• Title/Summary/Keyword: Longitudinal Studies

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Stability in Friendship Patterns Among Kindergarteners: A Short-Term Longitudinal Study (유아의 친구관계 안정성에 대한 단기 종단적 탐색)

  • Park, Mi Hyun;Park, Kyung Ja
    • Korean Journal of Child Studies
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    • v.37 no.1
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    • pp.73-82
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    • 2016
  • Objective: This two-wave study examined stability in kindergarteners' friendship patterns over 5 months. Methods: Participants were 501 five-year-old children (262 girls and 239 boys) attending kindergartens in Seoul, Incheon, and Kyounggi provinces in Korea. Each child nominated three individuals as his/her friends in July, and again in December of 2013. Depending on the presence/absence of friendships and the mutuality of identifying friends, the children's friendship patterns were categorized into five groups: stable, fluid, loss, gain, and friendless. The data were analyzed by descriptive statistics, and chi-square tests. Results: Results revealed stability, as well as changes in friendship patterns, among kindergarteners over the 5-month period. The stable friendships, those that maintained the same friend(s) in both waves, was 43.7%, the fluid friendships, those that changed friends over the 5 month period was 18%, the gain friendships, those who had newly developed friends in wave 2 was 17%, and the loss friendships, those who had friends at wave 1 but lost friends at wave 2, was 9.8%. The friendless, those that had no friends in both waves, was 11.5%. Conclusion: Results showed that kindergarteners were capable of maintaining and making new friends over a 5-month period.

Semiparametric Kernel Poisson Regression for Longitudinal Count Data

  • Hwang, Chang-Ha;Shim, Joo-Yong
    • Communications for Statistical Applications and Methods
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    • v.15 no.6
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    • pp.1003-1011
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    • 2008
  • Mixed-effect Poisson regression models are widely used for analysis of correlated count data such as those found in longitudinal studies. In this paper, we consider kernel extensions with semiparametric fixed effects and parametric random effects. The estimation is through the penalized likelihood method based on kernel trick and our focus is on the efficient computation and the effective hyperparameter selection. For the selection of hyperparameters, cross-validation techniques are employed. Examples illustrating usage and features of the proposed method are provided.

A multivariate latent class profile analysis for longitudinal data with a latent group variable

  • Lee, Jung Wun;Chung, Hwan
    • Communications for Statistical Applications and Methods
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    • v.27 no.1
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    • pp.15-35
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    • 2020
  • In research on behavioral studies, significant attention has been paid to the stage-sequential process for multiple latent class variables. We now explore the stage-sequential process of multiple latent class variables using the multivariate latent class profile analysis (MLCPA). A latent profile variable, representing the stage-sequential process in MLCPA, is formed by a set of repeatedly measured categorical response variables. This paper proposes the extended MLCPA in order to explain an association between the latent profile variable and the latent group variable as a form of a two-dimensional contingency table. We applied the extended MLCPA to the National Longitudinal Survey on Youth 1997 (NLSY97) data to investigate the association between of developmental progression of depression and substance use behaviors among adolescents who experienced Authoritarian parental styles in their youth.

The Behavior of Prestressed Composite Box Girder (프리스트레스트 합성상자형교의 거동 특성)

  • 김주형;한택희;김종헌;강영종
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.591-596
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    • 2001
  • In case of continuous steel box-girder bridges, the magnitude of the longitudinal tensile stress on concrete in internal support is larger than the tensile strength of concrete. In this paper, the parametric study was performed to present the effective magnitude of the longitudinal prestress for reducing the longitudinal tensile stress to decrease under the tensile strength of concrete. The parametric study is conducted with changing the steel box-girder section and the span length of bridge. Three dimensional finite element analyses are conducted with ABAQUS program. The behavior of the steel box-girder bridge with prestress is investigated through experimental works on a analogous steel box-girder bridge model, and their results are compared with those of analytical studies.

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Stress Concentration of Longitudinal Rib to Deckplate Welded Joint in Orthotropic Steel Bridge Decks (강상판 종리브.바닥강판 응접연결부의 응력집중)

  • 장동일;최동호;최준혁;김도환
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1999.04a
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    • pp.343-350
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    • 1999
  • Orthotropic steel bridge decks are potentially liable to cause fatigue cracks due to weld defects, residual stresses, and in-plane or out-of-plane stresses. In particular, the cracks propagated through deckplate in longitudinal rib to deckplate joints occur at weld toe and weld root due to stress concentrations. Numerical parametric studies are performed to show the Influence of the parameters on the stress concentration at the connection between the longitudinal rib and the deckplate. The parameters include root gap, toe angle $\theta$, toe radius $\rho$, and weld penetration. This study provides a fundamental point for the improvement of fatigue resistance and the estimation of the fatigue crack propagation in wekded joint details.

