• Steel and Composite Structures
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• v.45 no.2
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• pp.175-191
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• 2022

A review of previous studies shows that although there is a considerable difference between buckling loads of structures under follower and non-follower lateral loads, only the buckling load of FGM elliptical cylindrical shell under non-follower lateral load was investigated in the literature. This study is the first to obtain the buckling load of elliptical FGM cylindrical shells under follower lateral load and also make a comparison between buckling loads of elliptical FGM cylindrical shells under follower and non-follower lateral loads. Moreover, this research is the first one to derive the load potential function of elliptical cylindrical shell. In this regard, the FGM cylindrical elliptical shell was modeled using the semi-analytical finite strip method and based on the First Shear Deformation Theory (FSDT). The shell is discretized by strip elements aligned in the longitudinal direction. The Lagrangian and harmonic shape functions were considered in the circumference and longitudinal directions, respectively. The buckling pressure of the shell under follower and non-follower lateral loads was obtained from eigenvalue problem. The results obtained from the model were compared with those presented in the literature to evaluate the validity of the model. A comparison index was defined to compare the buckling loads of the shell under follower and non-follower lateral load. A parametric study was carried out to investigate the effects of material properties and shell geometry characteristics on the comparison index. For the elliptical cylindrical shells with length-to-radius ratio greater than 16 and major-to-minor axis ratio greater than 0.6, the comparison index reaches to more than 20 percent which is significant. Moreover, the maximum difference is about 30 percent in some cases. The results obtained from the parametric study indicate that the buckling load of long elliptical cylindrical shell under non-follower load is not reliable.

• Korean Journal of Child Studies
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• v.37 no.4
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• pp.17-29
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• 2016

Objective: The purpose of this study was to examine the bidirectional relation between mobile phone dependency (MPD) and self-regulated learning (SRL) of early Korean adolescents in $4^{th}$, $6^{th}$ and $8^{th}$ grade, while taking into account gender differences. Methods: The study made use of panel data from the Korean Children and Youth Panel Study (KCYPS), and three waves of data collected from 2,264 adolescents were analyzed by means of autoregressive cross-lagged modeling. Results: The results can be summarized as follows. Firstly, MPD and SRL were consistently stable for adolescents in $4^{th}$, $6^{th}$ to $8^{th}$ grades. Secondly, a bidirectional relations between MPD and SRL were confirmed. In other words, there was a significant influence of a high level of MPD on a subsequent low level of SRL, and the high level of SRL also had a significant effect on the lower level of MPD across time. According to multi-group analysis, no gender differences were found in the relations between two constructs during the studied period. Conclusion: Findings highlighted not only the necessary media usage education but also parenting intervention strategies may help early adolescents to be prevented from negative effects of media usage and to enhance self-regulated learning ability. Based on the results, more implications were also discussed.

• Journal of the Korea Convergence Society
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• v.13 no.4
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• pp.521-530
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• 2022

This study investigates the last twenty two years of research trends in the burnout of psychiatric ward nurses and suggests guidance for future studies. Five domestic databases were used in the literature search, and fourteen articles that met the inclusion criteria were reviewed. thirteen articles were descriptive, cross-sectional studies and one study was qulitative study. Among the quantitative study, the most used instrument to measure burnout of nurses working in psychiatric wards was the Maslach Burnout Inventory (MBI). The individual factors related to burnout in nurses in psychiatric wards were age, marital status, years of clinical experience psychiatric mental health nurse license status. monthly income, religious status and education related to psychiatry. The most related situational factor that affect burnout in psychiatric ward nurses was experience of violence. In future research, large-scale cross-sectional and longitudinal studies should be conducted, and based on this, intervention studies should be conducted on reducing the burnout of psychiatric ward nurses.

• Korean Journal of Social Welfare Studies
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• v.42 no.4
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• pp.295-327
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• 2011

Although there are many studies on the retirement recently, very few studies have empirically addressed on mandatory retirement. In Korea, several scholars suggest that the seniority systems may be the main reason that employers have been reluctant to hire older workers. Therefore, the seniority system that Lazear(1979) proposed has significant implication on explaining mandatory retirement in Korea. Thus, this study aims to examine the seniority system that Lazear proposed can explain the retired employees' mandatory retirement. The empirical study is based on Korean Longitudinal Study of Ageing. wave I-II. The main result from this analysis is that interaction between wage and job tenure on mandatory retirement is statistically significant. For employees with high wage growth rates, the probability of mandatory retirement rate is higher as their job tenure is longer. On the other hand those employees with wage growth rates, that is lower although their job tenure is longer. This study supports the assertion of Lazear(1979).

