• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.145-151
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• 2003

Using computational fluid dynamics (CFD) method, we investigated three-dimensional fluid flow field and particle movement with respect to the injected gas flow rate variation in typical cyclone separator system. The results of numerical investigation were deduced by coupling the analysis of fluid flow field with Wavier-stokes equation and the tracking of the particle trajectory with Langrangian approach. It was shown that the increasing of injected gas flow rate resulted in the increasing of pressure loss in the separator. This change of inner pressure had an effect on an aspect of the fluid flow in the separator. Particle movement was determined by fluid flow in the separator and was fully depended on a diameter of particles under the fixed flow rate. Increasing of injected gas flow rate was led to an increasing of the trace of particle, so the particles moved to the lower part of the separator. For this reason, the minimum diameters of the particles were decreased and increased the separation rate under the fixed particle diameter. In conclusion, the changes of injected gas flow rate have an important factor to the fluctuation of the fluid flow field and particle trajectory in the separator.

• Women's Health Nursing
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• v.28 no.2
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• pp.123-133
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• 2022

Purpose: This study investigated the trajectory of subjective health status in married postmenopausal women and aimed to identify predictive factors affecting subjective health status. Methods: Data were obtained from women who participated in wave 4 (2012) of the Korean Longitudinal Survey of Women & Families Longitudinal Study and continued to the latest phase (wave 7, 2018). A latent growth model (LGM) was used to analyze data from 1,719 married postmenopausal women in the framework of the ecological system theory. Results: The mean age of the participants at wave 4 was 56.39±4.71 years, and the average subjective health status was around the midpoint (3.19±0.84). LGM analysis confirmed that subjective health status decreased over time (initial B=3.21, slope B=-0.03). The factors affecting initial subjective health were age, body mass index, frequency of vigorous physical activity (microsystem level), marital satisfaction (mesosystem level), and medical service utilization (macrosystem level). Medical service utilization and the frequency of vigorous physical activity were identified as predictive factors affecting the slope in subjective health status. The model fit was satisfactory (TLI=.92, CFI=.95, and RMSEA=.04). Conclusion: This analysis of the trajectory of subjective health status of married postmenopausal women over time confirmed that subjective health is influenced by overall ecological system factors, including the microsystem, mesosystem, exosystem, macrosystem, and chronosystem. Therefore, it is necessary to assess physical activity and support policies promoting access to medical services in order to improve the subjective health status of married postmenopausal women.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.287-288
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• 2015

본 연구에서는 급증하는 청소년기 휴대폰 의존 문제의 심각성에 주목하여 우리나라 청소년들의 휴대폰 의존이 시간의 흐름에 따라 어떠한 변화 양상을 보이는지 실증적인 검증을 실시하고자 하였다. 이를 위하여 한국아동 청소년패널조사(KCYPS) 중학교 1학년 1~4차년도 자료에 대하여 이차잠재성장모형(second-order latent growth modeling)을 이용하여 휴대폰 의존의 발달궤적을 확인하였다. 휴대폰 의존의 발달궤적에 대한 최적의 모형을 찾기 위해 다수의 모형을 구성하여 비교 검증하였으며, 그 결과, 이차함수모형에 대하여 오차 간 공분산을 설정하고, 시간의 흐름에 따른 측정동일성 제약을 가한 후, 오차 간 공분산에 대한 동일화 제약을 가한 모형이 가장 좋은 적합도를 보이는 것으로 확인되었다. 이렇게 도출된 모형에 의하면, 중학교 1학년부터 고등학교 1학년까지 휴대폰 의존 정도는 증가하다가 그 증가율이 둔화되는 이차함수모형의 변화를 보이는 것으로 나타났다. 이러한 결과에 근거하여 청소년기 휴대폰 의존에 대한 예방 및 개입과 관련된 함의를 제시하였다.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.100-106
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• 2010

In this paper crack propagation analyses in the dissimilar metal weldment of a nozzle were performed using a finite element alternating method (FEAM). A two-dimensional axisymmetric finite element nozzle model was prepared and welding simulation including the thermal heat transfer analysis and the thermal stress analysis was performed. Initial cracks were inserted at weld and heat affected zone in the finite element model which has welding residual stress distribution obtained from the welding simulation. To calculate crack propagation trajectories of these cracks, a new fatigue crack evaluation module was developed in addition to the previous FEAM program. With the new FEAM fatigue crack evaluation module, crack propagation trajectory and crack growth time were calculated automatically and effectively.

• Korean Journal of Child Studies
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• v.27 no.3
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• pp.169-187
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• 2006

A hierarchical linear model(HLM) provides advantages over existing traditional statistical methods (e.g., ordinary least squares regression, repeated measures analysis of variance, etc.) for analyzing multilevel/longitudinal data or diary methods. HLM can gauge a more precise estimation of lower-level effects within higher-level units, as well as describe each individual's growth trajectory across time with improved estimation. This article 1) provides scholars who study children and families with an overview of HLM (i.e., statistical assumptions, advantages/disadvantages, etc.), 2) provides an empirical study to illustrate the application of HLM, and 3) discusses the application of HLM to the study of children and families. In addition, this article provided useful information on available articles and websites to enhance the reader's understanding of HLM.

