• 대한화장품학회지
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• 제11권1호
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• pp.1-12
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• 1985

A strain of Pseudomonas aeruginosa was isolated from the spoiled product and its characteristics on various formaldehyde-releasing preservatives were investigated. This strain, P. aeruginosa FR, could utilize 1.0% of imidazolidinyl urea and 0.2% of DMDM hydantoin as a sole carbon and nitrogen source in the minimal salts medium. With the growth of the strain in minimal salts medium containing imidazolidinyl urea, formic acid was initially accumulated according to the decrease of formaldehyde concentration. It was suggested that formaldehyde dehydrogenase was involved in this oxidation process and could catalyze formaldehyde, imidazolidinyl urea, DMDM hydantoin and quaternium-15, but not bronopol. MICs of this strain to each preservation were 0.03% in formaldehyde, 1.0% in imidazolidinyl urea, 0.2% in DMDM hydantoin, 0.2% in quaternium-15 and 0.1% of EDTA-2Na. But the MICs were diminished about ten times when 0.01% of EDTA-2Na was added to the preservative systems. In actual challenge test, the eyeliner and the pack which contained paraben and imidazolidinyl urea were not able to be protected from this strain, but when 0.05% EDTA-2Na was added the products were sufficiently preserved.

• 한국의류학회지
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• 제22권7호
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• pp.843-850
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• 1998

The purpose of this study is the investigation of chemical properties of wool treated with oxidants and protease at low temperature. The chemical degradation of the fibers were investigated by measuring $\alpha$-amimo acid contents and FT-IR analysis. In addition, urea-hydrogensulfite solubility was measured to compare to the oxidation and protease treated wool. The results were as follows. 1) By the oxidation of wool, cystine is oxidised to cysteic acid by way of the intermediate oxides, cystine-S-monooxide and cystine-S-dioxide, in the case hydrolysis catalysed by the protease catalyse. Also, $\alpha$-amimo acid contents is increased, and urea-hydrogensulfite solubility was lower than that of untreated wool. This chemical degradation of wool was occurred due to oxidate hydrolysis in the order of permonosulfate>dichloroisocyanuric acid$\geq$chlorine. 2) The chemical degradation of wool was accelerated by the protease treatment of oxidized wool. Oxidation of wool is considered to make the fiber more susceptibled to enzymatic attact by opening disulphide bond within wool. Enzymatic attact was effectively directed to the wool oxidised by permonosulfate.

• Bulletin of the Korean Chemical Society
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• 제25권10호
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• pp.1499-1502
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• 2004

An amperometric biosensor based on carbon paste electrodes (CPEs) for the determination of urea was constructed by enzyme (urease/GL-DH)-modified method. Urea was hydrolyzed to ${NH_4}^+$ by catalyzing urease onto the enzyme-modified electrode surface in sample solution. In the presence of ${\alpha}$-ketoglutarate and reduced nicotinamide adenine dinucleotide(NADH), a liberated ${NH_4}^+$ produce to L-glutamate and $NAD^+$ by Lglutamate dehydrogenase (GL-DH). After the chemical reaction was proceeded, the electrochemical reaction was occurred that an excess of the NADH was oxidized to $NAD^+$. The oxidation current of NADH was monitored at +1.10 volt vs. Ag/AgCl. An optimum conditions of biosensor were investigated: The optimum pH range for catalyzed hydrolysis reaction of urea was pH 7.0-7.4. The linear response range and detection limit were $2.0\;{\times}\;10^{-5}{\sim}2.0\;{\times}\;10^{-4}M\;and\;5.0\;{\times}\;10^{-6}M$, respectively. Another physiological species did not interfere, except L-ascorbic acid.

• 센서학회지
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• 제19권3호
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• pp.176-183
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• 2010

It is considered that the urea injection DeNOx SCR(selective catalytic reduction) system is the only promising method to satisfy the worldwide NOx emission standards. As for the theoretical aspect, reactants of NO and $NO_2$ with $NH_3$ produce $H_2O$, $N_2$ and $O_2$ which do not harm human beings and environmental as well. The realization of maximum NOx conversion (without using a post oxidation catalyst) is only possible with closed loop controlled urea dosing. It means built-in $NH_3$ gas sensor have to be developed for detecting accurate $NH_3$ concentration for the feedback system. Using YSZ(yttria-stabilized zirconia) as a solid state electrolyte and $In_2O_3$ as a sensing material, this paper aims to study dependable $NH_3$ gas sensor for the promising solution of DeNOx technology, which have a reproducible electric output signal, a high sensitivity and fast response.

