• The Journal of Korean Medicine
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• v.22 no.3
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• pp.31-41
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• 2001

Objectives : This study was performed to investigate the effects of Cordyceps Sinensis (CS) and Cordyceps Militaris (CM) on anti oxidation in the livers of ${CCl_4}-treated$ rats. Methods : Hepatotoxicity in rats was induced by carbon tetracWoride. $CCl_4-induced$ rats were administered with the extract of CS and CM. Results : In vitro, CS and CM didn't affect levels of lipid peroxide and the activities and type conversion ratio of xanthine oxidase. However, hydroxyl radicals and DPPHL radicals were decreased. In vivo, in the ${CCl_4}-treated$ rats, lipid peroxide, the activities and type conversion ratio of xanthine oxidase and superoxide radicals were increased but superoxide dismutase was decreased. After CS and CM were administered to ${CCl_4}-treated$ rats, levels of lipid peroxide, the activities and type conversion ratio of xanthine oxidase and superoxide radicals were decreased but superoxide dismutase was increased. Conclusions : These results suggest that CS and CM decrease the activities of free-radical-generating enzymes which form lipid peroxide and increase the activities of oxygen free radical scavenging enzymes.

• Natural Product Sciences
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• v.8 no.2
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• pp.35-43
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• 2002

Glycosides of herbal medicines, such as glycyrrhizin, ginsenosides, kalopanaxsaponins, rutin and ponicirin, were studied regarding their metabolic fates and pharmacological actions in relation to intestinal bacteria using germ-free, gnotobiotic and conventional animals. When glycyrrhizin (GL) was orally administered, $18{\beta}-glycyrrhetinic\;acid\;(GA)$, not GL, was detected in plasma and intestinal contents of gnotobiotic and conventional rats. However, GA could not be detected in germ-free rats. When GL was incubated with human intestinal bacteria, it was directly metabolized to GA (>95%) or via $18{\beta}-glycyrrhetinic\;acid-3-{\beta}-D-glucuronide$(>5%). Orally administered GL was effective in gnotobiotic and conventional rats for liver injury induced by carbon tetrachloride, but was not effective in germ-free rats. When ginseng saponins were orally administered to human beings, compound K in the plasma was detected, but the other protopanxadiol saponins were not detected. The compound K was active for tumor metastasis and allergy. When kalopanaxsaponins were incubated with human intestinal microflora, they were metabolized to kalopanaxsaponin A, kalopanaxsaponin I and hederagenin. These metabolites were active for rheumatoid arthritis and diabetic mellitus while the other kalopanxsaponins were not. When flavonoid glycosides were orally administered to animals, aglycones and/or phenolic acids were detected in the urine. The metabolic pathways proceeded by intestinal bacteria rather than by liver or blood enzymes. These metabolites, aglycones and phenolic acids, showed antitumor, antiinflammatory and antiplatelet aggregation activities. These findings suggest that glycosides of herbal medicines are prodrugs.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.94.1-94.1
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• 2012

폴리페닐카보실란은 페닐그룹을 포함하고 있는 카보실란계 고분자로서 열분해 후 과량의 탄소를 함유할 수 있는 세라믹 전구체이다. 카보실란계열의 고분자는 산화특성이 있어 SiOC 코팅 용도에도 사용되고 있는데, 폴리페닐카보실란은 free 탄소를 함유하는 SiOC:C 필름을 형성할 수 있다. SiOC 코팅 전구체로는 일반적으로 실리카졸, 실라잔 계열의 고분자, 실록산 계열의 고분자가 사용되고 있으나, 폴리페닐카보실란의 경우 상기 전구체에 비하여 보관 안정성 및 뛰어난 부착특성을 나타낸다. 기존 연구에서는 폴리페닐카보실란으로부터 형성된 SiOC:C 필름의 저유전막, 산화방지막, 분진방지막 등의 응용성에 대하여 고찰한 바 있다. 폴리페닐카보실란은 열처리 온도 영역에 따라 응용 분야가 달라질 수 있는데, 이에 본 연구에서는 각 열처리 온도 영역에 따라 형성되는 SiOC:C 필름의 구조적 변화를 고찰하였다. 필름 형성은 20 % 폴리카보실란 용액을 스핀코팅하고 대기상에서 경화를 실시하였으며, 질소 분위기에서 400 ~ 1200 도 범위에서 열처리하였다. 이렇게 얻어진 300 nm 두께의 필름은 XPS 표면분석과 FT-IR, Solid-NMR을 이용하여 C-Si-O 네트워크 형성의 거동을 확인하였으며, 800 도 이상에서 나타나는 특징적인 free 탄소는 Raman을 이용하여 확인하였다.