• East Asian Economic Review
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• v.24 no.4
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• pp.469-495
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• 2020

This paper overviews different exit strategies for the U.S. from the debt-overhang, and analyses their implications for emerging markets and global stability. These strategies are discussed in the context of the debates about secular-stagnation versus debt-overhang, the fiscal theory of the price level, the size of fiscal multipliers, prospects for a multipolar currency system, and historical case studies. We conclude that the reallocation of U.S. fiscal efforts towards infrastructure investment aiming at boosting growth, followed by a gradual tax increase, aiming at reaching a modest primary fiscal surplus over time are akin to an upfront investment in greater long-term global stability. Such a trajectory may solidify the viability and credibility of the U.S. dollar as a global anchor, thereby stabilizing Emerging Markets economies and global growth.

• Korean Journal of Social Welfare Studies
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• v.44 no.3
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• pp.85-112
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• 2013

This study aims to understand the developmental trajectories of life satisfaction among retirees and to examine what factors differentiate different trajectory classes. This study used three waves of longitudinal data from Korean Retirement and Income Study and data collected every two years(2005, 2007, and 2009). Subjects were respondents aged 50-69 who identified to be retired between wave 1 and wave 2. Finally, this study used 243 respondents for final data analysis. Life satisfaction was measured by seven items. The latent class growth model and multiple logistic regression model were used for data analysis. This study identified three distinct trajectory classes: high stable class(47.7%), high at the early stage but decreased class(42.8%), and low at the early stage and then decreased class(9.5%). This study founded that approximately 50% of the retirees experienced the decline of life satisfaction after retirement and about 10% of the sample was the most vulnerable group. This study analyzed what factors make different among the distinct trajectory groups. As a results, retirees who experienced the improvement in health change were more likely to be in 'high stable class' compared to 'hight at the early stage but decreased class'. In addition, retirees who were less educated, maintained the same health status rather than the improvement, worked as a temporary or a day laborer, and had less household income were more likely to belong to 'low at the early stage and then decreased class' relative to 'high stable class'. This study suggests that there are distinct three trajectories on life satisfaction among the retirees and finds out factors differentiating between trajectory groups. Based on these findings, the study discusses the implications for social work practice and further study.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.31 no.3
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• pp.154-160
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• 2020

Objectives: It remains unclear whether methylphenidate (MPH) has yadverse effects on growth in children. This study aimed to investigate the association of MPH with serum biological markers of growth in children with attention-deficit/hyperactivity disorder (ADHD). Methods: The present study included 103 children with ADHD (64 drug-naive children, 39 MPH-treated children) and 112 control subjects. Children with ADHD were diagnosed on the basis of a semi-structured interview. Levels of biochemical markers of growth, including insulin-like growth factor-I, thyroid stimulating hormone (TSH), free T₄, calcium, phosphorus, alkaline phosphatase, vitamin D, hemoglobin, total protein, albumin, total cholesterol, and hematocrit were measured in these individuals. Results: Except in case of TSH, no intergroup differences were found in the levels of the growth markers. The levels of TSH were found to be lower in the MPH-treated boys with ADHD than in the drug-naive and control groups (p<0.05), although the levels of TSH in all the groups were within normal limits. Conclusion: In this cross-sectional study, no significant association was found between MPH and growth markers. This calls for the need to carry out prospective longitudinal research studies in the future that investigate the effect of MPH on the growth trajectory in children.

• Journal of the Korea Convergence Society
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• v.10 no.7
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• pp.243-249
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• 2019

This study is aimed at offering a typology of changes in the social participation of middle-aged and older population and explore determinants for each type of such changes. The data employed for analysis are the 1st survey (2006) through the 6th version (2016) of the Korea Aging Research Panel Survey. Among the respondents of the panel survey, 1,327 males and 1,520 females with a total of 2,847 respondents were analyzed. As a result of applying the growth mixture modelling through the SPS 22.0 and M-plus 8.0 statistical programs, the changes in the social participation of middle-aged and older population have been classified into the 'high-decreasing', 'moderate-increasing' and 'low-stable' trajectory classes. Analysis of the determinants for each class shows that higher the education level, the more likely they are to belong to the high-decreasing and moderate-increasing classes than the low-stable class, and the more the population lives in urban areas, the more likely they are to belong to high-decreasing trajectory class than to low-stable class. Also, it was found that the probability of belonging to moderate-increasing trajectory class was higher than that of the low-stable class when there was no occupation. Through the results of these analyses, the implications of promoting social participation of middle-aged and older population were discussed.

• The Journal of the Korea Contents Association
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• v.21 no.4
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• pp.278-291
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• 2021

This study performed a longitudinal research on the causal relationship between multidimensionality of problem drinking and poverty, and multidimensional deprivation meaning the inequality, focusing on gender difference. For this, this study examined the latent group of problem drinking change trajectory through the latent class growth analysis targeting total 3,770 men and 5,632 women by using the 6th-year Korea Welfare Panel Study data from 2013 to 2018, and then conducted the multinominal logistic regression analysis to verify the influence of multidimensional deprivation factors on this latent group. The main results of this study are as follows. First, the latent group of problem drinking change trajectory according to gender was classified into three latent groups in both men and women while the development aspect was different from each other. The male latent group with 'moderate level' or higher showed higher level of problem drinking than women. However, in case of 'drinking group with high level' according to gender, as time passed, the men tended to maintain it while the women tended to increase it. Second, in the results of examining the effects of multidimensional deprivation on the latent group of problem drinking change trajectory, the men with more experiences of social deprivation and the women with more experiences of social security deprivation showed the higher possibility to belong to the 'drinking group with high level' compared to the 'drinking group with low level'. Based on such results above, this study discussed the preventive/intervention measures for problem drinking according to gender.