• Nuclear Engineering and Technology
• /
• 제46권5호
• /
• pp.619-632
• /
• 2014

The Best Estimate Plus Uncertainty (BEPU) method has been widely used to evaluate the uncertainty of a best-estimate thermal hydraulic system code against a figure of merit. This uncertainty is typically evaluated based on the physical model's uncertainties determined by expert judgment. This paper introduces the application of data assimilation methodology to determine the uncertainty bands of the physical models, e.g., the mean value and standard deviation of the parameters, based upon the statistical approach rather than expert judgment. Data assimilation suggests a mathematical methodology for the best estimate bias and the uncertainties of the physical models which optimize the system response following the calibration of model parameters and responses. The mathematical approaches include deterministic and probabilistic methods of data assimilation to solve both linear and nonlinear problems with the a posteriori distribution of parameters derived based on Bayes' theorem. The inverse problem was solved analytically to obtain the mean value and standard deviation of the parameters assuming Gaussian distributions for the parameters and responses, and a sampling method was utilized to illustrate the non-Gaussian a posteriori distributions of parameters. SPACE is used to demonstrate the data assimilation method by determining the bias and the uncertainty bands of the physical models employing Bennett's heated tube test data and Becker's post critical heat flux experimental data. Based on the results of the data assimilation process, the major sources of the modeling uncertainties were identified for further model development.

• 한국정보시스템학회지:정보시스템연구
• /
• 제17권3호
• /
• pp.25-37
• /
• 2008

In a fault tree analysis, an uncertainty importance measure is often used to assess how much uncertainty of the top event probability (Q) is attributable to the uncertainty of a basic event probability ($q_i$), and thus, to identify those basic events whose uncertainties need to be reduced to effectively reduce the uncertainty of Q. For evaluating the measures suggested by many authors which assess a percentage change in the variance V of Q with respect to unit percentage change in the variance $v_i$ of $q_i$, V and ${\partial}V/{\partial}v_i$ need to be estimated analytically or by Monte Carlo simulation. However, it is very complicated to analytically compute V and ${\partial}V/{\partial}v_i$ for large-sized fault trees, and difficult to estimate them in a robust manner by Monte Carlo simulation. In this paper, we propose a method for evaluating the measure using discretization technique and Monte Carlo simulation. The proposed method provides a stable uncertainty importance of each basic event.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제19권1호
• /
• pp.26-33
• /
• 2014

Uncertainty associated with a sampling method is very high in evaluating the degree of site contamination; therefore, such uncertainty affects the reliability of precise investigation and remediation verification. In particular, in evaluating a site for a small-sized filling station, underground utilities, such as connection pipes and oil storage tanks, make grid-unit sampling impossible and the resulting increase in uncertainty is inevitable. Accordingly, this study quantified the uncertainty related to the evaluation of the degree of contamination by total petroleum hydrocarbon and by benzene, toluene, ethylene, and xylene. When planning a grid aimed at detecting a hot spot, major factors that influence the increase in uncertainty include grid interval and the size and shape of the hot spot. The current guideline for soil sampling prescribes that the grid interval increase in proportion to the area of the evaluated site, but this heightens the possibility that a hot spot will not be detected. In evaluating a site, therefore, it is crucial to estimate the size and shape of the hot spot in advance and to establish a sampling plan considering a diversity of scenarios.

