• Structural Engineering and Mechanics
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• 제59권5호
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• pp.841-852
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• 2016

The present paper is concerned with the investigation of propagation of thermoelastic media, the finite difference technique is used to obtain the solution for the uncoupled dynamic thermoelastic stress problem in a non-homogeneous orthrotropc thick cylindrical shell. In implementing the method, the linear dynamic thermoelasticity equations are used with the appropriate boundary and initial conditions. Thermal shock stress becomes of significant magnitude due to stress wave propagation which is initiated at the boundaries by sudden thermal loading. Numerical results have been given and illustrated graphically in each case considered. The presented results indicate that the effect of inhomogeneity is very pronounced.

• 한국생활과학회지
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• 제17권1호
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• pp.27-34
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• 2008

The purpose of this study is to study how college students cope with their stress and how the level of their self-differentiation affects degrees of stress and stress-coping strategies. The questionnaires were handed to 497 college students at Y university in Gyeongbuk Province and the data were analyzed in terms of Cronbach's ${\alpha}$-coefficient, frequency and percentage, t-test, and regression analysis by using the SPSS statistical package. The results of this study were as follows: 1. For stress level, degree of self-differentiation and stress coping strategies of the college students, the average scores were 3.56, 2.53 and 3.49, respectively in 5-point Likert Scale, indicating that the students possess the above-average score for the degree of self-differentiation and stress-coping strategies and the below-average score for stress levels. 2. From examination of difference verification of stress levels based on the degree of self-differentiation and effect of degree of self-differentiation on stress levels, it was found that the higher is the degree of self-differentiation the lower is the stress level. 3. From examination of difference verification of stress-coping strategies according to the degree of self-differentiation and effect of degree of self-differentiation levels on stress coping strategies, we found that the students of higher degree of self-differentiation exercise the more active stress coping strategies. These results show that the degree of students' self-differentiation is a significant variable that influences their stress levels and stress control methods. It is thought that students' self-differentiation functions to minimize their stress and to actively cope with their stressful situation and that a high degree of self-differentiation is a significant mediator variable that is beneficial to students' mental health. It follows from the above observations that while college students in this study seem to possess good degrees of self-differentiation and stress coping capabilities and low stress levels they need to seek for the ways to improve their degree of self-differentiation by seeing into themselves and relationships with others around them. Parents, schools and consultation agencies are required to take an active hand to educate and encourage them to cope with their stress positively.

• 인간식물환경학회지
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• 제23권2호
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• pp.201-210
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• 2020

The purpose of this study was to determine the effects of flower decorations on job stress and stress copying style of police officers. Flower decorations were done in the form of "one-table one-flower", in which flowers were placed on each desk in the office space. By analyzing color psychology, we first identified the symbolism of color, and selected the cut flowers in the same color. We selected six types of flowers in six colors: red, orange, yellow, green, blue and purple. Each Monday morning, the flower decorations were delivered to the police station. We selected 50 subjects who wanted to keep flowers on their desks every week as the experimental group and 44 subjects who only wanted to participated in the assessment as the control group. Before and after the program, we examined the mean difference between the control group and experimental group. After six sessions of the program, there was a significant difference in job stress (p < .001) and stress copying style (p = .049) of the experimental group compared to the control group. Therefore, this study proved that having flower decorations in an office space is effective for the psychological stability of police officers that are highly stressed, due to sensory stimulations from the colors and scents of flowers as well as mutual interaction as they take care of the flowers.

• 대한치과교정학회지
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• 제48권6호
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• pp.384-394
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• 2018

Objective: This study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on time-dependent viscoelastic properties. Methods: Orthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated. Results: The degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length. Conclusions: Although prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.

• 대한안전경영과학회지
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• 제15권3호
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• pp.83-91
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• 2013

The purpose of this study was to compare the exposure levels to emotional labor, occupational and socio-psychological stress, and fatigue for workers engaged in the fields of beauty business (make-up, skin, nail, and hair). For this purpose, a survey was carried out and a statistical analysis was performed for 813 persons As a result, emotional labor was found to be linked with 3 factors of emotional control, emotional dissonance, and positive emotional expression. The exposure level of emotional control was found to be high in the area of hair care and that of positive emotional expression was high in the area of nail care. Based on evaluation of Occupational Stress Scale(KOSS), the stress were found to be highest among workers engaged in the field of make-up and lowest among those in the field of nail. The exposure level of psychosocial stress was found to be the highest in the area of make-up and the lowest in the area of nail care. The exposure level of fatigue was found to be the highest in the area of make-up and the lowest in the area of nail care, showing a difference in the exposure level of stress by area of beauty business. The study confirmed that there is a difference in the exposure level related to emotional labor, job stress, psychosocial stress, and fatigue by area of beauty business.

