• 대한기계학회논문집A
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• 제27권1호
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• pp.175-182
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• 2003

The fatigue life of welded joints is sensitive to welding residual stress and complexity of their geometric shapes. To predict the fatigue life more reasonably. the effects of welding residual stress and its relaxation on their fatigue strengths should be considered quantitatively, which are often regarded to be equivalent to the effects of mean stresses by external loads. The hot-spot stress concept should be also adopted which can reduce the dependence of fatigue strengths for various welding details. Considering the factors mentioned above, a fatigue life prediction model using the modified Goodman's diagram was proposed. In this model, an equivalent stress was introduced which is composed of the mean stress based on the hot-spot stress concept and the relaxed welding residual stress. From the verification of the proposed model to real welding details, it is proved that this model can be applied to predict reasonably their fatigue lives.

• 기본간호학회지
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• 제7권1호
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• pp.109-121
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• 2000

Increasingly nursing science is embracing the concepts and methodology derived from psycho-neuroimmunology. It has been previously shown that stress increases and immune function declines in students undergoing examinations. To date, however, no many studies have been reported on stress levels, immune function and interventions in Korean students undergoing their first clinical nursing rotation. It was proposed that nursing students during their first clinical rotation experience increase in stress because of the novelty of the situation and their lack of clinical knowledge. It was also hypothesized that biofeedback and progressive relaxation, methods of self-regulation of involuntary autonomic nervous system responses, would reduce the stress response. The purpose of this study is to test the effectiveness of progressive muscle laxation using biofeedback The effectiveness of the experimental methods was tested by measuring the degree of symptoms of stress (SOS) and the values of ephinephrine, pulse rate, blood pressure and natural killer cells. The subjects of this study were thirty nursing students divided into two groups: experimental group was progressive muscle relaxation group using biofeedback and control group. This study was conducted for 8 weeks of clinical practice. Biofeedback training was done by software developed by J&J company (1-410 form for progressive muscle training). Progressive muscle relaxation training according to Jacobson's Theory was done by messaged word from biofeedback. The data was analyzed using Chronbach' ${\alpha}$ and t-test of the SPSS program and the significance level of statistics was 5%. The results of the study were : 1) The progressive muscle relaxation training using biofeedback was effective for the reduction of symptoms of stress(t=-4.248, p<.001) under clinical practice stress conditions. 2) The progressive muscle relaxation training using biofeedback was not effective for the values of epinephrine(t=-1.294, p=.206). 3) The progressive muscle relaxation training using biofeedback was effective for the reduction of systolic blood pressure (t=-2.757, p=.01). 4) The progressive muscle relaxation training using biofeedback was effective for the reduction of diastolic blood pressure (p=-2.032, 0=.05). 5) The progressive muscle relaxation training using biofeedback was not effective for the reduction of pulse rate(t=-15, p=.988). 6) The progressive muscle relaxation training using biofeedback was effective for the maintenance of natural killer cells (t=2.381, p=02). The first clinical rotation for student nurses is a stressful experience as seen by the rise in the SOS in the control group. Biofeedback using progressive muscle relaxation were effective in preventing the rise of symptoms of stress and the blood pressure means when comparing the pre to post clinical experience, The mean natural killer cell count was depressed in the control group but not significantly different in the experimental groups, It is proposed here that stress via the hypothalamic - pituitary - adrenal axis suppressed the NK cell count whereas the relaxation methods prevented the rise in stress and the resulting immune depression. We recommend relaxation techniques using biofeedback as a health promotion technique to reduce psychological stress. In summary. the progressive muscle relaxation training using biofeedback was effective for the reduction of symptoms of stress under clinical practice stress conditions.

• 동의신경정신과학회지
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• 제17권3호
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• pp.57-65
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• 2006

Objectives: The purpose of this research is to investigate the effects of Benson's Relaxation Technique on autonomic nervous system for normal subjects with Heart Rate Variability(HRV) and find out relationship with anti - stress effects. Methods: First, Benson's Relaxation Technique was applied on 5 normal subjects for three weeks. Then HRV was examined for 15 minutes Benson's Relaxation Technique application. Next, Benson's Relaxation Technique each 8 times was applied on 5 normal subjects for 1 weeks. Then :HRV was examined each 5 minutes before and after Benson's Relaxation Technique application. Results: 1. SDNN, SDSD increased continuously in HRV for three weeks Benson's Relaxation Technique application. 2. Mean HRV, SDNN, SDSD were significant different in HRV between before and after Benson's Relaxation Technique application at fourth week. Conclusion: The results suggest that Benson's Relaxation Technique application have shown anti-stress effects and the more Benson's Relaxation Technique is repeated, the more effective.

