• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.1-9
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• 2010

Most of shear wall structures require openings in shear walls and thus shear walls are linked by floor slabs or coupling beams resulting in the coupled shear wall structures. When these structures are subjected to seismic excitations, excessive shear forces are induced in coupling beams. Accordingly, brittle failure of coupling beams may occur or shear walls may yield first. To avoid this problem, damping devices can be installed in coupling beams. It can increase the vibration control effect and improve the seismic resistance performance of the coupled shear wall structure by avoiding stress concentration and the brittle failure of coupling beams. Based on this background research, an LRB (lead rubber bearing) was introduced in the middle of the coupling beam in this study and the authors investigated the seismic response control effect and stress distribution of the proposed system. To this end, a modeling technique that can effectively predict the structural behavior of coupled shear wall structures has been proposed. With this proposed technique, time history analyses of the example coupled shear wall structure subjected to seismic excitation were performed and the vibration control effects of the seismic responses were investigated.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.315-327
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• 2016

Background: This study evaluated the atmospheric dispersion of radioactive material according to local weather conditions and emission conditions. Materials and Methods: Local weather conditions were defined as 8 patterns that frequently occur around the Kori Nuclear Power Plant and emission conditions were defined as 6 patterns from a combination of emission rates and the total number of particles of the $^{137}Cs$, using the WRF/HYSPLIT modeling system. Results and Discussion: The highest mean concentration of $^{137}Cs$ occurred at 0900 LST under the ME4_1 (main wind direction: SSW, daily average wind speed: $2.8ms^{-1}$), with a wide region of its high concentration due to the continuous wind changes between 0000 and 0900 LST; under the ME3 (NE, $4.1ms^{-1}$), the highest mean concentration of $^{137}Cs$ occurred at 1500 and 2100 LST with a narrow dispersion along a strong northeasterly wind. In the case of ME4_4 (S, $2.7ms^{-1}$), the highest mean concentration of $^{137}Cs$ occurred at 0300 LST because $^{137}Cs$ stayed around the KNPP under low wind speed and low boundary layer height. As for the emission conditions, EM1_3 and EM2_3 that had the maximum total number of particles showed the widest dispersion of $^{137}Cs$, while its highest mean concentration was estimated under the EM1_1 considering the relatively narrow dispersion and high emission rate. Conclusion: This study showed that even though an area may be located within the same radius around the Kori Nuclear Power Plant, the distribution and levels of $^{137}Cs$ concentration vary according to the change in time and space of weather conditions (the altitude of the atmospheric boundary layer, the horizontal and vertical distribution of the local winds, and the precipitation levels), the topography of the regions where $^{137}Cs$ is dispersed, the emission rate of $^{137}Cs$, and the number of emitted particles.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.9-15
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• 2017

Background: The purpose of this study is to assign an appropriate density to virtual phantom for 2D diode array detector with different dose calculation algorithms to guarantee the accuracy of patient-specific QA. Materials and Methods: Ten VMAT plans with 6 MV photon beam and ten VMAT plans with 15 MV photon beam were selected retrospectively. The computed tomography (CT) images of MapCHECK2 with MapPHAN were acquired to design the virtual phantom images. For all plans, dose distributions were calculated for the virtual phantoms with four different materials by AAA and AXB algorithms. The four materials were polystyrene, 455 HU, Jursinic phantom, and PVC. Passing rates for several gamma criteria were calculated by comparing the measured dose distribution with calculated dose distributions of four materials. Results and Discussion: For validation of AXB modeling in clinic, the mean percentages of agreement in the cases of dose difference criteria of 1.0% and 2.0% for 6 MV were $97.2%{\pm}2.3%$, and $99.4%{\pm}1.1%$, respectively while those for 15 MV were $98.5%{\pm}0.85%$ and $99.8%{\pm}0.2%$, respectively. In the case of 2%/2 mm, all mean passing rates were more than 96.0% and 97.2% for 6 MV and 15 MV, respectively, regardless of the virtual phantoms of different materials and dose calculation algorithms. The passing rates in all criteria slightly increased for AXB as well as AAA when using 455 HU rather than polystyrene. Conclusion: The virtual phantom which had a 455 HU values showed high passing rates for all gamma criteria. To guarantee the accuracy of patent-specific VMAT QA, each institution should fine-tune the mass density or HU values of this device.

