• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.99-106
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• 2001

An overview of Silicon Carbide (SiC) Static Induction Transistor (SIT) development is presented. Basic conduction mechanisms are introduced and discussed, including ohmic, exponential, and space charge limited conduction (SCLC) mechanisms. Additionally, the impact of velocity saturation and temperature effects on SCLC are reviewed. The small-signal model, breakdown voltage, power density, and different gate structures are also discussed, before a final review of published SiC SIT results. Published S-band (3-4 GHz) results include 9.5 dB of gain and output power of 120 W, and L-band (1.3 GHz) results include 400 W output power, 7.7 dB of gain, and power density of 16.7 W/cm.

• Journal of the Korean Chemical Society
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• v.58 no.1
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• pp.49-56
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• 2014

Different pyrazoline derivatives (6a-h and 7a-h) were synthesized by cyclization of substituted chalcones with hydrazine hydrate in acidic as well as basic conditions. Both the reactions were performed under conventional heating and microwave irradiation and percentage yields were compared. All the reactions were accelerated in acidic and basic conditions under microwave irradiation, with higher yields. All the synthesized compounds were characterized by their spectral study (IR, MS, $^1H$ and $^{13}C$ NMR) and were tested for their antibacterial and antifungal activity. The compounds 6g and 7g exhibited significant activity against S. aureu, 7g against E. faecalis, 6b and 7b against E. coli and 6b, 6c, 7b, 7c against S. typhi. The compounds 6d and 7d exhibited significant activity against C. albicans and 6c against M. luteus. Rest of the synthesized compounds showed moderate to poor activity against tested species with compared to standard.

• Journal of the Korean housing association
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• v.11 no.2
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• pp.129-137
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• 2000

This study is about the difference of South and East facing Cooling load of Apartment s Houses using Dynamic Heat-flow Calculation. Therefore, the purpose of this study is come in to use Material for the Thermal Environments of Apartment Houses. The results of the analysis are below. (1) For the peak load of degree hour; The highest is "I" unit and the next high load is H, F, E, C, B, G, D and A unit for the south facing Apartment houses. The higher load is "H" unit and the next high load is I, E, F, B, C, G, D, A Unit for the east facing Apartment houses. (2) For the total load of degree day; The highest load is "I" unit and the next high load is H, G, F, E, C, B, D and A Unit for the south facing Apartment houses. The highest load is "H" unit and the next high load is I, G, E, F, B, C, D, A Unit for the east facing Apartment houses. (3) For the total load of degree day; The highest load is "H" Unit for the east facing Apartment houses and the Lowest load is "A" Unit for the south facing Apartment houses.is "A" Unit for the south facing Apartment houses.nt houses.

• Journal of Korean Society of Transportation
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• v.9 no.1
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• pp.29-46
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• 1991

The purpose of this study is to develop a parking behavior model in prior step for solv-ing parking problems in Pusan C. B. D. The results of this study are as follows; In the C. B. D of Pusan the peak parking time is between 2 and 3 o'clock P. M., and the average parking duration is 237 minutes. It means the use of parking lots is very ineffi-cient. Hence in order to shorten the parking duration, it is very urgent for drivers to chan-ge parking attitude. The walking distance from the parking lots to his destination is below 300∼500m, so the establishment of parking areas and the arrangement of parking lots in C. B. D should be planned on the base of the above walking distance. The model distinguishing between legal and illegal parking behaviors is derived from the binary decision model. The selected model has the correlation rate, η2=0.505 which is relatively high value This result shows that the detetminating judgement on the legal and illegal parking behavior is influenced mutually such factors as driver's occupation parking purpose monthly income distance to his destination averaged parking duration and age.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.415-419
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• 2018

This paper predicts and measures the C/N ratio of a beacon signal transmitted from geostationary orbit satellite KorSat 5A ($113^{\circ}E$) at a ground station located in Kimpo. Based on the ground stations, we compared the rain attenuation of the zone K of ITU-R and the rain attenuation which analyzed the domestic weather information. In ITU-R, the Korean rainfall characteristics are classified into zone K, but forecasting the rainfall intensity and attenuation of three adjacent cities based on the cumulative rainfall data per minute from 2013 to 2017. The calculation of rainfall path and attenuation is based on ITU-R recommendations. The change of the C/N according to the rainfall amount was confirmed through the 2 week satellite beacon signal C/N measurement. The predicted critical C/N was decreased to 12 dB at $A_{0.3}$. During the experiment, it was confirmed that it decreased up to 8 dB according to the concentrated rainfall.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.323-326
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• 1998

A LNA(Low Nosise Amplifer) module for the Ka-band satellite transponder has been developed, which is composed of developed two MMIC chips and 50$\Omega$ line. This LNA exhibited noise figure less than 3.12dB, linear gain higher than 32dB from 30.085GHz to 30.885GHz frequency range. Temperature test from $20^{\circ}to$ $60^{\circ}C$ of the LNA Module showed very small noise figure and linear gain variation of 0.2 dB and 0.4dB.

