Cascading failure in Watts-Strogatz small-world networks

In this paper, we study the cascading failure in Watts-Strogatz small-world networks. We find that this network model has a heterogeneous betweenness distribution, although its degree distribution is homogeneous. Further study shows that this small-world network is robust to random attack but fragile to intentional attack, in the cascading failure scenario. With comparison to standard random graph and scale-free networks, our result indicates that the robust yet fragile property in the cascading failure scenario is mainly related to heterogeneous betweenness, rather than the network degree distribution. Thus, it suggests that we have to be very careful when we use terms such as homogeneous network and heterogeneous network, unless the distribution we refer to is specified.     

基于证据推理与最优指派策略的多属性单边匹配决策

针对匹配中某一方偏好失效的问题,提出一种基于证据推理和最优指派策略的单边匹配方法。一方主体采用多种数据类型描述由对方指定的多个属性信息;另一方给出关于各属性的权重信息;然后,使用证据推理组合规则递推合成多属性及权重信息,以此计算双方的匹配度。在此基础上,运用最优指派策略,建立匹配模型并求解得到匹配结果.实例表明该方法的可行性和有效性。     

材料的动态损伤和失效

本文对动载荷下材料内部损伤演化过程的研究进行了较为全面、系统的介绍和总结,并对现有的各种动态损伤模型(包括笔者所提出的模型)进行了必要的比较、讨论和评述。     

冲击速度和轴向静载对红砂岩破碎及能耗的影响

地下岩体工程爆破开挖中,距爆源不同距离处岩体承受的地应力和动载荷大小不同,从动载荷的角度表征岩石动态破坏结果与工程实际更吻合。为研究动载荷和地应力大小对岩体破碎和能量耗散特性的影响,利用动静组合加载试验装置,分别设置7个冲击速度和轴向静应力等级,对红砂岩试件进行冲击试验。根据试件的破碎状况,分析不同静应力工况下冲击速度对岩石破坏模式和机理的影响。计算不同工况下的应力波能量值,研究冲击速度和轴向静应力对岩石能耗特性的影响。对破坏试件进行筛分试验,研究岩石破碎分形维数随冲击速度和轴向静应力的变化关系。结果表明,随着冲击速度的增大,试件的破坏程度逐渐加大。无轴压时岩石试件破坏后整体仍是一个圆柱体,属于张拉破坏;有轴压时岩石试件宏观破坏后呈沙漏状,属于拉剪破坏。岩石耗散能随冲击速度的升高呈二次函数关系递增;轴向静应力越高,递增幅度越小。随着冲击速度的升高,岩石分形维数由零逐渐增加;随着轴向静应力的升高,分形维数由零转为大于零的临界冲击速度先升高后降低。

     

Calibrating software reliability models when the test environment does not match the user environment

Software failures have become the major factor that brings the system down or causes a degradation in the quality of service. For many applications, estimating the software failure rate from a user's perspective helps the development team evaluate the reliability of the software and determine the release time properly. Traditionally, software reliability growth models are applied to system test data with the hope of estimating the software failure rate in the field. Given the aggressive nature by which the software is exercised during system test, as well as unavoidable differences between the test environment and the field environment, the resulting estimate of the failure rate will not typically reflect the user‐perceived failure rate in the field. The goal of this work is to quantify the mismatch between the system test environment and the field environment. A calibration factor is proposed to map the failure rate estimated from the system test data to the failure rate that will be observed in the field. Non‐homogeneous Poisson process models are utilized to estimate the software failure rate in both the system test phase and the field. For projects that have only system test data, use of the calibration factor provides an estimate of the field failure rate that would otherwise be unavailable. For projects that have both system test data and previous field data, the calibration factor can be explicitly evaluated and used to estimate the field failure rate of future releases as their system test data becomes available. Copyright © 2002 John Wiley & Sons, Ltd.     

水下爆炸冲击荷载下混凝土重力坝的抗爆性能

在水下爆炸冲击荷载作用下,结构动力响应较之静态荷载和地震荷载作用下要复杂得多。通过大 量的数值模拟,探讨了混凝土重力坝在水下爆炸冲击荷载作用下,大坝高度、库前水位对大坝抗爆性能的影 响,为大坝抗爆性能评估和防护设计提供基础。数值计算中,构建了重力坝水下爆炸全耦合数值模型,并考虑 爆炸冲击作用下混凝土的高应变率效应。研究结果表明:对于混凝土重力坝,随着大坝高度的增加,大坝的抗 爆性能增强;库前水位对大坝的抗爆性能影响较大,通过降低库前水位可有效提高大坝的抗爆性能。     

无失效数据的Bayes和多层Bayes分析

本文推广了文献[6]的结果，对指数分布无失效数据的失效率，给出了Bayes估计、Bayes置信上限以及多层Bayes估计，从而可以得到无失效数据可靠度的估计，最后，结合实际问题进行了计算。     

慢性肾衰肾虚证患者血清微量元素的变化及其临床意义探讨

讨论了慢性肾衰肾阳虚和肾阴虚见证者血清微量元素。结果显示：肾阳虚患者血清Ｃｕ、Ｃｕ／Ｚｎ明显高于健康对照组,而血清Ｚｎ和Ｆｅ低于对照组,肾阳虚患者血清Ｃｕ、Ｃｕ／Ｚｎ也明显高于肾阴虚组,而血清Ｚｎ是低的,在肾阴虚组与对照组之间Ｃｕ、Ｚｎ、Ｃｕ／Ｚｎ均无明显差异。     

平面坡体渐进破坏模型及其应用

平面坡体渐进破坏模型旨在通过在坡体稳定性分析中引进渐进坡坏的概念,来较合理地考虑岩土材料的峰值强度和残余强度在稳定性分析中的不同作用。通过与其它稳定性分析方法进行比较以及实例应用研究,证明该计算模型可用于初步判断坡体稳定状态并估算其破坏变形范围。这一研究也说明了水对边坡破坏的重要作用。     

Semi-Markov failure rates processes

Usually, a reliability function is defined by a failure rate which is a real function taking the non-negative real values. In this paper the failure rate is assumed to be a stochastic process with non-negative and right continuous trajectories. The reliability function is defined as an expectation of a function of that random process. Particularly, the failure rate defined by the semi-Markov processes is considered here. The theorems dealing with the renewal equations for the conditional reliability functions with a semi-Markov process as a failure rate are presented in this paper. A system of that kind of equations for the discrete state space semi-Markov process is applied for calculating the reliability function for the 3-states semi-Markov random walk. Using the introduced system of renewal equations for the countable state space, the reliability function for the Furry-Yule failure rate process is obtained.