离散时间单重休假冷储备系统的可靠性分析

利用离散向量Markov过程方法研究了离散时间单重休假两同型部件冷储备可修系统。在部件寿命服从几何分布,修理时间和修理工休假时间服从一般离散型概率分布的假定下,引入修理时间和休假时间尾概率,求得了系统的稳态可用度、稳态故障频度、待修概率、修理工空闲概率和休假概率,以及首次故障前平均时间等可靠性指标。     

具有单重休假和修复不如新的两部件温贮备系统

研究了修理工单重休假且由两个不同型部件和一个修理工组成的可修型温贮备系统. 系统考虑了在工作故障和贮备 故障都不能 “修复如新”, 部件 1 是修复非新而部件 2 修复如新的条件下, 假设部件的工作寿命、贮备寿命、故障后的修理时间和贮备故障后的修理时间均服 从不同的指数分布, 修理工休假服从一般连续型分布. 运用几何过程理论、补充变量法、 拉普拉斯变换及拉普拉斯--司梯阶变换, 得到了系统的可用度、可靠度和系统首次故障前平均时间等可靠性指标. 最后, 通过数值模拟验证了结果的有效性.     

带启动时间和可修服务台的M/M/1/N工作休假排队系统

分析带有启动时间、服务台可故障的M/M/1/N单重工作休假排队系统.在该系统中,服务台在休假期间不是完全停止工作,而是处于低速服务状态.假定服务台允许出现故障且当出现故障时,服务台停止为顾客服务且立即进行修理.服务台的失效时间和修理时间均服从指数分布,且工作休假期和正规忙期具有不同的取值;同时,从关闭期到正规忙期有服从指数分布的启动时间.建立此工作休假排队系统的有限状态拟生灭过程(QBD),使用矩阵几何方法得到QBD的各稳态概率相互依赖的率阵,从而求得稳态概率向量.通过有限状态QBD的最小生成元和稳态概率向量得到系统的基本阵和协方差矩阵,求解出系统方差、系统稳态可用度、系统吞吐率、系统稳态队长、系统稳态故障频度等系统性能.数值分析体现了所提出方法的有效性和实用性,通过敏感性分析将各参数对系统性能的影响进行了初探,为此模型的实际应用提供了很好的理论依据.     

带工作休假和工作故障的M/M/1/N排队系统性能分析

本文在可修M/M/1/N排队系统中引入了启动时间、工作休假和工作故障策略.在该系统中,服务台在休假期间不是完全停止工作,而是处于低速服务状态.设定服务台在任何时候均可发生故障,当故障发生时立刻进行维修.且当服务台在正规忙期出现故障时,服务台仍以较低的服务速率为顾客服务.服务台的寿命时间和修理时间均服从指数分布,且在不同的时期有不同的取值.同时,从关闭期到正规忙期有服从指数分布的启动时间.本文建立此模型的有限状态拟生灭过程(QBD),使用矩阵几何方法得到系统的稳态概率向量,并应用基本阵和协方差矩阵理论,计算出系统稳态可用度、系统方差、系统吞吐率、系统稳态队长及各系统稳态概率等系统性能指标.同时,通过数值实验对各系统参数对系统性能的影响进行了初探.文中的敏感性分析体现了这种方法的有效性和可用性.实验表明,文中提出的模型,可有效改善仅带有工作休假或工作故障策略排队模型的系统性能.     

考虑多维修台异步多重休假的温贮备冗余系统可靠性模型

考虑多维修台保障多个系统时维修力量存在调度与分配的情况,引入多维修台异步多重休假策略;以温贮备冗余系统为研究对象,针对以往研究利用指数分布等典型分布导致模型约束条件过于严格的问题,采用连续phase-type(PH)分布描述系统中工作部件寿命、温贮备部件寿命以及维修台休假时间和维修时间,建立通用性更好的系统可靠性解析模型,给出系统可靠度、系统稳态可用度等冗余系统可靠性指标和稳态忙期维修台数量等维修台稳态指标;利用算例验证模型适用性,演示了维修台数量、系统温贮备部件数量变化以及修理工休假速率、维修速率变化对系统各可靠性指标和维修台稳态指标的影响.算例计算结果表明,所提出的可靠性模型能够有效复现多维修台调度对冗余系统可靠性的影响,从而为维修台数量的合理安排及系统部件数量的优化配置提供理论基础和实践参考.     

