• Journal of Surface Science and Engineering
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• v.53 no.6
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• pp.351-359
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• 2020

Formation behavior and properties of PEO (Plasma Electrolytic Oxidation) film on AA2024 were investigated under application of pulsed current as a function of Na3PO4 concentration in 0.05 M Na2SiO3 solution by analyzing voltage-time behavior, in-situ observation of arc generation, observation of surface morphology and measurements of thickness and surface roughness. Arc generation voltage decreased with increasing Na3PO4 concentration. Color difference of PEO films between edge and inner part disappeared by addition of Na3PO4. It was also observed that size of nodules on PEO film decreased with increasing Na3PO4 concentration. Thickness of PEO films formed on AA2024 increased with increasing Na3PO4 concentration. Whereas, surface roughness of PEO films decreased with increasing Na3PO4 concentration up to 0.05 M of Na3PO4 which is attributed to the deceased size of nodules on the PEO films. However, the surface roughness increased with increasing Na3PO4 concentration more than 0.07 M of Na3PO4 which seems to be due to the formation of non-uniform PEO films with smooth surface and large size pores formed by orange-colored big arcs. The experimental results suggest that added sodium phosphate less than 0.2 M in an alkaline silicate solution can contribute to the formation of relatively thick and uniform thickness of PEO films under arc generation voltage lower than 300 V.

• Journal of Surface Science and Engineering
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• v.48 no.6
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• pp.260-268
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• 2015

The thermal barrier coating (TBC) for inner wall of liquid-fuel rocket combustor consists of NiCrAlY as bonding layer and $ZrO_2$ as a top layer. In most case, the plasma spray coating is used for TBC process and this process has inherent possibility of cracking due to large difference in thermal expansion coefficients among bonding layer, top layer and metal substrate. In this paper, we suggest crack-free TBC process by using a precise electrodeposition technique. Electrodeposited Ni-P/Cr double layer has similar thermal expansion coefficient to the Cu alloy substrate resulting in superior thermal barrier performance and high temperature oxidation resistance. We studied the effects of phosphorous concentrations (2.12 wt%, 6.97 wt%, and 10.53 wt%) on the annealing behavior ($750^{\circ}C$) of Ni-P samples and Cr double layered electrodeposits. Annealing temperature was simulated by combustion test condition. Also, we conducted SEM/EDS and XRD analysis for Ni-P/Cr samples. The results showed that the band layers between Ni-P and Cr are Ni and Cr, and has no formed with heat treatment. These band layers were solid solution of Cr and Ni which is formed by interdiffusion of both alloy elements. In addition, the P was not found in it. The thickness of band layer was increased with increasing annealing time. We expected that the band layer can improve the adhesion between Cr and Ni-P.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.22 no.3
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• pp.313-324
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• 2024

Se sorption onto Ca-type montmorillonite purified from Bentonil-WRK-a new research bentonite introduced by Korea Atomic Energy Research Institute-was examined under ambient conditions (pH 4-9, pe 7-9, I = 0.01 M CaCl₂, and T = 25℃). Se(IV) was identified as the oxidation state responsible for weak sorption (Kd < 22 L·kg^-1) by forming surface complexes with edge functional groups of the montmorillonite. Thermodynamic modeling, considering reaction mechanisms of outer-sphere complexation (≡AlOH⁺₂ + HSeO₃^- ⇌ ≡AlOH₃SeO₃, log K = 0.50 ± 0.21), inner-sphere complexation (2≡AlOH + H₂SeO₃(aq) ⇌ (≡Al)₂SeO₃ + 2H₂O(l), log K = 7.89 ± 0.51), and Ca²⁺-involved ternary complexation (≡AlOH + Ca²⁺ + SeO₃^2- ⇌ ≡AlOHCaSeO₃, log K = 7.69 ± 0.28) between selenite and aluminol sites of montmorillonite, acceptably reproduced the batch sorption data. Outer- and inner-sphere complexes are predominant Se(IV) forms sorbed in acidic (pH ≈ 4) and near-acidic (pH ≈ 6) regions, respectively, whereas ternary complexation accounts for Se(IV) sorption at neutral pHs under the ambient conditions. The experimental and modeling data generally extend a material-specific sorption database of Bentonil-WRK, which is essential for assessing its radionuclide retention performance as a buffer candidate of deep geological disposal system for high-level radioactive waste.

