• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.763-768
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• 2013

The simulation investigation on the availability with failure density function of major equipment for a sewage treatment plant has been carried out. This study focuses on the availability of the plant and criticality with equipment module induced by component layout and its failure function. The equipment classification of sewage treatment plant and its failure function are established. Also solution methodologies are introduced as Monte-Carlo simulation method and event algorithm for uncertainty problem. The availability in the case of serial connection of equipment with all exponential function is calculated as around 50.4%. In other case of parallel combination with back up equipment, the availability showed over 80.1%. The criticality that a ffects availability showed high value over 77% in the dehydration and concentration process of sludge.

• Journal of the Korean Society for Railway
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• v.12 no.3
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• pp.348-356
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• 2009

The objective of this paper is to estimate the DMT utility function for the transportation mode choice using SP survey. With the freight OD data the estimated utility function can be used as a basic data for forecasting DMT market. 3 alternatives of transportation mode are considered in SP survey; railway, road and DMT. The utility functions are developed according to the freight items, which are container, steel and chemical product. In this study the attribute variable are chosen as time, cost and reliability. The number of level for attribute variables are 3. The high valve is determined as +10% above the standard and the low value -20% below the standard.

• The Korean Journal of Applied Statistics
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• v.33 no.4
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• pp.379-393
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• 2020

A terminal event such as death may censor an intermediate event such as relapse, but not vice versa in semi-competing risks data, which is often seen in medicine, public health, and epidemiology. We propose a Weibull regression model with a normal frailty to analyze semi-competing risks data when all three transition times of the illness-death model are possibly interval-censored. We construct the conditional likelihood separately depending on the types of subjects: still alive with or without the intermediate event, dead with or without the intermediate event, and dead with the intermediate event missing. Optimal parameter estimates are obtained from the iterative quasi-Newton algorithm after the marginalization of the full likelihood using the adaptive importance sampling. We illustrate the proposed method with extensive simulation studies and PAQUID (Personnes Agées Quid) data.

• Convergence Security Journal
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• v.12 no.3
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• pp.19-26
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• 2012

In this study, software products developed in the course of testing, software managers in the process of testing software and tools for effective learning effects perspective has been studied using the NHPP software. The log type hazard function applied to distribution was based on finite failure NHPP. Software error detection techniques known in advance, but influencing factors for considering the errors found automatically and learning factors, by prior experience, to find precisely the error factor setting up the testing manager are presented comparing the problem. As a result, the learning factor is greater than autonomous errors-detected factor that is generally efficient model could be confirmed. This paper, a failure data analysis of applying using time between failures and parameter estimation using maximum likelihood estimation method, after the efficiency of the data through trend analysis model selection were efficient using the mean square error and $R^2$(coefficient of determination).

• Journal of Korea Water Resources Association
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• v.55 no.10
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• pp.843-854
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• 2022

For the rip current warning system to reduce rip-current accidents, the implementation method producing the risk index was modified. To produce fast response from the warning system based on real-time observations, the method employed the numerical results (i.e., rip current likelihoods according to the possible scenario) obtained in advance. In this study, instead of using the empirical curve-fitting functions of the previous method, the present modification utilized two-dimensional distributions (i.e., wave height and period, wave height and tidal elevation, wave height and direction, wave height and spreading of frequency-directional spectrum) of rip current likelihoods stacked in a database of the system. The wave and tidal observations in 2021 at the Haeundae coast were applied to the modified system, and its performances at several real events recorded in CCTV images were presented.

• Environmental and Resource Economics Review
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• v.17 no.4
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• pp.845-873
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• 2008

This study estimates the VSL(value of a statistical life) as well as the WTP(willingness to pay) for mortality risk reduction using sample selection model with data on liver cancer examination which is associated with little possibility of multi-purpose(i.e. joint production) in averting behavior. The marginal benefits of mortality risk reduction are estimated by applying for household production function model with medical expense and the time required for medical examination of liver cancer. Individuals are more likely to take liver cancer test if they are male, older, higher educated, those with spouse, smoker, more income of household, and more anxious about their health. The costs of liver cancer examination are statistically significantly affected with expected signs by size of mortality risk reduction, sex, period of eduction, those with spouse, and household income. The marginal effect of mortality risk reduction owing to taking liver cancer examination is estimated at 321,097 won. The costs of liver cancer examination are increased by 905 won with more one year of education period and by 1,743 won with more one million won in household income. On liver cancer examination, male spends more 12,310 won than female and those with spouse pay more 7,969 won than those without spouse. Therefore the VSL from mortality risk reduction due to liver cancer examination is 321.10 million won at mean size of mortality risk reduction and mean cost of liver cancer examination. The results of sensitivity tests on costs and effects of liver cancer test shows that the VSLs are estimated in a range from 160.55 million won to 642.19 million won.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10b
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• pp.571-574
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• 2006

