• 동의생리병리학회지
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• 제19권5호
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• pp.1303-1310
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• 2005

This study was performed to investigate the effect of Bunsimgieumgagam on the stress due to the maternal separation in rat. In this study, we researched in 'the behavioral observation', 'the changes of body weight', 'quantitative analysis of the number of BrdU-positive cells per section in dentate gyrus of hippocampus', 'free radical scavenging assay' and 'MTT-based cytotoxicity assay of SK-N-SH cell line', in order to figure out the effect on which Bunsimgieumgagam has the increase of neuron in dentate gyrus of hippocampus damaged by the stress due to the maternal separation. In the behavioral Observation, Bunsimgieumgagam was also efficacious against the decline of one's behavior and anorexia derived from the stress by the maternal separation. In the change of body weight, it showed that the Bunsimgieumgagam is effective in the recovery of weight loss caused by heavy stress(p<0.05). Also, Bunsimgieumgagam had an increasing effect, which is similar to a normal state, on DG's neuron in hippocampus (P<0.001). In free radical scavenging assay, Bunsimgieumgagam had a superior free radical scavenging effect. And it showed a significant result with the high cell proliferation effect in MTT-based cytotoxicity assay(P<0.01, p<0.001) This result suggest that Bunsimgieumgagam has an anti-stress effect and a proliferation effect of neuron in dentate gyrus of hippocampus, and it shows the potential of Bunsimgieumgagam in the treatment for the various disorders derived from children's stress.

• 대한한의학회지
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• 제31권2호
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• pp.114-123
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• 2010

Objectives: This study was performed to investigate the effect of cold stress on heart rate variability and peripheral blood flow by Doppler ultrasound in healthy subjects. Methods: We classified the subjects by their Yin or Yang tendency using a Yin-Yang questionnaire. Cold stress was taken on the left hand of subjects for 10 seconds. Heart rate variability and peripheral blood flow were measured on the right radial artery before and after cold stress. Results: The Yang tendency group showed a significant decrease of heart rate after cold stress which was not seen in the Yin tendency group. The Yang tendency group showed a decrease of LF, total power, and increase of HF after cold stress, while the Yin tendency group showed the opposite. However, there were no statistically significant differences of heart rate variability analysis between the results of the two groups before and after cold stress. Recovery time of blood flow velocity by ultrasound Doppler was significantly different between the Yin and Yang tendency groups after cold stress. Conclusion: These results suggest that people with Yin or Yang tendency may show different responses in the autonomic nervous system. Further modified studies may include the responses to various manipulation techniques in acupuncture treatment and the individual responses according to pattern identification in traditional Korean medicine.

• 대한금속재료학회지
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• 제56권11호
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• pp.779-786
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• 2018

There have been previous attempts to observe the occurrence of dynamic ferritic transformation at temperatures even above $Ae_3$ in a low-carbon steel, and not only in steels, but recently also in titanium alloys. In this study, a new approach is proposed that involves treating true stress-true strain curves in uniaxial compression tests at various temperatures, and different strain rates in 0.1C-6Ni steel, which is a model alloy used to decelerate the kinetics of ferrite transformation from austenite. The initial flow stress up to peak stress was used to analyze the change in dynamic softening phenomena, such as dynamic recovery, dynamic recrystallization, and dynamic transformation. It is worth mentioning that for predicting the occurrence of dynamic transformation, flow stress before reaching peak stress is much more sensitive to the change in the dynamic softening rate due to dynamic transformation, compared to peak stress. It was found that the occurrence of dynamic ferritic transformation could be successfully obtained even at temperatures above $Ae_3$ once the deformation condition was satisfied. This deformation condition is a function of both the strain rate and the deformation temperature, which can be described as the Zener - Hollomon parameter. In addition, the driving force of dynamic ferritic transformation might be much less than that of the dynamic recrystallization of austenite at a given deformation condition. By applying this technique, it is possible to predict the occurrence of dynamic transformation more sensitively compared with the previous analysis method using peak stress during deformation.

• The Korean Journal of Physiology and Pharmacology
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• 제27권1호
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• pp.9-20
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• 2023

The mechanism is unclear for the reported protective effect of hyperbaric oxygen preconditioning against oxidative stress in tissues, and the distinct effects of hyperbaric oxygen applied after stress. The trained mice were divided into three groups: the control, hyperbaric oxygenation preconditioning, and hyperbaric oxygenation applied after mild (fasting) or hard (prolonged exercise) stress. After preconditioning, we observed a decrease in basal levels of nitric oxide, tetrahydrobiopterin, and catalase despite the drastic increase in inducible and endothelial nitric oxide synthases. Moreover, the basal levels of glutathione, related enzymes, and nitrosative stress only increased in the preconditioning group. The control and preconditioning groups showed a similar mild stress response of the endothelial and neuronal nitric oxide synthases. At the same time, the activity of all nitric oxide synthase, glutathione (GSH) in muscle, declined in the experimental groups but increased in control during hard stress. The results suggested that hyperbaric oxygen preconditioning provoked uncoupling of nitric oxide synthases and the elevated levels of GSH in muscle during this study, while hyperbaric oxygen applied after stress showed a lower level of GSH but higher recovery post-exercise levels in the majority of antioxidant enzymes. We discuss the possible mechanisms of the redox response and the role of the nitric oxide in this process.