• The Korea Journal of Herbology
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• v.23 no.2
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• pp.179-192
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• 2008

Objectives : Draconis Resina (DR) has been used as a traditional Korean herbal medicine since ancient times, and today it is used as a medication for wounds, tumors, diarrhea, rheumatism, in the itching of insect bites and with other conditions in the folk medicine. The aim of this study was to determine whether fractionated extracts of DR inhibit free radical generation, intracellular oxidation, production of nitrite, an index of NO, PGE2, iNOS, COX-2 and proinflammatory cytokines in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages, Methods : DR extract prepared with methanol, and then fractionated with hexane, dichloromethane, ethylacetate, n-butanol and water. Inhibitory effect of DR onto free radical generation was determined by measuring DPPH, superoxide anions and nitric oxide scavenging activities in vitro. Cytotoxic activity of extracts on RAW 264.7 cells was measured using 5-(3-caroboxymeth-oxyphenyl)-2H-tetra-zolium inner salt (MTS) assay. Intracelluar oxidation was analysed by DCF-DA assay. The nitric oxide (NO) production was measured by Griess reagent system. The levels of iNOS and COX-2 expression were confirmed by western blot. And proinflammatory cytokines were measured by ELISA kit. Results : Our results indicated that fractionated extracts, especially dichloromethane and ethyl acetate extracts, significantly inhibited free radical generation, the LPS-induced H202, NO, PGE2 production and iNOS, COX-2 expression accompanied by an attenuation of TNF-${\alpha}$, IL-$1{\beta}$ and IL-6 formation in macrophages. Conclusions : Our results indicate that dichloromethane and ethyl acetate extracts of DR have potential as an agent of chronic inflammatory diseases.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.8
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• pp.411-419
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• 2016

The objective of this study was to evaluate the application possibility of tube type electrolysis module system using recirculation process through removal organic matters and nitrogen in the pigment wastewater. The tube type electrolysis module consisted of a inner rod anode and an outer tube cathode. Material used for anode was titanium electroplated with $RuO_2$. Stainless steel was used for cathode. It was observed that the pollutant removal efficiency was increased according to the decrease of flowrate and increase of current density. When the retention time in tube type electrolysis module system was 180 min, chlorate concentration was 382.4~519.6 mg/L. The chlorate production was one of the major factors in electrochemical oxidation of tube type electrolysis module system using recirculation process used in this research. The pollutant removal efficiencies from the bench scale tube type electrolysis module system using recirculation operated under the electric charge of $4,500C/dm^2$ showed the $COD_{Mn}$ 89.6%, $COD_{Cr}$ 67.8%, T-N 96.8%, and Color 74.2%, respectively and energy consumption was $5.18kWh/m^3$.

• Membrane Journal
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• v.22 no.3
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• pp.171-177
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• 2012

Effect of humic acid (HA), photo-oxidation and adsorption with periodic $N_2$ back-flushing was investigated in hybrid process of ceramic ultrafiltration and photocatalyst for drinking water treatment. It was compared and investigated with the previous result at water back-flushing in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). As decreasing HA, $R_f$ decreased dramatically and J increased, and finally $V_T$ was the highest at HA 2 mg/L. As HA concentration increased from 2 to 10 mg/L, the membrane fouling resistance after 180 mins' operation ($R_{f,180}$) improved 0.8 times more than that of water back-flushing. Therefore, HA concentration should affect on the membrane fouling at $N_2$ back-flushing than water back-flushing. Turbidity treatment efficiencies were almost constant independent of HA concentration, but HA treatment efficiency was the maximum at HA 2 mg/L. This means that adsorption and photo-oxidation of photocatalyst beads could removed HA at HA 2 mg/L, but it was not enough at 4 mg/L. Beyond HA 6 mg/L, UF could effectively treat HA by thick cake layer on membrane surface and severe inner membrane fouling.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.55-62
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• 2001

