• Journal of Preventive Medicine and Public Health
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• v.40 no.6
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• pp.495-504
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• 2007

Objectives : This study attempts to show how studies using non-experimental data can strengthen causal inferences by applying propensity score and instrumental variable methods based on the counterfactual framework. For illustrative purposes, we examine the effect of having private health insurance on the probability of experiencing at least one hospital admission in the previous year. Methods : Using data from the 4th wave of the Korea Labor and Income Panel Study, we compared the results obtained using propensity score and instrumental variable methods with those from conventional logistic and linear regression models, respectively. Results : While conventional multiple regression analyses fail to identify the effect, the results estimated using propensity score and instrumental variable methods suggest that having private health insurance has positive and statistically significant effects on hospital admission. Conclusions : This study demonstrates that propensity score and instrumental variable methods provide potentially useful alternatives to conventional regression approaches in making causal inferences using non-experimental data.

• Genomics & Informatics
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• v.21 no.3
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• pp.28.1-28.13
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• 2023

Mild cognitive impairment (MCI) is a clinical syndrome characterized by the onset and evolution of cognitive impairments, often considered a transitional stage to Alzheimer's disease (AD). The genetic traits of MCI patients who experience a rapid progression to AD can enhance early diagnosis capabilities and facilitate drug discovery for AD. While a genome-wide association study (GWAS) is a standard tool for identifying single nucleotide polymorphisms (SNPs) related to a disease, it fails to detect SNPs with small effect sizes due to stringent control for multiple testing. Additionally, the method does not consider the group structures of SNPs, such as genes or linkage disequilibrium blocks, which can provide valuable insights into the genetic architecture. To address the limitations, we propose a Bayesian bi-level variable selection method that detects SNPs associated with time of conversion from MCI to AD. Our approach integrates group inclusion indicators into an accelerated failure time model to identify important SNP groups. Additionally, we employ data augmentation techniques to impute censored time values using a predictive posterior. We adapt Dirichlet-Laplace shrinkage priors to incorporate the group structure for SNP-level variable selection. In the simulation study, our method outperformed other competing methods regarding variable selection. The analysis of Alzheimer's Disease Neuroimaging Initiative (ADNI) data revealed several genes directly or indirectly related to AD, whereas a classical GWAS did not identify any significant SNPs.

• Journal of Families and Better Life
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• v.10 no.1 s.19
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• pp.27-42
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• 1992

This study focused on consumer information search activity and consumer's post-purchase satisfaction. For these purpose, a survey was conducted suing questionaires on 430 homemakers that lived in seoul. Statistics used for data were Frequency Distribution. Percentile, Mean, One-way AAANOVA., Scheffe-test, T-test, Pearson's correlation. Multiple Regression Analysis and Multiple Classification Analysis. The major findings were ; 1) The level of each amount information search was lower than average. And the level of consumer's post-purchase satisfaction was a little higher than average. 2) On amount of "noncommercial-personal" information search, the influencing variables were desire to seek information, education, brand royalty in turn. These three variables explained 7% of dependent variable's variance. 3) On amount of "noncommercial-media" information search, the influencing variables were desire to seek information, amount of internal information, education, occupational status in turn. These variables explained 14% of dependent variable's variance. 4) On amount of "commercial-personal" information search, the influencing variable was desire to seek information, and this variable explained 3.1% of dependent variable'a variance. 5) On amount of "commercial-media" information search, the influencing variables were desire to seek information, education, amount of internal information in turn. These three variables explained 12.1% dependent variable's variance. 6) Resulting from multiple classification analysis, influencing variables on consumer's post-purchase satisfaction were amount of noncommercial-media information search and printed media search, and brand royalty. These three variables explained 9% of dependent variable's variance. Furthermore, througout all the subareas of consumer's satisfaction, the amount of noncommercial-media information search was the most influencing variable.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.118-128
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• 2016

