• 한국진공학회:학술대회논문집
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• 한국진공학회 2007년도 제32회 학술대회 초록집
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• pp.84-84
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• 2007

• Journal of Microbiology and Biotechnology
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• 제23권12호
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• pp.1699-1707
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• 2013

During the fermentative production of 1,3-propanediol under high substrate concentrations, accumulation of intracellular 3-hydroxypropionaldehyde will cause premature cessation of cell growth and glycerol consumption. Discovery of oxidoreductases that can convert 3-hydroxypropionaldehyde to 1,3-propanediol using NADPH as cofactor could serve as a solution to this problem. In this paper, the yqhD gene from Klebsiella pneumoniae DSM2026, which was found encoding an aldehyde reductase (KpAR), was cloned and characterized. KpAR showed broad substrate specificity under physiological direction, whereas no catalytic activity was detected in the oxidation direction, and both NADPH and NADH can be utilized as cofactors. The cofactor binding mechanism was then investigated employing homology modeling and molecular dynamics simulations. Hydrogen-bond analysis showed that the hydrogen-bond interactions between KpAR and NADPH are much stronger than that for NADH. Free-energy decomposition dedicated that residues Gly37 to Val41 contribute most to the cofactor preference through polar interactions. In conclusion, this work provides a novel aldehyde reductase that has potential applications in the development of novel genetically engineered strains in the 1,3-propanediol industry, and gives a better understanding of the mechanisms involved in cofactor binding.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 Proceedings of The 6th korea-china joint workshop on nuclear waste management
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• pp.39-50
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• 2005

Electrolytic reduction of uranium oxide to uranium metal was studied in a $LiCl-Li_{2}O$ molten salt system. The reduction mechanism of the uranium oxide to a uranium metal has been studied by means of a cyclic voltammetry. Effects of the layer thickness of the uranium oxide and the thickness of the MgO on the overpotential of the cathode and the anode were investigated by means of a chronopotentiometry. From the cyclic voltamograms, the decomposition potentials of the metal oxides are the determining factors for the mechanism of the reduction of the uranium oxide in a $LiCl-3\;wt{\%} Li_{2}O$ molten salt and the two mechanisms of the electrolytic reduction were considered with regards to the applied cathode potential. In the chronopotentiograms, the exchange current and the transfer coefficient based on the Tafel behavior were obtained with regard to the layer thickness of the uranium oxide which is loaded into the porous MgO membrane and the thickness of the porous MgO membrane. The maximum allowable currents for the changes of the layer thickness of the uranium oxide and the thickness of the MgO membrane were also obtained from the limiting potential which is the decomposition potential of LiCl.

• 한국주조공학회지
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• 제23권5호
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• pp.268-275
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• 2003

The mechanism of the hydrogen gas pore formation was investigated in Lost Foam Casting of Al-alloy by reduced pressure test and real casting. The hydrogen gas pick-up was affected by the formed gas during the decomposition of polystyrene in addition to the liquid product. It depended on pouring temperature and a proper temperature of metal front gave the minimum hydrogen pick-up. At a low pouring temperature, the hydrogen went into the melt mainly from entrapped liquid product of polystyrene but pores were formed from the gas as well as the liquid product at a high pouring temperature. The mold flask evacuation down to 710torr decreased the gas porosity down by around 0.4% vol%. The entrapped decomposition product of polystyrene in the melt was observed through the visualization of filling behavior of Al alloy-melt with the high speed camera.

