• Transactions on Electrical and Electronic Materials
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• 제12권3호
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• pp.110-114
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• 2011

Polymeric films of high chemical stability and mechanical strength covered with a thin metallic film have been extensively used in various fields as electric and electronic materials. In this study, we have chosen polypropylene (PP) as the polymer due to its outstanding chemical resistance and good creep resistance. We coated thin nickel film on PP films by the electroless plating process. The surfaces of PP films were pre-treated and modified to increase the adhesion strength of metal layer on PP films, prior to the plating process, by an environment-friendly process with atmospheric plasma generated using dielectric barrier discharges in air. The surface morphologies of the PP films were observed before and after the surface modification process using a scanning electron microscope (SEM). The static contact angles were measured with deionized water droplets. The cross-sectional images of the PP films coated with thin metal film were taken with SEM to see the combined state between metallic and PP films. The adhesion strength of the metallic thin films on the PP films was confirmed by the thermal shock test and the cross-cutting and peel test. In conclusion, we made a composite material of metallic and polymeric films of high adhesion strength.

• 한국미생물·생명공학회지
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• 제22권6호
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• pp.636-642
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• 1994

Essential amino acids involving in the catalytic mechanism of the $\beta$-D-xylosidase of Bacillus stearothermophilus were determined by chemical modification studies. Among various che- mical modifiers tested N-bromosuccinimide (NBS), $\rho$-hydroxymercurybenzoate (PHMB), N-ethylma- leimide, 1-[3-(di-ethylamino)-propyl]$-3-ethylcarbodi-imide (EDC), and Woodward's Reagent K(WRK)inactivated the enzyme, resulting in the residual activity of less than 20%. WRK reduced the enzyme activity by modifying carboxylic amino acids, and the inactivation reacion proceeded in the form of pseudo-first-order kinetics. The double-lagarithmic plot of the observed pseudo-first- order rate constant against the modifier concentration yielded a reaction order of 2, indicating that two carboxylic amino acids were essential for the enzyme activity. The $\beta$-D-xylosidase was also inactivated by N-ethylmaleimide which specifically modified a cysteine residue with a reaction order of 1, implying that one cysteine residue was important for the enzyme activity. Xylobiose protected the enzyme against inactivation by WRK and N-ethylmaleimide, revealing that carboxylic amino acids and a cysteine residue were present at the substrate-binding site of the enzyme molecule.

• Journal of Microbiology and Biotechnology
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• 제11권1호
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• pp.118-123
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• 2001

The alginate lyase A1-III gene of Sphingomonas species A1 is composed of 1,077 nucleotides, encoding a protein (359 amino acids) with a molecular mass of 40,322 Da. Recombinant A1-III expressed in Escherichia coli exhibited the same full enzymatic activity as native A1-III. In order to identify the critical residue for activity, a site-directed mutation was introduced into the A1-III gene (H192A, His192->Ala). Recombinant A1-III (H192A) exhibited a significant decrease in enzyme activity (one-thirty thousandth of that of A1-III), without any conformational change, as detected by the CD spectra in the far UV region. Also, the chemical modification of wild-type A1-III with methyl 4-nitro benzene sulfonate resulted in a 40% decrease from the initial activity, whereas the same modification of A1-III (H192A) produced no change in the activity. The role of His192 on the catalytic process was also explored based on a model of A1-III docked with mannuronic acid into the active site.

• 마이크로전자및패키징학회지
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• 제27권2호
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• pp.27-32
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• 2020

Robust and hydrophobic tetraethoxysilane (TEOS) based silica aerogel was synthesized by supercritical alcohol drying with surface modification using the phenyl based silica co-precursor (PTMS). The aerogels were synthesized by hydrolysis and polycondensation reaction in which TEOS and PTMS in methanol were reacted together in presence of oxalic acid and ammonium hydroxide as the catalysts. Supercritical alcohol dried PTMS/TEOS composite silica aerogel were examined for the hydrophobicity, chemical interaction, surface morphology, and textural characteristics. The hydrophobic silica-based aerogels were characterized by Fourier transform infrared spectroscopy to investigate the presence of functional groups and chemical bonds. The prepared silica demonstrates hydrophobicity (76°-149°), a high specific surface area (398 ㎡/g to 739 ㎡/g). The present investigation provides a simple approach to synthesize hydrophobic and thermally stable silica aerogels.