• 한국가스학회지
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• 제14권2호
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• pp.7-14
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• 2010

메탄의 부분산화에 의하여 합성가스를 제조하였다. 저렴하며 본 반응에 활성이 좋은 것으로 알려진 Ni을 활성 물질로, 우수한 산소 저장능력과 높은 산화 환원 특성을 지닌 $CeO_2$를 담체로 하여, 함침법과 우레아법으로 촉매를 제조하였다. 반응은 고정층 반응기를 이용하여 1 atm, $650{\sim}800^{\circ}C$에서 실시하였다. 표면적 측정 장치를 이용하여 촉매 제조법에 따른 표면적 차이를 비교해 본 결과 우레아법으로 제조한 촉매가 함침법으로 제조한 촉매보다 표면적이 약 11배 이상 큼을 알 수 있었고, SEM으로 표면 구조를 조사해본 결과 우레아법으로 제조한 촉매가 훨씬 더 미세하고 균일함을 알 수 있었다. 우레아법으로 제조한 촉매가 함침법으로 제조한 촉매보다 더 높은 메탄 전환율 및 합성가스 선택도를 나타내었다. 본 반응의 문제점인 탄소 침적을 줄이기 위하여 La을 첨가하여 탄소 침적에 미치는 La의 영향을 알아보았다. TGA(열중량 분석기) 분석 결과 La이 첨가되지 않은 촉매에는 약 16%의 탄소 침적이, La을 첨가한 촉매에는 약 2%의 탄소 침적이 형성되었다. 따라서 La 첨가는 탄소 침적을 줄여서 촉매 비활성화를 막은 것으로 추정된다.

• Applied Biological Chemistry
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• 제47권4호
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• pp.384-389
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• 2004

$100^{\circ}C$에서 반응시켜 2, 4, 6, 8시간의 갈변도 변화는 ${\beta}-1,4-mannobiose$와 urea의 반응혼합물이 시간의 경과함에 따라 강한 착색도의 증가를 나타냈으나 phenylthiourea, thiourea의 반응액은 착색속도가 늦었다. 같은 조건하에서 $Gal^3Man_4$와 urea 관련화합물의 각 반응혼합물의 갈변도를 나타낸 것으로 urea가 강한 착색도의 중가를 보였고 phenylthiourea, thiourea의 반응액은 비교적 높은 착색도를 보였다. DP 7의 galactosyl mannooligosaccharide와의 각 반응혼합물의 갈변도는 urea의 반응액이 강한 착색을 보였으며 phenylthiourea, thiourea의 반응액의 순으로 착색를 나타내었다. 반응혼합물의 TLC 결과에서 ${\beta}-1,4-mannobiose$와 urea의 반응혼합물 이외에 phenylthiourea, thiourea의 반응액은 새로운 화합물이 생성되었고, $Gal^3Man_4$와 D.P 7 galactosyl manooligosaccharide와의 반응혼합물에서는 모든 반응액에서 새로운 화합물이 출현되었다. 반응혼합물의 환원력은 urea관련화합물 중에서 특히 phenylthiourea, thiourea가 ${\beta}-1,4-mannobiose,\;Gal^3Man_4$, DP 7의 galactosyl manooligosaccharide와의 반응혼합물에서 강한 환원력이 나타났다. Linoleic acid에 대한 반응혼합물의 항산화력 측정에서 ${\beta}-1,4-mannobiose$와 thiourea의 반응혼합물의 항산화력이 Ascorbic acid(AsA)수준의 항산화력을 나타내었고, $Gal^3Man_4$와 thiourea, phenylthiourea의 반응혼합물은 AsA와 유사한 항산화능을 나타내었다. DP 7의 galactosyl manooligosaccharide와 thiourea, phenylthiourea의 반응혼합물의 항산화력은 AsA에 미치지는 못하였다. ${\beta}-1,4-Mannobiose$와 thiourea, phenylthiourea의 반응혼합물이 강한 전자공여능을 나타내고 있고, $Gal^3Man_4$와 phenylthiourea의 반응혼합물 및 D.P 7의 galactosyl manooligosaccharide와 phenylthiourea와의 반응혼합물이 전자공여능을 나타내고 있다.

