• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.581-582
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.711-712
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1219-1220
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.189-190
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• 2011

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.273-278
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• 2015

${\alpha}-Al_2O_3$ was synthesized by solvothermal synthesis using ${\alpha}-Al_2O_3$ seed, precursor of fine boehmite (Al(OOH)) or gibbsite ($Al(OH)_3$), and 1, 4-butanediol solvent. The seed content and precursor type were selected as variables in order to synthesize ${\alpha}-Al_2O_3$. The formation time of ${\alpha}-Al_2O_3$ was reduced and the size of the particles was decreased with addition of the seed. When the seed content was increased, the size of the synthesized ${\alpha}-Al_2O_3$ was reduced. Morphologies of the as-synthesized ${\alpha}-Al_2O_3$ with ${\alpha}-Al_2O_3$ seed were polyhedron-shaped, while the shape was plate-like or polyhedral without the seed, depending on the additives or the average particle size of the boehmite precursor. The aggregation of as-synthesized ${\alpha}-Al_2O_3$ from boehmite was smaller than that from gibbsite. As-synthesized ${\alpha}-Al_2O_3$, with 140 nm size, was obtained by using the seed and boehmite precursor.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.5
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• pp.625-632
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• 2004

Perfluorocompounds ($PFC_s$), such as tetrafluoromethane ($CF_4$) and hexafluoroethane ($C_2F_6$), have been widely used as plasma etching and chemical vapor deposition (CVD) gases for semiconductor manufacturing processes. Since these $PFC_s$ are known to cause a greenhouse effect intensively, there has been a growing interest in reducing $PFC_s$ emissions. Among various $CF_4$ decomposing techniques, a dielectric barrier discharge (DBD) is considered as one of a promising candidate because it has been successfully used for generating ozone ($O_3$) and decomposing nitrogen oxide (NO). Firstly, optimal concentration of oxygen for $CF_4$ decomposition was found to figure out how many primary and secondary reactions are associated with DBD process. Secondary, to find effective discharge method for $CF_4$ decomposition, a streamer and a glow mode in DBD are experimentally compared, which includes (i) coaxialcylinder DBD, (ii) DBD reactor packed with glass beads. and (iii) a glow mode operation with a helium gas. The test results showed that optimal concentration of oxygen was ranged 500 ppm~1% for treating 500 ppm of $CF_4$ and helium glow discharge was the most efficient one to decompose $CF_4$.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.5
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• pp.1-11
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• 2015

Jeju Island is managed intensively in terms of environmental and ecological aspect because of its extraordinary ecosystem types comprising numerous rare, protected flora and fauna. To depict rapid change of habitat status in Jeju Island, the InVEST Habitat Quality model has been operated and compared analytically with the Eco-Natural map. The Habitat Quality map of Jeju Island is turned out to have similar inclination with Eco-Natural map. We compared the average habitat quality value in each Eco-natural map class in Jeju Island and the habitat quality value of first second third grade and non-included area decreased as 0.95 0.76, 0.53 and 0.37 in eco natural map respectively. Compared to biodiversity map based on biological investigation, the result of the InVEST habitat quality model can be simply obtained by land cover map with threat and sensitivity data. Further studies are needed to make explicit coefficients for Jeju Island and Korean peninsula, then the Habitat Quality model could be applied to past and future scenarios to analyze extent of habitat degradation in time series to help decision makers.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.7
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• pp.902-909
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• 2012

This study is aimed to develop a new type of micro cross-flow hydro turbine which has very simple structure and relatively high efficiency. Micro eco cross-flow hydro turbine (ECFT) is proposed to apply in the ranges of very low and middle specific speeds in order to extend the operational range of the turbine. In order to not only obtain a basic data for a new design method of ECFT but also improve the turbine efficiency, experiments and CFD analysis on the performance and internal flow characteristics of the turbine model are conducted. According to the present study results, anti-recirculation block (ARB) and relatively wide turbine width with high flow rate improve the turbine efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1203-1206
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• 2008

• Journal of Hydrogen and New Energy
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• v.31 no.1
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• pp.57-64
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• 2020

The water-gas shift reaction for the compact reformer was carried out at a gas hourly space velocity of 72,152 h^-1 over the Cu-Nb-CeO₂ catalysts prepared by co-precipitation method. In order to investigate the effect of Nb₂O₅ promotion over a Cu-CeO₂ catalyst, the Nb₂O₅ loading amount was systematically changed from 0 to 5 wt.%. Among the prepared catalysts, the Cu-Nb-CeO₂ (1%) catalyst showed the highest catalytic activity (CO conversion=61% at 400℃) as well as 100% CO₂ selectivity. The high activity and stability of Cu-Nb-CeO₂ (1%) catalyst are correlated to high Brunauer-Emmett-Teller surface area, small metallic Cu crystallite size, and enhanced redox property.