• 한국응용과학기술학회지
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• 제10권1호
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• pp.67-74
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• 1993

1, 2-Isopropylidene glycerol produced by ketalyzation of glycerol with aceton was esterified with long chain fatty acids in the presence of a Mucor miehei lipase to obtain 1, 2-isopropylidene 3-long chain acyl glycerol. To determine optimal conditions for the esterification reaction, esterification was proceeded as a reversible second-order reaction in various parameters that are enzyme/substrate ratio 0.096g/g at reaction temperatures ranged from $25^{\circ}C$ to $70^{\circ}C$. The order of reaction rate of fatty acids were lauric acid, myristic acid, oleic acid, and stearic acid. The range of their activation energies were from 7.8 to 11.4 (kcal/mol) and that of entropies of activation which have negative values were from 42.8 to 52.5(e.u.).

• 한국수소및신에너지학회논문집
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• 제14권1호
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• pp.1-7
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• 2003

In this study, activity changes of $Ni/Ce-ZrO_2$ catalyst for steam reforming reaction in the various steam treatment condition were investigated and BET, XRD and XPS analysis were introduced to characterize the catalyst before and after treatment. Activity test showed that $Ni/Ce-ZrO_2$ catalyst had good activity after reduction in steam reforming reaction but deactivated rapidly after steam treatment at high temperature. Activities of deactivated catalyst by steam was recovered to die previous activity level after reduction using hydrogen rich gas. It was observed that catalytic activity was preserved after repeated steam treatment, too. It showed that change of catalytic activity due to steam treatment is perfectly reversible. From the BET, XRD and XPS analysis, deactivation of $Ni/Ce-ZrO_2$ catalyst was due to the transition from Ni, that is activity site for steam reforming reaction, to $NiAl_2O_4$ in steam treatment at high temperature.

• 한국재료학회지
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• 제30권5호
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• pp.217-222
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• 2020

The design and fabrication of catalysts with low-cost and high electrocatalytic activity for the oxygen evolution reaction (OER) have remained challenging because of the sluggish kinetics of this reaction. The key to the pursuit of efficient electrocatalysts is to design them with high surface area and more active sites. In this work, we have successfully synthesized a highly stable and active NiCo₂S₄ nanowire array on a Ni-foam substrate (NiCo₂S₄ NW/NF) via a two-step hydrothermal synthesis approach. This NiCo₂S₄ NW/NF exhibits overpotential as low as 275 mV, delivering a current density of 20 mA cm^-2 (versus reversible hydrogen electrode) with a low Tafel slope of 89 mV dec^-1 and superior long-term stability for 20 h in 1 M KOH electrolyte. The outstanding performance is ascribed to the inherent activity of the binder-free deposited, vertically aligned nanowire structure, which provides a large number of electrochemically active surface sites, accelerating electron transfer, and simultaneously enhancing the diffusion of electrolyte.

• 마이크로전자및패키징학회지
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• 제27권4호
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• pp.11-17
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• 2020

Copper has been proved to be the best catalyst for electrochemical CO2 reduction reaction, however, for optimal efficiency and selectivity, its performance requires improvements. Electrochemical CO2 reduction reaction (RR) using CuO nanowire electrode was performed with different concentrations of KHCO3 electrolyte (0.1 M, 0.5 M, and 1 M). Cu(OH)2 was formed on Cu foil, followed by thermal-treatment at 200℃ under the air atmosphere for 2 hrs to transform it to the crystalline phase of CuO. We evaluated the effects of different KHCO3 electrolyte concentrations on electrochemical CO2 reduction reaction (RR) using the CuO nanowire electrode. At a constant current (5mA), low concentrated bicarbonate exhibited a more negative potential -0.77 V vs. Reversible Hydrogen Electrode (RHE) (briefly abbreviated as VRHE), while the negative potential reduced to -0.33 VRHE in the high concentration of bicarbonate solution. Production of H2 and CH4 increased with an increased concentration of electrolyte (KHCO3). CH4 production efficiency was high at low negative potential whereas HCOOH was not influenced by bicarbonate concentration. Our study provides insights into efficient, economically viable, and sustainable methods of mitigating the harmful environmental effects of CO2 emission.

• 한국항공우주학회지
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• 제32권4호
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• pp.95-100
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• 2004

본 논문에서는 기계적 링키지의 가역 (Reversible) 비행조종장치를 갖는 항공기익 조종간 조종력 재현 시스템 (CLS : Control Loading System) 개발을 목적으로 조종력 재현 장치 제어기 설계, 시스템 구성, 조종력 재현 장치 운용 환경을 구축하고 시험평가를 수행한 내용을 기술한다. 시스템 구성은 기계적인 외형부분과 힘을 측정하는 센서부분과 스틱에서의 반력을 재현하는 모터부분과 안전장치로 되어 있다. 하드웨어와 PC간의 입출력 신호 연결 및 제이기로 dSpace 사의 DS1103 DSP장치를 사용하였다. 대상항공기 (KT-1)의 비행 조종장치 모델링을 바탕으로 피치축과 롤축에 대한 CLS를 구성하고, 조종력 재현장치 제어법칙 설계와 모니터링 S/W 및 실시간 시험평가도구를 포함한 시험평가 및 운용환경 대해 기술하였다. 정적 및 동적시험을 수행하여 실제 대상항공기 데이터와 비교함으로써 개발한 시스템을 검증하였다.