• Journal of Korea Game Society
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• v.10 no.3
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• pp.61-71
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• 2010

This study looks into the usage pattern in online games based on genres and socio-demographic characteristics. Compared to the prior studies that adopted survey as their main research method, this study has analyzed the actual data of game login records and adopted parametric modeling and mathematical approach. In terms of the socio-demographic characteristics, the following facts were confirmed: men > women by gender, students > white-collars > housewives > blue-collars > self-employed > jobless(etc.) by occupation, college graduates > K-12 students > high-school graduates > undergrads & grads by academic background, 3∼5 million > 1∼3 million > over 5 million > less than 1 million by income levels, and not married > married by marital status. In terms of genres, the population of the players is in the order of web board games, RPG, action/racing/shooting, and sports. The RPG game is confirmed to have a higher level of MCR (Max Concurrent User Ratio) than any other genres. On the other hand, the hypothesis on the difference in Repeated Use Ratio according to genres is rejected. This study has also confirmed that interactions exist between gender and age; genre and gender; genre and age among online game users, and conducted post-hoc analysis about those interactions.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.12
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• pp.5287-5294
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• 2016

Background: Breast cancer is a worldwide public health concern and is the most prevalent type of cancer in women in the United States. This study concerned the best fit of statistical probability models on the basis of survival times for nine state cancer registries: California, Connecticut, Georgia, Hawaii, Iowa, Michigan, New Mexico, Utah, and Washington. Materials and Methods: A probability random sampling method was applied to select and extract records of 2,000 breast cancer patients from the Surveillance Epidemiology and End Results (SEER) database for each of the nine state cancer registries used in this study. EasyFit software was utilized to identify the best probability models by using goodness of fit tests, and to estimate parameters for various statistical probability distributions that fit survival data. Results: Statistical analysis for the summary of statistics is reported for each of the states for the years 1973 to 2012. Kolmogorov-Smirnov, Anderson-Darling, and Chi-squared goodness of fit test values were used for survival data, the highest values of goodness of fit statistics being considered indicative of the best fit survival model for each state. Conclusions: It was found that California, Connecticut, Georgia, Iowa, New Mexico, and Washington followed the Burr probability distribution, while the Dagum probability distribution gave the best fit for Michigan and Utah, and Hawaii followed the Gamma probability distribution. These findings highlight differences between states through selected sociodemographic variables and also demonstrate probability modeling differences in breast cancer survival times. The results of this study can be used to guide healthcare providers and researchers for further investigations into social and environmental factors in order to reduce the occurrence of and mortality due to breast cancer.

• Korean Journal of Social Welfare Studies
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• no.39
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• pp.315-342
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• 2008

The aim of this study was to examine growth trajectories of delinquent behaviors during adolescence. In addition, the effects of protective and risk factors that might account for individual difference in the level of delinquent behaviors and in the rate of change were examined. Four waves of data in the Korea Youth Panel Survey(KYPS) were used to analyze the linear growth modeling. The sample consisted of 3346 adolescents who were assessed at 4 measurement waves with approximately 1-year intervals. The results showed significant individual differences in both final level of delinquent behaviors and in the rate of change across 3 measurement occasions. Adolescent gender, family's socioeconomic background predicted the final level and the rate of change of delinquent behaviors. The protective effects of positive parenting and self-control were significantly associated with problem behaviors and the risk effects of the association with deviant peers and negative stigma were significant on the final level of delinquency. Self-control and deviant peer affiliation had differential influences over time significantly. Practice and policy implications as well as further research topic were discussed in the light of searching for important factors in preventing adolescent problem behaviors.

• Journal of Digital Convergence
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• v.19 no.9
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• pp.283-288
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• 2021

Due to the 4th Industrial Revolution and the Digital Revolution, many changes are being made in the manufacturing method and structure in the field of plastic arts and crafts. Therefore, in this study, we tried to present a new work method suitable for this era by effectively utilizing the digital technology called 3D printer. For this study, first of all, the theoretical background of 3D printing technology was understood, and prior studies on the use cases of 3D printing technology were summarized. Based on this, three types of craft molds were produced using a 3D printer. As a result of the study, there were characteristics that appear respectively depending on the thickness or overlapping of the craft molds using 3D printing technology. First, in the case of the thickness of the craft molds, the thinner the strength, the weaker the strength, but there was an advantage in that it was easier to take out the contents of the molds. However, it was determined that the thick craft molds was stable to contain the dense and heavy material. Second, in the case of overlapping of craft molds, the advantages of both thin and thick molds were obtained as a result of using a double-layered molds. However, there was a disadvantage that the surface of the contents taken out was not smooth, so that post-processing was necessary. In future research, I hope to deal with the material of the filament used in 3D printers.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.1
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• pp.140-153
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• 2019

