• Journal of Environmental Science International
• /
• v.25 no.1
• /
• pp.67-83
• /
• 2016

In order to improve the prediction of the regional air quality modeling in the Seoul metropolitan area, a sensitivity analysis using two PBL and microphysics (MP) options of the WRF model was performed during four seasons. The results from four sets of the simulation experiments (EXPs) showed that meteorological variables (especially wind field) were highly sensitive to the choice of PBL options (YSU or MYJ) and no significant differences were found depending on MP options (WDM6 or Morrison) regardless of specific time periods, i.e. day and night, during four seasons. Consequently, the EXPs being composed of YSU PBL option were identified to produce better results for meteorological elements (especially wind field) regardless of seasons. On the other hand, the accuracy of all simulations for summer and winter was somewhat lower than those for spring and autumn and the effect according to physics options was highly volatile by geographical characteristics of the observation site.

• Journal of the Korean Geographical Society
• /
• v.38 no.6
• /
• pp.906-921
• /
• 2003

This paper discusses the price effects of local growth controls on the housing markets of California jurisdictions in the late 1980s empirically. Particularly, based on spatial econometric modeling, the study focuses on the homebuilding constrained by growth controls which is one of the price effects. The modeling produces the California-wide generalizable results, differentiates among the individual effects of various growth controls on homebuilding, and covers spatial effects. Thereby, this study intends to supplement the existing work on the price effects of growth controls. The modeling results find that restrictive residential zoning had the effect of significantly restricting housing construction in the late 1980s. On the other hand, urban growth boundaries had the effect of accommodating homebuilding. Population growth or housing permit caps and adequate public facility ordinances had no significant effects on housing construction.

• Journal of The Korean Association of Information Education
• /
• v.26 no.5
• /
• pp.439-448
• /
• 2022

This study aims to search for education-related datasets provided by public data portals and examine what data types are constructed through classification using topic modeling methods. Regarding the data of the public data portal, 3,072 cases of file data in the education field were collected based on the classification system. Text mining analysis was performed using the LDA-based topic modeling method with stopword processing and data pre-processing for each dataset. Program information and student-supporting notifications were usually provided in the pre-classified dataset for education from the data portal. On the other hand, the characteristics of educational programs and supporting information for the disabled, parents, the elderly, and children through the perspective of lifelong education were generally indicated in the dataset collected by searching for education. The results of data analysis through this study show that providing sufficient educational information through the public data portal would be better to help the students' data science-based decision-making and problem-solving skills.

• Journal of Digital Contents Society
• /
• v.18 no.6
• /
• pp.1143-1150
• /
• 2017

The objective of this study is to examine the trends in information systems research. The abstracts of 1,245 articles were extracted from three leading Korean journals published between 2002 and 2016: Asia Pacific Journal of Information Systems, Information Systems Review, and The Journal of Information Systems. Time series analysis and topic modeling methods were implemented. The topic modeling results showed that the research topics were mainly "systems implementation", "communication innovation", and "customer loyalty". The time series regression results indicated that "customer satisfaction", "communication innovation", "information security", and "personal privacy" were hot topics, and on the other hand, "system implementation" and "web site" were the least popular. This study also provided suggestions for future research.

• Geophysics and Geophysical Exploration
• /
• v.22 no.2
• /
• pp.56-61
• /
• 2019

In this paper, we studied efficient modeling strategies when we simulate the 3D time-domain acoustic wave propagation using a cell-based finite difference method which can handle the variations of both P-wave velocity and density. The standard finite difference method assigns physical properties such as velocities of elastic waves and density to grid points; on the other hand, the cell-based finite difference method assigns physical properties to cells between grid points. The cell-based finite difference method uses average physical properties of adjacent cells to calculate the finite difference equation centered at a grid point. This feature increases the computational cost of the cell-based finite difference method compared to the standard finite different method. In this study, we used additional memory to mitigate the computational overburden and thus reduced the calculation time by more than 30 %. Furthermore, we were able to enhance the performance of the modeling on several media with limited density variations by using the cell-based and standard finite difference methods together.

