• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.139-145
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• 2005

[ $SnO_x$ ] films on the flexible substrate of PET film were prepared at ambient temperature under a $(CH_3)_4Sn(TMT: tetra-methyl tin)-H_2-O_2$ atmosphere in order to obtain transparent conductive polymer by using ECR-MOCVD(Electro Cyclotron Resonance Metal Organic Chemical Yfpor Deposition) system. The prepared $SnO_x$ thin films show generally over $90\%$ of optical transmittance at wavelength range of 380-780nm and about $1\times10^{-2\~3}ohm{\cdot}cm$ of electrical resistivity. In the present study, effects of $O_2/TMT\;and\;H_2/TMT$ mole ratio on the properties of $SnO_x$ films are investigated and the other process parameters such as microwave power, magnetic current power, substrate distance and working pressure are fixed. Based on our experimental results, the $SnO_x$ film composition ratio of Sn and O directly influences on the electrical and optical properties of the films prepared. The $SnO_x$ film with low electric resistivity and high transmittance could be obtained by controlling the process parameters such as $O_2/TMT\;and\;H_2/TMT$ mole ratio, which play an important role to change the composition ratio between Sn and O. An increase of $O_2/TMT$ mole ratio brought on the increases 0 content in the $SnO_x$ film. On the other hand, an increase of $H_2/TMT$ mole ratio lead to decreases the oxygen content in the film. The optimized composition ratio of oxygen : tin Is determined as 2.4: 1 at $O_2/TMT$ of 80 and $H_2/TMT$ of 40 mole ratio, respectively.

• Food Science and Industry
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• v.53 no.1
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• pp.2-32
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• 2020

In recent years, significant importance has been given to chitooligosaccharides (COS) due to its potent notable biological applications. COS can be derived from chitosan which is commonly produced by partially hydrolyzed products from crustacean shells. In order to produce COS, there are several approaches including chemical and enzymatic methods which are the two most common choices. In this regard, several new methods were intended to be promoted which use the enzymatic hydrolysis with a lower cost and desired properties. Hence, the dual reactor system has gained more attention than other newly developed technologies. Enzymatic hydrolysis derived COS possesses important biological activities such as anticancer, antioxidant, anti-hypersentive, anti-dementia (Altzheimer's disease), anti-diabeties, anti-allergy, anti-inflammatory, etc. Results strongly suggest that properties of COS can be potential materials for nutraceutical, pharmaceutical, and cosmeceutical product development.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.19-19
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• 2011

수중방전은 다양한 라디칼을 직접 물 속에서 발생시키기 때문에 수처리 공정에 다양한 응용이 가능하다. 특히, 최근에 선박평형수 등의 살균이 국제적인 이슈가 되고 있고, 2017년까지는 모든 선박에 살균을 위한 수처리 설비가 의무화된다. 본 연구에서는 염분이 있는 수체에서의 방전공정을 연구하고 이를 수처리공정에 적용할 수 있는 방법에 대해 연구하였다. 해수의 경우 전도도가 53mS로 자유로운 전하의 이동이 가능하기 때문에 일반적인 민물방전의 전원과 전극 등으로는 방전을 할 수 없다. 이에 세라믹과 금속의 이중구조로 되어 있는 모세관전극을 개발하여 전도성이 있는 수체에서의 방전을 이루었다. 전원장치로는 60 Hz, 380 V를 1차측에 인가하여 2차측에서 약 3 kV, 10 kW의 파워가 발생하는 12위상차 교류전원장치를 개발하여 사용하였다. 모세관 내부에 전압이 인가되면 전류가 발생하여 joule heating에 의하여 모세관 내부에 기포가 형성된다. 이 때, 전류의 단락이 이루어지면서 고전압쪽에 전하가 축적되며 기포내부의 E-field가 상승한다. 이후 기포 내에서 방전이 개시되며 각종 라디칼을 생성한다. 방전에 의해 생성되는 산화제로는 오존, OH라디칼, 과산화수소 등이 있으며, 해수에서는 Cl-의 결합에 의하여 Cl2 가스가 발생한다. 약 30,000 J/L의 체적에너지에 대하여 생성되는 총염소의 농도는 2.5 mg/L이다. 수중방전의 적용대상으로 선박평형수, 멤브레인과의 결합, 용존기포부상법을 선정하여 적용가능성을 연구하였다. 먼저 선박평형수 살균처리를 위해 해수의 처리유량을 20 lpm으로 유지하고 대장균, 바실러스, 조류(테트라셀미스) 등을 투입하여 전극 12개가 삽입된 12위상차 플라즈마 반응기를 통과시켰더니, 약 30,000 J/L의 체적에너지에 대하여 1일 후의 살균력이 각각 99.99, 99.99, 99.9%의 살균력을 나타내었다. 이는 국제해사기구에서 권장하는 살균수준인 99.9%를 초과하는 수치이다. 플라즈마를 이용한 해수살균공정의 안정적 운전을 위해 후단에 UF멤브레인을 추가하여 잔류생존 미생물을 제거할 수 있다. 이를 위해 플라즈마가 후단의 멤브레인 운전에 미치는 영향을 평가하였다. 카올린과 탄산칼슘을 오염원으로 각각 투입하여 멤브레인으로 처리를 하였을 때, 방전 직후 멤브레인에 걸리는 막간압력차가 약 30% 감소하였는데, 이는 막에 형성된 파울링이 방전에 의해 제거된 것으로 평가할 수 있다. 수중방전은 다양한 산화제를 생성함과 동시에 미세기포를 발생시키는데 이는 수중유기물의 부상분리에 적용될 수 있다. 방전모세관전극의 내부직경을 1 mm로 유지하고, 60 Hz, 교류전원으로 방전한 결과 평균입경 44 um의 기포를 발생시켰고, 이는 일반적으로 용존공기부상법에 사용되는 기포의 크기와 일치한다.

