• 대한안전경영과학회지
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• 제3권4호
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• pp.91-101
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• 2001

This paper is to develop replacement models under minimal repair with exponential polynomial wavelet failure rate function. Wavelets have good time-frequency localization, fast algorithms and parsimonious representation. Also this study is presented along with numerical examples using sensitivity analysis for exponential polynomial trigonometric failure rate function.

• 호남수학학술지
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• 제23권1호
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• pp.145-158
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• 2001

In this paper we investigated a replacement model with two types of repairs. Repairs are classified into minimal and perfect repair. An operating unit is completely replaced whenever it reaches age ${\tau}({\tau}>0)$(planned replacement). If it fails at age $t<{\tau}$, it is either restored by a entire unit with probability p(t)(perfect repair), or it undergoes minimal repair with probability $\bar{p}(t)=1-p(t)$. After a planned replacement, the procedure is repeated.

• 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.

• 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.

• 대한족부족관절학회지
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• 제22권2호
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• pp.68-73
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• 2018

Purpose: This study compared the clinical outcomes of open repair, percutaneous repair, and minimal incision repair by Achillon in ruptured Achilles tendon. Materials and Methods: The outcomes of 12 patients with open repair (group 1), 8 patients with percutaneous repair (group 2), and 10 patients with minimal incision repair by Achillon (group 3) from February 2013 to March 2016 were analyzed retrospectively. The postoperative clinical evaluations were done by the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, Arner-Linholm scale, mid-calf circumference difference, one-leg heel raise difference, visual analogue scale (VAS) for postoperative scarring, time to return to work, and complications. Results: No significant difference in the AOFAS ankle-hindfoot score, Arner-Linholm scale, and time to return to work was observed among three groups (p=0.968, 0.509, and 0.585). The mean differences in the mid-calf circumference in groups 1, 2, and 3 were 1.09, 0.73, and 0.58, respectively; groups 2 and 3 were significantly higher than group 1 (p=0.002). In addition, the mean VAS scores for postoperative scarring in groups 1, 2, and 3 were 7.0, 9.1, and 9.1, respectively; groups 2 and 3 were significantly higher than group 1 (p=0.001). The mean differences in one-leg heel raising in groups 1, 2, and 3 were 2.03, 1.91, and 1.33, respectively; group 3 was significantly higher than groups 1 and 2 (p=0.010). The complications encountered were one case of deep infection in group 1 and one case of sural nerve hypoesthesia in group 2. Conclusion: Minimal incision repair by Achillon is recommended as an effective surgical treatment for Achilles tendon rupture because it minimizes the risk of complications, leads to an improved tendon strength and healing, and achieves cosmetic satisfaction.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권4호
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• pp.409-417
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• 2011

In this paper, we consider a replacement model following the expiration of warranty. In other words, this paper proposes the optimal replacement policy for a repairable system following the expiration of payable renewing replacement-non-renewing minimal repair warranty. The expected cost rate per unit time from the user's perspective is used to determine the optimality of the replacement policy. Thus, we derive the expressions for the expected cycle length and the expected total cost to obtain the expected cost rate per unit time. Finally, the numerical examples are presented for illustrative purpose.

• Journal of the Korean Data and Information Science Society
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• 제8권1호
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• pp.85-89
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• 1997

In this paper, we consider a random replacement model with minimal repair, which is a generalization of the random replacement model introduced Lee and Lee(1994). It is assumed that a system is minimally repaired when it fails and replaced only when the accumulated operating time of the system exceeds a threshold time by a supervisor who arrives at the system for inspection according to Poisson process. Assigning the corresponding cost to the system, we obtain the expected long-run average cost per unit time and find the optimum values of the threshold time and the supervisor's inspection rate which minimize the average cost.

• Journal of the Korean Data and Information Science Society
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• 제23권6호
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• pp.1195-1202
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• 2012

본 논문에서는 최소수리의 비용이 시스템의 수명시간에 의존하는 경우에 연장된 보증이 주어진 수리가 가능한 시스템에 대하여 사용자 측면에서의 총기대비용을 구하였다. 이를 위해서 연장된 보증을 정의하고 사용자 측면에서 연장된 보증이 종료된 이후의 교체모형을 가정하였다. 특히, 시스템의 교체모형에서 사용자가 연장된 보증을 선택하기 위한 기준을 제시하였으며, 시스템의 고장시간이 와이블 분포를 따를 때 수치적 예를 통하여 이를 설명하였다.

• 한국국방경영분석학회지
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• 제25권2호
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• pp.144-157
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• 1999

In this paper, we consider a new preventive replacement policy for the system which deteriorates while it is in operation with an increasing failure rate. The system is subject to two types of failure. A type 1 failure is repairable while a type 2 failure is not repairable. In the new policy, a system is replaced at the age of $t_p$ or at the instant the$\textsc{k}^{th}$ type 1 failure occurs, whichever comes first. However, if a type 2 failure occurs before a preventive replacement is performed, a failure replacement should be made. We assume that a type 1 failure can be rectified with a minimal repair. We also assume that a replacement takes a non-negligible amount of time while a minimal repair takes a negligible amount of time. Under a cost structure which includes a preventive replacement cost, a failure replacement cost and a minimal repair cost, we develop a model to find the optimal ($\textsc{k},t_p$) policy which minimizes the expected cost per unit time in the long run while satisfying a system availability constraint.

• 한국신뢰성학회지:신뢰성응용연구
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• 제13권2호
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• pp.77-86
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• 2013

Recently, an extended warranty of a system following the expiration of the basic warranty is becoming increasingly popular to the user. In this respect, we suggest a replacement model following the expiration of extended warranty with minimal repair warranty from the user's point of view in this paper. Under extended warranty, the failed system is minimally repaired by the manufacturer at no cost to the user during the original extended warranty period. As a criterion of the optimality, we utilize the expected cost rate per unit time during the life cycle from the user's perspective and suggest the optimal replacement period after extended warranty. Finally, a few numerical examples are given for illustrative purpose.