• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1627-1631
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• 2003

Molecular modeling was performed to comprehend the chiral recognition of ${\alpha}$-methoxy-${\alpha}$-trifluoromethylphenylacetic acid (MTPA) enantiomers by cyclomaltoheptaose (${\beta}$-cyclodextrin,${\beta}$-CD) and 6-amino-6-deoxy-cyclomaltoheptaose (am-${\beta}$-CD). Monte Carlo (MC) docking coupled to constant temperature molecular dynamics (MD) simulations was applied to the investigation for the ${\alpha}$-methoxy-${\alpha}$-trifluoromethylphenylacetic acid complexation with two different CDs in terms of the relative distribution of the interaction energies. The calculated results are finely correlated with the experimental observations in chiral recognition thermodynamics. Am-${\beta}$-CD as a host showed the superior enantio-discrimination ability to the native ${\beta}$-CD where the amino group of am-${\beta}$-CD was critically involved in enhancing the ability of chiral discrimination via the Coulombic interaction with MTPA.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1241-1250
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• 2019

This study mainly focused on the neutronics modeling of bubbles in bubbly flow in boiling water reactors. The bubble, ring and homogenous models were used for radial void fraction distribution. Effect of the bubble and ring models on the infinite multiplication factor and two-group flux distribution was investigated by comparing with the homogenous model. Square pitch unit cell geometry was used in the calculations. In the bubble model, spherical and non-spherical bubbles at random positions, sizes and shapes were produced by Monte Carlo method. The results show that there are significant differences among the proposed models from the viewpoint of physical interaction mechanism. For the fully-developed bubbly flow, $k_{inf}$ is overestimated in the ring model by about $720{\pm}6pcm$ with respect to homogeneous model whereas underestimated in the bubble model by about $-65{\pm}9pcm$ with a standard deviation of 15 pcm. In addition, the ring model shows that the coolant must be separated into regions to properly represent the radial void distribution. Deviations in flux distributions principally occur in certain regions, such as corners. As a result, the bubble model in modeling the void fraction can be used in nuclear engineering calculations.

• Advances in Computational Design
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• v.4 no.2
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• pp.91-118
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• 2019

Every year, many people are severely injured or lose their lives in accidents such as fire, chemical spill, public pandemonium, school shooting, and workplace violence. Research indicates that the fate of people in an emergency situation involving one or more hazards depends not only on the design of the space (e.g., residential building, industrial facility, shopping mall, sports stadium, school, concert hall) in which the incident occurs, but also on a host of other factors including but not limited to (a) occupants' characteristics, (b) level of familiarity with and cognition of the surroundings, and (c) effectiveness of hazard intervention systems. In this paper, we present EVAQ, a simulation framework for modeling large crowd evacuation by taking into account occupants' behaviors and interactions during an emergency. In particular, human's personal (i.e., age, gender, disability) and interpersonal (i.e., group behavior and interactions) attributes are parameterized in a hazard-impacted environment. In addition, different hazard types (e.g., fire, lone wolf attacker) and propagation patterns, as well as intervention schemes (simulating building repellent systems, firefighters, law enforcement) are modeled. Next, the application of EVAQ to crowd egress planning in an airport terminal under human attack, and a shopping mall in fire emergency are presented and results are discussed. Finally, a validation test is performed using real world data from a past building fire incident to assess the reliability and integrity of EVAQ in comparison with existing evacuation modeling tools.

• Earthquakes and Structures
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• v.23 no.6
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• pp.549-580
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• 2022

This paper assesses the influences of modeling assumptions and uncertainties on the performance of the non-linear finite element (FE) model updating procedure and model clustering method. The results of a shaking table test on a four-story steel moment-resisting frame are employed for both calibrations and clustering of the FE models. In the first part, simple to detailed non-linear FE models of the test frame is calibrated to minimize the difference between the various data features of the models and the structure. To investigate the effect of the specified data feature, four of which include the acceleration, displacement, hysteretic energy, and instantaneous features of responses, have been considered. In the last part of the work, a model-based clustering approach to group models of a four-story frame with similar behavior is introduced to detect abnormal ones. The approach is a composition of property derivation, outlier removal based on k-Nearest neighbors, and a K-means clustering approach using specified data features. The clustering results showed correlations among similar models. Moreover, it also helped to detect the best strategy for modeling different structural components.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.427-438
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• 2023

Thermodynamic sorption modeling can enhance confidence in assessing and demonstrating the radionuclide sorption phenomena onto various mineral adsorbents. In this work, Ca-montmorillonite was successfully purified from Bentonil-WRK bentonite by performing the sequential physical and chemical treatments, and its geochemical properties were characterized using X-ray diffraction, Brunauer-Emmett-Teller analysis, cesium-saturation method, and controlled continuous acid-base titration. Further, batch experiments were conducted to evaluate the adsorption properties of Cs(I) and Sr(II) onto the homoionic Ca-montmorillonite under ambient conditions, and the diffuse double layer model-based inverse analysis of sorption data was performed to establish the relevant surface reaction models and obtain corresponding thermodynamic constants. Two types of surface reactions were identified as responsible for the sorption of Cs(I) and Sr(II) onto Ca-montmorillonite: cation exchange at interlayer site and complexation with edge silanol functionality. The thermodynamic sorption modeling provides acceptable representations of the experimental data, and the species distributions calculated using the resulting reaction constants accounts for the predominance of cation exchange mechanism of Cs(I) and Sr(II) under the ambient aqueous conditions. The surface complexation of cationic fission products with silanol group slightly facilitates their sorption at pH > 8.

