• Steel and Composite Structures
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• 제46권6호
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• pp.805-821
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• 2023

This study developed an evaluation system to explore the effect of the environmental temperature on the stress redistribution produced by cable stress relaxation of structural members in a steel cable-stayed bridge. The generalized Maxwell model is used to estimate stress relaxation at different temperatures. The environmental temperature is represented using the thermal coefficients and temperature loads. The fmincon optimization function is used to determine the set of stress relaxation parameters at different temperatures for all cables. The ABAQUS software is employed to investigate the stress redistribution of the steel cable-stayed bridge caused by the cable stress relaxation and the environmental temperature. All of these steps are set up as an evaluation system to save time and ensure the accuracy of the study results. The developed evaluation system is then employed to investigate the effect of environmental temperature and cable type on stress redistribution. These studies' findings show that as environmental temperatures increased up to 40 ℃, the redistribution rate increased by up to 34.9% in some girders. The results also show that the cable type with low relaxation rates should be used in high environmental temperature areas to minimize the effect of cable stress relaxation.

• 대한한방부인과학회지
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• 제19권4호
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• pp.93-116
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• 2006

Purpose : This study is to examine the effects of Hwaganjeon water extract(HGJ) on immobilization-stress or cold-stress in BALB/C mice. Methods : We have Hwaganjeon water extract(HGJ) by freeze-dryer & melt it by a saline solution. We feed HGJ 500mg/Kg to 5mice, and add immobilization-stress by putting mice in plastic cylinder 10 hours, and add cold-stress by putting mice in $4^{\circ}C$ cold room 6 hours. Results : 1. HGJ decreased the serum level of histamine and corticosterone increased by immobilization-stress or cold-stress. HGJ inhibited the release of histamine from mast cells at the concentration of 1 mg/ml. 2. HGJ did not affect the cell viability of thymocytes decreased by immobilization-stress or cold-stress, but increased the cell viability of splenocytes decreased by immobilization-stress or cold-stress. 3. HGJ decreased the population of splenic $CD4^{+}$ and $CD8^{+}$cells increased by immobolization-stress or cold-stress. 4. HGJ enhanced the production of ${\gamma}$-interferon(IFN) and interleukin(IL)-2 decreased by immobilization-stress or cold-stress. Conclusion : These results indicate that HGJ may be useful for the prevention and treatment of stress via suppression of serum histamine and corticosterone level and enhancement of immune response.

• 한국보육지원학회지
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• 제13권3호
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• pp.103-119
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• 2017

Objective: This study investigated the relationships between preschoolers' difficult temperament, resilience, problematic behaviors, and maternal parenting stress. In addition, the research examined the moderating effects of resilience on the relationships between maternal parenting stress, preschoolers'difficult temperament and problematic behaviors Methods: The participants were 200 four to six year olds attending kindergartens and daycare centers in Seoul, Gyeonggi-do, or Gangwon-do. Mothers completed the questionaries to measure children's temperament, parenting stress, and problem behaviors. Children's resilience was assessed by teacher ratings. Results: Significant correlations were found among maternal parenting stress, preschoolers' difficult temperament and problematic behaviors. Moreover, resilience moderated the associations between difficult temperament and problematic behaviors but it did not moderate the relation between maternal parenting stress and problematic behaviors. Conclusion/Implications: The results suggest that it is necessary to provide comprehensive intervention to reduce maternal parenting stress and improve preschoolers'resilience in order to prevent their problematic behaviors.

• Journal of Welding and Joining
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• 제15권4호
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• pp.187-193
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• 1997

In the weldmentsm the crack propagation rate is changed due to the residual stress. The crack propagation rate is high in the region with the residual stress. However it shows rhw same behavior with the base metal in the region that does not include the residual stress. The fatigue crack growth rate for the material with residual stresses can be predicted more precisely by using the effective stress ratio. The difference between experimental results and prediction results in the initial stage seems to be due to the redistribution of residual stresses and microstructural change.

