• Communications for Statistical Applications and Methods
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• v.10 no.1
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• pp.191-202
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• 2003

Availability is an important measure of performance of a repairable component. In this paper, the explicit expression for the availability of a repairable component, which is subject to the policy II(Age Replacement Policy) of Barlow and Hunter (1960), is obtained and the existence of the steady state availability is shown. The steady state availabilities of the model are also obtained for the cases when the mean of the minimal repair time is increasing at a geometric rate or linearly increasing, In order to show the importance and the utility of the obtained result, we also consider an illustrative example of the repairable coherent system whose components are repairable, and the obtained results are applied to derive the steady state availability of the whole system. In this situation, we can see that the condition of the existence of the steady state availability for each component is essential. Some remarks on the optimal replacement policy that maximizes the steady state availability are also given.

• Journal of the Korean Data and Information Science Society
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• v.17 no.3
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• pp.743-752
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• 2006

This paper considers a Bayesian approach to replacement policy model with minimal repair. We use the criterion based on the expected cost and the expected downtime to determine the optimal replacement period. To do so, we obtain the expected cost rate per unit time and the expected downtime per unit time, respectively. When the failure time is Weibull distribution with uncertain parameters, a Bayesian approach is established to formally express and update the uncertain parameters for determining an optimal maintenance policy. Especially, the overall value function suggested by Jiagn and Ji(2002) is applied to obtain the optimal replacement period. The numerical examples are presented for illustrative purpose.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.4
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• pp.507-517
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• 1995

The failure rate of an item depends on operational environment. When an item has a chance failure period and a wearout failure period in sequel, the severity of operational environment causes the increase in the slop of wearout failure rate or the increase in the magnitude of chance failure rate. For such a change of operational environment, this paper concerns the change of optimal preventive replacement time. Two preventive replacement policies, age replacement policy and periodic replacement policy with minimal repair, are considered. Investigated properties are: (a) in age replacement policy, optimal preventive replacement time increases as the chance failure rate increases and optimal preventive replacement time decreases as the slope of wearout failure rate increases, and (b) in periodic replacement policy with minimal repair, optimal preventive replacement time increases as the slope of wearout failure rate increases; however, the change of chance failure rate does not alter the optimal preventive replacement time.

• Journal of Integrative Natural Science
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• v.14 no.4
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• pp.197-204
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• 2021

Under the two-phase warranty, the warranty period is divided into two intervals, one of which is for renewing replacement warranty, and the other is for minimal repair warranty. Jung^[13] discusses the two types of extended two-phase warranty models. In this paper, we suggest the replacement model after the extended two-phase warranty that has been proposed by Jung^[13]. To determine the optimal replacement policy, we adopt the expected cost rate per unit time. So, the expressions for the total expected cost, the expected length of the cycle and the expected cost rate per unit time from the user's point of view are derived. Also, we discuss the optimal replacement policy and the uniqueness of the solution for the optimization. Furthermore, the numerical examples are provided to illustrate the proposed the replacement model.

• Journal of Integrative Natural Science
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• v.17 no.2
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• pp.43-51
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• 2024

Jung et al.(2015) suggest the two-phase warranty model, which is a general type of warranty model. Under the two-phase warranty, the warranty period is divided into two intervals, one of which is for renewing replacement warranty, and the other is for minimal repair warranty. And warranty policies play a very important role in product marketing. In this paper, we suggest the optimal warranty policy for free extended two-phase warranty. To determine the optimal warranty period, we adopt the expected profit per unit product. So, the expressions for the total expected cost, the sale price and the expected profit per unit product from the manufacturer's point of view are derived. Also, we discuss the optimal warranty period and the numerical examples are provided to illustrate the proposed the warranty policy.

• Journal of Chest Surgery
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• v.31 no.6
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• pp.576-580
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• 1998

This study is to clarify the results of atrial septal defect(ASD) repair and mitral valve surgery through right anterolateral thoracotomy since 1989, and those of more generalized application of minimal invasive cardiac surgery since August 1997. We retrospectively analyzed the results of open heart surgery(OHS) through other than full sternotomy carried out until October 1997. There were 28 cases of OHS done through right anterolateral thoracotomy(17 cases of ASD, 4 cases of mitral valve repair, 6 cases of mitral valve replacement, and 1 redo mitral and tricuspid valve repalcement) which has demonstrated no surgical mortality or morbidity except only 1 case of reoperation for bleeding. During the period between August and October 1997, we performed near routine application of upper sternotomy or transverse sternotomy in aortic valve cases and routine application of minimal incision in cases with ASD and there was no evidence of early and late complications associated with this approach. We conclude that OHS with the use of minimal incisions is very safe, cosmetically excellent, and superior in terms of the amount of bleeding. The indication for minimal incision, therefore, should be extended afterwards.

• Journal of Korean Society for Quality Management
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• v.31 no.3
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• pp.193-204
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• 2003

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate but remains the pattern of hazard rate unchanged. And the system undergoes only minimal repairs at failures between PM's. The expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.

• Journal of Korean Institute of Industrial Engineers
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• v.13 no.2
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• pp.59-63
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• 1987

An age replacement policy is considered for a system under a stepdown warranty. It is assumed that only minimal repairs are performed for failures occurred before age T.A unique optimal value of T which minimiges the expected cost rate is obtained. The cases of the free replacement warranty, prorata warranty and hybrid warranty are also considered and some numerical examples are given.

• Journal of Chest Surgery
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• v.24 no.9
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• pp.913-917
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• 1991

Ventricular septal defect complicating myocardial infarction is rare but fatal condition which requires early surgical intervention before end-organ failure ensues from cardiogenic shock. Since the first successful repair by Cooley et al in 1956, surgical skills and strategies were developed and modified to a great extent, and we adopted the new repair technique in our case which stresses that minimal or no part of the infarcted septum and left ventricular wall be resected. This technique obviates the need to resect the infarcted part of the septum and prevents recurrence of an even larger VSD, and provides adequate size and shape of the left ventricle after of transinfarction left ventriculotomy.

• Journal of Applied Reliability
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• v.10 no.4
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• pp.251-263
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• 2010

Modelling for failures is important for reliability analysis since failures of products such as automobiles occur as both time and usage progress and the results from the proper analysis of the two-dimensional data can be used for establishing warranty assurance policy. Hence, in this paper general issues which concern modelling failures are discussed, and both one-dimensional approaches and two-dimensional approaches to two-dimensional data are investigated. Finally non-parametric approaches to two-dimensional data are presented as a means of exploratory data analyses.