• Korean Journal of Childcare and Education
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• v.9 no.2
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• pp.357-377
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• 2013

This study aims to look for care quality factors reduce the daily stress of young children placed in care centers for long hours. Therefore, the research questions look into how the hours and care quality factors in child care centers affect young children's daily stress, and whether the care quality factor moderates the impact of the hours children spent in centers. The subjects in this study were 380 children from 3 to 5 years old from 10 child care centers. The Korean Preschool Daily Stress Scale(KPDSS) for children's daily stress and Early Childhood Environmental Rating Scale-Revised(ECERS-R) for quality of each classroom of centers were implemented. The main findings were summarized as following: (1) The more hours he/she spent in the center, the more stress he/she had. Children who spent 9 hours or more had more stress than children with 7 hours or less. (2) Among the 7 quality factors including space and furnishings, personal care routines, language reasoning, activities, interaction, program structure, parents staff, the interaction level between a teacher and a child and the level of parents and staff had the most impact on children's daily stress. (3) The qualitative factors of child care, language reasoning level, interaction level, parental support, and level of teachers reduced children's daily stress which was affected by the hours they spent in centers. Thus in order to reduce the daily stress of children who attend more than 9 hours a day, it is crucial to promote language reasoning activities and interaction between teachers and children and to improve parental support and teachers' professionalism.

• Structural Engineering and Mechanics
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• v.63 no.6
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• pp.713-723
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• 2017

As a new type of ballastless track, longitudinal continuous slab track (CST) has been widely used in China. It can partly isolate the interaction between the ballastless track and the bridge and thus the rail expansion device would be unnecessary. Compared with the traditional track, CST is composed of multi layers of continuous structures and various connecting components. In order to investigate the performance of CST on a long-span bridge, the spatial finite element model considering each layer of the CST structure, connecting components, bridge, and subgrade is established and verified according to the theory of beam-rail interaction. The nonlinear resistance of materials between multilayer track structures is measured by experiments, while the temperature gradients of the bridge and CST are based on the long-term measured data. This study compares the force distribution rules of ballasted track and CST as respectively applied to a long span bridge. The effects of different damage conditions on CST structures are also discussed. The results show that the additional rail stress is small and the CST structure has a high safety factor under the measured temperature load. The rail expansion device can be cancelled when CST is adopted on the long span bridge. Beam end rotation caused by temperature gradient and vertical load will have a significant effect on the rail stress of CST. The additional flexure stress should be considered with the additional expansion stress simultaneously when the rail stress of CST requires to be checked. Both the maximum sliding friction coefficient of sliding layer and cracking condition of concrete plate should be considered to decide the arrangement of connecting components and the ultimate expansion span of the bridge when adopting CST.

• International Journal of Highway Engineering
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• v.19 no.4
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• pp.19-25
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• 2017

PURPOSES : In this paper, the flow of construction material was simulated using computational fluid dynamics in a 2D axisymmetric condition to evaluate the effect of initial or varying material properties on the final shape of a specimen. METHODS : The CFD model was verified by using a well-known analytical solution for a given test condition followed by performing a sensitivity analysis to evaluate the effect of material properties on the final shape of material. Varying dynamic viscosity and yield stress were also considered. RESULTS : The CFD model in a 2D axisymmetric condition agreed with the analytical solution for most yield stress conditions. Minor disagreements observed at high yield stress conditions indicate improper application of the pure shear assumption for the given material behavior. It was also observed that the variation of yield stress and dynamic viscosity during curing had a meaningful effect on the final shape of the specimen. CONCLUSIONS : It is concluded that CFD modeling in a 2D axisymmetric condition is good enough to evaluate fluidal characteristics of material. The model is able to consider varying yield stress and viscosity during curing. The 3D CFD-DEM coupled model may be required to consider the interaction of aggregates in fluid.

• Journal of Integrative Natural Science
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• v.12 no.4
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• pp.127-132
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• 2019

Programmed cell death 4 (PDCD4) is a novel tumor suppressor that function in the nucleus and the cytoplasm and appears to be involved in the regulation of transcription and translation. Stress granules (SGs) are cytoplasmic foci at which untranslated mRNAs accumulate when cells exposed to environmental stresses. Since PDCD4 has implicated in translation repression through direct interaction with eukaryotic translation initiation factor 4A (eIF4A), we here investigated if PDCD4 has a functional role in the process of SG assembly under oxidative stresses. Using immunofluorescence microscopy, we found that PDCD4 is localized to SGs under oxidative stresses. Next, we tested if knockdown of PDCD4 has an effect on the assembly of SG using PDCD4-specific siRNA. Interestingly, SG assembly was accelerated and this effect was caused by sensitization of phosphorylation of eIF2α and dephosphorylation of eIF4E binding protein (4E-BP). These results suggest that PDCD4 has an effect on SG dynamics and possibly involved in cap-dependent translation repression under stress conditions.

