• Steel and Composite Structures
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• 제34권2호
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• pp.309-319
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• 2020

The objective is to study the deformation in a homogeneous isotropic modified couple stress thermoelastic medium with mass diffusion and with two temperatures due to a thermal source and mechanical force. Laplace and Fourier transform techniques are applied to obtain the solutions of the governing equations. The displacements, stress components, conductive temperature, mass concentration and couple stress are obtained in the transformed domain. Numerical inversion technique has been used to obtain the solutions in the physical domain. Isothermal boundary and insulated boundaryconditions are used to investigate the problem. Some special cases of interest are also deduced.

• Nutritional Sciences
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• 제6권2호
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• pp.67-72
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• 2003

This study was conducted to investigate the effect of oligosaccharide on the reduction of oxidative stress. Sprague-Dawley rats were fed an AIN-93G diet or a diet containing 5% soybean oligosaccharide for 6 weeks. Each group was divided into two sub-groups after streptozotocin (STZ) injection and fed the control diet or the diet containing oligosaccharide for the next 12 days. The number of fecal bifidobacteria increased significantly in groups fed oligosaccharide diet. Elevated blood glucose concentration after STZ injection declined faster in the oligosaccharide fed group. Liver thiobarbituric acid reactive substance concentration, as an indicator of oxidative stress, did not increase in groups fed the oligosaccharide diet after the STZ injection. In addition, these groups had significantly higher glutathione peroxidase activity both in the plasma and the liver than groups fed the control diet. The results of this study suggest that soybean oligosaccharide has a beneficial effect in reducing oxidative stress in streptozotocin-injected rats.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권1호
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• pp.51-57
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• 2000

Changes in the proline accumulation of ten-day-old seedlings of Vigna angularis in response to NaCl treatment were monitored. The proline content increased gradually both with an increase in the exposure time to salt stress and in a concentration-dependent manner. The increased proline accumulation was stronger in the shoots than in the roots. The salt stress by itself resulted in a significant inhibition of the chlorophyll content. Pre-treatment with proline before salinization lasting 48 h did not significantly affect the endogenous proline level in the roots, in contrast, a considerable increase of proline was observed in the shoots. The application of exogenous proline to the seedlings increased the endogenous proline content and improved the root and shoot growth under saline conditions. Detached leaves also exhibited an increased proline level in response to the applied NaCl, however, at a lower magnitude than in the intact seedlings. The proline alleviated the inhibitory effect of the NaCl in a concentration-dependent manner, thereby suggesting that salinity is a strong inducer of proline accumulation. In addition, abscisic acid eliminated the inhibitory effect of the salt salinity, thereby indicating a protective role on salinity stress and a regulatory role in proline synthesis. Accordingly, it would appear that proline may be involved in salt tolerance.

• Journal of Welding and Joining
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• 제32권2호
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• pp.37-42
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• 2014

In this study, non-load-carrying fillet welded joints fabricated using EH grade-steel are evaluated with the structural stress approach. The thickness effect was investigated by a study on welded steel joints with thickness ranging from 25 to 80mm. As-welded joint for main plate thickness of 25 to 80mm, the fatigue strength is reduced gradually. On the other hand, in case of main plate thickness of 25 to 80mm, the structural stress concentration factor increases gradually. As a result, for structural stress approach, thickness effect is not required for correction. Based on these results, a new evaluation fillet welded joint for fatigue design purposes has been proposed FAT 125.

• Journal of Welding and Joining
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• 제6권1호
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• pp.28-34
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• 1988

The fatigue test was carried out to evaluate the fatigue characteristics of the accelerated cooled (ACC) TMCP steel and its welded joint. From this study, it was confirmed that ACC TMCP steel has higher fatigue strength than conventional steels. After welding, however, the fatigue strength of ACC TMCP steel was deteriorated associated with HAZ softening when weld reinforcement was removed. On the other hand, with weld reinforcement, there is no effect of HAZ softening on the fatigue strength of welded joint because it is strongly dependant on the detail weld geometry i.e., stress concentration factor. Accordingly the fatigue strength of actual welded joint increases with decreasing the stress concentration factor of welded joint, regardless of HAZ softening.