Cloase-range image information from drones and ground-based camera has been frequently used in the field of disaster mitigation with 3D modeling and mapping. In addition, the utilization of virtual reality(VR) is being increased by implementing realistic 3D models with the VR technology simulating disaster circumstances in large scale. In this paper, we created a VR training program by extracting realistic 3D models from close-range images from unmanned aircraft and digital camera on hand and observed several issues occurring during the implementation and the effectiveness in the case of a VR application in training for disaster mitigation. First of all, we built up a scenario of disaster and created 3D models after image processing with the close-range imagery. The 3D models were imported into Unity, a software for creation of augmented/virtual reality, as a background for android-based mobile phones and VR environment was created with C#-based script language. The generated virtual reality includes a scenario in which the trainer moves to a safe place along the evacuation route in the event of a disaster, and it was considered that the successful training can be obtained with virtual reality. In addition, the training through the virtual reality has advantages relative to actual evacuation training in terms of cost, space and time efficiencies.

• Journal of Ecology and Environment
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• v.43 no.1
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• pp.43-60
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• 2019

Background: Tropical montane forests played an important role in the provision of ecosystem services. The intense degradation and deforestation for the need of agricultural land expansion result in a significant decline of forest cover. However, the expansion of agricultural land did not completely destruct natural forests. There remain forests inaccessible for agricultural and grazing purpose. Studies on these forests remained scant, motivating to investigate biomass and soil carbon stocks. Data of biomass and soils were collected in 80 quadrats ($400m^2$) systematically in 5 forests. Biomass and disturbance gradients were determined using allometric equation and disturbance index, respectively. The regression modeling is employed to explore the spatial distribution of carbon stock along disturbance and environmental gradients. Correlation analysis is also employed to identify the relation between site factors and carbon stocks. Results: The result revealed that a total of 1655 individuals with a diameter of ${\geq}5cm$, representing 38 species, were measured in 5 forests. The mean aboveground biomass carbon stocks (AGB CS) and soil organic carbon (SOC) stocks at 5 forests were $191.6{\pm}19.7$ and $149.32{\pm}6.8Mg\;C\;ha^{-1}$, respectively. The AGB CS exhibited significant (P < 0.05) positive correlation with SOC and total nitrogen (TN) stocks, reflecting that biomass seems to be a general predictor of SOCs. AGB CS between highly and least-disturbed forests was significantly different (P < 0.05). This disturbance level equates to a decrease in AGB CS of 36.8% in the highly disturbed compared with the least-disturbed forest. In all forests, dominant species sequestrated more than 58% of carbon. The AGB CS in response to elevation and disturbance index and SOC stocks in response to soil pH attained unimodal pattern. The stand structures, such as canopy cover and basal area, had significant positive relation with AGB CS. Conclusions: Study results confirmed that carbon stocks of studied forests were comparable to carbon stocks of protected forests. The biotic, edaphic, topographic, and disturbance factors played a significant variation in carbon stocks of forests. Further study should be conducted to quantify carbon stocks of herbaceous, litter, and soil microbes to account the role of the whole forest ecosystem.

• Korean Journal of Environmental Agriculture
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• v.38 no.1
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• pp.34-37
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• 2019

BACKGROUND: A region can be divided into agroclimatic zones based on homogeneity in weather variables that have greatest influence on crop growth and yield. The agro-climatic zone has been used to identify yield variability and limiting factors for crop growth. This study was conducted to classify agro-climatic zones in the state of Mato Grosso in Brazil for predicting crop productivity and assessing crop suitability etc. METHODS AND RESULTS: For agro-climatic zonation, monthly mean temperature, precipitation, and solar radiation data from Global Modeling and Assimilation Office (GMAO) of National Aeronautics and Space Administration (NASA, USA) between 1980 and 2010 were collected. Altitude and vegetation fraction of Brazil from Weather Research and Forecasting (WRF) were also used to classify them. The criteria of agro-climatic classification were temperature in the hottest month ($30^{\circ}C$), annual precipitation (600 mm and 1000 mm), and altitude (200 m and 500 m). The state of Mato Gross in Brazil was divided into 9 agro-climatic zones according to these criteria by using matrix classification method. CONCLUSION: The results could be useful as information for estimating agro-meteorological characteristics and predicting crop development and crop yield in the state of Mato Grosso in Brazil.