Using repair-depot system reliability to determine the distributionof supportability turn-around time

Assuming constant repair times, Linton, et al. (1995) used an `expression for the reliability of the system for repairing failed units (FU) at a repair-depot' to compute the longest repair time for a newly failed unit (NFU) which assures a given reliability level (also termed the NFU supportability turn-around time, STAT) in terms of the: (1) constant failure rate for all components, number of spares (s) on-hand; (2) number (n) of FU either `under repair' or `scheduled to begin repair in the future'; and (3) downstream repair completion times (DRCT) for FU. Since subtraction of the repair time for a NFU from its STAT-value yields the NFU's latest repair start-time (LRST) which assures a given repair-depot system reliability (RDSR), STAT-values are important for scheduling RST. This paper assumes that repair time is a random variable and, consequently, DRCT is a random variable. As shown in Linton, et al, (1995), STAT is the zero of a nonlinear, nonpolynomial function of DRCT; thus, STAT is also a random variable, and determining the distribution of STAT is a stochastic root-finding problem. For n=1 and s⩾0, numerical analysis and probability theory are used to find the Cdf and pdf of STAT in terms of any repair time pdf. Using the pdfs for STAT and repair time, expressions are derived for: (1) E{LRST} for a NFU; and (2) q=Pr{(repair time+c)相似文献   

Analysis of system reliability with dependent repair modes

This paper proposes an imperfect-repair model for repairable systems where two repair modes, perfect and minimal, occur in accordance with a Markov chain. It investigates the characteristics of the model and presents a statistical procedure for estimating the lifetime distribution of the system, based on consecutive inter-failure times. Under the Brown-Proschan imperfect repair model, the system is repaired to: good-as-new under perfect-repair, its “condition just prior to failure” under minimal-repair. This imperfect-repair model generalizes the Brown-Proschan imperfect-repair model, by allowing first-order dependency between two consecutive repair modes. The model assumes that, at failure, the system undergoes either perfect repair (restore to like new) or minimal repair (restore to like “just before failure”), and the repair modes are subject to a Markov process. The estimation procedure is developed in a parametric framework for incomplete data where some repair modes are not recorded. The s-expectation-maximization principle is used to address the incomplete-data problem. Under the assumptions that the lifetime distribution belongs to a parametric family having aging property and explicit form of the survival function, an algorithm is developed for finding the MLE (maximum likelihood estimates) of the reliability parameters; the transition probabilities of the repair modes, as well as the distribution parameters. A Monte Carlo study shows the consistency, effect of aging rate, effect of transition types, and effect of missing data, for the estimates     

On computing the repair cost of a maintained reliability system with known repair cost function and probability of repair

In this paper, a simplified analytic cost model for maintained reliability system under opportunistic repair scheme is discussed. Life cycle cost curves under various operating life cycle times and linear repair cost function is derived.     

Complex system reliability with general repair time distributions under preemptive repeat repair discipline

The behaviour of a complex system having “N” components in series in class L₁ and “m” identical components in parallel redundancy in class L₂, has been investigated. It has been assumed that a failure in L₁ brings about the complete break-down of the system whereas the failure of any two components of class L₂ causes the system to work in a state of reduced efficiency. The repair of the failed components in the class L₁ and L₂ is carried out under Preemptive Repeat Repair Discipline⁽⁵⁾. Laplace Transforms of various state probabilities, viz. the system is in up state, reduced efficiency state and down state, have been obtained. In the end, asymptotic behaviour of the complex system, has also been discussed.     

