• Smart Structures and Systems
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• v.7 no.3
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• pp.199-211
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• 2011

Using computational modeling, we design a pair of biomimetic microcapsules that exploit chemical mechanisms to communicate and alter their local environment. As a result, these synthetic objects can undergo autonomous, directed motion. In the simulations, signaling microcapsules release "agonist" particles, while target microcapsules release "antagonist" particles and the permeabilities of both capsule types depend on the local particle concentration in the surrounding solution. Additionally, the released nanoscopic particles can bind to the underlying substrate and thereby create adhesion gradients that propel the microcapsules to move. Hydrodynamic interactions and the feedback mechanism provided by the dissolved particles are both necessary to achieve the cooperative behavior exhibited by these microcapsules. Our model provides a platform for integrating both the spatial and temporal behavior of assemblies of "artificial cells", and allows us to design a rich variety of structures capable of exhibiting complex dynamics. Due to the cell-like attributes of polymeric microcapsules and polymersomes, material systems are available for realizing our predictions.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3183-3189
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• 2010

In order to increase the specific capacitance and energy density of supercapacitors, non-aqueous supercapacitors were prepared using lithium transition-metal oxides and activated carbons as active materials. The electrochemical properties were analyzed in terms of the content of lithium transition-metal oxides. The results of cyclic voltammetry and AC-impedance analyses showed that the pseudocapacitance may stem from the synergistic contributions of capacitive and faradic effects; the former is due to the electric double layer which is prepared in the interface of activated carbon and organic electrolyte, and the latter is due to the intercalation of lithium ($Li^+$) ions. The specific capacitance and energy density of a supercapacitor improved as the lithium transition-metal oxides content increased, showing 60% increase compared to those of supercapacitor using a pure activated carbon positive electrode.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.100-103
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• 2010

In this study, NO reduction behaviors of copper-loaded mesoporous molecular sieves (Cu/MCM-41) have been investigated. The Cu loading on MCM-41 surfaces was accomplished by a chemical reduction method with different Cu contents (5, 10, 20, and 40%). $N_2/77$ K adsorption isotherm characteristics, including the specific surface area and pore volume, were studied by BET's equation. NO reduction behaviors were confirmed by a gas chromatography. From the experimental results, the Cu loading amount on MCM-41 led to the increase of NO reduction efficiency in spite of decreasing the specific surface area of catalysts. This result indicates that highly ordered porous structure in the MCM-41 and the presence of active metal particles lead the synergistical NO reduction reactions due to the increase in adsorption energy of MCM-41 surfaces by the Cu particles.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.180-181
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• 2019

In this study, in order to find new uses for CBS dust, the chemical components of CBS dust were analyzed and effectively proposed a method. Chemical analysis shows that CBS dust contains a large amount of alkali in addition to chloride therefore, if CBS dust is used for secondary concrete products that use high amounts of mixed materials without rebars, it will be found that it can be used effectively for enhancing strength by active alkali.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.179-184
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• 2000

Chemical Mechanical Polishing (CMP) refers to a material removal process done by rubbing a work piece against a polishing pad under load in the presence of chemically active and abrasive containing slurry. CMP process is a combination of chemical dissolution and mechanical action. The mechanical action of CMP involves hydrodynamic behavior. The liquid slurry is trapped between the work piece and pad forming a hydrodynamic film. For the first step to understand material removal mechanism of the CMP process, the hydrodynamic analysis is done with semiconductor wafer. Three-dimensional Reynolds equation is applied to get pressure distribution of the slurry film. Shear stress distributions on the wafer surface are also analyzed

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.274-279
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• 1992

Immobilization method of lariat azacrown ethers, containing hydroxyl group in the side arm of crown ring, on the polymer matrix and the phase-transfer catalytic activity of thus obtained immobilized lariat azacrown ethers were studied. Polystyrene resins with crown ether structures and hydroxyl groups adjacent to the macrorings were prepared by the reaction of crosslinked polystyrene resins containing epoxy groups with monoaza-15-crown-5 or monoaza-18-crown-6. Microporous crosslinked polystyrene resins containing epoxy group for the syntheses of these immobilized lariat crown catalysts were prepared by suspension polymerization of styrene, divinylbenzene (DVB 2%) and vinylbenzylglycidyl ether. The immobilized lariat catalysts with 10-20% ring substitution exhibited maximal activity for the halogen exchange reactions of 1-bromooctane with aqueous KI or NaI under triphase heterogeneous conditions. Immobilized catalyst exhibited higher activity than corresponding catalyst without the hydroxyl group and this result was suggested that the active site have a structure in which the $K^+$ ion was bound by the cooperative coordination of the crown ring donors and the hydroxyl group in the side arm.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.185-189
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• 2004

