• 대한산업공학회지
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• 제39권4호
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• pp.233-238
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• 2013

This article concerns a profit model in a repair limit replacement problem with imperfect repair. If a system fails, we should decide whether we repair the failed system (repair option) or replace it by new one (replacement option with a lead time). We assume that repair times are random variables and can be estimated before repair with estimation error. If the estimated repair time is less than the specified limit (repair time limit), the failed unit is repaired but the unit after repair is different from the new one (imperfect repair). Otherwise, we order a new unit to replace the failed unit. The long run average profit (expected profit rate) is used as an optimization criterion and the optimal repair time limit maximizes the expected profit rate. Some special cases are derived.

• 교육녹색환경연구
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• 제9권2호
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• pp.1-8
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• 2010

This study is to present an engineering solution for the repair frequency and repair rates of a building. The existing data for the repair frequency and repair rates are used to draw the probability distribution for the generalized repair frequency and repair rate in a building. The suggested methodology can be widely used for most buildings to estimate the legal repair frequency and repair rates. Also, the methodology can be applied to resolve the risks on the maintenance costs in LC (Life Cycle) plans or LCC (Life Cycle Cost) analysis. As the future studies, there are the multiple regression analysis including the parameters on incurred costs and the decision methods on efficient repair and replacement.

• 교육녹색환경연구
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• 제6권1호
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• pp.60-84
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• 2007

This study purpose is seeing that the independent standard sufficiently reflecting the characteristics of the school facility as the basic material needed to calculate the maintenance and repair expenses is needed to make a more realistic and valid qualitative VFM analysis of the school BTL project. this study attempted to develop the standard for the repair cycle and rate and economic year of the school facility. The quantitative VFM analysis should be conducted based on the repair cycle and repair rate proper to the school facility, not the residential space, when calculating the maintenance and repair expenses of the operating expenses of the school facility. An attempt was made to calculate the repair cycle, repair rate and economic life of 114 component materials of the school facility judged to be able to explain the school field best. And it was confirmed that the repair and maintenance expenses more is needed to be set by about 35% than the existing maintenance and repair expenses.

• International Journal of Reliability and Applications
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• 제18권1호
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• pp.9-20
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• 2017

In this paper, we consider a renewable repair-replacement warranty strategy with age-dependent minimal repair service and propose an optimal maintenance model during post-warranty period. Such model implements the repair time limit under warranty and follows with a certain form of system maintenance strategy when the warranty expires. The expected cost rate is investigated per unit time during the life period of the system as for the standard for optimality. Based on the cost design defined for each failure of the system, the expected cost rate is derived during the life period of the system, considering that a renewable minimal repair-replacement warranty strategy with the repair time limit is provided to the customer under warranty. When the warranty is finished, the maintenance of the system is the customer's responsibility. The life period of the system is defined and the expected cost rate is developed from the viewpoint of the customer's perspective. We obtain the optimal maintenance strategy during the maintenance period by minimizing such a cost rate after a warranty expires. Numerical examples using field data are shown to exemplify the application of the methodologies proposed in this paper.

• 전기학회논문지
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• 제58권11호
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• pp.2122-2127
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• 2009

This study presents the failure rate and repair rate of Superconducting Fault Current Limiter(SFCL) and adjacent distribution equipments. When the fault current penetrated SFCL, the supply of electric power to the customers can be partly continued. It is expected that SFCL makes to improve the reliability index of customers. Contrary to the expectations, the series connection between SFCL and distribution system could deteriorate the reliability index. To evaluate the reliability index in the distribution system including SFCL, the failure rate and repair rate of SFCL are required as well as that of distribution equipments. Also, the insertion of SFCL makes to change the failure rate and repair rate of adjacent equipments. This study proposes a method to calculate the failure rate and repair rate of a component combining SFCL and adjacent equipments.

• 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.

