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Introduction of virtual open chamber for testing a weather modification technique in Korea
J-W Cha,K-H Chang,M-J Lee,J-Y Jeong,J-W Jung,H-Y Yang,K-L Kim,Y-C Kim,C-H Kim,K-H Nam,M-K Suk,C-K Jung,H-Y Go,J-H Chae,G-W Lee,Y-H Cho,S-H Jung,H-M Park,Y-A Oh,J-Y Jung,B-G Kim,Y-J Kim,M-H Choi,S-D Ki 한국기상학회 2009 한국기상학회 학술대회 논문집 Vol.2009 No.4
Jung, K.W.,Kim, D.H.,Kim, H.W.,Shin, H.S. Pergamon Press ; Elsevier Science Ltd 2011 International journal of hydrogen energy Vol.36 No.16
In the present work, a combined (acid + thermal) pretreatment was applied for the enhanced fermentative H<SUB>2</SUB> production (FHP) from Laminaria japonica. Various pretreatment conditions including HCl concentrations, heating temperatures, and reaction times were optimized via response surface methodology (RSM) with a Box-Behnken design (BBD). Through regression analysis, it was found that H<SUB>2</SUB> yield was well fitted by a quadratic polynomial equation (R<SUP>2</SUP> = 0.97), and the HCl concentration was the most significant factor influencing FHP. The desirable pretreatment conditions found were HCl concentration of 4.8%, temperature of 93 <SUP>o</SUP>C, and reaction time of 23 min, under which H<SUB>2</SUB> yield reached to 159.6 mL H<SUB>2</SUB>/g dry cell weight (dcw). The main organic acids produced were acetic and butyric acids that related closely with H<SUB>2</SUB> production. The concentration of hydroxymethylfurfural (HMF), a byproduct formed during the pretreatment process, showed an inverse relationship with H<SUB>2</SUB> yield, indicating that pretreatment conditions for the H<SUB>2</SUB> production from L. japonica were successfully optimized, by increasing the hydrolysis rate of the feedstock and also reducing the formation of HMF.
Jung, K.W.,Moon, C.,Cho, S.K.,Kim, S.H.,Shin, H.S.,Kim, D.H. Elsevier Applied Science 2013 Bioresource technology Vol.139 No.-
In this study, a two-stage system converting organic solid waste (food waste+sewage sludge) to H<SUB>2</SUB> and CH<SUB>4</SUB> was operated. In the first stage of dark fermentative hydrogen production (DFHP), a recently proposed method that does not require external inoculum, was applied. In the second stage, anaerobic sequencing batch reactor (ASBR) and an up-flow anaerobic sludge blanket reactor (UASBr) were followed to treat H<SUB>2</SUB> fermenter effluent. (H<SUB>2</SUB>+CH<SUB>4</SUB>-ASBR) system showed better performance in terms of total biogas conversion (78.6%), while higher biogas production rate (2.03L H<SUB>2</SUB>/L<SUB>system</SUB>/d, 1.96L CH<SUB>4</SUB>/L<SUB>system</SUB>/d) was achieved in (H<SUB>2</SUB>+CH<SUB>4</SUB>-UASBr) system. To reduce the alkali addition requirement in DFHP process, CH<SUB>4</SUB> fermenter effluent was tested as a diluting water. Both the ASBR and UASBr effluent was effective to keep the pH above 6 without CH<SUB>4</SUB> production. In case of using ASBR effluent, H<SUB>2</SUB> production dropped by 15%, but alkali addition requirement was reduced by 50%.
