• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.272-274
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• 2003

Distribution system reliability evaluation estimates by approach methods such as Makove modelling or Monte Carlo simulation, equation of state and failure rate that is on one basic data used to these assessment technique is described as probability of average value. because average failure rate equipment device is aged as time goes by but there is shortcoming that such used failure rate does not evaluate thing which is correct in reliability change hereafter. In this paper, failure rate displayed that apply aging to basis equipment device by passing time using Weibull distribution one of life evaluation method and for express aging of component from utility's failure database.

• 전자공학회논문지A
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• 제32A권6호
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• pp.67-74
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• 1995

This paper proposes the step-stress type-I censoring model for analyzing the data of accelerated life test and reducing the time of accelerated life test. In order to obtain the data of accelerated life test, the step-stress accelerated life test was run with voltage stress to CMOS Hex Buffer. The Weibull distribution, the Inverse-power-law model and Maximum likelihood method were used. The iterative procedure using modified-quasi-linearization method is applied to solve the nonlinear equation. The proposed Weibull step-stress type-I censoring model exactly estimases the life time of units, while reducting the time of accelerated life test and the equipments of test.

• 한국농림기상학회지
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• 제19권3호
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• pp.130-139
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• 2017

기상청 동네예보 풍속으로부터 농작물의 강풍피해를 예측하기 위해, 방재기상관측지점 19곳의 2012년 풍속자료를 이용하여 기상청 동네예보의 3시간 간격과 동일한 0000, 0300 ${\cdots}$ 2100 시간대의 풍속과 직전 3시간 동안의 최대풍속 간의 관계를 직선회귀식으로 표현하였다. 매 3시간 마다 추정된 최대풍속 중 가장 큰 값을 일 최대풍속으로 간주하고, 이 때의 추정오차를 정규분포와 Weibull 분포 확률밀도함수로 표현하였다. 또한 일 최대풍속과 작물 피해 임계풍속 간의 편차를 추정오차 기반 확률 분포에 적용하여 확률누적값으로 풍해 '주의보'와 '경보' 단계를 설정하였다. 19지점별 최대풍속 추정 회귀계수(a, b)와 추정오차의 표준편차 및 Weibull 분포의 모수(${\alpha}$, ${\beta}$)는 공간내삽하여 분포도로 작성하고 종관기상관측지점 4곳(순천, 남원, 임실, 장수)의 격자값을 추출하였다. 이를 이용해 2012년의 일 최대풍속을 추정하고, 배 만삼길 품종의 낙과 발생 사례에서 제시된 풍속 10m/s를 낙과 임계풍속으로 간주, 풍해 주의보와 경보를 판정하였다. 그 결과, 최대풍속 추정오차를 Weibull 분포로 표현하여 풍해 위험 정도를 판정하는 것이 정규분포만을 이용하는 것보다 더 현장에 정확한 주의보를 발령할 수 있었다.

• 대한기계학회논문집
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• 제18권12호
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• pp.3149-3158
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• 1994

In this paper, using the formulation of dynamic equivalent load considering the effects of moment load and the equation to estimate the cage rotational speed, the new life equation of deep groove ball bearing under radial and moment loads was proposed. Fatigue life test apparatus with the measuring equipment of shaft and cage speed was designed and developed to be capable of subjecting combined radial and moment load. Fatigue life tests were executed by sudden death test method and the reliability of fatigue lives was evaluated by Weibull distribution analysis. From the results of fatigue tests and analysis, the relationships between film parameters and life adjustment factors were acquired. And it was turned out that so as to estimate the effect of moment load on fatigue life, the life adjustment factor as well as the dynamic equivalent load must be taken into account.