• 대한원격탐사학회지
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• 제29권1호
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• pp.57-68
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• 2013

20세기 후반부터 유부도 주위에서 하구언 축조 등 비교적 큰 규모의 간척사업들이 진행되었다. 이러한 간척사업의 시작으로 인공구조물들이 연안에 축조됨에 따라 주변 해역의 해류, 조위 및 조류의 변화를 야기하여 퇴적 및 침식으로 인한 연안지형의 변화가 예상된다. 따라서 이 연구에서는 유부도 조간대를 포함하는 Landsat TM/ETM+자료를 1998년부터 2012년까지 획득한 후 waterline 기법을 적용하여 인공구조물 축조에 의한 지형변화를 탐지하였다. 그 결과 유부도의 동쪽, 북동쪽, 서쪽 조간대에서 주로 퇴적이 일어났으며 그 면적이 약 4.5 $km^2$ 이상 되었다. 한편, RADARSAT-2의 완전편파 SAR자료에 Freeman-Durden decomposition을 적용하여 퇴적이 뚜렷이 일어난 지역에 대한 산란특성을 분석하였다. 그 결과 동쪽 퇴적지역은 서쪽 및 북동쪽의 퇴적지역과는 다른 산란특징이 관찰되었으며, 이는 퇴적환경의 차이로 인해 다른 종류의 퇴적물이 퇴적되어 발생한 것으로 여겨진다.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.2013-2018
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• 2014

The adsorption and decomposition of trimethylene oxide ($C_3H_6O$) molecule on the Al(111) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employed a supercell ($6{\times}6{\times}3$) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between $C_3H_6O$ molecule and Al atoms induce the C-O bond breaking of the ring $C_3H_6O$ molecule. Subsequently, the dissociated radical fragments of $C_3H_6O$ molecule oxidize the Al surface. The largest adsorption energy is about -260.0 kJ/mol in V3, V4 and P2, resulting a ring break at the C-O bond. We also investigated the decomposition mechanism of $C_3H_6O$ molecules on the Al(111) surface. The activation energies ($E_a$) for the dissociations V3, V4 and P2 are 133.3, 166.8 and 174.0 kJ/mol, respectively. The hcp site is the most reactive position for $C_3H_6O$ decomposing.

• Bulletin of the Korean Chemical Society
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• 제24권3호
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• pp.350-356
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• 2003

The mechanism of the decomposition of a bronchodilator, S-nitroso-N-acetyl-D,L-penicillamine (SNAP) by a bronchoconstrictor, aqueous sulfite, has been investigated in detail. The decomposition was studied using a conventional spectrophotometer at 336 nm over the ranges: 0.010 ≤ $[S^{IV}]_T$ ≤ 0.045 mol $dm^{-3}$, 3.96 ≤ pH ≤ 6.80 and 15.0 ≤ θ≤ 30.0 ℃, 0.60 ≤ I ≤ 1.00 mol $dm^{-3}$, and at ionic strength 1.00 mol $dm^{-3}$ (NaCl). The rate of reaction is dependent on the total sulfite concentration and pH in a complex manner, i.e., $k_{obs}\;=\;k_1K_2[S^{IV}]_T/ ([H^+]\;+\;K_2)$. At 25.0 ℃, the second order rate constant, $k_1$, was determined as $12.5\;{\pm}\;0.15\;mol^{-1}\;dm^3\;s^{-1}$. ${\Delta}H^{neq}\;=\;+32\;{\pm}\;3 kJ\;mol^{-1}\;and\;{\Delta}S^{\neq}\;=\;-138\;{\pm}\;13\;J\;mol^{-1}K^{-1}$. The N-nitrosohydroxylamine-N-sulfonate ion was detected as an intermediate before the formation of any of the by-products, namely, N-acetyl-D,L-penicillamine. The effect of concentration of aqueous copper(Ⅱ) ions on this reaction was also examined at pH 4.75, but there was no dependence on $[Cu^{2+}]$. In addition, the $pK_a$ of SNAP was determined as 3.51 ± 0.06 at 25.4 ℃ [I = 1.0 mol $dm^{-3}$ (NaCl)].

