• International Journal of Automotive Technology
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• 제6권6호
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• pp.657-663
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• 2005

Recently, weight reduction of vehicles has been of great interest, and consequently the use of composite materials in the automotive industry is increasing every year. Composite sandwich panels which consist of two skins and core materials are replacing steels in automotive floor and door. The substitution of one material for another is accompanied by change of joining method, so that adhesive bonding has been popularly used for joining method of composite materials. In the case of adhesive bonding of composite materials, there could be loss in the joint strength by delamination of two faceplates or cracking on faceplate. Thus, it is necessary to prevent loss in the joint strength by designing the joint geometry. In the present paper, adhesive bonding of aluminum sandwich sheet was tried. For understanding joint behavior, studies on stresses in the single lap joint were reviewed and failure modes of composite material were analyzed. Strength tests on the single lap joint consisting of aluminum sandwich sheet and steel were performed and variation of the joint strength with the joint configuration was shown. Based on these results, design guide of adhesive bonding in aluminum sandwich sheet was suggested.

• Macromolecular Research
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• 제15권1호
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• pp.59-64
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• 2007

Star-shaped, nonlinear optical (NLO) material was synthesized and its optical, thermal, and electro-optic properties were investigated. Three NLO-active dipolar chromophores containing a phenylene ring substituted with a bulky alkyl chain as a conjugation bridge were chemically bonded to the core of 1,1,1-tris(4-hydroxyphenyl)ethane to form a dendritic architecture. The chemical structure and purity of the chromophore were verified by NMR spectroscopy. The chromophore exhibited a broad absorption band centered at around 608 nm tailing up to 760 nm in toluene solution and also showed a discernible solvatochromic shift in more polar solvent. The chloroform solution of the dendrimer produced an absorption band with a red-shifted maximum as large as 28 nm when compared to that of the toluene solution. It was thermally stable up to $275^{\circ}C$ in a nitrogen atmosphere and had a glass transition temperature of $76^{\circ}C$. In a preliminary result, the polymer film containing the dendritic compound exhibited a shift of 19 pm/V taken at $1.55{\mu}$.

• 한국철도학회논문집
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• 제12권1호
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• pp.110-114
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• 2009

본 연구에서는 스카프 패취가 접착된 복합소재 샌드위치 적층판의 압축강도 회복특성을 평가하였다. 본 연구에서는 알루미늄 허니콤 심재와 CF1263 직조된 탄소/에폭시 면재를 갖는 틸팅열차차체에 적용된 샌드위치 시험편이 이용되었다. 샌드위치 시험편은 저속충격에 의해 손상을 가하고, 스카프 보수기법에 의해 보수되었다. 보수 후 CAI시험을 통해 충격 후 압축강도를 평가하여 강도회복정도를 정량적으로 규명하였다. 본 시험으로부터 단지 스카프 보수를 적용한 경우 약 72%정도의 강도를 회복하였고, 추가보수층 한층을 추가했을 경우 약 91%까지 강도를 회복시킬 수 있음을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.205-208
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• 2008

강재매입형 합성교각은 강재의 구속효과에 의하여 심부콘크리트의 내력상승을 유발하고, 또한 심부 콘크리트로 인한 강재의 좌굴 보강효과로 단면과 자중을 증가시키지 않고도 부재의 내력이 증가하게 만들 수 있어 내진 설계시 필요한 여러 조건들을 충족시키는 구조물이라 할 수 있다. 조립식 강재매입형 합성교각에서는 일체형으로 하는 경우에는 프리스트레스를 도입하지 않아도 되지만 세그먼트를 나눌 경우에는 이음부 균열제어를 위해 일정 수준의 프리스트레스를 도입해야 한다. 도입되는 프리스트레스에 의해 합성단면에 발생하는 초기 응력과 변형은 콘크리트의 장기거동에 의해서 변화하게 되고 설계시 이를 검토해야 한다. 이 논문에서는 세그먼트로 나누어진 프리캐스트 합성교각에 프리스트레스를 도입한 후 강연선에 부착된 로드셀과 철근, 콘크리트, 강관의 변형률 변화를 통해 프리스트레스 손실량을 검토하여 분석하였다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.388-394
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• 2005

A typical honeycomb sandwich panel consists of two thin, high-strength facings bonded to a thick, light-weight core. Each component by itself is relatively weak and flexible, but when it combind in a sandwich panel they produce a structure that is stiff, strong, and lightweight. In addition to use in honeycomb sandwich panels, honeycomb is used for energy absorption, radio frequency shielding, light diffusion, and to direct air flow.Accordingly, the usage of honeycomb sandwich structure is very widely applied to the aircraft, the automobile, and marine industry, etc., because of these advantages. Generally, this honeycomb sandwich structure is manufactured by autoclave process.In this study, the honeycomb sandwich structure was produced by prepreg. To prove the suitability the honeycomb sandwich structure with prepreg, The optimum design of the skin materials and honeycomb sandwich structure were evaluated with the theory of stress analysis.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.78-78
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• 2010

The Adsorption structures of phenylalanine on Ge(100) surface have been investigated as a function of coverage using high-resolution photoemission spectroscopy (HRPES) and density functional (DFT) calculation. To converge these experimental and theoretical conclusion, we systematically performed HRCLPES measurements and DFT calculation for various coverage in the adsorption structures of phenylalanine molecules on the Ge(100) surface. In this study, we found two different adsorption structure as a function of coverage in phenylalanine on Ge(100), monitoring three core level spectra (Ge 3d, C 1s, N 1s, and O 1s) using HRPES Through analysis of the binding energies, we confirmed that O-H dissociated and N dative-bonded structure emerges at low coverage (0.10 ML), which is the same to the result of glycine and alanine on Ge(100) system, whereas O-H dissociation structure also appears at higher coverage. Moreover, we observed the shape of phenyl group being included in phenylalanine is changed from flat to tilting structure at final state using DFT calculation. Through the spectral analysis for phenylalanine, we will demonstrate variation of coverage dependent structural change for phenylalanine on Ge(100) surface using experimental (HRPES) and theoretical studies (DFT calculation).

