• 한국학교ㆍ지역보건교육학회지
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• 제23권3호
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• pp.15-28
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• 2022

Objectives: This study aims to examine factors affecting depression of adolescents by using the data of the 17th Korean Youth Health Risk Behavior Survey(2020). Methods: The total sample was 54,848 students who are in middle or high school. In this study, sociodemographic variables, health behavior variables, and stress were input to examine the effect on depression. The data was analyzed with χ²-test and hierarchical regression by SPSS statistic program. Results: The results showed that depression was related to sociodemographic factors, health behaviors, and stress factors. In the result of hierarchical regression analysis, it was found that not only stress but also other variables had an effect on depression, which had a statistically significant effect. Conclusions: It was found that there are various causes such as environmental aspects and health behaviors that surround adolescents' depression rather than a single factor such as stress. Also, stress and depression are reciprocal rather than causal. Adolescents should be subdivided into groups such as grade, gender, or academic performance to relieve stress and depression at the same time through specific interventions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.73-78
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• 2004

In this research, the photoelastic experimental hybrid method with Hook-Jeeves numerical method has been developed: This method is more precise and stable than the photoelastic experimental hybrid method with Newton-Rapson numerical method with Gaussian elimination method. Using the photoelastic experimental hybrid method with Hook-Jeeves numerical method, we can separate stress components from isochromatics only and stress intensity factors and stress concentration factors can be determined. The photoelastic experimental hybrid method with Hook-Jeeves had better be used in the full field experiment than the photoelastic experimental hybrid method with Newton-Rapson with Gaussian elimination method.

• Structural Engineering and Mechanics
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• 제20권3호
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• pp.335-346
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• 2005

The T-stress of cracks in elastic sheets is solved by using the fractal finite element method (FFEM). The FFEM, which had been developed to determine the stress intensity factors of cracks, is re-applied to evaluate the T-stress which is one of the important fracture parameters. The FFEM combines an exterior finite element model with a localized inner model near the crack tip. The mesh geometry of the latter is self-similar in radial layers around the tip. The higher order Williams series is used to condense the large numbers of nodal displacements at the inner model near the crack tip to a small set of unknown coefficients. Numerical examples revealed that the present approach is simple and accurate for calculating the T-stresses and the stress intensity factors. Some errors of the T-stress solutions shown in the previous literature are identified and the new solutions for the T-stress calculations are presented.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.197-204
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• 1999

The boundary element method was used for studying singularities of an interface crack with contact zones. The iterative procedure is applied to estimate the contact zone size. Because the contact zone size was extremely small in a tension field, a large number of Gaussian points were used for numerical integration of the Kernels. Stress extrapolation method and J-integral were used ofr determining stress intensity factors. When the interface crack was assumed to have opened tips, oscillatory singularities appear near the tips of the interface crack. But the interface crack with contact zone which Comninou suggested had no oscillatory behavior. The contact zone size under shear loading was much larger than that under tensile. The stress intensity factors computed by stress extrapolation method were close to those of Comninou's solution. And the stress intensity factor evaluated by J-integral was similar to that by stress extrapolation method.

• Corrosion Science and Technology
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• 제20권1호
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• pp.22-25
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• 2021

In the past, Alloy 600 nickel-based alloys have been widely used in steam generators. However, most of them have been replaced by thermally treated alloy 690 tubes in recent years because mill annealed alloy 600 materials are known to be susceptible to stress corrosion cracking. Unlike this general perception, some steam generators using mill annealed alloy 600 tubes show excellent performance even though they are designed, manufactured, and operated in the same way. Therefore, various analyses were carried out to determine causes for the degradation of steam generators. Based on the general stress corrosion cracking mechanism, tube material susceptibility, residual stress, and sludge deposits of steam generators were compared to identify factors affecting stress corrosion cracking. It was found that mill annealed alloy 600 steam generator tubes showed higher resistance to stress corrosion cracking when the amount of sludge deposits on tube surface was smaller and residual stress generated during the fabrication was lower.

