• Journal of Advanced Marine Engineering and Technology
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• 제29권4호
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• pp.426-435
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• 2005

The lightness of components required in automobile and machinery industries is requiring high strength of components. Therefore this requirement is accomplished as the process of shot-peening method that the compressive residual stress is made on the metal surface as one of various improvement methods. Special research is, therefore, needed about compressive residual stress on the metal surface in the process of shot-peening method. Therefore, in this paper the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in environmental condition(temperature) and mechanical condition(shot velocity, stress ratio) was investigated with considering fracture mechanics. By using the methods mentioned above, the following conclusions have been drawn. (1) The fatigue crack growth rate(da/dN) of the shot-peened material was lower than that of the un-peened one. In high temperature range. fatigue crack growth rate decreased with increasing temperature range, while fatigue crack growth rate increased by decreasing temperature in low temperature. (2) Fatigue life shows more improvement in the shot-peened material than in the un-peened material. And compressive residual stress of surface on the shot-peen processed operate resistance force of fatigue crack propagation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.644-655
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• 2008

Conventional hyperbolic model does not satisfactorily predict the overall stress-strain behaviors of various geomaterials. Tatsuoka and Shibuya(1992) suggest the generalized hyperbolic equation(GHE) considering strain dependency and calculated performance is in good agreement with precise triaxial compression test results of stress-strain relations over wide range of strains before peak stress condition in some cases, but GHE model also does not satisfactorily predict stress-strain relations as strain goes on state of peak stress in most cases. For improve a weak point of the GHE, in this study, modified form of generalized hyperbolic equation (MGHE model) is proposed which can predict highly nonlinear stress-strain behavior for various geomaterials from small strain to peak stress condition.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.1967-1974
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• 2005

The subsurface stress field caused by both normal loads and tangential loads has been evaluated using the rectangular patch solution. The effect of tangential loading on the subsurface stress field has been investigated in detail for both the cylinder-on-cylinder contact and a spur gear teeth contact. For the cylinder-on-cylinder contact, the subsurface stress fields are moved more to the direction of tangential loads and the positions where the maximum stress occur are getting closer to the surface with the increasing tangential loads. The subsurface stress fields of the gear teeth contact are expanded more widely to the direction of tangential loads with the increasing tangential loads. The friction coefficient of a gear teeth contact is low because they are operated in a lubricated condition, and therefore surface tractions in the EHL condition hardly affect on the subsurface stress field.

• 한국식생활문화학회지
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• 제10권5호
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• pp.405-417
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• 1995

This research was designed to see the relationship among nutrient intake, food intake frequency and psychosocial stress in ordinary life. The subjects were 190 males and 263 females of university students in urban areas. There were significant correlations between nutrient intake and stress value, and between food intake frequency and stress value. In male, the more they consumed energy, protein and carbohydrate, the higher they had stress in several categories. But in female the results were reversed. Their stress values were lower when they have consumed protein source food frequently. And in general, stress values of female were higher than those of male. From these results, we conclude that nutrient intake tends to be decresed with increase stress in less stressful condition, but to be increased in more stressful condition.

• Korean Journal of Mathematics
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• 제4권2호
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• pp.179-193
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• 1996

This paper is concerned with the penalized stationary incompressible Navier-Stokes system with the inhomogeneous Dirichlet boundary condition on the part of the boundary. By taking a generalized velocity space on which the homogeneous essential boundary condition is imposed and corresponding trace space on the boundary, we pose the system to the weak form which the stress force is involved. We show the existence and convergence of the penalized system in the regular branch by extending the div-stability condition.

• 대한기계학회논문집A
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• 제37권9호
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• pp.1159-1168
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• 2013

가압형 경수로 원자로의 압력용기 상부헤드 관통노즐 J-groove 용접부 주변에서 일차수응력부식균열(PWSCC)로 인한 냉각수 누설사례가 발생하고 있다. 본 연구에서는 PWSCC 의 주요 원인 중 하나인 용접 잔류응력을 유한요소 해석을 이용해 평가하고 원자력 발전소의 정상가동 조건을 해석에 반영하는 방법이 용접잔류응력 분포에 미치는 영향에 대한 분석을 수행하였다. 또한 반복되는 원자력 발전소의 가동 주기가 용접잔류응력 분포에 미치는 영향을 확인하여 정상가동조건에서의 정확한 용접 잔류응력을 예측할 수 있는 방법을 분석하였다.