• 한국생산제조학회지
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• 제21권1호
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• pp.40-45
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• 2012

The glass edge sealing is one of the vacuum glazing core manufacturing process and it needs the high reliability for the vacuum keeping. Conventionally, the glass edge sealing had been being researched by the method that pasted the flit on the glass edge part and bonded two sheets of glass. But this way has the defect that can't make tempered glass. In order to remedy it's faults, in this paper, the glass edge was sealed by using the hydrogen mixture gas torch within the furnace. The parameter having an effect on the glass edge sealing through the basic test was set. And the correlation of the thickness of the glass edge and parameter were analyzed through the design of experiment. By using the Taguchi method, the optimal process condition for the glass edge sealing was drawn and the validity was verified.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.147-147
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• 2000

Chemisorption of oxygen molecules on the Si(111)-(7x7) surface has been studied extensively as a model for the initial-stage oxidation of the surface. The basic step to the surface oxidation is the dissociation of the adsorbed O2 molecules, but the dissociation procedure and the atomic structure of the reaction products still remains as a subject of debates. We present here density-functional theory calculations on the initial-stage oxidation states of the Si adatom site for all possible dissociation configurations that can be generated by multiple O2 reactions. We determine the equilibrium structures and analyze their electronic and vibrational properties in comparison with measured UPS, XPS, and EELS spectra. The O(ad) atom bonded on top of the Si adatom is always less stable than the O(ins) atom inserted into one of the adatom backbonds. Our electronic and vibrational analysis demonstrates further that the O(ad) and O(ins) atoms account well for the metastable and stable features in previous experiments, respectively. Moreover, the calculated decay pathways of the metastable structures and the comparison of the calculated O ls core-level shifts with XPS data provides a convincing argument in unambiguously identifying the experimental metastable and stable structures, thereby making it possible to build a correct atomic-scale picture of the initial-stage oxidation process on this surface.

• 한국재료학회지
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• 제19권1호
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• pp.44-49
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• 2009

Conjugated nanocrystals using CdSe/ZnS core/shell nanocrystal quantum dots modified by organic linkers and glucose oxidase (GOx) were prepared for use as biosensors. The trioctylphophine oxide (TOPO)-capped QDs were first modified to give them water-solubility by terminal carboxyl groups that were bonded to the amino groups of GOx through an EDC/NHS coupling reaction. As the glucose concentration increased, the photoluminescence intensity was enhanced linearly due to the electron transfer during the enzymatic reaction. The UV-visible spectra of the as-prepared QDs are identical to that of QDs-MAA. This shows that these QDs do not become agglomerated during ligand exchanges. A photoluminescence (PL) spectroscopic study showed that the PL intensity of the QDs-GOx bioconjugates was increased in the presence of glucose. These glucose sensors showed linearity up to approximately 15 mM and became gradually saturated above 15 mM because the excess glucose did not affect the enzymatic oxidation reaction past that amount. These biosensors show highly sensitive variation in terms of their photoluminescence depending on the glucose concentration.

• 대한토목학회논문집
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• 제36권1호
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• pp.39-47
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• 2016

노후 콘크리트포장의 가장 일반적인 보수 방법은 복합 구조체 포장구조인 접착식 덧씌우기 방법이 일반적으로 사용되고 있으며, 이와 같은 복합 구조체는 신 구 콘크리트 간 부착력에 따라 공용 중 차량하중, 환경하중 하에서 일체화된 역학적 거동의 확보유무에 따라 장기 공용성 확보에 커다란 영향을 받게 된다. 현재 상용화 되고 있는 접착 덧씌우기 공법들은 우수한 신구 접착력을 확보하기 위하여 다양한 장비를 이용한 경계면 처리 방식과 더불어 재료자체의 접착력을 향상시키고자 폴리머 등의 혼화재료를 사용하고 있다. 그러나 이들 공법들은 현장 적용 시 객관화된 명확한 적용기준 없이 각 공법에서 제시하고 있는 시공장비 및 사용재료에 의존하여 적용 중이며 이러한 각 개별공법의 기준으로 인하여 현장 관리자들의 품질관리에 어려움이 있는 실정이다. 따라서 본 연구에서는 신구 콘크리트 간 부착력 확보에 가장 핵심적인 현장요소인 경계면 처리 방식과 재료의 부착력 확보에 가장 크게 기여하는 폴리머 함량을 변수로 현장시험을 실시함으로써 시공 전 기존 면처리 공정에서의 효과 분석 및 폴리머 혼입률 변화에 따른 부착강도 성능과의 상관성 검토를 통하여 부착강도의 성능을 개선 할 수 있는 현장시공방법을 도출하고자 하였다.