Yuseong Gu, South Korea
Yuseong Gu, South Korea

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Yu H.-C.,Yonsei University | Kumar S.V.,Yonsei University | Song Y.-K.,Yonsei University | Choi J.,University of Tokyo | And 4 more authors.
Macromolecular Research | Year: 2011

Nanopore generation could be accomplished in thin films of fully alicyclic polyimides derived from an alicyclic dianhydride and diamines. A silylation method for the alicyclic diamines was used to synthesize high molecular weight alicyclic polyimides. Triblock copolyimides were prepared using N-silylated alicyclic diamines, alicyclic dianhydride, and a thermally labile polymer. Nanoporous films of fully alicyclic polyimides were prepared through heating of the copolyimide films to induce thermal degradation of the labile block. © 2011 The Polymer Society of Korea and Springer Netherlands.


Nam H.-S.,Hanwha Chemical R and nter | Nam H.-S.,KAIST | Yoon J.-K.,Hanbat National University | Ko J.M.,Hanbat National University | Kim J.-D.,KAIST
Materials Chemistry and Physics | Year: 2010

Nanostructured manganese dioxide, MnO2, was synthesized by a sonochemical method. Nanostructured MnO2 had the shapes of flower-like and nanowires by changing the pH in the aqueous solution, as observed via scanning electron microscopy and transmission electron microscopy. The electrochemical capacitance was studied by cyclic voltammetry. A maximum specific capacitance of 300 Fg-1 was obtained for the nanowires in a potential range from 0.1 to 0.9 V vs. SCE in 1 M sodium sulfate solution at a scan rate of 5 mV s-1. These materials can be useful to increase the specific capacitance by wetting behavior of electrolytes from their structural properties. © 2010 Elsevier B.V. All rights reserved.


Lim J.-H.,Sungkyunkwan University | Bae K.,Sungkyunkwan University | Shin J.-H.,Sungkyunkwan University | Kim J.-H.,Hanwha Chemical R and nter | And 3 more authors.
Powder Technology | Year: 2016

Computational particle-fluid dynamics (CPFD) simulations were carried out to determine the bed pressure drop and bubble behavior in bubbling fluidized beds produced using a shroud nozzle distributor. The fluidized bed had an internal diameter of 0.3m and height of 2.4m and was modeled using Barracuda, commercial CPFD software. The bed materials consisted of metal-grade silicon particles with dp, ρp, and Umf of 150μm, 2330kg/m3, and 0.02m/s, respectively. The total bed inventory and the static bed height were 75kg and 0.8m, respectively. Air was used as the fluidizing gas at room temperature and atmospheric pressure and was uniformly supplied at the inlet boundary below the distributor. The superficial gas velocity was controlled in the range between 0.07 and 0.17m/s, and the restitution coefficient of the collision model and the particle normal stress parameter, which affected the particle-particle interaction, were adjusted to obtain accurate simulation data. The results of each simulation were validated by comparing the pressure drop profile to that obtained through experiments under the same conditions. The values predicted for the bed pressure drop and the bubble volume fraction changed according to the restitution coefficient in the collision model and the particle normal stress. At Ps=5, the bed pressure drop and the bubble flow characteristics were similar to those obtained from the experimental data. © 2015 Elsevier B.V.


Cho J.,Hanwha Chemical R and nter | Lee H.,Hanwha Chemical R and nter | Hyun D.,Hanwha Chemical R and nter | Lee Y.,Hanwha Chemical R and nter | And 2 more authors.
Solar Energy | Year: 2013

Emitter wrap-through (EWT) solar cells with an 18.6% cell efficiency were fabricated by etch-back with etch resist, a selective emitter (SE) with reactive ion etching (RIE) and screen printing technologies. The short-circuit current densities (Jsc) were more than 40mA/cm2, but the cell efficiency was limited by the fill factor (FF), which was as low as 73.4%. An electroluminescence (EL) analysis showed that this low value was linked to shunts occurring in the via-holes. The doping profile difference between the wafer surface and the inside of the via-holes was statistically insignificant. However, the thickness of the deposited SiNx passivation layer in the via-holes decreased from the surface to the inner side, allowing the paste to penetrate the junction through the passivation layer and causing shunts during the firing process. By changing to Ag paste for the shallow emitter, changing the firing conditions and performing a process optimization, an efficiency of 19.5% with a FF of 77.6% was achieved using industrial 6-inch. Cz wafers under AM 1.5G. © 2013 Elsevier Ltd.


Lee J.-H.,Yonsei University | Sohn J.-H.,Yonsei University | Ryu S.Y.,Hanwha Chemical R and nter | Hong C.-S.,Yonsei University | And 2 more authors.
Journal of Cellular and Molecular Medicine | Year: 2013

