• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.2949-2954
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• 2012

Nano ZnO with an average size of 8 nm was prepared by thermal decomposition of zinc oxalate at $450^{\circ}C$. A series of based composite polymer electrolyte PEO-$LiClO_4$ and nano ZnO as a filler have been synthesized using solution cast technique, with varying the filler ratio systematically. XRD, DSC and FTIR studies have been conducted to investigate the structure and interaction of different groups in the composite polymer electrolyte. Effect of nano ZnO ceramic filler concentration on the structure of composites and their electrical properties (DC-conductivity, AC-conductivity, dielectric constant, dielectric loss and impedance) at different frequencies and temperatures was studied. Melting temperature ($T_m$) of PEO decreased with the addition of both $LiClO_4$ salt and nano ZnO filler due to increasing the amorphous state of polymer. All composite samples showed an ionic conductivity. The maximum room temperature ionic conductivity is found for $(ZnO)_{0.5}(PEO)_{12}(LiClO_4)$ composite sample. All the results are correlated and discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1631-1633
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• 2000

A study was carried out on the effect of VDF mol%, on the phase transition presented by P(VDF/TrFE) copolymer cast from dimethylformamide(DMF) solution with molar ratios 70/30 and 80/20. The results from dielectric spectrum and differential scanning calorimetry(DSC) showed that the phase transitions from ferroelectric to paraelectric phase(Curie transition) were observed The Curie point slightly has shifted to high temperature with increasing in VDF mol%, however, the melting point has shifted to low temperature.

• E2M - 전기 전자와 첨단 소재
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• 제8권6호
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• pp.699-707
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• 1995

The material that is both conductive in electricity and transparent to the visible ray is called transparent conducting thin film. It has many fields of application such as Solar Cell, Liquid Crystal display, Vidicon on T.V, transparent electrical heater, selective optical filter, and a optical electric device , etc. In the recent papers on several TCO( transparent conducting oxide ) material, the study is mainly focusing on ITO(indium tin oxide) because ITO shows good results on both optical and electrical properties. Nowaday, in the development of LCD(Liquid Crystal display), the low temperature process to reduce the production cost and to deposit ITO on polymer substrate (or low melting substrate) has been demanded. In this study, we prepared indium tin oxide(ITO) by a cylindrical DC magnetron sputtering with Indium-tin (9:1) alloy target instead of indium-tin oxide target. The resistivity of the film deposited in oxygen partial pressure of 5% and substrate temperature of 140.deg. C. is 1.6*10$\^$-4/.ohm..cm with 85% optical transmission in viaible ray.

• 생명과학회지
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• 제8권5호
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• pp.526-531
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• 1998

In this study, the composition and characteristics of poly-$\beta$-hydroxybutyrate (PHB) biosynthesized by Actinobacillus sp. EL-9 are investigated. PHB produced by Actinobacillus sp. EL-9 was identified as the homopolymer of 3-hydroxy-butyric acid (PHB) by infrared spectroscopy and nuclear magnetic resonance spectroscopy analysis. The melting tem-perature (T$_{m}$), and crystallization temperature(T$_{c}$) of PHB was 169.7$^{\circ}C$ and 69.13$^{\circ}C$, respectively. The viscosity on he basis of Brookfield viscometer was 6.01 ㎗/g. The viscosity-average molecular weight estimated by Mark-Ho-wink-Sakurada equation was 1.08$\times$10$^{6}$ ($\pm$3,000).00).

• Bulletin of the Korean Chemical Society
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• 제21권1호
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• pp.110-117
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• 2000

A series of new liquid crystalline dimesogenic compounds with chiral tails was synthesized, and their thermal and liquid crystalline properties were studied. The chain length of the central polymethylene spacers (x) was varied from dimethylene (2) to decamethylene (12). These compounds were characterized by elemental analysis, IR and NMR spectroscopy, differential scanning calorimetry (DSC), and cross-polarizing microscopy. All compounds were found to be enantiotropically liquid crystalline, and the values of melting ($T_m$) and isotropization temperature ($T_i$) as well as enthalpy change (Δ$H_i$) and entropy change for isotropization (Δ$S_i$) decreased in a zig-zag fashion revealing the so-called odd-even effect as x increases. Their mesomorphic properties fall into three categories depending upon x; (a) compounds with x=2 and 4 formed two different mesophases, smectic and cholesteric phases in that order on heating, and vice versa on cooling, (b) compounds with x=3, 7, 8, 10 and 11 reversibly formed only the cholesteric phase, and (c) compounds with x=5, 6, 9 and 12 exhibited only a cholesteric phase on heating, whereas on cooling they formed two different mesophases, cholesteric and smectic phases, sequentially.

