• Elastomers and Composites
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• v.45 no.4
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• pp.250-255
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• 2010

From the three element non-Newtonian model of one non-Newtonian viscoelastic Maxwell elements and a elastic spring, the stress relaxation equation was derived. The various model parameters of this equation were evaluated by appling the experimental results of stress relaxation to the stress relaxation equation. The theoretical curves calculated from this model parameters agreed with the experimental stress relaxation curves. From the parameters of nonlinear viscoelastic model, the hole volume, fine structure, viscoelastic properties and mechanical properties of polymer fibers were studied. The experiments of stress relaxation were carried out using the tensile tester with the solvent chamber. The stress relaxation curves of the two types polyacrylonitrile-polyvinylchloride copolymer and another two types PVC monofilament fibers were obtained in air and water of various temperatures.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.424-429
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• 2001

Residual stresses can be produced during manufacturing processes, eg. welding, machining and plastic working, and also in service. It can be superimposed with externally applied loads, so that unexpected deformations and failures of members will be occurred. Especially, the strength and the life of welded components are affected extensively by the residual stresses distributed around their weldments not only under static loads, but also fatigue loads. These residual stresses are not kept constant, but relaxed or redistributed during service. Under static loads the relaxation takes place when the residual stress superimposed with external stress exceeds locally the yield stress of material used. It is shown that under fatigue loads the residual stress is considerably relieved by the first or few cycle loading, and then gradually relaxed with increasing loading cycles. Although many investigations in this field have been carried out, the phenomenon and mechanism of the stress relaxation by mechanical means are still not clear, and there are few comprehensive models for predicting specific effects on the stress relaxation. In this study, the effects of applied static and fatigue loads on the residual stress relaxation were Investigated, and a model to predict quantitatively the residual stress relaxation was proposed.

• Journal of Korean Biological Nursing Science
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• v.12 no.1
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• pp.8-15
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• 2010

Purpose: The purpose of this study is to investigate the effects of relaxation on stress and blood pressure of the college students induced by a cognitive distress game. Methods: The subjects for this research were 18 individuals whose stress index scores were below 4.0 (Asan city). The 18 subjects were divided into two, 9 students were assigned to the experimental group and the other 9 students to the control group randomly. Survey was used to gather data to recognize general characteristics and the level of stress and blood pressure were measured before and after cognitive distress game and relaxation. The gathered data were analyzed with frequency, $X^2$-test, Wilcoxon signed ranks test and Mann Whitney U test using SPSS 14.0 program. Results: Both level of stress and blood pressure displayed a statistically significant difference pre and post cognitive distress game. Relaxation had a statistically significant effect on level of stress. Relaxation, however, did not have statistically significant effect on blood pressure. Conclusion: The above results suggest that while relaxation was effective in reducing level of stress for college students, and therefore recommendable as a means to deal with stress. However, to investigate the effects on physiological index such as blood pressure, further research is needed.

• Journal of Welding and Joining
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• v.20 no.3
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• pp.84-90
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• 2002

The strength and the life of welded components are affected extensively by the residual stresses distributed around their weldments not only under static loads, but also fatigue loads. The residual stress can be superimposed with externally applied loads, so that unexpected deformations and failures of members will be occurred. These residual stresses are not kept constant, but relaxed or redistributed during in service. Under static loads the relaxation takes place when the external stress superimposed with the residual stress exceeds locally the yield stress of material used. It is shown that under fatigue loads the residual stress is considerably relieved by the first or flew cycle loading, and then gradually relaxed with increasing loading cycles. In this study the phenomenon and mechanism of the stress relaxation by mechanical means were investigated and a model to predict quantitatively the residual stress relaxation for the case of static and fatigue loading condition was proposed.

• Journal of the Korean Geosynthetics Society
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• v.5 no.3
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• pp.31-36
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• 2006

In this study, stress relaxation behaviors of nonwoven geotextile and geomembrane which have protection, filtration and drainage, water barrier functions, respectively were examined. 'Theory of transition phenomen' was applied to interpretate the stress relaxation behaviors of two geosynthetics. The initial and later relaxation times for stress relaxation behaviors of geosynthetics were derived from the constitutive equations. The initial relaxation behaviors of these geosynthetics were dependent on the additional strains and were especially faster with temperature. Finally, both relaxation times of geosynthetics were shorter with additional strain and temperature and the reduction of relaxation times of nonwoven geotextile were larger than those of geomembrane.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.76-79
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• 2000

Polymeric composites exhibit highly nonlinear and rate dependent behavior during loading and unloading in off-axis directions. The equilibrium state of stress during loading is lower than the state of stress produced at finite strain rates. The amount of stress relaxation during loading decreases. Interestingly, however, the stress goes up to reach to the equilibrium state of stress for a fixed displacement during unloading. The unloading behavior is quite similar to the loading behavior. The stress relaxation patterns during loading and unloading is also similar, and those depend on the fiber orientation angles and the loading and unloading rates. The AS4/PEEK thermoplastic composite is used to characterize the relaxation behavior for different off-axis angles and loading rates. There exists a transient loading region at the beginning of unloading. The effective stress and effective plastic strain concept is used to establish a master curve of stress recovery pattern for different off-axis angles and unloading rates.

