• Nuclear Engineering and Technology
• /
• v.55 no.10
• /
• pp.3787-3800
• /
• 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
• /
• v.26 no.1
• /
• pp.11-22
• /
• 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.

• Korean Journal of Remote Sensing
• /
• v.39 no.3
• /
• pp.355-361
• /
• 2023

Temperature of the Earth's surface is a crucial physical variable in understanding weather and atmospheric dynamics and in coping with extreme heat events that have a great impact on living organismsincluding humans. Thermalsensors on satellites have been a useful meansfor acquiring surface temperature information for wide areas on the globe, and thus characterization of its estimation uncertainty is of central importance for the utilization of the data. Among various factors that affect the estimation, the uncertainty caused by the algorithm itself has not been tested for the atmospheric environment of Korean vicinity. Thisstudy derivesthe uncertainty of the single-channel algorithm under the local atmospheric and oceanic conditions by using reanalysis data and buoy temperature data collected around Korea. Atmospheric profiles were retrieved from two types of reanalysis data, the fifth generation of European Centre for Medium-Range Weather Forecasts reanalysis of the global climate and weather (ERA5) and Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2) to investigate the effect of reanalysis data. MODerate resolution atmospheric TRANsmission (MODTRAN) was used as a radiative transfer code for simulating top of atmosphere radiance and the atmospheric correction for the temperature estimation. Water temperatures used for MODTRAN simulations and uncertainty estimation for the single-channel algorithm were obtained from marine weather buoyslocated in seas around the Korean Peninsula. Experiment results showed that the uncertainty of the algorithm varies by the water vapor contents in the atmosphere and is around 0.35K in the driest atmosphere and 0.46K in overall, regardless of the reanalysis data type. The uncertainty increased roughly in a linear manner as total precipitable water increased.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.134-134
• /
• 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.

• The Journal of the Korea Contents Association
• /
• v.6 no.3
• /
• pp.75-84
• /
• 2006

The internet has the capabilities of supporting and facilitating several forms of consumer interaction including one-to-one, one to many, or many-to-many interactions. Especially, previous studies revealed that the Online Word-of-Mouth communication is widely used as a source of customer's information seeking and purchase decision making. Even with this importance of the Online Word-of-Mouth communication on internet, few research has systematically addressed the issue. This study investigates the effect of interpersonal communication on consumers' information search activities and develops a model that depicts the key antecedents and mediating variables of interpersonal communication in internet shopping environment. The results are as follows: First, choice uncertainty, perceived risk, and knowledge uncertainty play an important role for perceived usefulness. Second, perceived usefulness has directly affected interactive communication of consumers' communication style. Thus, it is essential for internet companies to find ways to encourage their customers to engage in word-of-mouth communication.

• Earthquakes and Structures
• /
• v.10 no.1
• /
• pp.141-161
• /
• 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.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2004.05a
• /
• pp.479-482
• /
• 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.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1993.10a
• /
• pp.224-231
• /
• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2016.10a
• /
• pp.139-141
• /
• 2016

With the introduction of national standards (KS) for call centers, customers are expected to have access to better-quality services in the future. The purpose of this study is to evaluate the relative importance of certification criteria for call center services using the Fuzzy AHP(Analytic Hierarchy Process) approach. Fuzzy AHP is the combination of the fuzzy set theory and AHP to deal with the uncertainty or ambiguousness of the decision-making process. The evaluation method proposed in this study can be applied to the KS services certification promoted by government.

• Geomechanics and Engineering
• /
• v.29 no.3
• /
• pp.331-338
• /
• 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.