• 한국응용과학기술학회지
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• 제16권4호
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• pp.273-279
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• 1999

In order to study a reversible photoisomerization of disperse red l(DR 1) attached on natural polymers, cellulose acetate containing DR l(DR 1/CA adduct) was prepared, and the changes of UV/VIS spectra of its solution(benzene, DMAc). thick film, and LB film were investigated by alternate irradiation with two different wave length lights. DR 1/CA adduct was prepared through tosylation of partially hydrolyzed cellulose acetate followed by reaction with DR 1 at $100^{\circ}C$ in pyridine. From the UV/VIS spectra of DR 1/CA adduct dissolved in DMAc solvent including phosphoglyceride before and after irradiation at 360nm and 45Onm, we found out the changes of UV/VIS spectra were reversible. In addition, the change of UV/VIS spectra of this adduct solution was strongly depended on the sorts of solvents and temperature. As the temperature was increased, UV/VIS spectra of this adduct solution in DMF showed blue shift. These results provided this solution could be applied to a temperature sensor. In the thick film case, we also obtained similar results with solution case. LB monolayer and trilayer from DR 1/CA adduct was obtained by scattering the solution including phosphoglyceride on water surface at the surface pressure of 8mN/m. After irradiation on that LB monolayer and trilayer, the reversible photoisomerization was also detected. From these results we concluded DR 1/CA adduct was suitable for the application to data storage and optical switch, etc.

• 분석과학
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• 제15권2호
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• pp.97-101
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• 2002

Co(II)착물들을 세자리 Schiff base-NOIPH, 네자리 Schiff base-$NOTDH_2$ 및 $TNBPH_4$ 로부터 합성하였으며, 이 착물들의 산화-환원 과정 mecanism을 지지 전해질로서 0.1 M TBAP를 포함한 DMF용액에서 작업전극으로 유리질 탄소전극을 사용하여 순환 전압-전류법과 펄스 차이 전압-전류법에 의해서 알아 보았다. [Co(II)$(NOIP)_2$]와 [Co(II)(NOTD)$(H_2O)_2$] 착물의 환원은 Co(III)/Co(II)의 반응이 비가역적으로 진행되고 Co(II)/Co(I)의 반응이 준가역적으로 진행되는 일전자의 2단계반응이 확산 지배적으로 일어났다. 반면에 [$Co(II)_2$(TNBP)] 착물의 환원반응은 $Co(II)_2$가 Co(II)/Co(I)로 진행되는 준가역적이며 일전자 일단계의 반응이 확산지배적으로 일어났다.

• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1381-1385
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• 2006

Cobalt (cyclam) complex has been successfully immobilized onto SBA-15, and proven to be an active catalyst for the epoxidation of styrene with tert-butyl hydroperoxide as a terminal oxidant. The selectivity for styrene oxide was observed to be up to 66% with 40% styrene conversion after 12h reaction time. The reversible redox cycle between Co(III) and Co(II) couple which was supposed to play key role during the epoxidation reaction was supported by a cyclic voltametry analysis. The textural properties of the catalyst was characterized by XRD, N2 adsorption-desorption, and TEM analysis.

• Bulletin of the Korean Chemical Society
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• 제29권6호
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• pp.1121-1124
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• 2008

A carbon composite was synthesized by mechanical mixing of ball-milled graphite and PVC powders, followed by pyrolysis reaction of PVC. Natural graphite ball milled under atmosphere of argon or air leads to a disordered structure. It appears that the electrochemical lithium intercalation reaction is dependent on the atmosphere in which the graphite is ball milled. The carbon composite obtained using air-milled graphite shows a high reversible capacity and high initial coulombic efficiency compared to argon-milled graphite. This is attributed to the enhanced thermal stability of a disordered structure in the air milled sample. For the one with air-milled graphite, the disordered structure is maintained during heat treatment, while argon-milled graphite is partially crystallized.

• Macromolecular Research
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• 제15권1호
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• pp.31-38
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• 2007

Pentamethylcyclopentadienyltitanium trichloride, bis(cyclopentadienyl)titanium dichloride ($Cp_2TiCl_2$), and bis(pentamethylcyclopentadienyl)titanium dichloride were used in the polymerization of styrene without the aid of Group I-III cocatalysts. The properties of the resulting polymer indicated that polymerization was more controlled than in thermal polymerization. The kinetic studies indicated that a lower level of termination is present and that the polymer chain can be extended by adding an additional monomer. To elucidate the mechanism of polymerization, a series of experiments was performed. All results supported the involvement of a radical mechanism in the polymerization using $Cp_2TiCl_2$. The possibility of atom transfer radical polymerization (ATRP) mechanism was investigated by isolating the intermediate species. We could confirm the activation step from the reaction of 1-PEC1 with $Cp_2TiCl$ by detecting the coupling product of the generated active radicals. However, the reversible deactivation reaction competes with other side reactions, and it detection was difficult with our model system.