• Composites Research
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• 제26권2호
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• pp.123-128
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• 2013

PVDF(polyvinylidene fluoride) 섬유는 습식방사방법을 적용하여 제조하였다. PVDF 분자 내 압전 특성과 밀접한 관련을 갖는 ${\beta}$형태의 결정 함량을 높이기 위하여, 본 연구에서는 습식방사 된 섬유에 1단계 연신, 2단계 어닐링 공정으로 구성하여 후 처리를 도입하였다. 후 처리는 PVDF 고분자의 유리전이 온도($T_g$)와 용융온도($T_m$) 사이의 온도범위에서 진행하여, 최대의 ${\beta}$형태 결정을 생성 할 수 있는 열처리 조건을 최적화 하였다. 제조된 PVDF 섬유 내 분자 배향 특성과 결정 구조를 확인하기 위하여 적외선 분광 광도계(FT-IR)와 X선 회절 분석기(XRD)를 이용하여 분석하였으며, 전자현미경(SEM)을 통하여 섬유의 표면을 관찰하여 섬유의 평균직경을 확인하였다. 분석 결과, 후 처리 공정이 PVDF 결정 구조의 영향을 미치며, ${\beta}$형태의 결정 비율을 증가시킨다는 것을 확인하였다. 더불어 ${\beta}$형태 결정 향상으로 인해 기계적 강도가 증가되었으며, 압전 특성 향상까지 기대할 수 있었다.

• 대한기계학회논문집
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• 제16권11호
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• pp.2136-2149
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• 1992

본 연구에서는 Gebhart등이 제시한 새로운 밀도식을 사용하여 경사진 등온평 판이 저온의 순수물속에 잠겨있을 때의 자연대류현상을 F.D.M 방법을 사용하여 수치해 석하였다. 이러한 수치 계산으로부터 등온 평판 주위의 속도, 온도분포 및 평균 누 셀트수를 각각 구하고, 주위물 온도 및 평판의 경사각이 등온 평판에 의한 유동 및 열 전달 현상에 미치는 영향을 구명하였다.또한 본 연구결과와 Riu등이 상사해석하여 구한 다중 정상 상태 영역에서의 결과들과 실험적 연구의 결과들을 상회 비교분석하였 다. 여기서 사용한 등온 평판은 기존의 연구들에서 많이 이용하고 있는 가장 이상적 인 등온면인 0.deg. C 얼음면을 택하였다.

• 공업화학
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• 제19권1호
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• pp.133-136
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• 2008

온실 가스 가운데 하나인 이산화탄소를 줄이기 위한 연구의 일환으로 이산화탄소와 산화 스틸렌을 원료로 하고 zinc glutarate를 촉매로 하여 poly(styrene carbonate)를 합성하였다. 여러 가지 분광학적인(FT-IR, $^1H$-NMR, $^{13}C$-NMR, GC-MS) 분석결과 교대 공중합체임이 확인되었으며, MALDI법에 의하여 분자량($\bar{M}_n$)은 $5.0{\times}10^4$이며, 유리전이온도는 $88^{\circ}C$이고, 융융점은 $240^{\circ}C$로 밝혀졌다. 이 고분자를 열분해하면 고리형 카보네이트인 styrene carbonate가 생성되는 것도 확인하였다.

• 한국결정성장학회지
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• 제7권3호
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• pp.349-358
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• 1997

비선형 광학 유기물질 meta-Nitroaniline(mNA)의 고품질 단결정을 과냉법을 사용하여 성장시키는데 처음으로 성공 하였다. 정제한 mNA를 녹인 뒤, 0.1 K의 일정한 과냉각 상태에서 종자 결정을 도입하여 하루 동안 크기가 약 $20{\times}15{\times}15 \textrm {mm}^3인 우수한 품질의 단결정을 성장시켰다. 성장된 결정의 전체적인 외형상 특징은 한쪽 방향으로만 성장했다는 것이다. 성장한 방향으로는 잘 발달된 {111}면과 {021}면으로 형성되어 있으나, 성장하지 않을 반대쪽 방향으로는 결정면이 생기기 않았다. 결정 성장이 이루어지는 방향은 파이로 전기적 방법으로 측정한 결과, [001] 방향으로 판명되었다. 성장된 결정의 결함 구조 특성은 싱크로트론 X-선 topography를 이용하여 조사하였으며, 비선형 광학 특성은 2차 조화파 변환 효율 및 광손상 문턱 값 측정으로 조사하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제16권2호
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• pp.269-276
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• 2003

We studied the gel properties of porcine collagen with microbial transglutaminase (MTGase) as a catalyst. A creep meter was used to measure the mechanical properties of gel. The results showed samples with high concentration of MTGase gelled faster than those with a low concentration of MTGase. The gel strength increased with incubation time and the peaks of breaking strength for 0.1, 0.2 and 0.5% MTGase were obtained at 40, 20 and 10 min incubation time, respectively. According to SDS-PAGE, the MTGase was successfully created a collagen polymer with an increase in molecular weight, whereas no change in formation was shown without MTGase. The sample with 0.5% MTGase began to polymerize after 10 or 20 min incubation at $50^{\circ}C$, and complete polymerization occurred after 40-60 min incubation. Scanning electron microscopic analysis revealed that the gel of porcine collagen in the presence of MTGase produced an extremely well cross-linked network. The differential scanning calorimetric analysis showed the peak thermal transition of porcine collagen gel was at $36^{\circ}C$, and that with MTGase no peak was detected during heating from 20 to $120^{\circ}C$. The melting point of porcine collagen gel could be controlled by MTGase concentration, incubation temperature and protein concentration. Knowledge of the structural and physicochemical properties of porcine collagen gel catalyzed with MTGase could facilitate their use in food products.