Earticle

본 연구에서는 기존구조물에 대한 보수와 복구에 보강을 위하여 복합재료의 사용이 증가하고 있는 상황에서 방재의 개념에도 부합하는 탄소섬유보강재를 이용하여 기존금속재와 접합(접착방식)을 통한 강도증진효과를 연구하였다. 특히 실험을 통하여 강-탄소섬유보강재로 이루어진 복합재 거동을 파악하였으며 여기에 적절한 시험을 위한 새로운 형태의 시험편을 제작하였다. 접합재로 레진을 도포하는 방법을 달리하고 거동을 비교하기 위하여 표면처리가 다른 시험편을 각각 고려하여 시험한 결과 강성보강효과는 물론 일체거동의 특성이 잘 나타남을 알 수 있었다.

The use of advanced composite materials in strengthening and repair of existing structures is increasing rapidly. One specific area in which the technique has been introduced lately is the strengthening of metallic structures with bonded carbon-fibre laminates. In this paper, the behaviors of composite steel-CFRP members is studied experimentally. A new type of test specimen has been developed for this purpose. By examining different combination of CFRP-laminates and adhesives, different types of fracture mode could be examined. The tested composite elements also displayed different behavior and a large difference in strength and ductility could be observed.

This paper presents the dynamic magnetoelastic stress intensity factors of a Yoffe-type moving crack at the interface between two dissimilar soft ferromagnetic elastic half-planes. The solids are subjected to a uniform in-plane magnetic field and the crack is opened by internal normal and shear tractions. The problem is considered within the framework of linear magnetoelasticity. By application of the Fourier integral transform, the mixed boundary problem is reduced to a pair of integral equations of the second kind with Cauchy-type singularities. The singular integral equations are solved by means of a Jacobi polynomial expansion method. For a particular case, closed-form solutions are obtained. It is shown that the magnetoelastic stress intensity factors depend on the moving velocity of the crack, the magnetic field and the magnetoelastic properties of the materials.

점변일차원이층류(漸變一次元二層流)모델로서의 염수(塩水)쐐기형상(形狀)의 계산(計算)을 행함에 있어서 필요(必要)한 계면저항계수(界面低抗係數)의 평가수단(評價手段)에 대(對)하여 논(論)한다. 예(例)를 들면, 폭(幅)이 좁은 실험수로(實驗水路)에서 얻어진 염수(塩水)쐐기의 형상(形狀)에 의해 계면저항계수(界面低抗係數)를 역산(逆算)하는 경우는 실제(實際)의 하천(河川)에서는 무시(無視)할 수 있는 수로(水路)의 측벽(側壁)의 영향(影響)을 보정(補正)하지 않으면 안된다. 본연구(本硏究)에서는 이러한 점(點)을 고려(考慮), 정상(定常) 염수(塩水)쐐기의 형상(形狀) 및 계면저항계수(界面低抗係數)에 미치는 수로(水路)의 측벽(側壁)의 영향(影響)을 밝힌다.

In order to determine the form and the length of saline wedge, it is necessary to evaluate interfacial friction factor. Hetherto one dimensional two-layer flow model which assumed pressure as the hydrostatic pressure distribution has been well used to the calculation of saline wedge form, it just then stands in need of relevant interfacial friction factor. For example, in the case where we calculate back to interfacial friction factor out of saline wedge form obtained at a laboratory open channel with comparatively narrow width, it is needed to correct the side-wall effect of a channel, if generally negligible in the river. In this study, we confirmed the influence of a side-wall upon the lateral velocity distributions at laboratory channel and then examined in detail the value of interfacial friction factor in the case where it was corrected by the side-wall effect and not corrected. And then we make clear the influence of a side-wall upon the arrested saline wedge and interfacial faction factor from these results.

The purpose of this study was to improved the durability of a improved movable weir by replacing the improved movable weir's metal gate with a hybrid steel/glass fiber reinforced polymer composites panel gate. Because the metal gate of a improved movable weir is always in contact with water, its service life is shortened by corrosion. This study made four type of hybrid steel/glass fiber reinforced polymer composites panel gate with different steel gate surface deformation (control, sand blast, scratch and hole), flexural. Fracture properties tests were performed depending on the steel gate surface deformation. According to the test results, the flexural behavior, flexural strength and fracture properties of hybrid steel/glass fiber reinforced polymer composites panel gate was affected by the steel panel gate surface deformation. Also, the sand blast type hybrid steel/glass fiber reinforced polymer composites panel gate shows vastly superior flexural and fracture performance compared to other types.

