• 대한예방한의학회지
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• 제14권3호
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• pp.51-61
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• 2010

This study aimed to evaluate musculoskeletal workload associated with the work of hair designers, to identify the factors associated with work-related stress, depression and musculoskeletal symptoms in Hair Designers, and to check the painful areas based on patients who complained of musculoskeletal symptoms. The data were collected from 279 hair designers in Daegu metropolitan city from February 1 to August 31 of 2009. A summary of the results was as follows : According to work-related stress in study subjects, the degree of stress load was relatively higher in association with the working demand, the relational conflicts and the organizational culture, but the degree of stress was found to be relatively lower in association with the physical environment, work-related autonomy, an insufficient compensation and an occupational instability. People engaged for beauty business have gotten lots of stress because of the endless needs from customers, the pressure of the learning new skills and the uncomfortable working environment. These are able to cause the musculoskeletal disorder. Under this circumstance, small fries do not have any prevention managements for improving the musculoskeletal diseases and they are not afforded to have regular checkup. When teaching the people related with beauty business, it is necessary to provide accurate information like correct carriage to reduce musculoskeletal disorder stress.

• 대한기계학회논문집A
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• 제29권10호
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• pp.1384-1391
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• 2005

Damage often occurs on the surface of railway wheels due to wheel-rail contact fatigue. It should be removed before reaching wheel failure, because wheel failure can cause derailment with loss of life and property. The increase or decrease of the contact fatigue lift by the metal removal of the contact surface were investigated by many researchers, but they have not considered initial residual stress and traction force. The railway wheel has the initial residual stress formed during the manufacturing process, and the residual stress is changed by thermal stress induced by braking. The traction force and residual stress are operated on wheels of locomotive and electric motor vehicle. In this study, the effect of metal removal depth on the contact fatigue life for a railway wheel has been evaluated by applying lolling contact fatigue test. The effect of the traction force and metal removal on the contact fatigue life has been estimated by finite element analysis. It has been found that the initial residual stress determines the amount of metal removal depth if the traction coefficient is less than 0.15. If the traction coefficient is greater than 0.2, however, the amount of metal removal depth is independent on the intial residual stress.

• 대한치과기공학회지
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• 제40권4호
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• pp.249-259
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• 2018

Purpose: This study aimed to investigate the relationship between dental technology students' life stress and smartphone addiction in order to detect smartphone over-users early, prevent them from getting addicted, and obtain basic data for creating a positive environment for academic achievement by using smartphone in a right way. Methods: The subjects of this study were university students at D University and G University in Daejeon Metropolitan City and Gangwon-do. A questionnaire survey was conducted to the subjects who understood the purpose of this study and participated in it from March 1 to June 10, 2018, and 243 were finally analyzed except 24 questionnaires without sufficient answers. Results: As a result of multiple regression analysis with variables, which were significant in univariate analysis, as independent variables, there were gender and smartphone dependency as general characteristics affecting the degree of smartphone addiction, and family relations and future problems among stress sub-factors were selected as significant variables. Conclusion : In the case of college students, they choose the smartphone as the easiest way to relieve stress because they lack the time and space to actually release stress. Therefore, club activities or on-campus and extra-curricular activities are recommended, and it needs to seek a way to get rid of stress by solving the cause of stress through counseling.

• 한국정밀공학회지
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• 제23권5호
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• pp.162-169
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• 2006

Steel cord which is used as reinforcement in car tires is produced by wet-drawing process. Recently the quality improvement of the steel cord product is demanded by the tire market. After cold 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 cold drawn wire, it is very important to measure the residual stress, because the residual stress decides a variety of the quality level which is demanded in the cold drawn wire. The aim of this study is to propose residual stress relaxation method in the drawn wire using FE-analysis. The validity of the analysis results was verified by Nano indentation test.

• 대한기계학회논문집A
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• 제29권2호
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• pp.341-349
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• 2005

Damage often occurs on the surface of railway wheel by wheel-rail contact fatigue. It should be removed before reaching wheel failure, because wheel failure can cause derailment with loss of life and property. The increase or decrease of the contact fatigue life by the metal removal of the contact surface were shown by many researchers, but it has not explained precisely why fatigue life increases or decreases. In this study, the effect of metal removal depth on the contact fatigue life for railway wheel has been evaluated by applying finite element analysis. It has been revealed that the residual stress and the plastic flow are the main factors determining the fatigue life. The railway wheel has the initial residual stress formed during the manufacturing process, and the residual stress is changed by thermal stress induced by braking. It has been found that the initial residual stress determines the amount of metal removal depth. Also, the effects of the initial residual stress and metal removal on the contact fatigue lift has been estimated, and an equation is proposed to decide the optimal metal removal depth for maximizing the contact fatigue life.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.248-261
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• 1999

