• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.1-8
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• 2005

We fabricate PLT(5) thin film on Pt/TiO/sub x/SiO₂/Si substrate by using sol-gel method and investigate leakage current, switching and retention properties. The leakage current density of PLT(5) thin film is 3.56×10/sup -7/A/㎠ at 4V. In the examination of switching properties, pulse voltage and load resistance were 2V～5V and 50Ω～3.3kΩ, respectively. Switching time has a tendency to decrease from 0.52㎲ to 0.14㎲ with the increase of pulse voltage, and also the time increases from 0.14㎲ to 13.7㎲ with the increase of load resistance. The activation energy obtained from the relation of applied pulse voltage and switching time is about 135kV/cm. The error of switched charge density between hysteresis loop and experiment of polarization switching is about 10%. Also, polarization in retention decreases as much as about 8% after l0/sup 5/s.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.821-825
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• 2014

Steam gasification of sawdust char was performed in a thermobalance reactor at high temperature. Gasification temperature was changed from $850^{\circ}C$ to $1400^{\circ}C$ and steam partial pressure was 0.3, 0.5 and 0.7 atm. Three models of gas-solid reaction were applied to the reaction kinetics analysis and modified volumetric model was an appropriate model. Reaction control regime and diffusion control regime were distinct depending on the temperature. Apparent activation energy and pre-exponential factors for both of the regimes were evaluated and the effects of steam partial pressure were examined. $H_2$ concentration in the produced gas was two times higher than that of CO due to the gasification accompanying by the water gas shift reaction.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.701-706
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• 1999

The effect of siloxane oligomer content on thermal stability and internal stress of DGEBA epoxy resin was investigated. Siloxane-epoxy polymers having terminal epoxy group were prepared by reaction of siloxane-DDM prepolymer with DGEBA epoxy resin. Thermal stability was studied in terms of the initial decomposition temperature(IDT), temperature of maximum rate of weight loss($T_{max}$), integral procedural decomposition temperature(IPDT), and decomposition activation energy($E_t$) using TGA data. The thermal stability increased with increasing the siloxane oligomer content and showed a maximum value in the case of 5 wt% siloxane oligomer content in the blend system. While, the coefficient of thermal expansion(${\alpha}_r$) and the flexural modulus($E_r$) allowed us to study internal stress of the blend system. As the content of siloxane oligomer increases, the internal stress systematically decreases as decreasing both ${\alpha}_r$ and $E_r$.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.219-224
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• 2002

The oxidation reaction between 2,6-di-tert-butylphenol (DTBP) and oxygen adducted Co(III) complexes as a catalysis has been studied by UV-visible spectrophtometry. According to the results, main product is 2,6-di-tert-butylbenzoquinone(BQ) and the activity of the complexes is bigger in [Co(III)2(SMPD)2(Py)2]2O2 than in [Co(III)2(SPPD)2(Py)2]2O2. The rate constant is 4.55~2.12${\times}$10$-3}$s. It was found that the oxidation reaction is primary reac-tion or concentration of catalysis, O2 molecule and substance. The reasult is far from Arrhenius properties because acti-vationenergy is 10.38 kJ/mol.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.70-70
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• 2009

Si 도핑한 $Ge_2Sb_2Te_5$ 박막은 비정질상에서의 열적 안정성증가, fcc에서 hex상으로의 상전이 억제, 활성화 에너지 증가 등의 특성을 보인다. 본 연구에서는 Si 도핑에 의한 $Ge_2Sb_2Te_5$ 박막의 전기적 그리고 구조적인 특성에 관한 실험을 진행하였다. 실험에 사용된 Si 도핑 $Ge_2Sb_2Te_5$ 박막은 Si 기판 위에 radio frequency power supply를 사용해 Si과 $Ge_2Sb_2Te_5$ 타겟을 co-sputtering하여 증착하였다. Si의 sputtering 파워를 달리하여 실리콘의 농도를 다르게 증착 하였고 X-ray photoelectron spectroscopy (XPS)를 사용하여 박막의 Si 농도를 측정하였다. 증착된 박막은 질소 분위기 하에서 $5\;^{\circ}C$/min으로 열처리 하여 여러 온도와 Si 농도에서의 박막의 특성을 측정하였다. 열처리 전, 후의 박막은 X-ray diffraction (XRD) 분석을 통하여 각각의 온도에서의 구조적 특성을 분석하였다. 열처리 온도에 따르는 필름의 전기적 특성 파악을 위해서 four-point probe를 이용하여 박막의 면저항을 측정하였고 그 값은 3 회 이상 측정하여 평균값을 사용하였다. Nano-pulse scanner를 사용하여 다양한 파워범위와 펄스폭 범위에서의 박막의 상변화에 따른 반사도 차이를 측정하여 각 조성에서의 비정질-결정질상 변화속도를 분석하였다.

