• The Korean Journal of Applied Statistics
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• v.29 no.5
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• pp.849-858
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• 2016

It is important to control confounding bias when estimating the causal effect of treatment in an observational study. We illustrated that the covariate selection in the causal inference is different from the variable selection in the ANCOVA model. We then investigated the three criteria of covariate selection for controlling confounding bias, which can be used when we have inadequate information to draw a complete causal graph. VanderWeele and Shpitser (2011) proposed one of them and claimed it was better than the other two. We show by example that their criterion also has limitations and some disadvantages. There is no clear winner; however, their criterion is better (if some correction is made on its condition) than the other two because it can remove the confounding bias.

• The Korean Journal of Health Service Management
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• v.5 no.2
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• pp.119-129
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• 2011

A researcher examined 158 medical technologists and 140 radiologists who are working at 9 general hospitals in Gyeongsangbuk-do area using structured questionnaire to find out degree of fatigue of health professionals, the primary factors that have effect on them, and actions to control their fatigue on December 1 through December 20, 2008. The average complaining rate of fatigue subjective symptom by syndromes was overall 17.24 points, and medical technologists scored 16.48 points while radiologists scored 18.09 points. There were significant difference in the average fatigue complaining score of both medical technologists and radiologists such as when the younger their age is, when they are single, when the lower their monthly salary is, when the shorter their total working period is, and when the current status is staff at work. As a result of multiple regression analysis which sets fatigue score as dependent variable, there were significant difference on both syndromes such as satisfaction on work, work stress, and sleeping condition. It was the highest on relaxation, which was 76.6%, among the 15 questions on actions to control fatigue, and the next was enough sleep and controlling stress. And the lowest was help from medical professionals, which was 7.3%. It was the highest on enough sleep, which was 1.98 points, and next was relaxation and controlling stress, and the lowest points were help from medical professionals and taking medicine in the effective score of fatigue control action. In consequence of research, it is necessary to develop program and health education to control health professionals' various fatigue such as stress management and sleeping, and it is considered to find out the plan about effective work system.

• Journal of the Korea Society of Computer and Information
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• v.26 no.8
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• pp.173-180
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• 2021

The purpose of the present study was to investigate the relationship between perceived parenting style and life satisfaction among adolescents transitioning from middle to high schools and to ascertain whether self-esteem functions as a mediating variable between the two aforementioned variables. Based on the results of literature review, a research model, in which there were perceived parenting style, self-esteem, and life satisfaction as latent variables, was designed. The current study analyzed the 6th and 7th wave data of the 4th grade panel of elementary school from the Korea Children and Youth Panel Survey (KCYPS). Major results were as follows. First, perceived democratic parenting style had a significant positive effect on life satisfaction whereas controlling parenting style did not have a significant impact on life satisfaction. Second, self-esteem partially mediated the effect of perceived democratic parenting style on life satisfaction. Third, self-esteem fully mediated the effect of perceived controlling parenting style on life satisfaction. Finally, implications and recommendations were provided to improve parenting style and to enhance self-esteem of adolescents experiencing school transitions.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.12 no.5
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• pp.39-53
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• 2017

The purpose of this study was to investigate the effects of the rural migration factors, degree of preparation for migration, lifestyle conditions and support policies reflected against the family satisfaction of the migration. In this study family factors were used as control variables. Independent variables for this study will consist of the factors of rural migration, the degree of preparation for migration, living conditions of the farmers and the support policies, where as the dependent variable is the satisfaction of migration with an adjusting factor of the family satisfaction which will be further analysed to identify its effects on the dependent variable. For this study, a questionnaire survey was conducted for the residents and 237 valid questionnaires were collected. Multiple regression analysis was performed based on the collected data where demographic attributes being the controlling variable, and regression analysis was performed for the adjusting variable of the family. As the economic factor increases, the level of satisfaction generated to be higher in rural migration. As for the degree of preparation, living condition and support policies resulted, great quantity of green nature, safety and agriculture startup support, respectively, indicated a positive effect to the satisfaction level of migration. From the results, adjustment effect of the family factors on the economic, nature, convenience and satisfaction of the migration have appeared. The conclusion of this study is that policy support, regional stability, and economic gain are the most important factors to increase satisfaction and to reduce re-migration rate to city.

• Journal of agricultural medicine and community health
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• v.22 no.1
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• pp.27-34
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• 1997

This study was performed to offer the fundamental data for preventing and controlling the cardiovascular diseases of rural community women. The number of 168 women aged 40 to 50s who live in Kumsan-gun, Chungnam were selected for analysis after medical examination by a Kumsan-gun health center during the period of November to December in 1996. Total cholesterol(TC), triglyceride(TG), high density lipoprotein cholesterol(HDL-C), blood pressure(BP), degree of obesity(BMI) and atherosclerosis index(AI) were measured and relation between these physical measurements to serum lipid levels were studied. The results were as follows; 1. Mean TC level, TG level, BP, BMI and AI were significantly increased with advancing age. 2. Mean TC level, TG level, BMI and AI of borderline BP group and hypertension group were significantly increased than those of normal BP group. 3. Mean TC level, TG level and AI of obesity group were significantly increased than those of normal BMI group. 4. Simple correlation analysis showed that the positive correlation between TC, TG, BP, BMI and AI, but the level of HDL-C was negative correlation with TG and AI. 5. In multiple regression analysis taking HDL-C level as the dependent variable and TG, TC, BP, BMI, Age AI as the independent variable, AI, TG, BMI, TC were significantly related to HDL-C.

