• Tribology and Lubricants
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• v.31 no.6
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• pp.287-293
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• 2015

Laser surface texturing (LST), a surface engineering modification, has been considered as one of the new processes used to improve tribological characteristics of materials by creating artificially patterned microstructure on the contact surface of mechanical components. In LST technology, the laser is optimized to obtain or manufacture the dimples with maximum precision. The micro-dimples reduce the coefficients of friction and also improve the wear resistance of materials. This study investigates the effect of dimple density is investigated. For this purpose, a ball-on-disc type tester is used with AISI 52100 bearing steel as the test material. Discs are textured with a 5% and 10% dimple density. Experimental work is performed with normal loads of 5 N, 10 N, and 15 N under a fixed speed of 150 rpm at room temperature. The effect of the textured surface is compared to that of the untextured one. Experimental results show that the textured surface yields lower friction coefficients compared to those of untextured surfaces. Specifically, the 10% dimple density textured surface shows better friction reduction behavior than the 5% dimple density textured sample, and has an 18% improvement in friction reduction compared with the untextured samples. Microscopic observation using a scanning electron microscope (SEM) shows that the major friction mechanisms of the AISI 52100 bearing steel are adhesion, plastic deformation, and ploughing.

• Journal of Surface Science and Engineering
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• v.26 no.4
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• pp.192-202
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• 1993

The characteristics of the high-performance ceramic coatings fabricated on the optimum processings con-ditions for the atmospheric plasma spraying are evaluated by various material tests and analyses. The opti-mum processing parameters for the plasma spraying are determined by using the two-level orthogonal arrays of fractional factorial testing method as a statistical approach. Material tests for the coating specimens are carried out to evaluate microstructure, hardness, adhesion strength, and deposition efficiency. The properties of Al2O3-13%TiO2 coating are discussed with regard to the effective processings parameters. The decarburization effects of WC-12%Co coating is examined by XRD analysis in terms of the arc power and the secondary gas species. The hardness of Al2O2-13%TiO2 coating is increased with the arc power and shows the maximum value at around 40 lpm of Ar gas flowrate, which appears to be the most critical parame-ter on the deposition efficiency. For reducing the decarburization of WC-12%Co coating, the injection of inert He gas instead of reactive H2 gas as a secondary gas is more effective than the dropping of arc power to lessen the plasma enthalpy.

• Land and Housing Review
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• v.12 no.4
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• pp.119-125
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• 2021

The study presents the ductility reinforcement effect of the RC bending member using the CFRP Grid as an experimental result. Experimental variables include a non-reinforced RC bending member (ORI), a bottom reinforced RC bending member (REB), and an RC bending member reinforced at the bottom and side (REBS). The experiment was carried out with four points bending test. As a result of the experiment, it was confirmed that the maximum bending strength increased by 17-20% through reinforcement. In addition, the ductility index calculation results confirmed that the ductility index of REB and REBS increased by 2 and 3 times, respectively, compared to the ORI.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.129-133
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• 2019

TiN thin films were fabricated using an unbalanced magnetron sputtering (UBMS) system, and their structure and surface characteristics as well as their optical and tribological properties were evaluated. The hardness, elastic modulus, adhesive force, surface roughness, and transmittance of the Ti thin films fabricated using the UBMS system were 11.5 GPa, 103 GPa, 27.5 N, 2.45 nm and 20%, respectively. The TiN films prepared with various proportions of nitrogen as the reaction gas exhibited maximum values for the hardness, elastic modulus, critical load, RMS roughness and transmittance of approximately 19.2 GPa, 182 GPa, 27.3 N, 0.98 nm, and 85%, respectively. Moreover, the TiN thin film fabricated under the condition of 30 sccm nitrogen gas showed the optimal physical properties. In summary, the TiN thin films fabricated using the UBMS system exhibited excellent hardness, elastic modulus, adhesion, and smooth surface in addition to good hydrophilic properties.

• Journal of the Korean Applied Science and Technology
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• v.37 no.6
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• pp.1627-1634
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• 2020

In this study, water-based acrylic adhesives as copolymers with acrylic acid, 2-hydroxyethyl acrylate were synthesized using ethyl acrylate, 2-ethylhexyl acrylate, and lauryl methacrylate as the main monomers. Prepared water-based acrylic adhesive was compared to physical properties such as solid content, average particle size distribution, initial adhesive force, maximum adhesive force, peel strength, and heat resistance.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.1
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• pp.9-14
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• 2023

The application of starch-based films is limited by the poor water vapor barrier and mechanical properties. In this study, plasticized octenyl-succinated corn starch (OTPS) was mixed into Poly (butylene adipate-co-terephthalate) (PBAT) with various concentration (0/0.25/0.5/0.75 wt%) of epoxidized soybean oil (ESO) to enhance the mechanical properties and the hydrophobicity of blends. Tensile Strength and elongation at break of PBAT/OTPS film was slightly strengthened as the added ratio of ESO raised to 0.5 wt%, yet lessened again in 0.75 wt% sample. The yield strength and elastic modulus were highest in 0.25wt% of ESO added. In thermal properties, the melting temperature (T_m) and crystallization temperature (T_c) were highest at ESO 0.25 and the maximum degradation temperature (T_max) of components of the films were developed as ESO added. Also, it has been proved that the addition of hydrophobic substances reduces the hydrophilicity of the film by contact angle. This suggests the use of epoxidized oil for preparing films based on high TPS content allows obtaining enhanced interfacial adhesion. This study confirmed that ESO acts as a compatibilizer between OTPS and PBAT to improve the mechanical properties and hydrophobicity of the sample. The sample containing 0.5wt% of ESO was the most suitable for packaging application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.118-125
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• 2017

