• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.10
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• pp.969-978
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• 2008

In a linear cascade experimental apparatus, when it adopts only few blades as well as satisfies the periodic condition between blades, it gives several advantages in experiment. In this study, wall design on a cascade experimental apparatus is conducted to obtain the periodic condition on two blades installed within a passage of which the width is double pitch. The Mach number difference on the blade surface obtained with the periodic and wall condition is chosen as an objective function, and twelve design variables which are related to the wall shape are selected. A wall shape is designed using a gradient-based optimization method. Adjustment of range and weighting function are applied to calculate the objective function to avoid unrealistic evaluation of the objective function. By applying these methods, the computed results show same flow structures obtained with the periodic condition.

• Communications for Statistical Applications and Methods
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• v.17 no.1
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• pp.55-66
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• 2010

Propensity score adjustment(PSA) has been suggested as approach to adjustment for volunteer internet survey. PSA attempts to decrease the biases arising from noncoverage and nonprobability sampling in volunteer panel internet surveys. Although PSA is an appealing method, its application for internet survey regarding Korea presidential election and its effectiveness is not well investigated. In this study, we compare the Ni Korea internet survey with the telephone survey conducted by MBMR and KBS for 2007 Korean presidential election. The result of study show that the accuracy of internet survey can be improved by using PSA. And it is critical to include covariates that highly related to the voting tendency and the role of nondemographic variables seems important to improving PSA for Korea presidential election prediction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1599-1605
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• 2014

This study aimed to identify the relationship between depression of the elderly and low back pain. Data were obtained from cross-sectional surveys conducted as a part of the Community Health Survey 2008. The final analysis included data from 3,647 of the 3,649 elderly participants (aged over 65 years), as 2 responses were excluded since they were inaccurate. Data were analyzed with SPSS for Windows (ver. 19.0), using a Rao-Scott ${\chi}^2$-test and Logistic regression by applying a proper weighting. The significance threshold was set as p<0.05. Factors related to the depression of the elderly were low back pain, subjective health status, average sleep duration. Further, depression score was 1.38 times higher in elderly adults with low back pain than elderly adults without low back pain. In order to decrease depression of the elderly with low back pain the development of a program to decrease activities of daily living discomfort and management of low back pain will need to be determined. It is considered necessary to conduct further study to follow through the analysis of the various variables by applying them to the elderly with low back pain and depression.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.4
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• pp.3-12
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• 2011

Understanding of water sediment trends is an important part of water quality monitoring. Water quality variables change over time and space, and cannot be modeled or explained clearly by either temporal or spatial analysis alone. This research analysed the trends of temperature, pH levels and dissolved oxygen levels based on the sediment records and spatial data obtained in Lower Mekong Basin (LMB) during 1985-2005. Our aim is to evaluate spatio-temporal trends and graphical analyses using an Inverse Distance Weighting (IDW) interpolation method. The main results from this research can be summarized as follows. The maximum temperature and pH have been stable during the study period and the maximum dissolved oxygen has been increasing gradually until 2002. The minimum pH and dissolved oxygen have been changing in an unsteady trend during the period. A spatial analysis shows that the water temperature in this region has been increasing over time. The pH trend shows that it is decreasing during 1993-2005. Dissolved oxygen concentration has been increasing from 1989 onwards and stays in that track.

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.43-53
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• 2010

This study investigates a design optimization of a rotating two-pass rectangular cooling channel with staggered arrays of pin-fins. The radial basis neural network method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The ratio of the diameter to height of the pin-fins and the ratio of the streamwise spacing between the pin-fins to height of the pin-fin are selected as design variables. The optimization problem has been defined as a minimization of the objective function, which is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Results are presented for streamlines, velocity vector fields, and contours of Nusselt numbers, friction coefficients, and turbulent kinetic energy. These results show how fluid flow in a two-pass square cooling channel evolves a converted secondary flows due to Coriolis force, staggered arrays of pin-fins, and a $180^{\circ}$ turn region. These results describe how the fluid flow affects surface heat transfer. The Coriolis force induces heat transfer discrepancy between leading and trailing surfaces, having higher Nusselt number on the leading surface in the second pass while having lower Nusselt number on the trailing surface. Dean vortices generated in $180^{\circ}$ turn region augment heat transfer in the turning region and in the upstream region of the second pass. As the result of optimization, in comparison with the reference geometry, thermal performance of the optimum geometry shows the improvement by 30.5%. Through the optimization, the diameter of pin-fin increased by 14.9% and the streamwise distance between pin-fins increased by 32.1%. And, the value of objective function decreased by 18.1%.

