• Journal of the Society of Cosmetic Scientists of Korea
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• v.18 no.1
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• pp.64-80
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• 1992

Considerable interest has been generated in age-related non-enzymatic glycosylation and crosslinking of collagen in view of its extracellular nature, and its long biological half-life. The effects of UVA, which penetrates deep in dermis, and reactive oxygen species (ROS) on age- related changes of dermal collagen were studied. The amount of nonenzymatic glycosylation, fragmentation, and crosslinking of collagen were monitored from the mixtures of Type I collagen from calf skin and glucose, irradiated by UVA, with or without scavengers of ROS. At both high and low glucose dosages, non-enzymatic glycosylation was not affected by UVA irradiation. At high glucose dosage, however, glycosylation was reduced by the scavengers of superoxide radical and singlet oxygen, bolt not by hydroxyl radical scavengers. Fragmentation was increased by UVA and decreased by all ROS scavengers. Crosslinking was also enhanced by UVA, and effectively blocked crosslinking. Superoxide radical and singlet oxygen, which were produced by autoxidation of glucose independently to UVA, may encounter the initial phase of glycation. ROS generated from Amadory compounds by UVA enhanced fragmentation and crosslinking Hydroxyl radical was thought to be a major ROS affecting crosslinking. These results suggest that UVA and ROS are able to enhance age-related structural changes of collagen, as affecting many other tissue and cellular components.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.247-254
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• 2010

Due to lightweight and high durability of glass-fiber reinforced polyester (GFRP) materials, they are promising alternatives to conventional construction materials such as steel, concrete and wood. As good application examples of GFRP materials, several types of temporary arch bridges were suggested and verified by finite element analyses in our previous study where snap-fit GFRP decks were applied. In this paper, we conduct a structural performance test to verify safety and serviceability of the temporary arch bridge, where snap-fit GFRP decks are assembled by bolts. The structural problems occurred in this test are also discussed and improvement of temporary arch bridges is suggested to resolve the occurred structural problems.

• Prospectives of Industrial Chemistry
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• v.23 no.6
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• pp.25-36
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• 2020

용액공정을 통해 유기 전자소자를 대면적으로 제조하는 것은 다양한 장치 구성 요소(반도체, 절연체, 도체)의 패터닝 및 적층이 필요하기 때문에 매우 어려운 과제이다. 본 연구에서는 4개의 광 가교 기능기를 가지는 3차원 사면체 가교제인 (2,2-bis(((4-azido-2,3,5,6-tetrafluorobenzoyl)oxy)methyl)propane-1,3-diyl bis(4-azido-2,3,5,6-tetrafluorobenzoate) (4Bx)를 활용하여 용액공정을 기반으로 형성된 전자재료 박막을 고해상도로 패터닝 및 적층하는 기술을 개발하고, 이를 사용하여 고분자 박막 트랜지스터(PTFTs) 및 논리회로 어레이 제작을 진행하였다. 4Bx는 다양한 용액공정이 가능한 전자재료와 용매에 쉽게 혼합될 수 있으며, 자외선(UV)에 의해 가교제가 광 활성화되어 전자재료와 가교 결합을 형성할 수 있다. 4Bx는 기존의 2개의 광 가교 기능기를 갖는 가교제에 비해 높은 가교 효율로 인해 적은 양을 첨가하여도 완전하게 가교된 전자재료 박막을 형성할 수 있어 전자재료의 고유한 특성을 보존할 수 있다. 더욱이, 가교된 전자재료 박막은 화학적 내구성이 향상되어 고해상도 미세 패터닝을 할 수 있을 뿐만 아니라 용액공정을 통해 전자소자를 구성하는 전자재료의 적층이 가능하다. 4Bx의 광 가교 방법은 전용액공정을 통한 전자소자의 제작에 대한 혁신적인 방안을 제시한다.

• Elastomers and Composites
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• v.33 no.4
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• pp.274-280
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• 1998

Order of reaction, rate constant, activation energy for vulcanization reaction, crosslinking density, and elastic constant of the network produced by sulfur curing were investigated on the SBR/BR blends containing silica and carbon black under same cure system. The reaction order was shown to be first order regardless of filler types. The carbon black filled rubber compounds showed higher rate constant compared to silica filled compounds. But activation energy appeared to be same regardless of filler type and rubber blend ratio. The crosslinking density and elastic constant is higher in the carbon black filled compound compared to silica filled compounds because of strong interaction between rubber and carbon black. On the other hand, crosslinking density and elastic constant were decreased with increasing the butadine rubber content in rubber blends. From the comparison of combined sulfur content in the vulcanized rubber, sulfur content in the silica filled compound become constant 20min later after reaction initiates but sulfur content in the carbon black filled compound become constant 10min later after reaction starts. The silica compound has a longer induction time ($t_2$) and optimum cure time($t_{90}$) compared to those of the carbon black filled compound.