• 대한통합의학회지
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• 제11권1호
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• pp.167-175
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• 2023

Purpose : The purpose of this study was to identify the degree of occupational therapist's sleep quality and examine the correlation between sleep quality and job stress. We also investigated the effects of the occupational therapist's sleep quality on job stress. Therefore, we aimed to investigate the importance of sleep quality and find a way to reduce job stress in occupational therapists. Methods : We conducted a study from November 7 to from December 23, 2022. To assess sleep quality and job stress, sleep quality of scale and Korean occupational stress scale-SF (KOSS-SF) were used. The general characteristics, sleep quality, job stress were examined using a frequency analysis and presented with descriptive statistics. The pearson correlation coefficient was used to determine, whether there was a correlation between sleep quality and job stress. To find what factors have and effect on job stress, we conducted a multiple regression analysis. A significance level of α=.05 was used to verify statistical significance. Results : First, average sleep quality score was 2.10±.19. Second, a significant correlation was found between sleep quality and job stress (p<.01). And As a result of the relationship between sleep quality sub-factors and job stress, day time dysfunction (r=.23, p<.01), restoration (r=.18, p<.05), difficulty of falling asleep (r=.38, p<.01). difficulty of awakening (r=.36, p<.01), satisfaction (r=.33, p<.01) and difficulty of maintaining sleep (r=.24, p<.05) showed a statistically significant relationship with job stress. Third, the sub-factors of sleep quality influencing job stress were difficulty of falling asleep (β =.26, p<.01), difficulty of awakening (β=.23, p<.01) and satisfaction (β=.21, p<.01). Conclusion : The results of this study, demonstrated the importance of sleep quality in affecting job stress. Therefore, follow-up studies are, necessary to develop interventions to improve, occupational therapist's sleep quality in the future.

• 비파괴검사학회지
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• 제8권1호
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• pp.22-29
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• 1988

The optical method of reflected and transmitted caustics has been utilized in mechanics investigations. This relatively new experimental technique has been successfully applied on various fracture analysis such as static and dynamic c rack propagation studies, some elasticity problems and contact stress, etc, In this study, the stress intensity factors in thin polycarbonate specimens, a kind of optically anisotropic material, under Mode I loading condition are estimated by the method of caustics. The values of stress intensity factors obtained from theoretical caustics shape are compared by the experiment. It is confirmed that the two stress intensity factors agree well with Srawley's solution.

• 대한기계학회논문집
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• 제4권3호
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• pp.113-118
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• 1980

Stresses were calculated for finite-width orthotropic laminates with a circular hole and remote uniaxial loading using a two-dimensional finite-element analysis with both uniform stress and uniform displacement boundary conditions. Five different laminates were analyzed: quasi-isotropic [0.deg./.+-.45.deg./90.deg.].$\_$s/, 0.deg., 90.deg., [0.deg./90.deg.]$\_$s/, and [.+-.45.deg.]$\_$s/, Computed results are presented for selected combinations of hole diameter-sheet-width ratio d/w and length-to width ratio L/w. For small L/w values, the stress-concentration factors K$\_$tn/ were significantly different for the uniform stress and uniform displacement boundary conditions. Typically, for the uniform stress conditions, the K$\_$tn/ values were much larger than for the infinite-strip reference conditions; however, for the uniform displacement conditon, they were only slighty smaller than for this reference. The results for long strips are also presented as width-correction factor. For d/w.leg.33, these width-correction factors are nearly equal for all five laminates.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.183-188
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• 2007

In this paper, we propose a 2D-FE model in single impact with combined physical factors to obtain a unique residual stress by shot peening. Applied physical parameters include elastic-plastic deformation of shot ball, material damping coefficients, strain rate, dynamic friction coefficients. Single impact FE model consists of 2D axisymmetric elements. The FE model with combined factors showed converged and unique distributions of surface stress, maximum compressive residual stress and deformation depth. Further, in contrast to the FE models with rigid shot and elastic deformable shot, FE model with plastic deformable shot produces residual stresses very close to experimental solutions by X-ray diffraction. We therefore validated the 2D FE model with combined peeing factors and plastic deformable shot. This FE model will be a base of the 3D FE model for residual stresses by multi-impact shot peening.

• 보건의료산업학회지
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• 제7권3호
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• pp.111-123
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• 2013

The purpose of this study was to identify factors affecting stress and adaptation in newborn congenital heart disease patients of parents. Data were obtained through questionnaires from 181 newborn congenital heart disease inpatients of parents from P university in Y city. The data were analyzed SPSS 18.0, using descriptive statistics, Pearson correlation coefficients and stepwise multiple regression. Stress was negative correlated with level of patents adaptation. Social support, marital communication and family cohesion were positive correlated with level of patents adaptation. The explained variances for patents adaptation were 45.2% and factors affecting patients adaptation were congenital heart disease, family cohesion, stress, social support and marital communication. Educational intervention program for parents of newborn with congenital heart disease, reduce stress, and to increase the adaptation will be developed.