具有自重置功能的两部件温贮备可修系统的可靠性分析

该文讨论具有自重置功能的两部件温贮备可修系统.系统有两种修理策略,一是每个部件都有自重置功能,即通过自动错误检测从故障中自动恢复;二是通过修理工修理故障的部件.该文首先研究该系统稳态和瞬时可靠性指标,然后讨论了系统各参数对系统可靠性的影响.     

离散Weibull分布下实现系统可用度的最小波动

基于目前装备系统中存在的新装备在投入使用初期出现瞬时可用度剧烈波动的现象,分析了离散时间下单部件可修系统的瞬时可用度模型,提出了可用度振幅的概念用以刻画这种系统瞬时可用度波动.在此基础上,建立了关于可用度波动振幅的最优模型.然后针对装备工程大量存在离散Weibull分布的假定,用粒子群算法解决了系统可用度最小波动的设计问题,并用两组算例对最优设计模型的有效性给予了验证说明.     

基于ESB的信息交换系统可靠性仿真与分析

基于ESB的信息交换系统可靠性和生存能力分析,对提高整个系统的安全运行水平具有重要作用.可靠性是系统生存能力评估的重要指标,其建模分析一直是系统生存能力评估的难点.为了有效分析基于ESB信息交换系统的可靠性,把信息交换系统建模为串联可修复系统,提出一种概率分析方法对该模型的可靠度和瞬时可用度进行定量分析及比较.仿真结果表明,在给定部件的故障率和修复率等先验概率时,ESB信息交换系统遭受病毒攻击所产生的故障是系统可靠度及瞬时可用度下降的主要原因,修复率对瞬时可用度的提高具有重要作用,运营单位应设法提高系统修复率和抗攻击的能力.     

关于系统可靠性中的瞬时故障的若干考虑

故障可分为永久故障和瞬时故障.本文指出了二者的不同点,并定义了第一类和第二类 瞬时故障,分别计算了这两类瞬时故障在(0,t)时间内不导致系统故障的概率.     

考虑老化因素的串联系统不完全维修决策优化

针对Markov过程和虚拟役龄方法难以全面描述系统不完全维修的问题,构建基于准更新过程的串联系统可用度分析模型,提出平均故障间隔时间和平均维修间隔时间确定方法;引入运行时间缩减因子、维修时间增长因子描述考虑老化因素的不完全维修过程,确定系统可用度指标确定方法;根据单位时间维修成本、系统平均运行时间约束条件,确定系统在不同指标下的不完全维修次数.以某控制系统为例,应用传统方法验证不完全维修条件下可用度确定方法的有效性,并以维修成本、运行时间为约束确定不同条件下的不完全维修次数,为维修决策制定提供理论指导.     

Optimal replacement policy for a repairable system with multiple vacations and imperfect fault coverage

The present investigation deals with the reliability analysis of a repairable system consisting of single repairman who can take multiple vacations. The system failure may occur due to two types of faults termed as major and minor. When the system has failed due to minor faults, it is perfectly recovered by the repairman. If the system failure is due to major faults, there are some recovery levels/procedures that recover the faults imperfectly with some probability. However, the system cannot be repaired in ‘as good as new’ condition. It is assumed that the repairman can perform some other tasks when either the system is idle or waiting for recovery from the faults. The life time of the system and vacation time of the repairman are assumed to be exponential distributed while the repair time follows the general distribution. By assuming the geometric process for the system working/vacation time, the supplementary variable technique and Laplace transforms approach are employed to derive the reliability indices of the system. We propose the replacement policy to maximize the expected profit after a long run time. The validity of the analytical results is justified by taking numerical illustrations.     

