• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3787-3800
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• 2023

Reactivity Initiated Accident (RIA) scenarios require special attention using advanced simulation techniques due to their complexity and importance for nuclear power plant (NPP) safety. While the conservative approach has traditionally been used for safety analysis, it may lead to unrealistic results which calls for the use of best estimate plus uncertainty (BEPU) approach, especially with the current advances in computational power which makes the BEPU analysis feasible. In this work an Uncontrolled Control Element Assembly (CEA) Withdrawal at Full Power accident scenario is analyzed using the BEPU approach by loosely coupling the thermal hydraulics best-estimate system code (RELAP5/SCDAPSIM/MOD3.4) to the statistical analysis software (DAKOTA) using a Python interface. Results from the BEPU analysis indicate that a realistic treatment of the accident scenario yields a larger safety margin and is therefore encouraged for accident analysis as it may enable more economic and flexible operation.

• Asia Marketing Journal
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• 제26권1호
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• pp.11-22
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• 2024

In the uncertainty fueled by the COVID-19 pandemic, mergers and acquisitions (M&As) have emerged as key strategic responses by firms. This study explores the impact of M&As on acquirers' firm value, utilizing a firm-level panel dataset from SDC Platinum. Empirical evidence recognizes the potential negative impact of transaction value in M&As and the pandemic's effect on market uncertainty that may occasionally exacerbate the adverse influence on acquirers' firm value. The findings indicate that effective marketing strategies, such as enhancing consumer awareness through increasing advertising expenditures, can counterbalance these influences, particularly during uncertain times. This study accentuates the importance of adaptability and a responsive marketing approach in managing M&As during a global crisis. It provides valuable perspectives on consumer awareness in strategic decision-making, offering insights for both academic and business communities and focusing on actionable strategies for navigating the global market turmoil transformed by COVID-19.

• 대한원격탐사학회지
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• 제39권3호
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• pp.355-361
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• 2023

지구 표면에 대한 정보는 기상 및 대기 역학의 이해나 인간을 포함한 동물에 큰 영향을 미치는 극한 열현상에 대응함에 있어서 핵심적인 지구 물리량이다. 지구 영역에 대한 온도를 추정하기 위하여 위성에 탑재된 열적외 센서가 널리 활용되어 왔는데, 정밀한 활용을 위해서는 온도 추정 과정의 불확도에 대한 이해가 선행되어야 한다. 하지만 온도추정 불확도에 영향을 미치는 많은 요소 중에서 한반도 주변의 환경 하에서의 온도추정 알고리즘의 불확도 산정에 대한 연구는 미미하였다. 본 연구에서는 한반도 주변의 대기 및 해양 조건하에서 범용성이 높은 single-channel 알고리즘의 불확도를 추정하는 연구를 수행하였다. 알고리즘의 입력자료로 필요한 재분석자료(reanalysis)의 영향성을 평가하기 위하여 두 가지의 재분석자료, 즉 fifth generation of European Centre for Medium-Range Weather Forecasts reanalysis of the global climate and weather (ERA5)와 Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2)를 사용하였고, 복사전달모델은 MODerate resolution atmospheric TRANsmission (MODTRAN)을 사용하였다. MODTRAN 모의와 온도 추정 정확도 검증에 사용되는 현장 관측 수온은 한반도 인근 해역에 위치한 해양 기상 부이(buoy)로부터 획득했다. 실험 결과, 알고리즘 불확도는 대기 수증기량에 따라서 선형에 가깝게 증가하는 것을 확인하였고, 가장 건조한 조건에서는 약 0.35K 그리고 평균적으로 0.45K 가량의 불확도가 발생함을 확인하였다. 이러한 결과는 재분석자료의 종류에 상관없이 유사하게 도출되어 알고리즘이 가지는 순수한 불확도라고 추정할 수 있었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.134-134
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• 2022

Streamflow forecasting plays a crucial role in water resource control, especially in highly urbanized areas that are very vulnerable to flooding during heavy rainfall event. In addition to providing the accurate prediction, the evaluation of effects and importance of the input predictors can contribute to water manager. Recently, machine learning techniques have applied their advantages for modeling complex and nonlinear hydrological processes. However, the techniques have not considered properly the importance and uncertainty of the predictor variables. To address these concerns, we applied the GA-BART, that integrates a genetic algorithm (GA) with the Bayesian additive regression tree (BART) model for hourly streamflow forecasting and analyzing input predictors. The Jungrang urban basin was selected as a case study and a database was established based on 39 heavy rainfall events during 2003 and 2020 from the rain gauges and monitoring stations. For the goal of this study, we used a combination of inputs that included the areal rainfall of the subbasins at current time step and previous time steps and water level and streamflow of the stations at time step for multistep-ahead streamflow predictions. An analysis of multiple datasets including different input predictors was performed to define the optimal set for streamflow forecasting. In addition, the GA-BART model could reasonably determine the relative importance of the input variables. The assessment might help water resource managers improve the accuracy of forecasts and early flood warnings in the basin.

