开关寿命连续型n部件冷贮备系统的可靠性分析

为了讨论由n个同型部件和一个转换开关组成的冷贮备不可修系统的可靠度,假设部件的工作时间和转换开关的寿命均服从指数分布、所有随机变量均相互独立,首先根据系统的特征和可靠度的定义研究并求出三部件冷储备系统可靠度的解析式,然后在三部件冷储备系统可靠度研究的基础上建立了n部件冷贮备系统的可靠性关于部件个数n的递推关系式,最终得到系统的可靠度的解析表达式.计算过程对其他多部件系统可靠度的推导有一定的借鉴作用,计算结果具有一定的理论价值.     

有优先权且工作故障与贮备故障后的修理时间不相同的温贮备系统的可靠性分析

为了解决开关寿命为连续随机变量且部件工作故障的修理时间与贮备故障后的修理时间各不相同的问题,利用Markov过程理论和Laplace变换方法,研究了有优先权的两不同型部件和两不同修理工组成的温贮备可修系统.假定部件的工作寿命、贮备寿命、工作故障的修理时间和贮备故障的修理时间均服从不同的指数分布,得到了该系统的可靠度Laplace变换和系统的首次故障前平均时间的解析表达式.     

双开关的三部件冷贮备系统可靠性分析

双开关的冷贮备系统,会提高冷贮备部件的使用效率.讨论由三个不同型部件和双开关组成的冷贮备不可修系统和可修系统,转换开关是完全可靠的,且每次只能转换一个开关.首先假设部件的工作寿命和维修时间都服从指数分布、所有随机变量均相互独立,求出了不可修系统可靠度.然后考虑在工作期间系统会受到泊松冲击过程和自然退化过程的影响,分析了在泊松冲击下双开关的三部件冷贮备系统的退化模型,得到了系统可靠度的计算公式.最后利用马尔可夫过程理论讨论了可修系统,在优先权的条件下求出系统可靠性的稳态指标、平均指标、系统可靠度以及首次故障前平均时间.     

开关寿命连续型冷贮备可修系统的可靠性分析：两不同部件构成的可修系统

本对由两个不同部件组成的,而且开关寿命为连续随机变量的冷贮备可修系统作了研究,建立了该类系统的一般模型,给出了系统可靠度R(t）的L-变换和首次故障前的平均时间的结果。     

修理设备可更换和修理延迟的两类故障状态并联可修系统

考虑两同型部件组成的并联可修系统,每个部件有两类故障状态,部件故障后修理有延迟,且修理设备在修理故障部件的过程中也可能发生故障.假定部件的寿命和修理设备的寿命服从指数分布,部件发生故障后的修理延迟时间、修理时间和修理设备故障后的更换时间均服从一般分布,利用马尔可夫更新过程理论和拉普拉斯变换工具,求得了系统有关的可靠性指标.     

部件有两类故障状态且修理设备可更换的并联可修系统分析

本文考虑由两个同型部件组成的并联可修系统,每个部件有两类故障状态,部件故障后立即修理,且修理设备在修理故障部件的过程中也可能发生故障.假定部件的寿命和修理设备的寿命均服从指数分布,部件发生故障后的修理时间和修理设备故障后的更换时间均服从一般分布,利用马尔可夫更新过程理论,求得系统的有关可靠性指标和修理设备的闲期长度和"广义忙期"长度等一系列结果.     

有优先权三不同部件温贮备可修系统可靠性分析

针对由三个不同部件,一个完全可靠的开关和一个修理设备组成的温贮备可修系统,建立了部件的工作寿命,贮备寿命,工作故障后的修理时间和贮备故障后的修理时间均服从不同参数的指数分布的数学模型,利用Markov型可修系统的研究方法,并采用MATLAB软件给出了该系统的首次故障前的平均时间、可用度和故障频率等可靠性指标的表达式.     

具有修理延迟的两不同部件冷贮备系统的可靠性分析

研究了有修理延迟的两个不同部件和两个修理工组成的冷贮备系统.假定部件的工作寿命服从一般分布,故障后的延迟修理时间和修理时间均服从指数分布.利用马尔可夫更新过程、拉普拉斯变换和拉普拉斯-司梯阶变换工具,得到了系统的首次故障前时间、可用度和平均故障次数等可靠性指标.     

两个同型部件温贮备系统的几何过程模型

利用可靠性理论,研究了两个同型部件和一个修理工组成的可修型温贮备系统.假设两个部件的工作寿命、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,在工作故障和贮备故障都不能"修复如新"的情况下,运用几何过程理论、拉普拉斯变换和补充变量方法得出该模型的一些可靠性指标.     

修理设备可更换且修理工多重延误休假的单部件可修系统

假定部件的寿命、修理时间和修理工的休假时间均服从一般连续型分布.修理工的延误休假时间服从指数分布,并且修理设备的寿命服从爱尔朗分布,其更换时间服从一般连续型分布的情况下,研究了修理设备可更换且修理工可多重延误休假的单部件可修系统.通过使用补充变量法、广义马尔可夫过程方法和拉普拉斯变换工具,讨论了系统的瞬时可用度、稳态可用度以及(0,t]时间内系统的平均故障次数和稳态故障频度,得到了系统和修理设备主要可靠性指标的拉普拉斯变换表达式.     