The purpose of this study is to verify the role of moderating effect of pay system on the relation between organizational justice and employee's pay level satisfaction. By default, it would be a justice find out a positive impact on pay levels satisfaction members feel. It will examine the mediating effect of the wage system the main purpose of this study is to prove their relationship. A survey was conducted to examine the role of moderating effect of pay system on the responses of 218 employees. sex, education, status, and service type were chosen as control variable, and the regression model which treated the distributive justice and procedural justice as independent variable was set. A pay system was supposed as moderating variable of the relation between organizational justice and pay level satisfaction, In addition the pay system have a dummy variable (if pay system is lower than the average, pay system is 0, else pay system is 1). The result showed that the relation of organizational justice and pay level satisfaction are significantly unique. This means that pay system moderates the relation of organizational justice and pay level satisfaction. These results are different from the prior researches which had treated pay system as mediative variable of organizational justice and pay level satisfaction. This difference may be from the property of attitude variable. For example, pay satisfaction is individual-based attitude. Moreover, organizational committment has the instrumentality for future reward, while pay satisfaction does not. The future study should consider the properties of these variables and other employee's attitude variables.

• Fire Science and Engineering
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• v.24 no.3
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• pp.119-130
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• 2010

In the fire and disaster prevention administration of which is not developed in comparison with any other administrative system, the systematic improvement is necessary. For system's more development, financial resource of fire service must be increased sufficiently. If fire service's budget is not allocated sufficiently, fire and disaster were not prevented effectively. This study set up hypothesis based on theoretical background and past research. In this study, dependent variables are fire service budget and police service budget per person Whereas independent variables include demand characteristics, economical characteristics, political characteristics, and previous fiscal year's budget. Statistical methods for the hypothesis's verification are regression analysis, correlation analysis and t-test. The major finding on this study are as follows: First, regression analysis showed that significant variable were past budget variable and economical variable. But political variable and demand variable were not significant except for a emergency medical variable. Second, fire service budget's average was not different significantly from police service budget's average. The above result are contingent upon the theory described in this research. A sustained research and development effort will be necessary if substantial and meaningful progress is to be made in fire service budget.

• Journal of Korean Elementary Science Education
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• v.28 no.2
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• pp.154-160
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• 2009

Correlational reasoning is used to analyze results from an experiment and create meaningful relationships among variables. Although there were many recognition development studies, not a single study found the optimal period for the development of logical thinking. Therefore, the purpose of this study is to find the optimal period for students whose logic for variable controlling and correlational reasoning are poor. This study made a logic program treatment subject for students between the 4th and 8th grade whose recognition in reasoning has not been developed in general in order to find the optimal period for their development. The variable-controlling reasoning was performed the program of voice survey and sugared-water melting in subsection survey and sugared-water melting in subsection. And, the correlation reasoning was performed the program of rat's size and tail color, treatment, and effect. As a result of research, students, who were not formed variable controlling and correlational reasoning, could be known to be enhanced through learning, but to fail to be formed the qualitative change like the cognitive development. In other words, the optimal period couldn't be found that is grown the formation of students, who are not formed the variable controlling and correlational reasoning, through learning. It is expected that this research can contribute to the improvement of students' cognitive level and there would be more active researches in different fields to improve the cognitive level.

• The Mathematical Education
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• v.50 no.2
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• pp.213-231
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• 2011

The purpose of this study is to analyze the 6th graders' understanding of the concepts of variable on various aspects of school algebra. For this purpose, the test of concepts of variable targeting a sixth-grade class was conducted and then two students were selected for in-depth interview. The level of mathematics achievement of the two students was not significantly different but there were differences between them in terms of understanding about the concepts of variable. The results obtained in this study are as follows: First, the students had little basic understanding of the variables and they had many cognitive difficulties with respect to the variables. Second, the students were familiar with only the symbol '${\Box}$' not the other letters nor symbols. Third, students comprehended the variable as generalizers imperfectly. Fourth, the students' skill of operations between letters was below expectations and there was the student who omitted the mathematical sign in letter expressions including the mathematical sign such as x+3. Fifth, the students lacked the ability to reason the patterns inductively and symbolize them using variables. Sixth, in connection with the variables in functional relationships, the students were more familiar with the potential and discrete variation than practical and continuous variation. On the basis of the results, this study gives several implications related to the early algebra education, especially the teaching methods of variables.

