• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.102-105
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• 2001

The spring back taking place after the coiling process of steam generator tube leads to the dimensional inaccuracy. In order to reduce the spring back, tension force was applied to the one end of the tube during forming. In this work, parametric study using FEM was performed to find the appropriate magnitude of tension force. The force that induces minimum suing back was found by simultaneously taking account of suing back amount, cross-sectional ovality, and thickness of the tube wall after deformation. In addition, stress relieving by heat treatment was also simulated as an alternative to the former method. The latter was found to be more effective under the given constraints.

• Transactions of Materials Processing
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• v.11 no.3
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• pp.238-245
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• 2002

The spring back taking place after the coiling process of steam generator tube leads to the dimensional inaccuracy. In order to reduce the spring back, tension force was applied to the one end of the tube during forming. In this work, parametric study using FEM was performed to find the appropriate magnitude of tension force. The force that induces minimum spring back was found by simultaneously taking account if spring back amount, cross-sectional ovality, and thickness of the tube wall after deformation. In addition, stress relieving by heat treatment was also simulated as an alternative to the former method. The latter was found to be more effective under the given constraints.

• Transactions of Materials Processing
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• v.21 no.5
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• pp.291-297
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• 2012

In this paper, the effect of back tension in multi-pass drawing or wiredrawing on the central bursting defect is investigated using finite element predictions. A rigid-plastic finite element method was used together with the McClintock damage model. Central bursting defects under different back tension stress values ranging from 0% to 20% of the yield strength of the material were predicted and they were compared to understand the effect of the back tension stress values on the central bursting defect. It is found that the level of back tension has a strong influence on the cumulative damage. Thus, higher back tension raises the possibility of the central bursting defect occurring, even though it decreases the interfacial pressure between the die and the work piece.

• The Korean Journal of Health Service Management
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• v.9 no.4
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• pp.79-90
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• 2015

Objectives : The aim of this study was to investigate the effect of musculoskeletal symptoms and job stress on the fatigability of 268 dental health care workers in Busan. Methods : A structured, self-administered questionnaire was given from Oct 1 through Oct 10, 2015. The collected data were analyzed with the SPSS 18.0 program. Results : The results were as follows. First, for musculoskeletal symptoms, job stress and fatigability, the highest scores were for low back pain (3.23), business stress (2.95) and physical fatigability (3.32), respectively. Second, physical fatigability increased with increasing myofascial pain syndrome, low back pain and business stress. Mental fatigability increased with increasing business stress, human relationships and social activities and decreasing age. Conclusions : Taking the above into consideration, this thesis suggests that there is definite influence from musculoskeletal symptoms and job stress factors on physical and mental fatigability.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.5
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• pp.82-88
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• 2011

In the present work, FEM analyses are carried out to investigate the fractures occurred within the structural part in the course of combustion experiment. The loss of structural integrity stems from the localized deformation and the damage induced due to a severe change in the thermal load. Moreover, the two-back stress evolution model is proposed using the Armstrong-Frederick and the Phillips' rules to depict the plastic deformation, and the continuum damage mechanics is also incorporated into the present model. It is noted that the present model is able to formulate a wide range of constitutive description with ease. The numerical results depicts that a severe strain localization and damage evolution can be obtained depending on the dominant back stress.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.272-278
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• 2011

In the present work, FEM analyses are carried out to investigate the fractures occurred within the structural part in the course of combustion experiment. The loss of structural integrity stems from the localized deformation and the damage induced due to a severe change in the thermal load. Moreover, the two-back stress evolution model is proposed using the Armstrong-Frederick and the Phillips' rules to depict the plastic deformation, and the continuum damage mechanics is also incorporated into the present model. It is noted that the present model is able to formulate a wide range of constitutive description with ease. The numerical results depicts that a severe strain localization and damage evolution can be obtained depending on the dominant back stress.