• 대한금속재료학회지
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• 제49권11호
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• pp.823-830
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• 2011

Structural change in an amorphous alloy was measured by applying a load below the global yield stregth at ambient temperatures. It was observed that the magnitude of the apparent structural change occuring in the amorphous alloy is determined by the compatative relationship between the stress-induced disordering process and the thermally-activated relaxation process. Structural disorder was observed to take place even at a stress well below the global yield, and the degree of the disorder was increased abruptly at the earlier stage of loading and saturated with time. In the mean time, unlike the previous belief, the relaxation process was observed to occur even at embient temperatures, and the degree of the relaxation was observed to increase linearly with time. The analytical equation predicting the structural change was proposed.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.125-129
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• 2002

Authors had developed the model for the fatigue life assessment of welded details considering residual stress and its relaxation. The model consists of three ingredients; a hot-spot stress approach, a residual stress relaxation, and an equivalent stress. The equivalent stress is induced by stress ranges and the ratios between the applied mean stresses and the ultimate stress of material. Once being tuned with two specific fatigue tests by using load carrying cruciform joint, this model can be applied to many kinds of welded details which structural stress concentration factors are different from each other. This paper reports the application of the proposed model for various welded details including cover plate, longitudinal stiffener, gusset and side attachment. From the investigation of predicted results by using the proposed model it was shown that the ambiguous fatigue characteristics of the various details influenced widely by the welding residual stress are clarified, and also the model could be applied to assess fatigue life of general welded structures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.59-62
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• 1999

Inception and propagation of electrical tree and properties of Partial discharge(PD) pulses accompanying with tree as a function of needle tip radius in low density polyethylene were discussed. To study on these characteristics in different tip radius, we used specimens with needle-plane electrode system made of LDPE, observed inception and propagation of electrical tree by optical microscope with computer and investigated the characteristics of the phase resolved PD pulses accompanying with propagation of electrical tree. The PD quantities detected and analysed were PD magnitude, mean phase angle, average discharge, and the statistical characteristics of the PD pulses. As the tip radius ${\gamma}$ increases, tree inception stress E$\sub$i/ converges to constance value. This result suggests that tree inception stress E$\sub$i/ increases due to stress relaxation when the tip radius is small. Branch-type electrical tree was formed When E$\sub$i/ is 640-750[kV/mm]. bush-type electrical tree when E$\sub$i/ is 370∼400[kV/mm], branch-like electrical tree when E$\sub$i/ is 370-400[kV/mm].

• 동의생리병리학회지
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• 제26권4호
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• pp.566-571
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• 2012

The purpose of this study was to assess the effects of herbs aroma on relaxation in highly stressed volunteers with heart rate variability(HRV) and SACL(stress arousal check list). 28 highly stressed volunteers participated in this study. The volunteers were examined with heart rate variability(HRV) and SACL(stress arousal check list) before and after smell herbs aroma. After smelling powder incense composed with oriental medicine herbs, mean RR, SDNN, LF, HF, TP were incresed and mean HRV, LF/HF ratio were decreased, but it was not significant. And VLF, norm HF were incresed and norm LF was decreased significantly. This results show that the powder incense composed with oriental medicine herbs effects on decresing sympathetic nervous activity and increasing parasympathetic activity and rebalancing autonomic nervous system who were under stress.