• Korean Journal of Food Science and Technology
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• v.23 no.4
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• pp.414-419
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• 1991

Polyphenol oxidase from Jerusalem artichoke(Helianthus tuberosus L.) tubers was partially purified by precipitation with ammonium sulfate, followed by gel filtration on Sephadex G-100. The enzyme showed maximal activity at pH 6.5 and $4^{\circ}C$. Kinetic studies indicated $K_{m}$ value of 3 mM for catechol and activation energy of 72.6 kcal/mole. As for substrate specificity of polyphenol oxidase the enzyme showed high affinity towards diphenol compounds, but not towards monophenols. The enzamatic browning was completely inhibited at 1 mM concentration of L-ascorbic acid, sodium hydrosulfite and L-cystein(HCl). The activity of polyphenol oxidase in 0.1 M potassium phosphate buffer(pH 6.5) was fairly stable for a week at $4^{\circ}C$, while it decreased remarkably at $25^{\circ}C$.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.832-842
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• 1996

TAME synthesis was studied in a fixed bed reactor with 3 different types of exchanged resins i.e, Amberlyst-15, Amberlyst-15(wet) and Amberlyst XN-1010. Amberlyst-15 has highest activity, presumably due to the higher reaction participation of the inner active sites of gel shape microparticular resin structure. The optimum reaction conditions for TAME synthesis were found as follows ; reaction temperature of $135^{\circ}C$, molar ratio(MeOH/I.A.A) of 1.0~4.0 and W/F of 2.0~4.0 gr.-cat. hr/gr.-mole. The cross-linking bond of styrene divinyl benzene was observed at $2{\theta}=20$ in XRD pattern. The DSC analysis showed that the thermal stability was in order of Amberlyst-15>Amberlyst-15(wet)>Amberlyst XN-1010. The apparent activation energies of TAME synthesis reaction with Amberlyst-15, Amberlyst-15(wet) and Amberlyst XN-1010 were 12.36, 12.46 and 14.72 kcal/mole, respectively.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.26-31
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• 1997

Bee venom (Apis mellifera) phospholipase $A_2$ solubilized in reversed micelles containing small amount of water stabilized by surfactant could catalyze the hydrolysis of dipalmitoyl phosphatidylcholine (DPPC). A sensitive and simple high performance liquid chromatographic (HPLC) methodology of phospholipase $A_2$ assay for the hydrolysis of DPPC was developed. Kinetic analysis of the phospholipase $A_2$-catalyzed reaction was found to be possible in reversed micelles. Among the surfactants and organic solvents tested, aerosol-OT and isooctane were most effective for the hydrolysis of DPPC in reversed micelles. Optimal temperature, optimal pH, $K_{m,app.},\;V_{max.,app.}$ and activation energy were determined to be $35{\sim}40^{\circ}C$, 7.0, 8.73 mM, 2.83 units/㎎ protein and 12.31 kcal/mole, respectively. The hydrolysis activity was dependent on water content and maximum activity was obtained at R value (=[water]/[aerosol-OT]) of 10.0.

• Korean Journal of Food Science and Technology
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• v.24 no.4
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• pp.382-386
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• 1992

Effect of temperature on some quality characteristics of aqueous extracts of sea mustard was investigated. The concentration of total solids and protein and their yields in the extracts were increased as the extraction temperature raised from $50^{\circ}C$ to $100^{\circ}C$ during initial period of extraction. However the lower values of the percent of supernatant was obtained at $50^{\circ}C$ and $100^{\circ}C$. The percent of yields of solids and protein for 1 hour extraction at $100^{\circ}C$ were 21.56% and 4.7%, respectively. The highest viscosity, which was $2.5{\sim}4.0$ times of higher values of the other extracts, was obtained by 2 hours extraction at $100^{\circ}C$. The turbidity was gradually decreased after 1 hour extraction. The activation energy calculated for initial increase rate of solid and protein concentration were 1.18 and 3.90 Cal/mole, respectively.

• Korean Journal of Microbiology
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• v.24 no.2
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• pp.133-140
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• 1986

Extracts of CO-autotrophically grown cells of Acinetobacter sp. 1 were shown to use thionin, methylene blue, or 2,6-dichlorophenol-indophenol, but not NAD, NADP, FAD, or FMN, as electron acceptors for the oxidation of CO under strictly anaerobic conditions. The CO dehydrogenase (CO-DH) in the thes bacterium was found to be an inducible enzyme. The enzyme activity was determined by an assay based on the CO-dependent reduction of thionin. Maximal reaction rates were found at pH 7.5 and $60^{\circ}C$, and the Arrhenius plot revealed an activation energy of 6.1 kcal/mol(25.5kJ/mol). THe $K_m$ m/ for CO was $154{\mu}M$. Known metalchelating agents tested had no effects on the CO-DH activity. No divalent cations tested affect the enzyme activity significantly escept $Cu^{2+}$ which suppressed the activity completely. The enzyme was inhibited by glucose and succinate. The same extracts catalyzed oxidation of hydrogen gas and formate with thionin as electron acceptor. The CO-DH of Acinetobacter sp. 1 was to have no immunological relationship with that of Pseudomonas carboxydohydrogena.