• 한국항공우주학회지
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• 제47권10호
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• pp.720-727
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• 2019

하이브리드 로켓 연소의 저주파수 연소불안정은 고체연료의 열적지연(Thermal Lag)과 경계층 유동 변화에 의한 열전달 진동의 공진에 의해 발생한다. 본 연구는 연료 표면 근처의 경계층 유동의 교란이 어떤 물리적 과정에 의해 발생하여 연소불안정으로 발달하는지를 실험적으로 확인하였다. 특히 산화제의 스월 분사는 연소 안정화에 매우 큰 기여를 하므로 스월 강도를 증가시키며 경계층의 변화와 연소불안정의 발생과정을 연구하였다. 경계층 섭동을 확인하기 위하여 연소 유동장을 가시화하였고 이미지에 대한 POD(Proper Orthogonal Decomposition) 분석을 시도하였다. 스월 강도가 증가할수록 500Hz 대역 고주파수 p', q'의 결합이 약해지며 열적지연과 유사한 주파수 특성을 갖는 Rayleigh Index의 섭동 발생도 약해져 경계층 진동의 발생이 점차 감소하는 것을 관찰하였다. 따라서 고주파수 p', q'의 주기적인 결합에 의한 축 방향 경계층 진동이 나타나면 열적지연 주파수와 공진에 의한 연소불안정이 발생함을 확인하였다.

• 한국분말재료학회지
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• 제9권6호
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• pp.422-432
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• 2002

Mechanically driven decomposition of intermetallics during mechanical milling(MM 1 was investigated. This process for Fe-Ce and Fe-Sn system was studied using conventional XRD, DSC, magnetization and alternative current susceptibility measurements. Mechanical alloying and milling form products of the following composition (in sequence of increasing Gecontent): $\alpha$(${\alpha}_1$) bcc solid solution, $\alpha$+$\beta$-phase ($Fe_{2-x}Ge$), $\beta$-phase, $\beta$+FeGe(B20), FeGE(B20), FeGe(B20)+$FeGe_2$,$FeGe_2$,$FeGe_2$+Ge, Ge. Incongruently melting intermetallics $Fe_6Ge_5$ and $Fe_2Ge_3$ decompose under milling. $Fe_6Ge_5$ produces mixture of $\hat{a}$-phase and FeGe(B20), $Fe_2Ge_3$ produces mixture of FeGe(B20) and $FeGe_2$ phases. These facts are in good agreement with the model that implies local melting as a mechanism of new phase for-mation during medchanical alloying. Stability of FeGe(B20) phase, which is also incongruently melting compound, is explained as a result of highest density of this phase in Fe-Ge system. Under mechanical milling (MM) in planetary ball mill, FeSn intermetallic decomposes with formation $Fe_5Sn_3$ and $FeSn_2$ phases, which have the biggest density among the phases of Fe-Sn system. If decomposition degree of FeSn is relatively small(<60%), milled powder shows superparamagnetic behavior at room temperature. For this case, magnetization curves can be fitted by superposition of two Langevin functions. particle sizes for ferromagnetic $Fe_5Sn_3$ phase determined from fitting parameters are in good agreement with crystalline sizes determined from XRD data and remiain approximately chageless during MM. The decomposition of FeSn is attributed to the effects of local temperature and local pressure produced by ball collisions.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.135-140
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• 2015

유도 결합 플라즈마를 활용하여 $Ar/CO_2$ 혼합가스에서 이산화탄소를 분해하는 연구이다. 고밀도 플라즈마를 발생시키기 위해 Ar 가스를 첨가하였고 이산화탄소 분해율을 측정하기 위해 광학적 광량 측정법을 사용 하였다. 유도 결합 플라즈마를 방전시키고 인가 전력, 압력, 혼합가스 비율을 변경하가며 단일 랭뮤어 프로브를 이용해 플라즈마 변수를 얻고 방출 분광기로 얻은 빛의 스펙트럼을 이용하여 분해율을 측정하였다. 측정된 플라즈마 변수로부터 $CO_2$ 유도 결합 플라즈마의 소스 특성을 확인했고 $CO_2$ 분해 메커니즘은 플라즈마 변수에 직접적인 영향을 받기 때문에 그 상관관계를 분석하였다.