In this study, we examined the bond performance of FRP Hybrid Bars. FRP Hybrid Bars are developed by wrapping glass fibers on the outside of deformed steel rebars to solve the corrosion problem. The surface of the FRP Hybrid Bars was coated with resin and silica sand to enhance its adhesion bonding performance with concrete. Various parameters, such as the resin type, viscosity, and size of the silica sand, were selected in order to find the optimal surface condition of the FRP Hybrid Bars. For the bonding test, FRP Hybrid Bars were embedded in a concrete block with a size of 200 mm3 and the maximum load and slip were measured at the interface between the FRP Hybrid Bar and concrete through the pull-out test. From the experimental results, the maximum load and bond strength were calculated as a function of each experimental variable and the resin type, viscosity and size of the silica sand giving rise to the optimal bond performance were evaluated. The maximum bond strength of the specimen using epoxy resin and No. 5 silica sand was about 35% higher than that of the deformed rebar.

• Journal of Life Science
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• v.34 no.10
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• pp.691-700
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• 2024

Frutobacillus spp. strains (Fs) were isolated from honeybee larvae to evaluate their functionality and potential use as probiotics. Anti-microbial activity was generally observed in F strains against Gram-negative, Gram-positive, and yeast strains, with F2 and F3 being superior, particularly F2. Kerosene emulsification was similarly observed in strains other, except for F4. Emulsification analysis based on carbon sources showed that F2 had high emulsification in the presence of fructose but lower than the standard strain and 16S rDNA sequence analysis revealed that the F2 was identified as Fructobacillus fructosus. The growth curve of F2 showed maximum growth at 18 hr, followed by a slight increase. Furthermore, antimicrobial activity and pH showed maximum and minimum values at 18 hr, respectively, and remained constant thereafter. Lactic acid content showed a slight decrease after reaching its maximum value at 24 hr of culture. Acid resistance was observed up to pH 2.5, but completely lost at pH 2.0. Bile acid resistance was generally strong. F2's adhesion to mucin was higher compared to S. Typhimurium, which increased until 18 hr of culture and then decreased. Enzyme activity according to anaerobic culture time was high for carboxymethylcellulase (CMCase), avicelase, and mannase, regardless of the presence of fructose. Auto- and co-aggregation were higher compared to the standard strain, and surface hydrophobicity was high for chloroform, which indicates electron donor properties. Therefore, the Fructobacillus fructosus F2 can be considered a potential probiotic due to its excellent anti-microbial, emulsification, acid resistance, bile resistance, CMCase, mannase, and auto- and co-aggregation properties.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.41-49
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• 2014

In this study, experimental research was carried out to evaluate the structural performance of the reinforced concrete beam using hybrid retrofitting with two materials (groove and embedding FRP rod, CFRP sheet) in existing reinforced concrete buildings. Seven reinforced concrete beams, retrofitted groove and embedding FRP rod (NER series) and groove and embedding FRP rod with CFRP sheet (NERL series), and standard specimen (NBS) were constructed and tested under monotonic loading. Design parameters of test specimens are the amount of groove and embedding FRP rod and lapping CFRP sheet. Test results showed that the maximum load carrying capacity of specimens with groove and embedding FRP rod and groove and embedding FRP rod with CFRP sheet (NERL series) were increased the by 12~46% and 22~77% respectively in comparison with the standard specimen NBS. Test specimens NER series were failed with the adhesion slip and concrete cover separation. And test specimens NERL series were failed with the adhesion slip due to the confining effect of lapping CFRP sheet.

• Journal of Adhesion and Interface
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• v.10 no.4
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• pp.191-198
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• 2009

UV-curable aliphatic epoxy acrylates were prepared by the reaction of glycerol diglycidyl ether (GDE) with 2-carboxyethyl acrylate (2-CEA) or 2-hydroxyethyl acrylate (2-HEA). The structures of the epoxy acrylates were characterized by FT-IR, $^1H$-NMR, and $^{13}C$-NMR and the yield was obtained by prep-LC. The UV- and the thermal-curing behaviors of the product were investigated using photo-DSC and DSC, respectively. The reactivity of 2-CEA was higher than 2-HEA and the yield of the product (GEA-C) which was prepared using 2-CEA was about 83%. The maximum UV-curing time ($T_{max}$) of the GEA-C contained non-reactive components and by-product was about 10 seconds. The GEA-C showed low color difference (${\Delta}E^*$), low viscosity, and good thermal stability - its value was 2.51, 192 cps, and $299^{\circ}C$ (at 5% weight loss), respectively. The activation energies ($E_a$) of thermal-curing reaction calculated from Kissinger and Ozawa-Flynn-Wall method were 91~92 kJ/mol.