With a spread of BGA, CSP and fine pitch devices, the need of flatter surface finish in bare board is becoming more critical in solderability. The electroless Ni/Au plating has a solution of these needs and also has being spread to apply to surface finish for bare board in many electronic goods. But, the electroless Ni/Au plating had several issues such as Ni oxidation and phosphorous contents. Before this study, we studied on the effect of BGA solderability in electroless Ni/Au plating and chose some major factors such as the oxidation property of NiP plating and warpage of board. Firstly, we made test board with various plating conditions and improved the plating property through the improvement of NiP oxidation reducing P content. Also, we minimized the warpage of board with the improvement of inner layer structure and the analysis of warpage. For the evaluation of solderability, we analyzed the warpage of board and the plating property after mounting BGA on the board with optimizing conditions. The solder joint of BGA is investigated by SEM(Scanning Electronic Microscope) and OM(Optical Microscope). The composition of joint is used by EDS(Energy Dispersive Spectroscopy). We analyzed the fracture strength and mode by ball shear teser.

• The Korea Journal of Herbology
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• v.24 no.3
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• pp.39-50
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• 2009

Objectives : Smilacis glabrae rhizoma (SG) has been traditionally used as a herbal medication of musculoskeletal disorders like arthritis, pain, convulsions, and syphilis in traditional Korean medicine. This study was investigated anti-oxidative and anti-inflammatory effect of fractionated extracts of Smilacis Glabrae Rhizoma in Human Umbilical Vein Endothelial Cell (HUVEC). Methods : SG extract prepared with methanol, and then fractionated with hexane, dichloromethane, ethylacetate, n-butanol and water. Inhibitory effect of SG onto free radical generation was determined by measuring DPPH, superoxide anions and nitric oxide scavenging activities in vitro. Cytotoxic activity of extracts on RAW 264.7 cells was measured using 5-(3-caroboxymethoxyphenyl)-2H-tetra-zolium inner salt (MTS) assay. Intracelluar oxidation was analysed by DCF-DA assay. The nitric oxide (NO) production was measured by Griess reagent system. The levels of ICAM-1 and VCAM-1 expression were confirmed by western blot. And proinflammatory cytokines were measured by ELISA kit. Results : Our results indicated that fractionated extracts, especially ethyl acetate (EA) extract, significantly inhibited free radical generation, the TNF-$\alpha$-induced intracellular oxidation. Furthermore, the EA extract protected TNF-$\alpha$-induced adhesion to THP-1, expression of adhesion molecules accompanied by an attenuation of IL-6 and IL-8 formation in HUVEC. Conclusions : These results indicate that EA extract of SG have potential as an agent of atherosclerosis and other chronic inflammatory diseases including diabetes, hypertension, and arthritis.

• Journal of the Korean Society of Food Culture
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• v.20 no.6
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• pp.703-708
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• 2005

This study was carried out to compare the antioxidant activities of the ether, butanol, water extracts from chestnut inner shell(Castanea crenata Sieb. et Zucc.) with those of tocopherol and BHA in soybean oil. All additives were added to soybean oil on the quantities of 0.02%. Comparing the antioxidant activities under autooxidation condition at $45.0{\pm}0.5$ for 42days of the extracts were recorded in the order of butanol>ether>control>BHA>tocopherol depending on the solvent. Under the condition at $60.0{\pm}0.5^{\circ}C$ for 32days, the butanol extracts represented the high antioxidation effect, however, there was no significant differences between the ether extracts and control. Under thermal oxidation condition, the ether extract showed stronger antioxidant activity than those of the butanol extract. In the results of polyphenol compound analysis, ellagic acid, quercetin, morin, naringenin, flavanol were included in the ether extracts and ellagic acid, naringenin, gallic acid, flavanol were included in the butanol extracts, respectively. Among them, ellagic acid in ether extract and gallic acid and naringenin in butanol extracts seed to increase the antioxidant activities in the substrate oil.

• Corrosion Science and Technology
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• v.15 no.3
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• pp.125-128
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• 2016

The ASTM T92 steel was corroded at $600^{\circ}C$ and $800^{\circ}C$ at 1 atm of $N_2/3.1%H_2O/2.42%H_2S-mixed$ gas. The formed scales were thick and fragile. They consisted primarily of the outer FeS scale and the inner (FeS, $FeCr_2S_4$)-mixed scale containing a small amount of the $Cr_2O_3$ scale. This indicated that corrosion occurred mainly via sulfidation rather than oxidation due to the $H_2S$ gas. Since FeS was present throughout the whole scale, T92 steel was non-protective, displaying high corrosion rates.