• 한국입자에어로졸학회지
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• 제8권4호
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• pp.173-180
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• 2012

SiC particles, 8.3 ${\mu}m$ in volume average diameter, were chlorinated in an alumina tubular reactor, 2.4 cm in diameter and 32 cm in length, with reactor temperature varied from 100 to $1200^{\circ}C$. The flow rate of the gas admitted to the reactor was held constant at 300 cc/min, the mole fraction of chlorine in the gas at 0.1 and the reaction time at 4 h. The chlorination was negligibly small up to the temperature of $500^{\circ}C$. Thereafter, the degree of chlorination increased remarkably with increasing temperature until $900^{\circ}C$. As the temperature was increased further from 900 to $1200^{\circ}C$, the increments in chlorination degree were rather small. At $1200^{\circ}C$, the chlorination has nearly been completed. The surface area of the residual carbon varied with chlorination temperature in a manner similar to that with the variation of chlorination degree with temperature. The surface area at $1200^{\circ}C$ was 912 $m^{2}/g$. A simple model was developed to predict the conversion of a SiC under various conditions. A Langmuir-Hinshelwood type rate law with two rate constants was employed in the model. Assuming that the two rate constants, $k_{1}$ and $k_{2}$, can be expressed as $A_{1e}^{-E_{1}/RT}$ and $A_{2e}^{-E_{2}/RT}$, the four parameters, $A_{1}$, $E_{1}$, $A_{2}$, and $E_{2}$ were determined to be 32.0 m/min, 103,071 J/mol, 2.24 $m^{3}/mol$ and 39,526 J/mol, respectively, through regression to best fit experimental data.

• 센서학회지
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• 제3권2호
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• pp.16-23
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• 1994

오염수에서 유기인 화합물을 측정하기 위해 개발된 광섬유 바이오센서의 신호의 분석과 최적설계를 위하여 센서에 사용되어진 AChE효소(acetylcholinesterase)의 반응, 반응기 내의 유체거동 및 물질전달현상의 해석이 필요하다. 사용되어진 센서의 반응기 부분을 해석하고 재설계하기 위하여 효소 반응을 연구하고, 이동현상학적으로 유체 및 물질확산 현상을 해석하여 반응기 모델을 성립하였다. 사용되어진 유기인 화합물에 의해 저해되는 AChE효소의 측정범위인 0-2 ppm 사이에서 저해반응을 실험하였으며, 비가역 저해 효소 반응식을 제안하였다. 반응기를 두상 즉 벌크상과 효소층으로 나누어 유체거동을 해석하였으며, 고정화겔 내의 확산의 영향을 조사하였다. 반응식, 유체거동식 및 확산식을 연계하여 세워진 반응기 전체모델을 제시하였고, 이를 이용하여 신호를 해석하였다. 제시된 모델을 이용하여 효소량, 효소층의 두께의 증가에 따른 센서 신호량의 민감도를 전산모사하였다.

• Korean Chemical Engineering Research
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• 제58권4호
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• pp.665-674
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• 2020

외부순환형 공기부양반응기에서 낮은 주파수의 압력 변동에 대해 연구하였다. 상승관과 하강관의 상부와 하부에 설치된 내압관의 액면을 휴대폰으로 촬영하는 방법으로 빠른 주파수의 변동이 제거된 압력을 측정하였다. 자기상관함수와 교차상관함수의 계산을 통해 압력의 주기적인 변동을 확인하였다. 기체속도가 일정하여도 순환액체의 관성으로 인해 압력은 물론이고 상승관과 하강관내의 기체체류량도 주기적으로 변동하였다. 일반적으로 기체유속이 증가할수록 압력 변동의 강도는 커졌다. 비분산 액체높이가 0.04 m일 때 압력 변동의 주기는 기체속도가 0.14 ms^-1에서 극대값을 보여주었다. 이는 기체속도가 커질수록 순환 액체속도의 증가율은 둔화하고 효과적으로 순환하는 액체의 부피가 감소하므로 순환액체의 관성이 극대값을 보이기 때문이다.

