• E2M - 전기 전자와 첨단 소재
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• 제5권4호
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• pp.385-392
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• 1992

급속열산화방법으로 400-650.deg.C의 온도범위에서 10-600초 동안 n형 InP기판위에 InP자연산화막을 형성하고 산화막의 성장율, 성장기구와 화학적 구성성분 및 전기적 성질등을 조사하였다. InP자연산화막의 두께는 산화시간이 제곱근에 비례하였고 산화온도에 대하여 지수함수적으로 증가하였다. InP자연산화막은 320.deg.C의 온도에서 초기성장이 이루어지고 산소원자들이 InP내부로 확산되는 과정으로 형성되며 산화막 형성에 필요한 활성화에너지는 1.218eV이었다. InP 자연산화마그이 화학적성분은 In$_{2}$)$_{3}$, P$_{2}$O$_{5}$ 및 InPO$_{4}$의 산화물이 혼합하여 구성된다. Au/InP쇼트키다이오드와 InP자연산화막을 게이트절연물로 사용한 MOS 다이오드의 전기적 특성은 다이오드방정식에 따르는 전류-전압특성을 보였다.

• E2M - 전기 전자와 첨단 소재
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• 제9권4호
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• pp.351-356
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• 1996

The quartemary system ceramics 0.5[xPb(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$-(1-x)Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_{3}$]-0.5[yPbTiO$_{3}$-(1-y) PbZrO$_{3}$ for piezoelectric actuators were prepared bv the were added to the raw materials up to 5 mole. Sintering temperature was varied form 1000.deg. C to 1200.deg. C. Sintering characteristrics, dielectric and piezoelectric properties were then investigated. Piezoelectric properties of sample prepared by the molten salt method were improved compared to those prepared by the conventional method. Addition of PZN shifted morphotropic phase boundary to more Zr-rich composition and decreased the piezoelectric properties.

• Journal of Welding and Joining
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• 제13권2호
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• pp.122-131
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• 1995

The effects of cooling rate on the microstructures, precipitation of Cu-cluster, .epsilon.-Cu and impact toughness of high strength low alloy(HSLA) steel were studied using hardness tester, impact tester, DSC(differential scanning calorimetry), AES(auger electron spectroscopy) and TEM(transmission electron microscopy). Not only the Cu-precipitates but also the segregation of Cu, As, Sb, P, S, N, Sn along grain boundary were not observed at the specimens heat treated from 800.deg. C to 300.deg. C with the cooling time of 12-125 sec. The Cu-cluster, .epsilon.-Cu are formed by introducing ageing after cooling and the effect of precipitates on hardening increase after cooling was the same in all cooling rate. The peak hardness was obtained at an ageing of 500.deg. C in all cooling conditions. The impact energy become higher as the cooling time increases. This fact can be explained to be due to the tempering effect applied on the cooling stage since the present alloy has a relatively high Ms temperature and the local high concentration of the retained austenite.

• 미생물학회지
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• 제31권2호
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• pp.157-165
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• 1993

A 1, 4-.betha.-D-xylanase, designated as xylanase II, was purified from the culture filtrate of Trichoderma koningii ATCC 251131 by column chromatography on Sephadex G-75, SP-Sephadex C-50, DEAE-Sephadex A-50 and Sephadex G-50 with an overall yield of 6.97%. It has a molecular weight of 21.000 and an isoelectric point of 9.4. The enzyme activity is optimal at pH 5.0 and at a temperature of 50.deg.C. Xylanase II is stable up to 50.deg.C, while 40 and 90% of its activity are lost after the incubation for 30 and 60 min at 60.deg.C. The enzyme degrades xylan with relatively high activity, as well as carboxymethylcellulose and Avicel. Its $K_{m}$ values for oat-spelt xylan, larchwood xylan and Avicel are 7.48, 1.98 and 13.33 mg/ml, respectively. The hydrolysis products of oat-spelt xylan by xylanase II are xylose, xylobiose, xylotriose and arabinoxylotriose, while the reaction products of larchwood xylan are xylose, xylobiose, xylotriose and small amount of higher oligomers. The action paterns of the enzyme demonstrate that xylanase II is endo-enzyme.

• 동력기계공학회지
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• 제17권6호
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• pp.25-32
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• 2013

Biodiesel is technically competitive with it and offers technical advantages over conventional petroleum diesel fuel. Biodiesel is an environment friendly alternative liquid fuel that can be used in any diesel engine without modification. In this study, (dP/dCA)max and heat release, emission characteristics with different fuel injection timings are compared between diesel fuel and biodiesel in the D.I. diesel engine with T/C. The engine was operated at five different fuel injection timings from BTDC 6deg to 14deg at 2deg intervals and with four different loads at engine speed of 1800rpm. The experiments in a test engine showed that ranges between low and high of (dP/dCA)max got narrower, as the engine load increased, BD blend rate increased, and fuel injection timing was delayed. Cumulative heat release increased with the advanced fuel injection timing. NOX emissions decreased with the delays of fuel injection timing.

