• The Korean Journal of Applied Statistics
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• v.15 no.1
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• pp.107-117
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• 2002

In this paper we present the optimal replacement policies following the expiration of combination warranty. We consider two types of combination warranty policies: renewing warranty and non-renewing warranty. The criterion used to determine the optimal replacement period is the expected cost rate per unit time from the user'perspective. The optimal maintenance period following the expiration of combination warranty is obtained. Some numerical examples are presented for illustrative purpose.

• Proceedings of the Korean Statistical Society Conference
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• 2001.11a
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• pp.125-130
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• 2001

본 논문에서는 혼합보증기간이 있는 수리 가능한 시스템에 대한 최적의 교체정책을 제안한다. 이 교체정책은 보증기간이 재생되는 경우와 재생되지 않는 두 가지 경우에 대해서 고려되며, 최적의 교체주기를 결정하기 위해서 사용자 관점에서의 단위 시간당 기대비용을 사용한다. 시스템의 고장시간이 와이블 분포를 할 때 수치적 예를 통해서 제안된 최적의 교체정책을 설명한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6B
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• pp.623-629
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• 2009

In this research, the process of developing software products to users in transfer by considering the warranty period to determine the timing of the release period is a comparative study of models. For the results of demonstration, exponential software reliability model increases the warranty period, the higher the initial period, but shows almost a similar release. In contrast, the optimal release time of imperfect debugging software reliability model, lower the initial warranty period, but the pattern is expected to rise slightly larger. The proposed model, extreme value distribution model, pattern of the optimal release time gradually increase, have a form that can be drawn. These research results through, warranty period and release the software developers understand the relationship between the optimal time for software development by using advance information could do is feed.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.65-73
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• 2011

Recently, researches to introduce the performance warranty contract are in progress for quality improvement of road pavements. The performance warranty contract is a type of contract in which contractors guarantee to maintain certain level of performance during a period from completion of construction. The contract use in Europe and the U.S is being increased because it has been known to contribute to improvement of structure quality, reduction of life cycle cost, development of construction techniques, and etc. The research on performance indicators, threshold values, and warranty durations is essential to effectively introduce the contract in Korea. In this study, literatures on the performance warranty contract for concrete pavements of the Minnesota, Indiana, and Florida of the U.S. were reviewed. Major distresses influencing the pavement performance were investigated and analyzed in the jointed concrete pavement sections of 21 Korean expressway routes to be compared to the performance indicators, threshold values, and warranty durations of the states. More accurate comparison is expected by investigation in planned sections for a long time.

• The Korean Journal of Applied Statistics
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• v.26 no.1
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• pp.151-162
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• 2013

Due to a growing demand for the second-hand product, especially for the expensive one, the warranty and maintenance policies for such products have been studied to improve the product reliability of late. In this paper we study a periodic maintenance model for the second-hand product which is purchased by the customer at the age of $x$. When purchased, the dealer provides a warranty of a fixed length during which the product is maintained periodically to reduce the failure rate of the product and thus, to improve the reliability after each maintenance is served. If a failure occurs between two successive maintenances, only minimal repair is conducted. As for the warranty policy, we adopt free non-renewing repair action on each failure, in addition to the periodic maintenance service during the warranty period. Thus, under the given warranty policy, all the maintenance and repair costs incurred during the warranty period are charged to the dealer. For the proposed periodic maintenance scheme, we formulate a cost model to evaluate the expected total cost charged to the dealer during the warranty period and derive an optimal upgrade level of the failure rate at each maintenance to minimize the expected total warranty cost from the perspective of the dealer. We also present numerical results for an optimal upgrade level based on the proposed methods.

• Communications for Statistical Applications and Methods
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• v.17 no.6
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• pp.865-877
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• 2010

This paper considers the periodic preventive maintenance model for a repairable system following warranty expiration. We consider three types of warranty policies: free repair warranty, pro-rata repair warranty, and combination repair warranty. Under these preventive maintenance models, we derive the expressions for the expected cycle length, the total expected cost, and the expected cost rate per unit time. In addition, we explain 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 a Weibull distribution case.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.3
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• pp.142-148
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• 2005

대부분의 일차원 보증정책에 대한 비용분석은 소비자 사용률이 모든 사용자들에게 동이란 것으로 가정하고 있다. 하지만 현실적으로 사용률은 소비자에 따라서 다르기 때문에, 일반적인 경우 소비자 집단을 ${\kappa}$ 범주로 나눌 수 있다. 즉, 동일한 제품에 대해서 생산자는 ${\kappa}$ 범주에 속하는 다른 보증정책을 제시할 수 있고, 보증비용은 이런 옵션들 가운데 소비자가 자기의 입장에 맞는 보증기간을 선택할 수 있다. 본 논문에서는 소비자의 사용률이 변화하는 경우를 고려한 무료보증정책을 갖는 기대보증비용 모형을 분석하고, 이에 따른 수치예제를 제시한다.

• Korean Journal of Construction Engineering and Management
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• v.19 no.4
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• pp.34-42
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• 2018

Apartment is a typical type of housing preferred by the majority of people. However, and defect disputes occur because various defects such as cracks, subsidence, breakage, water leakage, dew condensation and dropout are confirmed with numerous structures and finishing materials. From this point of view, this paper analyzes defect frequency and costs of each warranty period by work types, and estimates defect risks by using defect dispute cases. It examined about 5,337 defect items for 32 apartment over ten years old. In this paper, there are 10 types of work types and the warranty liability period is divided into 6 categories. Based on these categories, defect frequency and costs are investigated, and finally defect risk of the warranty liability period by work types confirmed. As a result of this analysis, it was found that defect risk in RC and finishing work is very high. Especially the RC work revealed that there is a high risk of trying from the third year onwards and it was found that the defect risk up to the second year is high in the finishing work. Due to aging of RC structure, the defect risk gradually increases, and finishing work initially cause defect disputes because of the housing environment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3D
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• pp.279-288
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• 2010

Recently, researches on the performance warranty contracting has been going on to improve construction quality in road pavement area. The performance warranty contracting gives construction companies opportunity to select materials and methods freely while asks them to maintain a certain level of performance during a given period. To introduce the performance warranty contracting in Korea, lots of research results on performance indicator and threshold value of asphalt pavement have been made to be included in the warranty specification. However, research effort on the performance indicator and threshold value of concrete pavement which is commonly constructed in expressway and national highway has not been enough. In this study, the warranty duration, performance indicator, and threshold value of the concrete pavement were investigated by reviewing literatures on cases of the performance warranty contracting in European countries and states of the US. Major distresses influencing the performance of jointed concrete pavement were investigated and analyzed to be compared to the warranty duration, performance indicator, and threshold value of foreign countries.

• Proceedings of the Korean Reliability Society Conference
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• 2006.05a
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• pp.76-81
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• 2006