• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.731-740
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• 1998

Orthogonally stiffened steel plates are used for orthotropic steel decks of long-span bridges because of high degree of flexural and torsional resistances and good load-distribution behavior. An analytic study is presented for evaluating the buckling strength of orthogonally stiffened plates subjected to uniaxial compression. By using the plate theory, the buckling stress under overall and partial buckling modes, is derived. Parametric studies are performed to show the effects of the stiffness and the number of transverse and longitudinal ribs on the buckling strength. The results show quantitatively strong influence of stiffness and spacing of longitudinal and transverse ribs.

• Korean Journal of Human Ecology
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• v.16 no.6
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• pp.1107-1118
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• 2007

This study explored the consistency of bullying, victimization and aggressive victimization, the relationships between bullying, victimization and aggressive victimization and overt/relational aggression, and the relationships between bullying groups and overt/relational aggression with gender. The subjects were 4th grade children and 2 years later they were contacted again. Instruments were the Bully-Behavior Scale, the Peer-Victimization Scale and the Peer Nomination Instrument. Bullying, victimization and aggressive victimization were decreased while there were consistencies in overt and relational aggression from 4th to 6th grade. In the correlation analysis, male victims at Time 1 were negatively related to overt and relational aggression at both Time 1 and Time 2. Female bullies were positively related to relational aggression at both Time 1 and Time 2. In the cross-sectional relations of overt aggression with bullying groups, there was a gender difference. In the relational aggression with bullying groups, only bullying groups had a significant difference. In the longitudinal relations of overt aggression with bullying groups, only gender had a significant difference. Males appeared to be more overtly aggressive than females. In the relational aggression, bullying groups, gender, and the interaction between bullying groups and gender had significant differences. Female bullies were more likely to be relationally aggressive than other groups.

• Structural Engineering and Mechanics
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• v.72 no.5
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• pp.597-615
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• 2019

The paper studies the dispersion of the axisymmetric longitudinal wave propagating in the "hollow cylinder + surrounding medium" system with inhomogeneous initial stresses caused by the uniformly distributed radial compressional forces acting at infinity. Up to now in the world literature, there exist only a few investigations related to the wave dispersion in a hollow cylinder with inhomogeneous initial stresses. Therefore, this paper is one of the first attempts in this field in the sense of the development of investigations for the case where the cylinder is surrounded with an infinite medium. The three-dimensional linearized theory of elastic waves is used for describing the considered wave propagation problem and, for a solution to the corresponding mathematical problem, the discrete-analytical solution method is developed and employed. The corresponding dispersion equation is obtained and this equation is solved numerically and, as a result of this solution, the dispersion curves are constructed for the first and second modes. By analyzing these curves, the character of the influence of the inhomogeneous initial stresses on the dispersion curves is established. In particular, it is established that as a result of the inhomogeneity of the initial stresses both new dispersion curves and the "band gap" for the wave frequencies can appear.

• Journal of Korea Foresty Energy
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• v.18 no.1
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• pp.1-5
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• 1999

Variations in the wood quality were analyzed to utilize Korean pine (Pinus koraiensis S. et Z.) efficiently and to develop suitable use, depending on the stem location. Variations in the tracheid length and width, microfibril angle, compression strength were measured at the heights of 0.3, 1.3, 2.3, and 5.3m in the longitudinal direction of the 20m pine and they were analyzed by Duncan`s multiple range test. Variations in the tracheid length, width and compression strength did not show significant difference, whereas those in the microfibril angle showed significant difference. However, the microfibril angle did not vary with the height of trees, showing inconsistent pattern in change.

• Human Ecology Research
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• v.54 no.5
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• pp.551-564
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• 2016

This study examined the causal relationship between a mothers' depression and the emotional problems of their preschool-aged children as indicated by anxiety, depression and emotional reactivity. We analyzed data from 1,528 mothers and their children from the Panel Study of Korean Children (PSKC) collected when the children were 4 years old and 5 years old. Autoregressive cross-lagged modeling was conducted using AMOS ver. 23.0 to investigate the longitudinal reciprocal effects between mothers' depression and children's emotional problems. The results indicated that both mothers' depression and children's emotional problems were relatively stable between the ages of 4 to 5. There were significant cross-lagged effects from the mothers' depression to children's emotional problems and from children's emotional problems to mothers' depression. Mothers reported higher levels of depression when the children were 4 years old and the children showed more anxiety, depression and emotional reactivity when they were 5 years old. Emotional problems when the children were 4 predicted greater depression among mothers 1 year later. We also examined the group difference (between boys and girls) in the study model. Gender differences were not statistically supported. The results suggested that early assessment and intervention for mothers' depression and children's emotional problems are essential for a healthy mother-child relationship and later child outcomes.

