• Proceedings of the KSME Conference
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• 2001.06a
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• pp.603-608
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• 2001

Recently, cold expansion of fastener holes is commonly used in the aerospace industry to increase the fatigue endurance of airframes. Cold expansion process is used as the retardation of crack initiation in the hole. This treatment leads to an improvement of fatigue behavior due to the compressive residual stresses developed on the hole surface. The residual stress profile depends on the cold expansion ratio. In the present paper, it is shown that residual stress is redistributed due to the application of cold expansion process for CT specimen. It is further shown that residual stress increases in proportion to cold expansion ratio. It is thought that crack growth rate increases as cold expansion ratio.

• The Korean Journal of Health Service Management
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• v.10 no.4
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• pp.239-248
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• 2016

Objectives : The purpose of this study was to examine the mediation effects of self-efficacy on the relationship between life stress and depression in university students to provide a basis for planning nursing interventions to improve the mental health of university students. Methods : Data were collected from September 1 to September 30, 2015 by giving a questionnaire to 272 university students. The instruments for this study were life stress, self-efficacy, and depression. The data were analyzed with descriptive statistics, Pearson's correlation coefficients, and multiple linear regression with the SPSS/WIN 18.0 program. Results : There were significant correlations among life stress, self-efficacy, and depression. Additionally, self-efficacy had a mediating effect on the relationship between life stress and depression. Conclusions : Based on the findings of this study, health management programs focusing on stress management and self-efficacy improvement are highly recommended to promote good mental health in university students.

• Nuclear Engineering and Technology
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• v.30 no.3
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• pp.202-211
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• 1998

Interfacial stresses at two-material interfaces and initial displacement field over the entire domain are obtained by modifying the potential energy functional with a penalty function, which enforces continuity of the stresses at the interface of two materials. Based on the initial displacement field and interfacial stresses, a new methodology to generate a continuous stress field over the entire domain has been proposed by combining the modified projection method of stress-smoothing and Loubignac's iterative method of improving the displacement field. Stress analysis is carried out on two examples made of dissimilar materials : one is a two-material cantilever composed of highly dissimilar materials and the other is a zirconium-lined cladding tube made of slightly dissimilar materials. Results of the analysis show that the proposed method provides an improved continuous stress field over the entire domain, and accurately predicts the nodal stresses at the interface, while the conventional displacement-based finite element method produces significant stress discontinuities at the interface. In addition, the total strain energy evaluated from the improved continuous stress field converges to the exact value in a few iterations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.10
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• pp.568-572
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• 2013

The main components, such as a reactor vessel, in commercial nuclear power plants have been welded to pipes with dissimilar metal in which Primary Water Corrosion Cracking (PWSCC) has been occurred. PWSCC has become a worldwide issue recently. This paper addresses the results of experimental and numerical analysis to prevent PWSCC by changing the stress profile that is tensile stress to compressive stress at interesting regions with plastic deformation generated by mechanical pressure. Based on the results of experimental and numerical analysis with a 6 inch pipe and dissimilar metal welded pipes, compressive stress 68~206 Mpa is generated at all locations of inner surface in the heat affected zone.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.145-151
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• 2002

This paper is results of extensive centrifuge model experiments about design factors influencing the bearing capacity and the settlement behaviors of SCP (Sand Compaction Pile). Centrifuge model tests were carried out changing design factors for SCP method such as replacement area ratio (as= 20, 40, 70%), Improvement ratio to footing width (W/B = 1, 2, 3), and amount of fines m sand pile (#200 = 5, 10, 15). Therefore, the effects of these design factors on the bearing capacity and the settlement behavior of SCP were investigated and changes of stress concentratio rato due to such an design factors were also investigated. Centrifuge model testing technique for preparing and installing centrifuge model of sand compaction pile, using freezing them, was also developed. As results of centrifuge model tests, more fines in sand compaction pile increases the bearing capacity of SCP. Optimum improvement ratio to footing width was found to be 2. Values of stress concentration ratio was in the ranges of 1.5 - 3.5. The depth of bulging in sand plies was found in the range of 2.0 - 2.5 times of pile diameter.

• Journal of Oriental Neuropsychiatry
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• v.21 no.2
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• pp.17-28
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• 2010

Objectives : This study is to evaluate the quality of life and amount of stress after the treatment among the patients who visited hospital due to traffic accident. Methods : We evaluated 40 patients who have been treated by western medicine for 3 months but showed no improvements. We surveyed VNRS, SF-36 and IES-R-K scores before treatment began and treated patients twice a week for 4 weeks with acupuncture, chuna theraphy, herbal medicine. After 4 weeks of treatment, we surveyed VNRS, SF-36 and IES-R-K scores again and compared with the scores of before treatment. Results : VNRS score and SF-36 scale and IES-R-K scale showed significant improvement after the treatment, compared to the treatment before. Conclusions : The amount of pain and stress, physical condition, all showed improvement among the patients who came to Oriental medicine hospital due to traffic accident.

