• Korean Journal of Heritage: History & Science
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• v.46 no.4
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• pp.78-89
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• 2013

For safe conservation treatment of damaged accessory relics that were unearthed, the quality of the material should be accurately identified through a nondestructive analysis and failure analysis. This study provides the basic conservational scientific data regarding material analyses and conservation treatment that were conducted for 11 relics, including amber and agate that were discovered during the repair of Geumsansa Temple's Hall of Maitreya Buddha and Left Attendant Buddhas in June 2008. An ultraviolet analysis, SEM-EDS analysis and FT-IR microscope analysis revealed that the physical and chemical characteristics of the 11 relics are the same as those of amber. It is inferred that the cracks and exfoliation of the surface of most amber relics is attributable to darkening of the color due to C=C bond oxidation. It is also assumed that cracks and exfoliation occurred from the weathered layer on the amber surface. As such, it is appropriate to engage in conservation treatment of the damaged amber relics by using $Paraloid^{(R)}$ B67 reinforcing agent that is diluted in nonpolar solvent. The greatest care is needed for future handling of organic artifacts.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.487-492
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• 2021

In this study, the electrochemical properties of pitch coated silicon sheets/graphite anode materials were investigated. Using NaCl as a template, silicon sheets were prepared through the stöber method and the magnesiothermic reduction methode. In order to synthesize the anode composite, the silicon sheets and graphite were combined with SDBS. The pitch coated silicon sheets/graphite was synthesized using THF as a solvent for the anode material composite. The physical properties of the prepared anode composites were analysed by XRD, SEM, EDS and TGA. The electrochemical performances of the prepared anode composites were performed by the current charge/discharge, rate performance, cyclic voltammetry and EIS tests in the electrolyte LiPF₆ dissolved solvents (EC:DMC:EMC=1:1:1 vol%). As the silicon composition of silicon sheets/graphite composite material increased, the discharge capacity also increased, but the cycle stability tended to decrease. The anode material of pitch coated silicon sheets/graphite composite (silicon sheets:graphite=3:7 weight ratio) showed the initial discharge capacity of 1228.8 mAh/g and the capacity retention ratio of 77% after 50 cycles. From these results, it was found that the cycle stability of pitch coated silicon sheets/graphite was improved.

• Journal of Adhesion and Interface
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• v.24 no.1
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• pp.26-35
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• 2023

Generally, solvent-type coatings generate a large amount of volatile organic chemicals(VOC), which are carcinogenic substances, in the manufacturing process, and their use is regulated due to environmental problems. There is also the problem of resource depletion due to limited fossil fuels. Therefore, in this study, UV-curable urethane acrylate oligomers were synthesized with different contents of isosorbide, which is a biomass material, and proceeded to evaluate the physical properties of coatings. As the isosorbide contents increased, the viscosity, glass transition temperature, tensile strength, stain resistance, and pencil hardness increased, but elongation and flexibility decreased, and BOI-3 showed the best adhesion. The isosorbide content of the oligomer fixed at 20%, UV-curable urethane acrylate oligomer was synthesized according to the content ratio of polycaprolactone diol(PCL) and Ecoprol H1000(Ecoprol). As the PCL/Ecoprol content ratio increased, the glass transition temperature, elongation, and flexibility increased, but the tensile strength and pencil hardness decreased. It was confirmed that the adhesion and stain resistance increased by improving the surface bonding strength of PCL. All films of oligomers synthesized were transparent without discoloration.

• Journal of the Korean Electrochemical Society
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• v.25 no.4
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• pp.174-183
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• 2022

Polymer electrolyte fuel cells and water electrolysis are attracting attention in terms of high energy density and high purity hydrogen production. The catalyst layer for the polymer electrolyte fuel cell and water electrolysis is a porous electrode composed of a precious metal-based electrocatalyst and an ionomer binder. Among them, the ionomer binder plays an important role in the formation of a three-dimensional network for ion conduction in the catalyst layer and the formation of pores for the movement of materials required or generated for the electrode reaction. In terms of the use of commercial perfluorinated ionomers, the content of the ionomer, the physical properties of the ionomer, and the type of the dispersing solvent system greatly determine the performance and durability of the catalyst layer. Until now, many studies have been reported on the method of using an ionomer for the catalyst layer for polymer electrolyte fuel cells. This review summarizes the research results on the use of ionomer binders in the fuel cell aspect reported so far, and aims to provide useful information for the research on the ionomer binder for the catalyst layer, which is one of the key elements of polymer electrolyte water electrolysis to accelerate the hydrogen economy era.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.253-261
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• 2014

