• 한국안전학회지
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• 제17권1호
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• pp.33-38
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• 2002

SS41 material is welded automatically and is investigated some effects of the welding residual stress on the growth and propagation of fatigue crack, so as to study the fatigue behaviour in the welding residual stress field. The summarized results are as follows; 1) In case of the load amplitude is constant, as the stress ration is changing to 0.1, 0.33 and 0.5 the propagation life is constant but the initiation life decreases. And than, when maximum load or minimum load is constant, s the stress ration increases the initiation life and propagation life. 2) It was shown that the fatigue crack propagation ratio da/dn was almost constant regardless of the stress ratio change at constant load amplitude and that the larger stress ratio, the slower was the fatigue crack propagation ratio. 3) The opening ratio U is influenced by $K_{max}$ but it isn't only the function of $K_{max}$ because data range is very large. 4) The fatigue life of the specimens on tensile compressive residual stress field was decreased and increased respectably more than that of the base metal.

• 가정과삶의질연구
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• 제8권2호
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• pp.101-118
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• 1990

The purpose of this study is to examine the stress level and factors percepted by the married women during family life, and to identify the related variables influencing on stress level. For this purpose, questionnaires were distributed to the 650 married women who have been living in seoul. Among them 463 data were selected. For data analysis, the statistical method such as the factor analysis frequency distribution percentile , t-test, ANOVA, Duncan's Multiple Range Test and Stepwise Regression Analysis were used. the major findings were summarized as follows; 1) The general tendancy of the stress level percepted by the married women during family life was relatively low. 2) The household background variables(age, level of education, income, type of family, number of children, status of employment ) have turned out to be significant on the stress level of married women except family type. 3) All the social-psychological variables(socio-economic status, communication interaction, resources perception, psychological satisfaction) showed significant differences according to the stress level percepted by the married women during family life. 4) The level of work identity was the important factor on the stress level percepted by the married women during family life. 5) In Stepwise Multiple Regression Analysis, the married women's stress level during family life was greatly influenced by variables such as the resource perception and the psychological satisfaction.

• Journal of the Korean Data and Information Science Society
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• 제21권4호
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• pp.813-818
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• 2010

The least squares estimation method for model parameters under failure step-stress accelerated life tests is studied and a numerical example will be given to illustrate the proposed inferential procedures under the compound linear plans proposed as an alternative to the optimal quadratic plan, assuming that the exponential distribution with a quadratic relationship between stress and log-mean lifetime. The proposed compound linear plan for constant stress accelerated life tests and 4:2:1 plan are compared for various situations. Even though the compound linear plan was proposed under constant stress accelerated life tests, we found that this plan did well relatively in failure step-stress accelerated life tests.

• 한국해양공학회지
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• 제7권2호
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• pp.68-78
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• 1993

Fatigue crack shape variation by a residual stress during crack growth and life predition are studied. An analytical method is presented to predict the influence of a residual stress due to heattreatment on crack shape variations. Computer simulation results using this me thod are graphically shown that crack growth rate to surface direction are decreased due to compressive residual stress exisiting in surface area. These results are commpared with experimental results. The fatigue life is also predicted by computer simulation of crack aspect ratio variation which is based on the surface crack length increment per unit cycle calculated from a-N diagram. Predited life is about 12 percent lower than experimental life.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.252-254
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• 2004

Fatigue life a box weldment was predicted with the stress concentration and residual stress using the equation reported. In order to change the stress concentration and residual stress of the box weldment, Post treatments such as smooth grinding of weld bead, weld toe grinding and hammer peening were applied. The fatigue life of the weldment after post treatment clearly increased, which is attributed to the reduction of stress concentration and/or introduction of compressive residual stress at the weld toe. The predicted fatigue life was a relatively good agreement with the experiment for a long fatigue life, while it was underestimated for a short fatigue life.

• 지역사회간호학회지
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• 제27권2호
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• pp.124-131
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• 2016

Purpose: The purpose of this paper was to identify the correlations among academic stress and adjustment at university life in university students. Methods: A total of 489 subjects aged 17 and 36 were selected through convenient sampling. Data were collected with a self reported questionnaire from September 2 to November 30, 2015. Collected data were analyzed with SPSS/WIN. Results: There were statistical differences between academic stress and adjustment at university life. Academic stress were significantly different according to gender, grade, economic status, health status major department of study, drinking and smoking. Adjustment at university life were significantly different according to gender, economic status, health status. 25.4% of variance in adjustment at university life were explained by academic stress, major department of study, health status. Conclusion: The finding of this study may be useful in understanding the academic stress expression of university students and developing more specific programs on adjustment at university life.

