• Membrane and Water Treatment
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• v.7 no.5
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• pp.463-476
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• 2016

In this study, application of polypropylene hollow fiber membrane contactors for $CO_2$ removal from water in liquid-liquid extraction (LLE) mode was simulated. For this purpose, a steady state 2D mathematical model was developed. In this model axial and radial diffusion was considered to $CO_2$ permeation through the hollow fibers. $CO_2$ laden water is fed at a constant flow rate into the lumen side, permeated through the pores of membrane and at the end of this process, $CO_2$ solution in the lumen side was extracted by means of aqueous diethanolamine (DEA) and chemical reaction. The simulation results were validated with the experimental data and it was found a good agreement between them, which confirmed the reliability of the proposed model. Both simulation and experimental results confirmed the reduction in the percentage of $CO_2$ removal by increment of feed flow rate.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.310-313
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• 2011

본 논문에서는 지구온난화의 주요원인 중의 하나인 이산화탄소를 포집하기 위한 새로운 흡수제를 연구하였다. 액상 흡수법에서 가장 중요한 핵심 기술요소는 성능과 경제성면에서 우수한 흡수제를 개발하는 것이다. 흡수평형장치인 VLE(Vapor-Liquid Equilibrium)장치를 사용하여 신규흡수제의 이산화탄소 흡수능을 평가하고 특성을 알아봄으로써 신 흡수제를 개발하고자 하였다. 기존 아민흡수제인 MEA(monoethanolamine), DEA(diethanolamine)와 비교한 결과 아미노산염 흡수제의 경우 MEA (1.108), DEA (1.105)의 이산화탄소 흡수능보다 0.15～0.2 (mol $CO_2$/mol absorbent) 더 높은 흡수능과 2.5～3배 더 빠른 겉보기 속도를 나타내는 것을 확인하였다. 본 연구를 통하여 개발된 아미노산염 흡수제가 경제적인 이산화탄소 포집공정을 구현할 수 있는 가능성을 확인하였다.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.527-538
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• 2021

The purpose of the study is to determine the efficiency, position, and partner selection of securities companies via the negative super-SBM model used in data envelopment analysis (DEA). This model utilizes a variety of inputs, including current assets, non-current assets, fixed assets, liabilities, owner's equity and charter capital, and outputs including net revenue, gross profit, operating profit, and net profit after tax collected from the financial reports (Vietstock, 2020) of 32 securities companies, operating during the period from 2016 to 2019, negative data are collected as well. Empirical results determined both efficient and inefficient terms, and then further determined the position of each securities firm under consideration of every term. The overall score arrived at discovered a large performance change realizing a maximum score able to reach 20.791. In the next stage, alliancing inefficient companies was carried out based on the 2019 scores to seek out optimal partners for the inefficient companies. The tested result indicated that AAS was the best partner selection when its partners received a good result after alliancing, as with FTS (11.04469). The partner selection is deemed as a solution helpful to inefficient securities companies in order to improve their future efficiency scores.

• Journal of the Speleological Society of Korea
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• no.76
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• pp.1-13
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• 2006

Electrophoretic deposition (EPD) of alcohol YBCO suspensions on the Ag wire electrode is studied. Poly(ethylene glycol) was coordinated to a structure formed by the EPD process with YBCO particles. The suspension is characterized in terms of zeta potential and conductivity. The d.c electric fields of 200-300 V/cm are applied for 1-10 min. The optimal condition for the EPD allows modifying the properties and microstructure of the deposited films. Superconducting coatings with nanometer-sized pores and a preferred orientation along the c-axis were prepared from the result with chemically modified precursor solution. In contrast, YBCO coatings of submicrometer-sized pores and randomly orientated grains were prepared from the solution without PEG.