In this study, we investigated several chemical and physical characteristics of 4 weed seed fibers; Hemistepta lyrata (HEMLY), Imperata cylindrica var. koenigii (IMPCK), Metaplexis japonica (METJA) and Typha latifolia (TYPLA). In chemical composition, there were 74 (TYPLA)-88.5% (METJA) of holocellulose, 17 (IMPCK)-24% (METJA) of lignin, 0.22 (METJA)-4.2% (IMPCK) of ash, 2.2 (HEMLY)-7.8% (IMPCK) of hot water extractives and 0.4 (IMPCK)-6.3% (TYPLA) of solvent extractives. Alpha-cellulose proportion to holocellulose was similar among weed seed fibers as 45-48%. The crystallinity index (CI) of raw seed fibers was 53.2 (TYPLA)-65.9% (HEMLY). However, CI of the chemical treated fibers (EDA fibers) was a little increased and showed 61.1 (IMPCK)-71.8% (METJA). The maximum thermal decomposition temperature (MTDT) of the raw seed fibers were 312, 321.8, 331.5 and $341.6^{\circ}C$ in METJA, TYPLA, HEMLY and IMPCK, respectively. But the MTDT of the EDA fibers were 327, 327, 341.7 and $360.0^{\circ}C$ in HEMLY, TYPLA, METJA and IMPCK, respectively. Taken together, they showed a similar or better characteristics compared to the reported or commercial natural fiber resourses. Accordingly, they seem to be practically applicable as renewable resources for a new natural fibers.

• Food Science and Preservation
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• v.24 no.8
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• pp.1094-1102
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• 2017

Hazardous metals leaching experiment was carried out in accordance with various usage environments for camping cooking utensils distributed in the market. There was a significant difference in the degree of migration for lead, arsenic, cadmium and nickel defending on the solvent and how to use, although they were all appropriate for criteria. In general, the migrated amount of aluminum was increased in acidic condition, and the migrated amount of arsenic was increased in salty condition. Physical scratches increased the overall release of hazardous metals from the portable pots and pans for camping in all solvents. Especially, in 0.5% citric acid solution, cadmium was migrated by physical scratch in stainless steel and hard aluminum pots and pans. The longer the leaching time, the higher the migration of aluminum in acid condition and arsenic in basic condition. From these results, it is desirable to use the cooking utensil for camping without being exposed to strong acidic or basic solution and scratches in order to reduce the migration of hazardous metals from them.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.5 no.1
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• pp.47-55
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• 1999

Applications of chitosan are related to molecular weight and degree of deacetylation(DOD) of chitosan completely. The molecular weight and DOD were greatly affected by the concentration of solution time and temperature. The degree of demineralization was not significantly different at $50^{\circ}C\;and\;70^{\circ}C$ after 30 minutes. Deproteinization decreased as process time increased. The nitrogen content was reached to 6.92% after 90 minute at $80^{\circ}C$, which is similar to theoretical nitrogen content of chitin. The DOD was 82.84% after 2 hours reaction and increased as the reaction time increased in the process. Viscosity and molecular weight are increased as recycling number of concentrated NaOH solution increased. Chemical, biological and physical properties of chitosan depend on the DOD and molecular size of the molecule. Tensile strength of the films from acetic acid solutions was between $28.9{\sim}33.6$ MPa and was generally higher than that of the films from lactic acid. Elongation of the films from lactic acid was between $97.0{\sim}109.7%$ and was generally higher than that of the films from the acetic acid. Water vapor permeability of the films prepared from lcetic acid solutions was between $1.9{\sim}2.3ng{\cdot}m/m^2{\cdot}s{\cdot}Pa$ and was generally higher than that of the films from the acetic acid.

