• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.259-269
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• 2015

The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.

• Korean Journal of Child Studies
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• v.37 no.6
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• pp.5-17
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• 2016

Objective: This study focused on the longitudinal associations between self-esteem and peer relationships in Korean adolescents while considering gender and timing-early and late adolescence-differences. Methods: The study made use of data from the Korean Children and Youth Panel Survey. Three waves of data collected from 2,351 adolescents were analyzed by means of autoregressive cross-lagged modeling. Results: The results indicated that self-esteem predicted subsequent changes in peer relationship but not vice versa. Further, the results that longitudinal associations between self-esteem and peer relationships differed between male and female adolescents and between early and late adolescence. Conclusion: The findings revaluated the longitudinal relationship between self-esteem and peer relationships. Both gender and timing should be considered when planning interventions related issues about self-esteem and peer relationships in adolescence.

• Journal of Korean Medicine Rehabilitation
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• v.26 no.3
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• pp.59-65
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• 2016

Objectives The purpose of this review is to analyze domestic research trend of the ossification of posterior longitudinal ligament in Korean medicine. Methods We searched articles in Korean databases such as OASIS, RISS, NDSL and sorted the articles by journals, published year, institutions and research type. Results 9 suitable theses were reviewed. They were published between 2002 till 2011. Most of the theses were published in The Acupuncture, the journal of Korean Acupuncture & Moxibustion Medicine Society. There were 6 case reports, 2 case series and single disease review. Conclusions There were only 9 studies about the ossification of posterior longitudinal ligament in Korean medicine and most of them were case reports. To reinforce the evidence of effectiveness of Korean medicine, additional studies are required and well designed studies such as randomized controlled trials need to be carried out.

• International Journal of Computer Science & Network Security
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• v.21 no.4
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• pp.52-58
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• 2021

Questionnaires and surveys are increasingly being used to collect information from participants of empirical software engineering studies. Usually, such data is analyzed using statistical methods to show an overall picture of participants' agreement or disagreement. In general, the whole survey population is considered as one group with some methods to extract varieties. Sometimes, there are different opinions in the same group, but they are not well discovered. In some cases of the analysis, the population may be divided into subgroups according to some data. The opinions of different segments of the population may be the same. Even though the existing approach can capture the general trends, there is a risk that the opinions of different sub-groups are lost. The problem becomes more complex in longitudinal studies where minority opinions might fade over time. Longitudinal survey data may include several interesting patterns that can be extracted using a clustering process. It can discover new information and give attention to different opinions. We suggest using a data mining approach to finding the diversity among the different groups in longitudinal studies. Our study shows that diversity can be revealed and tracked over time using the clustering approach, and the minorities have an opportunity to be heard.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3479-3492
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• 2022

Longitudinal quantification of brain changes due to development, aging or disease plays an important role in the filed of personalized-medicine applications. However, due to the temporal variability in shape and different imaging equipment and parameters, estimating anatomical changes in longitudinal studies is significantly challenging. In this paper, a longitudinal Magnetic Resonance(MR) brain image segmentation algorithm proposed by combining intensity information and anisotropic smoothness term which contain a spatial smoothness constraint and longitudinal consistent constraint into a variational framework. The minimization of the proposed energy functional is strictly and effectively derived from a fast optimization algorithm. A large number of experimental results show that the proposed method can guarantee segmentation accuracy and longitudinal consistency in both simulated and real longitudinal MR brain images for analysis of anatomical changes over time.

• Communications for Statistical Applications and Methods
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• v.9 no.3
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• pp.703-713
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• 2002

In longitudinal studies, outcomes are repeatedly measured over time for each subject. It is common to have missing values or dropouts for longitudinal data. In this study time trend in longitudinal data with dropouts is of concern. The confounding of time trend with dropout process is investigated through simulation studies. Some simulation results are reported for binary responses as well as continuous responses with patterns of dropouts varying. It has been found that time trend is not confounded with random dropout process for binary responses when it is estimated using GEE.

• Korean Journal of Child Studies
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• v.25 no.6
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• pp.35-52
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• 2004

The purpose of this study is to explore the relation among mother's rearing attitude in infancy, children's self-concept and the relationship with friends in childhood by using the longitudinal data originated by the Korean Institute for Research in the Behavioral Sciences(KIRBS). Specifically, using Structural Equation Modeling(SEM), the causal relation among the mother's rearing attitude in infancy, children's self-concept and the relationship with friends in childhood were examined across a 8-year-period. The subjects were 68 children(38 boys and 30 girls) from the KIRBS longitudinal data. The results showed that mother's rearing attitude in infancy can be consequential environmental variable factor, and children's self-concept do not play an essential intermediate role between mother's rearing attitude in infancy and the relationship with friends in childhood. This study used a newly attempted method in the field of Human Development.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.571-576
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• 2001

The objective of this study is to assess seismic damage potential and evaluate structural performance of columns in concrete moment frames. For this purpose the results of 3 former studies are compared. Experimental variables considered in these studies are lap-splice of longitudinal reinforcement, axial load level, longitudinal reinforcement ratio, etc. The columns in 1st story of the building are considered in these studies since the columns in 1st story shall resist largest axial force during an earthquake. Based on test results strength, ductility capacities as well as plastic hinge length are compared and discussed.

• Korean Journal of Child Studies
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• v.31 no.1
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• pp.1-17
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• 2010

This study explored the differences in gender, developmental period and parents in terms of parenting, the cross-sectional and longitudinal relationships in parenting by gender, and the cross-sectional and longitudinal relationships between participant roles in bullying situations and parenting by gender. The subjects were 498 4-5th grade children and the instruments utilized in this study were the Parental Bonding Instrument (Bowers, Smith, & Binney, 1994) and the Participant Roles Scale (Sutton & Smith, 1999). The subjects were contacted again one year after the first contact. Results showed that the relationships between parents were longitudinally quite stable. Girls whose fathers had higher levels of accurate monitoring were more likely to be defenders cross-sectionally. Girls whose parents had more accurate monitoring were less likely to be victims longitudinally. The results underscore the importance of examining both gender and participant roles in bullying situations.

• Genomics & Informatics
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• v.20 no.1
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• pp.8.1-8.14
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• 2022

Despite the success of recent genome-wide association studies investigating longitudinal traits, a large fraction of overall heritability remains unexplained. This suggests that some of the missing heritability may be accounted for by gene-gene and gene-time/environment interactions. In this paper, we develop a Bayesian variable selection method for longitudinal genetic data based on mixed models. The method jointly models the main effects and interactions of all candidate genetic variants and non-genetic factors and has higher statistical power than previous approaches. To account for the within-subject dependence structure, we propose a grid-based approach that models only one fixed-dimensional covariance matrix, which is thus applicable to data where subjects have different numbers of time points. We provide the theoretical basis of our Bayesian method and then illustrate its performance using data from the 1000 Genome Project with various simulation settings. Several simulation studies show that our multivariate method increases the statistical power compared to the corresponding univariate method and can detect gene-time/ environment interactions well. We further evaluate our method with different numbers of individuals, variants, and causal variants, as well as different trait-heritability, and conclude that our method performs reasonably well with various simulation settings.