Interfacial cracks in a piezoelectric layer bonded to dissimilar elastic layers under the combined anti-plane mechanical shear and in-plane electrical leadings are considered. By using Fourier cosine transform, the mixed boundary value problem is reduced to a singular integral equation which is solved numerically to determine the stress intensity factors. Numerical results for the effects of the material properties and layer geometries on the stress intensity factors are obtained.

CO2-EOR공법에서 혼화압력측정은 중요한 과정 중 하나로 CO2 주입의 최적설계를 위해서는 혼화압력인 MMP(최소혼화압력)와 FCMP(초기접촉혼화압력) 측정이 필수적이다. 계면장력소멸방법은 혼화압력을 측정하는 방법 중 하나로 적은 양의 오일을 이용하면서 비용효율적이고, 정확한 방법이다. 혼화압력측정 연구는 대부분 무용해 가스오일(Dead oil)을 이용하는 방식으로 이루어져 왔으나 본 연구에서는 저류층 조건을 정확히 모사하기 위해 용해 가스를 오일과 혼합하여 용해가스오일(Live oil)로 제조하여 진행하였으며, 용해가스의 양과 온도에 따른 MMP와 FCMP 값을 측정하였다. 용해가스오일은 CCE(동성분리팽창)실험을 통해 기포점 압력을 측정하여, 공인된 기관인 LEMIGAS의 검증된 자료와 비교함으로써 제조된 오일의 유사성을 확인하였다. 계면장력소멸실험에서는 메탄가스의 용해도가 증가함에 따라 MMP, FCMP 값이 증가하였으며, 온도가 증가하면 무용해가스오일 및 용해가스오일/CO2, 두 시스템 모두 MMP, FCMP 값이 큰 폭으로 증가함을 확인하였다.

Miscibility condition is an important parameter for CO2-EOR process. In order to optimize the CO2 injection process, miscibility should be tested in advance. VIT method is the one of the main methods for evaluating miscibility condition. It is cost effective, accurate and requires smaller amount of crude oil sample and time saving experiment. Many experiments have been implemented using dead oil and we determined miscibility condition using VIT method with CO2-live oil at reservoir condition. MMP and FCMP were estimated according to the methane solubility and various temperature changes. Pb was measured to verify the reliability of the synthetic live oil. Pb is compared to the data from authorized organization (LEMIGAS) and validated reliability of synthetic live oil. VIT experiment results show that the amount of solution gas increases both MMP and FCMP. When the temperature increases, MMP and FCMP increased rapidly for both dead oil and live oil experiment.

본 연구는 재활용 PP/EVOH 기반 다층 시트에 SEBSg- MAH를 0, 10, 20 wt.% 첨가했을 때 미치는 영향을 종 합적으로 평가했다. 실험 결과, SEBS-g-MAH 함량이 증가함에 따라 OTR 및 WVTR이 유의미하게 감소하여 기체 및 수분 차단성이 향상됨을 확인했다. TEM 분석에서는 SEBS-g-MAH가 첨 가되지 않은 시편의 불균일한 EVOH 도메인이 SEBS-g-MAH 첨가 시 나노 수준으로 균일하게 분산되는 현상이 나타났다. FTIR 분석을 통해서는 SEBS-g-MAH가 첨가된 시편의 1735 cm1 부근에서 에스터 결합(C=O) 흡수 피크 가 뚜렷이 관찰되었다. 이는 SEBS-g-MAH의 말레산 무수 물(MAH) 작용기가 EVOH의 하이드록실기(-OH)와 화학적 으로 반응해 안정한 공유 결합을 형성했음을 입증한다. 이러한 결과는 SEBS-g-MAH의 양친매성(amphiphilic) 구조가 EVOH와의 화학적 상호작용과 PP와의 물리적 상호 작용을 통해 '분자적 교량(molecular bridge)' 역할을 수행했 기 때문으로 해석된다. 이로 인해 계면 안정화, 상 분리 억 제, 도메인 미세화가 이루어졌고, 결과적으로 복합계의 열 역학적 안정성 향상과 응력 전달 효율 증대를 가져왔다. 특 히 SEBS-g-MAH의 함량 증가는 계면 친화력 강화와 미세 구조 안정화를 촉진하여, 재활용 과정에서도 장기적인 산소 및 수분 차단 기능 유지를 가능하게 했다. 결론적으로, 본 연구는 SEBS-g-MAH가 재활용 PP/EVOH 시스템의 분산 상태 및 차단 성능을 개선할 수 있는 효과 적인 전략적 계면 개질제임을 명확히 제시한다. 이는 PP/ EVOH 재활용 포장재 개발에 있어 지속 가능한 고성능 소 재 솔루션으로서의 활용 가능성을 보여주는 중요한 근거가 될 것이다.

