• Journal of IKEEE
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• v.22 no.4
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• pp.1226-1229
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• 2018

We investigated the improvement of surface roughness and states after high temperature annealing using reduced-graphene oxide (r-GO) capping layer on ion-implanted 4H-SiC epitaxial layer. The specification of the 4H-SiC wafer grown on n-type $4^{\circ}$ off-axis 4H-SiC was $10{\mu}m$-thick and n-type epitaxial layer with a dose of $1.73{\times}10^{15}cm^{-2}$. The $n^+$ region were formed by multiple nitrogen ion-implantations and r-GO capping layer was produced by spray coating method. AFM measurements revealed that RMS value of the sample capped with r-GO was tenfold decrease compared to the sample without r-GO capping. The improvement of surface states was also verified by the improvement of leakage current level.

• Journal of Ginseng Research
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• v.43 no.4
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• pp.580-588
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• 2019

Background: Ginsenoside Rg1 has been shown to clear senescence-associated beta-galactosidase (SA-${\beta}$-gal) in cultured cells. It remains unknown whether Rg1 can influence SA-${\beta}$-gal in exercising human skeletal muscle. Methods: To examine SA-${\beta}$-gal change, 12 young men (age $21{\pm}0.2years$) were enrolled in a randomized double-blind placebo controlled crossover study, under two occasions: placebo (PLA) and Rg1 (5 mg) supplementations 1 h prior to a high-intensity cycling (70% $VO_{2max}$). Muscle samples were collected by multiple biopsies before and after cycling exercise (0 h and 3 h). To avoid potential effect of muscle biopsy on performance assessment, cycling time to exhaustion test (80% $VO_{2max}$) was conducted on another 12 participants (age $23{\pm}0.5years$) with the same experimental design. Results: No changes of SA-${\beta}$-gal were observed after cycling in the PLA trial. On the contrary, nine of the 12 participants showed complete elimination of SA-${\beta}$-gal in exercised muscle after cycling in the Rg1 trial (p < 0.05). Increases in apoptotic DNA fragmentation (PLA: +87% vs. Rg1: +133%, p < 0.05) and $CD68^+$ (PLA:+78% vs. Rg1:+121%, p = 0.17) occurred immediately after cycling in both trials. During the 3-h recovery, reverses in apoptotic nuclei content (PLA:+5% vs. Rg1 -32%, p < 0.01) and increases in inducible nitrate oxide synthase and interleukin 6 mRNA levels of exercised muscle were observed only in the Rg1 trial (p < 0.01). Conclusion: Rg1 supplementation effectively eliminates senescent cells in exercising human skeletal muscle and improves high-intensity endurance performance.

• Journal of the Korean Applied Science and Technology
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• v.39 no.1
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• pp.34-41
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• 2022

As the use of chemical products increases in daily life, the removal of dye waste has also emerged as an important environmental issue. This dye waste can be decomposed using a photocatalyst, and the photocatalyst can be synthesized very cost-effectively by using the sol-gel technology. The sol-gel technology is not only very useful for nanoscale film formation, but also can simply form multilayer structures. Using a multiple spin coating method, in this study, a ZnO film with a multilayered structure (3 layers, 5 layers) was formed by using zinc oxide (ZnO), which is effective in decomposing various dyes. For performance comparison, a ZnO film having a single layer structure by a single spin coating method was prepared as a control. Structural and elemental analysis of ZnO film was performed using an X-ray diffraction analyzer and an energy dispersive X-ray spectrometer. A nanowire-like surface morphology could be observed through a scanning electron microscope. Additionally, UV-Vis spectrophotometer was used to measure the absorbance of UV light. The ZnO film with a five-layer structure degraded the simulated methylene blue by 49% more than the ZnO film with a single-layer structure. In conclusion, it was found that ZnO having a multilayered structure is useful as a photocatalyst that decomposes methylene blue dye more effectively.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.312-312
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• 2022