• 한국가시화정보학회지
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• 제15권3호
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• pp.47-51
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• 2017

In this study, we investigate the wake characteristics in laminar inflow and two different turbulent inflow cases. To solve the flow with wind turbines and its wake, we use large eddy simulation (LES) technique with actuator line method (ALM) and turbulent inflow of Turbsim. We perform the quantitative analysis of velocity deficit and turbulent intensity in laminar inflow case and turbulent inflow case with different turbulent intensity. In turbulent inflow, unsteady strong wake recovery which is highly fluctuated in time. Normalized power in turbulent inflow case is also highly fluctuated with unsteady wake recovery, while that in laminar inflow has quasi steady characteristic in power generation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.355-357
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• 1996

With the wide-spread use of rectifier in electronic equipments, such problems as electronic components failures or equipment disorders have been occurred due to current harmonics. To overcome these problems, power factor correction circuits employing boost converter have been used. The switching stress of boost converter can be reduced by snubber circuit. Recently, research activities in snubber circuits have been directed to energy recovery snubber for improving the efficiency of power converter. In this study, a new passive snubber circuit which can recover trapped snubber energy without added control is proposed for boost converter The control of boost converter with proposed snubber is the same as the conventional one. In addition, the energy recovery circuit can be implemented with a few passive components. The circuit operation is confirmed through simulation.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.617-625
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• 1998

A passive energy recovery snubber for high-power-factor boost rectifier, in which the main switch is implemented with a MOSFET, is described in terms of the equivalent circuits that are operational during turn-on and turn-off sequences. These equivalent circuits are analyzed so that the overshoot voltage across the main switch, the snubber current, and the turn-off transition time can be predicted analytically. From these results, the normalized overshoot voltage is reduced to 1 as $_W2T_on$ varies from zero to $\pi$/2, and then it is fIxed at 1 for $_W2T_on$> $\pi$/2. The peak snubber inductor current is directly proportional to the input current. The turn-offtransition time wltoffvaries from 0 to 2.57, depending on $_W2T_on$. The main switch combined with proposed snubber can be turned on with zero current and turned off at limited voltage stress. The high-power-factor boost rectifier with proposed snubber is implemented, and the experimental results are presented to confirm the validity of proposed snubber.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.668-676
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• 1998

A passive energy recovery snubber for high-power-factor boost rectifier, in which the main switch is described in terms of the equivalent circuits that are operational during turn-on and turn-off sequences. These equivalent circuits are analyzed so that the overshoot voltage across the main switch, the snubber current, and the turn-off transition time can be predicted analytically. The main switch combined with proposed snubber can be turned on with zero current and turned off at limited voltage stress. The high-power-factor boost rectifier with proposed snubber is implemented, and the experimental results are presented to confirm the validity of proposed snubber.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.413-416
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• 2006

The power source of an AC-PDP fur sustainer circuit is operated in high-voltage and high frequency switching during the process required to achieve the gas discharge current to generate light in a PDP panel. Since PDP has the characteristics of a pure capacitive load, the displacement current that occurs during charge and discharge generates considerable reactive power. An auxiliary circuitry called Energy Recovery Circuit (ERC) reduces the capacitive displacement current. However, this auxiliary topology also bears high stress in its components. In this paper, a multilevel voltage wave shaping sustainer circuit with auxiliary ERC characteristics for an AC-PDP driver is proposed. A comparative analysis and experimental results are presented.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.271-274
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• 2007

The finite element linear buckling analysis of folded plate structures using adaptive h-refinement methods is presented in this paper. The variable-node flat shell element used in this study possesses the drilling D.O.F. which, in addition to improvement of the element behavior, permits an easy connection to other elements with six degrees of freedom per node. The Box-typed structures can be analyzed using these developed flat shell elements. By introducing the variable node elements some difficulties associated with connecting the different layer patterns, which are common in the adaptive h-refinement on quadrilateral mesh, can be overcome. To obtain better stress field for the error estimation, the super-convergent patch recovery is used. The convergent buckling modes and the critical loads associated with these modes can be obtained.