• 한국산림과학회지
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• 제101권4호
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• pp.599-605
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• 2012

본 연구의 목적은 굴참나무 임분의 직경분포와 ha당 재적 및 탄소량을 추정하는데 있다. 영급과 임분구조를 고려하여 굴참나무 임분에서 354개소를 조사하고 시료를 수집하였다. 임령에 따른 직경분포를 파악하기 위하여 Weibull 모형을 사용하였으며 모수의 추정은 단순적률법(Simplified method-of-moments)을 이용하였다. 사용된 자료 중에서 80%는 모형개발에 사용하였고, 나머지 20%는 개발된 모형의 검정에 사용하였다. 모형의 검정에는 적합도지수(Fitness Index)와 평균오차제곱(Root Mean Square Error), Kolmogorov-Smirnov 통계치가 이용되었다. 검정자료에서 추정된 지위지수, 수고, 재적식의 적합도지수는 각각 0.967, 0.727, 0.988이고 평균오차제곱은 2.763, 1.817, 0.007이며, Weibull 모형의 Kolmogorov-Smirnov 적합도는 75%를 나타내었다. 본 연구를 통해 개발된 모형에서 50년생의 굴참나무임분이 14의 지위지수와 697본의 분수를 나타내는 경우, 재적은 $188.69m^3/ha$이고 지상부 탄소량은 90.30 tC/ha으로 추정되었다. 본 연구의 결과는 활엽수 수종에 대한 생장정보의 제공이 가능하고 굴참나무 탄소량 추정에 활용이 가능하다.

• 한국산림과학회지
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• 제98권5호
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• pp.576-583
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• 2009

Based on the stem analysis and biomass measurement of 36 trees and 1,576 branches in Pinus sylvestris var. mongolica (Mongolian pine) plantations of Northeast China, this study was conducted to develop estimation model equation for leaf biomass of a single tree and branch, to examine the vertical distribution of leaf biomass in the crown, and to evaluate the proportional ratios of biomass by tree parts, stem, branch, and leaf. The results indicated that DBH and crown length were quite appropriate to estimate leaf biomass. The biomass of single branch was highly correlated with branch collar diameter and relative height of branch in the crown, but not much with stand density, site quality, and tree height. Weibull distribution function would have been appropriate to express vertical distribution of leaf biomass. The shape parameters from 29 sample trees out of 36 were less than 3.6, indicating that vertical distribution of leaf biomass in the crown was displayed by bell-shaped curve, a little inclined toward positive side. Apparent correlationship was obtained between leaf biomass and branch biomass having resulted in linear function equation. The stem biomass occupied around 80% and branch and leaf made up about 20% of total biomass in a single tree. As the level of tree class was increased from class I to class V, the proportion of the stem biomass to total biomass was gradually increased, but that of branch and leaf became decreased.

• 한국인터넷방송통신학회논문지
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• 제22권3호
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• pp.193-200
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• 2022

본 연구에서는 소프트웨어 신뢰성 분야에서 많이 사용하는 Weibull 수명 분포((Goel-Okumoto, Rayleigh, Type-2 Gumbe)에 근거하여 유한 고장 NHPP 소프트웨어 신뢰성 모형을 소프트웨어 개발 모형에 적용한 후, 비용의 속성을 비교하여, 분석하였다. 본 연구를 위하여 소프트웨어 시스템의 정상 운용 중 검출된 고장시간 데이터를 수집하여 사용하였고, 제안된 모형의 모수 추정은 최우추정법을 적용하였으며, 비선형 방정식의 계산은 이분법을 사용하여 해결하였다. 그 결과, 첫째, 소프트웨어 개발 모형의 단위 시간당 테스팅 비용과 단일 고장을 제거하는 비용이 증가하면 비용은 증가하였지만 방출시간은 변하지 않았고, 정상적인 시스템 운용 중에 검출된 고장 수리 비용이 증가하면 비용 증가와 함께 방출 시간도 지연됨을 알 수 있었다. 둘째, 제안된 모형들을 종합적으로 비교 분석한 결과, Type-2 Gumble 모형이 Rayleigh 모형과 Goel-Okumoto 기본 모형 보다 개발비용이 적고, 방출 시간 포인트도 상대적으로 빨라서 가장 효율적인 모형임을 알 수 있었다. 셋째, 본 연구를 통하여 Weibull 분포 모형의 개발비용 속성을 새롭게 분석하였으며, 분석된 데이터는 소프트웨어 개발자들이 개발 비용과 방출 시간에 대한 속성을 탐색하는 데 필요한 설계 데이터로 활용할 수 있을 것으로 기대한다.

