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Photobiocatalytic hydrogen production in a photoelectrochemical cell
Hyunku Joo,Jaekyung Yoon 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.5
this study the photobiocatalytic hydrogen production system was photoelectrochemically examined.fer from photocatalyst to enzyme in the absence of electron relay was a rate-determining step; the enzyme was de-activated by iradiated light (half after 10 days); physical properties (crystallinity, specific surface area, pore volumeand radius) of the photocatalysts, obtained by two preparation methods (sol-gel and hydrothermal), were seldom cor-related with the production rate; chemical properties were postulated to have been affected; and each material neededdiferent reaction conditions such as pH and temperature. For the later salt-bridged system, the I-V relation for eachprepared photocatalyst was measured (Vfb in the range of ca. 0.9~ oc close to 1.1 V vs. Ag/AgCl in saturatedKCl). The change in the amount of evolved hydrogen was also independently checked according to external bias (criticalbias around 1.0 V). Then both reaction components were connected through a salt bridge to initiate light-induced hy-drogen production for the hybrid system. The H2 production exhibited an exponential trend and the Tris-HCl bufershowed the highest rate. A feasible reaction pathway was proposed.
Hyunku Joo,Kyoungmo Koo,Jaekyung Yoon,이창하 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.5
The autothermal reforming of methane to syngas for use in the Fischer-Tropsch synthesis was studied in this work over PdO containing various combinations of CeO2, BaO or SrO in a washcoated form on a metallic monolith at atmospheric pressure. This study focused on the autothermal operation of the system, in which an electric heater inside the reactor was used only to reach the ignition temperature, and thereafter the autothermal reaction successfully sustained itself without any external heat source. It was concluded from the experiments that the PdO/Al2O3 catalyst was better than the others, except for PdO-CeO2-BaO-SrO/Al2O3, which showed similar performance in terms of the CH4 conversion and H2+CO selectivity, while affording a higher H2/CO ratio (close to ca. 3) than the PdO/Al2O3 catalyst did (close to ca. 2). The gas hourly space velocity and O2/CH4 ratio governed the methane conversion, while the H2O/ CH4 ratio controlled the H2/CO ratio. A methane conversion of ~87%, H2+CO selectivity of ~94%, H2/CO ratio of ≤2.9, and M factor ≅2.15 were obtained under the conditions of a gas hourly space velocity (GHSV) of 120,000 h−1, O2/CH4=0.6 and H2O/CH4=0.5.
A simple technique to determine quantum yield for UV photocatalytic decomposition studies
Hyunku Joo 한국화학공학회 2006 Korean Journal of Chemical Engineering Vol.23 No.6
ysis is addressed. The amount of photons absorbed by coated photocatalyst was obtained with a portable radiometer,optical fiber (diameter 1 m) and a purpose-built, fabricated accessory, as well as converted isopropyl alcohol, as theprobe substance, with gas chromatography and a designed reactor system which determined a first order rate constant.Quantum yield was calculated under the asumptions that all the irradiated photons from one end of the fiber wereeither absorbed by the photocatalyst or transmitted to the other end and that the peak wavelength of the spectrum oflysts were in the range of 10-30% under specified reaction conditions of initial isopropyl alcohol concentration of 240volume ppm, coated length of 10 cm, and initial transmitted light intensity of 20-25W/cm2.
내구도가 낮은 스토리지 클래스 메모리를 위한 블록 교환 마모도 균등화 기법
이현구 ( Hyunku Lee ),이한나 ( Hanna Lee ),엄영익 ( Youngik Eom ) 한국정보처리학회 2013 한국정보처리학회 학술대회논문집 Vol.20 No.2
현재 차세대 메모리로 불리는 스토리지 클래스 메모리는 빠른 속도, 비휘발성, 바이트 단위 데이터 접근 등의 장점으로 많은 관심을 갖고 있다. 스토리지 클래스 메모리중 하나인 PCM(PhaseChange Memory)은 높은 집적도로 현재 상용화 단계이나 낮은 내구도를 지니고 있어 이를 해결하기 위한 마모도 균등화 기법이 필수적으로 요구된다. 본 논문에서는 마모도 균등화 기법들의 비교 및 분석을 통해 현존하는 마모도 균등화 기법들의 한계를 알아보고 이를 극복하기 위한 새로운 블록 교환 마모도 균등화 기법을 소개한다.