• 한국자동차공학회논문집
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• 제22권4호
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• pp.111-120
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• 2014

The aim of this study is to develop an integrated urea-SCR catalytic filter system for reducing soot and $NO_X$ emissions simultaneously in diesel engines. In this study, the characteristics of exhaust emissions relative to reactive activation temperature under four kinds of engine loads are experimentally investigated by using a four-cycle, four-cylinder, direct injection type, water-cooled turbo intercooler ECU common-rail diesel engine with the integrated urea-SCR $MnO_2-V_2O_5-WO_3/TiO_2/SiC$ catalytic filter system operating at three kinds of engine speeds. The urea-SCR reactor is used to reduce $NO_X$ emissions, and the catalytic filter system is used to reduce soot emissions. The reactive activation temperature is very important for reacting a reducing agent with exhaust emissions. The reactive activation temperatures in this experiment is applied to 523, 573 and 623 K. The fuel is sprayed by the pilot and main injections at the variable injection timing between BTDC $15^{\circ}$ and ATDC $1^{\circ}$ according to experimental conditions. It is found that the $NO_X$ conversion rate is the highest as 83.9% at the reactive activation temperature of 523 K in all experimental conditions of engine speed and load, and the soot emissions shown by the average reduction rate of approximately 93.3% are almost decreased below 0.6% in all experimental conditions regardless of reactive activation temperatures. Also, the THC and CO emissions by oxidation reaction of Mn, V and Ti are shown in the average reduction rates of 70.3% and 38% regardless of all experimental conditions.

• 한국수소및신에너지학회논문집
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• 제17권1호
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• pp.21-30
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• 2006

[ $M/Fe_2O_3$ ] (M=Rh, Ce and Zr) mixed oxides were prepared using urea method to develop a medium for chemical hydrogen storage by their redox cycles. And their redox behaviors by repeated cycles were studied using temperature programmed reaction(TPR) technique. Additives such as Rh, Ce and Zr were added to iron oxides in order to lower the reaction temperature for reduction by hydrogen and re-oxidation by water-splitting. From the results, concentration of urea used as a precipitant had little effect on particle size and reduction property of iron oxide. TPR patterns of iron oxide consisted of two reduction peaks due to the course of $Fe_2O_3\;{\rightarrow}\;Fe_3O_4\;{\rightarrow}\;Fe$. The results of repeated redox tests showed that Rh added to iron oxide have an effect on lowering the re-oxidation temperature by water-splitting. Meanwhile, Ce and Zr additives played an important role in prevention of deactivation by repeated cycles. Finally, Fe-oxide(Rh, Ce, Zr) sample added with Rh, Ce and Zr showed the lowest re-oxidation temperature by water-splitting and maintained high $H_2$ recovery in spite of the repeated redox cycles. Consequently, it is expected that Fe-oxide(Rh, Ce, Zr) sample can be a feasible medium for chemical hydrogen storage using redox cycle of iron oxide.

• 한국환경농학회지
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• 제42권4호
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• pp.418-426
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• 2023

This study focused on nitrous oxide, a major greenhouse gas produced in agricultural settings through bacterial nitrogen oxidation in aerobic soil. Nitrogen fertilizer in farmland is identified as a primary source of nitrous oxide. The importance of reducing excess nitrogen in soil to mitigate nitrous oxide production is well-known. The study investigated the use of liquefied pig manure as an alternative to urea fertilizer in conventional agriculture. Results showed a more than two-fold reduction in nitrous oxide emissions in pepper cultivation areas with liquefied pig manure compared to that with urea fertilizer. The population of Nitrosospira, a nitrous oxide-producing bacterium, decreased by over 10% with liquefied pig manure. Additionally, nirK and nosZ, which are related to the denitrification process, significantly increased in the urea fertilizer group, whereas levels in the liquefied pig manure group resembled those with no nitrogen treatment. In conclusion, the experiment confirmed that liquefied pig manure can serve as an eco-friendly nitrogen fertilizer, significantly reducing nitrous oxide production, a major contributor to the atmospheric greenhouse effect.

• Bulletin of the Korean Chemical Society
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• 제18권11호
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• pp.1149-1152
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• 1997

An enzyme electrode for the amperometric measurement of urea was prepared by co-immobilizing L-glutamate dehydrogenase and urease onto an Immobilon-AV affinity membrane attached to a glassy carbon electrode. The reduced nicotinamide adenine dinucleotide(NADH) was used as the electroactive species. The electrochemical oxidation of NADH was monitored at +1.0 volt vs. Ag/AgCl. The enzyme-immobilized electrode was linear over the range of 2.0 × 10-5 to 2 × 10-4 M. The response time of the electrode was approximately 3 min. and the optimum pH of the enzyme immobilized membrane was pH 7.4-7.6 (Dulbcco's buffer solution). It was stable for at least two weeks or 50 assays. There was no interference from other physiological species, except from high levels of ascorbic acid.