This study examines the influence of SEBS-g-MAH (styrene ethylene butadiene styrene grafted maleic anhydride) content (0, 10, and 20 wt%) on the oxygen and moisture barrier properties, as well as the morphological and chemical structural changes in multilayer plastics composed of recycled polypropylene (PP) and ethylene vinyl alcohol (EVOH). Oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) analyses revealed a gradual decrease in permeability with increasing SEBS-g-MAH content, indicating improved barrier performance. Fourier-transform infrared (FTIR) spectroscopy confirmed the formation of ester bonds between the anhydride groups of SEBS-g-MAH and the hydroxyl groups of EVOH, as evidenced by a distinct absorption peak near 1735 cm⁻¹. This covalent interaction suggests enhanced interfacial compatibility. Transmission electron microscopy (TEM) revealed significant morphological evolution: without SEBS-g-MAH, EVOH domains were irregularly and coarsely dispersed within the PP matrix, whereas the addition of 10 wt% SEBS-g-MAH led to smaller domains and improved interfacial diffusion. At 20 wt%, the EVOH phase was finely and uniformly distributed, indicating stabilized phase morphology. These improvements in both chemical and morphological compatibility contributed to reduced interfacial tension, suppressed phase separation, and enhanced blend homogeneity. Overall, the results highlight the effectiveness of SEBS-g-MAH as a compatibilizer for recycled PP/EVOH plastics, providing a promising strategy for the development of sustainable, high-performance packaging materials.

적외선 대표소재인 Ge기판 위에 실리콘(Si) 계면층을 가지고 있는 다이아몬드 카본 상(DLC) 박막 시편과 Si 계면 층을 가 지고 있지 않는 DLC 시편 2종을 준비하여 계면의 접합력 및 적외선 성능을 연구하였다. 푸리에 변환 적외선 분광법(FTIR)에 의한 분석결과 Si 계면층을 가지고 있는 DLC 시편은 800-1400 cm-1 파장에서 최대 90 % 이상의 적외선 투과성능이 관찰 되었다. 또한 Ge 기판과 DLC 박막사이에 Si 계면층을 가지고 있는 DLC 박막은 Si 계면층을 가지고 있지 않은 DLC 코팅의 Ge 기판보다 상대적으로 우수한 계면 접합력이 관찰되었다. 투과전자현미경(TEM)을 활용하여 박막과 Si 계면 층의 계면 구 조를 관찰한 결과 비정질의 Si 계면층이 비정질의 카본 구조 위에 잘 증착되어 계면 접합력의 결과를 가져왔음을 확인하였으 며 음향 방출 긁힘 시험기를 사용하여 계면 접합력 향상을 또한 확인하였다. 그러므로 이러한 결과는 DLC 박막의 적외선 광 학 창 코팅재료로써의 가능성을 명확하게 보여준다.

We conducted a study involving the preparation of two types of diamond-like carbon(DLC) film-coated germanium(Ge), a representative material in infrared systems, with the aim of investigating both interface adhesion a nd i nfrared properties o f the DLC film. One set of s amples c omprised DLC-coated G e with a silicon(Si) interlayer, while the other set consisted of DLC-coated Ge without a Si interlayer. The Fourier-transform infrared(FTIR) spectrum of the DLC-coated Ge with a Si interlayer exhibited maximum transmission exceeding 90% within the wavelength range of 800-1400cm-1. Furthermore, it was observed that the adhesion of the DLC-coated Ge substrate with a Si interlayer was notably stronger compared to the DLC-coated Ge samples lacking the Si interlayer. The interface structure between the DLC film and the Si intermediate layer was throughly examined using transmission electron microscopy(TEM). The amorphous carbon structure of the DLC film exhibited robust adherence to the amorphous carbon Si intermediate layer, which consequently by acoustic emission scratch testing. Consequently, this results strongly underscore the potential of DLC films for applications as infrared window coatings.

The effect of Nb on interfacial bonding characteristics of Ni-Cr alloy for porcelain fused to metal crown (PFM) has been studied in order to investigate oxide layer. A specimens , which is 0.8 in thickness, were fired at 1,000 with four tests such as air, vacuum, air for 5 minutes and vacuum for 5 minutes in order to examine an oxide behavior of alloy surface generated by the adding of Nb to be controlled at a rate of 0, 1, 3 and 5. It observed oxide film form of the fired specimens with optical microscope and scanning electron microscope (SEM), and chemical formation of them with energy disperse X-ray spectroscopy (EDX). The other specimens, which is 2 in thickness, were fired at 1,000 with air and vacuum in order to analyze the diffusion behaviors of alloy-porcelain interface by X-ray dot mapping. The results of this study were as follows: 1. The observation of microstructure of specimens by SEM showed that the more Nb content is high, the more much intermediate compound of rich Nb is observed. 2. The surface morphology of oxide film is most dense in 3% Nb. The heat treatment in air constitutes denser oxide film than heat treatment under vacuum. 3. The diffusion behavior of oxide layer by X-ray dot mapping showed that Si, Al of porcelain diffuse toward metal.

