• Tribology and Lubricants
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• v.38 no.4
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• pp.152-161
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• 2022

Chemical mechanical planarization (CMP) is a technology that planarizes the surfaces of semiconductor devices using chemical reaction and mechanical material removal, and it is an essential process in manufacturing highly integrated semiconductors. In the CMP process, a conditioning process using a diamond conditioner is applied to remove by-products generated during processing and ensure the surface roughness of the CMP pad. In previous studies, prediction of pad wear by CMP conditioning has depended on numerical analysis studies based on mathematical simulation. In this study, using an artificial neural network, the ratio of conditioner coverage to the distance between centers in the conditioning system is input, and the average conditioning density, standard deviation, nonuniformity (NU), and conditioning density distribution are trained as targets. The result of training seems to predict the target data well, although the average conditioning density, standard deviation, and NU in the contact area of wafer and pad and all areas of the pad have some errors. In addition, in the case of NU, the prediction calculated from the training results of the average conditioning density and standard deviation can reduce the error of training compared with the results predicted through training. The results of training on the conditioning density profile generally follow the target data well, confirming that the shape of the conditioning density profile can be predicted.

• Advances in nano research
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• v.14 no.4
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• pp.355-362
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• 2023

Physical exercise, especially intense exercise and high intensity interval training (HIIT) by trampoline, can lead to muscle injuries. These effects can be reduced with intelligent products made of nanocomposite materials. Most of these nanocomposites are polymers reinforced with silicon dioxide, alumina, and titanium dioxide nanoparticles. This study presents a polymer nanocomposite reinforced with silica. As a result of the rapid reaction between tetraethyl orthosilicate and ammonia in the presence of citric acid and other agents, silica nanostructures were synthesized. By substituting bis (4-amino phenoxy) phenyl-triptycene in N, N-dimethylformamide with potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C, the diamine monomer bis (4-amino phenoxy) phenyl-triptycene is prepared. We synthesized a new polyaromatic (imide) with triptycene unit by sol-gel method from aromatic diamines and dianhydride using pyridine as a condensation reagent in NMP. PI readily dissolves in solvents and forms robust and tough polymer films in situ. The FTIR and NMR techniques were used to determine the effects of SiO₂ on the sol-gel process and the structure of the synthesized nanocomposites. By using a simultaneous thermal analysis (DTA-TG) method, the appropriate thermal operation temperature was also determined. Through SEM analysis, the structure, shape, size, and specific surface area of pores were determined. Analysis of XRD results is used to determine how SiO₂ affects the crystallization of phases and the activation energy of crystallization.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.30 no.1
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• pp.43-51
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• 2024

The addition of oxygen scavengers to food products helps to reduce oxygen exposure, thereby mitigating deterioration, including changes in taste, odor, and color, as well as inhibiting microbial growth. Despite the advantages of the existing non-metallic oxygen removal materials in terms of safety for the human body and suitability for use in microwave ovens, their utilization has been limited due to their slow reaction initiation speed. Therefore, in the current study, sodium metabisulfite was impregnated into various porous media, including halloysite nanoclay, activated carbon, montmorillonite, and silica gel. The oxygen scavenger, produced by impregnating silica gel with sodium metabisulfite, demonstrated a 425% improvement in the initial oxygen removal rate compared to pure sodium metabisulfite. Additionally, sachets containing an oxygen-removing composition with an enhanced oxygen removal rate effectively decreased the oxygen concentration to less than 0.5% on the third day of storage in apple packaging, without elevating carbon dioxide levels. Moreover, it proved effective in preventing the browning of the apple surface. Therefore, the SM/SG oxygen-removal composition can be effectively applied to active food packaging by controlling the oxygen concentration within the packaging.