• Journal of The Korean Association For Science Education
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• v.31 no.4
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• pp.587-599
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• 2011

The purpose of this study was to analyze variable-controlling strategy (below vcs) and the ability to infer the effect of variables in Middle school students who experienced 'Thinking Science' activities in a CASE program. For this study, 71 9th grade students experienced in CASE program for 2 years were selected as the experimental group and 72 students were selected as the control group. All students were tested with Science Reasoning TaskVII. The five types of variable-controlling strategy were extracted from students' response. According to the result of this study, the students experienced in CASE program was more successful in the variable-controlling strategy of length, quality, and shape than the control group. The types of reasoning ability of the variable effect intuitively were categorized as possibility of reasoning, impossibility of reasoning, and impossibility of reversible thinking. It has shown that the reasoning ability of the experimental group was higher than that of the control group in the length and thickness variable effect. The results of this study implied that the variable controlling activities in CASE program could be effective for learning variable controlling, and eventually, for the development of reasoning ability of the variable controlling effect. In the ability to infer the effects of variables to get difficult Intuitively, both groups were similar to the rate of cognitive level reached to the formal operation in generalization, and the student of experimental group was 1.5 times faster than the control group.

• The Research Journal of the Costume Culture
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• v.24 no.6
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• pp.756-776
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• 2016

The concern over beauty is increasing as the importance of appearance is becoming more prominent. Accordingly, the importance of studying beauty is now apparent. The purpose of this study is to analyze existing beauty-related research in order to assess current trends in beauty-related studies. Materials were collected from the master's theses and academic journals from 1997 through 2016. In addition, 81 beauty-related papers were selected and classified into 3 categories according to their subjects and content. There were 19 hair attitude papers, 52 papers about make-up and skincare, and 10 papers on cosmetic surgery. Each type was divided into detailed themes according to the study theme and its number was grasped. Consequently it was classified into 9 themes about the attitude toward hair and the relevant variable study, 10 themes about the attitude toward hair style and relevant variable study, 24 themes about the make-up attitude and relevant variable study, 28 themes about the skin care attitude and relevant variable study, and 10 themes about the cosmetic surgery attitude and relevant variable study. The results revealed that academic concern about beauty sharply increased starting in 2005. Moreover, we determined that the methodologies used in hair and make-up studies were sound and detailed, while cosmetic surgery studies were more inconsistent and poorly analyzed. Thus cosmetic surgery should be further researched in a more standardized and thorough manner. This review of attitudes toward beauty will serve as a basis for follow-up studies that employ meta-analyses to draw more quantitative conclusions by aggregating many more study results.

• Smart Structures and Systems
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• v.4 no.4
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• pp.493-515
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• 2008

Semi-active control systems have attracted a great deal of attention in recent years because these systems can operate on battery power alone, proving advantageous during seismic events when the main power source of the structure may likely fail. The behavior of semi-active devices is often highly non-linear and requires suitable and efficient control algorithm. This paper presents the comparative study and performance of variable semi-active friction dampers by using recently proposed predictive control law with direct output feedback. In this control law, the variable slip force of semi-active variable friction damper is kept slightly lower than the critical friction force, which allows the damper to remain in the slip state during an earthquake, resulting in improved energy dissipation capability. This control algorithm is able to produce a continuous and smooth slip forces for a variable friction damper. The numerical examples include a structure controlled with multiple variable semi-active friction dampers and with multiple passive friction dampers. A parameter, gain multiplier defined as the ratio of damper force to critical damper control force, is investigated under four different real earthquake ground motions, which plays an important role in the present control algorithm of the damper. The numerically evaluated optimum parametric value is considered for the analysis of the structure with dampers. The numerical results of the variable friction dampers show better performance over the passive dampers in reducing the seismic response of structures.