• Smart Structures and Systems
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• v.26 no.3
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• pp.311-318
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• 2020

The goal of this study is to analytically and non-stochastically generate structural uncertainty behaviors of isotropic beams and laminated composite plates under plane stress conditions by using an interval finite element method. Uncertainty parameters of structural properties considering resistance and load effect are formulated by interval arithmetic and then linked to the finite element method. Under plane stress state, the isotropic cantilever beam is modeled and the laminated composite plate is cross-ply lay-up [0/90]. Triangular shape with a clamped-free boundary condition is given as geometry. Through uncertainties of both Young's modulus for resistance and applied forces for load effect, the change of structural maximum deflection and maximum von-Mises stress are analyzed. Numerical applications verify the effective generation of structural behavior uncertainties through the non-stochastic approach using interval arithmetic and immediately the feasibility of the present method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.12
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• pp.3943-3959
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• 2022

People are constantly exposed to stress and anxiety environment, which could contribute to a variety of psychological and physical health problems. Therefore, it is particularly important to identify psychological stress in time and to find a feasible and universal method of stress reduction. This research investigated the influence of different music, such as relaxation music and natural rhythm music, on stress relief based on Electroencephalogram signals. Mental arithmetic test was implemented to create a stressful environment. 23 participants performed the mental arithmetic test with and without music respectively, while their Electroencephalogram signal was recorded. The effect of music on stress relief was verified through stress test questionnaires, including Trait Anxiety Inventory (STAI-6) and Self-Stress Assessment. There was a significant change in the stress test questionnaire values with and without music according to paired t-test (p<0.01). Furthermore, a model based on Transformer for stress level classification from Electroencephalogram signal was proposed. Experimental results showed that the method of listening to relaxation music and natural rhythm music achieved the effect of reducing psychological stress and the proposed model yielded a promising accuracy in classifying the Electroencephalogram signal of mental stress.

• The Journal of Korean Medicine
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• v.33 no.4
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• pp.50-59
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• 2012

Objectives: This study aimed to compare the effects of high frequency electroacupuncture, low frequency electroacupuncture and manual acupuncture on the autonomic nervous system in stroke patients by using a heart rate variability measuring device. Methods: Thirty-nine participants were recruited and each participated in the high frequency electroacupuncture group, low frequency electroacupuncture group, manual acupuncture group and non-acupuncture group. Some participants received needle insertion with 100 Hz stimulation, with 2Hz stimulation and manual stimulation under mental arithmetic stress during 2 sections. Other participants maintained in the supine position without acupuncture under mental arithmetic stress during the 2 sections. Acupuncture needles were directly inserted perpendicularly to the right Liv 3 acupoint followed by delivery of electric pulses to these points for 8 minutes. Heart rate variability was measured 8 minutes before and 16 minutes after acupuncture stimulation by a heart rate variability measuring system. Results: We found a significant elevated HF total power between 1 section and 2 section and between 1 section and 4 section in the non-acupuncture group, between 3 section and 4 section in the 100Hz electroacupuncture group, and between 1 section and 2 section in the manual acupuncture group and with no change in the 2Hz electroacupuncture group. We also found a significant VLF total power between 2 section and 3 section in the 2Hz electroacupuncture group and between 1 section and 4 section and between 2 section and 4 section in the 100Hz electroacupuncture group. All four groups showed no significant differences in other parameters including heart rate mean, low-frequency power, and the ratio of low-frequency power to high-frequency power. Conclusions: This study may be a basis for research about effects of acupuncture and electroacupuncture because the parameters measured, heart rate variability, showed differences according to acupuncture.

• Journal of Oriental Neuropsychiatry
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• v.20 no.1
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• pp.165-176
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• 2009

Objectives : The purpose of this study was to assess the effects of mental stress stimulation and acupucnture applied at HT7 point on heart rate variability (HRV) in normal subjects. Methods : Thirty seven healthy volunteers participated in this study. The volunteers were randomly allocated into two groups. Both groups performed a mental arithmetic stress test and stroop color-word test for 10 minute. Then, acupuncture needles were inserted on HT7 for the study group and on non-acupucnture point for the control group. HRV was recorded three times at test time and before and after acupuncture stimulation. Results : After giving mental stress stimulation to both groups, LF and LF!HF ratio were increased and HF was decreased significantly. After giving acupuncture to study group, LF and LF/HF ratio were decreased and HF was increased, but it was not significant. After giving acupuncture to control group, LF and LF/HF ratio were increased and HF was decreased, but it was not significant. Conclusions : This results show that mental arithmetic stress test and stroop color-word test contribute to activation of the sympathetic nervous system Acupuncture at HT7 could be relatively useful to decrease sympathetic activity and balance autonomic nervous system for those who are under stress.

• Journal of the Korean Ceramic Society
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• v.31 no.10
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• pp.1141-1146
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• 1994

Cyclic fatigue experiment was carried out to predict the life time of alumina ceramics. Four kinds of model were suggested to obtain the adequate representative static stress corresponding to the cyclic stress applied to the alumina specimens. Arithmetic mean stress model gives 21.81 of the crack growth exponent, integrated stress model gives 22.15, maximum stress model gives 24.57, and equivalent static stress model gives 24.43. It is considered that the equivalent static stress model is the most reasonable and gives the best adequate crack growth exponents value.

