• Communications for Statistical Applications and Methods
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• 제7권1호
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• pp.199-210
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• 2000

We shall propose several estimators for the shape and scale parameters I the Weibull distribution based upon the complete or truncated samples when both parameters are functions of a known exposure level and study properties for proposed several estimators

• 한국신뢰성학회지:신뢰성응용연구
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• 제3권2호
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• pp.137-143
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• 2003

Sequential test plans are characterized by decision rules for accepting or rejecting compliance, or continuing the test at my test time. They are determined by selected values of risks and discrimination ratio. The sequential test plans in the international standard such as MIL-HDBK-781A are based on the assumption that the underlying distribution of times between failures is exponential. In this paper, sequential test plans are extended to the Weibull distribution case. Simulation studies are performed to examine the reasonability in this extension.

• International Journal of Reliability and Applications
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• 제13권1호
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• pp.19-35
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• 2012

This paper presents an optimum design of step-stress partially accelerated life test (PALT) plan which allows the test condition to be changed from use to accelerated condition on the occurrence of fixed number of failures. Various life distribution models such as exponential, Weibull, log-logistic, Burr type-Xii, etc have been used in the literature to analyze the PALT data. The need of different life distribution models is necessitated as in the presence of a limited source of data as typically occurs with modern devices having high reliability, the use of correct life distribution model helps in preventing the choice of unnecessary and expensive planned replacements. Truncated distributions arise when sample selection is not possible in some sub-region of sample space. In this paper it is assumed that the lifetimes of the items follow Truncated Logistic distribution truncated at point zero since time to failure of an item cannot be negative. Optimum step-stress PALT plan that finds the optimal proportion of units failed at normal use condition is determined by using the D-optimality criterion. The method developed has been explained using a numerical example. Sensitivity analysis and comparative study have also been carried out.

• 충청수학회지
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• 제26권3호
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• pp.441-451
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• 2013

In this paper, we derive recurrence relations for moments of lower generalized order statistics within a class of doubly truncated distributions. Inverse Weibull, exponentiated Weibull, power function, exponentiated Pareto, exponentiated gamma, generalized exponential, exponentiated log-logistic, generalized inverse Weibull, extended type I generalized logistic, logistic and Gumble distributions are given as illustrative examples. Further, recurrence relations for moments of order statistics and lower record values are obtained as special cases of the lower generalized order statistics, also two theorems for characterizing the general form of distribution based on single moments of lower generalized order statistics are given.

• Communications for Statistical Applications and Methods
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• 제17권1호
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• pp.89-98
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• 2010

In this paper, a two-stage group sampling plan based on the time truncated life test is proposed for the Weibull distribution. The design parameters such as the number of groups and the acceptance number in each stage are determined by satisfying the producer's and consumer's risks simultaneously when the group size and the test duration are specified. The acceptable reliability level is expressed by the ratio of the true mean life to the specified life. It was demonstrated from the comparison with single-stage group sampling plans that the proposed plan can reduce the average sample number or improve the operating characteristics.

• Communications for Statistical Applications and Methods
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• 제17권3호
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• pp.319-326
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• 2010

In this paper, a new group sampling plan for the lot acceptance is proposed for the time truncated life test, which can be utilized when multi-item testers are implemented. The design parameters are found using the two-point approach such that the producer's and consumer's risks are satisfied simultaneously at the acceptable reliability level and the lot tolerance reliability level, respectively. The case of Weibull distribution is described to illustrate the procedure that can be used when the quality level is expressed by a multiple of the specified life. The advantage of the proposed plan is demonstrated by comparing with the existing plan in terms of the sample size required. The tables are constructed and some examples are given to illustrate the procedure developed here.

