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Daejeon, South Korea

Jung J.Y.,Gyeongsang National University | Jo J.S.,Gyeongnam National University of Science and Technology | Kim Y.W.,Korea Research Institute of Chemical Technology | Yoon B.T.,Korea Research Institute of Chemical Technology | And 2 more authors.
Journal of the Korean Wood Science and Technology | Year: 2013

The steam explosion-chemical pretreatment is a more effective wood pretreatment technique than the conventional physical pretreatment by accelerating reactions during the pretreatment process. In this paper, two-stage pretreatment processes of hardwood were investigated for its enzymatic hydrolysis and the succinic acid yield from the pretreated solid. The first stage pretreatment was performed under conditions of low severity to optimize the amount of solid recovery. In the second stage pretreatment washed solid material from the first stage pretreatment step was impregnated again with chemical (alkaline or chlorine-based chemicals) to remove a portion of the lignin, and to make the cellulose more accessible to enzymatic attack. The effects of pretreatment were assessed by enzymatic hydrolysis and fermentation, after the two stage pretreatments. Maximum succinic acid yield (16.1 g L -1 and 77.5%) was obtained when the two stage pretreatments were performed at steam explosion -3% KOH. Source

Kim M.S.,Korea Advanced Institute of Science and Technology | Kim M.S.,SK Energy Institute of Technology | Chalapathy R.B.V.,Korea Advanced Institute of Science and Technology | Yoon K.H.,Korea Institute of Energy Research | Ahn B.T.,Korea Advanced Institute of Science and Technology
Journal of the Electrochemical Society | Year: 2010

A precursor layer for Cu(In0.7Ga0.3)Se2 (CIGS) was deposited by simultaneous sputtering of Cu40In 60 and Cu50Ga50 and subsequent sputtering of Cu2Se. The Cu2Se/metal alloy-stacked precursor was selenized at 550°C in a Se vapor atmosphere to grow a CIGS film. The thickness of the Cu2Se layer was varied to control the Cu/ (In+Ga) ratio and to study the grain growth behavior. A CIGS film with large grains can be achieved when the overall Cu/ (In+Ga) ratio was above 0.92. With the existence of the Cu2Se layer, the Ga concentration was very low near the surface and it was accumulated near the CIGS/Mo interface. Also, the In concentration was very low near the CIGS/Mo interface. As a result, the CuInSe2 phase was formed at the surface and the CuGaSe2 phase was formed near the CIGS/Mo interface. The open-circuit voltage and fill factor were greatly reduced by the Ga segregation. Further supply of Ga on the selenized CIGS film reduced Ga segregation and improved the cell efficiency. © 2009 The Electrochemical Society. Source

Ryu J.-H.,Dongguk University | Kim T.-J.,SK Energy Institute of Technology | Lee T.-Y.,Pohang University of Science and Technology | Lee I.-B.,Pohang University of Science and Technology
Journal of the Taiwan Institute of Chemical Engineers | Year: 2010

Wastewater treatment is an important issue in the era when water resources are continuously decreasing world-wide in the face of increasing demand. The need for cheap and energy efficient wastewater utilization technologies is thus drawing continuous attention. Capacitive Deionization (CDI) was recently proposed as a novel alternative replacing for the conventional membrane methodologies. This paper is concerned with simulation of the separating saline from the wastewater effectively using CDI. After actual experiments of CDI to assess their basic behaviors, their behaviors are mathematically formulated and its associated parameters are identified accordingly. The corresponding model is implemented in Matlab simulink to show how it can be operated in preparation for the wider applications. The proposed simulation framework could be further expanded to evaluate the performance in terms of economical feasibility against other separation methods. © 2010 Taiwan Institute of Chemical Engineers. Source

Hur M.,Korea University | Hur M.,BNF Technology Inc. | Yeo I.,Korea Basic Science Institute | Park E.,Korea Basic Science Institute | And 6 more authors.
Analytical Chemistry | Year: 2010

Complex petroleum mass spectra obtained by Fouriertransform ion cyclotron resonance mass spectrometry (FTICR MS) were successfully interpreted at the molecular level by applying principle component analysis (PCA) and hierarchical clustering analysis (HCA). A total of 40 mass spectra were obtained from 20 crude oil samples using both positive and negative atmospheric pressure photoionization (APPI). Approximately 400 000 peaks were identified at the molecular level. Conventional data analyses would have been impractical with so much data. However, PCA grouped samples into score plots based on their molecular composition. In this way, the overall compositional difference between samples could be easily displayed and identified by comparing score and loading plots. HCA was also performed to group and compare samples based on selected peaks that had been grouped by PCA. Subsequent heat map analyses revealed detailed compositional differences among grouped samples. This study demonstrates a promising new approach for studying multiple, complex petroleum samples at the molecular level. © 2010 American Chemical Society. Source

Ahmed A.,Kyungpook National University | Cho Y.J.,Kyungpook National University | No M.-H.,SK Energy Institute of Technology | Koh J.,SK Energy Institute of Technology | And 4 more authors.
Analytical Chemistry | Year: 2011

The various components of crude oil were structurally resolved using an atmospheric-pressure solids analysis probe (ASAP) coupled with ion mobility mass spectrometry (IM-MS). An ASAP source was used to broadly fractionate compounds according to their boiling points, thereby simplifying the resulting mass spectra for easier data interpretation. The m/z-mobility plots obtained by IM-MS analysis of crude oil could be used to find the structural relationship between crude oil molecules. That was demonstrated using ion mobility mass spectra from a homologous series of compounds, differing only by the number of alkyl units, found in crude oil. The peaks from this series were linearly aligned in the plot, suggesting a continuous increase of the collisional cross section with an increase of mass values and hence the absence of significant structural differences within the series. In contrast, peaks in a homologous series differing only in the number of pendant hydrogen atoms were not linearly aligned, suggesting a discontinuous increase of the collisional cross section with an increase of mass values and hence significant structural differences due to the addition or removal of hydrogen. Cases in which a slope change was observed at three- or four-peak intervals may be related to the addition of an aromatic ring to existing structures. Overall, ion mobility mass spectrometry demonstrates a useful tool that can be used to elucidate structural relationships between molecules comprising crude oil. © 2010 American Chemical Society. Source

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