This study reports the results of a study on the interfacial properties of glycereth-25 PCA isostearate and its skin care cosmetic formulation application.This raw material is an amino acid-based surfactant, which is a natural moisturizing factor (NMF), and has properties of both soluble and emulsifying power and moisturizing effects. The organic property value (OV) of this raw material was 1460, the inorganic property value (IV) was 2085, and the obtained IOB value was 1.42. Since the IOB value was 1 or more, it was interpreted as having excellent hydrophilic available thermal power. In addition, it was found that the HLB value obtained by calculating the molecular weight of lipophilic and hydrophilic was 14.0 to 14.4 (average 14.2). It was found that the concentration of the solubilizing agent used to dissolve 0.1% of Bergamot oil was transparently dissolved at 0.5%. In addition, the concentration of this surfactant used to emulsify 20% of caprylic/capric triglyceride oil was capable of stable emulsification at 2%. As an application in skin care cosmetics, it is effective in developing transparent solubilized formulations and is expected to be widely applied as a main surfactant in developing moisturizing emulsified lotions, essence, and cream formulations. As a surfactant with strong hydrophilicity, it is expected to be effective in making a D-phase emulsification nanoemulsion.

A two-phase flow in mini-channels is consist with various flow regimes (such as bubble slug, annular, churn flow) according to gas and liquid phase flow rates. A previous researches revealed that in a case of slug flow in hydrophobic mini-channels, gas and liquid phase are perfectly separated by interfaces and triple contact line. In this study, the single dry slug flow experiments in circular mini-channel (D = 1.018 mm) are conducted to observe interfacial break-up phenomena in high capillary number range (Ca < 0.02). The slug is consist with D.I. water or D.I. water-ethanol binary mixtures (5% and 10%, mole fraction). On the base of previous researches, we calculate the pressure drop at moving triple contact line. In an addition, a single dry slug flow is visualized by using high-speed camera. Through the experiment, three regimes of pressure drop are observed; steady, loss, separation. As a result, criteria between steady and loss regimes is closely related to capillary number, and criteria between loss and separation regimes is related to surface tension.

The suspension polymerization of styrene was carried out to obtain the narrow-size distribution of particle by using poly(vinyl alcohol) (PVA) as suspension stabilizer according to the degree of hydrolysis and the molecular weight. The stabilizing properties of suspension are also dependent on the interfacial tension of aqueous solution when PVA is added. When the polymerization process was carried out with low hydrolyzed PVA, it gave single, well-defined particles, while high hydrolyzed PVA gave clusters. The size of particle produced in this study ranged between 5 and 10. The suspending agent, PVA, influences on the drop size and drop stability, When the molecular weight of PVA is increased, the drop size decreases and the drops become more stable toward coalescence. An increase in the PVA concentration decreases the mean drop size and narrows the drop size distribution.

In this study, the effect of downward inclined interface about interfacial crack of bimaterials are discussed. The fracture parameter are analyzed by finite element method of the ANSYS. The energy release rates, displacement jump and stress distribution were analyzed as the gradient variation of inclined interfaces. As a results, in case of positive shear displacement was applied, the energy release rates not varied with gradient of inclined interface increasing. However in case of negative shear displacement was applied, the energy release rates decreased with gradient of inclined interface increasing. Due to the inclined interface contact, the shielding effect relatively increased as the gradient of inclined interface was increased.

In this study, the effect of interface friction coefficient about interfacial crack of bimaterials are discussed. The fracture parameters are analyzed by finite element method using ANSYS. With increasing the interface friction coefficient, normal crack opening displacements and normal stress distributions are analyzed. In this case with surface contact in interface crack, the energy release rates decreases with interface friction coefficient increasing. Increase in the friction coefficient of the crack surface are tend to suppressing for the initiation of interfacial crack. In this case with surface non-contact, the energy release rates are constant with interface friction coefficient increasing, and so the friction coefficient are not related with the fracture parameter.