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.172-178
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• 2014

In this work, we describe an electrochemical immunosensor for simple, fast and quantitative detection of a urinary hippuric acid (HA). Urinary HA, of molecular weight 180 DA, is one of the major metabolites and biological indicators in toluene-exposed humans. Simple and ubiquitous monitoring of exposure to toluene is very important in occupational health care. We propose the electrochemical immunoassay based on the dopamine-antigen conjugate for detecting hippuric acid. Our electrochemical immunoassay system employs a conjugate of dopamine (DA) as an electrochemical active molecule and hippuric acid (HA) as an antigen. As an electrochemical aspect, dopamine (DA) containing two hydroxyl group can show excellent redox signal. Also, dopamine-tethered hippuric acid (DA-HA) shows the reversible redox signal in the immunoassay. The competition between HA and DA-HA generated electric signals proportional to HA concentration. The electrochemical immunoassay was performed with DA-HA on the screen printed carbon electrodes (SPCEs), and then applies the mixture antigen (HA) and HA-antibody. The electrical signals were proportional to HA in the range of 0.010~2.500 mg/mL which is enough range to be used for the point-of-care.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.51-62
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• 1990

Pentadentate Schiff base cobalt(II) complexes; Co(II)(Sal-DET) and Co(II)(Sal-DPT) were synthesized and these complexes were allowed to react with dry to form oxygen adducts of cobalt(II) complexes such as [Co(III)(Sal-DET)]$_2O_2$ and [Co(III)(DPT)]$_2O_2$ in aprotic solvents. These complexes have been identified by IR spectra, TGA, DSC, magnetic susceptibility measurements, and elemental analysis. It has been found that the oxygen adadduct complexes of $\mu$-peroxo type have hexaccordinated octahedral configuration with pentadentate schiff base cobalt(II) and oxygen, but the mole ratio of oxygen to cobalt(III) complexes of first step for oxygen adduct formation reaction of cobalt(II) complexes in aprotic solvents are 1:1. The redox reaction processes of Co(II)(Sal-DET), Co(II)(Sal-DPT), and oxygen adduct of cobalt(II) complexes were investigated by cyclic voltammetry and DPP method with glassy carbon electrode in 0.1M TEAP-DMSO and 0.1M TEAP-pyridine. As a result the reduction reaction processes of Co(III)/Co(II) and Co(II)/Co(I) for cobalt(II) complexes and oxygen adducts of cobalt(II) complexes are two irreversible steps of one eletron process, and reaction processes of oxygen for oxygen adducts complexes were quasireversible and redox range of potential was $E_{pc}$ = -0.97V∼-0.86V and $E_{pa}$ = -0.87V ∼ 0.64V.

