• Korean Chemical Engineering Research
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• 제44권4호
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• pp.387-392
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• 2006

이온 교환법으로 (Fe, Co)/NaY, (Fe, Co)/NaBeta (Fe, Co)/HUSY 등 (Fe,Co)/zeolite 촉매를 제조하였으며, 카테콜을 합성하는 과산화수소에 의한 페놀의 수산화 반응에서 이들의 촉매 성능을 조사하였다. (Fe, Co)/NaBeta 촉매에서는 반응온도가 $70^{\circ}C$, 페놀/과산화수소(몰) 비가 3, 페놀/촉매(무게) 비가 50, 용매(물)/페놀(무게) 비가 6인 조건에서 페놀의 전환율은 22％, 수산화 반응에 대한 선택도는 77％, 카테콜에 대한 선택도는 70％, 카테콜/하이드로퀴논의 생성비는 2.5로 가장 좋은 반응 결과를 얻었다. (Fe, Co)/zeolite 촉매는 재생하여 반복 사용해도 성능이 저하되지 않았다. 반응 전후의 (Fe, Co)/zeolite 촉매를 XRD, UV-VIS DRS, XPS 등으로 조사하여, 이를 근거로 촉매 반응 결과를 해석하였다.

• Bulletin of the Korean Chemical Society
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• 제20권7호
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• pp.815-818
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• 1999

The method of calculating the excess Helmholtz free energy from the averaged effective acceptance ratio for the Lennard-Jones fluid and the inverse twelve fluid has been slightly modified and applied to the two-center-Lennard-Jones liquid. The excess Helmholtz free energy is calculated directly from the average of the modified effective acceptance ratio through a single Metropolis Monte Carlo simulation. Therefore this method does not need any reference system. The results of the present method were satisfactory compared with those of the perturbation theories and the overlap ratio method.

• Carbon letters
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• 제25권
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• pp.78-83
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• 2018

Pyrolyzed fuel oil (PFO) and coal tar was blended in the feedstock to produce pitch via thermal reaction. The blended feedstock and produced pitch were characterized to investigate the effect of the blending ratio. In the feedstock analysis, coal tar exhibited a distinct distribution in its boiling point related to the number of aromatic rings and showed higher Conradson carbon residue and aromaticity values of 26.6% and 0.67%, respectively, compared with PFO. The pitch yield changed with the blending ratio, while the softening point of the produced pitch was determined by the PFO ratio in the blends. On the other hand, the carbon yield increased with increasing coal tar ratio in the blends. This phenomenon indicated that the formation of aliphatic bridges in PFO may occur during the thermal reaction, resulting in an increased softening point. In addition, it was confirmed that the molecular weight distribution of the produced pitch was associated with the predominant feedstock in the blend.

• Macromolecular Research
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• 제12권3호
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• pp.269-275
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• 2004

To graft N-isopropylacrylamide (NIPAAm) onto alginate, varying dosages of ${\gamma}$-rays were irradiated onto alginate films in deionized water and methanol media, which are non-solvents of alginate. We investigated the hydrogels graft ratio, mechanical strength, swelling kinetics and ratio, and behavior with respect to drug release. The graft yield of NIPAAm increased upon increasing the irradiation dose. The use of the aqueous solution increased the graft yield relative to that obtained in methanol. The mechanical strength of the grafted hydrogels increased after grafting with NIPAAm. In a study of the swelling kinetics, we found that all hydrogels reached an equilibrium swollen state within 3 h. The equilibrium swelling ratio of the hydrogels decreased upon increasing the irradiation dose. The swelling ratio of the hydrogels decreased dramatically between 30 and 35$^{\circ}C$ because phase separation of NIPAAm occurred at 32$^{\circ}C$. The swelling process, with respect to the temperature change, was repeatable. An NIPAAm-grafted alginate containing a drug sustained its release rate until 3 h after an initial high drug release caused by a burst effect.

