• Honam Mathematical Journal
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• v.30 no.2
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• pp.391-397
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• 2008

The existence of solutions and the occurrence of a Hopf bifurcation for the free boundary problems with Pushchino dynamics was shown in [1]. In this paper, we shall show a Hopf bifurcation occurs for the free boundary for Pushchino dynamics with a spatial dependency.

• Journal of the Korean association of regional geographers
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• v.16 no.5
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• pp.610-622
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• 2010

The proportion of overweight and obese individuals in the United States has been continuously increasing up to recently. Many studies related to obesity have concentrated on jurisdictional levels of aggregation, making it very difficult to dearly illustrate at risk regions. In other words, little research has been conducted in relation to spatial patterns considering spatial dependency and heterogeneity by spatial autocorrelation models over space. In response, this research analyzes spatial patterns between overweight/obesity and risk factors, such as high blood pressure and diabetes, over space. Specifically, the Moran''s I and Geary''s C will be conducted for global and local measures. What is more, the Ordinary Least Square (OLS) linear regression and Geographically Weighted Regression methods will be applied to identify spatial dependency and spatial heterogeneity. Data provided by the Behavioral Risk Factor Surveillance System (BRFSS) have Body-Mass Index (BMI) rates, containing 4 rates of under, healthy, overweight, and obesity. In addition, high blood pressure and diabetes rates in the United States will be used as independent variables. Lastly, we are confident that this research will be beneficial for a decision maker to make a prevention plan for obesity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.5
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• pp.1881-1903
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• 2015

With the fast-developing of mobile terminals, positioning techniques based on fingerprinting method draws attention from many researchers even world famous companies. To conquer some shortcomings of the existing fingerprinting systems and further improve its performance, we propose a radio map building and updating technique, which is able to customize the spatial and temporal dependency of radio maps. The method includes indoor propagation and penetration modeling and the analysis of human traffic. Based on the combination of Ray-Tracing Algorithm, Finite-Different Time-Domain and Rough Set Theory, the approach of indoor propagation modeling accurately represents the spatial dependency of the radio map. In terms of temporal dependency, we specifically study the factor of moving people in the interest area. With measurement and statistics, the factor of human traffic is introduced as the temporal updating component. We improve our existing indoor positioning system with the proposed building and updating method, and compare the localization accuracy. The results show that the enhanced system can conquer the influence caused by moving people, and maintain the confidence probability stable during week, which enhance the actual availability and robustness of fingerprinting-based indoor positioning system.

• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1287-1300
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• 2017

Based on the observation that ignoring the angle dependency of multigroup resonance cross sections within a fuel pellet would result in nontrivial underestimation of the spatial self-shielding of flux, a parametrized spectral superhomogenization (SPH) factor library (PSSL) method is developed as a practical means of resolving the problem. Region-wise spectral SPH factors are calculated by the normal and transport corrected SPH iterations after ultrafine group slowing down calculations over various light water reactor pin-cell configurations. The parametrization is done with fuel temperature, U-238 number density, fuel radius, moderator source represented by ${\Sigma}_{mod}V_{mod}$, and the number density ratio of resonance nuclides to that of U-238 in a form of resonance interference correction factors. The parametrization is successful in that the root mean square errors of the interpolated SPH factors over the fuel regions of various pin-cells are within 0.1%. The improvement in reactivity error of the PSSL method is shown to be superior to that by the original SPH method in that the reactivity bias of -200 pcm to -300 pcm vanishes almost completely. It is demonstrated that the environment effect takes only about 4% in the reactivity improvement so that the pin-cell based PSSL method is effective in the assembly problems.

