• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.259-266
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• 2012

In this paper the seismic performance of a flat plate wall system structure was evaluated based on the ATC-63 approach, and the results were compared with those of a wall slab structure having the same size. As analysis model structures, a twelve story flat plate wall structure and a wall slab structure were designed based on the KBC-2009, and their seismic performances and collapse behaviors were evaluated by nonlinear static and incremental dynamic analyses(IDA). It was observed that the flat plate wall structure was designed with smaller amount of reinforced concrete, and showed slightly larger displacement response compared with those of the wall slab structure. The collapse margin ratios of the two structures obtained from the incremental dynamic analyses satisfied the limit states specified in the ATC-63, and the structures turned out to have enough capacity to resist the design level seismic load.

• The Korean Journal of Food And Nutrition
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• v.29 no.3
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• pp.363-370
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• 2016

The purpose of this study is to investigate the dietary life status according to smart device use among university students. In 2015, data was collected during a 3 month survey of the eating behaviors, lifestyles, eating habits, and use of smart devices of 550 university students, as well as their dependency on smartphones. Ultimately, 520 subjects (94.5% analysis rate) were divided into three groups based on their daily use time of smart device: low-use group (<4.7 hours, n=173), medium-use group (${\geq}4.7hours$ and <6.4 hours, n=174), and high-use group (${\geq}6.4hours$, n=173). The more frequent use groups showed a higher level of dependency on the smartphone. Breakfast was found to be the most commonly skipped meal; and the high-use group showed a higher response of irregular meals than low-use group. In assessment of eating habits, the subjects with less smart device usage ate more regularly and at fixed times, did not overeat, drank milk everyday, and did not consume processed food as often. To sum up, more irregularity of meal and undesirable eating habits were found among university students with higher use of smart devices. These results suggest that a control of smart device usage would lead to a more desirable dietary life in university students.

• Composites Research
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• v.16 no.6
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• pp.23-32
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• 2003

Applications of advanced composite material in construction field are tending upwards and development of all composite material bridges is making progress rapidly in home and abroad due to their high strength to weight ratio. This paper formulated the dynamic responses of the laminated composite structures subjected to moving load and analyzed the various dynamic behaviors using the finite element method. The nondimensionalized natural frequencies of a simply supported square-laminated composite plate are considered for verifications. Mode superposition and Newmark direct integration method are applied for moving load analysis. For structural models, dynamic magnification factor calculated for various velocities of the moving load and displacements characteristics of laminated composite structures due to the moving load are investigated theoretically Numerical results are presented to study the effects of lamination scheme, stacking sequence, and fiber angle for laminated composite structures during moving load. The various results on moving load and lamination through numerical analysis will present an important basic data for development and grasp the behavior of all composite material bridges.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.147-153
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• 2012

Precise estimation f a structure's dynamic characteristics is indispensable for ensuring stable dynamic response during life time especially for the structures which can experience resonance such as railway bridges. Especially, concrete track can change the modal properties of the railway bridge, through the contribution of stiffness as well as mass effects, generally only the mass effect is considered in dynamic analysis of the railway bridge. In this paper, static and dynamic behaviors of railway bridge with concrete track were investigated through experimental study. Also, numerical analysis was performed about considering only mass of concrete track and together with stiffness and mass of concrete track. These were compared with experiment value. Numerical analysis value considering together with stiffness and mass of concrete track was similar experiment value. Therefore, when dynamic analysis of railway bridge with concrete track is performed, the contribution of stiffness as well as mass effects for concrete track is considered.

• Journal of the East Asian Society of Dietary Life
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• v.24 no.5
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• pp.552-563
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• 2014

This study was performed to investigate the dietary habits and nutritional knowledge of elementary school students (boy : 250, girl : 250) by gender. Frequency of skipping breakfast was high in both boys and girls. Duration of mealtime was significantly higher for boys compared with girls (p<0.001). Regularity of meals was not significantly different between boys and girls. Reason for irregular meals was 'no appetite' for both boys (39.6%) and girls (40.0%). Unbalanced diet was high in both boys (60.8%) and girls (59.6%), and problems related to dietary habits were in order of 'unbalance diet', 'irregular mealtime', 'overeating', 'skip a meal frequently', and 'eat out frequently'. Frequency of snack intake was significantly higher for girls compared to boys(p<0.05). The criterion for selecting snacks was higher for 'nutrition' compared to 'good taste' for both boys and girls. Frequency of eating out was statistically insignificant, and eating out preferences were in the order of 'Korean food', 'western food', and 'Chinese food'. Eating behavior 'eat meat, fish, egg, tofu every meal' was significantly higher for boys compared to girls (p<0.01). 'Healthful' response rates were 57.6% for boys and 58.8% for girls. Practice level of nutritional knowledge was significantly higher in girls compared to boys (p<0.001). To establish good eating behaviors, we should develop systematic and continuous education programs.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.3
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• pp.51-65
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• 2009

The seismic design concept of RC bridges is to attain the proper ductility of piers, yielding a ductile failure mechanism. Therefore, seismic design force for moment is determined by introducing a response modification factor (R), and lateral reinforcements to confine core concrete are specified in the current design code. However, these design provisions have irrationality, which results in excessive amounts of lateral reinforcements for columns in Korea, which are generally designed with large sections. To improve on these provisions, a new design method based on seismic performance has been proposed. To apply this to hollow sectional columns, however, further investigations and improvements must be performed, due to the different seismic behaviors and confinement effects. In this study, hollow sectional columns with different lap-splice of longitudinal bars and lateral reinforcements have been tested. Seismic characteristics and performance were investigated quantitatively. These research results can be used to derive a performance-based design for hollow sectional columns.

