• 한국신뢰성학회지:신뢰성응용연구
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• 제17권3호
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• pp.246-255
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• 2017

Purpose: This study proposes the optimal PM (preventive maintenance) policy of leased equipment for lessee's decision-making using two types of reliability condition. Methods: We consider reliability threshold based PM model. Equipment reliability is estimated and used as condition variable. The effect of repair for maintenance is imperfect and represented by age reduction factor. Results: We provide two PM policies. Policy 1 is focused on minimized total cost. This policy guarantees reliability threshold until last maintenance action. Policy 2 focus on maintaining reliability threshold during leased period. The proposed approach provides optimal reliability threshold under number of PM. Through result, we finally construct decision-making process for lessee using reliability threshold and end of reliability. Conclusion: This study provides two PM policy for lessee's decision-making. Through numerical example, we get a result of optimal reliability threshold, number of PM, optimum alternative under lessee's reliability condition.

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1994년도 교수 연수회(환경)
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• pp.450-468
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• 1994

Scientists have long used conventional toxicological methods to establish 'safe levels of exposure' for chemicals presumed to have threshold health effects or doses below which significant effects are unlikely to occur. These same methods cannot be used to establish safe levels of exposure for non-threshold pollutants. such as carcinogens. Therefore. Federal regulatory agencies in the United States are using risk assessment methods to provide information for public health policy decisions concerning increases in risk associated with increases in exposure to carcinogenic and other non-threshold pollutants. Acceptable exposure/risk levels are decided by policymakers who consider descriptions and estimates of risks together with social and economic benefits from the uses of the chemical. 1bis paper focuses on the development of quantitative risk assessment approaches by Federal regulatory agencies in the United States, and identifies the mathematical models currently being used for risk extrapolation. including their inherent uncertainties. The uncertainties and limitations of these methods have led some scientists to question the utility of quantitative risk extrapolation. The experience of the; U.S. Environmental Protection Agency (EPA). as summarized in this paper. can provide a realistic basis for evaluating the pros and cons. Finally. shortcomings in current risk assessment methods and their use in policy decisions are explored. and areas for possible improvement. given current scientific knowledge. are identified.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.919-922
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• 1998

A content-base search method is required for video which has an unformatted and huge size of data. The index techniue is necessary for the content-based search of the video data. The first step of the video indexing is a cut detection. We propose a dynamic threshold method which change a threshold value during the cut detection process. We demonstrate that the proposed method is more efficient than the existing methods.

• Communications for Statistical Applications and Methods
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• 제8권1호
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• pp.109-115
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• 2001

Wavelet coefficients are known to have decorrelating properties, since wavelet is orthonormal transformation. but empirically, those wavelet coefficients of images, like edges, are not statistically independent. Jansen and Bultheel(1999) developed the empirical Bayes approach to improve the classical threshold algorithm using local characterization in Markov random field. They consider the clustering of significant wavelet coefficients with uniform distribution. In this paper, we developed wavelet thresholding algorithm using Laplacian distribution which is more realistic model.

• Communications for Statistical Applications and Methods
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• 제19권5호
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• pp.705-720
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• 2012

In this paper, we introduce a hierarchical Bayesian model to simultaneously estimate the thresholds of each 6 cities. It was noted in the literature there was a dramatic increases in the number of deaths if the mean temperature passes a certain value (that we call a threshold). We estimate the difference of mortality before and after the threshold. For the hierarchical Bayesian analysis, some proper prior distribution of parameters and hyper-parameters are assumed. By combining the Gibbs and Metropolis-Hastings algorithm, we constructed a Markov chain Monte Carlo algorithm and the posterior inference was based on the posterior sample. The analysis shows that the estimates of the threshold are located at $25^{\circ}C{\sim}29^{\circ}C$ and the mortality around the threshold changes from -1% to 2~13%.

• 대한전자공학회논문지
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• 제17권2호
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• pp.10-14
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• 1980

본 논문에서는 DH-laser diode의 threshold current를 계산하기 위하여 2차고조파 왜곡 (se cond harmonic distortion)에 대해 Rate 방정식 (Rate-equation)을 동적상태와 정적상태 방정식으로 연릴하여 계산하였다. 특히 고조파 왜곡 ( )을 계산하는데 바이어스 전류 에 대하여 변조 전류 을 변조계수 m으로 놓고 (Jm=mJo)계산하여 주입전류 J가 Jth에서 2차 고조파 왜곡이 최대치를 가짐을 보여 ,이제까지 알려진 Jth조사 방법보다 간편하고 정확하게 조사할 수 있음을 제시하였다.

• 조명전기설비학회논문지
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• 제26권1호
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• pp.1-7
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• 2012

As the standard lighting required in the threshold zone of a road tunnel is determined by the enough contrast. Lighting design, therefore, must be determined by the calculation method of threshold luminance based on the adaptation luminance of the driver approaching the tunnel. The veiling luminance and the luminance in the access zone were measured at different time and in different weather using the veiling luminance method, a kind of perceived contrast methods, and the L20 method when the range of vision was 20 degrees. On the basis of the measured data each threshold luminance was calculated and its results were analyzed.