• Journal of Welding and Joining
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• 제12권3호
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• pp.90-100
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• 1994

In this study the fatigue crack growth behavior was investigated for the surface cracks in aluminum alloy A5083-O plate and its weldment. Several kinds of specimens were tested at room temperature. The Eccentric specimens(E1.0, E2.5) subjected to combined stresses(tension+bending) were tested and the welded specimens with weld toes(TOE1, TOE2) were tested in order to verify the method to consider the stress concentration such as weld toe. It was ascertained that the surface crack growth property in the weld toe could be predicted by the corrected Pang's equation proposed in this study.

• Nuclear Engineering and Technology
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• 제32권1호
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• pp.67-76
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• 2000

Significant wall thinning due to flow accelerated corrosion(FAC）was recently reported in main feedwater pipes in 3 Korean pressurized water reactor(PWR) plants. The main feedwater pipes in one plant were repaired using overlay weld method at the outside of pipe, while those in 2 other plants were replaced with new pipes. In this study, the effect of the wall thinning in the main feedwater pipes on piping integrity was evaluated using finite element method. Especially, the effects of both the overlay weld repair and the stress concentration in notch-type thinned area on the piping integrity were investigated. The results are as follows : (1) The piping load carrying capacity may significantly decrease due to FAC. In special, the load carrying capacity of the main feedwater pipe was reduced by about 40% during about 140 months operation in Korean PWR plants. (2) By performing overlay weld repair at the outside of pipe, the piping load carrying capacity can increase and the stress concentration level in the thinned area can be reduced.

• 대한예방한의학회지
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• 제5권2호
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• pp.114-121
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• 2001

To elucidate the preventive effect of oriental medicine Gami-Ondamtang(GO) on stress, we investigated the physiological change of rats which were applied immobilization stress. For immobilization stress, rats were placed in restrainer for 12 hours a day for 3 days. During application of stress, body weight of rats was measured. After sacrifice, 8 organs were taken for measurement of organ weight. Brain was sectioned into 4 parts that are Frontal Cortex, Corpus Striatum, Hypothalamus and Hippocampus. Each part was homogenated and its catecholamine and serotonin contents were measured with HPLC. In our study, stress mainly induced increase of concentration of neurotransmitters in brain without other significant physical change of rats. GO inhibited stress induced changes of neurotransmitter content in brain.

• Environmental Analysis Health and Toxicology
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• 제13권3_4호
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• pp.143-149
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• 1998

To elucidate the preventive effect of Danchisoyosan (DS) on stress, we investigated the physiological change of rats which were applied immobilization stress. For immobilization stress, rats were placed in restrainer for 12 hours a day for 3 days. During application of stress, body weight of rats was measured. After sacrifice, 8 organs were taken for measurement of organ weight. Brain was sectioned into 4 parts that are Frontal Cortex, Corpus Striatum, Hypothalamus and Hippocampus. Each part was homogenated and its catecholamine and serotonin contents were measured with HPLC. In our study, stress mainly induced increase of concentration of neurotransmitters in brain without other significant physical change of rats. DS inhibited stress induced changes of neurotransmitter content in brain.

• 인간식물환경학회지
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• 제23권4호
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• pp.411-422
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• 2020

Background and objective: This study was conducted to find out the effects of healing farm resources and participant satisfaction on the level of stress and loyalty. Methods: The experiment was conducted on 18 subjects who participated in agro-healing activities (aged 49.5 years on average) and the concentration of cortisol, the level of stress and satisfaction with the services and program of a healing farm. The healing-agriculture activities were performed once a week, a total of 7 sessions, for 90 minutes and their saliva was collected before and after the activities. Results: The concentration of cortisol, a stress hormone, was statistically significantly reduced after the healing-agriculture activities in 5 out of 7 sessions. The total cortisol concentration showed statistically significant differences. The 6th session was comprised of different activities, compared to others, such as understanding weeds, managing a garden and making a pizza with fermentation enzymes, and the level of cortisol in the 6th session was the lowest after participating in the agro-healing activities, which indicated that the activities have the positive effect of lowering the level of stress. The level of stress was lowered from 18.39 to 16.78, which was consistent with the results of the concentration of cortisol. The level of satisfaction in the last session was below 50%, which indicated that the owner of the farm might be a little inexperienced in education and marketing on information and safety. The variables of participants including stress and satisfaction with services showed a strong influence on their loyalty. Conclusion: Satisfaction with services and loyalty to the healing farm showed a very high correlation, which was statistically significant. It also showed that participants' stress level and satisfaction with the services and program of the healing farm have a strong influence on their loyalty.