• 한국콘텐츠학회논문지
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• 제6권3호
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• pp.75-84
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• 2006

인터넷은 다양한 정보를 소비자에게 제공하며 구매의사결정을 지원하는 중요한 매체이다. 특히 인터넷의 상호작용적 특성과 정보 생성자라는 소비자 역할의 변화는 구매행동에서 구전커뮤니케이션을 통해 교환되는 정보의 효용가치를 증가시키는 계기가 되었다. 본 연구의 목적은 온라인 쇼핑환경에서 구전커뮤니케이션을 통한 정보의 지각된 유용성에 미치는 영향요인을 규명하고, 지각된 유용성과 구전커뮤니케이션스타일과의 관계를 규명하는 것이다. 분석결과 선택 불확실성, 지식불확실성, 지각된 위험 등의 요인이 커뮤니케이션을 통한 정보의 유용성에 유의미한 영향을 미쳤으나 관계불확실성은 영향을 주지 않았다. 또한 소비자 간에 교환되는 정보의 유용성을 높게 지각할수록 수동적인 커뮤니케이션보다는 상호작용적 커뮤니케이션 방식을 선택하는 것으로 조사되었다.

• Earthquakes and Structures
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• 제10권1호
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• pp.141-161
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• 2016

In seismic fragility and risk analysis, the definition of structural limit state (LS) capacities is of crucial importance. Traditionally, LS capacities are defined according to design code provisions or using deterministic pushover analysis without considering the inherent randomness of structural parameters. To assess the effects of structural randomness on LS capacities, ten structural parameters that include material strengths and gravity loads are considered as random variables, and a probabilistic pushover method based on a correlation-controlled Latin hypercube sampling technique is used to estimate the uncertainties in LS capacities for four typical reinforced concrete frame buildings. A series of ten LSs are identified from the pushover curves based on the design-code-given thresholds and the available damage-controlled criteria. The obtained LS capacities are further represented by a lognormal model with the median $m_C$ and the dispersion ${\beta}_C$. The results show that structural uncertainties have limited influence on $m_C$ for the LSs other than that near collapse. The commonly used assumption of ${\beta}_C$ between 0.25 and 0.30 overestimates the uncertainties in LS capacities for each individual building, but they are suitable for a building group with moderate damages. A low uncertainty as ${\beta}_C=0.1{\sim}0.15$ is adequate for the LSs associated with slight damages of structures, while a large uncertainty as ${\beta}_C=0.40{\sim}0.45$ is suggested for the LSs near collapse.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2004년도 춘계공동학술대회 논문집
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• pp.479-482
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• 2004

This paper proposes a new framework for variability analysis in QFD. The proposed framework considers the uncertainty of the information contained in the house of quality chart and analyzes the variability resulting in the outcome. A new framework provides a dominance index and a difference index for each pairwise ECs. The indices are helpful to evaluate priorities of each pairwise EC.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 가을 학술발표회논문집
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• pp.224-231
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• 1993

This paper is concerned with the influence of changes in stochastic parameters of the important resistance variables such as the strength modelling parameter and material and geometric properties, on the system safety level of TLP structures. The effect of parameters governing the post-ultimate behaviour is also addressed. An extended incremental load method is employed for the present study, which has been successfully applied to the system reliability analysis of continuous structures. The Hutton Field TLP and its one variant called herein TLP-B, are chosen as TLP models in this paper. The results of several parameteric studies lead to useful conclusions relating to the importance of reducing uncertainties in strength formulae and relating the importance of component post-ultimate behaviour to the systems reliability of such structures.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.139-141
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• 2016

콜센터에 국가표준(KS)이 도입되면서 고객들이 질 좋은 서비스를 이용할 수 있을 것으로 기대된다. 본 연구는 Fuzzy AHP(Analytic Hierarchy Process) 기법을 이용하여 콜센터 서비스 인증 심사기준의 상대적 중요도를 평가하기 위해서 수행되었다. Fuzzy AHP는 AHP 기법에 Fuzzy 집합 이론을 결합한 것으로, 의사결정과정에서 발생할 수 있는 애매모호함과 불확실성을 해결하기 위하여 제시된 방법이다. 본 연구에서 제시한 평가방법론은 현재 국가적으로 추진되고 있는 KS 서비스 인증제도에서도 응용될 수 있을 것으로 본다.

• Geomechanics and Engineering
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• 제29권3호
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• pp.331-338
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• 2022

Face stability analyses provides the most probable failure mechanisms and the understanding about parameters that need to be considered for the evaluation of ground movements caused by tunneling. After the Upper Bound Method (UBM) solution which can consider the influence of seepage forces and depth-dependent effective cohesion is verified with the numerical experiments, the probabilistic model is proposed to calculate the unbiased limiting tunnel collapse pressure. A reliability analysis of a shallow circular tunnel driven by a pressurized shield in a frictional and cohesive soil is presented to consider the inherent uncertainty in the input parameters and the proposed model. The probability of failure that exceeding a specified applied pressure at the tunnel face is estimated. Sensitivity and importance measures are computed to identify the key parameters and random variables in the model.