• Smart Structures and Systems
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• 제22권2호
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• pp.151-159
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• 2018

Maintenance activities are regarded as a key part of the repairable deteriorating system because they maintain the equipment in good condition. In practice, many maintenance policies are used in engineering fields to reduce unexpected failures and slow down the deterioration of the system. However, in traditional maintenance policies, maintenance activities have often been assumed to be performed at the same time interval, which may result in higher operational costs and more system failures. Thus, this study presents two non-periodic preventive maintenance (PM) policies for repairable deteriorating systems, employing the failure rate of the system as a conditional variable. In the proposed PM models, the failure rate of the system was restored via the failure rate reduction factors after imperfect PM activities. Operational costs were also considered, which increased along with the operating time of the system and the frequency of PM activities to reflect the deterioration process of the system. A numerical example was provided to illustrate the proposed PM policy. The results showed that PM activities performed at a low failure rate threshold slowed down the degradation of the system and thus extended the system lifetime. Moreover, when the operational cost was considered in the proposed maintenance scheme, the system replacement was more cost-effective than frequent PM activities in the severely degraded system.

• 한국경영과학회지
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• 제24권3호
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• pp.1-11
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• 1999

We consider the problem of determining the spare inventory level for a multiechelon repairable-item inventory system. Our model extends the previous results to the system which has an inventory at the central depot as well as bases. We develop an optimal algorithm to find spare inventory leveis, which minimize the total expected cost and simultaneously satisfy a specified minimum service rate. The algorithm is tested using problems of various sizes to verify the efficiency and accuracy.

• 산업경영시스템학회지
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• 제20권43호
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• pp.99-107
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• 1997

We consider a multiechelon repairable-item inventory system where several bases are supported by a central depot and the external repair facilities. Unlike METRIC- based models, there are only a finite number of repair channels at each base, central depot and the external repair facilities. It is desired to find repair capacities and spares level which together guarantee a specified service level at minimum cost. Closed queueing network theory is used to model the stochastic process. The purpose of this paper is to derive the steady-state distributions of this system.

• 한국신뢰성학회지:신뢰성응용연구
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• 제7권1호
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• pp.13-22
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• 2007

A preventive maintenance model, caller FNBM (${\alpha},{\delta},{\gamma}$) model, is proposed to decide an optimal repair number under achieved availability requirements (r) along with taking two types of failures (repairable or irrepairable) into account. In this model, the current system is replaced by a new one in case when it doesn't meet the achieved availability requirement, even though it is repairable failure; Othewise it is replaced in time of the first irrepairable failure. Assumed that the j-th failure is repairable with probability ${\alpha}_j$ minimal repairs are allowed for repairable failure between replacements. Expected cost rate for preventive maintenance model is developed using NHPP (Non - Homogeneous Poisson Process) in order to de term in the optimal number $n^*$, also numerical examples are shown in order to explain the proposed model. Since the proposed FNBM (${\alpha},{\delta},{\gamma}$) model includes Park FNBM model (1979) and Nakagawa FNBM (p) model (1983) m this proposed model is thought to be better than previous model, especially for weapon system which requires availability as primary parameter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권4호
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• pp.1579-1602
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• 2020

In the design of production system, buffer capacity allocation is a major step. Through polymorphism analysis of production capacity and production capability, this paper investigates a buffer allocation optimization problem aiming at the multi-stage production line including unreliable machines, which is concerned with maximizing the system theoretical production rate and minimizing the system state entropy for a certain amount of buffers simultaneously. Stochastic process analysis is employed to establish Markov models for repairable modular machines. Considering the complex structure, an improved vector UGF (Universal Generating Function) technique and composition operators are introduced to construct the system model. Then the measures to assess the system's multi-state reliability and structural complexity are given. Based on system theoretical production rate and system state entropy, mathematical model for buffer capacity optimization is built and optimized by a specific genetic algorithm. The feasibility and effectiveness of the proposed method is verified by an application of an engine head production line.

• 대한산업공학회지
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• 제40권1호
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• pp.118-127
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• 2014

The configuration such as series, parallel and k-out-of-n of a repairable system directly affects its reliability. The maintenance strategy can also affect the overall performance of the system. The objective of this work is to investigate the possible trade-off between the configuration of a repairable k-out-of-n system and its maintenance strategy. The redundancy is considered to be the design decision variables, whereas the preventive maintenance period is considered to be the maintenance decision variables. The optimization model is used to minimize the overall life cycle cost associated with the system, considering constraint on reliability. Finally, genetic algorithm is used to find the optimal values for the decision variables. The result is compared with optimal values for considering redundancy and maintenance respectively.

• 산업경영시스템학회지
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• 제19권40호
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• pp.23-28
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• 1996

This paper deals with performance measures for recoverable item control where the demand process is time-dependent. The performance measure is essential for modelling a multi-echelon inventory problem for repairable items. Most repairable items are expensive and have a great influence on the performance of equipments. Thus the information on these items is very useful to the decision maker. The purpose of this paper is to derive the system performance measure and the part(component) performance measure considering a cannibalization policy under the dynamic environment.

• 한국통신학회논문지
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• 제40권9호
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• pp.1741-1753
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• 2015

본 논문에서는 MBR 재생부호인 반복분할 부호의 부분접속수를 향상시킬 수 있는 방법에 대해 소개한다. 향상된 부분접속수를 갖는 반복분할 부호를 부분접속 복구 가능한 반복분할 부호라고 한다. 부분접속 복구 가능한 반복분할 부호의 서로 다른 두 가지 생성 방법을 소개하고 각각을 다양한 성능 척도를 통해 분석한다. 새로운 부호는 반복분할 부호에 비해 낮은 부분접속수를 갖는 대신 저장 가능한 최대 파일 크기나 필요한 저장 노드의 수에서 손해가 발생한다. 다른 부분접속 복구 부호와 비교해 향상된 안정성을 갖고 또한 복구시 심벌 연산이 필요 없는 단순전달 복구를 수행함으로써 복구 복잡도를 낮출 수 있다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권3호
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• pp.225-238
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• 2012

In this paper determined is the quantity of repairable concurrent spare parts(CSP) of a new equipment system to maximize the operational availability under budget constraint and cannibalization allowed. When a part fails, the part is replaced and the failed part is repaired for later use while cannibalization is allowed. The failure of a part is assumed to follow a Poisson process and the availability in CSP is defined. The solution procedure consists of two parts. Firstly, a mathematical model is developed under the assumption that the failure rate is constant during the CSP period and cannibalization is not allowed. Secondly, proposed is a simulation search procedure which improves the heuristic solution to the near optimal solution in a reasonable amount of time under the assumption that the cannibalization is allowed.

• 한국군사과학기술학회지
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• 제9권2호
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• pp.51-59
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• 2006

The purpose of this paper is to present reliability analysis procedures for repairable systems and apply the procedures for assessing the reliabilities of two subsystems of a specific group of military equipment based on field failure data. The mean cumulative function, M(t), the average repair rate, ARR(t), and analytic test methods are used to determine whether a failure process follows a renewal or non-renewal process. For subsystem A, the failure process turns out to follow a homogeneous Poisson process, and subsequently, its mean time between failures, availability, and the necessary number of spares are estimated. For subsystem B, the corresponding M(t) plot shows an increasing trend, indicating that its failure process follows a non-renewal process. Therefore, its M(t) is modeled as a power function of t, and a preventive maintenance policy is proposed based on the annual mean repair cost.