• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.75-78
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• 2002

복합재구조물에 대한 피로수명과 잔류강도를 평가하기 위한 단순화된 방법을 소개하였다. 모델의 특성화를 위해 필요한 실험을 줄이기 위하여 강도저하 파라미터수를 피로수명의 함수로 가정하였다. 임의의 순서로 배열된 하중 스펙트럼에서 응력수준에 따른 피로수명을 추출하기위해 S-N 선도를 사용하였다. 그리고 상이한 응력비(stress ratio)에 대한 영향을 고려하기위해 Goodman 형식의 방법(fatigue envelope)을 사용하였다. 잔류강도는 하중 사이클 수와 응력진폭의 함수로 가정하였으며 임의의 하중사이클 후의 잔류강도분포는 2 모수 Weibull 분포로 표현하였다.

• Composites Research
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• 제16권1호
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• pp.13-18
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• 2003

복합재료의 피로수명을 평가하는 것은 여러 가지 파손모드와 파손모드 간의 강호작용 때문에 복잡하다. 본 논문에서는 현상론적인 모델(비선형 강도저하 모델)을 이용하여 피로수명과 잔류강도를 예측할 수 있는 방법을 제시하였다. 잔류강도를 하중 사이클 수와 피로응력의 함수로 가정하였으며, 계산에 필요한 모델변수(강도저하 파라미터, 피로수명형상 파라미터)를 피로수명의 함수로 가정하였다 임의로 배열된 하중 스펙트럼 상에서 응력수준에 따른 모델 매개변수를 구하기 위해 S-N 선도를 이용하였고, 상이한 응력비에 대하여 전술한 매개변수를 Goodman식의 보정을 통하여 계산하였다(피로선도). 임의의 하중이력 후의 잔여강도 분포를 2모수 weibull 함수로 표현하였다.

• International Journal of Reliability and Applications
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• 제7권2호
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• pp.177-186
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• 2006

Typical confidence intervals for a mean or mean residual life (MRL) are centered about the mean or mean residual life. We discuss novel confidence intervals that produce statements like "we are 95% confident that the MRL function, e(t), is greater than a prespecified $\mu_o$ for all t in the interval [0, $\hat{\theta})$)" where $\hat{\theta}$ is determined from the sample data, confidence level, and $\mu_o$. Also, we can have statements like 'we are 95% confident that the MRL of population 1, namely $e_1$(t), is greater than the MRL of population 2, $e_2$(t), for all t in the interval [0, $\hat{\theta}$)" where $\hat{\theta}$ is determined from the sample data and confidence level. We illustrate these one and two sample confidence intervals on internal bonds (tensile strengths) for an important modem engineered wood product, called medium density fiberboard (MDF), used internationally.

• Journal of the Korean Data and Information Science Society
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• 제22권1호
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• pp.89-97
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• 2011

본 연구에서는 Buckley와 James의 방법을 이용하여 중도절단된 자료를 보완한 조건부생존함수 추정량으로부터 조건부평균잔여수명함수를 추정하는 방법을 제안하고, 모의실험을 통하여 제안된 방법의 효율성을 평가하였다. 모의실험 결과 비례위험모형이 아닌 경우 제안된 방법으로 추정한 조건부 평균잔여수명함수의 평균제곱오차가 Cox모형이나 Beran의 비모수적 방법을 이용하여 구한 추정치의 평균제곱오차보다 작게 나타났으며, 비례위험모형인 경우에는 제안된 방법으로 추정한 결과들이 Cox 모형을 이용하여 얻은 결과들과 비슷하게 나타났다. 또한 K대학교병원 외과에서 위암 수술을 받은 1,192명의 환자 자료를 이용하여 제안된 방법의 임상적 적용의 적절성을 평가하였다.

• 품질경영학회지
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• 제22권3호
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• pp.111-118
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• 1994

In this paper we propose a parametric and a nonparametric small sample estimators for the mean residual life (MRL) under the random censorship model using the partial moment approximation. We also compare the proposed nonparametric estimator with the well-known nonparametric MRL estimator based on Kaplan-Meier estimator of the survival function, and present the efficiency of the nonparametric method relative to the Weibull model for small samples.