• Membrane Journal
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• v.20 no.1
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• pp.29-39
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• 2010

This study focuses on the modeling of DMFC to predict the characteristics and to improve its performance. This modeling requires deep understanding of the design and operating parameters that influence on the cell potential. Furthermore, the knowledge with reference to electrochemistry, transport phenomena and fluid dynamics should be employed for the duration of mathematical description of the given process. Considering the fact that MEA is the nucleus of DMFC, special attention was made to the development of mathematical model of MEA. Multiscale modeling is comprised of process modeling as well as a computational fluid dynamics (CFD) modeling. The CFD packages and process simulation tools are used in simulating the steady-state process. The process simulation tool calculates theelectrochemical kinetics as well as the change of fractions, and at the same time, CFD calculates various balance equations. The integrated simulation with multiscal modeling explains experimental observations of transparent DMFC.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.111-111
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• 2012

나노테크놀로지는 종래의 가공으로는 얻기 힘들었던 섬유가공 효과를 간단하게 할 수 있는 기술이다. 현재 각국의 기능성 나노 가공제를 섬유에 응용하는 나노 테크놀로지는 현재 공업 생산되고 있는 면, 모, 견 등의 천연섬유 및 polyester, Nylon 등의 합성섬유의 원단에 적용하는 데서 출발하고 있다. 이러한 나노기술은 기존의 설비와 물을 사용하는 것이 큰 특징이고, 특별한 기계장치가 필요하지 않으며, 소규모의 실험장비만 있어도 현장투입이 가능한 나노입자의 제조가 가능하기 때문에 대량생산이 용이하고 설비투자는 원칙적으로 필요하지 않는다. 또한, 나노입자의 분산을 제대로 시키면 그 사이즈가 빛의 가시광선 영역의 파장(400~800nm)에 비해 절반 수준이하 크기의 입자가 대부분을 차지하기 때문에 염색성, 태의 변화가 적어 앞으로 더욱더 나노테크놀로지에 의한 가공이 확대될 것이 예상된다. 특히 유 무기 하이브리드 재료는 용액상태에서 제조되기 때문에 용액 코팅공정의 적용이 가능하여 다양한 코팅에 적극적으로 활용되고 있다. 또한 코팅공정 온도가 상대적으로 낮아서, 유기물의 기능성 발현이 용이하며, 섬유가공에 그대로 적용이 가능하고, 섬유고분자와 내구성 있게 직접 결합이 되어 실용성이 높다 할 수 있다. 또한 나노졸의 형성 시, 혹은 나노졸에 기능성 물질을 첨가함으로서 나노졸과 기능성 물질을 복합화하여 섬유상에 부여하는 것도 가능하다. 최근에 실리카졸의 형성과 성장에 관한 연구는 졸-겔 기술의 발전과 해석 및 상용화에 집중되어 있다. 규산나트륨과 황산 또는 염산을 사용하여 실리카를 생성하는 공정은 tetraethoxysilane (($Si(OC_2H_5)_4$, (TEOS))를 이용하여 합성하는 방법과 달리 대량의 실리카를 경제적으로 생산하는데 방법으로 널리 연구되고 있지만, 많은 연구가 수행되었음에도 불구하고 실리카 졸의 특성, 성장, 제조에 대한 충분한 이해가 이루어 지지 않고 있어, 아직까지 나노크기의 입자를 제조하는 공정에 대해서는 경제성, 효율성, 품질의 균일성이 떨어지는 것이 현실이다. 따라서 본 연구에서는 앞서 연구된 졸-겔 합성기술과 저렴한 원료인 규산나트륨을 이용하여 보다 간단하고 경제적인 방법으로 고부가가치의 다양한 실리카 나노졸을 제조할 수 있는 연구를 하고자 하였다. 이를 위해 규산나트륨 수용액의 특성, 핵 생성에 필요한 규산나트륨 수용액의 산화반응 특성, 그리고 출발용액의 졸겔 반응을 기초로 하여 실리카 졸 형성에 대한 반응물질의 혼합방법, 반응온도, 반응물의 농도, pH등이 최종 실리카 나노졸 제품의 입자 크기와 모양 등에 미치는 영향을 조사하려고 하며 이를 토대로 다양한 크기와 특성을 가진 실리카 나노졸을 제조하였다.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.2
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• pp.113-119
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• 2011