• Steel and Composite Structures
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• v.26 no.1
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• pp.103-113
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• 2018

To study the effects of corner braces on fatigue performance of the U-rib and roof weld in steel bridge decks, the fatigue experiment was carried out to compare characteristics of the crack shape with and without corner braces. The improvement of fatigue life and stress variation after setting corner braces were also analysed. Different parameters of corner brace sizes, arrangements, and detail types were considered in the FEM models to obtain stress distribution and variation at the weld. Furthermore, enhancement of the fatigue performance by corner braces was evaluated. The results demonstrated that the corner brace could improve the fatigue life of the U-rib and roof weld, which exerted even no influence on the crack shape. Moreover, stress of the roof weld was decreased and the crack position was transferred from the root weld to U-rib and corner brace weld. It was suggested no weld scallop should be drilled on the corner brace. A transverse rib with lower height which was set between U-ribs was favourable for improvement of fatigue performance.

• Journal of Korean Academy of Nursing
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• v.38 no.3
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• pp.420-427
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• 2008

Purpose: The purpose of this study was to evaluate the contribution of group therapy to the improvement of self-esteem, anger, stress coping and communication of those who were violent in to family. Methods: The research design was a one-group-pretest-posttest design in quasi-experimental research, and the period of this study was from March to October, 2005. Participants were 14 offenders who were ordered to be counseled according to 'the special exemption law for punishing domestic violence.' Group therapy was applied once a week for 8 weeks. Results were collected by using a questionnaire for self-esteem, anger, stress coping and communication. In the data analysis, Wilcoxon signed test with SPSS/WIN 12.0 program was used. Results: The scores of self-esteem and communication showed statistically significant improvement from pre to post therapy. However, the scores of anger and stress coping were not significantly changed from pre to post therapy. Conclusion: This group therapy was effective in improving the self-esteem and communication in offenders of family violence.

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.131-137
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• 2008

SCP(Sand Compaction Pile) method that forms a composite ground by driving compacted sand piles into the soft ground. This method is one of the soil improvement techniques for reinforcing and strengthening soft ground deposits. This thesis describes the investigation on the behavior of soft ground reinforced with SCP by low improvement ratio. Direct shear test and consolidation test carried out to verified behavior of composite ground reinforced with SCP. Test results were discussed with reference to the amount of consolidation settlement, variation of shear resistance with area replacement ratio and effect of the stress concentration. And, laboratory model loading test carried out to verified the effect of the location and failure mode of reinforced embankment. Residual shear strength varies with the area replacement and constrict load in the low replacement ratio. Calculated stress concentration ratio overestimate than proposed valve by experimental, theoretical and analytical method. As regards the location, improving right below of the top of the slope was more effective than below of the toe of the slope. This thesis carried out to obtain fundamental information of behavior of the composit ground. Hereafter, centrifuge test that reproduce stress state of the in-situ must be necessary through the further study about pile penetration, reinforce position and construct time.

• Journal of Oriental Neuropsychiatry
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• v.21 no.2
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• pp.45-60
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• 2010

Objectives : The aim of this study was to investigate the correlation between the effectiveness of Brief Qigong-based Stress Reduction Program(BQSRP) and personality. Methods : Twenty nine women and nine men from the community with symptoms of distress(mean age 39.4 years, SD=11.4) were randomized into a group receiving a 4-week intervention of BQSRP(n=19) or a waiting-list control group. All subjects completed the temperament and character inventory (TCI) before the intervention. Before and after the intervention period, questionnaires were completed on perceived stress scale(PSS), anxiety, and quality of life. Results : 1. Those who have higher temperament of harm avoidance or lower character of self-directedness showed higher PSS, Hwa-Byung character, Hwa-Byung symptom, STAI and lower WHOQOL-BREF scores. 2. In the BQSRP training group, a correlation analysis demonstrated an association between higher temperament of harm avoidance and greater improvement of perceived stress and an association between lower character of self-directedness and greater improvement of perceived stress. 3. Those who have high Hwa-Byung symptom scores prefer the breathing meditation and there were no differences in effects of BQSRP group by the preference Brief Qigong-based Meditation(BQM) component. Conclusions : These results suggest that a BQSRP training may be effective for those with higher harm avoidance trait and low self-directedness.