• Stress
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• v.27 no.2
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• pp.199-204
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• 2019

Backgoround: This study aimed to examine the influence of anxiety sensitivity on task performance and physiological stress response, and to assess the effect of depression in this process for the youth population. Methods: We presented participants with an uncontrollable stress situation where they were required to perform mental arithmetic, based on the Montreal Imaging Stress Task (MIST). A total of 29 participants volunteered for this study. They completed the Anxiety Sensitivity Index-Revised and Patient Health Questionnaire-9 to measure their levels of anxiety sensitivity and depression. Two saliva samples, one before and one after the experiment, were collected to assess the change in cortisol levels as an index of physiological stress response. Results: Participants with high anxiety sensitivity showed lower performance on the mental arithmetic tasks and a significant increase in a salivary cortisol level, compared to those with low anxiety sensitivity. Furthermore, cortisol levels showed a remarkable increase where high anxiety sensitivity was coupled with depressed mood. In other hands, the levels of cortisol remained unchanged despite high anxiety sensitivity with low depressed mood. Conclusions: Our results confirm that the interaction between anxiety sensitivity and depression affects participants' task performance and stress response, as measured through behavioral tasks and physiological data with self-report indices. Also, through the physiological data, we examined that those who have a high level of anxiety sensitivity showed maladaptive responses under high stressful situation.

• Journal of Families and Better Life
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• v.18 no.3 s.47
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• pp.85-98
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• 2000

The purpose of this research is to examine the university students' stress and relationship satisfaction with their mother. For this purpose , 420 students were selected in Seoul area, and data were analyzed by the statistical methods, such as the Cronbach'a coefficient, Frequency, Percentile, Arithmetic Mean, Standard Deviation, One-Way ANOVA, Peason's Corelation and stepwised Multiple Regression Analysis though SPSS win PC+. The main results are as followed: (1) University students experience stress some extent through all the areas such as communication, dating, choosing occupation, daily activity, or pocket money. But the level of stress shows lower tendency relatively. (2)Students with the lower self-differentiation perceive more stress from mother. When using avoidance coping and personnel dependence coping, the level of stress is high. (3)Several variables(problem-focused coping, self-differentiation of emotional independence, avoidance coping, communication stress, daily activity stress, and sentimental self-differentiation) significiently influence relationship satisfaction with their mother. These variables explain 52% of the satisfaction with mother.

• Journal of the Korean Society of Safety
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• v.26 no.3
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• pp.83-90
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• 2011

It is well known that urgency resulted from time stress can be a great cause to industrial accidents. Therefore, time stress has been studied in the aspect of macroscopic view, namely industrial safety management, but has not been studied in microscopic view such as psychophysiological approach. Among diverse psychophysiological indices, Electroencephalogram(EEG) would be on of the most objective psychophysiological research technique on human errors though few research has been taken yet. This study aimed to get characteristics of human error while committing a simple arithmetic addition task by utilizing the power spectrum technique of EEG data. Each experiment was composed of 2 tasks under different condition - with and without time stress. As subjects, 5 young undergraduate students in their early twenties participated in this study. The results advocated a well-known fact that time stress downgrades the performance of human workers. However, correct answer rate and response time were not significantly influenced by time stress factor which might be explained by the constructural factor adopted in the present study. As in the previous studies, among various EEG-related measures, relative band power ratios of ${\alpha}$ and ${\beta}$ waves to sum of ${\alpha}$,${\beta}$,${\theta}$ wave powers, namely $P_{{\alpha}/({\alpha}+{\beta}+{\theta})}$ and $P_{{\beta}/({\alpha}+{\beta}+{\theta})}$ seemed to be the most effective measures to grasp variation of brain activities in time-stressed situation so that discussions were expanded about their variations.

• Journal of Oriental Neuropsychiatry
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• v.21 no.4
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• pp.163-173
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• 2010

Objectives : The objective of this study was to assess the effects of acupuncture applied at 114 and Liv3 points on heart rate variability (HRV) in normal subjects under mental stress. Methods: 36 healthy male and female subjects were recruited and randomized to a treatment group(18 subjects) or a control group (18 subjects). After 10-minutes rest period and instrumentation, both groups performed a mental stress test(Stroop color word test, Arithmetic test. four rule of arithmetic task) for l6-minutes. HRV was recorded before and after the mental stress. And then acupuncture needles were inserted on 114 and Liv3 for the study group. In the control group, they rested for l5-minutes. And Heart rate variability(HRV) was measured. Results: In the both groups, low frequency(LF) power, normalized low frequency power(LF(norm)) and ratio of low frequency to high frequency(LF/HF) was significantly increased after mental stress. Acupuncture induced significant decrease in low frequency(LF) power, normalized low frequency power(LF(norm)) and ratio of low frequency to high frequency (LF/HF) which was increased after mental stress test. In contrast, control group induced no changes. Conclusions : Acupuncture on 114 and Liv3 could be useful to decrease sympathetic activity and prevent the alteration of autonomic nervous system due to mental stress.

• Journal of Power System Engineering
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• v.22 no.6
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• pp.44-50
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• 2018

As a type of bolt with a spherical head, the ball stud is widely used as a part of a ball joint in steering or suspension systems in automobiles. Balls and studs are subjected to heat treatment suitable for each material; in particular, the shear strength of the ball stud must meet the specifications of the production company. This study evaluated the shear strength of joints according to the cooling method of ball studs subject to resistance welding. The shear stress of water cooling was higher than that of air cooling (as-received material). Note, however, th at oil cooling showed lower stress than that of as-received. When judged by standard deviation, mean, and coefficient of variation according to the arithmetic statistics and shape parameter as well as scale parameter, oil cooling is suitable.