Peanut hull as by-product has been discarded during peanut processing. However, peanut hull contains plenty of polyphenols that shows various physiological activities. The objectives of this study were to investigate anti-inflammatory and enzyme inhibitory activities of polyphenols from 'Sinpalkwang' peanut (Arachis hypogaea L.) hull. Compounds were isolated from methanol extracts of peanut hull by preparative-high performance liquid chromatography after identifying and quantifying polyphenols using Ultra performance liquid chromatography (UPLC) and UPLC-Quadrupole time-of-flight-mass spectrometry profiling. The structures of compounds were elucidated by one-dimensional [¹H, ¹³C] nuclear magnetic resonance (NMR) and two-dimensional NMR (correlated spectroscopy, heteronuclear single quantum coherence and heteronuclear multiple bond correlation). Three compounds were identified as 5,7-dihydroxy-4H-chromen-4-one (peak 2), luteolin (peak 4) and eriodictyol (peak 5). Significant differences in inflammatory mediator such as nitric oxide (NO), interleukin-6 (IL-6) and interleukin-1β (IL-lβ) in lipopolysaccharide stimulated Raw 264.7 macrophages and in enzyme (xanthine oxidase [XO] and α-glucosidase [AG]) inhibitory activities were observed between three compounds (p < 0.05). Peak 5 treated Raw 264.7 macrophages showed lower content of NO (16.4 uM), IL-6 (7.0 ng/mL), and IL-1β (60.6 pg/mL) than peak 2 (NO: 28.3 uM, IL-6: 11.3 ng/mL, IL-1β: 66.9 pg/mL) and peak 4 (NO: 24.7 uM, IL-6: 9.3 ng/mL, IL-1β: 62.6 pg/mL). Peak 5 showed higher XO inhibitory activity (84.7%) and higher AG inhibitory activity (52.4%) than peak 2 (XO inhibitory activity: 45.4%, AG inhibitory activity: 21.6%) and peak 4 (XO inhibitory activity: 37.9%, AG inhibitory activity: 37.5%) at concentration of 0.5mg/mL. This study suggests that peanut hull could be a potential source of anti-inflammatory and physiological materials while creating new use of discarded peanut hull as by-products concomitantly.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.19-23
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• 2023

The Second-generation high-temperature superconducting (HTS) Rare-Earth Barium Copper Oxide (REBCO) wire is a composite laminate having a multi-layer structure (8 or more layers). HTS wires will undergo multiple loads including the bending-tension loads during winding, high current density, and high magnetic fields. In particular, the wires are subjected to bending stress and magnetic field stress because HTS wires are wound around a circular bobbin when making a high-field magnetic. Each of the different laminated wires inevitably exhibits damage and fracture behavior of wire due to stress deformation, mismatches in thermal, physical, electrical, and magnetic properties. Therefore, when manufacturing high-field magnets and other applications, it is necessary to calculate the stress-strain experienced by high-temperature superconducting wire to present stable operating conditions in the product's use environment. In this study, the finite element model (FEM) was used to simulate the strain-stress characteristics of the HTS wire under high current density and magnetic field, and bending loads. In addition, the result of obtaining the neutral axis of the wire and the simulation result was compared with the theoretical calculation value and reviewed. As a result of the simulation using COMSOL Multiphysics, when a current of 100 A was applied to the wire, the current value showed the difference of 10^-9. The stress received by the wire was 501.9 MPa, which showed a theoretically calculated value of 500 MPa and difference of 0.38% between simulation and theoretical method. In addition, the displacement resulted is 30.0012 ㎛, which is very similar to the theoretically calculated value of 30 ㎛. Later, the amount of bending stress by the circular mandrel was received for each layer and the difference with the theoretically obtained the neutral axis result was compared and reviewed. This result will be used as basic data for manufacturing high-field magnets because it can be expanded and analyzed even in the case of wire with magnetic flux pinning.

• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.537-549
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• 1998

