• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.5
• /
• pp.79-84
• /
• 2004

We evaluated the reduction performance of NOx storage catalyst and TWC for lean-burn natural gas engine by the model gas. The method of unsteady state reaction was used to compare with reduction performances of NOx storage catalyst and TWC. It was found that the effective parameter was rich spike duration, temperature of the model gas. In the presence of $CO_2$ and $H_2O$ in the reaction mixture was decreased the NOx reduction performance.

• Journal of Microbiology and Biotechnology
• /
• v.11 no.3
• /
• pp.389-393
• /
• 2001

An $\alpha$-glucosidase inhibitor, CK-4416, was identified from the culture broth of Streptomyces sp. CK-4416. CK-4416, which had some specificity against intestinal disaccharidases, especially sucrase and matlase activities, was purified by adsorption and cationic ion exchange chromatographies. The molecular formula was determined to be $C_{37}H_{63}NO_{30}$ (MW 1001.31) by FAB-MS and NMR analyses. In vitro studies found CK-4416 to show a potent inhibitory activity against sucrase and maltase, but it had low inhibition against $\alpha$-amylase.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.11 no.1
• /
• pp.67-71
• /
• 2006

This paper compares regression and neural network modeling approaches to predict competitive biosorption equilibrium data. The regression approach is based on the fitting of modified Langmuir-type isotherm models to experimental data. Neural networks, on the other hand, are non-parametric statistical estimators capable of identifying patterns in data and correlations between input and output. Our results show that the neural network approach outperforms traditional regression-based modeling in correlating and predicting the simultaneous uptake of copper and cadmium by a microbial biosorbent. The neural network is capable of accurately predicting unseen data when provided with limited amounts of data for training. Because neural networks are purely data-driven models, they are more suitable for obtaining accurate predictions than for probing the physical nature of the biosorption process.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.6
• /
• pp.95-95
• /
• 2000

(No Abstract.see full/text)

• Journal of the Korean Geotechnical Society
• /
• v.16 no.6
• /
• pp.97-103
• /
• 2000

지반내 중금속의 저류와 이동에 대한 가장 중요한 인자는 토양 간극수의 pH이다. 점토의 완충능을 kaolinite, hectorite, attapulgite, Na-bentonite와 같은 4가지 점토에 대하여 연구하였다. 완충능의 크기는 hectoriteattapulgite>kaolinite의 순으로 나타났다. 완충능의 크기는 지반내 탄산염 함량과 양이온 교환능력이 완충능의 크기에 가장 영향을 미치며 유기물 함량과 비표면적의 영향은 적었다. 토양의 완충능을 모델링하기 위하여 수소 이온과 토양표면의 화학반응 기간의 화학반응을 정전흡착 모델을 이용하여 모델링하였다. 또한 탄산염 함량과 양이온 교환능력을 함수로 하는 회귀식을 제안하였다. 모델 검증을 위하혀 모델 예측치와 실험치를 비교하였는데 정전 흡착모델을 이용한 예측치가 실험치와 근사한값을 나타냈다.

• Journal of the Korean Ceramic Society
• /
• v.26 no.4
• /
• pp.539-549
• /
• 1989

Polycrystalline TiO2 thin films were deposited on Si and Al2O3 substrates by CVD method. Ethyl titanate, Ti(OC2H5)4, was used as a source material for Ti and O, and Ar was used for carrier gas. In the surface chemical reaction controlled deposition condition, the apparent activation energy of 6.74 Kcal/mole was obtained, and the atomic adsorption on substrate surface was proved to be governed by Rideal-Elley mechanism. In the mass transfer controlled deposition condition, the deposition rate was in a good agreement with the result which was calculated by the simple boundary layer theory. It was also observed that TiO2 thin films show different surface morphology according to the different deposition mechanism, which was fixed by deposition conditions. This phenomenon could be well explained by the surface perturbation theory.