• E2M - 전기 전자와 첨단 소재
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• 제8권4호
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• pp.458-463
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• 1995

The optical and electrical properties of $C_{22}$-Quinolinium(TCNQ) Langmuir-Blodgett films have been studied depending on the annealing temperatures. The optimal properties were investigated using UV/visible(300-800[nm]) absorption spectra and FTIR(Fourier-transformed- infrared) absorption measurements. The electrical properties were investigated in a frequency range of 10[Hz]-13[MHz]. The UV/visible absorption spectra at room temperature show that there are four characteristic peaks at 320, 380, 494 and 678[nm]. These absorption peaks decrease very rapidly above the annealing temperature of 180[.deg. C], which is due to a structural change of TCNQ. The FTIR absorption measurements strongly support the result of the UV/visible absorption spectra, because the absorption peak of TCNQ- at 2181[$cm^{-1}$ /] also decreases above 140[.deg. C]. The frequency-dependent dielectric constant shows that there is a dielectric dispersion near 1[MHz] which is due to an orientational polarization of the molecules inside the film. The overall frequency-dependent dielectric constant is higher near 80[.deg. C]. It may be due to a softness of the alkyl chains.s.

• 약학회지
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• 제3권1호
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• pp.23-25
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• 1957

The herb of Geranium sibirium L, a drug knwon as "Chui Sonni Poul" distributed widely, has been used as a folk-medicine for the treatment of diarrhea. The dried entire herb is boiled with methanol and methanol is distilled of from the filtered methanol extract under reduced pressure. Then the extract is boiled with water and filtered off. From the filtrate, the following substances are isolated and identified by treating with organic solvents as ether, ethyl acetate, and etc.: 1. Gallic acid: a colorless needle crystal which is soluble in alcohol and water. mp.235.deg. C, positive (dark blue) against the ferric chloride reagent. 0.76 percent of gallic acid is yielded from the herb. 2. Quercetin: a light yellow crystal. mp.194.deg. C. negative against the ferric chloride reagent. 3. Ellagic acid: a light yellow crystal which is insoluble in ehter and acetone and slightly soluble in alcohol. Positive (blue) against the ferric chloride reagent. The crystal obtained by recrystalisation from pyridine, does not melt by 360.deg. C. Represent a yield of 0.03 percent from the herb. 4. Crude tannin: a approximately 7.6 percent of crude tannin is yielded by treating with ethyl acetate. gallic acid and querceetin are yielded by hydrosis with dliute sulfuric acid. Based on the above results, the following suggestion could be recommendable; Geraed in the Japanese Pharmacoeia VI.acoeia VI.

• Journal of Welding and Joining
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• 제8권4호
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• pp.27-34
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• 1990

Integranular corrosion behaviors of KAL (Knife Line Attack) and mechanical properties such as tensile and creep rupture were investigated for the tube material used for nearly 20 years under the condition of 463.deg. C and 28 $kg/cm^2$. Based and weld metal were austenitic stainless steel AISI 321 containing Ti, AISI 347 containing Nb, respectively. KLA is a kind of the intergranular corrosion which often occurs just near the HAZ (heat affected zone) of AISI 321 and AISI 347 stainless steel due to the grain boundary sensitization. In KLA zone, intergranular corrosion crack has propagated outwards from the inner surface and carbides of white and narrow band type assuming as (Cr, Fe) carbide were confirmed. All the delta-ferrite formed in the weld metal during weld solidification has been transformed into sigma-phase since delta-ferrte was exposed for 20 years at 463.deg. C. Elongation was very low at the range from room temperature to 600.deg. C and it was confirmed that creep-rupture properties were not consideralbly affected.

• 대한기계학회논문집
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• 제8권5호
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• pp.425-434
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• 1984

본 연구에서는 ［0˚/90˚］$_{2s}$, Gr/Gp 복합 적층판에 대해서 접착면의 비율과 폴리에스테르 필름의 구멍의 형상이 적층판의 인장 성질과 파괴인성에 미치는 영향에 대한 실험적인 결과를 얻고자 한다.다.

• 대한기계학회논문집
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• 제12권6호
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• pp.1415-1427
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• 1988

본 연구에서는 막냉각되고 있는 수평평판에서 분사각도와 분사율의 변화가 열 전달계수에 미치는 영향을 주 연구대상으로 하였다. 열전달계수의 측정을 위하여 나 프탈렌 승화법을 이용하였고, 열전달 계수에 가장 큰 영향을 미치는 유동장에 대한 이 해를 위해 슐리렌 광학계를 이용한 유동의 가시화 실험을 수행하였다. 분사각도는 Fig.1에서와 같이 y축 방향으로의 수직분사(case 1), 유동방향(x축방향)dp eogo 35˚ 경사진 분사(case 2), 그리고 유동의 직각방향(Z축)dp eogo 35˚경사진 분사(case 3) 등 3가지의 경우에 대해 실험하였고, 분사율은 0.5, 1.0, 1.8로 변화시켰다.