• Food Science and Preservation
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• v.15 no.1
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• pp.111-117
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• 2008

As part of studies on functional food development from the acorn (Quercus acutissima CARRUTHERS), this study investigated the antioxidant properties of the acorn using response surface methodology. Optimal extraction conditions were established by monitoring total phenol levels, electron donating ability, antioxidant ability and nitrite-scavenging action using response surface analysis under a central composite design. The extraction temperature varied in the $30-70^{\circ}C$, the extraction time between 1-5 h, and the solvent ratio was in the interval 5-25mL/g of sample. Extracted total phenols were highest at $57.91^{\circ}C$, 4.08 h, and 22.39 mL/g. This extraction was influenced by solvent ratio, but not by extraction time or temperature. Electron donating ability was found to be highest at $60.37^{\circ}C$, 2.85h, and 6.47 mL/g. The highest antioxidant level was 2.09 AI at $37.11^{\circ}C$, 1.67 h, and 18.84 mL/g, and this value was greatly influenced by all of extraction temperature, extraction time, and solvent ratio. Nitrite-scavenging ability was found to be highest at $47.07^{\circ}C$, 1.24h, and 19.55mL/g. Changes in nitrite-scavenging ability were most influenced by solvent ratio, followed by extraction temperature, but no influence of extraction time within the range tested was found.

• Journal of the Korean Society of Food Culture
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• v.19 no.1
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• pp.94-105
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• 2004

The biochemical components of Namcheondlggae, Miryangdlkkae 25, Boradlggae and Ipdlkkae 1 were measured. The samples were extracted with hot water, 60% acetone or 80% ethanol for screening physiological activity. The crude protein content (4.36%) was found in the Miryangdlkkae 25 and calcium content (497.5 mg%) was found in the Namcheondlggae among the tested 4 perilla loaves. Fructose was 30.86 mg% in the Namcheondlggae and free amino acids at all perilla leaves was detected seventeen. In Boradlggae, glutamic acid and alanine were 25.37 and 11.91 mg%. Totally nine non-volatile organic acids were also detected and the contents of malic acid and glutaric acid were 28.34 and 14.57 mg% in Boradlggae. The Miryangdlkkae 25 had the highest vitamin C amount which was 113.24 mg%. Angiotensin converting enzyme (ACE) inhibition activity of 60% acetone extract of Miryangdlkkae 25 was 39.20% when added as addition of 200 ppm level and xanthine oxidase inhibition activity of 80% ethanol extract of Boradlggae was 46.71%. Electron denoting activity of 60% acetone extract from Namcheohndlggae was the strongest inhibition activity as 98.19% when 200 ppm level of the sample extracts were added.

• Journal of the Korean institute of surface engineering
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• v.52 no.6
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• pp.283-288
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• 2019

MCrAlY overaly coatings are used as oxidation barrier coatings to prevent degradation of the underlying substrate in high temperature and oxidizing environment of the hot section of gas turbines. Therefore, oxidation resistance in high temperature is important property of MCrAlY coatings. Also, coefficients of thermal expansion (CTE) of MCrAlY have middle value of that of Ni-based superalloys and oxides, which have the effect of preventing the delamination of the surface oxides. Cyclic oxidation test is one of the most useful methods for evaluating the high temperature durability of coatings used in gas turbines. In this study, NiCoCrAlY overlay coatings were formed on Inconel 792(IN 792) substrates by vacuum plasma spraying process. Vacuum plasma sprayed NiCoCrAlY coatings and IN 792 susbstrates were exposed to 1000℃ one-hour cyclic oxidation environment. NiCoCrAlY coatings showed lower weight gain in short-term oxidation. In long-term oxidation, IN 792 substrates showed higher weight loss due to delamination of surface oxide but NiCoCrAlY coatings showed lower weight loss. X-ray diffraction (XRD) analysis showed α-Al2O3 and NiCr₂O₄ was formed during the cyclic oxidation test. Through cross-section observation using scanning electron microscopy (SEM) and electron back scatter diffraction (EBSD) analysis, thermally grown oxide (TGO) layer composed of α-Al₂O₃ and NiCr₂O₄ was formed and the thickness of TGO increased during 1000℃ cyclic oxidation test. β phase in upper side of NiCoCrAlY coating was depleted due to oxidation of Al and outer beta depletion zone thickness also increased as the cyclic oxidation time increased.