• Korean Journal of Pharmacognosy
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• v.5 no.2
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• pp.111-124
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• 1974

The radioactive compound sodium $acetate-U-C^{14}\;(C^{14}-acetate)$ was administered to two- and four-year-old July and September American ginseng (Araliaceae, Panax quinquefolium L.) plants and cuttings. The $C^{14}-acetate$ uptake was approximately 99%. The autoradiochromatograms suggest that the saponins isolated by preparative thin-layer chromatography contained impurities, especially those isolated from the leaf and stem extracts. The root and fruit methanol extracts yielded relatively pure saponins. The large amounts of panaquilin B and its proximity to panaquilin C on preparative thin-layer plates resulted in some admixing. The average concentration (% plant dry weight) of semi-purified saponins were high in the leaves (13.8%), as compared to fruits (9.8%), stems (7.9%) and roots (6.3%). The average percentage of $C^{14}-acetate$ incorporation into panaquilins was 4.8%. The average percentage of $C^{14}-acetate$ incorporation into panaquilins B and C was higher (1.40% and 1.13%, respectively) than that into panaquilins C, (d), G-1 and G-2 (0.75%, 0.65%, 0.13% and 0.53%, respectively). Panaquilin synthesis may be depending upon the part, collection period and age of the plant. The average percentage of $C^{14}-acetate$ incorporation into panaquilin B is high in roots (0.58%) and stems (0.48%); that into panaquilins C and (d) high in leaves (0.40% and 0.45%, respectively); and that into panaquilin E high in roots and leaves (0.55% and 0.50%, respectively). Panaquilin G-2 was synthesized in all parts of plants. The panaquilins appear to be biosynthesized more actively in July than September (exception-panaquilin G-1). Panaquilins B, C and G-1 may be biosynthesized more actively in four-year-old plants and panaquilins (d) and E more actively in two-year-old plants. The results from expectance with cuttings suggest that the panaquilins are synthesized de novo in the above-ground parts of ginseng plants, and that panaquilin G-1 may be synthesized de novo in the leaf. It is known from the tissue culture studies that panaquilins are produced by leaf, stem and root callus tissues and cailus-root cultures of American and Korean ginseng plants. Panaquilins may actively be synthesized de novo in most any cell or organ of the ginseng plants. It was verified that $C^{14}-acetate$ was incorporated into the panaxadiol portions of the panaquilins of two-year-old plants (sp. act. 0.56 mmcCi/mg) and four-year-old plants $(sp.\;act.\;0.54\;m{\mu}Ci/mg)$.

• Elastomers and Composites
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• v.46 no.4
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• pp.343-351
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• 2011

We prepared polyurethane foam/cloisite30B/phosphates composites and characterized their rise time, density, cell morphology, and thermal properties. The composites were synthesized with polyadipatediol-cloisite30B composite (f=2.0), polyether-polyol (f=4.6), polymeric 4,4-diphenyl methane diisocyanate (f=2.5), and D-580 (phenyl polyoxyalkenyl phosphate). As a blowing agent, cyclopentane and distilled water were used at various concentrations of D-580 from 0 to 2.81 wt%. The rise times of PUF/Closite30B/Phosphate composites blown with distilled water were faster than those blown with cyclopentane by 30%. The composites blown with cyclopentane had spherical-shape cells and the cell diameter was decreased with increasing D-580 wt%. While $T_g$ of the composites blown with cyclopentane linearly decreased with increasing the D-580 content, the $T_g$ of the composites blown with distilled water increased with the D-580 content. All PUF/Closite30B/Phosphate composites began to decompose from $250^{\circ}C$. The composites blown with cyclopentane showed the second thermal decomposition at temperatures higher than $500^{\circ}C$. The thermal stability of all composites increased with the D-580 content. The effect of D-580 on the thermal stability of the composites was measured higher at the composites blown with distilled water.

• Journal of Veterinary Clinics
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• v.16 no.1
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• pp.13-18
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• 1999

This study was undertaken to find out the effect of dropwort on histopathological changes of cadmium toxicity in mice. Thirty two mice of BALB/c strain were divided into a control group (A) and three experimental groups (B, C, D). Each group was consisted of four males and four females : group A received tap water and basal diet, group B received tap water and diet supplemented with 100 mg/kg of cadmium, group C received dropwort juice and diet supplemented with 100 mg/kg of cadmium, group D received dropwort juice and basal diet. All mice were dissected on the 35th day. Pathological changes in liver, kidney, spleen, heart, lung, stomach and muscle were observed. Group D showed no significant change as the control group. But group B showed many cytoplasmic vacuoles and necrosis of hepatocytes, glomerular swelling, and degeneration and necrosis of convoluted tubules in kidney, marked congestion and hemorrhage, and a large number of variably sized alveolar macrophages appearance in lung and swelling in some part of muscle fiber. On the other hand, group C showed a little convalescent changes and maintained their normal architectures in liver, kidney, lung and muscle.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.243-258
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• 1977

1 The coastal area between Youngdo and Jodo was a common coastal water not much different from other coastal waters before the construction of the breakwater between them. 2. The breakwater between the two islands shuts off the tidal currents and divides the area . into the two small isolated bays to create quite different environments. 3. To understand the differences between then, present study examined some environmental factors such as water temperature, salinity, dissolved oxygen, transparency, and major nutrients, phosphates, sillicates and nitrites and the phytoand zooplankton. The samplings were carried out monthly from March 1976 to February 1977 at 4 stations: 2 stations in each bay. 4. Some differences were observed in the environmental factors such as water temperature, salinity, dissolved oxygen and transparency between the two bays. 5. The distribution and occurence of nutrient salts of the two bays were distinctly different each other. Northern Bay had $138\%$ of nutrients in comparison with Southern Bay. 6. Phytoplankton in Northern Bay was about $200\%$ plentier than in Southern Bay. 7. Zooplankton in Southern Bay was about $180\%$ richer than in Northern Bay. 8. One of the pollution indicator species, Synedra ulna, was observed in Northern Bay and the occurence of Euglena sp. and ciliates were much higher in Northern Bay than in Southern Bay, but, in contrast, Sagitta sp. was more abundant in Southern Bay than in the other. 9. The areas of the two bays seem to be in its way to eutrophication especially in Northern Bay. 10. The two bays have been differentiated enough to identify each other.