Dependent type은 유리수, 리스트 함수, 행렬 곱 등 여러 가지 타입들의 제약 사항들을 충실히 표현하는 데에 필수적이기 때문에 이를 지원하는 타입 시스템을 탑재한 언어를 새로 개발하거나 기존 언어의 다른 특성들을 활용하여 이를 모의(simulate)하려는 시도가 다각도로 진행되고있으며, Haskell 타입 레벨 프로그래밍도 이런 모의 기법 중 하나다. 기존 타입 레벨 프로그래밍은 변별력의 손실이 없는 대신 이로 인해 관련 함수들의 타입이 복잡해지거나 확정하기 어려워지는 경우가 많아서 잘못된 프로그램을 작성할 위험 부담이 커진다. 실제로 dependent type이 필요한 경우들 중에는 매우 간단한 변별력만을 요구하는 경우가 많으므로, 귀납적 자료형을 이진 추상화하여 일부 변별력을 포기하는 대신 상대적으로 간단하게 dependent type과 관련 함수들의 타입을 확정하는 간소화된 타입 레벨 프로그래밍 기법을 제안한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.289-291
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• 2013

건물일체형풍력시스템에서는 윈드가이드를 비롯한 주면 형상이 풍력터빈 주변의 풍속 등과 같은 유동특성에 중요한 영향을 미친다. 이 연구에서는 sech 함수를 이용한 새로운 충돌위험도 평가법에서 피항구역의 문턱값을 결정하는 방법을 분석하고 실제 상황에 적용 가능한 식을 개발하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.392-395
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• 2009

응답면 기법을 활용하여 댐구조물과 같은 사회간접자본 시설물의 파괴확률을 구할 수 있다. 본 위험성 평가과정에서 응답면기법으로 구성한 한계상태 방정식을 유전자알고리즘의 적합도 방정식으로 사용하면, 핵심타입이나 지반종류, 지반다짐정도 등의 입력설계변수의 최적화 과정 속도를 더욱 신속화 시킬 수 있다. 제안된 응답면 기법과 유전자알고리즘의 복합해석기법은 신뢰성기반 최적화프로그램으로 기존의 유전자알고리즘의 수렴속도를 더욱 빠르게 하여주고, 특히 입력변수의 상하한계가 불확실한 경우에도 만족스러운 수렴성을 보장하여준다. 한계상태 방정식의 목표신뢰도 지수를 변화시켜면 해당하는 입력변수의 최적값을 출력하여주므로, 입력변수의 제약조건에 가격함수와 같은 가중치를 벌칙함수로 부여하면 가격최적화 프로그램으로 작용하게 되며, 시설물 운영자에게는 목표신뢰도에 대한 유지관리 기법과 정도를 의사결정 할 수 있도록 하여주는 기능을 가지게 된다. 조사된 많은 댐구조물의 파괴모드가 시간에 독립적으로 시공중 또는 시공완료 후 5년이내에 다수 발생하는바, 파괴모드를 조사하고 중요한 파괴모드인 파이핑 현상에 대해서 파괴확률을 계산하고 최적유지관리를 위한 개선된 유전자알고리즘 최적화 연산을 수행하였다. 기존 댐구조물과 같이 설계변수와 하중의 변동성을 알기가 어려운 경우에 유지관리비용 최소화를 위해서 본 제안 프로그램의 확장된 버젼은 중요한 기준을 제시하여줄 것으로 기대한다.

• Water for future
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• v.26 no.2
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• pp.89-97
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• 1993

For the system benefit optimization by considering risk or reliability from a multiple reservoir system using the Monte Carlo technique, many stochastically generated inflow series have to be used for the system analysis. In this study, the stochastically generated inflow series for the multiple reservoir system operation are preprocessed according to the considered system objectives and operating time periods. Through this procedure, several representative inflow series which have discrete probability levels and operation horizons are selected among the thousands of generated inflows. Then a deterministic optimization technique is applied to the power energy estimation from the Han River Reservoirs System which considers five reservoirs in the study. It took much lower computational requirements then using the original Monte Carlo Technique, even though estimated result was almost similar.