• Journal of Microbiology and Biotechnology
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• v.20 no.1
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• pp.153-160
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• 2010

The present study was carried out for the isolation of bacteriocin-producing enterococci from indigenous sources. Gram-positive enterococci are known for having the ability to produce enterocins with good antimicrobial potential. A total of 34 strains were isolated from processed dairy products of Pakistan and seven out of them were found to be member of genus Enterococcus on selective enumeration. Biochemical and molecular characterization revealed that four of these isolates (IJ-03, IJ-07, IJ-11, and IJ-12) were Enterococcus faecalis and three (IJ-06, IJ-21, and IJ-31) were Enterococcus faecium. Local processed cheese was the source of all enterococcal isolates, except E. faecium IJ-21 and IJ-31, which were isolated from indigenous yoghurt and butter samples, respectively. Bacterial isolates were sensitive to commonly used antibiotics except methicillin and kanamycin. They also lacked critical virulence determinants, mainly cytolysin (cyl), gelatinase (gel), enterococcal surface protein (esp), and vancomycin resistance (vanA and vanB). Polymerase chain reaction amplification identified that enterocin A and P genes were present in the genome of E. faecium IJ-06 and IJ-21, whereas the E. faecium IJ-31 genome showed only enterocin P genes. No amplification was observed for genes that corresponded with the enterocins 31, AS-48, L50A, and L50B, and ent 1071A and 1071B. There were no signals of amplification found for E. faecalis IJ-11, indicating that the antimicrobial activity was because of an enterocin different from those checked by PCR. Hence, the indigenous bacterial isolates have great potential for bacteriocin production and they had antibacterial activity against a variety of closely related species.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.176-185
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• 2016

Yeonsan Ogae has been known as supporting health and high efficacy of treatment. In recent days, as the efficacy of functional peptides has known, the optimization of oligo peptides production and its characteristics from Ogae legs has been performed. Response surface method was used to perform the optimizaion of enzyme hydrolysis. The range of processes was temperature ( 40, 50 and $60^{\circ}C$), pH( pH 6.0, 7.0 and 8.0 ), and enzyme( 1, 2 and 3% ). The degree of hydrolysis, amino acids, molecular weight of products were analyzed. The optimum process of enzyme hydrolysis were determined as temperature $58^{\circ}C$, pH 7.5, and enzyme concentration 3%. At optimum conditions, the degree of hydrolysis after 2 h reaction was 75-80%. The amino acid and were 168.131 mg/100 g, respectively. The molecular weight of products by using MALDI-TOF was ranged from 300 to 1,000 Da.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3712-3719
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• 2011

Confined Pt and $CoFe_2O_4$ nanoparticles (NPs) in a mesoporous core/shell silica microsphere, Pt-$CoFe_2O_4$@meso-$SiO_2$, were prepared using a bi-functional linker molecule. A large number of Pt NPs in Pt-$CoFe_2O_4$@meso-$SiO_2$, ranging from 5 to 8 nm, are embedded into the shell and some of them are in close contact with $CoFe_2O_4$ NPs. The hydrogenation of cyclohexene over the Pt-$CoFe_2O_4$@meso-$SiO_2$ microsphere at $25^{\circ}C$ and 1 atm of $H_2$ yields cyclohexane as a major product. In addition, it gives oxygenated products. Control experiments with $^{18}O$-labelled water and acetone suggest that surface-bound oxygen atoms in $CoFe_2O_4$ are associated with the formation of the oxygenated products. This oxidation reaction is operative only if $CoFe_2O_4$ and Pt NPs are in close contact. The Pt-$CoFe_2O_4$@meso-$SiO_2$ catalyst is separated simply by a magnet, which can be re-used without affecting the catalytic efficiency.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.2
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• pp.131-157
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• 2016

A smog chamber has been an effective tool to study air quality, particularly secondary organic aerosol (SOA), which is typically formed by atmospheric oxidation of volatile organic compounds (VOCs). In controlled environments, smog chamber studies have validated atmospheric oxidation by identifying, quantifying and monitoring products with state-of-art instruments (e.g., aerosol mass spectrometer, scanning mobility particle sizer) and provided chemical insights of SOA formation by elucidating reaction mechanisms. This paper reviews types of smog chambers and the current state of smog chamber studies that have accomplished to find pathways of SOA formation, focusing on gas-particle partitioning of semivolatile products of VOC oxidation, heterogeneous reactions on aerosol surface, and aqueous chemistry in aerosol waters (e.g., cloud/fog droplets and wet aerosols). For future chamber studies, then, this paper discusses potential formation pathways of fine particles that East Asia countries (e.g., Korea and China) currently suffer from due to massive formation that gives rise to fatal health problems.

