The Wartime Bridge Reliability Evaluation Model Based on Birth-and-Death Process

At first, the concept of bridge reliability is given, followed with its mathematic model. Then, based on the analysis about the mechanism of the damage and repair of bridges, and the state diversion of bridge network, the state diversion process is proved to be birth-and-death process. In the end, the state diversion balance equation of bridge network is built, and the evaluation model of wartime bridge reliability is got. The model is used in a certain example, and it is proved to be precise and credible.

Reliability evaluation of PMS considering coupling effect of functional and physical dependency

Aviation and aerospace system are typical Phased-Mission Systems(PMSs)featured with varying configuration,phased load condition and cross phase failure correlation.The coupling effect of Functional Dependency(FDEP)and Physical Dependency(PDEP)has a unique influence on the failure behavior of PMS.In this article,the coupling effect is analyzed,and the degradation of components is modeled with the positive drift wiener process,in which the drift coefficient is related to environmental conditions and operation stress.Finally,failure behavior and system reliability are simulated.An avionics controller is studied as a case,with the degradation time distribution model and simulation algorithm,the coupling effect and dynamical system reliability can be achieved.Results show that this modeling method can describe the coupling effects of FDEP and PDEP and their influence on the failure behavior and reliability of the PMS system.

Reliability Evaluation of Two-Phase Degradation Process with a Fuzzy Change-Point

For some products,degradation mechanisms change during testing,and therefore,their degradation patterns vary at different points in time;these points are called change-points.Owing to the limitation of measurement costs,time intervals for degradation measurements are usually very long,and thus,the value of change-points cannot be determined.Conventionally,a certain degradation measurement is selected as the change-point in a two-phase degradation process.According to the tendency of the two-phase degradation process,the change-point is probably located in the interval between two neighboring degradation measurements,and it is a fuzzy variable.The imprecision of the change-point may lead to the incorrect product’s reliability evaluation results.In this paper,based on the fuzzy theory,a two-phase degradation model with a fuzzy change-point and a statistical analysis method are proposed.First,a two-phase Wiener degradation model is developed according to the membership function of the change-point.Second,the reliability evaluation is carried out using maximum likelihood estimation and a fuzzy simulation approach.Finally,the proposed methodology is verified via a case study.The results of the study show that the proposed methodology can achieve more believable reliability evaluation results compared with those of the conventional approach.

Reliability Comparison Between Parallel and Cold-standby Two-unit System Under Poisson Shock

This paper investigates the comparison problem of the reliability index between a parallel and a cold-standby system,both of which are consisting of two identical units.On the contrary to the general intuitive result,we proved that,under the condition that the system is shocked by a Poisson stream,the life time of the parallel system is longer than that of the cold-standby one in the sense of probability.

Reliability of a Large Series-parallel System in Variable Operating Conditions

In this paper, a semi-Markov model of system operation processes is proposed and its selected parameters are determined. A series-parallel multi-state system is considered, and its reliability and risk characteristics found. Subsequently, a joint model of system operation process and system multi-state reliability and risk is constructed. Moreover, the asymptotic approach to reliability and risk evaluation of a multi-state series-parallel system in its operation process is applied to a port grain transportation system.

Reliability Measure of a Relay Parallel System under Dependence Conditions

In a relay system of dependent components, the failure to close reliability measure is given as a Girsanov transform of the failure to open reliability measure.

A GMRP Approach for Reliability Analysis of Repairable Systems

We propose here a mathematical approach for the study of repairable systems with arbitrary distributions. The idea is to define a new type of stochastic process, called a generalized Markov renewal process (GMRP). which may describe the transition behavior of the stochastic process at non-regenerative points. In the paper an analytical method for the GMRP is put forward and the formulas are then presented for reliability analysis of repairable systems which can be described by a GMRP with finite states. A signal flow graph technique for system modeling is also summarized here. Finally- an analytical model to evaluate the reliability of a m-out-of- n.G system with general repair-time distribution is developed by means of the GMRP approach.

Reliability modelling based on dependent two-stage virtual age processes

This paper proposes reliability and maintenance models for systems suffering random shocks arriving according to a non-homogeneous Poisson process.The system degradation process include two stages:from the installation of a new system to an initial point of a defect(normal stage),and then from that point to failure(defective stage),following the delay time concept.By employing the virtual age method,the impact of external shocks on the system degradation process is characterized by random virtual age increment in the two stages,resulting in the corresponding two-stage virtual age process.When operating in the defective state,the system becomes more susceptible to fatigue and suffers from a greater aging rate.Replacement is carried out either on failure or on the detection of a defective state at periodic or opportunistic inspections.This paper evaluates system reliability performance and investigates the optimal opportunistic maintenance policy.A case study on a cooling system is given to verify the obtained results.

