• 산업경영시스템학회지
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• 제43권1호
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• pp.61-69
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• 2020

Systems such as database and socal network systems have been broadly used, and their unexpected failure, with great losses and sometimes a social confusion, has received attention in recent years. Therefore, it is an important issue to find optimal maintenance plans for such kind of systems from the points of system reliability and maintaining cost. However, it is difficult to maintain a system during its working cycle, since stopping works might incur users some troubles. From the above viewpoint, this paper discusses minimal repair maintenance policy with periodic replacement, while considering the random working cycles. The random working cycle and periodic replacement policies with minimal repair has been discussed in traditional literatures by usually analyzing cases for the nonstopping works. However, maintenance can be more conveniently done at discrete time and even during the working cycle in real applications. So, we propose that periodic replacement is planned at discrete times while considering the random working cycle, and moreover provide a model in which system, with a minimal repair at failures between replacements, is replaced at the minimum of discrete times KT and random cycles Y. The average cost rate model is used to determine the optimal number of periodic replacement.

• 품질경영학회지
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• 제48권1호
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• pp.201-214
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• 2020

Purpose: The purpose of this paper is to determine an optimal number of cycle times for the replacement under the circumstance where the system is replaced at the periodic time and the multiple number of working cycles whichever occurs first and the system is minimally repaired between the replacements if it fails. Methods: The system is replaced at periodic time () or cycle time, whichever occurs first, and is repaired minimally when it fails between successive replacements. To determine the optimal number of cycle times, the expected total cost rate is optimized with respect to the number of cycle times, where the expected total cost rate is defined as the ratio of the expected total cost between replacements to the expected time between replacements. Results: In this paper, we conduct a sensitivity analysis to find the following results. First, when the expected number of failures per unit time increases, the optimal number of cycle times decreases. Second, when the periodic time for replacement becomes longer, the optimal number of cycle times decreases. Third, when the expected value for exponential distribution of the cycle time increases, the optimal number of cycle times increases. Conclusion: A mathematical model is suggested to find the optimal number of cycle times and numerical examples are provided through the sensitivity analysis on the model parameters to see the patterns for changes of the optimal number of cycle times.

• International Journal of Reliability and Applications
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• 제12권2호
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• pp.117-122
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• 2011

In this paper, we suggest the optimal replacement policy following the expiration of repair warranty when the cost of minimal repair depends on the age of system. To do so, we first explain the replacement model under repair warranty. And then the optimal replacement policy following the expiration of repair warranty is discussed from the user's point of view. The criterion used to determine the optimality of the replacement model is the expected cost rate per unit time, which is obtained from the expected cycle length and the expected total cost for our replacement model. The numerical examples are given for illustrative purpose.

• KIEAE Journal
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• 제12권5호
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• pp.35-42
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• 2012

The rental housing has been a main role to supply a living space to the household who can not be available for the home-owner. Specially, the public rental housing is targeted for the low-income household and supplied with low rental fee. Therefore, the rent owner should manage and maintain the housing condition decently with a systematically maintenance plan which includes a repair time and scope, a repair cost. Among them, the repair time is important to make a repair plan. The repair time would be explained with two types, which is divided into a breakdown maintenance and a preventive maintenance. Each of them has a advantage in a repair cost, maintenance of the living condition and provision of the repair scope and method. In this paper, it aimed at providing the repair time in 12 components of the public rental housing which is reflected from a preventive maintenance. This study shows that overall, a permanent rental housing has a longer repair time than any other rental housing in 12 housing components. A public rental housing is closer to the a permanent rental housing then a redevelopment rental housing in repair time. On the other hand, the repair time of the 12 housing components is different form the rental housing. This leads to further study in difference of the repair time according to a tenant type.

• KIEAE Journal
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• 제12권5호
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• pp.29-34
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• 2012

A rental housing has a key role to supply the living space to non-ownership. A public rental housing is particularly aimed at providing the living space for the low-income households with a low rent fee. Therefore, the local government would try to maintain the facilities of the rental housing and to get the decent living condition. For getting the required living condition, it should make a maintenance plan, which contains the repair time, repair scope and targeted component and finishings. This study is aimed at providing the optimal repair time in 12 components and components of the rental housing which is controlled by the local government. The optimal repair time has two steps to get the final result. First, it would draw the 1'st repair time with the probabilistic and empirical approach. Second, comparing the drawn data and the service life, the optima repair time would be provided with considering the components' attributes. Result are as follows : First, the optimal repair time would be considered with the component attributes. There are user's convenience, its safety and physical aspect. Second, the kitchen utensils, elevator and water tap has a optimal time of 16, 19, 17 years respectively which is considered with physical aspect. In addition, the optima repair time of the wiring appliance and lighting equipment are 12 years and 10 years respectively.