Using a software reliability model to design a telecommunicationssoftware architecture

The author proposes a software reliability model for a large real-time telecommunications software architecture. Some simple examples of the critical components of the software architecture and their dependencies are described. The component dependencies permit the propagation of faults from the component in which the fault originates to the other components. This propagation can cause failures in the chain (or in the tree) of components. Detection and failures depends on the tests executed or on the number and type of customer requests. An error can occur in any component. This error can be caused by a fault that propagated from another component or it can be a fault that originates in that component. The error can be traced through the component-dependency chain (or tree) to repair all the faults that are associated with that error. The software reliability model guides the design of the software architecture     

Complex system reliability with exponential repair time distributions under head-of-line-repair-discipline

In this paper the behaviour of a complex system, composed of two classes of components L₁ and L₂, has been investigated. It has been assumed that the repair of the failed components in classes L₁ and L₂ is carried out under the “head-of-line-repair-discipline”. Laplace transforms of the various state probabilities have been obtained. Inversions have also been carried out to obtain time-dependent probabilities. In the end, the behaviour of this system under steady state has also been examined.     

Cost analysis of a two-unit warm standby reliability system with two types of repair facilities

This paper deals with a two-unit warm standby system. These units are identical, but have different failure rates and repair time distributions, when failed in operating or standby state. If the unit fails in operating state, we wait for the repairman for some maximum time or until the other unit fails, and if the unit fails in standby state we wait for the repairman until the other unit fails. On the failure of the second unit or on the completion of the maximum time, we call the repairman immediately at the higher cost.The system has been analysed to determine the various reliability measures by using semi-Markov processes and regenerative processes. Numerical results pertaining to some particular cases are also added.     

Distribution of time to non-availability of a reliability system

The author derives in this paper the distribution of the time to non-availability of a system which under-goes the following states, viz. (i) operative (ii) failed, and (iii) repair. Special cases are discussed and tables are provided at the end.     

Using statistically designed experiments to improve reliability andto achieve robust reliability

This tutorial explains statistically designed experiments which provide a proactive means to improve reliability as advocated by Genichi Taguchi. That is, by systematic experimentation, the important parameters (factors) affecting reliability can be identified along with parameter values that yield reliability gains. In addition to improving reliability, Taguchi's robust design can be used to achieve robust reliability; that is, to make a process or product reliability insensitive to factors which are hard or impossible to control. Robust design is also implemented using statistically designed experiments. This paper presents classes of experimental plans for reliability improvement and robust reliability. An important feature of the reliability data collected from such experiments is censoring which occurs when some of the experimental units have not failed by the end of the experiment. Consequently, the analysis methodology must account for these censored data which are likely to occur in light of the ever increasing reliability of today's products. Several appropriate methods are discussed briefly. These experimental plans and analysis methods are illustrated using three documented experiments which improved fluorescent lamp and industrial thermostat reliability and which achieved robust reliability for night-vision goggles     

基于MATLAB仿真的系统稳定性判定的分析

稳定性是系统本身的属性,与输入信号无关.但任何系统要使其能对输入信号进行处理,都必须以系统稳定为先决条件.所以设法判断系统的稳定与否十分重要.以常用的二阶有源系统为例,分别采用两种方法进行稳定性分析,从而得出采用MATLAB仿真进行系统稳定性判定是一种方便有效方法的结论.     

Periodic replacement with minimal repair at failure and general random repair cost for a multi-unit system

A policy of periodic replacement with minimal repair at failure is considered for the multi-unit system which have the specific multivariate distribution. Under such a policy an operating system is completely replaced whenever it reaches age T (T > 0) at a cost c₀ while minimal repair is performed at any intervening component failures. The cost of the j-th minimal repair to the component which fails at age y is g(C(y),c_j(y)), where C(y) is the age-dependent random part, c_j(y) is the deterministic part which depends on the age and the number of the minimal repair to the component, and g is an positive nondecreasing continuous function. A simple expression is derived for the expected minimal repair cost in an interval in terms of the cost function and the failure rate of the component. Necessary and sufficient conditions for the existence of an optimal replacement interval are exhibited.     

