• Tribology and Lubricants
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• 제31권6호
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• pp.272-280
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• 2015

Recently, Luu suggested fatigue life equation that uses every term of the Crossland equation with stress gradient effect. Luu’s model, however, has a limit of being unable to coverage small radii that are less than a specified length. Furthermore, rolling model has a very small contact area compared to the rolling element size, and fatigue failure occurs on the small radius such as surface asperity by cyclic loading. Therefore, it is necessary to modify fatigue life equation in order to enable fatigue analysis for a small radius. In this paper, the fatigue life considering a stress gradient effect in rolling contact was obtained using Luu’s modified equation. Fatigue analysis was performed to study the effect of stress gradient on the fatigue life using newly adopted equation and to compare the results with pervious models. In order to do this, a series of simulation such as surface stress analysis, subsurface stress analysis, and fatigue analysis are conducted for two rolling balls of same size that contact each other. Through such a series of processes, the fatigue life can be calculated and equation that is proposed in this paper evaluates the fatigue life in case the contact area is small.

• International Journal of Reliability and Applications
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• 제17권1호
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• pp.85-105
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• 2016

In this paper accelerated life testing is incorporated in quality control technique of acceptance sampling plan to induce early failures in high reliability products.Stress under accelerated condition can be applied in constant-stress, step-stress and progressive-stress or combination of such loadings. A ramp-stress results when stress is increased linearly (from zero) with time. In this paper optimum failure-censored ramp-stress accelerated life test sampling plan for log-logistic distribution has been formulated with cost considerations. The log-logistic distribution has been found appropriate for insulating materials. The optimal plans consist in finding optimum sample size, sample proportion allocated to each stress, and stress rate factor such that producer's and consumer's interests are safeguarded. Variance optimality criterion is used when expected cost per lot is not taken into consideration, and bilevel programming approach is used in cost optimization problems. The methods developed have been illustrated using some numerical examples, and sensitivity analyses carried out in the context of ramp-stress ALTSP based on variable SSP for proportion nonconforming.

• 디지털융복합연구
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• 제11권12호
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• pp.193-199
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• 2013

오늘날 학생들은 미래 사회인으로써의 준비를 위해 개인역량 개발, 학업성적, 대인관계, 취업준비, 영어공부 등으로 스트레스를 받고 있다. 학생들의 스트레스는 마음의 안정을 저해하고, 삶의 만족감을 악화시킨다. 본 연구에서는 대학생들이 느끼는 스트레스가 마음챙김과 삶의 만족감에 미치는 영향 관계를 구조방정식모델을 통해 살펴보았다. 더불어, 학생들의 학년에 따른 스트레스 수준이 삶의 만족감에 미치는 영향을 분석하였다. 본 연구결과는 학생들의 삶의 만족감을 높이기 위한 스트레스 관리와 마음챙김에 도움을 제공해 줄 것이다.

• 보건의료산업학회지
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• 제6권4호
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• pp.177-189
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• 2012

This study was done to identify campus life stress, self-esteem and health promotion behavior of university students and to provide basic data for the qualitative improvement of health promoting behavior of young adult. The data were obtained from distributing structured questionnaires to 491 university students in Busan. It was collected from July. 2th to the Agu. 2th of 2012, and analyzed by t-test, ANOVA, Pearson's correlation coefficient and Multiple stepwise regression. The correlation between health promotion behavior and self esteem showed to be positivity correlated(r=.180, p<.001). Also the correlation between health promotion behavior and campus life stress showed to be negativity correlated(r=-.231, p<.001). Life stress(Challenges stress) and Self-esteem were significant predictor and accounted for 13.4% of the variance in health promotion behavior of university students. Therefore it is important to develop programs that increase their self-esteem and is required to prepare a program for the development of health promoting behaviors early adult.

• 동의신경정신과학회지
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• 제11권1호
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• pp.47-57
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• 2000

This study was designed and performed to identify the effects of oriental medical therapy on hwabyung patients by investigating the life events as the cause of Hwabyung, recent stress perception which influences the clinical appearances and change of symptoms by means of objective scales. 1. Through life events rating scale, life events are reported as follows, in the order of majority. Health, discord within family, martial life, friendship and interest, religion etc. Hwabyung patients experienced negative stress much more than positive stress. 2. Through the GARS (Global Assessment of Recent Stress), there were some significant decreases of stress perception in stress4(stress of sickness or injury), stress7(stress of change or no change in routine) and stress8(overall global stress)(p<0.05, respectively), but there were no significant decreases in five items out of eight items. 3. There were significant decreases of all rated symptoms(feeling of chest oppressed, stuffy in the chest or epigastric mass, feeling of something pushing-up, flushing of body or face, abrupt impulsion of anger, resentment), which were checked weekly for 4 times (p<0.05, respectively). In this study the symptoms of hwabyung were improved regardless of stress perception. It means that hwabyung can be improved significantly with oriental medical therapy.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 2001년도 춘계학술대회논문집:21세기 신지식정보의 창출
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• pp.129-133
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• 2001