• Journal of the Korean Data and Information Science Society
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• v.27 no.5
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• pp.1203-1214
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• 2016

Obesity is a risk factor for various diseases as well as itself a disease and associated with socioeconomic factors. The obesity proportion has been increasing in Korea over about 15 years so that investigation of the socioeconomic factors related with obesity is important in terms of preventation of obesity. In particular, the association between obesity and socioeconomic status varies with gender and has spatial dependency. In the paper, we estimate the effects of socioeconomic factors on obesity proportion by gender, considering the spatial correlation. Here, a conditional autoregressive model under the Bayesian framework is used in order to take into account the spatial dependency. For the real applicaiton, we use the obestiy proportion dataset at 25 districts of Seoul in 2010. We compare the proposed spatial model with a non-spatial model in terms of the goodness-of-fit and prediction measures so the spatial model performs well.

• Journal of Korean Association for Spatial Structures
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• v.15 no.3
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• pp.103-110
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• 2015

Various hybrid dampers have been developed as increasing tall buildings in Korea. To minimize the installment space and cost, the new hybrid friction damper was developed using friction components. It is composed of two one-nodal rotary frictional components and a slotted bolted frictional connection. Because of these components, hybrid friction damper can be activated by building movements due to lateral forces such as a wind and earthquake. In this paper, displacement amplitude dependency tests were carried out to evaluate on the structural performance and the multi-slip mechanism of the hybrid damper. Test results show that the multi-slip mechanism is verified and friction coefficients are increasing as displacement amplitudes are increasing.

• Journal of Korean Association for Spatial Structures
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• v.15 no.4
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• pp.73-80
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• 2015

The new rotary friction damper was developed using several two-nodal rotary frictional components with different clamping forces. Because of these components, the rotary friction damper can be activated by building movements due to lateral forces such as a wind and earthquake. In this paper, various dependency tests such as displacement amplitude, forcing frequency and long term cyclic loading were carried out to evaluate on the structural performance and the multi-slip mechanism of the new damper. Test results show that the multi-slip mechanism is verified and friction coefficients are dependent on displacement amplitute and forcing frequency except long term cyclic loading.

• Journal of Korean Association for Spatial Structures
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• v.23 no.4
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• pp.51-58
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• 2023

In this study, the displacement dependence, strength, and energy dissipation capacity of the steel rod damper were evaluated. The test variables are the number of steel rod dampers and the lateral deformation prevention details. From test results, it was evaluated that the displacement dependence conditions in the structural design code were satisfied. The maximum strength and energy dissipation capacity increased linearly as the number of steel rod increased. In addition, the maximum strength and energy dissipation capacity were evaluated by more than 20 times increased by using of the lateral deformation prevention details.

• Journal of Korean Society of Rural Planning
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• v.22 no.4
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• pp.139-146
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• 2016

Aging phenomenon is an important issue in Korea national policy. This aging phenomenon depends on the social and environmental characteristics of regions. Also aging phenomenon and regional characteristics have spatial dependency. The purpose of this study is to discover the spatial changes in aging population rate and to find local factors of regional aging phenomenon considering spatial autocorrelation. For spatial analysis of ageing phenomenon, local Moran's I and Geographically Weighted Regression (GWR) were applied. As the results, the most significant changes of aging phenomenon appeared between 2000 and 2005, and most of hot-spot regions (aged regions) were distributed in Jullanam-do and Jullabuk-do. The results of GWR (R-square: 0.681) shows that total fertility rate, the number of doctor per 1,000 people and forest area rate have positive relation with aging population rate, but the number of private academy per 1,000 people has negative relation.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.2
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• pp.20-41
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• 2023

Recently, urban shrinkage due to low birth rate and aging population and the decline of local cities are causing a new urban problem of empty houses. This study examines the distribution of vacant homes using spatial panel data collected from 2015 to 2019 at local administraitve districts and estimates the factors of vacant house occurrence using a spatial panel model considering spatio-temporal dependency. As a result, the spatio-temporal dependence of vacant houses was identified and it was estimated using spatial panel model not OLS model. Based on the spatial panel model, it was found that the most influential factor in the occurrence of vacant houses was the housing-related factor. This result shows that policy considerations for housing supply are necessary for the management of vacant housing as well as population movement and poor infrastructure.