The fatigue life of mechanical components and structures has been influenced by mechanical, material and environmental conditions. It is important to search out the load type and size for accurate cause of fracture at the damaged surface of material. The fractographic method by x-ray diffraction can utilize residual stress $\sigma$_r and half-value breadth B and find out the types and the mechanical conditions of fracture. This study showed the relationship between fracture mechanical parameters $\Delta$K, $K_{max}$ and X-ray residual stress $\sigma$_r for normalized SS41 steel with homogeneous crystal structure and M.E.F. dual phase steel(martensite encapsulated islands of ferrite). The fatigue crack propagation tests were carried out under stress ratios 0.1 and 0.5. The x-ray diffraction technique according to crack propatation direction was applied to fatigue fractured surface. Residual stress $\sigma$_r was independent on stress ratios by arrangement of $\Delta$K. The equation of $\sigma$_r$\Delta$K was established by the experimental data. Therefore, fracture mechanical parameters can be estimated can be estimated by the measurement of X-ray parameters.

• 한국정밀공학회지
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• 제24권3호
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• pp.84-90
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• 2007

As a result of vehicle maintenance of rocker arm shaft for 4-cylinder SOHC engine, failure stress analysis of rocker arm shaft is needed. Because more than 30% of vehicles investigated have been fractured. Failure stress analysis is classified into an naked eyes, microscope, striation and X-ray fractography etc. Failure stress analysis by using striation is already established technology as means for seeking cause of fracture. But, although it is well known that striation spacing corresponds to the crack growth rate da/dN, it is not possible to determine ${\sigma}_{max}\;and\;{\sigma}_{min}$ under service loading only from striation spacing. This is because the value of striation spacing is influenced not only by ${\Delta}K$ but also by the stress ratio R. In the present paper, we determine the stress ratio using orthogonal array and ANOVA, and propose a prediction method of failure stress which is combined with FEM and striation.

• 한국직업건강간호학회지
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• 제16권2호
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• pp.147-157
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• 2007

Purpose: The purpose of this study was to identify job stress, burnout experience and job satisfaction in nurses and to identify their relationships. Method: The data were collected from 280 nurses employed in one general hospital, using the structured questionnaire. The data analyzed using SPSS Win program for descriptive statistics, t-test, ANOVA, and Pearson correlation coefficient. Result: There were significant differences in job stress, burnout experience and job satisfaction by current working unit, working period, scheduled to work as a nurse, cause to satisfaction, periods in night shift, level of adaptation, and health status. There was a significant positive correlation between job stress and burnout experience, and a inverse correlation between job stress and job satisfaction. Conclusion: The study findings show that job stress, burnout experience, and job satisfaction of nurses are correlated each other. Therefore, it is need to maintain a proper level of nurses' job stress and burnout experience through various ways to improve the situation. As a result, job satisfaction will be promoted and human resources will be managed appropriately.

• 한국전산구조공학회논문집
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• 제22권6호
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• pp.557-564
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• 2009

용접과정 중 발생되는 인장잔류응력은 원전 배관 이종용접부의 PWSCC가 발생되는 원인 중 하나라고 알려져 있다. 일반적으로 보수용접은 용접과정 중 흔히 일어나는 현상이다. 보수용접은 강한 인장잔류응력을 유도하기 때문에 이종용접부의 PWSCC를 유도하기 쉽다. 본 논문에서는 강한 인장잔류응력이 발생되는 보수용접부에 대해 보수용접 깊이에 따라 동종용접과 예방용접 overlay로 인하여 인장잔류응력의 크기가 변화하는 것을 정량적으로 확인하였다.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.209-216
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• 2016

Holes of rivets, bolts and nuts may cause stress concentration on the plates used in aircraft, ship and other structures. Excessive stress concentration may lead to severe breakage of the plates. Thus, accurate analysis of the stress concentration at the design stage will be important. In this paper, accuracy of EDISON program in stress concentration analysis was examined. By changing hole size on a narrow plate, the change of the stress concentration factor(K) was investigated. Additionally, the same experiment was conducted about series of holes on plate to investigate the interaction between adjacent holes. Then, these numerical results were compared with the analytic prediction. EDISON program showed very high accuracy about stress concentration, since the numerical results was correlated well with the analytic prediction.