• Water Engineering Research
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• v.6 no.2
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• pp.39-48
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• 2005

The Brazos River is one of the longest rivers contained entirely in the state of Texas, flowing over 700 miles from northwest Texas to the Gulf of Mexico. Today, the Brazos River Authority and Texas Commission on Environmental Quality interest in drought protection plan, waterpower project, and allowing the appropriation of water system-wide and water right within the Brazos River Basin to meet water needs of customers like farmers and local civilians in the future. Especially, this purpose of this paper primarily intended to provide the data for the engineering guidelines and make easily geological mapping tool. In the Brazos River basin, many stream-flow gage station sites are not working, and they can not provide stream-flow data sets enough for development of the Probable Maximum Flood (PMF) for use in the evaluation of proposed and existing dams and other impounding structures. Integrated GIS-Spatial Interpolation (GIS-SI) tool are composed of two parts; (1) extended GIS technique (new making interface for hydrological regionalization parameters plus classical GIS mapping skills), (2) Spatial Interpolation technique using weighting factors from kriging method. They are obtained from the relationship among location and elevation of geological watershed and existing stream-flow datasets. GIS-SI technique is easily used to compute parameters which get drainage areas, mean daily/monthly/annual precipitation, and weighted values. Also, they are independent variables of multiple linear regressions for simulation at un gaged stream-flow sites. In this study, GIS-SI technique is applied to the Brazos river basin in Texas. By assuming the ungaged flow at the sites of Palo Pinto, Bryan and Needville, the simulated daily/monthly/annual time series are compared with observed time series. The simulated daily/monthly/annual time series are highly correlated with and well fitted to the observed times series.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.279-286
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• 2020

In this study, we investigate the accuracy of higher order derivatives in the moving least square (MLS) difference method. An interpolation function is constructed by employing a Taylor series expansion via MLS approximation. The function is then applied to the mixed variational theorem in which the displacement and stress resultants are treated as independent variables. The higher order derivatives are evaluated by solving simply supported beams and cantilevers. The results are compared with the analytical solutions in terms of the order of polynomials, support size of the weighting function, and number of nodes. The accuracy of the higher order derivatives improves with the employment of the mean value theorem, especially for very high-order derivatives (e.g., above fourth-order derivatives), which are important in a classical asymptotic analysis.

• YAKHAK HOEJI
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• v.58 no.2
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• pp.99-106
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• 2014

This study explores the prescribing pattern of generic drugs and the relationship between socio-demographic factors and the use of generics in South Korea. The analysis was based on claims data of 2011 from Korean National Health Insurance. We examined utilization, costs, and market share of oral preparations by original and generic product. Multiple logistic regression was performed to evaluate the predictive factors of generic use among multi-source medications. Generics accounted for 37~41% of utilization and 34~41% of costs in the insured market of oral preparations. In the generic market, costly generics made up about 58~61%, 56~66% of volume and value, respectively. Other things being equal, institutional factors affected generic use to the largest degree. The odds of having generics were 6 times higher in clinics, 4 times higher in hospitals, and 1.7 times higher in general hospitals than in teaching hospitals. Those in metropolitan or rural area were more likely to prescribe generics than those in the capital area. While generics were frequently prescribed for off-site pharmacy (OR=1.173), the odds of having generics was 0.88 after weighting the data by units prescribed. This study empirically presented the pattern of generic prescribing, confirming the widely accepted view that costly generics were more likely to be utilized in the Korean market. Up to two thirds of the generic market consisted of costly products. The strongest factors affecting generic use were institutional variables.

• Survey Research
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• v.11 no.1
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• pp.123-144
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• 2010

In new sample design for Korea Housing Survey to research about housing policy, total strata are forty five because individual results of sixteen regions are estimated. The sample size is determined by sample errors of several variables which are the living area, family income, householder income, and living expenses. The sample size of each region is determined by relative standard error of existing result, and the strata sample size is to use the square root proportion allocation. Enumeration districts are sampled by the probability proportion to size systematic sampling in proportion to the enumeration district size, and the systemic sampling to use assortment characteristics. We considered a new apartment complex because of variation reflections which are rebuilder and redevelopment of houses. To get estimators of mean and variance, we used the design weighting, non-response adjusting, and post-stratification. In order to consider estimation efficiency, we calculate the design effect using estimators of variance.

• Journal of Korean Biological Nursing Science
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• v.19 no.4
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• pp.215-226
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• 2017

Purpose: The purpose of this study was to investigate the effects of general, health, and alcohol-related characteristics on blood pressure and stress according to the Alcohol Use Disorders Identification Test (AUDIT). Methods: This was a descriptive study. From participants in the 2013 Korea National Health and Nutrition Examination Survey, 319 participants who responded to the survey when they were attending college or university were selected. Data were analyzed using the SPSS Win 23.0 program for composite sample data reflecting the composite design elements of stratification, colonization, and weighting. Results: Mean age of onset of alcohol drinking was $17.91{\pm}0.16$ years, the average AUDIT score was $7.56{\pm}0.41$, and 25 (9.1%) participants fell into the high-risk drinking group. In the high-risk AUDIT group, systolic blood pressure was influenced by age, gender, institution, health status, body mass index, and suicidal ideation, and the explanatory power of the model ($R^2$) was 75.0%. For diastolic blood pressure, institution and health status were the influential factors, and $R^2$ was 66.2%. Predictors of stress were health status, depression, and the age of onset of drinking, and $R^2$ was 57.2%. Conclusion: It was confirmed that the explanatory power of the variables in models of systolic and diastolic blood pressure and stress is greater in those with higher scores on AUDIT.