• Korean Journal of Food Science and Technology
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• v.34 no.3
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• pp.524-528
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• 2002

The study was carried out to evaluate the antioxidant activity of grape seed extracts by measuring acid value, peroxide value (POV), thiobarbituric acid reactive substances (TBARS value) and electron donating ability by 1,1-dipheny1-2-pycryl hydrazil (DPPH) method. Total phenol content of freeze dried crude solvent extracts increased in the order of ethanol>acetone>hot water. Among extracts, the total phenol content of 70% ethanol extract of grape seed (GSE) was the highest, 51%. Besides the total phenol, the other major components of GSE were crude carbohydrate (29.63%), crude protein (3.38%) and crude lipid (2.84%). The acid values of crude rice bran oil containing GSE or several antioxidants at the concetration of 0.01% were 52.3 for the control, 0.5 for GSE, 2.3 for dibutyl hydroxytoluene (BHT), 45.0 for tertiarybutyl hydroxy quinone (TBHQ), 29.9 for tocopherol and 37.7 for ascorbic acid. The POVs for linoleic acid methyl ester in the presence of 0.01% antioxidants were 1220 meq/kg in control, 55 meq/kg in GSE, 104 meq/kg in BHT, 952 meq/kg in tocopherol and 71 meq/kg in GSE, 37% in BHT, 37% in tocopherol and 52% in ascorbic acid. The electron donating abilities by DPPH in the presence of 0.01% antioxidants were 95.3% in GSE, 75.0% in BHT, 96.3% in tocopherol and 98.2% in ascorbic acid. These results indicated that the antioxidants activities of GSE were significantly higher than those of several antioxidants compared.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.48 no.4
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• pp.357-364
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• 2022

In this study, antioxidant efficacy was analyzed to verify the value of use as an antioxidant-related functional cosmetic material using Cheongtaejeon tea extract. Cheongtaejeon tea was extracted, concentrated, and freeze-dried with hot water and 70% ethanol as a solvent to prepare samples, and then ABTS⁺ radical scavenging activity, electron donating ability, SOD-like ability, reducing power, ferric reducing antioxidant power (FRAP), total phenolic, and flavonoid contents were analyzed. In the ABTS⁺ radical scavenging activity experiment, both the Cheongtaejeon hydrothermal extract (CTW) and the Cheongtaejeon 70% ethanol extract (CTE) showed erasure activity of more than 98% at a concentration of 1,000 ㎍/mL, and in the electron donating analysis experiment, CTW and CTE, respectively, 42.20% and 78.82%. As a result of SOD-like activity measurement, activity of 39.73% and 67.39% of CTW and CTE, respectively, was confirmed. In the case of FRAP and reducing power experiments, both CTW and CTE showed high effects, and as a result of analyzing the total phenol and flavonoid contents, both CTW and CTE showed high contents. Based on the results of the experiment, the Cheongtaejeon tea extract is expected to have a highly valuable as a functional cosmetics material related to antioxidants.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1997-2002
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• 2010

ZnSe and ZnS:Mn nanocrystals were synthesized via the thermal decomposition of their corresponding organometallic precursors in a hot coordinating solvent (TOP/TOPO) mixture. The organic surface capping agents were substituted with EDTA molecules to impart hydrophilic surface properties to the resulting nanocrystals. The optical properties of the water-dispersible nanocrystals were analyzed by UV-visible and room temperature solution photoluminescence (PL) spectroscopy. The powders were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), and confocal laser scanning microscopy (CLSM). The solution PL spectra revealed emission peaks at 390 (ZnSe-EDTA) and 597 (ZnS:Mn-EDTA) nm with PL efficiencies of 4.0 (former) and 2.4% (latter), respectively. Two-photon spectra were obtained by fixing the excitation light source wavelengths at 616 nm (ZnSe-EDTA) and 560 nm (ZnS:Mn-EDTA). The emission peaks appeared at the same positions to that of the PL spectra but with lower peak intensity. In addition, the morphology and sizes of the nanocrystals were estimated from the corresponding HR-TEM images. The measured average particle sizes were 5.4 nm (ZnSe-EDTA) with a standard deviation of 1.2 nm, and 4.7 nm (ZnS:Mn-EDTA) with a standard deviation of 0.8 nm, respectively.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.6
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• pp.269-274
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• 2018

