• Journal of Microbiology and Biotechnology
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• 제17권5호
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• pp.721-727
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• 2007

Stability-enhanced mutants, H44, 11-94, 5A2-84, and F8, of L-threonine aldolase(L-TA) from Streptomyces coelicolor A3(2)(SCO1085) were isolated by an error-prone PCR followed by a high-throughput screening. Each of these mutant, had a single amino acid substitution: H177Y in the H44 mutant, A169T in the 11-94 mutant, D104N in the 5A2-84 mutant and F18I in the F8 mutant. The residual L-TA activity of the wild-type L-TA after a heat treatment for 20 min at $60^{\circ}C$ was only 10.6%. However, those in the stability-enhanced mutants were 85.7% for the H44 mutant, 58.6% for the F8 mutant, 62.1% for the 5A2-84 mutant, and 67.6% for the 11-94 mutant. Although the half-life of the wild-type L-TA at $63^{\circ}C$ was 1.3 min, those of the mutant L-TAs were longer: 14.6 min for the H44 mutant, 3.7 min for the 11-94 mutant, 5.8 min for the 5A2-84 mutant, and 5.0 min for the F8 mutant. The specific activity did not change in most of the mutants, but it was decreased by 45% in the case of mutant F8. When the aldol condensation of glycine and 3,4-dihydroxybenzaldehyde was studied by using whole cells of Escherichia coli containing the wild-type L-TA gene, L-threo-3,4-dihydroxyphenylserine(L-threo-DOPS) was successfully synthesized with a yield of 2.0 mg/ml after 20 repeated batch reactions for 100 h. However, the L-threo-DOPS synthesizing activity of the enzyme decreased with increased cycles of the batch reactions. Compared with the wild-type L-TA, H44 L-TA kept its L-threo-DOPS synthesizing activity almost constant during the 20 repeated batch reactions for 100 h, yielding 4.0 mg/ml of L-threo-DOPS. This result showed that H44 L-TA is more effective than the wild-type L-TA for the mass production of L-threo-DOPS.

• Environmental Engineering Research
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• 제10권5호
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• pp.257-263
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• 2005

A batch and a continuous type experiments were conducted to test the conditions for simultaneous phosphorus release and uptake, and denitrification, taking place in one process. The bacteria able to denitrify as well as to remove phosphorus were evaluated for the application to biological nutrient removal(BNR) process. In the batch-type experiment, simultaneous reactions of phosphorus release and uptake, and also denitrification were observed under anoxic condition with high organic and nitrate loading. However the rate and the degree of P release were lower than that occurred under anaerobic condition. BNR processes composed of anaerobic-anoxic-oxic(AXO), anoxic-anaerobic-oxic(XAO) and anoxic-oxic(XO) were operated in continuous condition. The anoxic reactors in each process received nitrate loading. In the AXO process, P release in anaerobic reactor and the luxury uptake in oxic reactor proceeded actively regardless to nitrate loading. However in XAO and XO processes, P release and luxury uptake occurred only with the nitrate loading less than $0.07\;kg{NO_3}^--N$/kgMLSS-d. With higher nitrate load, P release increased and the luxury uptake decreased. Therefore, it appeared that the application of denitrifying phosphorus-removing bacteria (DPB) to BNR process must first resolve the problem with decrease of luxury uptake of phosphorus in oxic reactor.

• 한국수소및신에너지학회논문집
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• 제20권2호
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• pp.151-160
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• 2009

Natural gas combustion characteristics of mass produced oxygen carrier particles were investigated in a batch type bubbling fluidized bed reactor. Five particles, NiO/bentonite, OCN601-650, OCN702-1100, OCN703-950, OCN703-1100 were used as oxygen carrier particles. Natural gas and air were used as reactants for reduction and oxidation, respectively. During reduction reaction, high fuel conversion and high $CO_2$ selectivity were achieved for most of oxygen carriers. During oxidation, NO emission was very low. These results indicate that inherent $CO_2$ separation and low NOx combustion are feasible for the natural gas fueled chemical-looping combustion system. Among the five oxygen carriers, OCN703-1100 particle was selected as the best candidate for demonstration of long-term operation in large-scale chemical-looping combustor from the viewpoints of fuel conversion, $CO_2$ selectivity, $CH_4$ concentration, and CO concentration.

• 한국물환경학회지
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• 제25권4호
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• pp.515-521
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• 2009

In this study, the applicability of $CaCO_3$ as a seed material for crystallization reaction was tested. $CaCO_3$ was ground to lesser than 425 mesh and was made to media mixed with binder. Batch experiment was to investigate the ${PO_4}^{3-}-P$ removal efficiency of different parameters such as $CaCO_3$ dosage and binder ratio, size, type and mass of media. In addition, the effect of phosphorus removal from wastewater was tested using a lab-scaled crystallization reactor. At the results of the batch test, phosphorus removals were improved with increasing $CaCO_3$ dosage and media mass but were decreased with increasing media size. Moreover, phosphorus removals were influenced by specific surface area but media type. The average T-P and ${PO_4}^{3-}-P$ removal efficiency in a lab-scaled crystallization reactor with $CaCO_3$ media for wastewater were shown to be 60.2% and 60.3% for 18 days of operation time.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1098-1108
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• 2008

Batch type and column type experiments were performed in order to predict adsorption and movement within soil. Clay minerals montmorillonite and kaolinite were respectively added to paraquat which is a cationic compound with long residual time, 2,4-D which is an anionic compound with relatively short residual time and napropamide which is an amphoteric compound. Therefore, it is very important to determine the movements of toxic pollutants in the ground soil to establish measures to prevent soil grounds contamination and to restore contaminated soils effectively, because contamination of soil is getting severe due to these toxic wastes, industrial waste water, and agricultural chemicals, etc. Therefore, in this study, we have carried out column and batch experiments by using general toxic organic compounds as test samples in order to restore contaminated soils effectively as well as to prepare a basic data to develop absorbents that will remove various toxic organic compounds, with a grandiose purpose to prevent contaminations of soil and grounds due to various toxic organic compounds.

