Title: A note on a statistical detection method of cascading failure for parallel systems
Authors: Shuhei OTA and Mitsuhiro KIMURA (Hosei University)
Abstract: Cascading failure, one kind of dependent failures, is a phenomenon in which the failure occurrence of one component triggers other failures. The trigger component can cause a huge number of failures after it fails if other components strongly rely on the trigger component. For example, this phenomenon is observed in complex network systems such as blackouts of power transmission systems. As a result, the cascading failure causes the reliability deterioration of the systems. From the viewpoint of reliability management, the factors of the cascading failure should be ideally eliminated before the utilization of the system. In this study, we propose a statistical detection method of the cascading failure occurrence in n-component parallel systems. This research contributes to the cause analysis of the cascading failure occurrence in the n-component parallel system. The cascading failure is modeled by hazard rate switching mechanism. We assume that the lifetime distribution of the remaining components changes if such a trigger component actually exists and fails. The cascading failure occurrence can be detected by identifying the change of the distribution. The performance of the proposed method is demonstrated by simulation studies.
Title: Conditions for the optimal arrangement of a connected-(m-1,s)-out-of-(m,n):F lattice system
Authors: Taishin NAKAMURA, Hisashi YAMAMOTO, Sayaka MATSUO, Xiao XIAO (Tokyo Metropolitan University), and Tomoaki AKIBA (Chiba Institute of Technology)
Abstract: A connected-(r,s)-out-of-(m,n):F lattice system consists of m×n components arranged as an (m,n) matrix, and fails if and only if the system has an (r,s) sub-matrix where all components are failed. One of the most important problems in reliability theory is the component arrangement problem (CAP) on the assumption that component reliabilities are given, and components are interchangeable. The CAP is to find the optimal arrangement of components to maximize system reliability. By taking CAP into account, we can make the best use of limited resources and maximize the performance of the system.
In this study, we provide necessary conditions for the optimal arrangement of the connected-(r,s)-out-of-(m,n):F lattice system in the case of r=m-1. Since we only need to calculate the reliability of the systems corresponding to the arrangements satisfying the necessary conditions, our proposal necessary conditions can considerably reduce the search space for the patterns of component arrangements. We evaluate the performance of the proposed algorithm by numerical experiments.
Title: Compromised life test plan for accelerated degradation test of three factor stress level
Author: Takenori SAKUMURA (Chuo University)
Abstract: Accelerated degradation tests (ADT) are often used to quickly find the life of materials such as electrical insulators. An ADT consists of several high levels of stress and the number of samples at that level. Each sample is subjected to the stress for a certain evaluation time and the degradation rate at that time is measured. The time when the degradation reaches a certain threshold is regarded as the failure time. The lifetime can be predicted from the obtained failure time data under the assumption that the physical law is empirically established between the stress and the lifetime and the logarithmic lifetime follows a specific probability distribution under a certain stress. In this research, focusing on finding the optimum sample allocation number, consider the case where the number of stress levels is three. In order to consider the reality, we use the mathematical model obtained from actual experimental data and its parameter value.
Title: Analysis for the Conditions of Component Assignment for the Optimal Arrangement of a k-Window System
Author: Tomoaki Akiba (Chiba Institute of Technology)
Abstract: k-window system in this study is an application system of the consecutive-k-out-of-n:F system. This system can be expressed to the occurring of a failure in the system when a certain extent intensive components failure happens in the system. One of the most important problems for this kind of system is the optimal arrangement problem. In the previous study, we confirmed by the simulation approaches that optimal arrangement of k-window system. However, this component arrangement depends on the system parameters k, r and components reliabilities. In this study, we provide necessary conditions of component assignment for the optimal arrangement of k-window system by the mathematical analysis.