Grain-oriented electrical steel sheets are mainly used as core materials for transformers and motors. They should have excellent magnetic properties such as low core loss, high magnetic flux density and high permeability. In order to improve the magnetic properties of the electrical steel sheet, it is important to form Goss oriented grains with a very strong {110}<001> orientation. Recently, efforts have been made to develop Goss grains by controlling processes such as hot rolling, cold rolling, and primary and secondary recrystallization. In this study, the sheets containing 3.2 and 3.4wt.% Si were used, which were rolled with 1 and 10 passes with total thickness reduction of 89%. Heating was carried out for primary recrystallization with different heating rates of $25^{\circ}C/s$ and $24^{\circ}C/min$ until $720^{\circ}C$. The behavior of Goss-, {411}<148>-, and {111}<112>-oriented grains were analyzed using X-ray diffraction(XRD) and electron back-scatter diffraction(EBSD) analysis. The area fraction of Goss-oriented grains increased with the number of rolling passes during cold rolling; however, after the primary recrystallization, the area fraction of the Goss grains was higher and exact Goss grains were found in the specimens subjected to rapid heating after one rolling pass.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.89.1-89.1
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• 2013

We present a multiwavelength study of the X-class flare, which occurred in active region (AR) NOAA 11339 on 3 November 2011. The EUV images recorded by SDO/AIA show the activation of a remote filament (located north of the AR) with footpoint brightenings about 50 min prior to the flare occurrence. The kinked filament rises-up slowly and after reaching a projected height of ~49 Mm, it bends and falls freely near the AR, where the X-class flare was triggered. Dynamic radio spectrum from the Green Bank Solar Radio Burst Spectrometer (GBSRBS) shows simultaneous detection of both positive and negative drifting pulsating structures (DPSs) in the decimetric radio frequencies (500-1200 MHz) during the impulsive phase of the flare. The global negative DPSs in solar flares are generally interpreted as a signature of electron acceleration related to the upward moving plasmoids in the solar corona. The EUV images from AIA $94{\AA}$ reveal the ejection of multiple plasmoids, which move simultaneously upward and downward in the corona during the magnetic reconnection. The estimated speeds of the upward and downward moving plasmoids are ~152-362 and ~83-254 km/s, respectively. These observations strongly support the recent numerical simulations of the formation and interaction of multiple plasmoids due to tearing of the current-sheet structure. On the basis of our analysis, we suggest that the simultaneous detection of both the negative and positive DPSs is most likely generated by the interaction/coalescence of the multiple plasmoids moving upward and downward along the current-sheet structure during the magnetic reconnection process. Moreover, the differential emission measure (DEM) analysis of the active region reveals presence of a hot flux-rope structure (visible in AIA 131 and $94{\AA}$) prior to the flare initiation and ejection of the multi-temperature plasmoids during the flare impulsive phase.

• Polymer(Korea)
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• v.29 no.2
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• pp.166-171
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• 2005

EPDM (ethylene propylene diene monomer)/silicone rubber blends were prepared and the influence of a compatibilizer and thermal aging on the properties of the blends was investigated. The blends of which the compositions were varied in the range of 90/10 through $10/90\;wt\%$ were melt mixed by using a Brabender Plasticoder (internal mixer) and were vulcanized by a hot press. The morphology of the vulcanized EPDM/SR blends was examined by scanning electron microscopy (SEM). After the thermal Aging for 24, 48, 96 hrs at $100^{\circ}C$ in an air oven, hardness, tensile strength, elongation and contact angle of the blends were investigated. From the result of the morphology, it was confirmed that the domain size of the blends containing the compatibilizer was reduced. As the increase of the thermal aging time, hardness and tensile strength of the blends decreased but elongation and contact angle increased.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.66-71
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• 2011

The flexural strength of $MoSi_2$ based composites reinforced with Nb sheets has been investigated, based on the detailed examination of their microstructure and fractured surface. Both sintered density and porosity of Nb/$MoSi_2$ composites were also examined. Nb/$MoSi_2$ composites were fabricated by different conditions such as temperature, applied pressure and its holding time, using a hot-press device. The volume fraction of Nb sheet in this composite system was fixed as 10%. The characterization of Nb/$MoSi_2$ composites were investigated by means of optical microscopy, scanning electron microscope and three point bending test. Nb/$MoSi_2$ composites represented a dense morphology at the interfacial region, accompanying the creation of two types of reaction layer by the chemical reaction of Nb and $MoSi_2$. Nb/$MoSi_2$ composites possessed an excellent density at the fabricating temperature of $1350^{\circ}C$, corresponded to about 95% of theoretical density. The flexural strength of Nb/$MoSi_2$ romposites were greatly affected by the pressure holding time at the same fabricating temperature, owing to the large suppression of porosity in the microstructure. Especially, Nb/$MoSi_2$ composites represented a good flexural strength of about 310 MPa at the fabricating condition of $1350^{\circ}C$, 30MPa and 60min, accompanying the pseudo-ductile fracture behavior by the deformation of Nb sheet and the interfacial delamination.