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Numerical Simulation on Interactions of Longitudinal Vortices in a Turbulent Boundary Layer (종방향 와동과 난류경계층의 상호작용에 관한 수치해석)

  • Yang Jang-Sik
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.6
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    • pp.637-644
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    • 2005
  • This paper describes the numerical simulation of the interaction between longitudinal vortices ("common flow up") and a 3-D turbulent boundary layer over a flat plate To analyze the common flow up Produced from vortex generators. the flow field behind the vortex generators Is modeled by the information that is available from studies on a half-delta winglet. Also. the Reynolds-averaged Navier-Stokes equation for three-dimensional turbulent flows. together with a two-layer turbulence model to resolve the near-wall flow, is solved by the method of AF-ADI. The computational results predict that the boundary layer is thinned in the regions where the secondary flow is directed toward the wall and thickened where it is directed away from the wall Also. the numerical results. such as Reynolds stresses. turbulent kinetic energy and skin friction characteristics generated from the vortex generators . are reasonably close to the experimental data.

Analytical Study on the Improvement of Fatigue Strength for the Orthotropic Steel Decks with Reinforced Structural Details (보강상세 적용에 따른 강바닥판 피로강도 향상에 관한 해석적 연구)

  • Kyung, Kab-Soo;Park, Kyung-Jin;Kin, Kyo-Hoon;Park, Hye-Yeon
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.839-844
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    • 2007
  • In order to reduce resultant stress of the connection detail of longitudinal and rib and floor beam, in this study, the parameter studies for the reinforcement details as the bulk head and the vertical rib were preformed with FE analysis. As the result, it was shown that reinforcement detail with the bulk head plate in longitudinal rig reduced generally the principal stress at the connection detail, but the stress concentration of the weld toe parts occurring fatigue crack increased. However, it was known that the reinforcement detail with the vertical rib in the rib is more effective than the bulk head plate of the reduction stress concentration in the weld toe parts.

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On the attenuation of the axisymmetric longitudinal waves propagating in the bi-layered hollow cylinder made of viscoelastic materials

  • Kocal, Tarik;Akbarov, Surkay D.
    • Structural Engineering and Mechanics
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    • v.61 no.1
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    • pp.143-160
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    • 2017
  • The paper studies the attenuation of the axisymmetric longitudinal waves propagating in the bi-layered hollow cylinder made of linear viscoelastic materials. Investigations are made by utilizing the exact equations of motion of the theory of viscoelasticity. The dispersion equation is obtained for an arbitrary type of hereditary operator of the materials of the constituents and a solution algorithm is developed for obtaining numerical results on the attenuation of the waves under consideration. Specific numerical results are presented and discussed for the case where the viscoelasticity of the materials is described through fractional-exponential operators by Rabotnov. In particular, how the rheological parameters influence the attenuation of the axisymmetric longitudinal waves propagating in the cylinder under consideration, is established.

Semiparametric kernel logistic regression with longitudinal data

  • Shim, Joo-Yong;Seok, Kyung-Ha
    • Journal of the Korean Data and Information Science Society
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    • v.23 no.2
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    • pp.385-392
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    • 2012
  • Logistic regression is a well known binary classification method in the field of statistical learning. Mixed-effect regression models are widely used for the analysis of correlated data such as those found in longitudinal studies. We consider kernel extensions with semiparametric fixed effects and parametric random effects for the logistic regression. The estimation is performed through the penalized likelihood method based on kernel trick, and our focus is on the efficient computation and the effective hyperparameter selection. For the selection of optimal hyperparameters, cross-validation techniques are employed. Numerical results are then presented to indicate the performance of the proposed procedure.

Emotional Intelligence Research Trends and Future Research Directions in Korean Journals

  • LEE, Seoyeon;MOON, Jaeseung
    • The Journal of Industrial Distribution & Business
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    • v.12 no.1
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    • pp.31-46
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    • 2021
  • Purpose: The purpose of the study is to analyze the characteristics of emotional intelligence and the variables related to emotional intelligence in a comprehensive manner. In addition, the study intends to present research trends and future research directions of emotional intelligence in a Korean context by analyzing the effects of emotional intelligence and its mechanisms. Research Design, Data, and Methodology: 77 KCI listed studies were selected for the analysis, and the research perspective of emotional intelligence, measurement instruments, empirical research and research methods were analyzed. In addition, research directions were suggested based on the analysis results. Results: The results of the analysis were as follows: First, previous researchers used the ability model of emotional intelligence the most. Second, Previous studies tended to focus on behavioral factors as dependent variables affected by emotional intelligence, in addition to attitudes, affection. Third, there were few studies on the antecedents of emotional intelligence, however, most studies dealt with the consequences of emotional intelligence. Fourth, few studies dealt with moderators between emotional intelligence and dependent variables. Fifth, on the research type, most studies were quantitative studies, however, a few of them were qualitative studies (Literature review, in-depth interview). Sixth, with regard to the analysis level, almost all studies were conducted on the individual level of emotional intelligence, and most studies featured a cross-sectional research design (longitudinal research design was rare). Conclusion: First, from the perspective of emotional intelligence, additional research should be focused on not only the ability model of emotional intelligence but also on the trait model or the mixed model in the future. Second, since emotional intelligence is a multidimensional construct, it is necessary to study the profile of emotional intelligence by employing people-centered as well as variable-centered methods. Third, with regard to empirical studies, additional research is needed with respect to not only the emotional intelligence of the subordinate, but also the emotional intelligence of the supervisor (leader) and the emotional intelligence of the group. Fourth, it is necessary to actively utilize not only cross-sectional design but also longitudinal design, and qualitative research and meta-analysis methods should also be adopted.