考虑极端天气冲击过程的风电机组竞争失效可靠性评估

针对风电机组的运行可靠性易受极端天气影响的问题,提出了一种考虑极端天气冲击过程的风电机组竞争失效可靠性评估方法。同时考虑风电机组自然退化、极端天气冲击导致的瞬时退化以及极端天气持续过程产生的加速退化,构建极端天气下的风电机组综合退化模型;考虑风电机组退化过程对其耐冲击性能的影响,建立风电机组竞争失效可靠度模型以评估风电机组可靠性;基于我国北方某风电场工程数据和极端天气历史数据评估了某2 MW风电机组的可靠性并进行了参数灵敏度分析。结果显示,到第5年时,仅考虑自然退化的方法评估风电机组可靠度为0.84,而考虑极端天气冲击过程的方法评估风电机组可靠度为0.178,后者更加符合工程实际。通过模型参数的灵敏度分析发现,运行时间超过3年后,退化失效开始逐渐影响风电机组的可靠性。

基于组合赋权-偏序集的应急供应链可靠性评价

为协调好应急供应链中物资的分配与使用,基于文献分析等方法提炼应急供应链可靠性评价指标,建立由组织保障可靠性、系统制度可靠性以及运作流程可靠性3个一级指标及其对应的17个二级指标组成的应急供应链可靠性评价指标体系;利用层次分析法(AHP)、熵权法(EWM)和三角模糊数计算指标权重,将蕴含权重信息的偏序关系引入评价研究中,构建组合赋权-偏序集模型评价应急供应链的可靠性,并应用该模型评价分析C市5个县级城市的应急供应链可靠性水平。结果表明:5个县级城市的应急供应链可靠性程度可分为4类,其中,地区03的可靠性水平高,地区04、02的可靠性水平较高,地区05的可靠性水平中等,而地区01的可靠性水平低;通过对比分析,获取各地区的优势环节和薄弱环节以及需改进的地方。该评价模型可有效评估应急供应链可靠性水平。

退化系统任务中止策略研究综述

对退化系统的任务中止策略展开研究。首先,将退化系统分为普通退化系统和随机过程退化系统,从多部件、多阶段、多状态等角度对普通退化系统提出的中止策略进行论述,从Wiener、Gamma等过程具有的不同性质对随机过程退化系统提出的中止策略进行论述;然后,通过讨论退化系统任务中止策略模型的实际应用可知,无人机(unmanned aerial vehicle,UAV)是目前被应用最多的领域;最后,采用CiteSpace软件对这一领域的研究热点、趋势、前沿进行分析,结果表明,基于随机过程建立退化模型,并在制定任务中止策略的同时考虑预防维护、最优检测、任务冗余以及完美或不完美维修的联合优化模型虽然难度很大,但却具有相当大的发展空间。

基于时变Copula函数的多部件系统可靠性评估

针对多部件失效相关的机械系统,提出一种基于时变Copula函数的多部件系统可靠性评估方法。首先,引入非线性Wiener过程刻画性能退化过程,并采用Copula函数刻画多部件失效间的相关性;其次,基于傅里叶级数近似Copula函数的演化方程,并通过蒙特卡洛(MC)模拟验证傅里叶级数对常见时变形式的拟合效果;此外,采用似然比统计量检验时变相关性的存在性,指明时变相关性研究的必要性。算例分析结果表明,与静态相关性模型相比,时变相关性模型对数似然函数值提高4.36%、赤池信息量准则(AIC)减小3.81%,可靠性评估结果更加准确。

基于统计过程控制的硅转接板良率优化系统设计

针对2.5D封装用硅通孔(through silicon via,TSV)硅转接基板批量化生产过程中缺乏可靠性评价与优化技术的问题,提出基于统计过程控制(statistical process control,SPC)的评估控制系统,实现在线工艺状态监控及评价,设计硅转接板测试用工艺控制检测(process control monitor,PCM)结构,阐述自动光学检测(automated optical inspection,AOI)中常见的缺陷对系统可靠性的影响。提出的SPC系统对硅转接板批量化生产良率提升具有重要意义。

基于AHP和HoR的船用动力装置可靠性重要度评价方法

针对船用动力装置组成复杂、可靠性影响因素多、分析难度大的问题,提出一种考虑故障相关性的动力装置可靠性重要度评价方法。采用可靠性屋分析(house of reliability,HoR)方法对动力装置危害性进行分析,得到考虑故障相关性的动力装置各单元故障危害度。综合考虑多种因素对动力装置可靠性的影响程度,将HoR分析结果运用到层次分析法(analytic hierarchy process,AHP)中,对影响动力装置的各单元进行可靠性重要度评价。结果显示柴油机和高弹性联轴器具有较高的重要度,该评价结果可用于指导动力装置的故障预防和维修保养方案制定等。

