• 디지털산업정보학회논문지
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• 제7권4호
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• pp.7-14
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• 2011

Infinite failure NHPP models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rate per fault (hazard function). This infinite non-homogeneous Poisson process is model which reflects the possibility of introducing new faults when correcting or modifying the software. In this paper, polynomial hazard function have been proposed, which can efficiency application for software reliability. Algorithm for estimating the parameters used to maximum likelihood estimator and bisection method. Model selection based on mean square error and the coefficient of determination for the sake of efficient model were employed. In numerical example, log power time model of the existing model in this area and the polynomial hazard function model were compared using failure interval time. Because polynomial hazard function model is more efficient in terms of reliability, polynomial hazard function model as an alternative to the existing model also were able to confirm that can use in this area.

• International Journal of Reliability and Applications
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• 제3권1호
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• pp.1-16
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• 2002

In reliability engineering, the bathtub-shaped hazard rates play an important role in survival analysis and many other applications as well. For the bathtub-shaped, initially the hazard rate decreases from a relatively high value due to manufacturing defects or infant mortality to a relatively stable middle useful life value and then slowly increases with the onset of old age or wear out. In this paper, we present a new two-parameter lifetime distribution function, called the Loglog distribution, with Vtub-shaped hazard rate function. We illustrate the usefulness of the new Vtub-shaped hazard rate function by evaluating the reliability of several helicopter parts based on the data obtained in the maintenance malfunction information reporting system database collected from October 1995 to September 1999. We develop the S-Plus add-in software tool, called Reliability and Safety Assessment (RSA), to calculate reliability measures include mean time to failure, mean residual function, and confidence Intervals of the two helicopter critical parts. We use the mean squared error to compare relative goodness of fit test of the distribution models include normal, lognormal, and Weibull within the two data sets. This research indicates that the result of the new Vtub-shaped hazard rate function is worth the extra function-complexity for a better relative fit. More application in broader validation of this conclusion is needed using other data sets for reliability modeling in a general industrial setting.

• 정보과학회지
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• 제5권2호
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• pp.94-98
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• 1987

本 論文에서는 多値論理回路를 實現함에 있어서 發生하는 Hazard를 2가 지, 卽 Function Hazard와 Logic Hazard로 分類하였고 이의 解決方案으로 入力 信號가 Switching하여 最終 安定 level에 到達했을 때 Switching函數를 決定하고 이 函數로써 Switching函數의 Unate性을 試圖하였다. 그리고 內部回路에서 信號 가 遷移될 때 內部回路의 遲延 遲延時間으로 말미암아 發生되는 Hazard狀態를 Redundant回路를 實現하였다. 또 이 論理回路를 基本으로한 N値 Flip-flop N과 Shift Register, Counter等의 順序論理回路를 構成하였다.

• 한국철도학회논문집
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• 제16권2호
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• pp.104-109
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• 2013

The paper will outline how hazard identification and risk evaluation can effectively be performed to obtain Tolerable Hazard Rates (THR). As a target group manufacturers are addressed, who face the situation, that for a generic application THRs are needed for compliance with EN 50129 [1]. Focusing on functional hazards this paper shows a possible hazard log and the relevant analysis methods. The terms safety barrier and barrier function will be introduced and used instead of the term "safety function". As functional hazards and barrier functions depend on each other, emphasis will be put on a comprehensive and detailed definition of barrier functions and the usage of function lists. By using detailed and complete hazard and barrier function definitions THRs can be obtained while at the same time the approach becomes clear how the hazard rates (HR) will be established.

• Journal of the Korean Data and Information Science Society
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• 제22권3호
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• pp.613-618
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• 2011

The proposed method is based on a penalized log partial likelihood of Cox proportional hazard model with L1-penalty. We use the iteratively reweighted least squares procedure to solve L1 penalized log partial likelihood function of Cox proportional hazard model. It provide the ecient computation including variable selection and leads to the generalized cross validation function for the model selection. Experimental results are then presented to indicate the performance of the proposed procedure.

• International Journal of Reliability and Applications
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• 제2권1호
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• pp.49-56
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• 2001

In this paper we consider empirical Bayes estimation of the hazard rate and survival probabilities with right censored data under the assumption that the hazard function is constant over the period of observation and the prior distribution is gamma. We provide an estimator of the first derivative of the prior moment generating function that converges at each point to the true value in $L_2$ and use it to obtain, easy to compute, asymptotically optimal estimators under the squared error loss function.

• Communications for Statistical Applications and Methods
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• 제1권1호
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• pp.20-26
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• 1994

The hazard function is a non-negative function that measures the propensity of failure in the immediate furture, and is frequently used as a decision criterion, especially in replacement decisions. In this paper, we compute approximate confidence intervals for the lognormal hazard function under Type I censored data, and show how to choose the sample size needed to estimate a point on the hazard function with a specified degree of precision. Also we provide a table that can be used to compute the sample size.

• Communications for Statistical Applications and Methods
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• 제23권3호
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• pp.189-201
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• 2016

In survival analysis, the Nelson-Aalen estimator and Peterson estimator are often used to estimate a cumulative hazard function in randomly right censored data. In this paper, we suggested the smoothing version of the cumulative hazard function estimators using a Bezier curve. We compare them with the existing estimators including a kernel smooth version of the Nelson-Aalen estimator and the Peterson estimator in the sense of mean integrated square error to show through numerical studies that the proposed estimators are better than existing ones. Further, we applied our method to the Cox regression where covariates are used as predictors and suggested a survival function estimation at a given covariate.

• Journal of the Korean Data and Information Science Society
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• 제26권6호
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• pp.1225-1238
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• 2015

본 연구에서는 직장암 환자들의 수술 후 재발까지의 시간 데이터에 대해 집단 간 생존함수 양상에 차이가 있는지 로그 순위 검정 결과 유의수준 10%에서 포도당 단일수송체 (GLUT1)의 수준, 수술 전 병기 (cstage), 수술 후 병기 (ypstage)에 따른 차이가 유의하며, Cox 비례위험률 모형을 이용하여 검정한 결과 가장 유의한 공변량은 포도당 단일수송체와 수술 후 병기였다. 지수분포를 따른다고 가정할 경우, 우도함수를 기반한 여러 가지 위험률 변화점을 추정하였다.

• 전자공학회논문지C
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• 제36C권10호
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• pp.47-55
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• 1999

본 논문에서는 비동기 논리 회로 합성을 위해서 신호천이 그래프 상에서 직접 펑션 해저드를 제거하고 신호선의 추가에 따른 면적의 오버헤드를 최소화하는 새로운 알고리듬을 제안한다. 기존의 펑션 해저드 제거방법은 신호선 사이의 전이 관계를 나타내는 신호천이 그래프로부터 상태를 할당하여 얻어지는 상태 그래프를 이용하였다. 이 방법은 해저드의 제거를 위해 동기 시스템에서 사용하는 방법을 그대로 적용할 수 있으나, 상태 그래프의 구성과 조작에 많은 시간이 소요되는 단점이 있다. 이에 따라 신호천이 그래프를 직접 이용하는 방법이 제시되었으나 해저드의 제거에 따른 면적의 오버헤드는 고려되지 않았다. 본 논문에서는 신호천이 그래프로부터 직접 해저드를 제거함으로써 기존의 상태 그래프를 이용하는 방법에 비해 계산량을 줄이고, 추가되는 신호를 구현하기 위한 논리회로의 크기는 최소항과 적항의 개수를 조절하여 최소화하였다. 제안하는 알고리듬을 벤치마크 데이터로 실험한 결과 면적의 오버헤드가 평균 15%이상 감소함을 확인하였다.