Cu 기판위에 성장한 MgO, MgAl₂O₄와 MgAl₂O₄/MgO 박막의 집속이온빔을 이용한 스퍼터링수율 측정과 이차전자방출계수 측정
정강원(K. W. Jung),이혜정(H. J. Lee),정원희(W. H. Jung),오현주(H. J. Oh),박철우(C. W. Park),최은하(E. H. Choi),서윤호(Y. H. Seo),강승언(S. O. Kang) 한국진공학회(ASCT) 2006 Applied Science and Convergence Technology Vol.15 No.4
MgAl₂O₄ 막은 MgO 보호막 보다 단단하며 수분 흡착 오염문제에 상당히 강한 특성을 가진다. 본 연구에서 AC-PDP의 유전체보호막으로 사용되는 MgO 보호막의 특성을 개선하기 위해 MgAl₂O₄/MgO 이중층 보호막을 제작하여 특성을 조사하였다. 전자빔 증착기를 사용하여 Cu 기판에 MgO와 MgAl₂O₄을 각각 1000 Å 두께로 증착, MgAl₂O₄/MgO을 200/800 Å 두께로 적층 증착 후, 이온빔에 의한 충전현상을 제거하기 위해 Al을 1000 Å 두께로 증착하였다. 집속 이온빔(focused ion beam ; FIB)장치를 이용하여 10 ㎸에서 14 ㎸까지 이온빔 에너지에 따라 MgO는 0.364 ~ 0.449 값의 스퍼터링 수율에서 MgAl₂O₄/MgO을 적층함으로 24 ~ 30 % 낮아진 0.244 ~ 0.357 값의 스퍼터링 수율이 측정되었으며, MgAl₂O₄는 가장 낮은 0.088 ~ 0.109 값의 스퍼터링 수율이 측정되었다. g-집속이온빔(g-FIB)장치를 이용하여 Ne? 이온 에너지를 50 V에서 200 V까지 변화 시켜 MgAl₂O₄/MgO와 MgO는 0.09 ~ 0.12의 비슷한 이차전자방출 계수를 측정 하였다. AC-PDP셀의 72시간 열화실험 후 SEM 및 AFM으로 열화된 보호막의 표면을 관찰하여 기존의 단일 MgO 보호막과 MgAl₂O₄/MgO의 적층보호막의 열화특성을 살펴보았다. It is known that MgAl₂O₄ has higher resistance to moisture than MgO, in humid ambient MgO is chemically unstable. It reacts very easily with moisture in the air. In this study, the characteristic of MgAl₂O₄ and MgAl₂O₄/MgO layers as dielectric protection layers for AC-PDP (Plasma Display Panel) have been investigated and analysed in comparison for conventional MgO layers. MgO and MgAl₂O₄ films both with a thickness of 1000 Å and MgAl₂O₄/MgO film with a thickness of 200/800 Å were grown on the Cu substrates using the electron beam evaporation. 1000 Å thick aluminium layers were deposited on the protective layes in order to avoid the charging effect of Ga? ion beam while the focused ion beam(FIB)is being used. We obtained sputtering yieds for the MgO, MgAl₂O₄ and MgAl₂O₄/MgO films using the FIB system. MgAl₂O₄/MgO protective layers have been found th show 24 ~ 30% lower sputtering yield values from 0.244 up to 0.357 than MgO layers with the values from 0.364 up to 0.449 for irradiated Ga? ion beam with energies ranged from 10 ㎸ to 14 ㎸. And MgAl₂O₄ layers have been found to show lowest sputtering yield values from 0.88 up to 0.109. Secondary electron emission coefficient(g) using the γ-FIB. MgAl₂O₄/MgO and MgO have been found to have similar g values from 0.09 up to 0.12 for indicated Ne+ ion with energies ranged from 50 V to 200 V. Observed images for the surfaces of MgO and MgAl₂O₄/MgO protective layers, after discharge degradation process for 72 hours by SEM and AFM. It is found that MgAl₂O₄/MgO protective layer has superior hardness and degradation resistance properties to MgO protective layer.
Jung, K.W.,Cho, S.K.,Yun, Y.M.,Shin, H.S.,Kim, D.H. Pergamon Press ; Elsevier Science Ltd 2013 International journal of hydrogen energy Vol.38 No.22
Application of an up-flow anaerobic sludge blanket (UASB) reactor to dark fermentative H<SUB>2</SUB> production greatly improves H<SUB>2</SUB> productivity due to the maintenance of high biomass concentration. However, a long start-up HRT and start-up period are required to develop the H<SUB>2</SUB>-producing granules (HPGs) and to avoid washing out the suspended sludge at the start of the process. In the present work, a novel strategy to rapidly form HPGs was developed in UASB reactor. To induce highly active mass transfer in the UASB reactor, a high recirculation rate (15 times the influent) was adopted over 10 days, then recirculation was stopped. As the operation progressed, self-flocculation took place and HPGs developed after 90 h of operation. A stable production of H<SUB>2</SUB> was observed after 20 days of operation. The thickness of the HPGs layer in the sole UASB reactor increased progressively, and consequently the average HPG diameter and concentration were 1.86 mm (0.1-3.9 mm) and 52 g/L, respectively, after 60 days of operation. These findings seem to suggest that high-rate recirculation plays a crucial role in accelerating the formation of HPGs in such UASB reactors through high up-flow velocity, providing active mass transfer.