• Korean Chemical Engineering Research
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• 제49권1호
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• pp.120-127
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• 2011

친환경 복합단열재를 개발하기 위하여 천연섬유질(목재칩 및 톱밥)을 심재로, 활성황토를 결합재로 사용하였다. 물/결합재비 및 천연섬유질/결합재비를 다양하게 변화시켜 공시체를 제작하였으며, 공시체의 제 물성을 조사하기 위하여 압축 및 휨강도, 흡수성, 내열수성, 열전도도, 세공분포측정 및 SEM에 의한 미세조직 관찰을 실시하였다. 그 결과 흡수율은 천연섬유질/결합재비가 증가될수록 증가되었으나 폴리머/결합재비 증가에 따라 현저히 감소되었다. 압축 및 휨강도는 물/결합재비 및 천연섬유질/결합재비에 따라 다양한 특성을 나타내었다. 천연섬유질/결합재비 및 폴리머/결합재비가 증가됨에 따라 열전도도는 감소되었다. SEM조사에서 활성황토 결합재는 수화결정체가 잘 형성되어 치밀한 조직을 관찰할 수 있었고, 활성황토를 결합재로 사용한 시편의 총세공량은 생황토를 결합재로 사용한 시편의 총세공량에 비하여 적게 나타났다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.169-171
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• 2007

A breaking layer was introduced to conventional decal transfer method in membrane electrolyte assembly fabrication for high catalyst transfer ratio. In this study, the modified decal transfer method with high catalyst transfer ratio was introduced and its performance is studied. The structural features of electrodes made by decal method were investigated using scanning electron microscopy and current-voltage polarization measurement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.555-558
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• 2005

The purpose of this study is to evaluate the chemical resistance of polymer powder-modified mortars with special accelerator component. Polymer powder-modified mortars with the accelerator are prepared with various polymer-binder ratios, and tested for flexural and compressive strengths and mass change. Chemicals resistance was tested by dealing with $10\%$ HCl and $5\%\;H_2SO_4$ aqueous solution. As a result, the weight reduction ratio of the mortars decreased with increasing polymer-binder ratio. However, in the viewpoint of strength reduction by chemical attacks, the maximum chemical resistance of the mortars was shown at a polymer-binder ratio of $5\%$.

• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1493-1498
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• 2007

In this work, alkyl methacrylate-based microgels were synthesized by an experimental design method, and their sebum absorption characteristics were investigated. The results of fractional factorial experimentation indicated that the cross-linking agent content, solvent content, and stirring speed were the main parameters in the synthesis of the microgels. The suitable synthesis conditions were determined by the response surface design method. Through a study of the monomer and solvent effects, it was confirmed that the microgel shows the highest sebum absorption ratio when t-butyl methacrylate is used as a monomer or when acetone is used as a solvent. The optimal microgel synthesis conditions for cosmetic application were determined, and the resulting microgel had a mean particle size of 4.7 μm and a sebum absorption ratio of 435%.

• Korean Chemical Engineering Research
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• 제57권2호
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• pp.289-300
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• 2019

We have conducted a preliminary numerical analysis to understand the effects of double-diffusive convection on the molar flux at the crystal region during the growth of mercurous bromide ($Hg_2Br_2$) crystals in 1 g and microgravity (${\mu}g$) conditions. It was found that the total molar fluxes decay first-order exponentially with the aspect ratio (AR, transport length-to-width), $1{\leq}AR{\leq}10$. With increasing the aspect ratio of the horizontal enclosure from AR = 1 up to Ar = 10, the convection flow field shifts to the advective-diffusion mode and the flow structures become stable. Therefore, altering the aspect ratio of the enclosure allows one to control the effect of the double diffusive natural convection. Moreover, microgravity environments less than $10^{-2}g$ make the effect of double-diffusive natural convection much reduced so that the convection mode could be switched over the advective-diffusion mode.

• 한국추진공학회지
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• 제24권4호
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• pp.66-72
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• 2020

본 논문은 알루미늄 함량 변화에 따른 추진제의 후경화에 대한 영향성, 화학적 노화도에 관하여 기술하였다. 동일 경화조건에서 알루미늄 함량이 18 wt%인 추진제가 2 wt%인 추진제 대비 후경화 기간이 길어지는 것으로 확인하였다. 반면 후경화가 포함된 화학적 노화도 분석에서는 알루미늄 함량이 18 wt%인 추진제가 2 wt%인 추진제 대비 화학적 노화가 천천히 진행되는 것을 확인하였다.