• 품질경영학회지
• /
• 제25권1호
• /
• pp.80-99
• /
• 1997

This paper considers designing the simple (2-level) constant-and step-stress ALTs minimizing the asymptotic variance of the maximum likelihood estimator of the accelaeration factor, which is defined as the ratio of the 100qth percentile at use stress to that a specified stress, for items having lognormally-distributed lives. It is assumed that (i) the log-linear relationship exists between the stress and the mean log life, (ii) the standard deviation of the log life is constant, and (iii) the cumulative exposure model holds for the effect of changing stress. For the constant-stress ALT the low stress and the sample proportion allocated to low stress are determined and for two modes of stress loading of step-stress ALTs, the low-to-high and high-to-low, the low stress and the stress change time are determined. For selected values of the design parameters the optimum plans are figured, two modes of step-stress ALTs and the constant-stress ALT are compared to each other, and the effects of the incorrect pre-estimates of the design parameters are investigated.

• Geomechanics and Engineering
• /
• 제16권2호
• /
• pp.113-124
• /
• 2018

Under repeated loading, the residual stresses within the subgrade and subsoil can accelerate the deformation of the road structures. In this paper, a series of laboratory cyclic loading model tests and small-scale model tests were conducted to investigate the dynamic stress response within soils under different loading conditions. The experimental results showed that a dynamic stress accumulation effect occurred if the soil showed cumulative deformation: (1) the residual stress increased and accumulated with an increasing number of loading cycles, and (2) the residual stress was superimposed on the stress response of the subsequent loading cycles, inducing a greater peak stress response. There are two conditions that must be met for the dynamic stress accumulation effect to occur. A threshold state exists only if the external load exceeds the cyclic threshold stress. Then, the stress accumulation effect occurs. A higher loading frequency results in a higher rate of increase for the residual stress. In addition to the superposition of the increasing residual stress, soil densification might contribute to the increasing peak stress during cyclic loading. An increase in soil stiffness and a decrease in dissipative energy induce a greater stress transmission within the material.

• 한국지역사회생활과학회지
• /
• 제21권3호
• /
• pp.341-350
• /
• 2010

The purpose of this study was to identify the level of care givers' job stress, burn-out and stress coping strategies and to determine the mediator effect of coping strategies in the relationship between job stress and burnout. The research subjects were 193 care givers for the elderly in Jeollanamdo. The data analysis was performed by using SPSS Win 17.0. The results of this study were as follows; The level of care givers' job stress which they perceived was 2.68 points in a scale of 5 points, stress coping strategies was 2.39 points in a scale of 4 points, and the degree of burnout was 2.27 points in a scale of 5 points. There was a positive correlation between the care givers' job stress and burnout. There was a negative correlation between the job stress and stress coping strategies. There was a positive correlation between the stress coping strategies and burnout. And the stress coping strategies showed mediating effects between the care givers' job stress and burnout. Accordingly, we found that stress coping strategies had an mediating effect on care givers' burnout and various coping strategies were related to the burnout.

• 한국지반공학회논문집
• /
• 제16권6호
• /
• pp.35-41
• /
• 2000

Residual stress is defined as a minimum stress with a large displacement of specimens and the residual stress after peak shear stress appears with displacement volume but there is no provision to select the residual stress. In the previous study, residual stress was recorded when the change of shear load is small in the condition of the strain more than 15%. But, in this study, hyperbolic function((No Abstract.see full/text), b=experimental constant) of soil test is adapted to joint of rock and the propriety is investigated. In a landslide and landsliding of artificial slope, wedge failure of tunnel with a large displacement, tests are simulated from peak stress to residual stress for safety analysis. But now. direct shear stress and triaxial compressive tests are usually performed to find out characteristics of shear stress about joint. Although these tests get a small displacement, that data of peak stress and residual stress are used for safety analysis. In this study, we tried to determine failure criteria for joints of rock using ring shear test machine. The residual stress following shear behavior was determined by the result of ring shear test and direct shear test. In conclusion, after comparing the results of the two test, we found that cohesion(c) and internal friction angle(ø) of ring shear test are 30% and 22% respectively of those of the direct shear test.

• 대한가정학회지
• /
• 제40권7호
• /
• pp.25-40
• /
• 2002

The purpose of this study was to examine the relationships between child's emotional intelligence and stress according to child's sex. The subjects for this study were 380 children of 5-6th grade selected from elementary schools in Busan. Kwak's questionnaires(1994) on child's emotional intelligence and Han, Mi-Hyun's questionnaires(1996) on child's stress were used. Statistical techniques such as Manoya, Pearson's correlation, canonical were used. The results were as follows : (1) According to sex, there were significant differences in child's emotional intelligence and stress. The girls showed higher emotional expression, emotional empathy, emotional control, and the friend-related stress than boys. The boys showed higher parent-related stress than girls. (2) There were significant negative correlations between child's emotional intelligence and stress. The children who got higher emotion intelligence perceived lower stress. (3) Among five dimensions of emotional intelligence for boy, the effective variable was emotional utilization. And among six dimensions of stress, the effective variables were home-environment stress and school-related stress. Among fine dimensions of emotional intelligence for girl, the effective variables were emotional expression and emotional recognition. And among six dimensions of stress, the effective variables were friend-related stress and parent-related stress.

