• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2513-2519
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• 2000

Free vibration characteristics of an initially stressed CD/DVD disk, which is designed for increasing critical speeds of current optical disks, are analyzed using the Rayleigh-Ritz technique based on variational formulations. Natural frequencies of the new disk depend on membrane stresses caused by disk rotation as well as residual stresses imposed during the cooling process of the injection molding. Critical speeds are calculated for the various initial patterns of radial and circumferential stresses. Initially imposed tensile stresses increase the natural frequencies of all the vibration modes except zero nodal diameter mode, whose natural frequency is independent of circumferential stress. A new disk with initial tensile stress of 0.5MPa is shown to have its critical speed about 30 % higher than the current optical disk.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.187-192
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• 2001

Cracks in mechanical joints is generally under mixed-mode and there is the critical inclined angle at which mode I stress intensity factor becomes maximum. In order to evaluate the fatigue life of cracks in mechanical joints, horizontal crack normal to the applied load and located on minimum cross section is major concern but critical inclined crack must also be considered. In this paper mixed-mode fatigue crack growth test is performed for horizontal crack and critical inclined crack in mechanical joints. Fatigue crack growth path is predicted by maximum tangential stress criterion using mode I and mode II stress intensity factors obtained from weight function method, and fatigue crack growth rates of horizontal and inclined crack are compared.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.605-612
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• 2009

The purpose of this article is to empirically suggest the necessity of reconsidering the new aptitude factors such as the ability to withstand work stress, to handle unusual events, and to work independently, in the respect that the environmental change in railway safety-critical worker's job should be flexibly reflected in the current aptitude management system. Besides, several ways of reducing the stress level for the railway safety-critical workers were suggested as well.

• Journal of the Korean Ceramic Society
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• v.30 no.3
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• pp.229-235
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• 1993

Thermal history and thermal stress of alumina specimen, which occured from thermal shock process, were calculated by finite difference method. Stress intensity factor and crack growth in cyclic thermal fatigue were calculated from single thermal shock temperature history and thermal stress. Cyclic thermal life were estimated by bending strength after cyclic thermal shock under critical thermal shock temperature. Calculated stress intensity factor was compared with real experimental thermal fatigue life of specimen. Fatigue life until critical stress intensity factor and real experimental result were comparable.

• Journal of Korean society of Dental Hygiene
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• v.17 no.1
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• pp.39-47
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• 2017

Objectives: Identifying influencing factors of stress in clinical practice of dental hygiene students through controlling the amount of stress in clinical practice. Methods: A self-reported questionnaire was filled out by 226 dental hygiene students in Daejeon, Cheongju and Jeolla province from March 2 to 30, 2016. The contents of the questionnaire included general characteristics (6 items), clinical practice characteristics (4 items), clinical practice stress (16 items), quality of life (24 items), health promotion behavior (20 items), OHIP (14 items), and critical thinking disposition (15 items). Data was analyzed using SPSS 19.0. for one way ANOVA, scheffe' posthoc test, Pearson correlation coefficients, and multiple regression analysis. Cronbach's alpha of clinical practice stress, quality of life, health promotion behavior, OHIP, and critical thinking disposition were 0.827, 0.913, 0.896, 0.921 and 0.778, respectively. Results: Clinical practice stress was 3.38 points, quality of life was 3.40 points, health promotion behavior was 3.21 points, OHIP was 4.21 points and critical thinking disposition was 3.17 points. Conclusions: Factors that had impact on clinical practice stress include sleeping state, satisfaction of clinical practice, practice number, and the quality of life, and they appeared statistically significant (p<0.05). This exercise showed the necessary manuals and system implementations in clinical practice, which can reduce the amount of stress in dental hygiene students.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1109-1117
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• 2015

The purpose of this study was to examine the job-seeking stress of nursing students according to their critical thinking disposition and self-esteem and the relationship of these variables. The subjects in this study were 332 nursing students. The students got $89.57{\pm}9.77$ in critical thinking; $25.11{\pm}2.58$ in self-esteem; and $46.38{\pm}17.67$ in job-seeking stress. There was a positive correlation between critical thinking and self-esteem(r=.294, p<.001), and critical thinking(r=-.240, p<.001) had a significant positive correlation with self-esteem(r=-.209, p<.001). Critical thinking disposition and self-esteem were identified as the variables to affect job-seeking stress, and the two variables had a 35.2% explainability.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.51-56
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• 2003

It is important to evaluate the fracture initiation behaviors of steel structure. It has been well known that the ductile cracking of steel would be accelerated by triaxial stress state. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameters, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of notch radius, which can elevate plastic constraint due to heterogeneous plastic straining on critical condition to initiate ductile crack using two-parameters. Hense, the crack initiation testing were conducted under static loading using round bar specimens with circumferential notch. To evaluate the stress/strain state in the specimens was used thermal elastic-plastic FE-analysis. The result showed that equivalent plastic strain to initiate ductile crack expressed as a function of stress triaxiality obtained from the homogeneous specimens with circumferential notched under static loading. And it was evaluated that by using this two-parameters criterion, the critical crack initiation of homogeneous specimens under static loading.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.141-144
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• 1984

The fatigue limits of crack initiation and propagation on the edge elliptical notched semi-infinite plate under completely reversed fatigue stress are determined theoretically. Assuming that the crack initiation and propagation occur when stress intensity factors of notched plate reach the critical values obtained from critical micro-crack length under plain fatigue limit loading and the threshold stress intensity factory, respectively, the fatigue limits of crack initiation and propagation are obtained. The induced theoretical fatigue limit of crack initiation is expressed in terms of plain fatigue limit, critical micro-crack length and notch shape. The one of crack propagation is in terms of threshold stress intensity factor, plain fatigue limit and notch shape. These theoretical results are showed to be in good agreement of Frost's experimental data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2344-2352
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• 2000

Mechanical joints such as bolted or riveted joints are widely used in mechanical components. The reliable determination of the stress intensity factors for cracks in bolted joints is needed to evaluate the safety and fatigue life of them. The weight function method is an efficient technique to calculate the stress intensity factors for various loading conditions because only the stress analysis of an uncracked model is required. In this paper the mixed-mode stress intensity factors for cracks in bolted joints are obtained by weight function method, in which the coefficients of weight function are determined by finite element analyses for reference loadings. Critical inclined angle that mode I stress intensity factor becomes maximum is determined and the effects of crack length and the magnitude of clearance on critical inclined angle are investigated.

• Journal of Digital Convergence
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• v.15 no.8
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• pp.213-224
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• 2017

This study was to examine the structural model of nursing student 's Professional self-concept, Critical thinking, Clinical Practice Satisfaction, Clinical competency and Clinical Practice Stress. The subjects consisted of 227 nursing students and data was collected through Structured questionnaires. Results, Critical thinking, Clinical Practice Satisfaction, Clinical competency and Clinical Practice Stress showed a direct effect on Professional self-concept for nursing students. Clinical competency and Clinical Practice Stress showed an indirect effect on nursing Professional self-concept. Clinical competency and Clinical Practice Stress showed a direct effect on Critical thinking and Clinical Practice Satisfaction. In this paper, we propose a new approach to nursing students 'self-concept in nursing. In this paper, we propose a new approach to nursing students' self-concept. And to develop and apply an intervention program that can reduce the stress of clinical practice.