• 대한소아치과학회지
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• 제45권3호
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• pp.370-377
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• 2018

이번 연구의 목적은 12세 이하의 아동의 제1대구치 복합레진 수복물에 관하여 후향적 연구를 하여 재수복률을 평가하고자 함에 있다. 이번 연구는 2014년 5월부터 2015년 4월까지 경희대학교 치과병원 소아치과를 내원하여, 제1대구치에 복합레진 수복을 진행한 12세 이하의 환자 169명의 재수복률과 그 원인을 분석하였다. 재수복률은 성별에 따라 통계적으로 유의한 차이는 보이지 않았다. 제1대구치의 위치에 따라서 상악보다는 하악이 그리고 우측보다는 좌측에서 재수복률이 높았다. 와동의 종류에 따라서 2급 와동에서 가장 재수복률이 높았고, 교합면만 수복한 경우 재수복률이 가장 낮았다. 2년간의 재수복률은 14.8%로 나타났으며, 연령이 증가함에 따라 재수복의 위험도는 감소하였다. 재수복의 가장 주된 원인은 이차우식(74.1%)이었다. 아동의 영구치 복합레진 수복물의 재수복률은 성인 보다 높은 것으로 나타났으며, 영구치의 맹출도, 환자의 협조도 및 구강위생 관리능력이 중요한 영향을 미치는 것으로 사료되었다.

• 대한족부족관절학회지
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• 제16권3호
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• pp.181-189
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• 2012

Purpose: The purpose of this study was to compare and analyse the clinical outcomes of minimal incision repair and open repair in ruptured Achilles tendon. Materials and Methods: We retrospectively analyzed the outcomes of 10 patients with minimal incision repair (group 1) and 19 patients with open repair (group 2) from February 2007 to June 2011. The postoperative clinical evaluations were done by Arner-Lindholm scale, AOFAS score, overall patient's satisfaction and cosmetic satisfaction of scar. Results: There was no statistical difference between two groups in Arner-Lindholm scale, AOFAS score, overall patient's satisfaction (p=1.21, 0.87, 1.07). There was statistically high rate of cosmetic satisfaction in group 1(p<0.001). There were no complications in group 1. Complications occurred in three patients (deep infection, rerupture, deep vein thrombosis) of group 2. Conclusion: Treatment of minimal incision repair in Achilles's tendon ruptures showed high rate of cosmetic satisfaction and low rate of complication's, but there were no significant differences with open repair in other clinical outcomes. The minimal incision repair could be recommended as one of the effective treatment for the Achilles's tendon ruptures.

• 대한안전경영과학회지
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• 제16권1호
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• pp.139-146
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• 2014

As Crosby notes, the most companies spend 15 to 20% of their sales dollars on quality costs. Generally the most effective way to manage quality costs is to avoid having defects in the first place. In this paper we have studied about the repair(service) problem of domestic gas boiler within warranty period. We develop a system, which man could find the cause of the problem at an early stage and could devise a countermove to the problem under supposing that the service(repair) rate follows exponential distribution and the product is manufactured lot-for-lot continually. Using the developed early sensing system. it is expected to improve the reliability of the product, to save expenses of company and to improve customer's satisfaction. And the system will be expended to incorporate information technology, which can detect the repair rate automatically.

• 한국구조물진단유지관리공학회 논문집
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• 제6권1호
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• pp.205-212
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• 2002

The deterioration rate of concrete structures in urban area is accelerated due to rapid urbanization and environmental pollution. Repair materials and methods newly introduced in Korea should be investigated whether they are appropriate for the urban environment in Korea. The creek concrete structures are exposed in severe environmental condition than others. Based on these background in mind, the study is focused on evaluation of performance on repair materials used to rehabilitate creek concrete structures. To evaluate the performance of repair materials, four kinds of repair materials were selected based on polymer emulsion. This experimental study was conducted on fundamental performance such as setting time, compressive strength, bending strength, bonding strength, thermal expansion coefficient, and durability performance such as chloride diffusion, carbonation, chemical attack, and steel corrosion rate. On the basis of this study, the optimal repair material which is proper to the environment condition can be selected and service life of creek concrete structures can be extended. As a result, the life cycle cost can be reduced and the waste of material resources will be cut down.