特殊状态需要特殊修理的诊断可修系统

研究了特殊状态需要特殊修理的诊断可修系统.假设系统有三种运行状态:正常状态、 异常状态和故障状态,有些异常状态和故障状态需要特殊的修理,但哪些异常状态和故障状态 需要特殊修理必须诊断后才能知道.利用概率分析和补充变量方法,求得了系统的重要可靠性 指标.     

Bayesian assessing for a repairable system with standby imperfect switching and reboot delay

System performance measures of a repairable system are studied from a Bayesian viewpoint with different types of priors assumed for unknown parameters, in which the system consists of two active components and one warm standby. There is a failure probability q that switches from standby state to active state. Time-to-failure of components is assumed to be an exponential distribution. The reboot time and repair time are also exponential distributions. When time-to-failure, time-to-repair and reboot time are with uncertain parameters, a Bayesian assessing is adopted to evaluate system performance measures. Monte Carlo simulation is used to derive the posterior distribution for the steady-state availability and the mean time-to-system failure. Some numerical experiments are performed to illustrate the results derived in this article.     

部分可修系统的可靠性分析

The reliability analysis of a system with repairable failures and non-repairable failures is presented. It is assumed that the system has n repairable failure modes and m non-repairable failure modes. As one repairable failure mode takes place, the system will be repaired after the failure mode is detected, otherwise, it would never work again when attaining one non-repairable failure mode. Thus, the system brings about new reliability indices for having both repairable failures and non-repairable failures. The definitions of the new reliability indices are given, and the calculating methods for them are derived by using probability analysis and the supplementary variable technique.     

Reliability Analysis of Partially Repairable Systems

The reliability analysis of a system with repairable failures and non-repairable failures is presented.It is assumed that the system has n repairable failure modes and m non-repairable failure modes.As one repairable failure mode takes place,the system will be repaired after the failure mode is detected,otherwise,it would never work again when attaining one non-repairable failure mode.Thus,the system brings about new reliability indices for having both repairable failures and non-repairable failures.The definitions of the new reliability indices are given,and the calculating methods for them are derived by using probability analysis and the supplementary variable technique.     

Sensitivity analysis of the machine repair problem with general repeated attempts

In this paper, we propose a machine repair problem with constant retrial policy, wherein if a failed machine finds the repairman busy upon arrival, it enters into an orbit. The machines in the orbit form a single waiting line, and only the one at the head of the orbit repeats its request for repair. The failure times of operating machines and the repair times of failed machines follow exponential distributions. It is assumed that retrial times are generally distributed. We used the supplementary variable technique to obtain explicit expressions for the steady-state probabilities of the number of failed machines in the orbit. We performed sensitivity analysis of the machine availability and operative efficiency with respect to system parameters and the number of machines in operation. The analysis of the busy period and the waiting time were also presented. Finally, we developed a cost model and formulated a cost minimization problem.     

A deteriorating repairable system with stochastic lead time and replaceable repair facility

In this paper, a deteriorating repairable system with stochastic lead time and replaceable repair facility is studied. We assume that the spare system for replacement is available only by an order and the lead time for delivering the spare follows exponential distribution. Moreover, we also suppose that the repair facility may be subject to failure during the repair period. Under these assumptions, by using the geometric process and the supplementary variable technique, some important reliability indices such as the system availability, rate of occurrence of failure (ROCOF) and the probability that the system is waiting for replacement are derived. An ordering policy N − 1 and a replacement policy N based on the number of failures of the system are also considered. Furthermore, employing several Lemmas, the explicit expression of the average cost rate is derived. Meanwhile, the optimum value N^∗ for minimizing the average cost rate could be determined numerically.     

Dependability and performance measures for the databasepractitioner

We estimate the availability, reliability, and mean transaction time (response time) for repairable database configurations, centralized or distributed, in which each service component is continuously available for repair. Reliability, the probability that the entire transaction can execute properly without failure, is computed as a function of mean time to failure (MTTF) and mean time to repair (MTTR). Mean transaction time in the system is a function of the mean service delay time for the transaction over all components, plus restart delays due to component failures, plus queuing delays for contention. These estimates are potentially applicable to more generalized distributed systems