• Journal of dental hygiene science
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• v.21 no.2
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• pp.119-126
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• 2021

Background: Dental caries is mainly composed of various cellular components and is deposited around the tooth surface and gums, causing a number of periodontal diseases. Streptococcus mutans is commonly found in the human oral cavity and is a significant contributor to tooth decay. The use of antibacterial ingredients in oral hygiene products has demonstrated usefulness in the management of dental caries. This study investigated the anticaries effect of the ethanol extract of Terminalia chebula (EETC) against S. mutans and their cytotoxicity to gingival epithelial cells. Methods: The EETC was prepared from T. chebula fruit using ethanol extraction. Disk diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and colony forming unit (CFU) were analyzed to investigate the antimicrobial activity of the EETC. Glucan formation was measured using the filtrate of the bacterial culture medium and sucrose. Gene expression was analyzed using reverse transcription-polymerase chain reaction (RT-PCR). Cytotoxicity was analyzed via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Results: The antibacterial activity of the EETC was explored using disc diffusion and CFU measurements. The MIC and MBC of the EETC were 10 and 20 ㎍/ml, respectively. EETC treatment decreased insoluble glucan formation by S. mutans enzymes and also resulted in reduced glycosyltransferase B (gtf B), gtf C, gtf D, and fructosyltransferase (ftf), expressions on RT-PCR. In addition, at effective antibacterial concentrations, EETC treatment was not cytotoxic to gingival epithelial cells. Conclusion: These results demonstrate that the EETC is an effective anticaries ingredient with low cytotoxicity to gingival epithelial cells. The EETC may be useful in antibacterial oral hygiene products for the management of dental caries.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.704-709
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• 2021

In the flux used in the batch galvanizing process, the effect of the component ratio of NH₄Cl to ZnCl₂ on the microstructure, coating adhesion, and corrosion resistance of Zn-Mg-Al ternary alloy-coated steel is evaluated. Many defects such as cracks and bare spots are formed inside the Zn-Mg-Al coating layer during treatment with the flux composition generally used for Zn coating. Deterioration of the coating property is due to the formation of AlCl_x mixture generated by the reaction of Al element and chloride in the flux. The coatability of the Zn-Mg-Al alloy coating is improved by increasing the content of ZnCl₂ in the flux to reduce the amount of chlorine reacting with Al while maintaining the flux effect and the coating adhesion is improved as the component ratio of NH₄Cl to ZnCl₂ decreases. Zn-Mg-Al alloy-coated steel products treated with the optimized flux composition of NH₄Cl·3ZnCl₂ show superior corrosion resistance compared to Zn-coated steel products, even with a coating weight of 60 %.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.125-137
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• 2024

In paste backfill mining, cemented coal gangue-fly ash backfill (CGFB) can effectively utilize coal-based solid waste, such as gangue, to control surface subsidence. However, given the pressurized water accumulation environment in goafs, CGFB is subject to coupling effects from water pressure and chloride ions. Therefore, studying the influence of pressurized water on the chlorine salt erosion of CGFB to ensure green mining safety is important. In this study, CGFB samples were soaked in a chloride salt solution at different pressures (0, 0.5, 1.5, and 3.0 MPa) to investigate the chloride ion transport characteristics, hydration products, micromorphology, pore characteristics, and mechanical properties of CGFB. Water pressure was found to promote chloride ion transfer to the CGFB interior and the material hydration reaction; enhance the internal CGFB pore structure, penetration depth, and chloride ion content; and fill the pores between the material to reduce its porosity. Furthermore, the CGFB peak uniaxial compression strain gradually decreased with increasing soaking pressure, whereas the uniaxial compressive strength first increased and then decreased. The resulting effects on the stability of the CGFB solid-phase hydration products can change the overall CGFB mechanical properties. These findings are significant for further improving the adaptability of CGFB for coal mine engineering.