• Journal of the Korean Wood Science and Technology
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• v.30 no.1
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• pp.11-17
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• 2002

This study was performed to determine the characteristics of particleboard made from three-months-old bamboo, (Phyllostachys nigra var henonis Stapf) grown in Damyang district, Korea. Total 60 particleboards were manufactured with 1% of liquid wax emulsion using urea-formaldehyde resin content 9%,11% and 13%, respectively. The particle boards consisted of three layers, in which face layer had the same proportion of a weight 25% of the particleboard each. And the core layer had a weight 50% of the board. The core layer and face layer had the particle dimension passing 6 mesh (3.35 mm), 12 mesh (1.70 mm), respectively. The study was carried out to determine the effect of the growing time of 3 months and 3 years on particleboard properties. The physical and mechanical properties of boards were measured and compared to the Korean standard (KS) requirements of particle boards. The results were as follows; 1. The longer the growing time, the higher the density of bamboo. Density of the upper part of bamboo showed higher than that of lower part. 2. Density and moisture content of the two particle boards did not show significant differences. Three-months-old bamboo particleboard gave higher thickness swelling than three-years-old bamboo particleboard. Bamboo particleboard passed the thickness swelling test of KS. 3. The static bending and internal bond strength of three-months-old bamboo particleboard were higher than those of three-years-old bamboo. Increase of resin contents in bamboo particleboard increased bending and internal bond strength, proportionally. Strength properties of bamboo particle board were above KS. 4. Formaldehyde emission of all the bamboo particleboards satisfied E₂ level (5.0 mg/L) of KS F 3104.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.105-111
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• 2024

The SLA (Stereolithography Apparatus) method is a type of 3D printing technique predicated on the transformation of liquid photocurable resin into a solid form through UV laser exposure, and its application is increasing in various fields. In this study, we conducted research to enhance the hydrophobicity and transparency of SLA 3D printing surfaces for microfluidic system production. The enhancement of surface hydrophobicity in SLA outputs was attainable through the application of hydrophobic coating methods, but the coating durability under different conditions varied depending on the type of hydrophobic coating. Additionally, to simultaneously achieve the required transparency and hydrophobic properties for the fabrication of microfluidic systems, we applied hydrophobic coatings to the proposed transparency enhancement method from prior research and compared the changes in contact angles. Teflon coating was proposed as a suitable hydrophobic coating method for the fabrication of microfluidic systems, given its excellent transparency and high coating durability in various environmental conditions, in comparison to titanium dioxide coating. Finally, we produced an Electrophoresis of Charged Droplet (ECD) chip, one of the digital microfluidics systems, using SLA 3D printing with the proposed Teflon coating method (Fluoropel 800). Droplet manipulation was successfully demonstrated with the fabricated chip, confirming the potential application of SLA 3D printing technology in the production of microfluidic systems.

• Analytical Science and Technology
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• v.11 no.5
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• pp.374-385
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• 1998

Phytoestrogens are biologically active compounds derived from plants foods. It had been suggested that phytoestrogens, by inhibiting aromatase in peripheral and/or cancer cells and lowering estrogen levels, may play a protective role as antipromotional compounds during growth of estrogen-dependent cancers. Therefore, simultaneous analysis of estrogens and phytoestrogens is necessary to elucidate the possible involvement of phytoestrogens in estrogen metabolism. In this view, we developed a simple and reproducible procedure to quantitatively determine estrogen and phytoestrogen metabolites. The proposed method consisted of solid phase extraction using preconditioned Serdolit AD-2 resin, enzyme hydrolysis with ${\beta}$-glucuronidase/arylsulfatase from Helix pomatia, liquid-liquid extraction and TMS-ether derivatization. And the final determination was carried out by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring mode (SIM). The precision and accuracy of this method was evaluated through within-a-day and day-to-day test. Recovery range and detection limit were 71.96~105.66%, 2~4 ng/mL, respectively. Using this method, 17 estrogen and 5 phytoestrogen compositions in urine of normal subjects were analyzed. It was found that amounts and relative distribution of urinary phytoestrigens and estrogens showed different pattern in male and female subjects.

