• Progress in Superconductivity
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• 제9권2호
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• pp.177-182
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• 2008

[ $MgB_2$ ] thin films were fabricated using hybrid physical-chemical vapor deposition (HPCVD) method on silicon substrates with buffers of alumina grown by using atomic layer deposition method. The growth war in a range of temperatures $500\;{\sim}\;600^{\circ}C$ and under the reactor pressures of $25\;{\sim}\;50\;Torr$. There are some interfacial reactions in the as-grown films with impurities of mostly $Mg_2Si$, $MgAl_2O_4$, and other phases. The $T_c$'s of $MgB_2$ films were observed to be as high as 39 K, but the transition widths were increased with growth temperatures. The magnetization was measured as a function of temperature down to the temperature of 5 K, but the complete Meissner effect was not observed, which shows that the granular nature of weak links is prevailing. The formation of mostly $Mg_2Si$ impurity in HPCVD process is discussed, considering the diffusion and reaction of Mg vapor with silicon substrates.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.232-233
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• 2006

In recent years the interest in organic/inorganic hybrid materials has increased at a fast rate. Nano organic-inorganic hybrid composites have shown advantages for preparing hard coating layers. Especially, nano hybrid composite has low environmental pollution. It has high transparency, hardness, toughness, thermal dissociation temperature, hydrophobicity by using nano sized inorganic material. There are many ways in which these materials may be synthesized, a typical one being the use of silica and silanes using the sol-gel process. The structure of sol-gel silica evolves as a result of these successive hydrolysis and condensation reactions and the subsequent drying and curing. The sol-gel reactions are catalyzed by acids and produce silica sol solutions. The silica sol grows until they reach a size where a gel transition occurs and a solid-like gel is formed. Colloidal silica(CS)/silane sol solutions were synthesized in variation with parameters such as different acidity and reaction time. In order to understand their physical and chemical properties, sol-gel coating films were fabricated on glass. From all sol-gel solutions, seasoning effect of sol-gel coating layer on glass was observed.

• Journal of Microbiology
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• 제39권3호
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• pp.149-153
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• 2001

The electron transfer reaction is one of the most essential processes of life. Not only does it provide the means of transforming solar and chemical energy into a utilizable form for all living organisms, it also extends into a range of metabolic processes that support the life of a cell. Thus, it is of great interest to understand the physical basis of the rates and reduction potentials of these reactions. To identify the major determinants of reduction potentials in redox proteins, we have chosen the simplest electron transfer protein, rubredoxin, a small (52-54 residue) iron-sulfur protein family, widely distributed in bacteria and archaea. Rubredoxins can be grouped into two classes based on the correlation of their reduction potentials with the identity of residue 44; those with Ala44 (ex: Pyrococcus furiosus) have reduction potentials that are ∼50 mV higher than those with Va144 (ex: Clostridium pasteurianum). Based on the crystal structures of rubredoxins from C. pasteurianum and P. furiosus, we propose the identity of residue 44 alone determines the reduction potential by the orientation of the electric dipole moment of the peptide bond between 43 and 44. Based on 1.5 $\AA$ resolution crystal structures and molecular dynamics simulations of oxidized and reduced rubredoxins from C. pasteurianum, the structural rearrangements upon reduction suggest specific mechanisms by which electron transfer reactions of rubredoxin should be facilitated.

• 대한기계학회논문집B
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• 제35권9호
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• pp.897-902
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• 2011

PEMFC 의 내부에서 발생하는 화학반응은 계면의 물리적 조건 및 물성에 지배되고 그 거동은 임피던스로 표현된다. 일반적으로 임피던스 특성은 전기적 등가회로로 표현이 가능하기 때문에 PEMFC의 임피던스 계측 결과를 등가회로를 이용하여 해석함으로써 간단히 성능 진단을 할 수 있을 것이다. 본 연구에서는 이러한 등가회로를 이용하여 고분자 전해질 연료전지의 특성평가에 관한 기초연구를 수행하였다. 교류 임피던스 계측 값과 다양한 등가회로(단순 등가회로, CPE 를 고려한 등가회로, 2 개의 시정수를 고려한 등가회로, 2 개의 CPE 를 고려한 등가회로)를 이용하여 특성평가를 수행하였다. 그 결과 등가회로를 이용한 PEMFC 의 특성평가가 가능하고, 2 개의 CPE 를 고려한 등가회로가 가장 정도가 높음을 확인하였다.

• Advances in materials Research
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• 제4권2호
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• pp.113-132
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• 2015

The phenomena of high-voltage polarization and conductivity in oriented vinylidenefluoride and tetrafluoroethylene copolymer films have been investigated. It was shown that under certain electric fields, injection of carriers from the material of electrodes appears The barrier for holes injection in the copolymer was found to be lower than that for electrons. It results in more effective screening of the external field near the anode than near cathode. Electrones, ejected from cathode, creating negative charge by trapping on the surface. It is shown that the electrons injected from cathodes create a negative homocharge on the copolymer surface and then become captured on the surface shallow traps. Their nature has been studied by the x-ray photoelectron spectroscopy. It was shown that these traps may consist of chemical defects in the form of new functional groups formed by reactions of surface macromolecules with sputtered atoms of aluminum. The asymmetric shape of hysteresis curves was explained by the difference in mobility of injected holes and electrons. These factors caused appearance of "non-closed" hysteresis curves for fluorine-containing polymer ferroelectrics. Hysteresis phenomena observed at low electric fields (below coercive ones) are to associate with the behavior of the domains localized in the ordered regions formed during secondary crystallization of copolymers.