• Clean Technology
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• v.21 no.1
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• pp.76-82
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• 2015

Volatile organic compounds (VOC) free adhesives have been interested by many scientists and engineers due to environmental regulations and the safety of industrial workers. In this work, a series of composites composed with bisphenol A epoxy resin used as solvent, dicyandiamide, and promoter were prepared to investigate the most appropriate molar ratio for steel-steel adhesion. The cured test specimen of each composite were measured with universal testing machine (UTM) to figure out mechanical properties such as tensile strength, Young’s modulus, and elongation. Furthermore, the lap shear strength of the specimen was tested with UTM while impact resistance was measured with Izod impact tester. The composite whose molar ratio of epoxy resin to curing agent is 1 : 0.9 (sample 3), showed better tensile strength, coefficient of elastic modulus, elongation, and impact strength than other composites did. The highest tanδ from dynamic mechanical analysis (DMA) was observed from sample 2 (epoxy resin: dicy = 1 : 0.7) while sample 3 showed slightly lower tanδ than that of 2. The morphology of the fracture surface of the cured composites from SEM showed that the number of subtle lines on the surface caused by impact increase as the contents of amine curing agent accrete. Furthermore, the viscosity change of sample 5 (epoxy resin: dicy = 1 : 1.3) was observed to confirm its storage stability.

• Korean Journal of Medicinal Crop Science
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• v.11 no.1
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• pp.62-70
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• 2003

The biological activities on human immune and cancer cell lines of the four kinds of Korean mistletoes (Korean Viscum album, var. coloratum, : Korean Viscum sp. in Quercus acutissima Carr., Korean Viscum sp. in Castanea crenata, Korean Viscum sp. in Betula platyphylla, and Korean Viscum sp. in Salix koreensis) extracts were investigated. The extracts were preparated with ethanol, and fractionated with n-butanol, ethyl acetate, chloroform, hexane, and second distilled water. Cytotoxic potencies of the fractions on human normal lung cell line (HEL 299) showed under 28% in the concentration of 0.5 mg/ml. Growth inhibition effect of the Korean mistletoe extracts on the several human cancer cell lines depends on the concentration of the extracts, and extracting solvent. The hexane, chloroform, and ethyl acetate fractions indicated a strong anticancer activity, but not in aqueous and butanol fractions. Some mistletoe fractions have a different characteristic on the cancer cell lines. Stimulation on the growth of human immuno cell lines(B cell : Raji, T cell: Jurkat) of the extracts were confirmed in the ethyl acetate, chloroform, hexane fractions, but not in aqueous system.

• Journal of Food Hygiene and Safety
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• v.37 no.6
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• pp.373-384
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• 2022

Fluoxastrobin a fungicide developed from Strobilurus species mushroom extracts, can be used as an effective pesticide to control fungal diseases. In this study, we optimized the extraction and purification of fluoxastrobin according to its physical and chemical properties using the QuEChERS method and developed an LC-MS/MS-based analysis method. For extraction, we used acetonitrile as the extraction solvent, along with MgSO₄ and PSA. The limit of quantitation of fluoxastrobin was 0.01 mg/kg. We used 0.01, 0.1, and 0.5 mg/kg of five representative agricultural products and treated them with fluoxastrobin. The coefficients of determination (R²) of fluoxastrobin and fluoxastrobin Z isomer were > 0.998. The average recovery rates of fluoxastrobin (n=5) and fluoxastrobin Z isomer were 75.5-100.3% and 75.0-103.9%, respectively. The relative standard deviations (RSDs) were < 5.5% and < 4.3% for fluoxastrobin and fluoxastrobin Z isomer, respectively. We also performed an interlaboratory validation at Gwangju Regional Food and Drug Administration and compared the recovery rates and RSDs obtained for fluoxastrobin and fluoxastrobin Z isomer at the external lab with our results to validate our analysis method. In the external lab, the average recovery rates and RSDs of fluoxastrobin and fluoxastrobin Z isomer at each concentration were 79.5-100.5% and 78.8-104.7% and < 18.1% and < 10.2%, respectively. In all treatment groups, the concentrations were less than those described by the 'Codex Alimentarius Commission' and the 'Standard procedure for preparing test methods for food, etc.'. Therefore, fluoxastrobin is safe for use as a pesticide.