• Journal of Korean Academy of Nursing
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• v.27 no.2
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• pp.289-302
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• 1997

The main purpose of this study was to identify the effects of integrated stress management program on the stress symptoms of psychophysiological patients. especially patients with peptic ulcer. The study employed a quasi-experimental design using two different experimental groups. The samples in the integrated stress management program participated in autogenic training with biofeedback. discussions on effective coping method. cognitive. behavioral, and emotional management. They were also provided with an educational booklet on stress management and an tape on progressive muscie relaxation. Each session lasted one hour and the program consisted of seven sessions over four weeks. The other group was only given an tape on progressive muscle relaxation. The data were collected from May 20 to september 25, 1996. A total 47 patients from one university hospital located in Seoul participated, experiment group 1(integrated stress management training) had 23 subjects and experiment group 2(progressive muscle relaxation training) had 24 subjects. The effects of these programs were measured by the stress symptom scale developed by Kogan(1991) which was translated by Lee(1992) and the healing status of the ulcer evaluated by a physician. The data were analyzed using Chi-square test, t- test, ANOVA, repeated measure ANOVA. The result are as follows : 1. The integrated stress management group reported a significantly lower stress symptom score than the group given the progressive muscle relaxation only. 2. The integrated stress management group showed a significantly improved ulcer status as compared to the group given a progressive muscle relaxation only. In conclusion, it was found that the integrated stress management program was more effective in decreasing self-reported stress and physiological symptoms among patients with peptic ulcer as compared to the progressive muscle relaxation group. Based on this finding, the following suggestions can be made. 1. It is necessary to broaden the scope of nursing practice for psychophysiological patients so nurses can include stress management as part of patient care. 2. It is necessary to develop stress management program for other patients whose symptoms are known to be related to stress. 3. It is necessary to replicated this study with a larger sample in different settings.

• Korean Journal of Psychosomatic Medicine
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• v.9 no.1
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• pp.93-102
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• 2001

The relaxation response is a state of profound rest, creates physiological responses directly opposite to the stress response. The relaxation response can be used to counteract the harmful effects of stress. The relaxation response can be elicited by a number of techniques such as diaphragmatic breathing, meditation, progressive muscle relaxation, autogenic training, biofeedback, etc. These relaxation methods in any mental or physical conditions associated with distress and even in normal people have useful benefits for stress control and health enhancement. These relaxation techniques are but one part of a comprehensive stress management program, through regular and continuous practice appropriate for each person, they will make an effective role in stress management. In this review, author reviewed how to practically use meditation, progressive muscle relaxation and autogenic training, in more detail. In the treatment of various stress-related disease, especially in psychiatric disorders, the relaxation technique may be a useful complement to conventional treatment and serves as an intervention between stress and disease.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2018-2025
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• 2002

It is well known that the strength and the fatigue life of welded steel components are affected extensively by welding residual stresses distributed around their weldments under not only monotonic but also cyclic loads. The externally applied loads are to be superimposed with the welding residual stresses, so that unexpected deformations and failures of the components might occur. These residual stresses are not kept constant, but relaxed or redistributed during in service. Under monotonic loads the relaxation takes place when the sum of external and welding residual stress exceeds locally the yield stress of material used. By the way, it is shown that under cyclic loads the welding residual stress is considerably relieved by the first or the early cycles of loads, and then gradually relaxed with increasing loading cycles. Although many investigations in this field have been carried out, the phenomenon and mechanism of the stress relaxation are still not clear, and there are few comprehensive models to predict amount of relaxed welding residual stress. In this study, the characteristics of the welding residual stress relaxation under monotonic and cyclic loads were investigated, and a model to predict quantitatively amount of welding residual stress relaxation was proposed.

• Journal of Preventive Medicine and Public Health
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• v.43 no.5
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• pp.445-450
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• 2010

Objectives: Emotional support and a stress management program should be simultaneously provided to clients as effective preventive services for healthy behavioral change. This study was conducted to review various relaxation and meditation intervention methods and their applicability for a preventive service program. Methods and results: The author of this paper tried to find various relaxation and meditation programs through a literature review and program searching and to introduce them. The 'Relaxation Response' and 'Mindfulness Based Stress Reduction (MBSR)' are the most the widely used meditative programs in mainstream medical systems. Abdominal breathing, Progressive Musclular Relaxation (PMR), Relaxative Imagery, Autogenic Training (AT) and Biofeedback are other well-known techniques for relaxation and stress management. I have developed and implemented some programs using these methods. Relaxation and meditation classes for cancer patients and a meditation based stress coping workshop are examples of this program. Conclusions: Relaxation and meditation seem to be good and effective methods for primary, secondary and tertiary preventive service programs. Program development and standardization and further study are needed for more and wider use of the mindbody approach in the preventive service area of medicine.