三次转变的发展方向。而一些国家对证明犯罪人主观心理方法合法性的立法认可显露了司法证明方法第三次转变的冰山一角。 相似文献
30.
刘雪丽 《河南工程学院学报(社会科学版)》2011,26(2):56-58
行政赔偿问题一直是社会关注的热点,它直接关系到行政机关的信誉和公民的切身利益。修改前的《国家赔偿法》规定行政赔偿采用违法归责原则,但是违法归责原则的不足影响了公平正义的实现。修改后的《国家赔偿法》虽然在总则中取消了违法性的要求,但仍存在不足之处。行政赔偿制度可以借鉴民事赔偿的归责原则,以过错原则作为违法归责原则的补充,从而更好地保障公民的合法权益,救济损害,维护社会正义。 相似文献