• 청정기술
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• 제12권2호
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• pp.95-100
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• 2006

엑서지 개념을 이용하여 BTX 공정의 일부인 분별증류 및 수소첨가알킬제거 공정에 대한 열역학적 해석을 실시하였다. 공정에 화학반응이 관계되는 까닭에 엑서지 값은 물리적 엑서지와 화학적 엑서지의 합으로서 구했으며 모든 계산은 공정의 조업자료를 바탕으로 한 전산 모사의 결과를 기반으로 하였다. 엑서지 손실을 구동 엑서지와 물질 엑서지 손실로 구분하여 정의하고 각각의 값을 구하였으며 그 결과를 바탕으로 공정의 에너지 이용 개선방안을 제시하였다. 엑서지 해석을 통해 공정의 내부에서 손실되는 엑서지 정확한 양과 그 위치를 파악할 수 있었으며 엑서지 해석이 산업생태학 개념의 이용과 손실방지책 연구를 위한 기초가 될 수 있음을 확인할 수 있었다.

• 대한화학회지
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• 제33권2호
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• pp.238-246
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• 1989

옥사티올란 고리에 대해서 술폭시드기와 2-메틸기가 동일 평면상에 놓인 1,3-옥사티올란술폭시드 4는 sigmatropic 전위를 통하여 고리확대 생성물로 전환한다. 이 생성물의 구조는 디히드로-1,4-옥사티인 6 또는 이것의 구조 이성체인 exo형 화합물 7의 가능성이 있다. 본 연구에서는 물리적 및 화학적 방법에 의하여 두 alternative 구조 중 올바른 구조를 밝혔다. 즉 수소핵자기 공명스펙트럼, 자외선 흡수스펙트럼, 그리고 질량분석 스펙트럼으로부터 실제로 얻어진 화합물은 디히드로옥시티인 6이었다. 또한 중수소 치환반응으로부터 환팽창 반응에서 처음 exo형 화합물 7이 생성되나 tautomerization에 의해서 결국 디히드로-1,4-옥사티인 6으로 전환함을 알았다.

• 한국환경과학회지
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• 제19권9호
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• pp.1119-1127
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• 2010

The behavior of copper throughout the whole process of wastewater treatment plant that uses the activated sludge process to treat the wastewater of petrochemical industry that contains low concentration of copper was investigated. Total inflow rate of wastewater that flows into the aeration tank was $697\;m^3$/day with 0.369 mg/L of copper concentration, that is, total copper influx was 257.2 g/day. The ranges of copper concentrations of the influent to the aeration tank and effluent from the one were 0.315 ~ 0.398 mg/L and 0.159 ~ 0.192 mg/L, respectively. The average removal rate of copper in the aeration tank was 50.8 %. The bioconcentration factor (BCF) of copper by microbes in the aeration tank was 3,320. The accumulated removal rate of copper throughout the activated sludge process was 71.3%, showing a high removal ratio by physical and chemical reactions in addition to biosorption by microbes. The concentration of copper in the solid dehydrated by filter press ranged from 74.8 mg/kg to 77.2 mg/kg and the concentration of copper by elution test of waste was 2.690 ~ 2.920 mg/L. It was judged that the copper concentration in dehydrated solid by bioconcentration could be managed with the control of that in the influent.

• Elastomers and Composites
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• 제36권4호
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• pp.268-277
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• 2001

PPG, PEG, trimethylolpropane(TMP) 등의 폴리올에 MDI(4,4'-diphenyl methane diisocyanate)를 각각 혼합하고 경화시켜 여러가지 물성을 측정하였다. 경화시간은 PEG와 TMP의 함량이 늘어날수록 짧게 나타났고 분자량의 효과보다는 관능기의 수에 더 큰 영향을 받았다. NCO-OH 반응은 NCO-NCO반응보다 활성적이고 빠르게 일어났다. 경도는 가교밀도와 분자구조의 영향을 받았으며 NCO-NCO 반응으로 생긴 도막은 취약하였고 NCO-OH간의 반응으로 생긴 도막은 유연하였다. 부착력은 결정화도와 수축율이 클수록 낮은 값을 나타내었으며 TMP 함량이 증량될수록 높은 값을 나타내었다. 난연성은 난연제의 종류와 함량에 영향을 받았으며 난연효과는 IXOL B-251이 가장 우수하였고 TCCP는 수지와의 상용성이 좋지 않아 부분적으로 분리되었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권2_spc호
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• pp.86-100
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• 2020

Analyzing and monitoring environmental contaminants based on geophysical exploration techniques have become important and it is now widely applied to delineate spatial distribution geophysical characteristics in wide area. Among the techniques, induced polarization (IP) method, which measures polarization effects on electrical potential distribution, has drawn much attention as an effective tool for environmental monitoring since IP is sensitive to changes in biochemical reactions. However, various reactions stemming from the presence of multiple contaminants have greatly enhanced heterogeneity of polluted sites to result in highly variable electrical characteristics of the site. Those contaminants influence chemical and physical state of soil and groundwater to alter electrical double layer, which in turn influences polarization of the media. Since biochemical reactions between microbes and contaminants result in various IP effects, IP laboratory experiments were conducted to investigate IP responses of the contaminated soil samples under various conditions. Field IP surveys can delineate the spatial distribution of contamination, while providing additional information about electrical properties of a target medium, together with DC resistivity. Reviewing IP effects of contaminants as well as IP surveys can serve as a good starting point for the application of IP survey in site assessment for environmental remediation.