• Journal of the Korean Data and Information Science Society
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• 제21권3호
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• pp.555-560
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• 2010

One-dimensional approach to two-dimensional warranty data involves modeling us- age as a function of time. Iskandar (1993) suggests a simple linear model for usage. However, simple linear form of intensity function is of limited value to model the situa-tion where the intensity varies over time. In this study Weibull intensity is considered where the scale parameter is expressed in terms of different models. We will nd out how each parameter in the model a ects the warranty cost and which model gives a bigger number of failures within the two-dimensional warranty region.

• 한국해안·해양공학회논문집
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• 제36권1호
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• pp.20-36
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• 2024

요 지 : 본 연구에서는 먼저 우리나라 해역별 해양환경 특성이 담긴 장기 파랑 관측자료로부터 Goda 모형을 활용하여 파력과 양력 시계열자료를 생성하였다. 이어 이렇게 생성된 시계열자료부터 Three-parameter Weibull distribution에 기반한 파력과 양력 확률모형을 개발하였다. 해역별로 다른 우리나라 해양환경은 파력과 양력 확률모형 모수에서도 그 차이를 확연하게 드러내었다. 충분히 발달한 풍성 파가 우월한 남해안의 경우 큰 Scale Coefficient, 작은 Location Coefficient, 1.3 전후의 Shape Coefficient로 특정되는 것을 확인하였다. 이에 비해 파랑의 성장이 취송거리에 의해 제한되는 서해를 마주하고 있는 군산의 경우 작은 Scale Coefficient, 큰 Location Coefficient, 2.0 전후의 Shape Coefficient로 특정되었다. 서해와 남해가 만나는 해역을 마주하고 있는 목포의 경우 작은 Scale Coefficient, 큰 Location Coefficient, 제일 작은 Shape Coefficient를 지녀 남해와 서해의 해양환경이 혼재한다는 사실도 확인할 수 있었다.

• 동력기계공학회지
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• 제21권3호
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• pp.37-44
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• 2017

In this study, failure analysis of the angular pin for molding machines to aluminum component molding was carried out. SM45C steel was used for the angular pin, it was surface hardened by the induction surface hardening heat treatment. The cross section of damaged angular pin was observed, and micro Vickers hardness value from the fractured part was measured. Brittle fracture was occurred from the fracture surface of angular pin, therefore, impact toughness value was evaluated by V-notch Charpy impact test. It was confirmed that the impact absorption energy was high when was tempered at a high temperature for a long time, and the toughness was slightly increased. Also, 2-parameter Weibull statistical analysis was investigated in order to evaluate the reliability of the measured micro Vickers hardness values and absorbed energy. The micro Vickers hardness and absorbed energy well followed a two-parameter Weibull probability distribution, respectively. The reverse design against angular pin was proposed as possible by using test results.

• 대한전기학회논문지:전력기술부문A
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• 제55권3호
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• pp.109-115
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• 2006

The Weibull distribution is a good candidate for accurate probabilistic model with its rich shape-forming ability and relatively simple CDF(cumulative distribution function). If there are sufficient information to get convincible mean and variance for a probabilistic event, reliable parameters of the Weibull distribution can be determined uniquely. However, sufficient information is not given as usual. There needs more deliberate model building method for that case. This Paper presents an effective parameter estimation technique for Weibull distribution with limited failure data.

• Journal of the Korean Data and Information Science Society
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• 제17권3호
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• pp.927-932
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• 2006

The techniques for selecting and evaluating prior distributions are studied over recent years which the primary emphasis is on noninformative priors. But, noninformative priors are typically improper so that such priors are defined only up to arbitrary constants which affect the values of Bayes factors. In this paper, we consider the Bayesian hypotheses testing for the Weibull shape parameter based on fractional Bayes factor which is to remove the arbitrariness of improper priors. Also we present a numerical example to further illustrate our results.