• Korean Journal of Community Nutrition
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• v.11 no.5
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• pp.562-574
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• 2006

The study compared eating and physical activity related behaviors and self-esteem between healthy weight and obese children by presenting 175 primary school students in Busan City and Gyeongsang province with a self-reported questionnaire and Coopersmith's self-esteem inventory. The questionnaire was composed of 25 items, weighted primarily by a Likert scale. The self-esteem inventory presented to the students comprised 25 'Yes' or 'No' response questions to different statements. The study found obese children were more likely to think they always had to control their weight (p=0.000), reportedly measuring their weights significantly more than the healthy weight children. Also the study found that obese children are significantly more likely than healthy weight children to go on a diet, however neither group were successful in losing weight as the duration of the diet in 79.5% of the total sample lasted no longer than one week. In comparison to healthy weight children, obese children reported that they consumed fewer snacks during the day, avoided snacking subsequent to an evening meal and exercised more frequently for as long as physically possible. Interestingly, we found no difference of reported self-esteem between groups, though the obese group were more likely to answer that their parents did not understand them (p=0.055) Based on these findings, we concluded that the obese children who participated in the study were more aware of their body weights than the healthy weights children. It may be necessary to investigate further the relationship between self-esteem and participants' weights while considering other variables such as personality and body image.

• Computational Structural Engineering
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• v.10 no.4
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• pp.281-290
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• 1997

Current seismic design code is based on the assumption that the designed structures would be behaved inelastically during a severe earthquake ground motion. For this reason, seismic design forces calculated by seismic codes are much lower than the forces generated by design earthquakes which makes structures responding elastically. Present procedures for calculating seismic design forces are based on the use of elastic spectra reduced by a strength reduction factors known as "response modificaion factor". Because these factors were determined empirically, it is difficult to know how much inelastic behaviors of the structures exhibit. In this study, lateral strength required to maintain target ductility ratio was first calculated from nonlinear dynamic analysis of the single degree of freedom system. At the following step, base shear foeces specified in seismic design code compare with above results. If the base shear force required to maintain target ductility ratio was higher than the code specified one, the lack of required strength should be filled by overstrength and/or redundancy. Therefore, overstrength of moment resisting frame structure will be estimated from the results of push-over analysis.

• Geomechanics and Engineering
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• v.7 no.4
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• pp.375-401
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• 2014

It is generally accepted that material heterogeneity has a great influence on the deformation, strength, damage and failure modes of rock. This paper presents numerical simulation on rock failure process based on the characterization of rock heterogeneity by using a digital image processing (DIP) technique. The actual heterogeneity of rock at mesoscopic scale (characterized as minerals) is retrieved by using a vectorization transformation method based on the digital image of rock surface, and it is imported into a well-established numerical code Rock Failure Process Analysis (RFPA), in order to examine the effect of rock heterogeneity on the rock failure process. In this regard, the numerical model of rock could be built based on the actual characterization of the heterogeneity of rock at the meso-scale. Then, the images of granite are taken as an example to illustrate the implementation of DIP technique in simulating the rock failure process. Three numerical examples are presented to demonstrate the impact of actual rock heterogeneity due to spatial distribution of constituent mineral grains (e.g., feldspar, quartz and mica) on the macro-scale mechanical response, and the associated rock failure mechanism at the meso-scale level is clarified. The numerical results indicate that the shape and distribution of constituent mineral grains have a pronounced impact on stress distribution and concentration, which may further control the failure process of granite. The proposed method provides an efficient tool for studying the mechanical behaviors of heterogeneous rock and rock-like materials whose failure processes are strongly influenced by material heterogeneity.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.5
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• pp.1-10
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• 2008

A series of shaking table tests were conducted on a 1:12 scale model using scaled Taft N21E earthquake records to investigate the seismic performance of a 17-story high-rise reinforced concrete building structure with a high degree of torsional eccentricity and soft-story irregularities in the bottom two stories. The main characteristics of the behaviors were: (1) a sudden change of the predominant vibration mode from the mode of translation and torsion to the torsional mode after the flexible side underwent a substantial inelastic deformation; (2) an abrupt increase in the torsional stiffness during this change of modes; (3) a warping behavior of the wall in the torsional mode; and (4) a unilateral overturning moment in the transverse direction to the table excitations. In this study, efforts were made to simulate the above characteristics using a nonlinear analysis program, Perform3D. The advantages and limitations are presented with the nonlinear models available in this software, as they are related to the correlation between analysis and test results.