• 한국경영과학회지
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• 제14권2호
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• pp.75-86
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• 1989

Joint stocking and preventive age replacement policy is considered for non-repairable items assuming instantaneous replenishment. A recursive relationship among the optimal preventive replacement ages is obtained, which shows that the preventive replacement ages in a replenishment cycle form an increasing sequence due to the inventory carrying cost. Using this relationship, a procedure is given for determining how many units to purchase on each order and when to replace each unit after it has begun operating so as to minimize the total cost per unit time over an infinite time span. The problem can be simplified if equal preventive replacement ages are assumed, and the solution is very close to that of the original unconstrained problem.

• 품질경영학회지
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• 제40권1호
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• pp.88-91
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• 2012

Joint optimization of preventive age replacement and inventory policy is considered in this paper. There are three decision variables in the problem: (i) preventive replacement age of the operating unit, (ii) order quantity per order and (iii) reorder point for spare replenishment. Preventive replacement age and order quantity are jointly determined so as to minimize the expected cost rate, and then the reorder point for meeting a desired service level is found. A numerical example is included to explain the joint optimization model.

• 품질경영학회지
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• 제39권4호
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• pp.480-485
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• 2011

This paper presents a spare ordering policy for preventive replacement with minimal repair. To analyze the ordering policy, the failure process is modeled by a non-homogeneous Poisson process. Introducing the ordering, repair, downtime, replacement costs and salvage value, we derive the expected cost effectiveness as a criterion of optimality when the lifetime and lead times for the regular and expedited orders are generally distributed random variables. It is shown that, under certain conditions, there exists a finite and unique optimum ordering time which maximizes the expected cost effectiveness. A numerical example is also included to explain the proposed model.

• Journal of the Korean Data and Information Science Society
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• 제22권4호
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• pp.775-784
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• 2011

본 논문에서는 비재생무료교체-수리보증이 종료된 이후의 수리가 가능한 시스템에 대한 주기적인 예방보전모형을 고려한다. 이러한 예방보전모형에 대하여 기대순환길이, 총기대비용 그리고 단위시간당 기대비용을 각각 유도하고자 한다. 또한 유도된 단위시간당 기대비용을 최소화하는 최적의 예방 보전주기와 예방보전횟수를 결정하는 방법에 대하여 자세히 설명한다. 끝으로 고장시간이 와이블분포를 따르는 경우에 최적의 주기적 예방보전정책을 결정하여 본다.

• 전기학회논문지
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• 제66권8호
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• pp.1278-1284
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• 2017

As of December 2016, there are 608,828 elevators in operation in Korea and 179,790 elevators in more than 15 years. 30.4% of all elevator are aging. Improved maintenance of the elevator and proactive replacement of the parts of the elevator can extend the lifetime of the elevator and ensure safety. An unclean environment reduces the lifetime of elevator parts. If you do not clean the environment and prevent preventive parts replacement, eventually shortening the lifetime of the parts connected to the failed part or causing more damage will result in greater economic loss. Also, the risk of elevator safety accidents due to failures of elevator parts will be increased accordingly. The study of optimum replacement time of elevator parts will contribute to prevention of safety accident of elevator and prolongation of lifetime of elevator through preventive replacement of elevator parts.

• 한국국방경영분석학회지
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• 제10권2호
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• pp.61-73
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• 1984

A block replacement policy using items with different reliability is discussed. We divide system unit failure modes into two modes and use less reliable unit when operating unit fails near the planned preventive replacement time. In this policy, item A has two failure modes. Mode-1 failure is removed by minimal repair, mode-2 failure by replacement. If mode-2 failure of item A happens in (0, $T-{\delta}$), failure item A is replaced by new item A. If mode-2 failure of item A happens in ($T-{\delta}$, T), failure item A is replaced by new item B. Item B should be cheaper and less durable than item A. Under this policy, we determine the preventive replacement interval $T^{*}$ and the interval ${\delta}^{*}$ of item B replacement which minimize the cost rate per unit time.

• 품질경영학회지
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• 제28권3호
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• pp.11-17
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• 2000

This paper presents a model for determining the optimal number of general repairs and supplementary input cost limit rate in addition to minimal repair cost rate to implement preventive maintenance. The basic concept parallels the periodic replacement model with minimal repair at failure introduced by Barlow and Hunter(1960) and Park(1979), only difference being the replacement signalled by the number of previous general repairs performed on the system. A general repair brings the state of the system to a certain better state than before repaired. Numerical examples are provided.

• ETRI Journal
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• 제6권3호
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• pp.17-20
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• 1984

A block replacement policy using items with different reliability is discussed. We devide system unit failure modes into two modes and use less reliable unit when operating unit fails near the planned preventive replacement time. In this policy, item A has two failure modes. Mode-1 failure is removed by minimal repair, mode-2 failure by replacement. If mode-2 failure of item A happens in (0,T- $\delta$). failure item A is replaced by new item A. If mode-2 failure of item A happens in(T-$\delta$,T), failure item A is replaced by new item B. Item B should be cheaper and less durable than item A. Under this policy, we determine the preventive replacement interval T and the interval $\delta$ of item B replacement which minimize the cost rate per unit time.

• 한국안전학회지
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• 제38권2호
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• pp.104-111
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• 2023

Rolling stock maintenance, which focuses on preventive maintenance, is typically implemented considering the potential harm that may be inflicted to passengers in the event of failure. The cost of preventive maintenance throughout the life cycle of a rolling stock is 60%-75% of the initial purchase cost. Therefore, ensuring stability and reducing maintenance costs are essential in terms of economy. In particular, private railroad operators must reduce government support budget by effectively utilizing railroad resources and reducing maintenance costs. Accordingly, this study analyzes the reliability characteristics of components using field data. Moreover, it resolves the problem of determining an economical replacement interval considering the timing of scrapping railroad vehicles. The procedure for determining the optimal replacement interval involves five steps. According to the decision model, the optimal replacement interval for the onboard signal device components of the "A" line train is calculated using field data, such as failure data, preventive maintenance cost, and failure maintenance cost. The field data analysis indicates that the mileage meter is 9 years, which is less than the designed durability of 15 years. Furthermore, a life cycle in which the phase signal has few failures is found to be the same as the actual durability of 15 years.

• 조명전기설비학회논문지
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• 제28권7호
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• pp.34-40
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• 2014

In this paper, we want to know the optimal replacement cycle(time) for this study was performed. The optimal preventive replacement age can be fond by finding the value of time that minimizes the cost function(model of Barlow and Jardine). In addition, The reliability of the relay according to the service environment were studied. The use of the exchange relay period is longer, and maintenance cost rate(per hour) may increase, and also the reliability may cause a decline. In addition, considering the preventive maintenance and purchase order, a representative relay(RAX-L440-A type) life was calculated.