• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.545-548
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• 2009

최근 천연가스 개발의 중요성이 대두되면서 심해저 퇴적층에 존재하고 있는 천연가스 하이드레이트 개발에 많은 연구가 진행되고 있다. 본 연구에서는 심해저 퇴적층에 부존하는 가스 하이드레이트 조건과 유사하게 하기위해 3 wt% 농도의 염수를 다공성 실리카 젤 기공에 넣어 사용하였다. 기공의 직경에 따른 영향을 알아보기 위해 기공 직경이 각각 6.0, 15.0, 30.0 nm인 실리카 젤을 사용하여, 천연가스 주성분인 에탄, 프로판, 메탄+프로판 하이드레이트의 3상 (H-Lw-V) 평형을 측정하였다. 그 결과 기공의 크기가 작아질수록 각각의 벌크 상태의 에탄, 프로판, 메탄+프로판 하이드레이트에 비해 하이드레이트의 평형조건이 온도는 낮아지고 압력이 높아지는 저해효과가 커짐을 알 수 있었다. 실험값으로 부터 기공 내의 물과 하이드레이트상 사이의 계면장력 값을 Gibbs-Thomson식에 의해 구할 수 있으며, 열역학 계산을 통하여 실험값과 비교하였다. 본 연구에서 얻어진 결과는 심해저 천연가스 개발, 이산화탄소 심해저장 등의 가스 하이드레이트 응용 연구에 유용한 기초 자료가 될 것이다.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.60-67
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• 2008

The catalytic filter of Cu-ZSM5/alumina beads was considered to reduce NOx in the urea SCR system. Catalytic support of porous alumina beads with mean pore size $130{\mu}m$ and porosity $75{\sim}83%$ were prepared using foaming and gel-casting method. The Cu-ZSM5 catalysts were coated on the supporting alumina beads using $Cu(NO_3)_2$ by ion exchange method. After a washcoating process was applied to coat 10w% Cu-ZSM5 on porous alumina bead, coating layer was estimated $20{\mu}m$ in thickness. The characterization and the feasibility as a catalytic supports were investigated. And the NOx conversion test in Cu-ZSM5/Alumina Beads filter system was conducted by using Urea as reductants under laboratory test. The NOx conversion was increased as size and porosity of beads and observed more than 95% excellent NOx conversion above $300^{\circ}C$.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.3-17
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• 2007

This paper provides an introduction to life-span simulation and numerical approach to support the performance design processes of reinforced concrete structures. An integrated computational system is proposed for life-span simulation of reinforced concrete. Conservation of moisture, carbon dioxide, oxygen, chloride, calcium and momentum is solved with hydration, carbonation, corrosion, ion dissolution. damage evolution and their thermodynamic/mechanical equilibrium. Coupled analysis of mass transport and damage mechanics associated with steel corrosion is presented for structural performance assessment of reinforced concrete. Multi-scale modeling of micro-pore formation and transport phenomena of moisture and ions are mutually linked for predicting the corrosion of reinforcement and volumetric changes. The interaction of crack propagation with corroded gel migration can also be simulated. Two finite element codes. multi-chemo physical simulation code (DuCOM) and nonlinear dynamic code of structural reinforced concrete (COM3) were combined together to form the integrated simulation system. This computational system was verified by the laboratory scale and large scale experiments of damaged reinforced concrete members under static loads, and has been applied to safety and serviceability assessment of existing structures. Based on the damage details predicted by the nonlinear finite element analytical system, the life-span-cost of RC structures including the original construction costs and the repairing costs for possible damage during the service life can be evaluated for design purpose.

• Journal of Ginseng Research
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• v.19 no.3
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• pp.237-243
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• 1995

Agmatine iminohydrolase (EC 3.5.3.12) catalyzes the hydrolysis of agmatine into putrescine. The enzyme seems to be one of the critical enzymes in putrescine biosynthesis. The enzyme was purified to homogeneity from Panax ginseng C.A. Meyer by combined method of ammonium sulfate 1 fractionation, DEAR anion exchange column, hydroxyapatite column and agmatine carboxyhexyl Sepharose 4B affinity column. The molecular weight estimated by native pore gadient polyacrylamide gel electrophoresis was 71, 000 Dalton, while that estimated by SDS-PAGE was 70, 000 Dalton, indicating a monomeric enzyme. The optimal pH and temperature were 9.0 and 37$^{\circ}C$, respectively. The Km and 1 Vmax for agmatine were 8.3 mM and 14.4 nmole/hr, respectively. Heat stability of this enzyme was high. The enzyme was observed to be inhibited by polyamines such as putrescine, cadaverine, spermidine and spermine. Especially, putrescine was a potent inhibitor of the purified enzyme. These results suggest that polyamines could be important in growth regulation of Panax ginseng C.A. Meyer.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.193-196
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• 2009

Mesoporous $TiO_2$ material was synthesized from diblock copolymers with ethylene oxide chains via a sol-gel process in aqueous solution. The properties of these materials were characterized with several analytical techniques including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), wide angle X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Barrett-Joyner-Halenda (BJH) analysis. The mesoporous $TiO_2$ materials calcined at 400${^{\circ}C}$ were found to have specific surface areas 212 $m^2g^-1$, average pore sizes 6.2 nm, and their average crystal sizes were found to be 8.2 nm. The photocatalytic activity of mesoporous $TiO_2$ was characterized with UV-Vis spectroscopy, and it was found to be 5.8 times higher than that of Degussa P25 $TiO_2$ (P25). For deactivation of Escherichia coli, mesoporous $TiO_2$ also has high photocatalytic inactivity than that of P25. Such a high photocatalytic activity is explained with large surface area and small crystal size with wormhole-like mesoporous structure.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1432-1433
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• 2006