Asthma is a chronic inflammatory disease induced by Type 2 helper T cells and eosinophils. Vascular cell adhesion molecule-1 (VCAM-1) has been implicated in recruiting eosinophils and lymphocytes to pathological sites in asthma as a regulatory receptor. Accordingly, monoclonal antibody (mAb) against VCAM-1 may attenuate allergic inflammation and pathophysiological features of asthma. We attempted to evaluate whether a recently developed human anti-VCAM-1 mAb can inhibit the pathophysiological features of asthma in a murine asthma model induced by ovalbumin (OVA). Leucocyte adhesion inhibition assay was performed to evaluate the in vitro blocking activity of human anti-VCAM-1 mAb. OVA-sensitized BALB/c mice were treated with human anti-VCAM-1 mAb or isotype control Ab before intranasal OVA challenge. We evaluated airway hyperresponsiveness (AHR) and bronchoalveolar lavage fluid analysis, measured inflammatory cytokines and examined histopathological features. The human anti-VCAM-1 mAb bound to human and mouse VCAM-1 molecules and inhibited adhesion of human leucocytes in vitro. AHR and inflammatory cell counts in bronchoalveolar lavage fluid were reduced in mice treated with human anti-VCAM-1 mAb as compared with a control Ab. The levels of interleukin (IL)-5 and IL-13, as well as transforming growth factor-β, in lung tissue were decreased in treated mice. Human anti-VCAM-1 mAb reduced goblet cell hyperplasia and peribronchial fibrosis. In vivo VCAM-1 expression decreased in the treated group. In conclusion, human anti-VCAM-1 mAb attenuated allergic inflammation and the pathophysiological features of asthma in OVA-induced murine asthma model. The results suggested that human anti-VCAM-1 mAb could potentially be used as an additional anti-asthma therapeutic medicine. © 2013 The Authors.


Kim J.-G.,Hanwha Chemical R and nter | Jang D.O.,Yonsei University
Tetrahedron Letters | Year: 2010

We developed a mild and convenient trifluoroacetylation process for amines using a combination of trichloroacetonitrile and triphenylphosphine. The reaction that we designed is applicable to the trifluoroacetylation of a wide variety of amines, including amines with stereogenic centers, which underwent trifluoroacetylation without racemization. © 2009 Elsevier Ltd. All rights reserved.


Kim W.,Korea Advanced Institute of Science and Technology | Yun C.,Doosan Heavy Industries and Construction | Jung K.T.,Hanwha Chemical R and nter | Park S.,Korea Advanced Institute of Science and Technology | Kim S.H.,Hanwha Chemical R and nter
Computers and Chemical Engineering | Year: 2012

Temperature control is crucial when designing a catalytic tubular reactor for exothermic reactions because hot spots in packed-bed tubes affect conversion, selectivity and lifespan of catalysts. To resolve the hot spot problem, a computer-aided scale-up method combining process modeling software, heat exchanger design software and computational fluid dynamics (CFD) analysis is proposed. The proposed method is composed of three steps as follows: firstly, the length and the number of tubes are determined to achieve a target production rate by the simulations of a single-tube reactor model. Secondly, the detailed geometry of a scaled-up reactor comprising multiple tubes is determined using heat exchanger design software. Finally, optimal operating conditions to control the hot spots are designated by CFD analysis. As a practical application, the method is applied to scaling up the single-tube reactor producing epichlorohydrin to a demonstration-scale reactor comprising 200 tubes so its optimal design and operating conditions are determined. © 2011 Elsevier Ltd.


Kim W.,Korea Advanced Institute of Science and Technology | Yun C.,Korea Advanced Institute of Science and Technology | Yun C.,Doosan Heavy Industries and Construction | Kim Y.,Korea Institute of Machinery and Materials | And 5 more authors.
Industrial and Engineering Chemistry Research | Year: 2011

A mathematical model for a tubular reactor producing epichlorohydrin (ECH) over titanium silicate-1 (TS-1) catalyst is proposed in this work. The Eley-Rideal mechanism is selected to describe the catalytic reaction, and pertinent kinetic parameters are estimated by a genetic algorithm combined with the Levenberg-Marquardt algorithm. The time-varying catalytic activity and effectiveness factor of a commercial TS-1 catalyst pellet are additionally included in the two-dimensional dynamic mass and energy transport model for the packed-bed tubular reactor. In a case study, the optimal length of the tubular reactor is determined by simulations using the developed model to maintain both conversion and selectivity above 96% during 90 days. The proposed model will contribute to effective design of industrial ECH production processes. © 2010 American Chemical Society.


Kim J.-G.,Hanwha Chemical R and nter | Jang D.O.,Yonsei University
Synlett | Year: 2010

We developed a simple, practical, and catalytic method for the N-formylation of a wide variety of amines in the presence of molecular iodine as a catalyst under solvent-free conditions. This reaction is applicable to the chemoselective N-formylation of amino groups and -amino acid esters without epimerization. © 2010 Georg Thieme Verlag Stuttgart · New York.


Cho S.-Y.,Yonsei University | Kim J.-G.,Hanwha Chemical R and nter | Chung C.-M.,Yonsei University
Journal of Nanoscience and Nanotechnology | Year: 2010

Four kinds of cinnamate-type monomers were synthesized as healing agents. Photoirradiation of the monomers gave cyclobutane-containing crosslinked polymers via [2+2] cycloaddition. Cyclobutane cleavage upon cracking of the crosslinked polymers and re-cycloaddition of the cracked polymers were investigated by FT-IR spectroscopy. Photochemical crack healing was demonstrated by measurement of flexural strength of crosslinked, cracked, and healed polymers. It was observed that microcracks with width of 200 nm to 2 μm were healed by photoirradiation. Copyright © 2010 American Scientific Publishers.

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