• 대한치과보철학회지
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• 제30권4호
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• pp.582-610
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• 1992

The long-term success of any dental implant is dependent upon the optimization of stresses which occur during oral function and parafunction. Especially, it has been suggested that there is an unique set of problems associated with joining an osseointegrated implant and a natural tooth with a fixed partial denture. For this particular case, although many literatures suggest different ways to avoid high stress concentrations on the bone surrounding the implant under static and dynamic loading conditions, but few studies on the biomechanical efficacy of each assertion have been reported. The purpose of this investigation was to evaluate the efficacies of clinically suggested methods on stress distribution under static load and shock absorption under dynamic load, using two dimensional finite element method. In FEM models of osseointegrated implant-natural tooth supported fixed partial dentures, calculations were made on the stresses in surrounding bone and on the deflections of abutments and superstructure, first, to compare the difference in stress distribution effects under static load by the flexure of fastening screw or prosthesis, or intramobile connector, and second, to compare the difference in the shock absorption effects under dynamic load by intramobile connector or occlusal veneering with composite resin. The results of this analysis suggest that : 1. Under static load condition, using an implant design with fastenign screw connecting implant abutment and prosthesis or increasing the flexibility of fastening screw, or increasing the flexibility of prosthesis led to the .increase in height of peak stresses in cortical bone surrounding the implant, and has little effect on stress change in bone around the natural tooth. 2. Under static load condition, intramobile connector caused the substantial decrease in stress concentration in cortical bone surrounding the implant and the slight increase in stress in bone around the natural tooth. 3. Under dynamic load condition, both intramobile connector and composite resin veneering showed shock absorption effect on bone surrounding the implant and composite resin veneering had a greater shock absorption effect than intramobile connector.

• 성인간호학회지
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• 제19권3호
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• pp.353-364
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• 2007

Purpose: The purpose of this study was to investigate the effects of health promotion program on physiological stress, perceived stress and menopausal symptoms in menopausal women. Methods: This study followed a nonequivalent control group pretest-post test design. The subjects consisted of 57 middle-aged women(30 in the experimental group and 27 in the control group) who were recruited from the community health center in J city. The subjects in the experimental group participated in a health promotion program for 8 weeks, which was composed of yoga and teaching for 1 session per week. Results: The health promotion program showed a statistical difference in blood pressure, pulse rate and perceived stress. However, there was not a statistical difference in serum cortisol, or menopausal symptoms. Conclusion: This health promotion program was partially effective for reducing stress and it was not effective for reducing menopausal symptoms in menopausal women. It is necessary to conduct a future study using a different time period, measurement time, and target population.

• 한국세라믹학회지
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• 제32권12호
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• pp.1337-1348
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• 1995

TZP/SUS- and ZT/SUS-functionally gradient materials (FGM) were fabricated by pressureless sintering in Ar-atmosphere. The sintering defects such as warping, frustrum formation, splitting and cracking which originated from shrinkage and sintering behaviors of metal and ceramics different from each other could be controlled by the adjustment with respect to the particle size and phase type of zirconia. The residual stresses generated on the metal and ceramic regions in FGM were characterized with X-ray diffraction method, and relaxed as the thickness and number of compositional gradient layer were increased. The residual stress states in TZP/SUS-FGM have irregular patterns by means of the different sintering behavior and cracking at ceramic-monolith. While in ZT/SUS-FGM, compressive stress is induced on ceramic-monolith by the volume expansion of monoclinic ZrO2 at phase transformation. Also, compressive stress is induced on metal-monolith by the constraint of warping which may be created to the metal direction by the difference of coefficient of thermal expansions. As a consequence, it has been verified that the residual stress generated on FGM is dominantly influenced by the thickness and number of compositional gradient layer, and the sintering defects and residual stress can be controlled by the constraint of the difference of shrinkage and sintering behaviors of each component.

• 한국분말재료학회지
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• 제1권1호
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• pp.52-59
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• 1994

Since the coefficient of thermal expansion (CTE) of matrix phase is larger about 4 times than that of W particle in tungsten heavy alloy, the thermal stresses due to the CTE difference between the two phases are induced in the alloy during heating and cooling processes. In the present study, a series of W heavy alloy containing various W particle volumes of 0 to 90% is made to investigate the residual stress taking place during cooling process. The CTE and residual stress of the series of alloy are measured by dilatometer and X-ray diffractometer. The residual stress of W particle is in compressive stress irrespective of W particle vol% and tends to increase with decreasing W particle vol% while that of the matrix phase is in tensile stress. The measured residual stress of W particle is about a third of calculated thermal stress. The influence of W particle vol% on the residual stress of W heavy alloy is discussed in terms of the deformation behaviors of W particle and matrix phase.

• Journal of Korean Biological Nursing Science
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• 제17권2호
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• pp.169-178
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• 2015

Purpose: This study aimed to compare work-related musculoskeletal symptoms, occupational stress and nursing work environments of nurses working in patient-sitter wards and general wards. Methods: The study surveyed 240 nurses with more than one year of experience working in both patient-sitter wards and general wards. The collected data then was analyzed by SPSS statistics version 22. Results: As for the musculoskeletal symptoms, the survey showed that 85.2% and 67.8% of the nurses had such symptoms respectively in patient-sitter wards and general wards. In terms of occupational stress, no significant difference was observed between the patient-sitter ward and the general ward (t=-0.23, p=.821). Lastly, the study showed that there is a significant difference in terms of work environment considering the scores recorded 2.65 and 2.55 points respectively in patient-sitter ward and general ward (t=2.53, p=.012). Conclusion: Follow-up research should look at ways to lower the rate of experiencing work-related musculoskeletal symptoms; analyze work performances and establish work standards to lower occupational stress; and devise measures to improve the work environment for the nurses working in patient-sitter wards.