• 한국결정성장학회지
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• 제12권4호
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• pp.215-221
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• 2002

$SiH_2Cl_2/H_2$ 기체혼합물을 원료로 사용하여 (100) Si 기판 위에 고온벽 화학기상증착법(hot-wall CVD)으로 에피 실리콘을 증착시켰다. 공정변수(증착온도, 반응기 압력, 입력 기체의 조성비($H_2/SiH_2Cl_2$)등)가 실리콘 증착에 미치는 영향을 조사하기 위해 열화학적 전산모사를 수행하였으며, 전산모사를 통해 얻은 공정조건의 범위를 바탕으로 실험한 결과, 전산모사의 결과와 실험이 잘 일치함을 알 수 있었다. 실험을 통해 얻은 최적 증착 조건은 증착온도가 850~$950^{\circ}C$, 반응기 압력은 2~5 Torr, $H_2/SiH_2Cl_2$비는 30~70 정도임을 알 수 있었고, 증착된 에피 실피콘은 두께 및 비저항의 균일도가 우수하고 불순물 함량이 낮은 양질의 박막임을 확인할 수 있었다.

• Nuclear Engineering and Technology
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• 제52권6호
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• pp.1304-1317
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• 2020

The tubes in a heat exchanger, such as a steam generator (SG), are subjected to crossflow, and interaction between tubes and supports can happen, which can cause fretting wear of tubes. Although many experiments and models have been established, some detailed mechanisms are still not sufficiently clear. In this work, more attention is paid to obtain the regulation of impact and sliding in the complex process and many factors, such as excitation forces and clearances. The responses and contact forces were analyzed to obtain clear understanding of the influences of these factors. Room temperature tests in the air were established. The results show that the effect of clearance on the normal work rate is not monotonous and instead has two peaks. The force ratio can influence the normal work rate by changing the distribution of contact angles, which can result in higher sliding in the contact process. Fretting wear tests are conducted, and the wear surfaces are analyzed by a scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX). The results of this work can serve as a reference for impactsliding contact analysis between AVBs and tubes in steam generators.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.344-351
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• 2020

AgInCd alloy is widely used as neutron absorber in nuclear reactors. However, the AgInCd control rods may fail during service due to the irradiation swelling. In the present study, a calculational method is proposed to calculate the composition change of the AgInCd absorber. Calculated results show that neutron fluence has significant impact on the chemical compositions. Ag and In contents gradually decrease while Cd and Sn conversely increases from the center to the rim of AgInCd absorber due to the depression of neutron flux. The composition change at the surface is higher almost two times than that at the center. Based on the calculated compositions, six simulated AgInCdSn alloys were prepared and examined. With the increase of Cd and Sn, the simulated AgInCdSn alloys transform from a single fcc phase into the mixed fcc and hcp phases, and finally into the single hcp phase. The atomic volume of the hcp phase is obviously larger than the fcc phase. The fcc-hcp transformation results in considerable volume swelling of the AgInCd absorber. Moreover, the lattice parameters of the fcc and hcp phases gradually increase with Cd and Sn contents, which also can induce small volume swelling.

• 한국물환경학회지
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• 제21권4호
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• pp.337-346
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• 2005