• 한국자동차공학회논문집
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• 제3권1호
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• pp.1-12
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• 1995

Isothermal and thermal-mechanical fatigue characteristics of 12Cr heat resisting steel used for high temperature applications were investigated including hold time effects. Isothermal low cycle fatigue test at $600^{\circ}C$ and in-phase, out-of-phase thermal-mechanical fatigue test at 350 to $600^{\circ}C$ were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Regardless of thermal-mechanical and isothermal fatigue tests, cyclic softening behavior was observed and much more pronounced in the thermal-mechanical fatigue tests with hold times due to the stress relaxation during the hold time. The phase difference between temperature and strain in thermal-mechanical fatigue tests resulted in significantly shorter fatigue life for out-of-phase compared to in-phase. The differences in fatigue lives were dependent upon the magnitudes of plastic strain ranges and mean stresses. During the hold time in the strain-controlled fatigue tests, the increase in the plastic strain range and the stress relaxation were observed. It appeared that the increase in plastic strain range per cycle and the introduction of creep damage made important contributions to the reduction of thermal-mechanical fatigue life with hold time, and the life reduction tendency was more remarkable in the in-phase than in the out-of-phase thermal-mechanical fatigue. Isothermal fatigue tests performed under the combination of fast and slow strain rates at $600^{\circ}C$ showed that the fatigue life decreased as the strain rate and frequency decreased,especially for the low strain ranges.

• 혜화의학회지
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• 제22권2호
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• pp.81-92
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• 2014

Objective : The purpose of this study was to assess the effects of Cyperus rotundus L. essential oil on relaxation in highly stressed volunteers with heart rate variability(HRV) and electroencephalography(EEG). Methods : 11 highly stressed volunteers participated in this study. The volunteers were examined with HRV and EEG before and after inhalation of Cyperus rotundus L. essential oil. Results : After smelling Cyperus rotundus L. essential oil, mean RR(mean of RR intervals) was incresed significantly(p<0.01), mean HRV(mean of heart rate), HF(high frequency) were decreased significantly(p<0.01). norm LF(low frequency), LF/HF ratio were decreased significantly(p<0.05), norm HF(normalized high frequency) was increased significantly(p<0.05) on HRV. After smelling Cyperus rotundus L. essential oil, relative ${\theta}$ power was decreased significantly(p<0.05) at P3(left parietal) and relative ${\alpha}$ power was increased significantly(p<0.05) at Fp1(left prefrontal), Fp2(right prefrontal) and relative ${\beta}$ power was decreased significantly(p<0.05) at Fp1(left prefrontal) and relative ${\gamma}$ power was decreased significantly(p<0.05) at Fp1(left prefrontal) on EEG. Conclusions : This results show that inhalation of Cyperus rotundus L. essential oil effects on relaxation and decreasing stress.

• 감성과학
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• 제22권1호
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• pp.55-64
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• 2019

스트레스는 자율신경계 반응의 변화를 수반하며, 특히 심박변이도 지표는 스트레스에 의한 자율신경계의 활동을 반영하는 양적 지표로 사용된다. 본 연구에서는 스트레스 완화를 위한 산소와 색채 조명의 복합 자극이 제시되는 동안 자율신경계 반응의 변화를 확인하였다. 42명의 실험참가자는 지난 2주 동안 경험한 스트레스에 대한 증상들을 스트레스 반응 척도에 평가하였다. 스트레스 평가 후, 실험참가자는 복합 자극을 제시받았고, 자극 제시 전과 후, 그리고 자극이 제시되는 동안 심전도 신호가 기록되었다. 자극 조건은 30% 농도의 산소와 백색 조명, 산소와 주황색 조명과 산소와 파란색 조명의 조합의 세 가지로 구성되었다. 심박률(HR), R-R간격의 표준편차(SDNN), 연속한 R-R 간격 차이 값의 평균제곱근(RMSSD)과 심박변이도의 저주파 성분(LF), 고주파 성분(HF), 그리고 LF와 HF의 비율을 심박변이도 지표로 추출하였다. 이들 지표는 자극 제시 전과 후의 평균을 비교하는데 활용되었다. 결과는 자극 조건이 제시되고 난 후, HR과 LF/HF ratio의 유의한 감소를 보여주었다. 특히, 산소와 파란색 조명이 제시된 조건에서 다른 두 조건보다 유의하게 큰 RMSSD와 HF의 증가 및 LF/HF ratio의 감소가 나타났다. 이는 30% 농도의 산소와 파란색 조명의 조건이 부교감신경의 활성화에 의한 자율신경의 균형을 유발하여 스트레스 이완에 가장 효과적임을 보여주었다.