The study purpose was to examine an effect of zero emission of excess sludge on biological reactor and treated water quality within the biological reactor in the process of biological treatment combined with excess sludge reduction system with ozone. Under an ozone injection rate 0.03 g $O_3/g$ SS, Sludge Disintegration Number (SDN) 3 and less than pH 4 as pre-treatment process, it was possible to maintain a stable biological treatment process without sludge disintegration. In the test of $OUR_{max}$, of sludge, its value was hardly under the condition of ozone injection rate 0.03 g $O_3/g$ SS. There were almost no changes of MLVSS/MLSS within biological reactor followed by a solubilization of excess sludge. Accumulation of microorganism within biological reactor was also not observed. After solubilization of excess sludge, an increase for organic matter and SS concentrations of an effluent was not observed and T-N concentration was reduced by increasing nitrification and denitrification rate within biological reactor. Most of T-P was not removed by zero emission of excess sludge and was leaked by being included in effluents.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.443-454
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• 2013

Various metal ions (transition and base metals) incorporated MCM-41 catalysts can be synthesized using colloidal and soluble silica with non-sodium involved process. Transition metal ion-typically $V^{5+}$, $Co^{2+}$, and $Ni^{2+}$-incorporated MCM-41 catalysts were synthesized by isomorphous substitution of Si ions in the framework. Each incorporated metal ion created a single species in the silica framework, single-site solid catalyst, showing a substantial stability in reduction and catalytic activity. Radius of pore curvature effect was investigated with Co-MCM-41 by temperature programmed reduction (TPR). The size of metallic Co clusters, sub-nanometer, could be controlled by a proper reduction treatment of Co-MCM-41 having different pore size and the initial pH adjustment of the Co-MCM-41 synthesis solution. These small metallic clusters showed a high stability under a harsh reaction condition without serious migration, resulting from a direct anchoring of small metallic clusters to the partially or unreduced metal ions on the surface. After a complete reduction, partial occlusion of the metallic cluster surface by amorphous silica stabilized the particles against aggregations. As a probe reaction of particle size sensitivity, carbon single wall nanotubes (SWNT) were synthesized using Co-MCM-41. A metallic cluster stability test was performed by CO methanation using Co- and Ni-MCM-41. Methanol and methane partial oxidations were carried out with V-MCM-41, and the radius of pore curvature effect on the catalytic activity was investigated.

• Nuclear Engineering and Technology
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• v.13 no.3
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• pp.145-152
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• 1981

Even though a lately reported method of high temperature exchange labelling of o-iodo-hippuric acid (Hippuran) in the absence of oxidizing agent was considered to be an attractive one, the exchange mechanism was somewhat unclear. In this study iodine isotope exchanges between o-iodohippuric acid (OIH) and radioiodide ($^{125}$ $I^{ }$) or between OIH and molecular radioiodine ($^{125}$ $I_2$) were carried out at two different temperatures. Rate constants and activation parameters were measured by applying a radio-paper chromatography technique. Since o-iodobenzoic acid is known as a by-product in the exchange labelling of OIH, data were also obtained for the OIB-iodide systems for comparison. The rate constant was increased in the order of OIB...$^{125}$ $I^{[-10]}$ >OIB...$^{125}$ $I_2$>OIH..$^{125}$ $I^{[-10]}$ >OIH...$^{125}$ $I_2$ and the activation parameters for OIH were generally larger than those for OIB :$\Delta$H$\neq$$_{OIH}$>$\Delta$H$\neq$$_{OIB}$, $\Delta$S$\neq$$_{OIH}$>$\Delta$S$\neq$$_{OIB}$. These results suggest that the mechanism of the high temperature exchange is predominantly nucleophilic even though some electrophilic character can also be involved depending upon reaction conditions. Such a fact may well be caused by a feasible formation of hydrogen bonding type transition state due probably to the ortho substituent effect of-CONHC $H_2$COOH. Thus, the high temperature exchange method is estimated to be quite effective for labelling Hippuran especially at a small research center where reducing agent-free $^{131}$ I is unavailable.ailable..