• Advances in Energy Research
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• v.6 no.2
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• pp.103-129
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• 2019

While global demand for energy increases annually, at the same time the demand for carbon-free, sulphur-free and NO_x-free energy sources grows considerably. This state poses a challenge in the research for newer sources like biomass and shale gas as well as renewable energy resources such as solar, wind, geothermal and hydraulic energy. Although wave energy also is a form of renewable energy it has not fully been exploited technically and economically so far. This study tries to explain those reasons in which it is beyond doubt that the demand for wave energy will soon increase as fossil energy resources are depleted and environmental concerns gain more importance. The electrical energy supplied to the grid shall be produced from wave energy whose conversion devices can basically work according to three different systems. i. Systems that exploit the motions or shape deformations of their mechanisms involved, being driven by the energy of passing waves. ii. Systems that exploit the weight of the seawater stored in a reservoir or the changes of water pressure by the oscillations of wave height, iii. Systems that convert the wave motions into air flow. One of the aims of this study is to present the classification deficits of the wave energy converters (WECs) of the "wave developers" prepared by the European Marine Energy Center, which were to be reclassified. Furthermore, a new classification of all WECs listed by the European Marine Energy Center was arranged independently. The other aim of the study is to assess the technological state of the art of these WECs designed and/or produced, to obtain an overview on them.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.327-331
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• 2014

LED(Light Emitting Diode) is a semiconductor device utilizing electroluminescent effect is a phenomenon in which a type of P-N junction diode, the light of short wavelength which a voltage is applied in the forward direction is released. LED is advantageous in reducing the energy as environmentally materials that can greatly reduce the carbon emissions, recent it has attracted attention IT(Information Technology) and GT(Green Technology) industry. In addition, there are advantages long life, high efficiency, and excellent response speed, LED have come into the spotlight as the illumination means to replace the existing fluorescent light and incandescent light bulb. When connecting to MR16 electronic transformer for existing LED driver circuit, due to malfunction of the dimmer and the electronic transformer, flicker occurs and linear dimming is not possible. Therefore, in this paper, we suggest an LED drive circuit there is no flicker with the corresponding dimming MR16 electronic transformer. Further, we explain the principles of the LED current control technique and the principle of the drive circuit of the LED, in order to validate the proposed circuit through prototyping and simulation.

• Korean Membrane Journal
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• v.3 no.1
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• pp.39-50
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• 2001

The counter-diffusion of two gaseous substances permeating a polymeric membrane has been investigated both experimentally and theoretically. The aim of the study was to find mutual effects, if any, that could influence the permeability and diffusivity data. The experimental data were obtained with an isostatic permeameter operating at ambient pressure and 303 K: helium, nitrogen, carbon dioxide methane were used as permeating gas at different partial pressure; helium or nitrogen as equilibrating or carrier gas. No evident mutual effect of the counter-diffusing gas was observed. The theoretical analysis gave some insight into the phenomena and it was concluded that at near-atmospheric pressures, and in the absence of swelling phenomena no mutual interaction exists. On a theoretical basis any mutual interaction between diffusing and counter-diffusing gases could only occur: i) at high pressures , when the free movement of permeating gas molecules within the polymer is hindered by the counter-diffusing gas; ii) when a large part of the free volume fraction is occupied by the counter--diffusing gas; iii) swelling phenomena modify the structure and free volume fraction of the polymer.

• Membrane and Water Treatment
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• v.10 no.1
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• pp.57-65
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• 2019

This study assessed the contribution of emergent vegetation (Phragmites australis, Typha latifolia, and Nelumbo nucifera) to the submerged surface area, the amount of biofilms attached to the submerged portions of the plants, and the treatment performance of a free water surface (FWS) constructed wetland. Results showed that a 1% increase ($31m^2$) in the vegetative area resulted in an increase of $220m^2$ of submerged surface area, and 0.48 kg Volatile Suspended Solids (VSS) of attached biofilm. As the vegetation coverage increased, effluent organic matter and total Kjeldahl nitrogen decreased. Conversely, a higher nitrate concentration was found in the effluent as a result of increased nitrification and incomplete denitrification, which was limited by the availability of a carbon source. In addition, a larger vegetation coverage resulted in a higher phosphorus in the effluent, most likely released from senescent biofilms and sediments, which resulted from the partial suppression of algal growth. Based on the results, it was recommended that constructed wetlands should be operated with a vegetation coverage of just under 50% to maximize pollutant removal.

• Advances in nano research
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• v.7 no.2
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• pp.109-123
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• 2019

In this article, the free vibration analysis of annular sandwich plates with various functionally graded (FG) porous cores and carbon nanotubes reinforced composite (CNTRC) facesheets is investigated based on modified couple stress theory (MCST) and first order shear deformation theories (FSDT). The annular sandwich plate is composed of two face layers and a functionally graded porous core layer which contains different porosity distributions. Various approaches such as extended mixture rule (EMR), Eshelby-Mori-Tanaka (E-M-T), and Halpin-Tsai (H-T) are used to determine the effective material properties of microcomposite circular sandwich plate. The governing equations of motion are extracted by using Hamilton's principle and FSDT. A Ritz method has been utilized to calculate the natural frequency of an annular sandwich plate. The effects of material length scale parameters, boundary conditions, aspect and inner-outer radius ratios, FG porous distributions, pore compressibility and volume fractions of CNTs are considered. The results are obtained by Ritz solutions that can be served as benchmark data to validate their numerical and analytical methods in the future work and also in solid-state physics, materials science, and micro-electro-mechanical devices.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.173-176
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• 2005

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.53-56
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• 2003

The disappearance of continuous yielding and the formation of an extended region in engineering stress-strain curves at tempering temperatures of 673-873K is closely related to the reduction of mobile dislocations during tempering and dynamic recovery during tensile deformation. In addition, the occurrence of discontinuous yielding at tempering temperature above 923K would be attributed to the formation of new strain-free polygonal ferrite grain.