利用激光扫描共聚焦显微成像系统的正交切割成像确证GFP标记细菌在植物根内定殖

用激光扫描共聚焦显微镜（LSCM）检测绿色荧光蛋白（GFP）标记的细菌常用来确证植物内生细菌的内生特性。本文通过用GFP标记的内生细菌侵染植物根,用LSCM分别检测植物的根段或根的徒手横切片,显示LSCM系统的无损伤光学切片和正交切割成像适用于确证GFP标记细菌在植物根内定殖,显示徒手切片对揭示细菌定殖模式及其入侵途径的不良影响,并依此更新LSCM检测GFP标记细菌在植物根内定殖的方法。     

Using formal methods in a design for reliability as applied to an electronic system that integrates software and hardware to perform a function

Formal methods of design are neglected areas with very little current work. At present, requirements analysis and high-level design are rarely treated in a disciplined way by design engineers. Yet errors committed in these stages are most difficult to detect and costly to remove. The paper presents a formal approach to development of systems with high reliability, taking into account safety-critical factors as and when they are relevant. It discusses how formalism may be used to support direct requirements expression and realization.     

A new approach to system reliability

Calculating system-reliability via the knowledge of structure function is not new. However, such attempts have had to compromise with the increasing complexity of a system. This paper overcomes this problem through a new representation of the structure function, and demonstrates that the well-known systems considered in the state-of-art follow this new representation. With this new representation, the important reliability calculations, such as Birnbaum reliability-importance, become simple. The Chaudhuri, et al. (1991) bounds which exploit the knowledge of structure function were implemented by our simple and easy-to-use algorithm for some s-coherent structures, viz, s-series, s-parallel, 2-out-of-3:G, bridge structure, and a fire-detector system. The Chaudhuri bounds are superior to the min-max and Barlow-Proschan bounds. This representation is useful in implementing the Chaudhuri bounds. With this representation of the structure function, the computation of important reliability measures such as the Birnbaum structural and reliability importance are easy. The use of Chaudhuri bounds is recommended for general use, especially when cost and/or time are critical. The C-H-A algorithm (in this paper) is simple and easy to use. It depends on the knowledge of the path sets of a given structure. Standard software packages are available to provide the minimal path sets of any s-coherent system. The C-H-A algorithm has been programmed in SAS, S-PLUS, and MATLAB     

Using modulation instability to determine Kerr coefficient inoptical fibres

The power and polarisation dependence of modulation instability were experimentally investigated and used to obtain a novel, simple and accurate method for the measurement of Kerr coefficient in optical fibres. New results on dispersion shifted fibres are reported, giving n ₂=2.64×10²⁰m²/W at 1553 nm (linear polarisation)     

Using FHT to determine digital straight line chain codes

A novel application of the fast Hartley transform is proposed. Using the FHT, the straightness of a digital arc can be determined from the periodicity of its chain codes. Further results for the new approach in four of Lee's examples demonstrate that the new application is promising.<>     

Burn-in and thermal cyclic tests to determine the short-term reliability of a thin film resistance temperature detector

In this paper, experimental data and theory are presented for two methods of the thermal failure of a multi-layer, thin film resistance temperature detector (RTD). The methods are: (i) while placed in a low pressure inert gas atmosphere, the temperature of the RTD was increased incrementally by means of joule heating until failure (burn-in test), and (ii) the RTD was thermally cycled in both a low-pressure inert gas atmosphere as well as in air at atmospheric pressure. The performance of the RTD was analyzed with respect to three factors: (i) changes in electrical resistivity with respect to temperature of the Ti–Cu–Ti trace that forms the conductive path of the RTD, (ii) degradation of the encapsulation layers, especially the Benzocyclobutene (BCB) with emphasis on its impact on radiation, and (iii) failure of the trace due to crack formation. Environmental effects on performance and probable causes of failure are discussed.     

A reliability physics model for dissimilar two-unit standby system with single repair facility

In this paper, the reliability and availability analysis of a repairable dissimilar two-unit standby system is carried out using stress-strength failure model. Single repair facility with the time taken to repair a unit being either deterministic or random has been considered. The analysis is carried out for arbitrary stress, strength and repair time distributions.