一种基于连续时间马尔科夫随机过程的多态退化可靠性模型及应用

传统二态可靠性评价方法难以反映复杂系统性能退化过程的多态变化特征,为动态评价机械系统性能退化过程中的可靠性特征,提出了基于多态退化模型的系统可靠性动态评价方法。运用连续时间Markov随机过程理论,并基于最小化维修策略,构建了系统性能多态退化随机过程模型。运用拉普拉斯变换对模型求解,得到了系统性能退化过程中各状态的时间相关概率通用表达式,并推导了系统的时间相关可靠性特征参数,从而获取了系统性能多态退化过程的可靠性动态变化特征。以某汽车副车架的疲劳性能退化过程为研究对象,建立了其疲劳性能多态退化可靠性评价模型。以实测疲劳试验数据为驱动,多项可靠性指标的模型计算结果与实际试验结果十分接近,误差低于3%,验证了所建模型的有效性,实现了对该型副车架疲劳性能衰退过程的有效模拟与动态评价。所提出的多态退化模型可为复杂机械系统性能退化过程的可靠性评价与研究提供参考。

基于Markov过程的继电保护通信系统可靠性评估方法

继电保护通信系统受内外部因素影响,易出现拒动失效。传统评估方法未充分考虑动态行为、故障传播及复杂环境,导致评估结果中拒动失效率偏高。因此,文章提出基于Markov过程的继电保护通信系统可靠性评估方法。通过选取合适的可靠性评估指标全面反映系统的性能特点,利用Markov过程构建状态随机转移概率矩阵,描述系统在不同状态下的转移概率,综合评估继电保护通信系统的可靠性。实验结果表明,该方法综合考虑多种因素,拒动失效率较低,为电力系统的安全稳定运行提供有力支持。

基于Beowulf集群的大电力系统可靠性评估蒙特卡罗并行仿真

研究了大电力系统可靠性评估并行仿真问题:分别采用状态采样法和系统状态转移采样法进行Monte-Carlo并行仿真。建立了与收敛判据相结合的任务分配拓扑结构,并根据2种采样方法的不同需要采用了不同的伪随机数生成方式,详细地分析了配合收敛控制的异步模拟过程,最后基于构建的Beowulf集群环境进行测试系统的可靠性评估计算。2种Monte-Carlo并行仿真方法均得到较高的加速比和并行效率,其可靠性指标的计算结果亦与串行环境下得到的结果基本保持一致。该文所做工作是对国外若干电力系统可靠性评估并行仿真研究的深入和发展。

大电力系统可靠性评估高性能计算平台设计与实现

针对大电力系统可靠性计算的高度复杂性,基于高性能集群环境,建立了粗粒度Monte Carlo并行计算模型,提出了消息传递机制下配合收敛控制的异步化并行算法,以较高的加速比和并行效率,快速实现大电力系统可靠性评估计算。同时,以大电力系统可靠性评估高性能计算为核心,利用LAMP(Linux+Apache+MySQL+PHP)网络开发工具,建立基于浏览器/服务器(B/S)3层模型的Web计算系统基本结构,提出对应的网络数据库设计和并行计算模块装载模型,以Web Service的形式实现大电力系统可靠性评估高性能计算的Internet共享。

电力系统可靠性评估的动态任务分配并行算法

针对大电力系统可靠性评估并行计算中静态任务分配方法存在的进程间通信次数多、过度计算等不足,在详细分析Monte-Carlo仿真过程中可靠性指标方差系数和抽样次数变化规律的基础上,提出基于De Moivre-Laplace中心极限定理和曲线拟合相结合的启发式动态任务分配方法,并提出基于动态任务分配的大规模电力系统可靠性评估并行算法。在并行任务分配过程中,根据已有的仿真信息对总抽样次数进行合理估计,使得单次任务分配量尽可能多,以达到减少进程间通信次数的目的。算例分析表明所述的动态任务分配方法可较好地提高并行效率。

基于改进层次分析法的交、直流微电网综合评估

根据交、直流微电网的特点,基于供电可靠性、技术经济性以及适应性3个准则,建立了交、直流微电网综合评估指标体系,并提出各个评价指标的计算模型和量化方法。同时采用5/5-9/1标度层次分析法确定各评价指标的权重,使得确定后的权重更加合理且具有更好的一致性。对交、直流微电网的算例评估结果验证了所提指标体系的合理性以及评估方法的有效性。