• Journal of the Korean Data and Information Science Society
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• 제17권3호
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• pp.945-952
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• 2006

Several accelerated life test plans use tests at only two levels of stress and thus, have practical limitations. They highly depend upon the assumption of a linear relationship between stress and time-to-failure and use only two extreme stresses that can cause irrelevant failure modes. Thus 3-level stress plans are preferable. When the lifetime distribution of test unit is exponential with mean lifetime $\theta_i$ at stress $x_i$, i=0, 1, 2, 3, we derive the optimum quadratic plan under the assumption that a quadratic relationship exists between stress and log(mean lifetime), and propose the compound linear plans, as an alternative to the optimum quadratic plan. The proposed compound linear plan is better than two other compromise plans for constant stress testing and nearly as good as the optimum quadratic plan, and has the advantage of simplicity.

• Advances in nano research
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• 제15권6호
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• pp.567-577
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• 2023

The killing of bacteria by mechanical forces on nanopatterned surfaces has been defined as a mechano-bactericidal effect. Inspired by nature, this method is a new-generation technology that does not cause toxic effects and antibiotic resistance. This study aimed to simulate the mechano-bactericidal effect of nanopatterned surfaces' geometric parameters and material properties against three implant-derived bacterial species. Here, in silico models were developed to explain the interactions between the bacterial cell and the nanopatterned surface. Numerical solutions were performed based on the finite element method. Elastic and creep deformation models of bacterial cells were created. Maximum deformation, maximum stress, maximum strain, as well as mortality of the cells were calculated. The results showed that increasing the peak sharpness and decreasing the width of the nanopatterns increased the maximum deformation, stress, and strain in the walls of the three bacterial cells. The increase in spacing between nanopatterns increased the maximum deformation, stress, and strain in E. coli and P. aeruginosa cell walls it decreased in S. aureus. The decrease in width with the increase in sharpness and spacing increased the mortality of E. coli and P. aeruginosa cells, the same values did not cause mortality in S. aureus cells. In addition, it was determined that using different materials for nanopatterns did not cause a significant change in stress, strain, and deformation. This study will accelerate and promote the production of more efficient mechano-bactericidal implant surfaces by modeling the geometric structures and material properties of nanopatterned surfaces together.

• 동력기계공학회지
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• 제13권6호
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• pp.95-101
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• 2009

The generator for gas turbine power generation consists of the rotor which generates magnetic field, the winding coil which is the path for the field current and the wedge and retaining ring which prevents the radial movement of the coil. Relatively severe deformation was observed at the coil end section during the inspection of the generator for peaking-load operation, and the thermal-electricity and the centrifugal force were evaluated by the simple modeling of the windings to find the cause. But the simulation stress was not sufficient to induce the coil plastic deformation. The analysis result seems to be applicable to the base-load generators which runs continuously without shut down up to a year, but there had been more deformation than simulated for the generator which is started up and shut down frequently. The cause of the coil deformation was the restriction of the expansion and shrinkage. The restriction occurs when the winding coil shrinks, and the stress overwhelms the yield stress and cause the plastic deformation. The deformation is accumulated during the start-ups and shut-downs and the thermal growth occurs. The factors which induce the coil restriction during the expansion and shrinkage should be reduced to prevent the unallowable deformation. The resolutions are cutting off the field current earlier during the generator shut-down, modifying the coil end section to remove the stress concentration and making the insulation plate inserted between the coil end section and the retaining ring have the constant thickness.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.715-722
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• 2001

The main purpose of this study is to evaluate early age thermal stresses and to estimate the risk of thermal cracking in the footings of Hyungsan bridge. In this study, stress analyses are performed for several construction stages using the computation of temperature distributions. The stress analysis results show that, not using the embedded pipe cooling, placing the concrete at once for each footings may cause sever thermal cracking. So, the structures should be constructed with one horizontal construction joint. Then the height of each lifts were determined to be 1.50 meters. Using various time intervals between lifts, temperature and stress.