• 한국안전학회지
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• 제14권1호
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• pp.78-85
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• 1999

The removal characteristics of H$_2$S from IGCC process over the natural manganese ore(NMO) containing several metal oxides($MnO_x$ : 51.85%, $FeO_y$ : 3.86%, CaO : 0.11%) were carried out in a batch type fluidized bed reactor(I.D.=40mm, height=0.8m). The $H_2S$ breakthrough curves were obtained as a function of temperature, initial gas velocity, initial gas concentration, and aspect ratio. The effect of particle size ratio and particle mixing fraction on $H_2S$ removal were investigated with binary system of different particle size. From this study, the adsorption capacity of $H_2S$ increased with temperature but decreased with excess gas velocity. The breakthrough time for $H_2S$ is reduced as the gas velocity is increased which leaded to gas by-passing and gas-solid contacting in a fluidized bed reactor. The results of the binary particle system with different size in batch experimental could predict to improve the behavior of continuous process of $H_2S$ removal efficiency. The natural manganese ore could be considered as potential sorbent in $H_2S$ removal.

• 생명과학회지
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• 제7권2호
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• pp.73-78
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• 1997

시판되고 있는 강염기성 $Cl^{-}$형의 음이온 교환수지를 사용하여 회분식 질산성 질소 제거 실험을 행하여 다음과 같은 결과를 얻었다. 수지의 종류에 따라 제거특성은 달랐다. 수지의 량이 많을수록, 계의 온도가 톡을 수록 질산성 질소이 제거효율은 높아졌다. 원수의 농도는 낮을수로그 원수의 공급유속은 느릴수록 질산성 질소의 제거효율이 좋았다. 음이온에 디한 겔형 이온교환수지인 SA 10A의 선택성은 ${SO_4}^{2-}>{No_3}^->NO_{2-}>{HCO_3}^-$로써 이온가 수가 높은 이온일수록 선택성이 증가하고 은 이온가인 경우에는 원자번호가 클수록 그리고 수화반경이 작을수록 선택성이 증가하였다. 증가하였다.

• 한국정밀공학회지
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• 제13권8호
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• pp.72-79
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• 1996

In a BAF(Batch Annealing Furnace), various studies have been pursued in order to reduce energy consumption rate to improve productivity and to stabilize the properties of products. The purpose of this study was to investigate the effects of both the atmospheric gas and convector plate shapes on the augmentation of heat transfer. The use of hydrogen instead of nitrogen as an atmospheric gas, combined with high convection in the BAF, has shown that considerable increases in furnace out put and significantly improved material quality are attainable. Because convector plate shapes make the atmosheric gas easily flow density, high diffusivity and reducing character of hydrogen, a better heat transfer rates resulting in uniform material temperature distribution and improved coil surface quality can be achieved. Also, it was found that the closed convector plate took more time for the annealing cycle time than the other plate type(open-type)by about ten hours.

• 상하수도학회지
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• 제24권6호
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• pp.775-788
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• 2010

The decomposition of 2,4,6-trinitrotoluene (TNT) and the mass balance of nitrogen (N) species as products were investigated in a UV/H2O2system by varying pH, concentrations of $H_2O_2$, and $O_2$. All experiments were conducted in a semi-batch system employing a 50 mL reaction vessel and a coil-type quartz-tube reactor. In contrast with previous studies employing batch mode, TNT decomposition in the semi-batch mode was proportionally enhanced by increasing $H_2O_2$ concentration to 10 mM (0.034%), indicatingthat an inhibitory effect of excess $H_2O_2$on hydroxyl radical (${\cdot}OH$) can be negligible. N compounds are released as $NO_2^-$ in the early stages of the reaction, but $NO_2^-$ is rapidly oxidized to $NO_3^-$ by means of ${\cdot}OH$. $NH_4^+$ was also detected in this study and showed gradually the increase with increasing reaction time. In this study, $NH_4^+$ production can involve the reduction of nitro group of TNT concurrent with the production of $NO_3^-$. Of the N species originating from TNT decomposition, 12 ~ 72% were inorganic forms (i.e. [$NO_3^-$] + [$NO_2^-$] + [$NH_4^+$]). This result suggests that the large remaining N portions indicate that unidentified N compounds can exist.

• 멤브레인
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• 제24권1호
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• pp.20-30
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• 2014

C/N 비가 낮은 농촌마을 하수의 고도처리를 위하여 $0.4{\mu}m$의 세공크기를 갖고 있는 평막이 침지된 연속회분식 반응기를 사용하였다. 분말활성탄의 투입, 폭기량 및 유입 유기물 농도가 처리효율과 여과 성능에 미치는 영향을 조사하였다. 54일 이내의 조업 초기에서는 C/N 비가 증가할수록 COD, T-N 및 T-P의 제거율과 MLSS 농도는 증가하였다. 조업 89일 후의 COD, T-N 및 T-P의 제거율은 각각 97.1%, 75.0% 및 48.3%이었다. 막여과에 의해 처리수에서 SS는 검출되지 않았으며, T-P의 제거율이 낮게 나온 이유는 과잉의 슬러지를 배출하지 않았기 때문이다. 분말활성탄을 투여한 경우 조업이 진행됨에 따라 분말활성탄의 혼합강도와 충돌빈도가 증가하여 슬러지의 입자크기가 감소하였으며, 이로 인해 분말활성탄을 투여하지 않은 경우에 비해 TMP 상승이 크게 나타났다.