• Journal of the Korean institute of surface engineering
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• v.45 no.1
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• pp.8-14
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• 2012

The effects of the alkali surface modification process on the adhesion strength between electroless-plated Cu and polyimide films were investigated. The polyimide surfaces were effectively modified by alkali surface treatments from the hydrophobic to the hydrophilic states, and it was confirmed by the results of the contact angle measurement. The surface roughness increased by alkali surface treatments and the adhesion strength was proportional to the surface roughness. The adhesion strength of Cu/polyimide interface treated by KOH + EDA (Ethylenediamine) was 874 gf/cm which is better than that treated by KOH and KOH + $KMnO_4$. The results of XPS spectra revealed that the alkali treatment formed oxygen functional groups such as carboxyl and amide groups on the polyimide films which is closely related to the interfacial bonding mechanism between electroless-plated Cu and polyimide films. It could be suggested that the species and contents of functional group on polyimide films, surface roughness and contact angle were related with the adhesion strength of Cu/polyimide in combination.

• Textile Coloration and Finishing
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• v.24 no.2
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• pp.131-137
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• 2012

para-Aramid fibers were treated by low-temperature plasma to improve the adhesion. The surface of para-aramid fibers were treated with gaseous plasma of several discharge power and treatment time in oxygen gas at 1Torr pressure. The treated fibers at low-temperature plasma were taken oxygen-containing functional groups and micro-crator on the surface. The modified fibers were measured by dynamic contact angle analyzer and XPS(X-ray photoelectron spectroscopy). The Interfacial adhesion properties of aramid fabric and polyurethane resin were determined by T-peel test. The surface of aramid fibers were observed by FE-SEM photographs. It was found that surface modification and chemical component ratio of the aramid fibers were improved wettability and adhesion characterization.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.04a
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• pp.97-98
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• 1998

1. Introduction : Polypropylene(PP) membrane is widely used in the field of microfiltration and ultrafiltration. However, the hydrophobicity of PP causes the adsorption of hydrophobic and amphoteric solutes in the feed. Surface modification techniques of membrane through the treatment of hydrophilizing agents, coating of hydrophilic compounds, UV, plasma and high energy irradiation, etc. can have a great effect on propensities to prevent the protein from staining membranes. Among them, the modification to hydophilize membrane surface using UV is very simple and effective. Recently many studies for more effective surface modification have been conducted. Iwata et al. prepared membranes by grafting polyethylene glycol diacrylate macromer(PEGDA) onto polysulfone with plasma using a glow discharge reactor which prevent the oil from staining the membrane. The primary mechanism contributing to the membranes is preventing the oil from directly contacting the surface of the membrane as the PEGDA chains dissolved into emulsion. To evaluate their feasibility for use as a anti-fouling separation membrane, we prepared hydrophilic membranes by UV irradiation method and investigated their characteristics.

• Journal of Microbiology and Biotechnology
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• v.11 no.1
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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.

• Wind and Structures
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• v.21 no.3
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• pp.331-352
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• 2015

A series of wind tunnel tests were conducted on tapered super high-rise buildings with a square cross section by applying synchronous pressure measurement technology. The effects of global strategy of chamfered modification on aerodynamic loads and wind-induced responses were investigated. Moreover, local aerodynamic strategies of opening a ventilation slot in the corner of equipment and refuge floors were carried out. Results show that the global strategy of tapered elevation increased the vortex shedding frequency, but reduced vortex shedding energy, leading to reduction of across-wind aerodynamic loads and responses. Chamfered modification suppressed the across-wind vortex shedding effect on tapered buildings. Opening the ventilation slot further suppressed the strength of vortex shedding and reduced the residual energy related to vortex shedding in aerodynamic loads of chamfered buildings. Finally, the optimized locations of local aerodynamic strategies were suggested.

• Carbon letters
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• v.4 no.1
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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.

• Steel and Composite Structures
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• v.14 no.6
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• pp.523-545
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• 2013

In this study, the effect of presence and distribution of masonry infill walls on the mid-rise steel frame structures having soft ground storey was evaluated by implementing finite element (FE) methods. Masonry infill walls were distributed randomly in the upper storey keeping the ground storey open without any infill walls, thus generating the worst case scenario for seismic events. It was observed from the analysis that there was an increase in the seismic design forces, moments and base shear in presence of randomly distributed masonry infill walls which underlines that these design values need to be amplified when designing a mid-rise soft ground storey steel frame with randomly distributed masonry infill. In addition, it was found that the overstrength related force modification factor increased and the ductility related force modification factor decreased with the increase in the amount of masonry infilled bays and panels. These must be accounted for in the design of mid-rise steel frames. Based on the FE analysis results on two mid-rise steel frames, design equations were proposed for determining the over strength and the ductility related force modification factors. However, it was recommended that these equations to be generalized for other steel frame structure systems based on an extensive analysis.

• Journal of the Korean institute of surface engineering
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• v.37 no.1
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• pp.5-12
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• 2004

The enhancement of adhesion for Cu film on polycarbonate (PC) surface with the $Ar/O_2$ gas plasma treatment and dc-bias sputtering was studied. The plasma treatment with this reactive mixture changes the chemical property of PC surface into hydrophllic one, which is shown by the variation of contact angle with surface modification. The micro surface roughness that also gives the high adhesive environment is increased by the $Ar/O_2$ gas plasma treatment. These results were observed distinctly from the atomic force microscopy (AFM). The negative substrate dc-bias effect for the Cu adhesion on PC was also investifated. Accelerated $Ar^{+}$ lons in sheath area of anode bombard the bare surface of PC during initial stage of dc bias sputtering. PC substrate. therefore, has severe roughen and hydrophilic surface due to the physical etching process with more activated functional group. As dc-bias sputtering process proceeds, morphology of Cu film shows better step coverage and dense layer. The results of peel test show the evidence of superiority of bias sputtering for the adhesion between metal Cu and PC.C.

• Journal of Korea Foundry Society
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• v.34 no.5
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• pp.156-161
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• 2014

This study is focused on the effect of $Al_2Ca$ as a modifier on eutectic Si modification of A356 alloy. Microstructural observation was carried out for as-cast, as-solution treated and as-aged samples. Solution treatment and aging were performed for 2, 4, 6 and 10 hrs at $540^{\circ}C$ and $170^{\circ}C$, respectively. Although A356 alloy, which $Al_2Ca$ was added, has no significant difference in as-cast phases with normal A356 alloys, it shows much more modified eutectic Si, grain refinement and improved tensile property both in as-cast and as-heat treated conditions. TGA result shows that $Al_2Ca$ added A356 alloy has a certain improvement in oxidation resistance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.834-837
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• 2005

Structural Dynamics Modification (SDM) is a very effective technique to improve structure's dynamic characteristics by adding or removing auxiliary structures, changing material properties and shape of structure. Among those of SDM technique, the method to change shape of structure has been mostly relied on engineer's experience and trial-and-error process which are very time consuming. In order to develop a systematic method to change structure shape, surface grooving technique is studied and successfully applied to HDD cover model. At first, to check the effect of mesh size, surface grooving technique was tested to the fine HDD cover FEmodel. And fur the more efficient method, the algorithm is modified. Removing the low-valued modal strain energy element among the target domain, computational effort can be greatly reduced and the result of simulation is similar with the other simulation result.