• Corrosion Science and Technology
• /
• v.3 no.4
• /
• pp.148-153
• /
• 2004

Magnesium thin flims were prepared on cold-rolled steel substrates by RF magnetron sputtering technique. The influence of argon gas pressure and substrate bias voltage on their crystal orientation and morphology of the coated films were investigated by scanning electron microscopy (SEM) and X-ray diffraction, respectively. And the effect of crystal orientation and morphology of magnesium films on corrosion behaviors was estimated by measuring anodic polarization curves in deaerated 3%NaCl solution. From the experimental results, all the sputtered magnesium films showed obviously good corrosion resistance to compare with 99.99% magnesium target of the sputter-evaporation metal. Finally it was shown that the Corrosion-resistance of magnesium films can be improved greatly by controlling the crystal orientation and morphology with effective use of the plasma sputtering technique.

• Journal of Microbiology and Biotechnology
• /
• v.24 no.1
• /
• pp.48-51
• /
• 2014

${\alpha}$-Neoagarooligosaccharide (${\alpha}$-NAOS) hydrolase was purified from Cellvibrio sp. OA-2007 by using chromatographic techniques after hydroxyapatite adsorption. The molecular masses of ${\alpha}$-NAOS hydrolase estimated using SDS-PAGE and gel filtration chromatography were 40 and 93 kDa, respectively, and the optimal temperature and pH for the enzyme activity were $32^{\circ}C$ and 7.0-7.2. ${\alpha}$-NAOS hydrolase lost 43% of its original activity when incubated at $35^{\circ}C$ for 30 min. The enzyme hydrolyzed neoagarobiose, neoagarotetraose, and neoagarohexaose to galactose, agarotriose, and agaropentaose, respectively, and produced 3,6-anhydro-L-galactose concomitantly; however, it did not degrade agarose.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.10a
• /
• pp.134.2-135
• /
• 2003

지초(Lithospermum efthrorhizon)뿌리는 예로부터 한방약제로 이용되어져 왔으며, 지초 뿌리에 함유된 naphtoquinon계 색소물질인 shikonin은 항암, 항균, 항바이러스, 항염증 등의 효과가 있다고 보고되었다. 그러나 지초뿌리에 함유된 기능성 물질에 관한 연구는 미비한 실정이다. 이에 본 연구에서는 지초뿌리에서 기능성 물질의 탐색 및 기능성 해명연구를 위하여 지초뿌리를 ethanol로 추출한 후 이 추출물을 n-hexane, EtOAc, MeOH로 순차적으로 추출하여 MeOH추출물을 얻었다. 이 MeOH추출물을 silica gel adsorption column chromatography, ODS column chromatography, Sephadex LH-20 column chromatography로 순차 정제한 후 Shodex Asahipak column을 이용한 GPC-HPLC에 의해 활성 물질을 분리하였다. 분리된 물질들은 1H-NMR, 13C-NMR, COSY, HSQC, HMBC, FAB-MS 등의 기기분석을 통해 당 관련 화합물인 것으로 판명되었다.

• Journal of Integrative Natural Science
• /
• v.3 no.4
• /
• pp.219-225
• /
• 2010

On the surface of mesoporous silica thin films (MSTF) which were fabricated by sol-gel approach there are existences of water and three different silanol types including chained, germinal and isolated silanol. Their amounts changes as a function of aging time of used sol solution, as confirmed by FT-IR. The adsorbed water generates ionic carriers such as H+ and OH- and passivates the Si dangling bonds at the interface of silicon wafer-MSTF. The ionic carriers can not only transport across the thickness of thin film to enhance the leakage current but also diffuse toward the silicon wafer-MSTF interface to depassivate Si dangling bonds. On the other hand, chained silanols or germinal silanols promote the moisture adsorption of MSTF and tend to form strongly hydrogen bonded systems with adsorbed water molecules resulting in very high dielectric constant. Isolated silanol, on the contrary, affects less on electrical properties of thin film.