• 아동학회지
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• 제35권3호
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• pp.1-14
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• 2014

This study examined the moderated mediating effect of stress by self-concept on the influence of ego-resiliency on school adjustment in children. The participants consisted of 278 4th-graders, who completed self-report questionnaires designed to assess ego-resiliency, school adjustment, self-concept, and stress. The results indicated the following: First, stress mediated the effect of ego-resiliency on school adjustment. Second, self-concept moderated the effect of stress on school adjustment. Third, the mediating effect of stress on the influence of ego-resiliency on school adjustment was moderated by self-concept. The mediating effect of stress was statistically significant when self-concept was positive, but was not statistically significant when self-concept was negative. Methods to improve children's school adjustment are also included, based on the results of this research.

• 지역사회간호학회지
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• 제19권3호
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• pp.368-377
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• 2008

Purpose: The Purpose of this study was to investigate the effects of perceived stress on cognition in the community elderly. Methods: This was a descriptive study. Data were collected using individual-based interviews from 40 senior residents at the hall for the elderly in S City. The period of data collection was from June 19 to July 7, 2006. The tools of data collection were Mini-Mental State Examination (Folstein, Folstein, & McHugh, 1975) and Perceived Stress Scale (Cohen, Kamarck, & Mermelstein, 1983). Results: Cognition showed significant differences according to gender education, and regular exercise. Cognition was significantly correlated to stress and age. Stress was significantly correlated to orientation, recall, and attention/calculation. In the results of stepwise multiple regression, factors affecting cognition were stress, age, and gender. Conclusion: It is necessary to prepare health promotion programs that can reduce stress level in the community elderly.

• 한국생산제조학회지
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• 제6권2호
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• pp.26-33
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• 1997

In this study effect of residual stress and its redistribution in weldment on the fatigue crack propagation was investigated. Fatigue tests were conducted by the center notched specimens machined with welded plate. The residual stress and its redistribution after the crack growth were measured by the magnetizing stress indicator and hole-drilling method. Fatigue crack propagation was estimated by the specimens having residual stress redistributed after the cracks growth and having the effects of crack closure. Crack growth rates were predicted and compared with experimental results. It had been found that the predicted crack propagation rates have a good agreement with experimental results when the redistribution of residual stress was considered.

• 대한기계학회논문집A
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• 제27권1호
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• pp.1-7
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• 2003

The optimal design for the shape of MIL-S-46119 ring obturator under the high pressure using parameter stud:』 on the stress analysis considering effects of design variable is presented, and it is compared to experimental results. The trends of parametric study are in good agreement with the experimental results. The more thickness the higher stress. The more taper the higher stress. And maximum stress of circumferential surface is larger than maximum stress of forward surface. The design variable!; are such as thickness, taper, radius of shape of the obturator. In order to optimize the shape of obturation ring, the weight is maximized subject to maximum stress of the obturator within allowable stress. The design constraints are geometric elements of design variables.

• 대한기계학회논문집A
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• 제28권9호
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• pp.1328-1336
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• 2004

According to our fatigue tests carried out at 20 Hz, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short life range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

• 한국농공학회논문집
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• 제48권7호
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• pp.35-43
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• 2006

This study was carried out to investigate the liquefaction behaviour and predict deviator stress with matric suction, of unsaturated silty sand. The unsaturated soil tests were conducted using a modified triaxial cell and specimens were prepared using the moisture tamping method. The axis translation technique was used to create the desired matric suctions in the specimen. Undrained triaxial compression tests were carried out at matric suction of 0, 2, 5, 10 and 25 kPa. The specimens were sheared to axial strains of about 20% to obtain steady state conditions. The results showed that liquefaction of silty sand only occurs at matric suction of 0 kPa and 2 kPa. The results also show that at matric suctions of 5, 10 and 25 kPa, the resistance to liquefaction increases. As the suction increases, the undrained effective stress path approached the drained stress path. Also, the predicted and measured maximum deviator stress for unsaturated soils using the effective stress concept showed good agreement as matric suction increases. The deviator stress increase is nonlinear as matric suction increases.