In this study, the crack initiation and propagation behavior of interfacial crack in bimaterial are discussed. Normal crack opening displacements(NCOD) and stresses are analyzed by finite element method using ANSYS and used for extracting fracture parameters. The energy release rates can not explained the initiation and crack propagation velocity of interfacial crack. Initial velocity of crack propagation is dependent upon the normal and shear stress behind of crack tip. The crack propagation velocity of interfacial crack is very dependent upon the normal and shear stress behind of crack tip. In case of negative shear displacements increase in interfacial crack, initiation delay of crack propagation is dependent upon the negative shear stress ahead of crack tip due to the suppressing of crack opening. In case of positive shear displacements increase in interfacial crack, initiation delay of crack propagation is dependent upon the stress behind of crack tip due to the stress decrease. The fracture toughness increase is due to the initiation delay of crack propagation.

The chemistry of mussel adhesion has commanded the focus of much recent research activity on wet adhesion. By comparison, the equally critical adhesive processing by marine organisms has been little examined. Using a mussel-inspired coacervate formed by mixing a recombinant mussel adhesive protein (fp-151-RGD) with hyaluronic acid (HA), we have examined the nanostructure, viscosity, friction, and interfacial energy of fluid-fluid phase-separated coacervates using the surface forces apparatus and microscopic techniques. At mixing ratios of fp-151-RGD:HA resulting in marginal coacervation, the coacervates showed shear-thickening viscosity and no structure by cryo-transmission electron microscopy (cryo-TEM). However, at the mixing ratio producing maximum coacervation, the coacervate showed shear-thinning viscosity and a transition to a bicontinuous phase by cryo-TEM. The shear-thinning viscosity, high friction coefficient (>1.2), and low interfacial energy (<1mJ/m2) observed at the optimal mixing ratio for coacervation are promising delivery, spreading and adhesion properties for future wet adhesive and coating technologies.

Photo-responsive surfactants obtained from Tween 20 and coumarin derivatives, which attached on the ends of PEO fragment of Tween 20 through ester or ether bond. The molar ratios of the coumarin residues to Tween 20 in both of these two conjugates having ester bond (TCES) and ether bond (TCET) were about 1:1.Coumarin residues of TCES and TCET could be photo-dimerized, and the photo dimerization degrees were in the order of TCET >TCES >free coumarin derivative. The air/water interfacial activity was in the order of TCET >Tween 20 >TCES, and the interfacial activities of TCES and TCET increased with the UV irradiation time. This possibly comes from the photo-dimerization of the couamrin residues on Tween 20. The decrease in the interfacial activity of TCES was slightly greater than that of TCET, probably because of the differences in the length, the polarity and the flexibility of the linker between coumarin residue and Tween 20.

연질 접착제에 대한 최근의 연구는 그들의 화학적 또는 기계적 구조가 살아있는 조직과 어떻게 강하게 상호작 용하는지를 깊이 이해하고자 했다. 그 목적은 급성 또는 만성 질환 환자의 충족되지 않은 요구를 최적으로 해결하는 것이다. 정전기(수소 결합)와 기계적 상호 작용(모세관 보조 흡입 스트레스)을 모두 포함하는 시너지 접착은 조직에 대한 장기간의 불안정한 결합과 관련된 과제를 극복하는 데 효과적인 것으로 보인다. 본 연구에서는 화학 잔류물이 없는 접착의 정전적이고 기계적으로 시너지 메커니즘을 기반으로 한 로봇 그리퍼 인터페이스용 하이브리드 구조를 보고한다. 메커니즘을 추론하기 위해 하이브리드 구조를 기반으로 한 열역학적 모델을 분석하였다. 모델은 엘라스토 머 구조에 내장된 하이드로젤의 열역학적으로 제어된 팽창이 습한 표면과의 지속가능한 접착력 향상과 박리 방향의 화학적 잔류물 없는 탈착력을 향상시킨다는 실험 결과를 뒷받침했다.

Recent research on soft adhesives has sought to understand in depth how their chemical or mechanical structures interact strongly with living tissues. The aim is to optimally address the unmet needs of patients with acute or chronic diseases. Synergy adhesion, which includes both electrostatic (hydrogen bonds) and mechanical interactions (capillary stress), appears to be effective in overcoming challenges related to long-term unstable bonds to wet surfaces. Here, we report electrostatic and mechanically synergistic mechanisms of adhesion without chemical residues. To infer the mechanism, a thermodynamic model based on custom combination adhesives has been proposed. The model supported experimental results that thermodynamically controlled swelling of hydrogels embedded in elastomeric structures improves biofluidic insensitive on-site adhesion to wet surfaces and improves detachment without chemical residues in the direction of peeling.