The purpose of this study was to evaluate the influence of root resection and retrograde cavity preparation methods on the apical leakage in endodontic surgery. To investigate the effect of various root resection and retrograde cavity preparation methods on the apical leakage, 71 roots of extracted human maxillary anterior teeth and 44 mesiobuccal roots of extracted human maxillary first molars were used. Root canals of the all the specimens were prepared with step-back technique and filled with gutta-percha by lateral condensation method. Three millimeters of each root was resected at a 45 degree angle or perpendicular to the long axis of the tooth according to the groups. Retrograde cavities were prepared with ultrasonic instruments or a slow-speed round bur, and occlusal access cavities were filled with zinc oxide eugenol cement. Three coats of clear nail polish were placed on the lateral and coronal surfaces of the specimens except the apical cut one millimeter. All the specimens were immerged in 2% methylene blue solution for 7 days in an incubator at $37^{\circ}C$. The teeth were dissolved in 14 ml of 35% nitric acid solution and the dye present within the root canal system was returned to solution. The leakage of dye was quantitatively measured via spectrophotometric method. The obtained data were analysed statistically using two-way ANOVA and Duncans Multiple Range Test. The results were as follows: 1. No statistically significant difference was observed between ultrasonic retrograde cavity preparation method and slow-speed round bur technique, without apical bevel (p>0.05). 2. Ultrasonic retrograde preparation method showed significantly less apical leakage than slow-speed round bur technique, with bevel (p<0.0001). 3. No statistically significant difference was found between beveled resected root surface and non-beveled resected root surface, with ultrasonic technique (p>0.05). 4. Non-beveled resected root surface showed significantly less apical leakage than beveled resected root surface, with slow-speed round bur technique (p<0.0001). 5. No statistically significant difference in apical leakage was found between the group of retrograde cavity prepared parallel to the long axis of the tooth and the group of one prepared perpendicular to the long axis of the tooth (p>0.05). 6. Regarding isthmus preparation, ultrasonic retrograde preparation method showed significantly less apical leakage than slow-speed round bur technique, in the mesiobuccal root of maxillary molar, without bevel (p<0.0001).

• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.257-274
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• 2018

The purpose of this study was to evaluate the effect of acid-treatment conditions on the surface properties of the RBM (Resorbable Blast Media) treated titanium. Disk typed cp-titanium specimens were prepared and RBM treatments was performed with calcium phosphate ceramic powder. Acid solution was mixed using HCl, $H_2SO_4$ and deionized water with 4 different volume fraction. The RBM treated titanium was acid treated with different acid solutions at 3 different temperatures and for 3 different periods. After acid-treatments, samples were cleaned with 1 % Solujet solution for 30 min and deionized water for 30 min using ultrasonic cleanser, then dried in the electrical oven ($37^{\circ}C$). Weight of samples before and after acid-treatment were measured using electric balance. Surface roughness was estimated using a confocal laser scanning microscopy, crystal phase in the surface of sample was analyzed using X-ray diffractometer. Surface morphology and components were evaluated using Scanning Electron Microscope (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoemission Spectroscopy (XPS). Values of the weight changes and surface roughness were statistically analyzed using Tukey-multiple comparison test (p=0.05). Weight change after acid treatments were significantly increased with increasing the concentration of $H_2SO_4$ and temperature of acid-solution. Acid-treatment conditions (concentration of $H_2SO_4$, temperature and time) did not produce consistent effects on the surface roughness, it showed the scattered results. From XRD analysis, formation of titanium hydrides in the titanium surface were observed in all specimens treated with acid-solutions. From XPS analysis, thin titanium oxide layer in the acid-treated specimens could be evaluated. Acid solution with $90^{\circ}C$ showed the strong effect on the titanium surface, it should be treated with caution to avoid the over-etching process.

• Journal of Periodontal and Implant Science
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• v.25 no.3
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• pp.741-755
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• 1995