• The Korean Journal of Food And Nutrition
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• v.16 no.4
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• pp.296-302
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• 2003

First. the purification and analysis of alliin in garlic from different origins by alliin-HPLC determination method were studied. Allinase in garlic was inactivated by heating in boiling water followed by extraction of alliin in garlic with 80% methanol. To remove free amino acids and alliin homologs in garlic, garlic extract was separated by cation exchange column which was packed with amberlite CG-120 resin using 40L d-water as eluent. Alliin in garlic extract was crystallized in a mixture of acetone (50$^{\circ}C$)：H$_2$O：acetic acid=70:29:1 and then recrystallized in a mixture of acetone (50$^{\circ}C$)：H$_2$O：acetic acid=75:24:1. Obtained alliin was identified by melting point. TLC, microscope observation and mass spectrometry. High performance liquid chromatography (HPLC) following pre-column derivatization of cystein derivatives with o-phthaldialdehyde/2-mercaptoethanol has succeessfully been applied to the analysis of various garlics. Each alliic of standard solution and garlic extract was derivatized to isoindole derivative by o-phthaldialdehyde /2-mercaptoethanol and then analyzed by HPLC. Six point calibration was done by using alliin peak area. Lineality was observed at 0 ∼ 1.0mg/ml of alliin concentration. Weighted regression line function was Y=6254X - 256077. By this function, alliin contents in various garlics were 0.34 ∼ 0.73% fresh weight. Second study was designed to evaluate the effects of garlic extracts of various concentrations on the growth of various pathogenes (Eubacterium limonsum, Bacteroides fragilis, Salmonella typhimurium, Salmonella typhi, Shigella sonnei, Kiebsiella pneumoniae, Enterobacter cloacae, Pserdomonas aeruginosa, Escherichia coli). For antimicrobial effects against microorganism, totally minimal inhibition concentrations (MIC) of alliin were from 5,000 to 20,000ppm. MIC of ethanol extract were 1,250 to 10,000ppm.

• Korean Journal of Food Science and Technology
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• v.32 no.5
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• pp.1029-1034
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• 2000

A suitable method of sample treatments to minimize the analytical interferences was presented in order to determine bisphenols [bisphenol F (BPF), bisphenol A (BPA), bisphenol F diglycidyl ether (BFDGE), and bisphenol A diglycidyl ether (BADGE)] in various canned beverages coated with epoxy resin by the reversephase high performance liquid chromatography (RP-HPLC) equipped with a fluorescence detector and the gas chromatography with mass selective detection. The recovery test of bisphenols was performed using 1, 5, and 10 ${\mu}g/L$ bisphenols spiked beverages with the combined technique of the solid-phase extraction (SPE) and the liquid-phase extraction (LPE). Both BPA and BADGE showed quite adequate resolutions in HPLC-chromatograms. The recoveries of BPA obtained by LPE with diethyl ether were higher than those obtaind with methylene chloride on coffee, shikhye and fruit juice. For cola and tea, the recoveries of BPA obtaind by SPE were higher than those by LPE with diethyl ether. The recoveries of BADGE were less than those of BPA for all beverage samples treated by either SPE or LPE method. In survey of bisphenols for eighteen commercial canned beverage samples, BPA contents of coffee, cola, tea, shikhye, and fruit juice were in the range of $1.3{\sim}11.6,\;0.5{\sim}0.9,\;1.0{\sim}1.3,\;2.4{\sim}7.9$, and $3.0{\sim}3.4\;{\mu}g/L$, respectively, but there was no detection of BPA in beer sample.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.3
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• pp.338-351
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• 2005

Statement of problem. Accurate fit between the implant components is important because the misfit of the implant components results in frequent screw loosening, irreversible screw fracture, plaque accumulation, poor soft tissue reaction, and destruction of osseointegration. Purpose. This study is to evaluate the machining accuracy and consistency of the implant fixture/ abutment/screw interfaces of the internal connection system by using a Stereoscopic Zoom microscope and FE-SEM(field emission scanning electron microscope) Materials and methods. The implant systems selected in this study were internal connection type implants from AVANA(Osstem^{\circledR}), Bioplant(Cowell-Medi^{\circledR}), Dio(DIO^{\circledR}), Neoplant(Neobiotech 􀋓), Implantium(Dentium􀋓)systems. Each group was acquired 2 fixtures at random. Two piece type abutment and one piece type abutment for use with each implant system were acquired. Screw were respectively used to hold a two piece type abutment to a implant fixture. The implant fixtures were perpendiculary mounted in acrylic resin block. Each two piece abutment was secured to the implant fixture by screw and one piece abutment also secured to the implant fixture. Abutment/fixture assembly were mounted in liquid unsaturated polyester. All samples were cross-sectioned with grinder-polisher unit. Finally all specimens were analysed the fit between implant fixture/abutment/screw interfaces Results and conclusions. 1. Implant fixture/abutment/screw connection interfaces of internal connection systems made in Korea were in good condition. 2. The results of the above study showed that materials and mechanical properties and quality of milling differed depending on their manufacturing companies.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.4
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• pp.297-308
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• 2007