• The Journal of Industrial Distribution & Business
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• v.11 no.1
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• pp.29-38
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• 2020

Purpose: Understanding which product types of overseas travel (free independent travel vs. package travel) consumers will choose is one of the key issues of marketing and consumer behavior in travel agency management. Prior studies on overseas travel type preferences mainly focused on comparing regional differences (e.g., Asian vs. Westerner, or Korean vs. Australian, or Korean vs. Japanese, or American, French, Italian vs. Japanese) influencing the choice of overseas travel type. Another researchers focused on comparing cultural differences (e.g., individualism vs. collectivism, or individualistic culture vs. collectivistic culture), subcultural difference (e.g., acculturation; Koreans living in Republic of Korea vs. Koreans living in Australia), travel lifestyle, and socio-demographics (e.g., age, gender, income level, education level, marital status, occupation etc.). However, there are few studies that identify individual psychological differences (i.e., individual psychological differences within the same culture) influencing the choice of overseas travel type. Self-construal is a psychological factors that greatly influences choice behavior. The purpose of this study was to examine the role of self-construal as an antecedent variable influencing choice of overseas travel product type. Research design, data and methodology: To achieve the purpose of this study, the questionnaire survey method was used. Self-construal items composed of independent self-construal items and interdependent self-construal items. Product types of overseas travel were free independent travel (FIT) type versus package travel type. In this study, the correlation coefficient between independent self-construal and interdependent self-construal was nonsignificant. It meant that the relationship between independent self-construal and interdependent self-construal was orthogonal. Therefore it was analyzed that independent self-construal and interdependent self-construal separately. Reliability analysis, factor analysis, and logistic regression analysis (controlling gender and age) was used as the data analysis method. Results: According to the results of this study, the stronger independent self-construal, the more preference for the free independent travel type rather than package travel, and the stronger interdependent self-construal, the more preference for the package travel type rather than free independent travel. Conclusions: Self-construal is an antecedent variable influencing the choice of travel type. Travel agencies must consider the consumer's self-construal (independent self-construal vs. interdependent self-construal) before planning and designing overseas travel products.

• Journal of KIISE
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• v.44 no.4
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• pp.423-432
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• 2017

Recently, the video quality control schemes for the improvement of the QoE (Quality of Experience) of video streaming services that are based on DASH (Dynamic Adaptive Streaming over HTTP), which is a standard of HTTP adaptive streaming (HAS) services, have been studied. However, the problem of the existing schemes is the degradation that is due to unnecessary quality changes because the VBR (Variable Bitrate) characteristics of the video are not considered. In this paper, we propose a SC-DASH (Segment Characteristics-based DASH) which controls the video quality based on the segment characteristics. The SC-DASH can prevent the occurrence of the unnecessary quality changes by controlling the video quality based on the size of the next segment, the segment throughput, and the buffer occupancy. The experiment results showed that the SC-DASH improves the QoE by reducing the unnecessary quality changes compared with the existing quality control schemes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.11-15
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• 2011

In this paper, a methodology for the power control of a wind turbine, which is the variable-speed and variable-pitch (VSVP) control system, is introduced. This control methodology maximizes the capability of the turbine to extract maximum power from the wind in the regions with low wind speeds. Further, it regulates the wind-turbine power as the rated power in the case of the regions with high wind speeds. A simple drive train model is used to design the VSVP control system. The methodology for VSVP control is mechanized by controlling the generator torque and blade pitch. Finally, some simulation results for the VSVP control to a MW wind turbine are discussed in this paper.

• Journal of The Korean Digital Architecture Interior Association
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• v.13 no.4
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• pp.51-60
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• 2013

With regard to urban culture this study aims to essential understanding and systematic approach to the culture. The "2012 Seoul Survey" report has been used to find out causality among the related variables. In the first place 'satisfaction of cultural condition' was operationally selected as a dependent variable for regression. For the purpose of controlling the third factors for ceteris paribus effect correlation analysis was previously done between the dependent variable and all other variables respectively, which resulted in two groups of variables: group (1) - 2 variables of very significant correlations(p-value<0.01) and (2) - the other 6 variables of significant correlations(p-value<0.05). Then hierarchical regression was adopted to these 2 groups to analyse statistical significance of independent variables, and multicollinearity(VIF; variance inflation factor). Additionally to OLS robust and bootstrapping regressions were done to confirm the validity of this model specification. At last a regression model specified by group (1) as independent variables(they are 'community spirit caring for women, the disabled, the poor and the old,' 'satisfaction of bicycle riding condition' shows that the variables have statistically significant and substantially strong effect on 'satisfaction of cultural condition.' This finding implies the following understanding; (1) urban festivals are regarded as the main of the urban culture as of now and this results from the low level of today's culture, (2) culture is telling and hearing stories but the influential relationship between urban culture and community spirit on the weak is negative, which says that the cultural perception among citizen is somewhat selfish and far from the essential understanding of the urban culture. In spite of restrictive external validity this finding can be used as a direction for promoting culture and a basis for related policy choice in cities.

• Journal of the Korean Data and Information Science Society
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• v.25 no.4
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• pp.715-725
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• 2014

This study uses a quantile regression analysis to investigate intergenerational economic mobility in Korea. The analysis is based on data from the 1st through 11th waves of the Korean Labor and Income Panel Study (KLIPS) conducted from 1998-2008. The household nature of the data allows us to link parents' incomes to children's incomes at different points in time. Using a quantile regression analysis instead of mean one reveals that the effect of fathers' earnings are different across the conditional distribution of sons' earnings, particularly being larger on the upper quantile than on the lower quantile. After controlling effect of sons' college education by including a dummy variable for the degree, however, the pattern among quantile effects for fathers' earnings is no longer clear. Instead a new pattern emerges that education has a much larger effect on the upper quantiles than on the lower ones. Using nonparametric estimates of conditional density curves based on the quantile regression results, we derive some interesting features in graphical forms, which are not obvious in numerical analysis.