• Journal of the Korean Statistical Society
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• 제33권2호
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• pp.191-202
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• 2004

The paper considers nonparametric empirical Bayes estimation of residual survival function at age t using a Dirichlet process prior V(a). Empirical Bayes estimators are proposed for the case where both the function ${\alpha}$(0, $\chi$] and the size a(R$\^$+/) are unknown. It is shown that the proposed empirical Bayes estimators are asymptotically optimal at a rate n$\^$-1/, where n is the number of past data available for the present estimation problem. Therefore, the result of Lahiri and Park (1988) in which a(R$\^$+/) is assumed to be known and a rate n$\^$-1/ is achieved, is extended to a(R$\^$+/) unknown case.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권3호
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• pp.220-228
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• 2018

Purpose: The purpose of this study is to investigate the tail behavior of the life distribution which exhibits an increasing failure rate or other positive aging effects after a certain time point. Methods: We characterize the tail behavior of the life distribution with regard to certain reliability measures such as failure rate, mean residual life and reliability function and derive several stochastic properties regarding such life distributions. Also, utilizing an L-statistic and its asymptotic normality, we propose new nonparametric testing procedures which verify if the life distribution has an increasing tail failure rate. Results: We propose the IFR-Tail (Increasing Failure Rate in Tail), DMRL-Tail (Decreasing Mean Residual Life in Tail) and NBU-Tail (New Better than Used in Tail) classes, all of which represent the tail behavior of the life distribution. And we discuss some stochastic properties of these proposed classes. Also, we develop a new nonparametric test procedure for detecting the IFR-Tail class and discuss its relative efficiency to explore the power of the test. Conclusion: The results of our research could be utilized in the study of wide range of applications including the maintenance and warranty policy of the second-hand system.

• 상하수도학회지
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• 제23권3호
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• pp.305-313
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• 2009

This paper provides a method for evaluating a residual life of water mains using a proportional hazard model(PHM). The survival time of individual pipe is defined as the elapsed time since installation until a break rate of individual pipe exceeds the Threshold Break Rate. A break rate of an individual pipe is estimated by using the General Pipe Break Model(GPBM). In order to use the GPBM effectively, improvement of the GPBM is presented in this paper by utilizing additional break data that is the cumulative number of pipe break of 0 for the time of installation and adjusting a value of weighting factor(WF). The residual lives and hazard ratios of the case study pipes of which the cumulative number of pipe breaks is more than one is estimated by using the estimated survival function. It is found that the average residual lives of the steel and cast iron pipes are about 25.1 and 21 years, respectively. The hazard rate of the cast iron pipes is found to be higher than the steel pipes until 20 years since installation. However, the hazard rate of the cast iron pipes become lower than the hazard rates of the steel pipes after 20 years since installation.

• 품질경영학회지
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• 제22권1호
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• pp.152-161
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• 1994

In this paper we develop a test for alternatives representing decreasing mean residual life. The test statistic for decreasing mean residual life, $K_{1n}$, is a modified version of Hollander and Proschan's test $V^*$ and critical constants and large sample approximation are shown to make the test readily applicable. Consistency is also shown for the tests based on $K_{1n}$. And small sample powers for four alernatives are obtained.

• 대한수학회지
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• 제58권1호
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• pp.237-264
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• 2021

In this work the stationary bootstrap of Politis and Romano [27] is applied to the empirical distribution function of stationary and associated random variables. A weak convergence theorem for the stationary bootstrap empirical processes of associated sequences is established with its limiting to a Gaussian process almost surely, conditionally on the stationary observations. The weak convergence result is proved by means of a random central limit theorem on geometrically distributed random block size of the stationary bootstrap procedure. As its statistical applications, stationary bootstrap quantiles and stationary bootstrap mean residual life process are discussed. Our results extend the existing ones of Peligrad [25] who dealt with the weak convergence of non-random blockwise empirical processes of associated sequences as well as of Shao and Yu [35] who obtained the weak convergence of the mean residual life process in reliability theory as an application of the association.