• Journal of Families and Better Life
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• v.27 no.3
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• pp.31-43
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• 2009

Using the first wave of KLoSA(Korean Longitudinal Study of Ageing) beta version, this study analyzed factors affecting early retired men's subjective life satisfaction through Binary Logit and Multiple Regression. Total 552 men were selected as a sample. The main results of empirical analysis in this study were as follows: The retirement reason(health-) and monthly household income(+) affected whether they were satisfied with the retirement life or not and subjective life satisfaction over all. Especially, the retirement reason(health-) had a stronger effect on whether early retired min were satisfied with the retirement life or not and their subjective life satisfaction than monthly household income revealed significant variable in previous studies. This result represents that the retiree's life satisfaction analysis model must include retiree's characteristics at the time of retirement as well as retiree's current status characteristics or socio-economic characteristics.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.1 s.151
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• pp.32-39
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• 2007

A three-dimensional finite element model has been developed to simulate the MIG P/S welding process of two aluminum plates. The finite element calculations are performed using ANSYS finite element code, which takes into account the thermal and mechanical non-linear material properties. The results of finite element analysis compared with those of experiment to show its validity in view of distortions. Parametric studies are carried out on the validated model to assess the effects of various factors on the final residual distortion. Large deformations, temperature dependent material properties are included in the model. Finally, the formulas of fitting curves of angular distortion transverse shrinkage, and longitudinal shrinkage have been proposed.

• Journal of The Korean Astronomical Society
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• v.36 no.spc1
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• pp.21-27
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• 2003

In the present study, we have investigated morphology and evolution of small-scale Ha dynamic features on the quiet sun by analyzing video magnetograms and high resolution Ha images simultaneously taken for 5 hours at Big Bear Solar Observatory on April 18, 1997. From comparisons between time sequential longitudinal magnetograms and H$\alpha$ images covering $150" {\times} 150"$, several small-scale H$\alpha$ dynamic features have been observed at a site of magnetic flux cancellation. A close relationship between such features and cancelling magnetic fluxes has been revealed temporarily and spatially. Our results support that material injection by chromospheric magnetic reconnect ion may be essential in supporting numerous small-scale H$\alpha$ dynamical absorption features, being in line with recent observational studies showing that material injection by chromospheric magnetic reconnect ion is essential for the formation of solar filaments.

• Journal of Korean Academy of Nursing
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• v.32 no.3
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• pp.336-343
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• 2002

Recently the rate of adolescent smoking in Korea has increased rapidly, and various health problems related to smoking can be expected to increase in the future. Studies on smoking behavior report that assertiveness is important factor influencing on the adolescent smoking. Purpose: This study was conducted to develope a educational video for the purpose of adolescent's smoking prevention. Method: The 533 participating subjects, 269 in experimental group and 264 control group, in the study were 7th grade students. The content of video introduces three smoke tempting situations. The experimental group received 17 minute video education, and the control group did not receive any treatments. Result: The results show that the student's assertiveness was increased significantly in the experimental group after the video education. Student's attitude on smoking became more negative in the experimental group. However, in the control group, the intention, assertiveness, attitude was not changed. Conclusion: This assertiveness video can be useful educational resource for the smoking prevention program for adolescents. Also further study on longitudinal effect and application on drinking, drug abuse are needed.

• The Journal of the Korean dental association
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• v.54 no.11
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• pp.850-864
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• 2016

The Generalized Estimating Equations (GEE) approach is a widely used statistical method for analyzing longitudinal data and clustered data in clinical studies. In dentistry, due to multiple outcomes obtained from one patient, the outcomes produced from an individual patient are correlated with one another. This study focused on the basic ideas of GEE and introduced the types of covariance matrix and working correlation matrix. The quasi-likelihood information criterion (QIC) and quasi-likelihood information criterion approximation ($QIC_u$) were used to select the best working correlation matrix and the best fitting model for the correlated outcomes. The purpose of this study is to show a detailed process for the GEE analysis using SPSS software along with an orthodontic miniscrew example, and to help understand how to use GEE analysis in dental research.

• Journal of the Korean Society of Visualization
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• v.1 no.1
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• pp.82-91
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• 2003

The study of swirl flow has been of technical and scientific interest because it has an internal recirculation field and its tangential velocity is related to the curvature of the streamline. The fluid flow for ducts or elbows of an internal engine has been much studied through numerical methods and experiments, but studies about swirl flow has been insufficient. Using the PIV (Particle Image Velocimetry) method, this study found the time-mean velocity distribution, time-mean turbulent intensity, with swirl and without swirl flow for Re=10,000, 15,000, 20,000, and 25,000 along longitudinal sections and the results appear to be physically reasonable. In addition, axial velocity distribution is compared with that of Jeong's, Kodadadi's and Murakami's. It was found that the highest velocity of swirl and non-swirl flow occurs in the opposite position at the center of a round tube, $\phi$=45$^{\circ}$