Currently titanium is the material of choice for implants because of its biological acceptance. This high degree of biocompatibility is thought to result, in part, from the protective and stable oxide layer that presumably aids in the bonding of the extracellular matrix at the implant-tissue interface. Endosseous dental implants are interfaced with bone, connective tissue, and epithelium when implanted into the jaw bone. The soft tissue interface including connective tissue and epithelium is one of the most critical factors in the determination of implant maintenance and prognosis. For maintenance of failing or failed implants, it is essential to treat the implant fixture surface to remove bacterial endotoxins and make a surface tolerated by surrounding soft and hard tissues. In this study, the effect of mechanical treatment on titanium plasma sprayed implant on adhesiveness and proliferation of human gingival fibroblasts and changed surface characteristics were studied. titanium plasma sprayed discs manufactured by Friedrichsfeld company were treated with loaw speed stone bur, a rubber point and a jetpolisher. Its surface components were analyzed with Energy dispersive X-ray spectroscopy to evaluate whether the surface characteristics were altered or not. To observe the spreading pattern of the human gingival fibroblasts which attached to the all specimens author used the scanning electron microscope. The results were as follows : Pure titanium and plasma sprayed titanium, stone polished titanium showed titanium peak and small amout of aluminum, so there was no alteration on surface characteristics. Under the scanning electron microscopic examination in the initial attachment of human gingival fibroblast, there was a slight enhancement in pure titanium, stone polished titanium than plasma sprayed titanium. After 6 hours, the pure titanium and stone polished titanium showed human gingival fibroblasts were elongated and connected with numerous processes. Human gingival fibroblasts were more intimately attached on the pure titanium discs than on the other discs. The human gingival fibroblasts attached on the plasma sprayed titanium by thin and elongated processes. After 24 hours, the human gingival fibroblasts connected with each other via numerous processes and compeletly covered the pure titanium and stone polshed titanium discs. Human gingival fibroblasts had multiple point contacts with more long and thin lamellopodia and showed a little bare surface on plasma sprayed titanium discs.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.1
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• pp.73-79
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• 2011

Purpose: The aim of this study was to evaluate the effect of repeated firings on the color of zirconia restoration with different shading method. Materials and methods: Three different types of zirconia frameworks (adding metallic pigments to the initial zirconia powder before sintering (Group NM), dipping the milled frameworks in dissolved coloring agents (Group KI), or application of liner material to the sintered white frameworks (Group KW) were used to support A3 shade dentin porcelain. Repeated firings (3, 5, or 7) were performed, color differences among ceramic specimens were measured using a colorimeter. Repeated measurements analysis of variance (ANOVA) was used to analyze the data for significant difference. The Tukey Honestly Significant Different (HSD) test was used to perform multiple comparisons (${\alpha}$ = .05). Results: 1. $L^*a^*b^*$ values of the ceramic systems were affected by the number of firings (1, 3, 5 or 7 firings) (P < .001) and shading methods (P < .001). 2. As the number of firings increased, the $L^*$ (for all groups) and $a^*$ value (for KW and NM groups) decreased and the $b^*$ value(for all groups) increased. 3. The mean color differences caused by repeated firings were perceptible (${\Delta}E$ > 1) for group KW and KI fired after 3 times, except for group NM fired after 7 times. 4. In order of decreasing ${\Delta}E$ value fired after 7 times, the values were group KI(${\Delta}E$ = 2.26) > group KW (${\Delta}E$ = 1.47) > group NM (${\Delta}E$ = 1.08) (P < .001). Conclusion: Repeated firings influenced the color of the zirconium-oxide all-ceramic specimens with different shading methods.

• Restorative Dentistry and Endodontics
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• v.36 no.5
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• pp.419-424
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• 2011

Objectives: This study was aimed to determine the effects of temporary sealing materials on microtensile bond strength between resin-coated dentin and resin inlay and to compare the bonding effectiveness of delayed dentin sealing and that of immediate dentin sealing. Materials and Methods: The teeth were divided into 4 groups: group 1, specimens were prepared using delayed dentin sealing after temporary sealing with zinc oxide eugenol (ZOE); group 2, specimens were prepared using immediate dentin sealing and ZOE sealing; group 3, specimens were prepared using immediate dentin sealing and Dycal (Dentsply) sealing; group 4, specimens were prepared using immediately sealed, and then temporarily sealed with a resin-based temporary sealing material. After removing the temporary sealing material, we applied resin adhesive and light-cured. Then the resin inlays were applied and bonded to the cavity with a resin-based cement. The microtensile bond strength of the sectioned specimens were measured with a micro-tensile tester (Bisco Inc.). Significance between the specimen groups were tested by means of one-way ANOVA and multiple Duncan's test. Results: Group 1 showed the lowest bond strength, and group 4 showed the highest bond strength (p < 0.01). When temporary sealing was performed with ZOE, immediate dentin sealing showed a higher bonding strength than delayed dentin sealing (p < 0.01). Conclusions: Based on these results, immediate dentin sealing is more recommended than delayed dentin sealing in bonding a resin inlay to dentin. Also, resin-based temporary sealing materials have shown the best result.