Glass / p μc-Si:H 특성에 따른 i μc-Si:H 층 및 태양전지 특성변화 분석
장지훈(Jang, J.H.),이지은(Lee, J.E.),김영진(Kim, Y.J.),정진원(Jung, J.W.),박상현(Park, S.H,),조준식(Cho, J.S.),윤경훈(Yoon, K.H.),송진수(Song, J.),박해웅(Park, H.W.),이정철(Lee, J.C.) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06
PECVD를 이용하여 제조된 미세결정질 p-i-n 실리콘 박막 태양전지에서, p 층은 태양전지의 윈도우 역할 및 그 위에 증착될 i {mu}c-Si:H 층의 'seed'층 역할을 수행하기 때문에, p층의 구조적 및 전기적, 광학적 특성은 태양전지의 전체 성능에 큰 영향을 미칠 수 있다. 본 연구에서는 SiH₄ 농도를 변화시켜 각기 다른 결정 특성을 갖는 p {mu}c-Si:H층을 제조하고 그 위에 i {mu}c-Si:H 층을 증착하여 p층의 결정 특성변화와 그에 따른 i {mu}c-Si:H 층 및 'superstrate' p-i-n 미세결정질 실리콘 박막 태양전지의 특성 변화를 조사하였다. P층의 경우, SiH₄ 농도가 증가함에 따라 결정분율 (Xc)이 감소하여 비정질화되었으며 그에 따라 dark conductivity가 감소하는 경향을 나타내었다. 각기 다른 결정분율을 가지는 p 'seed' 층 위에 증착된 태양전지는, p 'seed' 층의 결정분율이 증가함에 따라 개방전압, 곡선인자, 변환효율이 경향적으로 감소하였다. 이는 p 층 결정분율 변화에 따른 p/i 계면특성 저하 및 그 위에 증착되는 i {mu}c-Si:H 층의 결함밀도 증가 등에 따른 태양전지 특성 감소 때문인 것으로 판단되며, 이를 분석하기 위하여 i {mu}c-Si:H 층의 전기적, 구조적 특성 분석 및 태양전지의 dark I-V 특성 등을 분석하고자 한다.
Jung, S.W.,Park, J.,Kwon, O.B.,Kim, Y.J.,Keel, S.I.,Yun, J.H.,Lim, I.G. Butterworths [etc.] ; Elsevier Science Ltd 2014 Fuel Vol.136 No.-
The effects of CO<SUB>2</SUB> addition on the downstream interactions of H<SUB>2</SUB>-air and CO-air premixed flames were investigated. Flame stability diagrams mapping the extinction limits for various fuel concentrations as functions of the strain rate were developed for the downstream interactions between H<SUB>2</SUB>-air and CO-air premixed flames with 0-20% CO<SUB>2</SUB> addition. Of particular concern was the impact of the chemical reactions of the additional CO<SUB>2</SUB> on the flame extinction characteristics. The results showed that CO<SUB>2</SUB> addition suppressed the flammable regions appreciably and decreased the critical strain rate, opening up the lean extinction boundary. For highly stretched interacting flames, two flammable island regions on the maps were combined into one when 10% or 20% CO<SUB>2</SUB> was added to either the H<SUB>2</SUB>-air or CO-air premixed mixtures. The chemical reactions of the additional CO<SUB>2</SUB> were significant, especially for high strain rate flames, while the effect of the radiative heat loss of the additional CO<SUB>2</SUB> was minor, even for low strain rate flames. Such chemical reactions were determined by competition between the reaction steps for the consumption and production of HCO and the reverse reaction of CO+OH=CO<SUB>2</SUB>+H with the reaction step of H+O<SUB>2</SUB>→O+OH, an indicator of the overall reaction rate for the H atoms. This resulted in a weakened interacting flame. Such chemical reactions of the additional CO<SUB>2</SUB> were examined in detail to describe the flame characteristics.
Fe-Co-W 소결체와 탄소강의 레이저 용융부 결함형성에 미치는 공정변수의 영향
김성욱(S. W. Kim),윤병현(B. H. Yoon),정우광(W. G. Jung),이창희(C. H. Lee) 한국레이저가공학회 2004 한국레이저가공학회지 Vol.7 No.3
This study was performed to clarification of the formation of weld discontinuities in the dissimilar laser fusion zone. Welding parameters were beam power of 1300, 1430, 1560, and 1700 W and travel speed of 1, 1.3, and 1.7 m/min. Most cavities in the fusion zone were observed near the tip. Cavities in the fusion zone observed to be formed and grown from pores in the tip. More cavities were formed as the beam position moves to the tip side. Small cavities were decreased but large cavities were increased when the energy input increased. W content in the fusion zone was increased with heat input and as the beam position close to the tip. In the fusion zone, W content in the dendrite boundary was increased with heat input. Considering the propagation path and fracture morphology, cracks were solidification cracking, and were initiated and propagated along the dendrite boundaries. The formation of cracks might be related with the W rich μ phase which was formed in the grain boundaries and dendrite boundaries.