• The Journal of the Korea Contents Association
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• v.17 no.12
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• pp.493-504
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• 2017

The purpose of this study is to investigate the differences between low-income and middle-income groups with respect to how family factors intervene with friendship factors to influence adolescent depression. In order to do this, we selected 1,552 adolescents (246 from low-income group and 1276 from middle-income group) from 1 panel of the 6th Korean Children & Youth Panel Survey and conducted multiple-group analysis for structural equation modeling. The results are as follows. Firstly, there were no direct effects of parenting style on adolescent depression for the low-income group, whereas effects were found to be significant for the middle-income group. Secondly, parenting style had a greater influence on friendship factors for the low-income group than the middle-income group. Thirdly, the influence of friendship factors on depression was much more negative for the middle-income group than the low-income group. Fourthly, it was found that parenting style had greater intervention effects on friendship factors influencing adolescent depression for the middle-income group as compared to the low-income group. However, intervention effects were not found for peer alienation.

• Journal of Digital Convergence
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• v.13 no.8
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• pp.267-279
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• 2015

The study aimed to examine the longitudinal relationship between addictive use of mobile phones and learning activities for elementary school students and to analyze (1)temporal changes of the addictive use of mobile phones and learning activities, (2)temporal relationship between them, and (3)multiple and complex group analysis across gender on the relationship. For the study, 3-year longitudinal data(2010-2012) of the Korean Children and Youth Panel Survey and autoregressive cross-lagged modeling were used. The findings showed that the addictive use of mobile phones and learning activities had a significant positive effect on the future selves of children over time. The addictive use of mobile phones influenced positively subsequent learning activities, but, the learning activities did not affect the addictive use of mobile phones. Further, there were no significant gender differences in the longitudinal relationship. The study provided the useful data to make guidelines on how to protect mobile phone addiction for elementary school students.

• Journal of the Korean Data and Information Science Society
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• v.26 no.1
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• pp.123-139
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• 2015

The purpose of this study is to analyze the effect of the parent's socioeconomic status to the academic achievement, together with the mediation effect of the private education expenditure. The structural equation modeling (SEM) method is used with the survey of private education expenditures data collected by Statistics Korea in 2011. In SEM, the multi-group effect is also analyzed for gender, region and school level. The analysis results show that the high socioeconomic status of parent tends to increase the private education expenditures but does not affect the academic achievement, and there are the significant multi-group effect for gender, region, and school level.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.574-578
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• 2003

There are so many methods to estimate the groundwater recharge. These methods can be categorized into four groups. First groupis related to the water balance analysis, second group is concerned with baseflow/springflow recession, and third group is interested in some types of tracers; environmental tracers and/or temperature profile. The limitation of these types of methods is that the estimated results of recharge are presented in the form of an average over some time period. Forth group has a little different approach. They use the time series data of hydraulic head and specific yield evaluated from field test, and the results of estimation are described in the sequential form. But their approach has a serious problem. The estimated results in forth typeof methods are generally underestimated because they cannot consider the discharge phase of water table fluctuation coupled with the recharge phase. Ketchum el. at. (2000) proposed calibrated method, considering recharge- and discharge-coupled water table fluctuation. But the dischargeis considered just as the areal average with discharge rate. On the other hand, there are many methods to estimate the source wavelet with observed data set in geophysics/signal processing and geophysical methods are rarely applied to the estimation of groundwater recharge. The purpose this study is the evaluation of the applicability of one of the geophysical method in the estimation of sequential recharge rate. The applied geophysical method is called minimum entropy deconvolution (MED). For this purpose, numerical modeling with linearized Boussinesq equation was applied. Using the synthesized hydraulic head through the numerical modeling, the relative sequenceof recharge is calculated inversely. Estimated results are very concordant with the applied recharge sequence. Cross-correlations between applied recharge sequence and the estimated results are above 0.985 in all study cases. Through the numerical test, the availability of MED in the estimation of the recharge sequence to groundwater was investigated

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.4
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• pp.435-448
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• 2021

This study describes the depth and straight motion control performance depending on control surface combinations of a supercavitating underwater vehicle. When an underwater vehicle experiences supercavitation, friction resistance can be minimized, thus achieving the effect of super-high-speed driving. Six degrees of freedom modeling of the underwater vehicle are performed and the guidance and control loops are designed with not only a cavitator and an elevator, but also a rudder and a differential elevator to improve the stability of the roll and yaw axis. The control performance based on the combination of control surfaces is analyzed by the root-mean-square error for keeping depth and straight motion.