An MSBR using a membrane for not only filtration but also aeration (MA-MSBR) was designed to reduce membrane fouling and to enhance water quality, and compared with an MSBR using a membrane for only filtration (BA-MSBR). COD removal efficiency of the MA-MSBR was similar to that of the BA-MSBR, but membrane performance of the MA-MSBR was better than that of the BA-MSBR. The MA-MSBR had more small particles in mixed liquor, so the specific cake resistance of flocs in the MA-MSBR was higher than that in the BA-MSBR. However, in the aerobic reaction step of the MA-MSBR, air went through membrane pores and out of the membrane surface, so cake layers on the membrane surface and a portion of organics adsorbed on membrane pores could be removed periodically. Therefore, cake resistance, $R_c$, and fouling resistance by adsorption and blocking, $R_f$, for the MA-MSBR increased more slowly than those for the BA-MSBR. Additionally, in order to compare the energy efficiency for two MSBRs, oxygen transfer efficiency and power to supply air into the reactor by a membrane module and a bubble stone diffuser were measured using deionized water. From these measurements, the transferred oxygen amount per unit energy was calculated, resulting that of MA-MSBR was slightly higher than that of BA-MSBR.

• 한국응용과학기술학회지
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• 제28권3호
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• pp.321-328
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• 2011

The autothermal reforming reaction of methane was investigated to produce hyd rogen with Ni/$CeO_2-ZrO_2$, Ni/$Al_2O_3$-MgO and Ni-Ru/$Al_2O_3$-MgO catalysts. Honeycomb metalli c monolith was applied in order to obtain high catalytic activity and stability in autothermal r eforming. The catalysts were characterized by XRD, BET and SEM. The influence of various catalysts on hydrogen production was studied for the feed ratio($O_2/CH_4$, $H_2O/CH_4$). The $O_2/CH_4$ and $H_2O/CH_4$ ratio governed the methane conversion and temperature profile of reactor. Th e reactor temperature increased as the reaction shifted from endothermic to exothermic reactio n with increasing $O_2/CH_4$ ratio. Among the catalysts used in the experiment, the Ni-Ru/$Al_2O_3$-MgO catalyst showed the highest activity. The 60% of $CH_4$ conversion was obtained, and th e reactor temperature was maintained $600^{\circ}C$ at the condition of GHSV=$10000h^{-1}$ and feed ratio S/C/O=0.5/1/0.5.

• 대한기계학회논문집B
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• 제35권12호
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• pp.1257-1264
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• 2011

희박예혼합 가스터빈 연소기에 대한 3 차원 RANS 해석을 수행하였으며 PCFM(Partially Premixed Coherent Flame Model) 화염면적밀도 생성항 상수의 보정을 통하여 희박연소조건을 모사하였다. PCFM 에서 계산된 화염면적밀도에 의해 층류 예혼합 화염의 전파를 예측하고 불균일하게 분포한 기연 가스의 물성을 평형 가정에 따라 예측하였다. 복사와 대류 열전달을 모사하기 위해 냉각 조건으로서 실험과의 비교를 통해 결정된 열유속을 적용하였다. 이러한 3 차원 해석 결과를 바탕으로 파일럿 노즐과 메인 노즐에 분배되는 연료량 비에 대한 민감도 조사를 수행하였으며 CRN(Chemical Reactor Network)을 구성하여 NOx 배출량을 예측하고 측정값과 비교 분석하였다.

• Korean Chemical Engineering Research
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• 제55권1호
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• pp.86-92
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• 2017

석탄 화력발전 연소 배가스에 포함된 이산화탄소를 염수의 전기분해를 통해 얻어진 가성소다와 반응시켜 중탄산나트륨, 염소, 수소 등을 생산하는 공정에 대하여 실험과 전산모사를 병행하였다. Bench 규모 공정을 디자인하여 가성소다에 의한 이산화탄소 전환 공정에 대하여 실험하였고 같은 공정을 공정 모델링을 통해 전산모사 하였다. 실험결과와 전산모사 결과의 비교를 통해 모델의 신뢰성을 확인하였고, 상용급 공정에 대한 모델링을 수행하였다. 상용급 공정에 대한 열 및 물질수지를 계산하였고 반응기내 온도분포와 $CO_2$ 흡수율을 도출하였다. 본 연구를 통해 온실가스 저감뿐만 아니라 $CO_2$ 전환을 통한 경제성까지 갖춘 본 공정에 대한 기술 신뢰성을 확보할 수 있을 것이다.