• The Journal of the Korea Contents Association
• /
• v.22 no.1
• /
• pp.86-98
• /
• 2022

This study explored the agenda of conservative and liberal media in reporting COVID-19, and observed the effects of each media's partisan agenda-setting on the public with the same political orientation. To this end, researchers collected 5,286 articles on COVID-19 from five newspapers, and analyzed the survey data of 1,067 respondents. Next, the researchers extracted main agenda using LDA topic modeling and analyzed the correlation between newspapers' agenda and survey respondents' agenda. As results, 15 topics such as infection, vaccine, and economic crisis appeared as the media agenda, and the difference in major agenda between conservative and liberal media was found. On the other hand, the conservative media exerted an agenda-setting influence not only on the conservatives but also on the liberals, but the liberal media did not have a significant influence on the liberals. This study contributes to the methodological expansion of agenda-setting research by introducing a new way to confirm the effectiveness of agenda-setting by combining topic modeling and survey.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.3
• /
• pp.185-198
• /
• 2017

Since the year 2000, the growth rate of domestic manufacturing has declined and the sales and employment have decreased. Major developed countries have established a variety of strategies to strengthen their manufacturing competitiveness, and promote manufacturing innovation through the convergence of technology and ICT. The key to manufacturing innovation is to reduce the time and cost for developing new products using modeling and simulation (M&S) technology in the product design stage. M&S industries, which belong to the top sector of the industry value chain, have a huge ripple effect across other industries. On the other hand, the competitiveness of the domestic M&S industry is weak compared to developed countries and even the definition and classification of domestic M&S companies have not been made. In this paper, by analyzing the Korea Standard Industry Classification (KSIC), five fine industry classifications included in M&S service companies were derived. In addition, the 307 M&S service companies were derived in accordance with the selection procedure of 3 steps from the 11,822 related companies. To analyze the capabilities of domestic M&S service companies, the current status of the selected M&S service companies was investigated. Considering the Korean economy's high dependence on the manufacturing industry, strengthening the competitiveness of manufacturing industry is required by enhancing the capacities and building an ecosystem in domestic M&S services for future sustainable economic growth.

• The Korean Journal of Health Service Management
• /
• v.7 no.4
• /
• pp.65-79
• /
• 2013

The purpose of this study was to reveal relationship between positive illusions and oral health promotion behaviors. Positive illusions was composed of positive self-perception, exaggerated sense of personal control, and unrealistic optimism. We thought these factors affect to the oral health behaviors. For this study, 307 collegians in Ulsan, Yangsan are participated in this study. The data was subjected to confirmatory factor analysis and structural equation modeling with SPSS 18.0, AMOS 18.0. In conclusion, we obtained the next results. First, positive illusions has a statistically significant with oral health promotion in correlation analysis(p<0.05). Second, Structural equation modeling fit index was well fitted as $X^2$=100, df=112, P=0.893, RMR=0.021, GFI=0.969, AGFI=0.943. Only positive self-perception and exaggerated sense of control has a statistically significant(P<0.05). Third, the group of the highest positive illusions has a statistically significant in all factors(P<0.05), the other hand, the group of the lowest positive illusions has not statistically significant in all factors(P>0.05). So, as this results we concluded that the self-confident or activated persons were very well performed in oral health promotion behaviors.

• Transactions of Materials Processing
• /
• v.20 no.5
• /
• pp.377-386
• /
• 2011

During stamping processes, the air trapped between sheet metal and the die cavity can be highly compressed and ultimately reduce the shape accuracy of formed panels. To prevent this problem, vent holes and passages are sometimes drilled into the based on expert experience and know-how. CAE can be also used for analyzing the air behavior in die cavity during stamping process, incorporating both elasto-plastic behavior of sheet metal and the fluid dynamic behavior of air. This study presents sheet metal forming simulation combined simultaneously with simulation of air behavior in the die cavity. There are three approaches in modeling of air behavior. One is a simple assumption of the bulk modulus having a constant pressure depending on volume change. The next is the use of the ideal gas law having uniform pressure and temperature in air domain. The third is FPM (Finite point method) having non-uniform pressure in air domain. This approach enables direct coupling of mechanical behavior of solid sheet metal and the fluid behavior of air in sheet metal forming simulation, and its result provides the first-hand idea for the location, size and number of the vent holes. In this study, commercial software, PAM-$STAMP^{TM}$ and PAM-$SAFE^{TM}$, were used.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.2
• /
• pp.586-593
• /
• 2017

Modeling busbar distribution system as a transmission line is an important subject of power line communication in the smart grid concept. This requires extraction of busbar RLGC parameters, accurately. In this study, a comparison is made between conventional and modified method for the aspect of optimum RLGC parameters extraction in the 1 MHz to 50 MHz frequency band. The usefulness of these methods is shown both in time and frequency-domain analysis. The frequency-domain analyzes show that the inherent power of modified method can eliminate the errors especially due to the discontinuities arise in conventional method. This makes the modeling approach of modified method more advantageous for the busbars due to its robustness against disturbances in the S-parameters measurements which cannot be eliminated with the calibration procedure. On the other hand, time-domain simulations show that the transmission line representation of the modified method is closer to physical reality by handling causality issues.