International Journal of Reliability, Quality and Safety Engineering

In the computer science community, garbage collection is a dynamic storage management technology to ensure the reliability of computer systems. In this paper, we consider two garbage collection policies to meet the goal of time consumption for a generational garbage collector when increase in objects might be unclear at discrete times for the high frequency of computer processes. That is, (a) tenuring collection is triggered at the $n$th minor collection preventively or at a threshold amount $K$ of surviving objects correctively, and (b) major collection is made at discrete times $JT$ for a given $T$ or at the $N$th collection including minor and tenuring collections. Using the damage process and renewal theory, the expected cost rates are obtained, and their optimal policies for tenuring and major collection are discussed analytically and computed numerically.

In this paper, a random repairable $k$-out-of-$n$ system is studied when random replacement policies are performed, where $k$ is a stochastic parameter. It is replaced before failure at a planned time $T$ or at random working cycle $Y$, whichever occurs last or first. Furthermore, optimal replacement policies are obtained for the extended models with working numbers. This paper aims to find the optimal replacement policies when replacement first and last policies are performed. Expected cost rates for the first and last replacement policies are derived, and their optimal replacement policies are derived analytically. Numerical examples are given to illustrate the theoretical results.

This paper takes up managerial maintenance policies during different phases for mission executions. When a mission execution is divided into two phases and three phases respectively, replacement, minimal repair and keeping failure status become alternatives for managerial maintenance policies. Further, we give approximations of the above managerial maintenance policies to make the computations simple. In this paper, keeping failure status is considered as the last choice for the last phase of mission executions. We aim to minimize the expected maintenance costs for the total mission executions. All of the discussions are made analytically and their numerical examples are given.

This study supposes a single unit and investigates cumulative damage and catastrophic failure models for the unit, in situations where the interarrival times between the shocks, and the magnitudes of the shocks, involve two different stochastic processes. In order to consider two essentially different stochastic processes, integer gamma and Weibull distributions are treated as distributions with two parameters and extensions of exponential distributions. With respect to the cumulative damage models, under the assumption that the interarrival times between shocks follow exponential distributions, the case in which the magnitudes of the shocks follow integer gamma distributions is analyzed. With respect to the catastrophic failure models, the respective cases in which the interarrival times between shocks follow integer gamma and Weibull distributions are discussed. Finally, the study provides some characteristic values for reliability in such models.

This paper applies the inspection policy in reliability theory to social integrations. As a result of shortage of labor forces due to the declining birthrate, many developed countries are increasingly accepting immigrants. However, it has been shown that the acceptance of immigrants increases anti-immigrant sentiment among host citizens and leads to large-scale riots. While social integration policies such as language education for new immigrants and support for labor market can reduce anti-immigrant sentiment, they need high costs. It is necessary to detect the anti-immigrant sentiment based on regular public polls and implement social integration. However, there is no empirical study that proposes the expected costs until the anti-immigrant sentiment is detected and discuss the optimal checking times which minimize them. We formulate three stochastic models, replacing inspection of units with check of the social structure such as people’s feelings for immigrants and failure with riot. This paper proposes extended stochastic models of social structures considering the suppression of a riot. We obtain the expected costs until a riot ends and discuss optimal checking times which minimize them analytically and numerically. These methods used in this paper could be applied to some social problems occurred in the world.

Product fault diagnosis has been a focus of research in the field of quality control. Many studies have been made to ensure the accuracy of fault diagnosis in electromagnet quality control direction. However, in the pursuit of perfect identification method, the fault diagnosis process is extremely complex in quality control management. A new fault diagnosis method for quality control of electromagnet machining processes based on $T$–$S$ fault tree and grey relation degree analysis is proposed in this paper. First, $T$–$S$ fault tree is used to analyze and describe the dynamic fault relationship of the electromagnet machining processes. In order to make the fault mode more intuitive and specific, $T$–$S$ fault tree logic diagram is used to describe the actual fault form of machining processes. Second, according to the fault output algorithm of $T$–$S$ fault tree, the fault rate of basic event in each cycle is calculated and the fault rate of intermediate event and top event in each cycle is obtained. Then, the grey relation method is applied to calculate the relation between the basic event and the trend of top event failure rates in electromagnet machining processes. Based on the obtained relation degree, the faulty system of electromagnet machining processes can be repaired pertinently and achieve the purpose of quality control. Finally, an example of electromagnet quality control’s fault diagnosis is used to verify the objectivity and simplicity of the new method.

This study focuses on developing an algorithm to compute the system signatures of linear and circular connected-$(1,2)$-or-$(2,1)$-out-of-$(m,n)$:F lattice systems. In reliability engineering, system signatures have diverse theoretical applications, such as conducting stochastic comparisons of certain systems, deriving mean time to failure, and providing optimal maintenance policy. However, the complexity involved in computing the system signature increases with the increase in the number of components, making the aforementioned applications challenging. Moreover, the computation of system signatures for connected-$(1,2)$-or-$(2,1)$-out-of-$(m,n)$:F lattice systems has not been sufficiently discussed. Thus, this study proposes an algorithm for computing the system signatures of both linear and circular connected-$(1,2)$-or-$(2,1)$-out-of-$(m,n)$:F lattice systems. Numerical experiments were conducted to investigate the efficiency and it was determined that the proposed algorithm can generate system signatures that the enumerative method cannot obtain. Consequently, the proposed algorithm will contribute to various applications.

In this study, an unreliable machine repair system with warm standby switching failure and retrial behavior is examined. An application of the Ceph storage cluster system is described to illustrate the applicability of the proposed model and establish its results. To analyze the reliability of the application system, two-state-transition rate diagrams and their associated differential-difference equations are provided. Laplace transforms and the matrix-analytical method are employed to obtain the steady-state probabilities. Explicit expressions for the reliability function, mean time to failure, and steady-state availability of the examined system are then derived. With these system performance measures, we perform a sensitivity analysis of the system parameters to identify critical variables. Furthermore, the numerical results for various parameter settings are tabulated and presented graphically. Finally, managerial insights and constructive results are provided as a guide for managers in determining an effective strategy for performance enhancement.