• Interaction and multiscale mechanics
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• v.1 no.4
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• pp.437-448
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• 2008

This paper examined the stability of high-dense dislocation substructures (HDDSs) associated with martensite laths in High Cr steels supposed to be used for FBR, based on a series of dislocation dynamics (DD) simulations. The DD simulations considered interactions of dislocations with impurity atoms and precipitates which substantially stabilize the structure. For simulating the dissociation processes, a point defect model is developed and implemented into a discrete DD code. Wall structure composed of high dense dislocations with and without small precipitates were artificially constructed in a simulation cell, and the stability/instability conditions of the walls were systematically investigated in the light of experimentally observed coarsening behavior of the precipitates, i.e., stress dependency of the coarsening rate and the effect of external stress. The effect of stress-dependent coarsening of the precipitates together with application of external stress on the subsequent behavior of initially stabilized dislocation structures was examined.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.709-714
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• 1999

The objectives of this study are to estimate the strengthening effect of concrete column strengthened with CFS and to provide basic guideline for the strengthening design with laminated composite materials. Analysis stress-strain model of laminated CFS is presented based on laminate theory. This model has been implemented in the algorithm of evaluating confinement effect of CFS. From results of the algorithm, stress-strain relationship of confined concrete is obtained. Using this stress-strain relationship, section analyses of circular and rectangular concrete columns strengthened with CFS are carried our, and load-moment interaction and load-ductility curves of the columns are obtained. To evaluate the strengthening effects of CFS, parametric study is also conducted for the angle of ply, thickness of CFS, shape of section, and reinforcement ratio. Based on this investigation, design recommendations and basic guidelines for the strengthening design with CFS are proposed.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.775-784
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• 2017

This study is devoted to developing many new substructure models for ballasted railway track by using the pyramid model philosophy. As the effect of railway embankment has been less considered in the previous studies in the field of vehicle/track interaction, so the present study develops the pyramid models in the presence of railway embankment and implements them in vehicle/track interaction dynamic analyses. Considering a moving car body as multi bodies with 10 degrees of freedom and the ballasted track including rail, sleeper, ballast, subgrade and embankment, two categories of numerical analyses are performed by considering the new substructure systems including type A (initiation of stress overlap areas in adjacent sleepers from the ballast layer) or type B (initiation of stress overlap areas in adjacent sleepers from the subgrade layer). A comprehensive sensitivity analyses are performed on effective parameters such as ballast height, sleepers spacing and sleeper width. The results indicate that the stiffness of subgrade, embankment and foundation increased by increasing the ballast height. Also, by increasing the ballast height, rail and ballast vertical displacement decreased.

• The Journal of the Korea Contents Association
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• v.17 no.12
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• pp.25-33
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• 2017

An increase of the interaction speed can lead to the problem of over-relations. Due to psychological and temporal burdens caused by the excessive relationship, users feel fatigue and users are avoiding using SNS. SNS fatigue and SNS anxiety is regarded as SNS stress related to the side effects caused by the SNS use. This study is to approach negative view which is SNS stress and find out causes of stress from the over-relation of interaction. This study used total of 261 samples from Facebook users. As a results, all hypothesis are accepted using SEM(Structural Equation Model). Information sharing and communication have positive effect on social interaction overload and it causes technostress. The results of this study show that SNS characteristics occurs technostress. This study is significant in that it examines that the features of SNS have negative results.

• The Journal of the Korea Contents Association
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• v.21 no.6
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• pp.261-273
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• 2021

This study analyzed the model by using the data of 416 counselors working in the counseling field to verify the moderated mediation effect of burnout on life satisfaction, through counselors' self-care in the process of counselors' stress. First, counselors' stress had an effect on life satisfaction through burnout. Second, the interaction effect between counselors' stress and self-care was significant and the relationship between stress and burnout was changed according to the level of self-care. Third, counselors' stress was found to be controlled by self-care, which has a mediating effect on life satisfaction through burnout. The results of this study are meaningful in that it provides an empirical basis for self-care factors that can contribute to the improvement of the counselor's personal and professional growth and quality of life through the verification of the effect of self-care that improves the satisfaction of life by preventing and alleviating the stress and burnout of the counselors.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.2
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• pp.27-32
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• 2014

Since the collapse of historical masonry structures in Europe in the late 1990's, the interests in understanding the long-term effect of masonry under sustained compressive stresses have increased. That requires combining the significance of time-dependent effects of creep with the effect of damage due to overstress to realize the evolution of cracks and then failure in masonry. Meanwhile, composite analysis of masonry columns was proven effective for realizing ultimate strength capacity of masonry column. In this study, a simplified mechanical model with step-by-step in time analysis was proposed to incorporate the interaction of damage and creep to estimate the maximum stress occurred in masonry. It was examined that the interaction of creep and damage in masonry can accelerate the failure of masonry.