• 응용통계연구
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• 제32권1호
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• pp.129-138
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• 2019

무기체계의 구성요소 중 하나인 탄약은 전투력 발휘에서 필수적이다. 원활한 탄약의 공급과 전투력 발휘를 위하여 군은 탄약의 기본휴대량을 개인별 임무와 화기에따라 정하여 활용중이다. 탄약의 기본휴대량 산출에 핵심이 되는 탄약의 소요보급률은 부대의 작전환경과 임무등을 고려한 실제 전투 자료에 기반하여 산출이 되어져야한다. 한국전쟁의 자료를 통해 얻어진 기존의 소요보급률은 현대의 전투 양상을 반영하지 못한다는 한계가 있어, 본 연구에서는 실전과 가장 유사한 훈련인 육군 과학화 훈련단(Korea Combat Training Center; KCTC)의 소총 탄약 소모량 자료를 통하여 소총 탄약의 소요보급률을 추정하였다. KCTC 소총 소모량 자료가 중도 절단되었던 점을 고려하여 우측 중도절단된 와이블 분포를 추정하고 상위백분위수로 탄약의 소요보급률을 추정하였다. 그 결과 개인별 탄약 소모량을 반영하여 대부분의 전투원들이 추가 보급없이 전투를 수행할 수 있는 소요보급률을 추정할 수 있었다.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.544-555
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• 1998

Although the bimodal mixed weibull distribution is used to developing burn-in model widely, the failure times for a component or a system is often truncated at some time, T, due to the obsolescence in the electronics industry. In this paper, we will determine minimum total cost and burn-in time by using the bimodal mixed weibull distribution and the truncated bimodal mixed weibull distribution under the free warranty policy. The results of this study are summarized as follows. First, when products or system is not repairable, the width of the change of burn-in time can be larger by ${\beta}_1,\;{\beta}_2$ Second, if burn-in time become longer, it will be impossible to consider the bum-in in a long time, and in this case, the burn-in time should be shorten by the acceleration burn-in. Third, in case that opportunity loss cost or repair cost is exceed the warranty cost, or the total cost of considering burn-in is larger than that of not considering burn-in, it is not existed burn-in time which makes total cost to minimize. Forth, the shorter life-cycle of product, the more burn-in times will be decreased and the cost in considering burn-in will be increased

• 대한토목학회논문집
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• 제14권3호
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• pp.509-521
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• 1994

본 연구는 간헐 수문과정인 일 강수계열의 모의발생 모델을 개발한 것으로서, 일 강수계열의 구조적 특성인 강수발생과정과 습윤일의 강수량과정을 고려하였다. 본 연구는 두편이 논문으로 구성되어 있으며, 연구(I)에서는 강수발생과정을 위하여 고대재생과정(ARP)을 이용하였으며, 건조 습윤계속기간 분포에 대해서는 TBD, TPD, TNBD, LSD의 4가지 이산형 확률분포를 적용하였다. 후속논문인 연구(II)에서는 강수발생과정으로 Markov 연쇄모델을 이용한다. 그리고 습윤일의 강수량 분포에 대해서는 Gamma 분포, Pearson Type-III 분포, Type-III 극치분포, 3모수 Weibull 분포의 4가지 연속형 확률분포를 적용하였다. 연구(I)에서는 낙동강 유역의 대구, 고령, 밀양, 영주 관측소 및 섬진강 유역의 하동, 순창, 구례 관측소의 일 강수계열 자료를 사용하였으며, 강수발생과정과 습윤일의 강수량과정을 조합하여 구성한 두가지의 일 강수계열 모의발생 모델 A-W, A-G 모델의 적용성을 확인하였다.

• Industrial Engineering and Management Systems
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• 제11권4호
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• pp.390-396
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• 2012

The present paper extends the idea of tightened-normal-tightened sampling scheme to group acceptance sampling plans under the time truncated life tests. We consider three famous distributions that are widely used in the area of reliability such as the generalized exponential distribution, the Weibull distribution, and the Birnbaum-Saunders distribution in the proposed sampling plan. The plan parameters are determined such that the producer's risk and the consumer's risk are satisfied at the specified median life. Extensive tables showing plan parameters are provided at various values of the experiment time and the consumer's risk for each of three distributions for the practical use. Some examples are given to illustrate the procedure of the proposed plan.