• Herbal Formula Science
• /
• v.7 no.1
• /
• pp.143-151
• /
• 1999

To evaluate the neurotoxic effect of oxygen radicals in cultured mouse spinal dorsal root ganglion(DRG) neurons, cytotoxicity was determined by MTT assay after cultured DRG neurons were grown in the media containing various concentrations of glucose oxidase(GO). In addition, neuroprotective effect of herb extract, Epimedium Koreanum Nakai was examined by MTT assay in cultured DRG neurons. Cell viability of cultured DRG neurons was remarkably decreased by GO in dose- and time-dependent manner, and Epimedium Koreanum Nakai protected remarkably GO-induced neurotoxicity in these cultures. From the above results, it is suggested that oxygen radicals is toxic in cultured mouse DRG neurons, and herb extracts such as Epimedium Koreanum Nakai are effective in prevention of the neurotoxicity induced by oxygen radicals in cultured mouse DRG neurons.

• Journal of IKEEE
• /
• v.26 no.4
• /
• pp.553-559
• /
• 2022

In this paper, RC snubber circuit design technology for oscillation suppression in half-bridge configuration of cascode gallium nitride (GaN) field effect transistors (FETs) is analyzed. A typical wide band-gap (WBG) device, cascode GaN FET, has excellent high-speed switching characteristics. However, due to such high-speed switching characteristics, a false turn-off problem is caused, and an RC snubber circuit is essential to suppress this. In this paper, the commonly used experimental-based RC snubber design technique and the RC snubber design technique using the root locus method are compared and analyzed. In the general method, continuous circuit changes are required until the oscillation suppression performance requirement is met based on experimental experience . However, in root locus method, the initial value can be set based on the non-oscillation R-C map. To compare the performance of the two aforementioned design methods, a simulation experiment and a switching experiment using an actual double pulse circuit are performed.

• Korean Journal of Environmental Agriculture
• /
• v.38 no.3
• /
• pp.154-158
• /
• 2019

BACKGROUND: 'Shiranuhi' mandarin is a major cultivar among all late ripening type of citrus, and is widely cultivated in Korea. However, many farmers have reported scion root problems in their orchard resulting in reduced flowering and fruiting. It is necessary that the physiology of scion-rooted 'Shiranuhi' mandarin trees is further understood. METHODS AND RESULTS: This experiment was conducted to understand the growth response and physiology of scion-rooted 'Shiranuhi' mandarin hybrids. In our study, 'Shiranuhi' mandarin trees were divided into two groups: trees without scion roots (control) and trees with scion roots. The experiment was conducted in Seogwipo of Jeju, with ten replicates for each group. Growth of trees with scion roots was more vigorous and the trees were taller than the controls. Tree height and trunk diameter of scion-rooted trees were significantly higher than those of control trees. Exposed length of rootstocks of scion-rooted trees was significantly lower (by about 2 cm) than that of control trees (8.6 cm). In terms of root nutrition, carbon contents of scion-rooted trees was significantly lower than that of control trees, but nitrogen and potassium concentrations in scion roots were significantly higher than those in control roots. CONCLUSION: Based on the results, we infer that growth of scion-rooted trees was very vigorous and the content of nitrogen in these roots was higher than that in the control tree roots. Thus, the carbon/nitrogen ratio of scion roots was significantly lower than that of the control roots.

• 한국균학회소식:학술대회논문집
• /
• 2015.05a
• /
• pp.23-23
• /
• 2015

Plasmodiophora brassicae is a major disease threat for Brassica oil and vegetable crop production worldwide. The causal agent is a Plasmodiophorid, which are obligate biotrophic plant-pathogenic protists in the Rhizarian kingdom. Although the Plasmodiophorids include other important agricultural pathogens such as Polymyxa betae, Spongospora subterranea, their biology remains poorly understood due to their intracellular biotrophic life style. I will present the assembled and annotated genome of P. brassicae, with insights into developmental stage-specific. We provide the first genomic data for pathogenic Rhizaria. The exploitation of the life stage specific transcripts will shed light in the understanding of the life cycle at a molecular basis, which will in the long run help to understand and control club root disease. Our data also fill an important gap for the understanding of the eukaryotic tree of life, since this is only the third genome of the eukaryotic kingdom of Rhizaria.