• 한국수자원학회논문집
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• 제41권5호
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• pp.527-544
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• 2008

GPD 모형은 수문학 극치확률량 해석에 주로 적용되어 왔다. 극치 통계의 주목적은 드문 사상의 예측이며, 주요 문제점으로는 임계값 또는 임계값 초과치들에 대한 정확한 산정방법이 없어 그 추정이 매우 어렵다는 것이다. 본 연구에서는 임계값 또는 임계값 초과치들을 산정하기 위하여 4가지 방법을 적용하였다. 그 비교를 위하여 GPD 모형에 적용하여 7개의 지속시간(1, 2, 3, 6, 12, 18 및 24시간)과 10개의 재현기간(2, 3, 5, 10, 20, 30, 50, 70, 80 및 100년)에 대한 매개변수 및 Quantile을 추정하였다. 3변수 GPD의 매개변수 및 Quantile을 추정하기 위하여 MOM, ML과 PWM을 적용하였다. 적합도를 추정하기 위하여 K-S, CVM 및 A-D 검정을 수행하였고 Monte Carlo 실험으로 상대 제곱근오차를 산정하였다. 이러한 방법들을 이용하여 임계값 산정방법들을 비교하여 최적화된 방법을 추정하였다.

• Journal of Preventive Medicine and Public Health
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• 제32권1호
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• pp.17-29
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• 1999

Objectives. This study was carried out to analyze the hearingthreshold levels and relating factors of 1,048 workers with noiseinduced hearing loss$(D_1)$. Methods. We analyzed the hearing-threshold levels and relating factors of 1,048 workers with noise-induced hearing loss$(D_1)$ examined by the summary reports of specific health examination results of industries and personal reports of specific health examination results reported by 58 specific health examination institutes and 8 secondary pneumoconiosis examination institutes in 1996. Results. Among 1,048 workers at 510 workplaces, male workers were 1,009 (96.3%) and female workers were 39 (3.7%). The mean ages of workers initially exposed to noise and at present were 28.7 and 47.2, respectively. The duration of total exposure was 16.5 years. Average hearing-threshold levels analyzed by three-divided classification of the study subjects were 43.7dB(Lt) and 42.6dB(Rt). Those analyzed by six-divided classification were 50.5dB(Lt) and 48.6d8(Rt). Among workers with noise-induced shearing loss$(D_1)$, 16.3% was unilateral hearing loss and 84.6% was classified to compensation case. 8.8%(Rt) and 10.2%(Lt) of them were suspected to be conductive hearing loss by differences of air-bone hearing-threshold levels. Hearing-threshold levels of workers in manufacturing industry were significantly increased during the short exposure compared with the levels in mining industry. Among manufacturing industries, hearing-threshold levels of workers in trailer and other transportation equipment manufacturing industry were significantly increased. Age and duration of total noise exposure were not significantly related to the average hearing-threshold levels analyzed by three-divided classification. Hearing-threshold levels of female workers were significantly increased during the short exposure compared with those of male workers. Hearing-threshold levels of workers at the high risk group, ages of 20s, 30s and total exposure duration of less than 10 years, were not significantly increased compared with those of the other groups. However, they were exposed at young ages. The 3 leading industries of workers at high risk group were trailer and other transportation equipment manufacturing, automobile manufacturing and assemble-metal manufacturing industries. Conclusions. This study was the first nationwide analysis of the hearing-threshold levels and relating factors of workers with noise. induced hearing loss$(D_1)$. We found the differences of the real number by the statistics of the department of labour and the expected number of worker' s compensations for occupationally-induced hearing loss estimated by this study. According to the results of this study, we should carefully examine the methods to narrow this difference.

• 한국컴퓨터정보학회논문지
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• 제19권2호
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• pp.183-191
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• 2014

본 연구는 웹 소프트웨어의 복잡도와 객체지향 프로그래밍 측정자인 클래스 수(NOC), 메서드 수(NOM)와의 상관관계를 통하여 순환복잡도를 정량적으로 분석하고자 한다. 웹 환경에서 소프트웨어의 복잡도, NOC, NOM의 빈도분포를 근거로 복잡도한계값과 NOC한계값, 복잡도 한계값과 NOM한계값의 상관관계를 파악하기 위하여 실제 사용되는 10개의 웹 프로젝트에서 4,000여개의 ASP 파일이 표본으로 사용되었다. 실험 결과 NOC한계값은 21, NOM한계값은 40이었고 복잡도는 68의 높은 값을 보였으며 10개의 프로젝트 중 NOC, NOM이 특히 높은 빈도를 보이는 2개의 프로젝트를 제외한 8개의 프로젝트는 NOC한계값은 12, NOM한계값은 21이었고 복잡도 한계값도 52의 상대적으로 낮은 값을 나타내 상관관계가 있는 것으로 판명이 되었다. 또한 복잡도, NOC, NOM의 한계값이 낮은 8개의 프로젝트는 내부 관리 소프트웨어이었고 나머지 2개의 프로젝트는 외부 매매 서비스 소프트웨어임이 밝혀져 업무 특성에 따라 설계 단계에서 클래스 수, 메서드 수가 결정됨에 따라 복잡도도 미리 추정할 수 있어 품질 향상에 기여할 수 있을 것이다.