• 한국유체기계학회 논문집
• /
• 제17권2호
• /
• pp.24-29
• /
• 2014

In general, a large-capacity axial flow fan is used for industrial processes or ventilation in a social overhead capital infrastructure. The main characteristics of the large axial-flow fan need a lot of electrical power consumption and operate 24 hours a day, 365 days a year. Since the large axial flow fan consumes several hundreds to thousands kW per hour, both manufacturer and consumer are struggling to select high efficiency products for saving energy and reducing operation cost. Therefore, the performance testing should be accurately conducted in experimental equipments. The performance estimation and uncertainty of measurement of the axial-flow fan gathered from the result from nozzle shaped testing equipments certified with ANSI/AMCA standard and duct shaped testing equipment under the same experimental condition. The experimental results from both facilities have maximum 17% differences in performance evaluation and uncertainty of measurement. As considering that the differences, it is doubt about the reliability of testing result. The test was repeated with the specific term during 12 months because it is important to fully reflect the real conditions and to decide the repeatability of data. The evaluation of duct type testing facilities was failed to get an uncertainty measure. Testing results were previously published. As a series of previous paper, axial fan (∅1690 mm) and duct type testing facilities were fabricated. The purpose of fabricating testing equipment was testing an uncertainty measurement under the controlled environments.

• 터널과지하공간
• /
• 제13권2호
• /
• pp.87-99
• /
• 2003

지구통계학적 접근법은 지역화 변수를 모델링하기 위한 방법으로서, 제한된 공간 샘플 자료로부터 불확실성을 평가하고 추정하기 위한 효과적인 방법론이다. 본 연구에서는 추정문제에서 사용할 수 있는 크리깅 기법과 지구통계학적 시뮬레이션에 대해 이론적으로 비교 검토하였다. 시뮬레이션과 달리, 크리깅은 자료의 통계량과 공간 구조를 유지할 수 없으며, 불확실성의 측도를 제공하기 어렵다. 따라서, 본 연구에서는 불확실성 평가를 위한 지구통계학적 시뮬레이션의 과정을 제시하였으며, RMR의 공간 분포 파악 및 그 불확실성의 평가 과정을 현장 적용을 통해 살펴보았다. 지구통계학적 시뮬레이션은 지반공학적 변수들의 공간 불확실성을 정량적으로 표현할 수 있는 효과적인 방법임을 확인할 수 있었다. 따라서, 지구통계학적 시뮬레이션 결과는 다양한 지질학적조건 및 시공 계약 조건하에서 설계자의 의사결정을 위한 유용한 정보로서 활용할 수 있다.

• 한국태양에너지학회 논문집
• /
• 제31권1호
• /
• pp.51-58
• /
• 2011

The energy makes the basic element which improves the quality of life with motive power of industry and life. However, using the fossil fuel resources was restricted through it's abuse and exhaustion, and that cause a global warming resultingly. According to the reason, the world increased the interest that are stability and use of new and renewable energy which is clean energy with environment. Therefore, the property data of new and renewable is needed for developing and supplying the energy. In other words, the data of new and renewable energy becomes the standards for supply and evaluation of new and renewable energy with development of industry and technology. Also, the necessity came to the fore as the reference and standards of new and renewable energy data. Therefore, in this study, we evaluate and collect the solar radiation data as the new and renewable data and process the collected data through the standards for valuation. We evaluate uncertainty with standards which are NREL, WMO, and GUM. Whereby the data becomes reference standards data and gains the credibility. For the reliability data, we correct the measuring instrument with correction period. Using the DQMS and SERI QC, we efficiently manage and evaluate the solar radiation data. As a result, we evaluate uncertainty as 1,120 case about 16 area. we achieve credibility of data from evaluated solar radiation data and provide an accurate information to user. The annual average of horizontal radiation presents between 1,484 and 4,577, then the uncertainty evaluates from 163 to 453. The error of uncertainty presents smaller than the measurement values. So, we judge a credibility of data by expression of reliability quantitatively. In additional, the reference standards data which is possible to approach anywhere will be used for the supporting related industry and policy making.