The granulation equipment of concentrated wastes is manufactured for the polymer solidification of concentrated wastes. It uses liquid sodium silicate as a granulating agent for the granulating of dried powder containing boric acid. The granulating agent is sprayed in the form of droplet and mean size of dried granules is $2{\sim}4mm$. The new technology which has been used for the polymer solidification of spent resin in U.S. and certified by Nuclear Regulatory Commission (NRC) is successfully applied to concentrated wastes. This uses in-situ solidification process within drum without mechanical mixing. Maximum loading of waste can be achieved without increasing of waste volume. Polymer waste forms were evaluated with several test such as fire test, compressive strength test, leaching test, immersion test, irradiation test, and thermal cycling test according to standard test procedures.

• Korean Journal of Food Science and Technology
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• v.42 no.3
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• pp.277-280
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• 2010

Bisphenol A (BPA) is an endocrine disruptor frequently used in food containers, including epoxy resin and polycarbonates. BPA concentrations were monitored by high performance liquid chromatography (HPLC) under photosensitization of riboflavin (RF), methylene blue (MB), rose bengal (RB), or titanium dioxide ($TiO_2$) and the involvement of singlet oxygen was determined using sodium azide ($NaN_3$). The stability of BPA decreased significantly in the order of RF, RB, and MB photosensitization (p<0.05), while the concentration of BPA in samples with $TiO_2$ was not significantly different from that of control samples without photosensitizers under light (p>0.05). The stability of BPA decreased in an MB concentration-dependent manner and increased as the concentration of added $NaN_3$ increased, implying that singlet oxygen was involved in the photodegradation of BPA during MB photosensitization. The results of this study may help control the BPA content in foods or the environments using photosensitized oxidation and visible light irradiation.

• Transactions of Materials Processing
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• v.22 no.1
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• pp.23-29
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• 2013

In this study, a micro/nano-random-pattern-structure surface was machined by electric discharge machining (EDM) followed by replicating the EDM surface with a silicone elastomer having low energy and greater hydrophobicity. The variation of hydrophobicity was of prime interest and was examined as a function of the surface roughness of the replicated silicone elastomer. The hydrophobicity was evaluated by the water contact angle (WCA) measured on the relevant surface. For the experiments, the original surfaces were machined by die sinking electric discharge machining (DS-EDM) and wire cutting electric discharge machining (WC-EDM). The ranges of surface roughness were Ra $0.8{\sim}19{\mu}m$ for the DS-EDM and Ra $0.5{\sim}4.7{\mu}m$ for the WC-EDM. In order to fabricate a hydrophobic surface, the EDM surfaces were directly replicated using a liquid-state silicone elastomer, which was thermally cured. The measured WCA on the replicated surfaces for DS-EDM was in the range of $115{\sim}130^{\circ}$ and for WC-EDM the WCA was in the range of $123{\sim}150^{\circ}$. Additionally, the dynamic hydrophobicity was evaluated by measuring an advancing and a receding WCA on the replicated silicone elastomer surfaces.

• Polymer(Korea)
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• v.24 no.4
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• pp.499-504
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• 2000

The effect of anodic oxidation on high strength PAN-based carbon fibers has been studied in terms of surface functionality and surface energetics of the fiber surfaces, resulting in improving the mechanical properties of composites. According to FT-IR and XPS measurements, it reveals that the oxygen functional groups on fiber surfaces induced by an anodic oxidation largely influence the surface energetics of fibers or the mechanical interfacial properties of composites, such as the interlaminar shear strength (ILSS) of composites. According to the contact angle measurements based on the wicking rate of a test liquid, it is observed that anodic oxidation does lead to an increase in surface free energy of the carbon fibers, mainly due to the increase of its specific (or polar) component. From the surface energetic point of view, it is found that good wetting plays an important role in improving the degree of adhesion at interfaces between fiber and epoxy resin matrix of the resulting composites. Also, a direct linear relationship is shown between 01s/01s ratio and ILSS or between specific component and ILSS of the composites for this system.