• 시큐리티연구
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• 제41호
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• pp.241-261
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• 2014

이 연구는 전의경의 부대적응의 원인을 밝히는 데 있어 전의경 부대의 구타근절대책이 스트레스 변인을 통해 부대적응에 이르는지를 구조방정식분석을 사용하여 파악하는 데 그 주된 목적을 두었다. 연구에 사용된 자료는 2011년 울산지방경찰청 소속 전의경 전원에 대한 조사 데이터이다. 구조방정식 분석결과, 스트레스를 통한 매개효과는 p<.001 수준에서 통계적으로 유의미한 것으로 나타났다. 또한 표준화 회귀계수를 통해 효과크기를 확인한 결과, 스트레스가 부대적응에 미치는 영향력이 부대의 구타근절대책의 영향력 보다 더 더 컸다. 즉, 부대의 구타근절대책이 전의경의 부대적응에 긍정적인 영향을 주지만, 전의경의 부대적응력은 부대의 구타근절대책 보다 개인이 느끼는 스트레스 요인이 더 커다는 것을 알 수 있다. 이를 통해 경찰당국은 전의경이 겪는 스트레스가 부대적응도를 결정할 수 있는 원인임을 인지하고, 이에 대한 대안을 마련하여야 한다.

• 한국생활과학회지
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• 제16권4호
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• pp.711-722
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• 2007

The purpose of this study was to analyzed child care teachers' health state and a relationship between health promoting lifestyle and job stress of child care teachers. The subjects were 101 child care teachers in Busan. They responded to 'health state open ended question', 'health promoting lifestyle scale', and 'job stress scale'. For the analysis of the data, M(SD), frequencies, t-test, Pearson's correlation were run by using SPSS WIN computer program. The major findings of this study were as follows; First, the most uncomfortable symptoms of child care teacher's physical health state was respiratory organs and the main cause was classroom ventilation and dust. The most uncomfortable symptoms of child care teacher's mental health state was tension and the main cause was children's safety. Second, the mean scores of the variables were as follows : the mean score of health promoting lifestyle was 2.54. The highest sub factor of health promoting lifestyle was 'positive self recognition' and the lowest one was 'exercising'. The mean score of job stress was 2.80 and the highest sub factor was 'administration services'. They desire for a healthy life, but in reality, they are unsatisfied with their current health state and they are not able to practice certain actions actively to promote their health. Third, health promoting lifestyle was negatively correlated with job stress. The result of this study can be used as the basic data for reducing day care teacher's job stress, development of a program to promote day care teacher's health and improving day care teachers working environment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.191-194
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• 2006

Recently the quality improvement of the steel cord product is demanded by the tire market. After wire drawing process, produced residual stresses have a harmful effect on the durability of the wire and become the cause which decreases the quality of the product. Therefore, to improve the quality of the steel cord product, the research regarding the method of residual stress relaxation is necessary. To evaluate the quality of the drawn wire, it is important to measure the residual stress, because the residual stress decides a variety of the quality level which is demanded in the drawn wire. This study proposed a residual stress relaxation method in the drawn wire using FE analysis. The validity of the analysis results was verified by nanoindentation test.

• 한국조리학회지
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• 제11권4호
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• pp.150-163
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• 2005

If a licensed cook of a special-deluxe hotel restaurant and n family restaurant receives stress psychologically and physically, it will influence the interaction with customers who eat their food. Job stress is known to affect the kitchen operation and cause negative formation of interior and exterior customer management. This study wishes to present the method that can minimize the negative effect caused by stress, leading to an elevation of service quality that is offered to customers by removing those factors related to the stress of a licensed cook. This study established the range of targets to compare the cooks of super-deluxe hotel restaurants and those of family restaurants and to apply result of this research to whole licensed cooks is considered to have some limitations. Therefore, estimating job stress and turnover intention of general licensed cooks through comparison with tourist hotels and general restaurants should be significant hereafter.

• 한국해양공학회지
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• 제9권1호
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• pp.83-91
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• 1995

Surface defects in structural members are apt to be origins of fatigue cracks growth, which may cause serious failure of whole structures. Most structure has a part where stress concentrates such as welded joints, corner parts, etc. And then, analysis on crack growth and penetration from these defects, therefore, is one of the most important subjects for the reliability of LBB design. The present paper has performed an experimental and analysis on the fatigue crack propagation by variety in crack length of surface cracked plate with stress concentration part. The crack growth behavior can be explained quantitatively by using Newman-Raju equation and the stress partitioning method proposed by ASME B&P Code Sec. XI. The stress concentration factor $K_t$ has affected on the crack growth. The crack growth after penetration depends upon the initial front side crack length.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.195-198
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• 2002

Residual stress of sheet occurs during cold rolling and it is hard to avoid and inevitable. The residual stress in the sheet cause etching curls when it suffers peroration process. The residual stress through the thickness direction in the sheet is a function of a friction coefficient, total reduction, mil size and initial sheet thickness. To estimate the residual stress and deformation due to etching curl, FEM analysis is performed. A numerical analysis is used a ANSYS 5.6 and an elastic-plastic constitutive equations. rho simulation results indicate a distribution of residual stress.