• Journal of the Korean Statistical Society
• /
• 제11권2호
• /
• pp.77-87
• /
• 1982

The choice if constants that define a life testing procedure is considered in terms of the test termination time (censoring time) and the number of items to be tested subject to a given range of variance of the expected life time, where the failure time of life testing is exponentially distributed.

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

• Journal of the Korean Data and Information Science Society
• /
• 제21권1호
• /
• pp.71-86
• /
• 2010

생명보험의 보험료는 보험가입자들의 예정 수명분포와 예정 이자율에 기초하여 산출되게 된다. 산출된 보험료는 향후 해당 보험을 운영하는 과정에서 발생할 수 있는 보험회사나 보험가입자들의 손실 그리고 이들이 부담하는 리스크에 직접적인 영향을 미치게 된다. 따라서 생명 보험에서 이들 두 가지 요소, 즉 예정 수명분포와 예정 이자율은 중요한 영향 변수로 여겨진다. 본 논문에서는 종신보험에서 이들 영향 변수가 보험료, 보험 운영상의 리스크, 보험운영에 있어서의 손실 확률에 미치는 영향력을 분석하고 상대적인 영향력의 크기를 비교해 보고자 한다.

• Communications for Statistical Applications and Methods
• /
• 제24권1호
• /
• pp.29-41
• /
• 2017

The estimation problem of expected time to failure of units is studied in a discrete set up. A simple step-stress accelerated life testing is considered with a Type-I censored sample from geometric distribution that is a commonly used distribution to model the lifetime of a device in discrete case. Maximum likelihood estimators as well as the associated distributions are derived. Exact, approximate and bootstrap approaches construct confidence intervals that are compared via a simulation study. Optimal confidence intervals are suggested in view of the expected width and coverage probability criteria. An illustrative example is also presented to explain the results of the paper. Finally, some conclusions are stated.

• 지역연구
• /
• 제35권2호
• /
• pp.59-71
• /
• 2019

우리나라 연평균 근로시간은 OECD 최상위 수준이다. 장시간 근로는 근로자의 생산성을 저해하고 일과 가정의 양립을 방해하는 등 삶의 질을 하락시키는 요인이 된다. 최근 정부는 시간제 일자리를 증가하는 등 유연근로제를 장려하고 있지만, 양질의 시간제 일자리가 부족한 현실이다. 시간제 근로는 일과 개인의 삶을 병행할 수 있게 하지만, 동시에 열악한 근로환경과 부정적인 사회적 시선을 보유하여 개인의 삶의 만족도에 미치는 영향이 전일제 근로와는 다를 것으로 예상된다. 특히 여성의 경우 노동시장에서 성별 격차를 경험하고 있으며, 일과 가정의 병행이라는 측면에서 시간제 근로가 삶의 만족도에 미치는 영향이 남성과 다르게 나타날 수 있다. 본 연구는 2017년도 "서울서베이 도시정책지표조사" 자료를 활용하여 근무유형-성별의 교차효과가 개인의 삶의 만족도에 미치는 영향을 순서형 로지스틱 회귀모형을 통해 실증적으로 분석하였다. 분석결과에 따르면, 삶의 만족도는 전일제 여성, 전일제 남성, 시간제 여성, 시간제 남성 순으로 높은 것으로 나타났다. 또한 시간제 여성 근로자가 낮은 삶의 만족도를 가질 확률이 가장 높은 반면, 높은 삶의 만족도를 가질 확률은 가장 낮게 나타났다. 대조적으로 전일제 남성 근로자는 낮은 삶의 만족도를 가질 확률이 가장 낮은 반면, 높은 삶의 만족도를 가질 확률은 가장 높은 것으로 나타났다.

• 한국경영과학회:학술대회논문집
• /
• 대한산업공학회/한국경영과학회 1994년도 춘계공동학술대회논문집; 창원대학교; 08월 09일 Apr. 1994
• /
• pp.78-78
• /
• 1994

• 응용통계연구
• /
• 제23권3호
• /
• pp.573-584
• /
• 2010

This paper considers the differences in the software execution environments in the testing phase and the operational phase to determine the optimal release time and warranty period of software systems. We formulate equations for the total expected software cost until the end of the software life cycle based on the NHPP. In addition, we derive the optimal release time that minimizes the total expected software cost for an imperfect debugging software reliability model. Finally, we analyze the sensitivity of the optimal testing and maintenance design related to variation of the cost model parameters based on the fault data observed in the actual testing process, and discuss the quantitative properties of the proposed model.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회 1996년도 추계학술대회발표논문집; 고려대학교, 서울; 26 Oct. 1996
• /
• pp.103-112
• /
• 1996

Optimal pricing research in general has been focused on profit maximizing strategy under the given product life-time T. Here we have tried to study the effect of uncertain product life-time on dynamic optimal pricing strategy. In reality, the life-time of product is more likely to be uncertain and not known as well. In terms of approximating the model to the concerned reality, so-called model validity, it seems to be more desirable to consider the uncertainty of product life-time into the optimal pricing strategy model, For this purpose, we tried two different approaches. One is to consider diverse product life-time probability functions under fixed life-time T. In this case, we might have the same product life-time as the previous study, but the process could be different in the expectation of product's discontinuity. The other is that life-time itself is not determined and thus it is the situation in which we can only decide optimal price on incremental basis. The former is the situation in which although we got some strong guess on life-time of a certain product, the pattern of expected life-time probability could be different. The question is what could be optimal pricing strategies on such different product life-time situations. But since in the latter, we don't assume any idea on the life-time of product. proper optimal pricing could be derived only from the past prices and diffusion information. While the latter seems to be safer in the aspect of model assumption, the former could be more realistic because we might have more or less a prior knowledge on the product life-time itself.

• International Journal of Reliability and Applications
• /
• 제18권1호
• /
• pp.1-8
• /
• 2017

In this paper, we study an extended warranty model under minimal repair-replacement warranty (MRRW) which is suggested by Park, Jung and Park (2013). Under MRRW policy, the manufacturer is responsible for providing the minimal repair-replacement services upon the system failures during the warranty period. And if the failure occurs during the extended warranty period, only the minimal repair is conducted. Following the expiration of extended warranty, the user is solely responsible for maintaining the system for a fixed length of time period and replaces the system at the end of such a maintenance period. During the maintenance period, only the minimally repair is given for each system failure. The main purpose of this article is to suggest the extended warranty and replacement model with MRRW. Given the cost structures incurred during the life cycle of the system, we formulate the expected cost and the expected length of life cycle to obtain the expected cost rate.

• 품질경영학회지
• /
• 제21권1호
• /
• pp.108-120
• /
• 1993

In this article an economic life test sampling plan is considered for repairable products when the products in each lot have the same interfailure time distribution, but the mean time between failure (MTBF) of a lot varies from lot to lot according to a known prior distribution. A cost model is constructed which consists of test cost, accept cost, and reject cost. Determination of the optimal plan which minimizes the expected average cost per lot is discussed. Numerical examples are presented to illustrate the use of the proposed sampling plans and sensitivity analyses for parameters of the prior distribution are performed.