• 보건의료산업학회지
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• 제10권4호
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• pp.239-248
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• 2016

Objectives : The purpose of this study was to examine the mediation effects of self-efficacy on the relationship between life stress and depression in university students to provide a basis for planning nursing interventions to improve the mental health of university students. Methods : Data were collected from September 1 to September 30, 2015 by giving a questionnaire to 272 university students. The instruments for this study were life stress, self-efficacy, and depression. The data were analyzed with descriptive statistics, Pearson's correlation coefficients, and multiple linear regression with the SPSS/WIN 18.0 program. Results : There were significant correlations among life stress, self-efficacy, and depression. Additionally, self-efficacy had a mediating effect on the relationship between life stress and depression. Conclusions : Based on the findings of this study, health management programs focusing on stress management and self-efficacy improvement are highly recommended to promote good mental health in university students.

• 원예과학기술지
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• 제33권5호
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• pp.625-632
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• 2015

Drought is a severe abiotic stress that affects global crop production. A drought model was created for 'Toyonoka' Fragaria ${\times}$ ananassa, and the effects of drought stress on contents of proline, sugars, and antioxidant enzyme activities were investigated. Strawberry transplants with identical growth were chosen for the experiments and the randomized design included four replications (10 plants per block). The experimental sets differed in the moisture level of the culture medium relative to the range of moisture content as follows: control, 70-85%; mild drought stress, 50-60%; moderate drought stress, 40-50%; and severe drought stress, 30-40%. Drought stress was imposed by limiting irrigation. Plants were sampled and physiological parameters w ere measured on 0, 2, 4, 6, 8, and 10 days after the commencement of droughts tress. The water potential of strawberry leaves decreased in the plants under mild, moderate, and severe stress during the course of the water stress treatment and exhibited a significant difference from the control. Strawberry leaves subjected to drought stress had higher accumulation of proline, sugars, and malondialdehyde, and higher activities of superoxide dismutase, peroxidase, and catalase than leaves of control plants. Malondialdehyde levels increased in parallel with the severity and duration of drought stress. By contrast, antioxidant enzyme activity displayed dynamic responses to drought stress, first increasing and subsequently decreasing as the severity and duration of drought stress increased. These results suggest that strawberry plants respond to drought stress by altering the activities of antioxidant enzymes and the levels of osmotically active metabolites. These biochemical response changes may confer adaptation to drought stress and improve the capacity of plants to withstand water-deficit conditions.

• 한국간호교육학회지
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• 제24권3호
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• pp.269-278
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• 2018

Purpose: This study was conducted to investigate the correlation between stress and adjustment to college life among nursing students. Methods: The sample consisted of 183 university students in C & S cities. Self-report questionnaires were used to measure the variables. In data analysis, SPSSWIN 23.0 program was utilized for descriptive statistics, Pearson's correlation coefficients, and regression analysis. Results: The mean scores of stress and adjustment to college life were 2.55 and 3.24. Stress was significantly different according to grade (F=7.30, p<.001), economic state (F=14.39, p<.001), perceived health state (F=6.66, p<.001). In regression analysis, stress for college life, perceived health state, and college life satisfaction were significant predictors of adjustment to college life explaining 68%. Conclusion: This study suggests that perceived health state was a significant factor on adjustment to college life among nursing students. Therefore, the strategies of nursing intervention which improve perceived health state must be developed for college students.

• 한국초지조사료학회지
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• 제41권3호
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• pp.162-167
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• 2021

Aluminum (Al) stress in acidic pH is known to decrease the growth and productivity of alfalfa. However, not much is known about how the application of silicon (Si) affects the Al stress response in alfalfa. This study was conducted to evaluate the effect of exogenous application of Si on the growth of alfalfa seedlings exposed to Al stress in pots. Alfalfa seedlings grown in pots for 2 weeks were treated either Al stress (pH 4.0, 0.2 mM Al) or Al stress + Si (1 mM) for 5 days, lengths and biomass of shoot and root, and chlorophyll and carotenoid contents in leaf tissues were analyzed respectively. Al stress treatment inhibited shoot and root growth, and decreased fresh and dry weights, and chlorophyll content in leaves, but increased carotenoid content. In contrast, when alfalfa seedlings treated with Al stress combined with Si, delayed growth caused by Al stress of shoot and root of alfalfa seedlings was restored, dry weight was increased and chlorophyll content of leaf tissue was increased, but carotenoid content was decreased. These results suggest that Si has a function of alleviating Al toxicity in alfalfa, of which it exhibits a mitigating effect by a function that overlaps with some of the intracellular functions of carotenoids.