• Carbon letters
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• 제4권1호
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• pp.14-20
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• 2003

Based on the previous results of the equilibrium and batch adsorptions, the removal efficiency of the two-step surface-modified activated carbon ($2^{nd}AC$) for heavy metal ions such as Pb, Cd, and Cr in fixed column was evaluated by comparing with that of the as-received activated carbon (AC) and the first surface-modified activated carbon ($1^{st}AC$). The order of metal removal efficiency was found as $2^{nd}AC$ > $1^{st}AC$ $\gg$ AC, and the efficiency of the $2^{nd}AC$ maintained over 98% from the each metal solution. Increase of the removal efficiency by the second surface modification was contributed to maintain favorable pH condition of bulk solution during adsorption process. The removal of the heavy metals on the $2^{nd}AC$ was selective with Pb being removed in preference to Cr and Cd in multicomponent solutions and slightly influenced by phenol as the organic material.

• 공학교육연구
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• 제13권5호
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• pp.55-60
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• 2010

Chemistry laboratory class was produced for senior high school freshmen with the cooperation of university staffs, high school teachers and the university students. Although the students who will take the lab class are senior high school freshmen, we decided to prepare four experiments that are simple and have highly visible reactions or transformation. That is, 1) Water purification, 2) Surface modification, 3) Briggs-Rauscher reaction, and 4) Polymer synthesis and characterization. After the safety guideline and experiment instructions by the faculty staffs, two teaching assistants (TAs) supervised each experiment. Since taking a direct part in it will provide stronger impact than only being one who is just watching the experiment, all experiments contained some process that the high school students must handle the reagents, tools or the equipment, by themselves. Although, the operation performed by the students was limited to a series of simple actions, the various unique phenomena presented by the experiments impressed the students. The lab class was fruitful not only for high school students, but also good for university students. The lab class provided good opportunity for them to improve the abilities to teach and guide someone.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.156-163
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• 2008

화학공장에서는 공정 이상, 장치 수명 및 경제적 환경 등에 의하여 변경이 발생하고 있다. 그리고 변경관리는 정확한 기술적 판단근거에 의한 변경 판정, 위험도 확인 및 위험성 평가 수행 등 근본적인 공정안전 기술을 바탕으로 이루어진다. 그러나 변경관리는 경험 부족, 지식 부족 및 기술인력 부족 등의 이유로 수행하기 매우 어려운 상황에 놓여있다. 본 연구에서는 화학공장 변경관리의 취약점을 파악하고 이를 적절히 보완하여 안전성을 향상할 수 있는 변경관리 체계를 구축하였다. 위험성 평가를 기반으로 하는 변경관리 절차의 정립 및 변경 여부 판단, 변경시 위험도 산정 등 변경관리 의사결정 단계들의 명확한 판단 기준 체계 정립을 통한 장치산업의 변경관리 수행 체계를 제안하였다. 이러한 안전공학 기술이 접목된 형태의 변경관리 절차를 제안하여 화학공장의 안전성 향상을 꾀하고자 하였다.

• Macromolecular Research
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• 제10권5호
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• pp.291-295
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• 2002

Atomic force microscopy(AFM) was used to study the polyethylene(PE) surfaces grafted and immobilized with acrylic acid by Ar plasma treatment. The topographical images and parameters including RMS roughness and Rp-v value provided an appropriate means to characterize the surfaces. The plasma grafting and immobilization method were a useful tool for the preparation of surfaces with carboxyl group. However, the plasma immobilization method turned out to have a limitation to use as a means of preparation of PE surface with specific functionalities, due to ablation effect during the Ar plasma treatment process.

• 분석과학
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• 제8권4호
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• pp.849-854
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• 1995

A series of biologically active phosphopeptides were synthesized and their behavior in tandem mass spectrometry have been investigated. The structure identifications of other unusual peptides such as sulphated, glycosylated, lipoidal, and backbone modified peptides have been carried out. For all tested peptides, the structural modification could be determined directly by measurement of the absolute molecular weight in combination with collision-induced-dissociation in tandem mass spectrometry.

• 한국방재학회 논문집
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• 제5권2호
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• pp.45-56
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• 2005

구름씨뿌리기 방법에 의한 안개조절의 가능성을 파악하기 위해 대관령 산악지역의 구름특성을 분석하였다. 구름씨뿌리기에 의한 안개조절은 흡습성 물질을 이용한 온안개 소산에 집중되고 있다. 이 연구에서는 관측된 안개의 특성을 통계적으로 분석하고 이에 대해 논의하였다. 안개의 대부분은 여름철에 발생한 온안개이고 6시전 이른 아침에 발생하여 7시${\sim}$9시 소산되는 특성을 보인다. 봄철과 겨울철에는 AgI시딩에 적합한 동풍계열의 냉안개가 발생한다. 이 결과로부터 안개소산에 적합한 구름씨뿌리기방법과 물질을 추론할 수 있으며 이는 실제 냉안개와 온안개 실험에 적용할 수 있다.