• 한국음향학회지
• /
• 제28권7호
• /
• pp.668-673
• /
• 2009

본 논문에서는 최소값 제어 음성 존재 부정확성의 추정기법을 이용한 음성 향상 기법을 제안한다. 기존의 음성 존재 부정확성 추정기법에서는 간단한 a posteriori SNR에 근거하여 프레임, 채널마다 다른 a priori음성 부재 확률값을 결정하여 음성 부재 확률 계산에 적용하였다. 본 논문에서 제안된 알고리즘은 기존 음성 존재 부정확성 추적방법과는 달리 최소값 제어방법을 이용하여 주파수성분별 최소값에 근거한 강인한 a priori음성 부재 확률값 추정방법을 통해 음성 부재 확률에 적용하여 음성을 향상시킨다. 제안된 음성 향상 기법은 ITU-T P.862 perceptual evaluation of speech quality (PESQ)를 이용하여 평가하였고 기존의 음성 존재 부정확성 추적방법보다 향상된 결과를 나타내었다.

• KIEAE Journal
• /
• 제15권6호
• /
• pp.5-10
• /
• 2015

Purpose: To evaluate the economic performance of grid-connected photovoltaic system in residential house, household electricity bill policy of Korea Electric Power Corporation (KEPCO) must be applied precisely, and market tendency and uncertainty of system also need to be considered. In this study, to evaluate the economic feasibility of PV system, we measured PV power generation and electricity consumption of six of Green home in Daejeon through web based remote monitoring system. Method: We applied Monte-Carlo simulation based on life cycle cost analysis, to reflect an uncertainty of main factor in economic feasibility evaluation of photovoltaic system. Result: First, with deterministic analysis, the difference of NPV of cumulative financial savings among households varied from -3,310 ~ 24,170 thousand won, portraying notably big range. Also the possibility of getting the same result was 50% when applying uncertainty. Second, the higher electricity consumption is, the more economic feasibility of photovoltaic system increases because KEPCO uses progressive taxation in household electricity bill policy. Third, The contribution to variance of electricity price increases in NPV varied from 98.5% to 99.9%. While the inflation rate and annual degradation contributed very little to none.

• 한국지반환경공학회 논문집
• /
• 제16권5호
• /
• pp.13-25
• /
• 2015

This paper proposes an extended model evaluation method that considers not only the model performance but also the model structure and parameter uncertainties in hydrologic modeling. A simple reservoir model (SFM) and distributed kinematic wave models (KWMSS1 and KWMSS2 using topography from 250-m, 500-m, and 1-km digital elevation models) were developed and assessed by three evaluative criteria for model performance, model structural stability, and parameter identifiability. All the models provided acceptable performance in terms of a global response, but the simpler SFM and KWMSS1 could not accurately represent the local behaviors of hydrographs. Moreover, SFM and KWMSS1 were structurally unstable; their performance was sensitive to the applied objective functions. On the other hand, the most sophisticated model, KWMSS2, performed well, satisfying both global and local behaviors. KMSS2 also showed good structural stability, reproducing hydrographs regardless of the applied objective functions; however, superior parameter identifiability was not guaranteed. A number of parameter sets could result in indistinguishable hydrographs. This result indicates that while making hydrologic models complex increases its performance accuracy and reduces its structural uncertainty, the model is likely to suffer from parameter uncertainty.

• 방사성폐기물학회지
• /
• 제6권2호
• /
• pp.141-145
• /
• 2008

후행 핵연료주기 경제성 평가는 추정 비용의 불확실성, 평가 대상기간의 장기성, 적용 할인율에 따른 계산결과의 변동성 등 많은 불확실성을 내포하고 있기 때문에 평가기관 또는 평가자에 따라 그 결과가 서로 상이하다. 본고에서는 지금까지 수행된 주요 경제성 평가 연구들을 조사/분석하여 그 특징과 한계를 알아봄으로써 현재 국내에서 추진되고 있는 사용후핵연료 공론화 및 후행 핵연료주기 정책 연구 추진에 기초자료로 활용될 수 있도록 하고자 하였다. 분석 결과 사용후핵연료 재활용 옵션에 비해 직접처분 옵션이 유리하나, 입력 자료로 사용된 파라미터 값에 따라 결과의 불확실성이 많이 나타나 이 부분에 대한 추가적인 연구가 필요하다는 사실을 알 수 있었다.