Methanol dehydration to dimethyl ether (DME) has been investigated over ZSM-5 zeolites and compared with that of ${\gamma}-Al_2O_3$. Although the catalytic activity was decreased with an increase in silica/alumina ratio, the DME selectivity increased. H-ZSM-5 and NaH-ZSM-5 zeolites were more active for conversion of methanol to DME than ${\gamma}-Al_2O_3$. $Na^+$ ion-exchanged H-ZSM-5 (NaH-ZSM-5) shows higher DME selectivity than H-ZSM-5 due to the selective removal of strong acid sites.

• Bulletin of the Korean Chemical Society
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• v.20 no.12
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• pp.1413-1417
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• 1999

Chemical poisoning of Ni/MgO catalyst was induced by hot alkali carbonate vapor in molten carbonate fuel cell (MCFC), and the poisoned (or contaminated) catalyst was characterized by TPR/TPO, FTIR, and XRD analysis. Carbonate electrolytes such as K and Li were transferred to the catalyst during DIR-MCFC operation at 650 ℃. The deposition of alkali species on the catalyst consequently led to physical blocking on catalytic active sites and structural deformation by chemical poisoning. TPR/TPO analysis indicated that K species enhanced the reducibility of NiO thin film over Ni as co-catalyst, and Li species lessened the reducibility of metallic Ni by chemical reaction with MgO. FTIR analysis of the poisoned catalyst did not exhibit the characteristic ${\vector}_1$$(D_{3h})$ peaks (1055 $cm^{-1},\;1085\;cm{-1})$ for pure crystalline carbonates, instead a new peak (1120 $cm^{-1})$ was observed proportionally with deformed alkali carbonates. From XRD analysis, the oxidation of metallic Ni into $Ni_xMg_{1-x}O$ was confirmed by the peak shift of MgO with shrinking of Ni particles. Conclusively, hot alkali species induced both chemical poisoning and physical deposition on Ni/MgO catalyst in DIR-MCFC at 650 ℃.

• Current Photovoltaic Research
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• v.9 no.4
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• pp.137-144
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• 2021

In this study, the microstructure of the CVD-fabricated Cu(In,Ga)Se₂ (CIGSe) absorber layer by simulating the stacking sequence used in a co-evaporation method, and changes solar cell performance were investigated. The absorber layer prepared by stacking CuSe and (In,Ga)Se between InSe is separated into Ga-free CuInSe₂ and Ga-rich CIGSe, and transformed to CIGSe by selenization heat treatment with slight improvement in the the solar cell efficiency. However, in CVD, since the supply of liquid Cu-Se is not as active as in the co-evaporation method, the nanoocrystalline layer containing a large amount of Ga remained independently in the absorption layer, which acted as a cause of the loss of J_SC and FF. Therefore, by using a precursor structure in which CuGa is sputter-deposited on a single layer of InSe deposited by CVD, performance parameters of V_OC, J_SC, and FF could be greatly improved.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.68-72
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• 2013

Until a recent day, degradation of PEMFC MEA (membrane and electrode assembly) has been studied, separated with membrane degradation and electrode degradation, respectively. But membrane and electrode were degraded coincidentally at real PEMFC operation condition. During simultaneous degradation, there was interaction between membrane degradation and electrode degradation. The effect of electrode degradation on membrane degradation was studied in this work. We compared membrane degradation after electrode degradation and membrane degradation without electrode degradation. I-V performance, hydrogen crossover current, fluoride emission rate (FER), impedance and TEM were measured after and before degradation of MEA. Electrode degradation reduced active area of Pt catalyst, and then radical/$H_2O_2$ evolution rate decreased on Pt. Decrease of radical/$H_2O_2$ reduced the velocity of membrane degradation.