• Korean Journal of Psychosomatic Medicine
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• v.10 no.1
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• pp.18-26
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• 2002

Objectives : The object of this study was to investigate the relationship between coping strategies and perceived stress or pain discomfort in patients with chronic low back pain. 80 patients with chronic low back pain and 100 normal controls participated in this study. Methods: Global assessment of recent stress (GARS) scale and Stress Response Inventory (SRI) were used to measure perception for stressors and stress responses. Coping scale and pain discomfort scale were used to measure coping strategies and pain perception. Results : Scores of perceived stress related to work or job, interpersonal relationship, changes in relationship, sickness or illness and the total scores on the GARS scale were significantly higher in those with chronic low back pain than normal controls. Scores of the SRI fatigue subscale scored significantly higher in those with chronic low back pain than normal controls. No significant difference was found on total scores of the pain discomfort scale between those with chronic low back pain and normal controls. The patients with chronic low back pain scored significantly higher on planful problem solving and positive reappraisal than normal controls. In the patient group, pain perception had significant positive correlations with total scores of the SRI and scores of stress perception related to illness or injury. The extent of escape-avoidance showed significant negative correlations with age, whereas the extent of distancing or escape-avoidance had significant negative correlations with the level of education. Significant difference was also found in accepting responsibilities between male subjects and females. However, no significant correlations were found between coping strategies and perceived stressors, stress responses or pain perception. Conclusion : The results suggest that patients with chronic low back pain were more likely to use more active coping strategies than normal controls, though the former had more perception for stressors than the latter. It was also found that coping strategies used by the patients were associated with sociodemographic factors, but that they were not associated with perceived stressors, stress responses or pain perception.

• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.193-198
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• 2001

유한요소법을 이용하여 STS VOD 래들에서 내장 내화물의 재질 및 back filler의 시공 위치에 따른 열응력을 수행하였다. 불소성 내화물의 경우 높은 열전도율에 의해 가동면과 배면(back face)간의 온도구배가 소성품에 비해 감소하였으며 탄성계수도 낮아 발생되는 열응력이 2~4배 낮았다. Back filler는 dolomite 내화물의 열간 팽창을 흡수하기 위해 시공하는 것으로, 상대적으로 낮은 열전도율을 가지고 있기 때문에 back filler의 내부와 외부에 급격한 온도구배가 발생된다. 결과적으로 래들의 내부는 고온을 유지하여 내화물이 팽창이 되고, 외부는 온도가 낮아지므로 수축되어 열응력이 증가하였다.

• Journal of muscle and joint health
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• v.21 no.3
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• pp.165-172
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• 2014

Purpose: The purpose of this study was to identify effects of postural habits and stress on low back pain experienced by nursing students. Methods: The survey was conducted with 282 students at 5 nursing schools in Seoul, Incheon, Chungcheongbuk, and Jeollabuk Province. Data were collected from October, 2013 to January, 2014. Data analyses including descriptive analysis, ANOVA, Pearson's correlation coefficient, Spearman's rank correlation coefficients, and multiple regression were performed using SPSS 21.0. Results: In multiple regression, habit of standing on force of one feet (${\beta}=.23$, p<.001), habit of sleeping on one's back (${\beta}=-.19$, p=.020), habit of resting the chin on one's hands (${\beta}=.15$, p=.029), and habit of carrying a bag on one shoulder (${\beta}=.12$, p=.011) were associated with low back pain experienced by nursing students. These factors accounted for 12.9% of the variance in the low back pain in undergraduate students. Conclusion: These results suggest that low back pain in nursing students are related to their habits of posture in daily life. Therefore, intervention program to encourage healthy postural habits can be effective to prevent low back pain in nursing students.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.63-69
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• 2010

A noble model of the whole lumbar spine (L1~L5) considering all the passive elements, especially the ligaments of the lumbar spine was developed. The purpose of this study was to investigate the relationship between the shear stress of the AVB and the ALL and the effect of a compressive follower pre-load on all ligaments with various motions. The result shows that the shear stress at the AVB and the ALL are positively correlated. This indicates that the shear stress of the ligament can be used an index of low back pain. Regarding the effect of a follower pre-load, contrary to our expectation, the shear stress of the ligaments was not always reduced by applying follower pre-load; flexion was decreased and axial rotation did not change, while extension and lateral bending were increased.