• International Journal of Safety
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• 제1권1호
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• pp.36-42
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• 2002

This paper is aimed at predicting the life of rubber insulating gloves under normal operating stresses from relatively rapid test performed at higher stresses. Specimens of rubber insulating gloves are subject to multiple stress conditions, i.e. combined electrical and thermal stresses. Two modes of electrical stress, step voltage stress and constant voltage stress are used in specimen aging. There are two types of test for electrical stress in this experiment: the one is Breakdown Voltage (BDV) test under step voltage stress and thermal stress and the other is lifetime test under constant voltage stress and temperature stress. The ac breakdown voltage defined as the break-down point of insulation that leakage current excesses a limit value, l0mA in this experiment, is determined. Because the very high variability of aging data requires the application of statistical model, Weibull distribution is used to represent the failure times as the straight line on Weibull probability paper. Weibull parameters are deter-mined by three statistical methods i.e. maximum likelihood method, graphical method and least squares method, which employ SAS package, Weibull probability paper and FORTRAN, respectively. Two chosen models for predicting the life under simultaneous electrical and thermal stresses are inverse power model and exponential model. And the constants of life equation for multistress aging are calculated using numerical method, such as Gauss Jordan method etc.. The completion of life equation enables to estimate the life at normal stress based on the data collected from accelerated aging test. Also the comparison of the calculated lifetimes between the inverse power model and the exponential model is carried out. And the lifetimes calculated by three statistical methods with lower voltage than test voltage are compared. The results obtained from the suggested experimental method are presented and discussed.

• 대한토목학회논문집
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• 제5권4호
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• pp.113-119
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• 1985

본(本) 논문(論文)에서는 휨하중을 받는 콘크리트의 피로특성 및 피로신뢰성이 연구(硏究)되었다. 콘크리트보에 대한 피로실험이 수행되었으며, 피로하중은 4 점하중 상태로 작용되었다. 본(本) 실험결과(實驗結果)로부터 S-N 관계가 얻어졌으며, 콘크리트의 휨피로 강도를 예측하기 위한 공식(公式)이 도출되었다. 또한 본(本) 논문(論文)에서는 콘크리트의 휨피로에 대한 확률론적 해석방법이 제안되었다. 본(本) 연구결과(硏究結果) 콘크리트의 피로거동을 서술하는 데는 Weibull 분포가 적절한 것으로 나타났다.

• 한국기계가공학회지
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• 제19권6호
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• pp.67-72
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• 2020

Life tests are essential in reducing the catastrophic damage caused by the accidents of large machinery such as aircraft and ships. However, life tests are challenging to implement due to the high costs and time required to test the life of large machinery parts. Therefore, it is advantageous and convenient to apply accelerated life test techniques for key components to reduce costs and time. In fact, extensive research has already been conducted on these techniques. However, recently, there have been cases in which an experimental value was applied to the shape parameter of the Weibull distribution used in the reliability test, but the test time was not significantly reduced. Therefore, in this paper, the shape parameters are estimated from the probability density function of the Weibull distribution for the analysis of an accelerated life test for bladder accumulators, which are core components of military helicopters. The test time was derived based on the number of samples and confidence level by substituting it into the test time equation. Next, the accelerated life test time was calculated using the steady-state test time with an acceleration factor obtained from the Arrhenius model. The steady-state life test required approximately 15,000 H, whereas the accelerated life test time for one sample at 100 ℃ was 34% shorter than that of the steady-state life test.