$Li_{2}CO_3$ doped $Ba_{0.5}Sr_{0.5}TiO_3$ ceramics were fabrication by sol-gel method. Sintering temperature must be suited to the LTCC technology. Structure and dielectric properties were investigated for effect of $Li_{2}CO_3$ dopants at BST. Structure of $Li_{2}CO_3$ doped $Ba_{0.5}Sr_{0.5}TiO_3$ ceramics were dense and homogeneous with almost no pore. Relative permittivity was decreased and dielectric loss was increased with increasing $Li_{2}CO_3$ doping rations. In the case of the 3wt% $Li_{2}CO_3$ doped $Ba_{0.5}Sr_{0.5}TiO_3$ ceramics sintered at $900^{\circ}C$, relative permittivity and dielectric loss were 907 and 0.003 at 100 kHz.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2191-2197
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• 2018

To remove tar and produce environment-friendly $H_2$, one of the promising routes is the sorption-enhanced steam reforming (SESR) process, in which the $CO_2$ sorbent is a key element. We prepared the $CO_2$ sorbents with $Ca_{12}Al_{14}O_{33}$ as carrier with various methods. Their characterizations were examined, and the sample prepared by solgel (SG) method showed the strongest CaO and $Ca_{12}Al_{14}O_{33}$ phases and the most excellent pore structure among all the samples. Then, a thermogravimetric experiment was conducted, and the results showed that the sample prepared by sol-gel (SG) method had the best $CO_2$ adsorption capacity and excellent long-term cyclic stability. Finally, the sorbent was used into the steam reforming experiments of tar. Under the action of the sorbent, the reforming reaction was enhanced in-situ, with the $H_2$ yield and concentration improved obviously, and especially, $H_2$ concentration can reach over 98.85%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.99-105
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• 2014

$LiCoO_2$ thin film have received attention as cathodes of thin-film microbatteries. In this study, $LiCoO_2$ thin films were synthesized on Au substrates by sol-gel spin coating method and electrochemical properties were investigated under annealing temperature and time. The phycochemical properties of $LiCoO_2$ thin film were investigated by X-ray diffraction, scaning electron microscopy and atomic force microscopy. The electrochemical properties were characterized using galvanostatic charging/discharging cycling tests. From X-ray diffraction, as-grown films annealed at $550^{\circ}C$ and $750^{\circ}C$ are presumed to be spinel structure and a single phase of the layered-rock-salt, respectively. The RMS roughness and grain size of the films which annealed at $750^{\circ}C$ has similar values for annealing time 10 and 30 min, while for annealing time 120 min surface roughness, grain size increase and pore appearance were observed. The first discharge capacity of $LiCoO_2$ thin films annealed at $750^{\circ}C$ for 10, 30 and 120 min is about 54.5, 56.8 and $51.87{\mu}Ah/cm^2{\mu}m$, respectively. Corresponding capacity retention at 50th cycle is 97.25, 76.69, 77.19%.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.76-81
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• 1998

Physical adsorption on a silica gel(pore size of 80 nm, particle size of $10{\mu}m$)has been studied for binary mixture of acetone diluted in $CO_2$ by use of a FTIR transmission technique and we have compared the result of FTIR transmission technique with that of a chromatographic technique. Measurements were made at 313.2 K and under pressures up to 15MPa. As the pressure increases from 0.1MPa, the IA(Integral Absorbance) of the hydrogen-bonded OH groups interacting with acetone and adsorbed amount by use of a chromatographic technique increases at first, and reaches a maximum at a pressure below the critical pressure of $CO_2$, and then the intensities decrease gradually with increasing pressure. It is found that the pressure dependency of the chromatographic isotherm is a little larger than that of spectroscopic isotherm in the supercritical fluid region. This difference might be attributable to the weaker van der Waals force and relatively stronger hydrogen-bonding force influencing the adsorption of acetone on the sllica gel. The unique spectroscopic characteristics of amine group which vibrational frequencies of hydroxyl groups on the silica gel surface shift downward to about $1300cm^{-1}$ were measured from experimental result of triethylamine diluted in $CO_2$ or $N_2$.

• Journal of Veterinary Clinics
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• v.32 no.3
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• pp.224-230
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• 2015

This study was designed in the fabricated poly (L-Lactic-co-${\varepsilon}$-Caprolactone) (PLCL) scaffold using chitosan-alginate hydrogel, which would be more suitable to maintain the biological and physiological functions continuing three dimensional spatial organizations for chondrocytes. As a scaffold, hydrogels alone is weak at endure complex loading within the body. In this study, we made cell hybrid scaffold constructs with poly (L-Lactic-co-${\varepsilon}$-Caprolactone) (PLCL) scaffold and hydrogels to make a three-dimensional composition of cells and extracellular matrix, which would be a mimic of a native cartilage. Using a particle leaching technique with NaCl, we fabricated a highly-elastic scaffold from PLCL with 85% porosity and $300-500{\mu}m$ pore size. A mixture of bovine chondrocytes and chitosan-alginate gel was seeded and compared with alginate as a control on the PLCL scaffold. The cell maturation, proliferation, extracellular matrix synthesis, glycosaminoglycans (sGAG) production and collagen type-II expressions were better in chondrocytes seeded in chitosan-alginate hydrogel than in alginate only. These results indicate that chondrocytes with chitosan-alginate gel on PLCL scaffolds provide an appropriate biomimetic environment for cell proliferation and matrix synthesis, which could successfully be used for cartilage repair and regeneration.