쉴드 TBM의 장비 형상 및 굴진 데이터를 고려한 체적손실 산정 연구
박현구(Hyunku Park),장석부(Seokbue Chang),이승복(Seungbok Lee) 한국암반공학회 2015 터널과지하공간 Vol.25 No.5
본 논문에서는 쉴드 TBM 굴진 중 체적손실 산정과 관련한 기존 사례 및 정량적인 산정 방안에 대한 문헌 분석을 수행하여 장비 형상과 운전 중 주요 기계데이터를 활용한 산정 방안을 도출하였다. 도출된 방안은 기존 문헌에 보고된 토압식 및 이수식 TBM 굴진 사례 분석에 적용되었다. 전반적으로 계측 결과와 잘 부합하는 것으로 나타났으며 일부 차이에 대한 분석을 실시하였다. Estimation of shield TBM tunnelling-induced volume loss is of great importance for ground settlement control. This study proposed a simple method for evaluation of volume loss during TBM tunnlling, which is able to take into account of shield machine configurations and main driving data in calculation. The method was applied to analyze the tunnelling cases with earth pressure balanced and slurry pressure balanced shiled TBM, and mostly, reasonable agreements with monitoring results were found. Additional discussions were made for some disagreements.
스토리지 클래스 메모리 기반 파일시스템의 일관성 유지 기법 비교 및 분석
이현구 ( Hyunku Lee ),김정훈 ( Junghoon Kim ),엄영익 ( Youngik Eom ) 한국정보처리학회 2014 한국정보처리학회 학술대회논문집 Vol.21 No.1
최근 기존 스토리지의 물리적 한계를 극복하기 위해 차세대 스토리지로 불리는 스토리지 클래스 메모리(SCM)의 연구 및 개발이 활발히 진행되고 있다. 이러한 SCM의 장점을 활용하기 위한 SCM 전용 파일 시스템 또한 많은 연구가 되고 있다. 하지만, 현재까지 연구되어온 SCM 전용 파일 시스템은 빠른 속도에만 중점을 두어 부분적인 일관성 지원 또는 특정한 환경에서의 시스템 성능 저하 등의 문제 요인이 있다. 본 논문에서는 SCM과 SCM 전용 파일 시스템을 알아보고 일관성 유지 기법의 비교 및 분석을 통하여 현재까지 연구된 일관성 유지 기법의 문제점을 파악하고 SCM에 최적화된 새로운 일관성 유지 기법의 방향을 모색한다.
컨셉 단계 유성기어 소음 개발을 위한 pRMC 프로그램 개발 및 적용에 관한 연구
이현구(Hyunku Lee),김무석(Moosuk Kim),이상화(Sanghwa Lee),서현승(Hyunsueng Suh),백상범(Sangbum Baek),칼만아멧(Ahmat Kahraman) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
To predict the optimized planetary gear sets that have quite gear noise in early design stage, Planetary Run Many Cases(here after pRMC) program which is using the combination analysis method of all gear specifications to find out the best planetary gear specification is developed. The pRMC is composed of 5 steps, generate, setting, evaluate, combine and analysis and been also capable of analyzing any number of simple, compound or complex-compound planetary gear set. After calculating of all candidate gear sets, pRMC could show some results likewise transmission errors, sum of forces, contact ratios and so on. By using the pRMC, the best planetary gear sets which have low noise level could be developed easily and successfully in the new automatic transmissions and others.