Accelerated life test is a viable method for identifying failure modes, incorporating design changes on an on-going basis during the early stages of automotive development program. The information from tests at high stress levels is extrapolated to obtain estimate of life at normal stress levels. This paper presents a practical method for accelerated life test to achieve a specified accuracy in estimating life at a design stress. Recommended and optimum plan are presented and the plans are illustrated with a simulated test data for the automotive power element example.

• Food Science and Biotechnology
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• 제16권6호
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• pp.1035-1040
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• 2007

Epidemiologic studies have shown important relationships between oxidative stress and Alzheimer's disease (AD) brain. In this study, free radical scavenging activity and neuronal cell protection effect of aqueous methanol extracts of Acanthopanax senticosus (A. senticosus) were examined. $H_2O_2$-induced oxidative stress was measured using 2',7'-dichlorofluorescein diacetate (DCF-DA) assay. Pretreatment with the phenolics of A. senticosus prevented oxidative injury against $H_2O_2$ toxicity. Since oxidative stress is known to increase neuronal cell membrane breakdown, leading to cell death, lactic dehydrogenase release, and trypan blue exclusion assays were utilized. We found that phenolics of A. senticosus have neuronal cell protection effects. It suggests that the phenolics of A. senticosus inhibited $H_2O_2$-induced oxidative stress and A. senticosus may be beneficial against the oxidative stress-induced risk in AD.

• Child Health Nursing Research
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• 제12권3호
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• pp.368-376
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• 2006

Purpose: The purpose of this research was to examine the degree of care stress and the quality of life of grandmothers caring for their grandchildren while mother was employed. Method: A convenience sample of 107 grandmothers were measured for grandmother's care stress using a revised for of the PSI/SF and the quality of life tool by Andrew and Weinert. Descriptive statistics, t-test, and Pearson correlation coeffcients were used to analyze the data using SPSS/PC 10.0 Results: The results found that grandmothers' care stress was high according to their age and religion. Their quality of life was low according to their age, their present health status, income and sleep pattern. Their subjective care stress was a sense of social isolation, burden of caring for grandchildren, health problems, and conflict with adult children. Care stress and quality of life were found to be negatively correlated. This result was statistically significant. Conclusion: In conclusion, it was found that the care stress was high and affected quality of life. From this study it is proposed that there is a need to develop programs which consider grandmother' techniques in child care and health care to improve their quality of life. Ultimately, a good care environment for children will be good for the children's growth and development.

• 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.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.490-496
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• 2017

본 연구의 목적은 성격5요인과 스트레스 대처방식과의 관계에서 자기효능감의 매개효과를 검증하는 것이다. 이를 위하여 설정된 연구문제는 다음과 같다. 첫째, 성격 5요인과 스트레스 대처방식, 자기효능감의 관계는 어떠한지 분석하였다. 둘째, 성격 5요인 가운데 그 자체가 대학생의 정신건강을 의미하는 변인으로, 임상적 의미가 매우 높은 신경증과 성실성을 선정하여 신경증 및 성실성과 스트레스 대처방식과의 관계에서 자기효능감이 매개역할을 하는지 알아보았다. 이러한 연구문제를 검증하기 위하여 충청지역 D대학 1학년 462명을 대상으로 성격 5요인 척도, 스트레스 대처방식 척도, 자기효능감 척도를 실시하였다. 첫째, 상관 분석 결과 신경증과 자기효능감은 부적 상관을 나타내고, 성실성은 정적 상관을 나타냈다. 그리고 성격5요인과 스트레스 대처방식을 살펴보면 성실성은 스트레스 대처방식 가운데 회피중심과 부적상관을 보였고, 신경증은 스트레스 대처방식 중 사회적지지, 문제해결중심과 부적상관을 보였다. 둘째, 위계적 회귀분석을 사용해 자기효능감의 매개효과를 분석한 결과 자기효능감은 신경증 요인과 회피중심 간에 관계에서만 부분 매개효과가 있음을 나타냈다. 이러한 결과는 대학생의 스트레스 대처를 예측하기 위해 성격5요인이 유용한 심리적 구인이라는 점과 특히 대학생의 정신건강의 예언변수인 신경증 요인과 스트레스 대처방식 가운데 회피성향을 갖고 있는 경우 정신적 스트레스를 줄이기 위해 자기효능감에 대한 교육적 중재의 필요성을 밝혔다는 점에서 의의가 있다.