一可修系统的最优检测更新模型

本文研究了由一个部件和一个修理工组成的检测更新模型。部件不能“修复如新”。其寿命和修理时间均服从一般分布。在假设最大的修理次数为K—1的条件下,证明了最优检测时间T的存在,此时模型取得最大经济效益。     

Compartmental modelling of equipment subject to partial repair

A semi-Markov model for equipment that can be repaired and returned to service in a less than new state is developed, where several less than new states are possible before the equipment finally fails. A subclass of phase-type distributions is used to model the times spent in each of these states. Then, exploiting the phase-type structure, the composite distribution of the entire lifetime of the equipment can be constructed. Data from railway wagon wheel-sets are used to illustrate this modelling and data analysis.     

A discrete-time model of failure and repair

In this paper the authors introduce and study a model of failures and repairs of units with discrete lifetimes. They suppose that a unit has a sequence of tasks to perform and that its lifetime is measured by the number of tasks performed before its final, fatal failure. Upon a failure the unit may be repaired (with some probability) and then it may attempt again to perform the current task. The unit dies when (with some probability) a repair cannot be completed. We derive some stochastic comparisons of pairs of such models. The stochastic comparisons are then applied for obtaining results regarding the inheritance of several aging properties by the repaired unit. Various examples illustrate the applicability of the model. Some variants of the model of this paper can be viewed as discrete analogues of the notion of imperfect repair.     

A mixed integer nonlinear programming model for the optimal repair–replacement in the firm

Optimal repair–replacement problem is an important aspect of economic decision making at the firm and aggregate levels. In this paper, we extend the continuous time optimal replacement model in the firm under technological progress by considering the possibility of repairing/replacing the machines during their lifetime period. In our model, two possible decisions can be recognized by the managers in which the machines are repaired under the efficiency condition or replaced under the availability of technological progress in the firm. As a special case, we restrict the model to the more real case in which all the growth, purchase price and repair cost functions are assumed to be in the exponential form. The solvability of the model in this case is also discussed.     

Exact approaches for lifetime maximization in connectivity constrained wireless multi-role sensor networks

In this paper, we consider the duty scheduling of sensor activities in wireless sensor networks to maximize the lifetime. We address full target coverage problems contemplating sensors used for sensing data and transmit it to the base station through multi-hop communication as well as sensors used only for communication purposes. Subsets of sensors (also called covers) are generated. Those covers are able to satisfy the coverage requirements as well as the connection to the base station. Thus, maximum lifetime can be obtained by identifying the optimal covers and allocate them an operation time. The problem is solved through a column generation approach decomposed in a master problem used to allocate the optimal time interval during which covers are used and in a pricing subproblem used to identify the covers leading to maximum lifetime. Additionally, Branch-and-Cut based on Benders’ decomposition and constraint programming approaches are used to solve the pricing subproblem. The approach is tested on randomly generated instances. The computational results demonstrate the efficiency of the proposed approach to solve the maximum network lifetime problem in wireless sensor networks with up to 500 sensors.     

Consecutive k-out-of-n systems with maintenance

A consective k-out-of-n system consists of n linearly or cycliccally ordered components such that the system fails if and only if at least k consecutive components fail. In this paper we consider a maintained system where each component is repaired independently of the others according to an exponential distribution. Assuming general lifetime distributions for system's components we prove a limit theorem for the time to first failure of both linear and circular systems.     

三同型部件冷贮备可修系统可靠性的密度演化方法

本讨论了三个同型部件、一个修理工组成的冷贮备可修系统的可靠性，所假定的部件的寿命和修理时间均服从一般分布，所使用的方法是密度演化法．     

The EOQ repair and waste disposal model with variable setup numbers

In a previous paper the author discussed an EOQ model in which the stationary demand can be satisfied by newly made products and by repaired used products. In the modelled situation some share of the used products is collected and later repaired; the other products are disposed outside according to some waste disposal rate. In the present paper this model is extended to the case of variable setup numbers n and m for production and repair within some collection time interval. First, for a fixed waste disposal rate the cost optimal setup numbers and the minimum cost are determined. Secondly, the minimum cost is analysed as a function of this rate and it is shown to be convex for small and medium waste disposal rates and to be concave for large rates. Thirdly, the existence and generation of cost optimal waste disposal rates are discussed.     

A multiple warm standby system with operational and repair times following phase-type distributions

We study a warm standby n-unit system. The system functions as long as there is one operative unit. When the unit online fails, a unit in standby becomes the new unit online, if any. When a unit fails it goes to repair. There is a repairman. The units are repaired following the arrival order. The unit online has a lifetime governed by a phase-time distribution. The repair times follow a phase-type distribution. The warm standby units have lifetimes exponentially distributed. All the other times are negligible. This system extends many others of frequent use in the literature. We show that this system is governed by a level-dependent quasi-birth-and-death process (LDQBD process). The availability, rate of occurrence of failures and other magnitudes of interest are calculated. The mathematical expressions are algorithmically and computationally implemented, using the Matlab programme.