• Human Ecology Research
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• v.58 no.3
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• pp.343-356
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• 2020

This paper examines the associations of having a helper for domestic work or childcare and time spent on it by couples in South Korea. We use five waves of panel survey data from the Korean Longitudinal Survey of Women and Families (KLoWF), which allows longitudinal changes within couples over time that account for potential selection effects and unobserved heterogeneity among individuals. With fixed effects, we find outsourcing is associated with a decrease in wife's time spent on domestic work or childcare by 1 hour per week. However, the decrease is concentrated on the unemployed wife's time, but not employed wife's time. In addition, outsourcing is not a significant factor for husband's time and the husband's share of total contribution. This may be because wives are the main provider of domestic work and childcare in Korea regardless of employment status or having any helper. Due to unequal contributions between husband and wife, using outsourcing also neither alleviates the employed wife's contribution nor changes the husband's contribution. However, the results may be underestimated because there are more common and diverse types of outsourcing in a broad sense, such as going out for dinner, buying prepared food, and using dry cleaning services. We expect future studies to consider more broad types of outsourcing and examine how relations with the couple's time use at home are different by type.

• Women's Health Nursing
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• v.12 no.1
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• pp.53-60
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• 2006

Purpose: This study aimed to explore changes in symptom distress and functional status in gynecologic cancer patients during the entire treatment cycles of chemotherapy. Methods: A prospective and longitudinal study with repeated measures was designed. Symptom Distress Scale and Karnofsky Performance Status Index were included in a daily log developed for self-administration. A total of 39 patients with a mean age of 48.4 years participated. Results: The levels of symptom distress and functional status changed significantly over the six cycles. Symptom distress kept increasing until its peak at the fourth cycle, while the functional status scored lowest at the first cycle, then it improved as the cycle repeated. In each cycle, symptom distress was marked higher during the first 6 days accompanying poor functional status. However, both changes did not recover completely until the end of each cycle. Conclusion: Nursing assessment and intervention need to be provided based on these changing patterns to help cancer patients cope and adjust successfully during the long treatment period. Further studies are needed to examine the impact of the major symptoms on psychological responses, quality of life, and outcomes of the cancer treatments.

• International Journal of Aeronautical and Space Sciences
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• v.2 no.2
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• pp.95-107
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• 2001

This paper is devoted to the parameter optimization of unmanned aerial vehicle's (UAV) flight control laws. Optimization procedure is based on the ideas of mixed $H_2/H_{\infty}$ control of multi-model plants. By using this approach, some partial $H_2$-terms defining the performance of nominal and parametrically perturbed Flight Control System (FCS) responses to deterministic command signals in stochastic atmosphere as well as $H_{\infty}$-terms defining robustness of the FCS can be incorporated in the composite cost function. Special penalty function imposed on the location of closed-loop system's poles keeps the speed of response and oscillatory properties for both nominal and perturbed FCS in reasonable limits. That is the reason why this procedure may provide reasonable trade-off between the performance and robustness of FCS that are very important especially for UAV. Its practical importance is illustrated by case studies of lateral and longitudinal control of small UAV.

• The Korean Journal of Health Service Management
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• v.14 no.1
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• pp.137-146
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• 2020

Objectives: The aim of this study was to investigate cognitive function decline by socio-demographic and health-related characteristics (health behaviors and health status) using 5th Korean Longitudinal Study of Aging panel data. Methods: The subjects were 4,440 community-dwelling people aged over 57 years. The data were analyzed with descriptive statistics, frequency analysis, χ²-test, and binary logistic regression analysis using SPSS ver. 25.0. Results: The findings revealed that socio-demographic characteristics (gender, age, area of residence, educational level, marital status, number of children, number of grand-children) and health-related characteristics (smoking, drinking, regular exercise, weight category by body mass index, hypertension and diabetes mellitus) were factors that influenced cognitive function decline (p<.05). Conclusions: Cognitive function decline was closely related to health behaviors and disease types. Future studies must examine related constructs to accurately determine these relationships among various populations. The present study could be used as a tool for the development and implementation of health promotion and prevention strategies.

• Structural Engineering and Mechanics
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• v.37 no.3
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• pp.297-307
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• 2011

Meck Plot is an adapted version of the well-known Southwell method to the case of lateral-torsional buckling, which indeed reflects the physical inter-dependence of lateral flexure (lateral displacement) and torsion (rotation) in the structure. In the recent reported studies, it has been shown experimentally and theoretically that lateral displacement of an I-beam undergoing elastic lateral-distortional mode of buckling is interestingly directly coupled with other various deformation characteristics such as web transverse strain, web longitudinal strain, vertical deflection, and angles of twist of top and bottom flanges, and consequently good results have been obtained as a result of application of the Meck's method on lateral displacement together with each of the aforementioned deformation variables. In this paper, it is demonstrated that even web transverse and longitudinal strains, vertical deflection, and angles of twist of top and bottom flanges of an I-beam undergoing elastic lateral-distortional buckling are two-by-two directly coupled and the application of the Meck Plot on each pair of these deformation variables may still yield reliable predictions for the critical buckling load.