• 한국전기전자재료학회논문지
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• 제12권1호
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• pp.11-17
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• 1999

Aging characteristics of the crosslinked polyethylene have been measured after applying electrical, thermal and combined stresses. ICP and FT-IR measurements confirmed diffusion of low molecular weight components such as antioxidant and presence of carbonyl group. Carbonyl group of aged crosslinked polyethylene under combined stress was detected by FT-IR. As deterioration of the crosslinked polyethylene progresses, crystallinity degree and density decrease. Also, dielectric properties have been measured by tan $\delta$ and $\varepsilon$$_{r}$ measurements. The three-parameter Weibull distribution was found to be the best suited among other probabilistic distribution representing the dielectric breakdown strength of aged crosslinked polyethylene. The scale parameter and location parameter decreases as the applied stress increases. The shape parameter increases as the stress increases.s.

• 대한기계학회논문집A
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• 제35권10호
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• pp.1281-1289
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• 2011

본 논문에서는 소형풍력발전시스템 블레이드 제작에 사용되는 복합재료의 피로수명 데이터에 대한 통계적 해석을 위하여 다양한 확률분포 모델의 적합성에 대한 연구를 수행하였다. 이를 위하여 삼축 유리섬유강화 복합재료를 대상으로 0$^{\circ}C$, 45$^{\circ}C$ 및 90$^{\circ}C$ 의 하중방향에 대한 인장시험을 실시하였다. 또한 상기의 하중방향에 대하여 4 수준의 피로응력준에서의 피로시험을 수행하였다. 이를 통하여 획득한 피로수명 데이터를 대상으로 1) 전체 적합성, 2) 끝단 적합성 및 3) 피로물리 일치성의 기준을 이용하여 2 모수 Weibull, 3 모수 Weibull, 정규 및 대수정규분포의 적합성을 평가하였다. 또한 피로수명의 분산에 대한 하중방향 및 피로응력의 영향 역시 검토하였다.

• 전기학회논문지
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• 제66권3호
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• pp.500-506
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• 2017

In 2014, ISO 55000s has been enacted and the power plant asset management is becoming a hot issue for all over the world. The asset management system is being developed as a combination of CBM(Condition Based Maintenance) and RCM(Reliability Centered Maintenance). Therefore, the research on the calculation of the failure rate which is the most basic index of RCM is actively carried out. The failure rate calculation has been going on for a long time, and the most widely used probability distribution is the Weibull distribution. In the Weibull distribution, the failure rate function is determined in three types according to the value of the shape parameter. However, the Weibull distribution has a limitation that it is difficult to apply it when the trend of failure rate changes-such as bathtub curves. In this paper, the failure rate is calculated using the mixture Weibull distribution which can appropriately express the change of the shape of the failure rate. Based on these results, we propose the necessity and validity of applying mixture Weibull distribution.

• 한국신뢰성학회지:신뢰성응용연구
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• 제13권3호
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• pp.191-206
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• 2013

Application areas for Lifetime Performance Index(LPI), a kind of process capability index to be frequently used as a means of measuring process performance are illustrated with examples. Statistical properties for maximum likelihood and unbiased estimators of LPI are evaluated and discussed under Weibull distribution with known shape parameter. Furthermore, guidelines for selecting an estimator of LPI are also presented.

• 대한기계학회논문집A
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• 제35권4호
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• pp.375-381
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• 2011

본 연구의 주목적은 마그네슘합금의 피로균열성장거동을 지배하는 파라미터들의 확률론적 특성을 규명하는 것이다. 피로균열전파실험은 AZ31 마그네슘합금의 CT 시편을 이용하여 통계적으로 수행하였으며, 시편두께, 하중비, 최대하중 등의 여러 가지 실험조건으로 실온에서 진행하였다. 이 실험을 통하여 획득한 통계적 피로 데이터를 이용하여 피로거동 파라미터의 확률적 변동성 해석과 함께 확률분포 적합성을 고찰하였다. 균열성장속도계수는 확률적으로 매우 큰 변동성을 나타내는 파라미터로 밝혀졌으며, 반면에 균열성장속도지수는 매우 작은 변동성을 나타냄으로써 재료상수로 볼 수 있을 것이다. 피로거동 파라미터인 균열성장속도계수와 균열성장속도지수에 가장 적합한 확률분포는 3-파라미터 Weibull 분포이며, 2-파라미터 Weibull 분포는 균열성장속도계수의 경우에만 양호한 적합성을 나타낸다는 것을 규명하였다.