• Elastomers and Composites
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• v.40 no.4
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• pp.284-289
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• 2005

Changes of crosslink densities of resole-cured NR composites by thermal aging were studied. The thermal aging was performed at $50-90^{\circ}C$. The crosslink density change increased with increase of the aging temperature and then decreased. Level of the crosslink density change decreased with increase of the resole content. Increase of the crosslink density by the thermal aging was explained with the formations of new crosslinks by combination reactions of pendent groups terminated by resoles and crosslinking reactions by pendent groups having methylol or o-methylene quinone intermediate. And decrease of the crosslink density by the thermal aging was explained with the dissociations of the existing crosslinks having dimethylene ether linkages.

• Elastomers and Composites
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• v.40 no.1
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• pp.29-36
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• 2005

Mixing condition and procedure affect properties or a filled rubber compound such as filler dispersion, viscosity, and bound rubber formation. Influence of separate load of styrene-butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) on properties or silica-filled SBR compounds containing NBR was studied. Cure time and cure rate became faster as NBR content increased. The crosslink density increased with increase in the NBR content. The bound rubber content also increased as the NBR content increased. NBR content of the bound rubber was higher than that of the compounded rubber. The bound rubber content was higher when SBR and NBR were loaded separately than when loading simultaneously. The cure time and cure rate were slower for the separate load than for the simultaneous one. The crosslink density was also lower for the former case than for the latter one.

• 한국약용작물학회:학술대회논문집
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• 2008.11a
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• pp.485-486
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• 2008

• Korean Journal of Food Science and Technology
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• v.30 no.2
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• pp.372-378
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• 1998

Two types of formaldehyde-treated soy protein isolate (SPI) films, formaldehyde-incorporated and formaldehyde-adsorbed films, and control SPI films were prepared. Cross-linking effect of formaldehyde on selected film properties such as color, tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and water solubility (WS) were determined. Physical properties of formaldehyde-incorporated films were not geneally different from those of control films, while almost all of those among formaldehyde-adsorbed films were significantly different. Through cross-linking development within formaldehyde-adsorbed films, WS decreased significantly (P<0.05) from 26.1% to 16.6%, and TS increased two times while E decreased two times compared with control films. This was caused by insolubilization and hardening of protein by cross-linking most likely attributed to the significant changes in properties of protein films reacted with formaldehyde.

• Prospectives of Industrial Chemistry
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• v.23 no.6
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• pp.14-24
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• 2020

최근 우수한 발광 특성을 갖는 양자점을 고해상도 디스플레이의 발광 소재로 도입하고자 하는 노력이 활발하다. 양자점을 활용한 디스플레이의 실현을 위해서는 콜로이드 상태인 다색의 양자점을 고해상도로 패터닝하는 기술의 확립이 필요하다. 본 연구에서는 ethane-1,2-diyl bis(4-azido-2,3,5,6-tetrafluorobenzoate)를 양자점용 가교제로 활용하여 용액공정을 기반으로 형성된 양자점 박막을 고해상도로 패터닝한 기술을 소개하고자 한다. 위 양자점용 가교제의 양 말단에는 아지드 그룹을 포함한 작용기가 존재한다. 아지드 기는 자외선에 의해 광 활성화되어 양자점 표면의 알킬 리간드와 가교 결합을 형성함으로써, 양자점 박막에 화학적 내구성을 부여한다. 본 기술을 기반으로, 적색, 녹색, 청색의 카드뮴 기반 양자점을 고해상도로 패터닝하고 정밀하게 배열하여 인치 당 화소 수 1400 이상의 픽셀 형성에 성공하였다. 또한 가교 반응 후에도 성능 저하가 없는 양자점 박막 및 자발광 양자점 다이오드를 개발하였다.

• Composites Research
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• v.22 no.3
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• pp.35-43
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• 2009

In this study, for a radiator hose made of carbon black filled EPDM(ethylene-propylene diene monomer) rubber, a measuring method of crosslink density was established to analyze the aging behaviors under thermo-oxidative stresses. At $125^{\circ}C$, the crosslink density of the rubber specimens decreased slightly in the initial stage, but increased with increasing the aging time. Such variation in crosslink density was similar to that of tensile strength. This might be due to the formation of sulphoxide crosslinks as well as to additional crosslinks made by the reaction of unvalcunized sulfurs. A high temperature aging of rubber specimens at $180^{\circ}C$ caused a slight increase in crosslink density while it did a large decrease in tensile strength and elongation. With aging at high temperature, the formation of carbonyl groups in EPDM molecule chain and formation of sulphoxide crosslink, rather than the crosslink density variation itself, had a large influence on such changes in mechanical property.