• KIEAE Journal
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• 제15권1호
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• pp.69-75
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• 2015

Building has required the repair money to improve or maintain the decent living condition continuously after construction. It needs to grasp the building deterioration to decide the scope and contents before it is repaired. Under various conditions such as physical, social and financial constraints, the repair plan would be prepared. Among constraints, the cost is indispensible to specify the repair time, repair scope and target. The required cost would be planned to preparation over the years. In this paper, it aimed at providing the repair strategy of the public rental housing in repair time, using the cumulative cost model which is $3^{rd}$ function. In the $3^{rd}$ function, the inflection point should exist in the line. And there are two types in the cumulative model, First, if the maximum cost be shown, the repair time would be provided. Second, if the maximum cost not be shown, the cumulative function should be proportionally increased and the repair strategy is properly provided with a short cycle. In results of this study, 11 items would provide the repair time. These cumulative function would be repaired about 4 years after constructed, and after about 4 years, the cumulative function would be continuously increased.

• KIEAE Journal
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• 제14권5호
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• pp.5-12
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• 2014

Building has been deteriorated gradually owing to geographic, physical complex and other factors. School living condition has a key role to improve the learning ability, life attitude and qualifications to adopt to social life. Therefore, it is important for school environment to keep the living condition. Repair time and scope of school facilities are required to maintain the function and performance to plan the long term repair. But there are little information about the school maintenance such as repair time and function. In this paper, it aimed at providing the service life to suggest the repair time and scope in the roof-proofing and floor finishing which used the three estimation method in probabilistic approach. The service life has a key role to decide the repair time and to make the plan for the repair maintenance. Results of this study are as follows ; First, the 1st repair time were taken through three methods in probabilistic and deterministic functions to eliminate the estimation bias. Second, the service life is suggested 36 years of an elementary school, 34 years of a middle school and 41 years of a high school. Third, the service life of a floor finishing is 43 years of an elementary, 39 years of a middle school and 41 years of a high school. The above study could not include the detailed information about the materials and repair works. Therefore it needs a further study to reflect the detailed information and to make a repair strategy.

• International Journal of Reliability and Applications
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• 제18권1호
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• pp.1-8
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• 2017

In this paper, we study an extended warranty model under minimal repair-replacement warranty (MRRW) which is suggested by Park, Jung and Park (2013). Under MRRW policy, the manufacturer is responsible for providing the minimal repair-replacement services upon the system failures during the warranty period. And if the failure occurs during the extended warranty period, only the minimal repair is conducted. Following the expiration of extended warranty, the user is solely responsible for maintaining the system for a fixed length of time period and replaces the system at the end of such a maintenance period. During the maintenance period, only the minimally repair is given for each system failure. The main purpose of this article is to suggest the extended warranty and replacement model with MRRW. Given the cost structures incurred during the life cycle of the system, we formulate the expected cost and the expected length of life cycle to obtain the expected cost rate.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권2호
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• pp.57-66
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• 2012

In this paper, we consider the periodic preventive maintenance model for a repairable system following the expiration of replacement-repair warranty. Under this preventive maintenance model, we derive the expressions for the expected cycle length, the expected total cost and the expected cost rate per unit time. Also, we determine the optimal preventive maintenance period and the optimal preventive maintenance number by minimizing the expected cost rate per unit time. Finally, the optimal periodic preventive maintenance policy is given for Weibull distribution case.

• 한국건축시공학회지
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• 제10권2호
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• pp.41-50
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• 2010

본 연구에서는 수선교체이력 자료 및 전문가 의견을 기초데이터로 하고 몬테카를로 시뮬레이션을 활용하여 건축물 수선교체주기에 대한 신뢰성 분석을 가능하게 할 수 있는 모델을 제시하였다. 제시된 모델은 건축물의 경년별 수선교체 시기를 확률적으로 제시하고 건물의 유지관리 계획시 신뢰성분석에 근거한 수선교체시기와 비용수요를 사전에 예측하도록 지원한다. 또한 건물의 소유주체나 유지관리 의사결정권자에게 공통적으로 발생하는 계획상의 많은 리스크를 감소시켜주는 역할을 할 것이다. 더불어 기존건물의 수선교체 이력데이터의 부재로 인해 의사결정에 많은 어려움 겪고 있는 대규모 건물자산의 유지관리책임자가 수선교체소요에 대한 중장기정책 수립시 이에 대한 타당성을 확보할 수 있는 공학적 해법이 제시되었다. 정리하면 크게 다음과 같이 3가지의 연구성과로 나눌 수 있다 첫째, 건축시스템의 발달에 대응할 수 있는 수선교체주기 산정법이 개발되었다. 둘째, 수선교체주기의 리스크를 정량화 시킬 수 있는 확률론적 방법론이 제안되었다. 셋째, 제안된 모델은 건축프로젝트에서 설계자와 시공자가 건물의 생애주기설계에 관한 의사결정을 지원할 수 있는 도구로 활용 가능할 것이다.