• 한국직업건강간호학회지
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• 제10권1호
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• pp.41-54
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• 2001

This study was designed to assess the relationship between occupational stress and health status in a study group of 197 workers employed in four newspaper publishing companies, using a self-adminstrative questionnaire. The types of occupation of them were reporters(79), clerical workers(54), and engineers (64). The studies on workers' health have been focused mainly on the physical, chemical, and biological diseases in our country. Therefore, the study of mental health, especially of occupational stress, is to be carried out. I consider stress as a factor having an effect on the health status of the newspaper employees, who have been well known to have high stress due to time pressures. I expect that this research will be helpful not only for understanding of health status by occupation, but also for making clear the issues that have been raised continuously from the previous researches. The results of this study are as follows; 1. The mean values of stress by occupation were statistically significant; the reporters had the highest stress symptom scores, and the engineers had the lowest levels of stress. The mean values of stress symptoms were higher in the workers who had long working hours. 2. The health status by occupation showed significant differences in gastrointestinal systems and in depression. The clerical workers were healthier than the engineers in gastrointestinal systems, and the reporters were more depressed than the engineers in depression. 3. The health status by the general characteristics, there was a statistical significance as for a gender, marital status, and absenteeism in the gastrointestinal systems. The men, the married, and the workers who had not been absent were more healthy. Only absenteeism had an effect on the problems in optical-dermal systems and in oro-fecal systems. Gender, marital status, absenteeism, and working hours were related with health status : the men. the married, the workers who had not been absent, and the workers who had longer working hours were more healthy. In mental stability, gender had a significant effect : the men were more healthy than the women. In general condition, the men, the older, the married, and the workers who had not been absent were more healthy. 4. Stress level had an effect on the health status in the respiratory systems, optical-dermal systems, oro-fecal system, depression, mental stability, general condition, and health condition. The workers who perceived more stress had more problems in their health status. 5. In the results of the multiple regression analyses, age in the respiratory systems, absenteeism in the optical-dermal systems, occupation and absenteeism in the gastrointestinal systems and in the oro-fecal systems, gender in depression and in mental stability, gender, age, absenteeism, and working hours in the general condition, absenteeism in the health condition had an effect on the health status of the workers.

• 한국직업건강간호학회지
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• 제15권1호
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• pp.58-71
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• 2006

Purpose: This study was performed to identify workers' Job stress status and to analyse the influencing factors. Method: Data were collected from 456 workers with Korean Occupational Stress Questionnaire Short Form(KOSQ SF) and analysed using descriptive statistics, t-test, ANOVA. Results: Total job stress status of men was slightly lower than Korean workers' standard. In case of women, the score of total job stress was lower than Korean workers' standard. The most significant influencing factors to stressors were insufficient sleeping time and self cognitive bad health condition. Among seven domains of job stressors, job demand was affected by 8 characteristics. Conclusion: This study indicated that workers' job stress level were various by their characteristics except workplace size. The development of stress management programs by types of industry is required. On the base of the model program, planning of customized program for every company or employee is required. High job demand, insufficient job control, insufficient sleeping time, bad health condition are the key factors of workers' job stress in this study. The change of workers' health behavior with supportive environment is essential to stress management program. More researches for adding physical environment domain to KOSQ SF are expected.

• 대한기계학회논문집
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• 제18권1호
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• pp.101-112
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• 1994

The measurement of residual stress distribution of $Si_3N_4/SUS304$ joint was performed on 23 specimens with the same joint condition using PSPC type X-ray stress measurement system and the two-dimensional elastoplastic analysis using finite element method was also attempted. As results, residual stress distribution near the interface on the ceramic side of the joint was revealed quantitatively. Residual stress on the ceramic side of the joint was turned out to be tensional near the interface, maximum along the edge, varying in accordance with the condition of the joint and variance to be most conspicuous for the residual stress normal to the interface characterized by the stress singularities. In the vicinity of the interface, the high stress concentration occurs and residual stress distributes three-dimensionally. Therefore, the measured stress distribution differed remarkably from the result of the two-dimensional finite-element analysis. Especially at the center of the specimen near the interface, the residual stress, $\sigma_{x}$ obtained from the finite element analysis was compressive, whereas measurement using X-ray yielded tensile $\sigma_{x}$. Here we discuss two dimensional superposition model the discrepancy between the results from the two dimensional finite element analysis and X-ray measurement.

• Journal of Nutrition and Health
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• 제54권4호
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• pp.373-382
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• 2021

Purpose: For college students, poor eating habits can cause problems with adult health. This study investigated the status of sweet food intake and the degree of stress in college students in the Seoul and Gyeonggi areas to provide a basis for nutrition education by analyzing the relationship between stress and sugar intake. Methods: The subjects were 760 college students, and the survey was conducted using a questionnaire. Statistical analysis for collected data was performed using SPSS (version 21.0). Results: The stress score showed higher stress in female students. Females had more stress in their employment and study-related problems than males. For changes in food intake under stress, the intake was increased greatly in females than in males. For food preference changes before and after stress, males preferred more spicy foods and less salty foods after stress. After stress, females significantly preferred sweeter and spicier foods and less salty, sour, and bitter foods. The intake of sweet foods by stress factors showed that the intake of snacks was higher under the condition of 'worry, fatigue, and tension', and the intake of beverages was increased significantly under the condition of 'anger and aggression'. Conclusion: Sweet foods were preferred under stress, and the amount of intake was increased. Education on food selection and nutrition information should be provided to prevent health problems that can be developed by the reckless intake of sweet foods. Active guidance is needed for college students to select the proper snacks instead of nutritionally insufficient foods to relieve stress.