• Journal of information and communication convergence engineering
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• v.1 no.1
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• pp.27-30
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• 2003

Electrophoretic deposition (EPD) of alcohol YBCO suspensions on the Ag wire electrode is studied. Poly(ethylene glycol) was coordinated to a structure formed by the EPD process with YBCO particles. The suspension is characterized in terms of zeta potential and conductivity. The d.c electric fields of 200-300 V/cm are applied for 1-10 min. The optimal condition for the EPD allows modifying the properties and microstructure of the deposited films. Superconducting coatings with nanometer-sized pores and a preferred orientation along the c-axis were prepared from the result with chemically modified precursor solution. In contrast, YBCO coatings of submicrometer-sized pores and randomly orientated grains were prepared from the solution without PEG.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.53-56
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• 2003

The properties of YBCO thick film coated on Ag wire with YBCO powder is deeply affected by cracking on its surface which was deposited in organic solution by electrophoretic method. YBCO superconducting thick films were prepared on Ag wire$({\Psi}0.8mm)$ by electrophoresis in acetone with added PEG (Poly-Ethylene Glycol, 3% in Acetone), 1ml for being crack-free. The surface properties of YBCO superconducting wire was evidently improved with adding PEG. Added PEG which molecular weight is 600, 1000, 3400 was affected with variation of deposition voltages to the surface properties of samples. As a result, with adding PEG (its molecular weight is 3400), YBCO superconducting wire was better on its surface properties.

• Transactions on Electrical and Electronic Materials
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• v.4 no.5
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• pp.6-9
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• 2003

Electrophoretic deposition (EPD) of alcohol YBCO suspensions on the Ag wire electrode is studied. Polyethyleneglycol was coordinated to a structure formed by the EPD process with YBCO particles. The d.c electric fields of 200-300 V/cm are applied for 1-10 min. The optimal condition for the EPD allows modifying the properties and microstructure of the deposited films. Superconducting coatings with nanometer-sized pores and a preferred orientation along the caxis were prepared from the result with chemically modified precursor solution. In contrast, YBCO coatings of submicrometer-sized pores and randomly orientated grains were prepared from the solution without PEG.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.295-298
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• 2011

This paper is to analyze an app curriculum using smartphone authoring solution for the education of smartphone applications with optimized effectiveness by reducing time period of development. In addition, The best goal will find the effective training methodology for developers to develop application program running on smartphones with quick and easy way. The final goal of the paper is to find the best way on how to develop business application programs using an authoring solution for smartphone application. In conclusion, this paper covers the best solution and education of an high-tech authoring solution design for the effective smartphone applications to be used by experienced developers with perfect knowledge of the field for practical on-site.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.557-560
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• 2003

The submicron $YBa_2Cu_3O_x$ powder was prepared by the sol-gel method. The particle size is distributed from 0.2 to $1.0\;{\mu}m$, which benefits to eliminate the micro-cracks formed in the $YBa_2Cu_3O_x$ films deposited by electrophoresis. The powder was single phase of $YBa_2Cu_3O_x$ examined by X-ray diffraction. In the sol-gel process the citrate gel was formed from citric acid and nitrate solution of $Y_2O_3$, $Ba(NO_3)O_2$ and CuO. When pH values were adjusted to $6.4{\sim}6.7,\;Ba(NO_3)O_2$ could be dissolved in the citrate solution completely. Appropriate evaporative temperature of the sol-gel formation is discussed. After the heat treatment the transition temperature($T_c$) and critical current density($J_c$) of the $YBa_2Cu_3O_x$ samples made of the submicron powder were measured.

• Journal of the Speleological Society of Korea
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• no.76
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• pp.49-55
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• 2006

The submicron $YBa_2Cu_3O_x$ powder was prepared by the sol-gel method. The particle size is distributed from 0.2 to 1.0 ${\mu}m$, which benefits to eliminate the micro-cracks formed in the $YBa_2Cu_3O_x$ films deposited by electrophoresis. The powder was single phase of $YBa_2Cu_3O_x$ examined by X-ray diffraction. In the sol-gel process the citrate gel was formed from citric acid and nitrate solution of $Y_2O_3$, $Ba(NO_3)_2$ and CuO. When pH values were adjusted to 6.4-6.7, $Ba(NO_3)_2$ could be dissolved in the citrate solution completely. Appropriate evaporative temperature of the sol-gel formation is discussed. Acetone is used as electrophoreticsolution, in which some water and iodine (0.2 g/1) and polyethylene glycol (2 vol. %) are added. The concentrations of $YBa_2Cu_3O_x$ powders is 20g/l. The thickness of deposited film could be more than 50 ${\mu}m$ in 3 minutes of depositing time. The most EPD films could be 90K zero resistance and the Jc values were over 1000A/cm2 (0 H, 77 K).