• Journal of Welding and Joining
• /
• v.15 no.4
• /
• pp.36-41
• /
• 1997

제조업의 공동화 현상 및 3D 작업의 기피 현상 등으로 용접 고기량자의 구인 난 및 신규 용접인력의 감소 현상이 나타나고 있다. 이는 단기적으로는 경량 간이 용접 장치를 1인이 다수대를 운용함으로써 해결 가능하지만 적용 부위가 한정되고 수정 부위가 과다 발생되어 근본적인 해결책이라 보기는 어렵다 따라서 지능형 용접 ROBOT의 적용을 통한 용접기량자의 대체가 요구되어 지고 있다. 반면에 용접 ROBOT에 의한 고효율 및 고품질의 용접을 위해서는 용접재료, 용접기등의 발전도 중요하지만 고기량자에 준하는 최적 용접조건의 선정이 무엇보다도 중요하며 다양한 대상물에 대한 다양한 용접 사양을 만족하기 위해서는 기존 TEST를 통해서 얻어진 최적 용접 조건의 재현만으로는 한계를 가지게 되며 LASER SENSOR 등을 통한 용접부의 GROOVE 형상 혹은 ROOT GAP의 감지와 이에 적합한 용접조건을 REAL TIME으로 결정할 수 있는 용접 정보 처리 시스템이 요구된다. 본 연구에서는 광범위한 용접정보 처리 시스템중 조선분야에 비중이 제일 큰 단층 FILLET 용접부위에 대하여 용접 ROBOT SYSTEM을 적용 할 경우 표준용접 조건 및 용접조건 최적화를 위한 용접전문가 시스템의 연구결과를 소개하고 향후 전망에 대해서 의견을 제시하고자 한다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2007.05a
• /
• pp.271-273
• /
• 2007

This paper presents the experimental results of underwater discharges in 25 mm point-plane gap caused by impulse voltage. Discharge phenomena were observed by digital cameras and recorded by oscilloscope. As a result, discharge patterns in positive and negative polarity have different shapes according to applied voltage amplitudes. The positive discharge is like root but the negative discharge is similar to bush. As the voltage is increased, the discharge routs are thick and have more branches. Also the time to breakdown is inversely proportional to voltage.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2002.11a
• /
• pp.356-360
• /
• 2002

Leaky modes on a circular dielectric rod are investigated from the precisely determined normalized complex propagation constants using Davidenko's complex root finding technique. Below the cutoff frequency of the guided mode, distinct frequency regions that have unique properties are observed, such as nonphysical region, antenna mode region, reactive mode region, and spectral gap region. The effects of tro design parameters, dielectric constants and the radius of the rod, to the leaky mode characteristics are also considered.

• Journal of Mechanical Science and Technology
• /
• v.15 no.12
• /
• pp.1691-1698
• /
• 2001

In recent years, significant progress has been made in modeling turbulence behavior in plasma and its effect on transport. It has also been made in diagnostics for turbulence measurement; however, there is still a large gap between theoretical model and experimental measurements. Visualization of turbulence can improve the connection to theory and validation of the theoretical model. One method to visualize the flow structures in plasma is a laser Schlieren imaging technique. We have recently applied this technique and investigated the characteristics of a highly underexpanded pulsed plasma jet originating from an electrothermal capillary source. Measurements include temporally resolved laser Schlieren imaging of a precursor blast wave. Analysis on the trajectory of the precursor blast wave shows that it does not follow the scaling expected for a strong shock resulting from the instantaneous deposition of energy at a point. However, the shock velocity does scale as the square root of the deposited energy, in accordance with the point deposition approximation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.4
• /
• pp.318-323
• /
• 2004

When a strong electric field is applied between a sharply curved electrode and a blunt surface, the corona may result in a gas movement in the electrode gap which is directed toward the blunt surface. That is called the corona wind. It enhances heat and mass transfer between the surface and the surrounding gas. Moreover such enhancement causes no noise or vibration, which can be applied in complex, isolated geometries, and allows simple control of surface temperatures. This paper examines the relationship between the corona wind and the relative humidity. The facility consists of high voltage power supply thin tungsten wire, plate electrode, multimeter, microammeter and flow meter. Gas velocity is a linear function of voltage, relative humidity and is proportional to the square root of the current. The maximum velocities for the positive and negative corona discharge are 1.9 m/s (2.74 CMM/m), 1.5 m/s(2.15 CMM/m), respectively.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2001.11a
• /
• pp.88-91
• /
• 2001

New type of vehicles made from thin aluminum alloy are under rapid development and some product are already on the market, but when welding sheet metal joint of aluminum alloy, the main problem are burn-through by the high heat input. The purpose of this study, it is to prevent the burn-through and to shallow penetration that AC pulse welding has diminish the penetration and to lower the droplet temperature at Al sheet metal welding. In this study, we observed the bead appearance and whether it was appeared burn through or not , as the variation of the root gap in the lap and butt-joint welding process.