• 품질경영학회지
• /
• 제25권2호
• /
• pp.1-14
• /
• 1997

This paper considers maximum likelihood (ML) estimation of lifetime distribution under stress bounded ramp tests in which the stress is increased linearly from used condition stress to the stress u, pp.r bound. The following assumptions are used: exponential lifetime distribution under a constant stress, an inverse power law relationship between stress and mean of exponential lifetime distribution, and a cumulative exposure model for the effect of changing stress. Likelihood equations for the parameters involved in the model and asymptotic distribution of the estimators are obtained, and a numerical example is given.

• 터널과지하공간
• /
• 제23권6호
• /
• pp.457-469
• /
• 2013

국내 100여개 지역에서 측정된 460개 현지응력자료를 종합 분석하여 국내의 광역적 현지응력 분포 패턴을 분석하고, 심도-응력 및 심도-측압계수 관계식을 제시하였다. 이와 함께 한반도의 지질시대별 고응력장 변화와 최근의 지진 메카니즘에 의한 응력장 추정 결과를 통합하여, 한반도지역의 응력장 분포 패턴인 한국응력지도(Korea Stress Map)를 작성하였다. 세계의 심도-응력 관계식들과 비교를 통해, 본 연구에서 도출된 관계식의 적합성과 수 km 심도에의 유추 적용성을 확인하였다. 그리고 세계응력지도(World Stress Map)과 함께 동북아시아지역의 응력장 패턴을 분석하였다.

• 한국콘텐츠학회논문지
• /
• 제9권9호
• /
• pp.359-369
• /
• 2009

본 연구는 호텔인턴쉽 참가자의 스트레스요인과 인턴쉽 만족, 사회적(학교)지원의 중요성을 논하기 위해 일본호텔에서 인턴쉽으로 참가하고 있는 대학생을 대상으로 분석을 하였다. 그 결과, 인턴쉽 스트레스는 인구통계학적인 특성에 따라 스트레스를 받는 집단이 상이하였고, 인턴쉽 만족은 인턴부서에 따라 만족도가 상이하게 나타남을 알 수 있었다. 또한, 인턴쉽 스트레스 요인은 인턴쉽 만족에 음(-)의 관련성을 나타내는 것으로 분석되었으며, 특히 '직무자체요인' 스트레스가 클 경우 직무만족이 상대적으로 크게 감소하는 것으로 나타나 '직무자체요인'의 스트레가 상대적으로 중요함을 알 수 있었다. 또한, 호텔인턴쉽 참가자에 대한 사회적(학교)지원이 높을수록 그리고 인턴쉽 스트레스가 낮을수록 인턴쉽 만족이 높게 나타나 인턴쉽 만족도를 향상시키기 위해서는 사회적 지원을 증가시키고 인턴쉽 스트레스를 감소시켜야 함을 알 수 있다.

• 동력기계공학회지
• /
• 제12권2호
• /
• pp.41-47
• /
• 2008

This article deals with the stress analysis of the friction drive, which transmits the power via the rolling resistance on the contract area between the two rotating bodies. On the contact area, friction drives are normally involved with shear stress due to the transmitted force, as well as normal stress. Thus the stress analysis including the shear stress is necessary for the design of the friction drive. Hertzian results can be used to estimate the normal stress distribution and elastic deflection of the contact area, although the shear stress distribution is not well defined. In order to investigate the shear stress distribution and its effects in a friction drive, we have performed the stress analysis of the spherical continuously variable transmission(CVT) using finite element method. The spherical CVT is one of friction drives, which is used in small power applications. The numerical results show that the normal stress distribution is not affected by the transmitted shear force, and the maximal shear stress is increased in small amount along with the shear force.

• Animal cells and systems
• /
• 제14권1호
• /
• pp.17-23
• /
• 2010

We isolated warm temperature acclimation-related protein 65-kDa (Wap65) cDNA from the liver of olive flounder and investigated the mRNA expression of Wap65 and HSP70 in olive flounder exposed to osmotic (17.5, 8.75, and 4 psu) and thermal stress (25 and $30^{\circ}C$). The mRNA expression of Wap65 and HSP70 was increased by thermal stress. The mRNA expression of HSP70 was also increased by osmotic stress, whereas no significant change in Wap65 expression was detected. These results indicate that Wap65 mRNA expression occurs specifically in response to increases in water temperature, but not in response to osmotic stress. Plasma cortisol levels were also increased by osmotic and thermal stress. We also utilized the stress hormone cortisol to examine whether Wap65 expression is thermal-stress-specific. Cortisol treatment increased HSP70 mRNA expression in vitro, but had no significant effect on Wap65 mRNA expression. Thus, thermal stress, but not osmotic stress, induces Wap65 expression.