• Corrosion Science and Technology
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• v.19 no.3
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• pp.138-145
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• 2020

Immersion tests of Alloy 600 were conducted in simulated primary water environments of a pressurized water reactor at 325 ℃ for 10, 100, and 1000 h to obtain insight into effects of surface deformation on internal and intergranular (IG) oxidation behavior through precise characterization using various microscopic equipment. Oxidized samples after immersion tests were covered with polyhedral and filamentous oxides. It was found that oxides were abundant in mechanically ground (MG) samples the most. The number density of surface oxides increased with time irrespective of the method of surface finish. IG oxidation occurred in mechanically polished (MP) and chemically polished (CP) samples with thin internal oxidation layers. However, IG oxidation was suppressed with relatively thick internal oxidation layers in MG samples compared to MP and CP samples, suggesting that MG treatment could increase resistance to primary water stress corrosion cracking (PWSCC) from the standpoint of IG oxidation. As a result, appropriate surface treatment for Alloy 600 could prevent oxygen diffusion into grain boundaries, inhibit IG oxidation, and finally induce its high PWSCC resistance.

• Journal of Korea Foundry Society
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• v.27 no.2
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• pp.72-76
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• 2007

Contact materials are widely used as electrical parts. Ag-Cd alloy has a good wear resistance and stable contact resistance. But the Cd exists as coarse oxide in alloy so it have an effect on mechanical properties badly. Moreover, the Cd is an injury material to environment. Nowadays, the use of Cd is strictly restricted. Because of these disadvantage, Ag-Sn-In alloy has been developed. In Ag-Sn-In alloy, the Sn : In ratio affects the internal oxidation properties, such as the formation of the oxide layer on the surface. In this work, we changed and optimized the Sn : In ratio variety for good internal oxidation properties. We have shown that a internal oxidation process did not fully completed when the Sn : In ratio is over 4 : 1 because of the Sn oxide layer at surface. The increase of In decelerates the formation of Sn oxide layer.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.2
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• pp.34-41
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• 2011

Wrought nickel-base superalloys are being considered as the structural materials in very-high temperature gas-cooled reactors. To understand the effects of impurities, especially oxygen, in helium coolant on the mechanical properties of Alloy 617, creep tests were performed in high temperature flowing He environments with varying $O_2$ contents at 800, 900, and $1000^{\circ}C$. Also, creep life in static He was measured to simulate the pseudo-inert environment. Creep life was the longest in static He, while the shortest in flowing helium. In static He, impurities like $O_2$ and moisture were quickly consumed by oxidation in the early stage of creep test, which prevented further oxidation during creep test. Without oxidation, microstructural change detrimental to creep such as decarburization and internal oxidation were prevented, which resulted in longer creep life. On the other hand, in flowing He environment, surface oxides were not stable enough to act as diffusion barriers for oxidation. Therefore, extensive decarburization and internal oxidation under tensile load contributed to premature failure resulting in short creep life. Limited test in flowing He+200ppm $O_2$ resulted in even shorter creep life. The oxidation samples showed extensive spallation which resulted in severe decarburization and internal oxidation in those environments. Further test and analysis are underway to clarify the relationship between oxidation and creep resistance.

• The Journal of Internal Korean Medicine
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• v.24 no.2
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• pp.203-212
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• 2003

Objective : As a link in chain of research to confirm the oriental medical prescription which has the anti-atherosclerosis effects, this research evaluated the effects on the macrophage-related factors by using KanghwalSokdantang(KS). Methods : In order to perform this research, we have evaluated the effects on the oxLDL formation from the macrophages, the nitric oxide formation, and the oxidation of macrophages. Thus, with this evaluation, we have investigated the applicapability on the artherosclerosis. Results : KanghwalSokdantang has showed a noticeable reduction of protein oxidation in the process of oxLDL formation, has remarkably restrained phospholipid peroxidation, an index to estimated the phospholipid oxidation and reduction that are formed in the process of macrophage's oxLDL formation, and has increased the nitrite concentration noticeably in the LDL-dealing macrophages. By increasing the survival rate of macrophages, KanghwalSokdantang has restrained the cellular damages. KanghwalSokdantang is ineffective on the LDH outflow from damaged cells. $1{\mu}g/ml$ KanghwalSokdantang sample has increased acid phosphatase activity remarkably. Conclusion : KanghwalSokdantang has the possibility to be used in the prevention and treatment of atherosclerosis, which is formed by the oxLDL formation of macrophages.

• Journal of Korea Foundry Society
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• v.25 no.6
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• pp.226-232
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• 2005

Contact material is widely used in the field of electrical parts. Ag-CdO material has a good wear resistance and stable contact resistance. In order to establish optimizing heat treatment condition, rolling temperature and oxidation process, we studied the microstructure of Ag-CdO material with various conditions. The experimental procedure were melting using high frequency induction, heat treatment, rolling and internal oxidation. And we experimented on difference process, Post-oxidaion. In this study, we obtained the optimizing heat treatment condition was $700^{\circ}C$ for 15 min. and the optimizing rolling temperature was $730^{\circ}C$. In investigation of the microstructure of oxidized material, coarse oxide and depleted oxidation layer existed. The hardness was average Hv 70. When we used Post-oxidation, oxides were finer than prior process and depleted oxidation layer did not exist. The hardness of Post-oxidation material was average Hv 80. And the optimizing rolling temperature was $800^{\circ}C$.

• Corrosion Science and Technology
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• v.21 no.1
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• pp.53-61
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• 2022

Alloys of Fe-(5.3-29.8)%Mn-(1.1-1.9)%Al-(0.4-0.5)%C were oxidized at 550 ℃ to 650 ℃ for 20 h to understand effects of alloying elements on oxidation. Their oxidation resistance increased with increasing Mn level to a small extent. Their oxidation kinetics changed from parabolic to linear when Mn content was decreased and temperature was increasing. Oxide scales primarily consisted of Fe₂O₃, Mn₂O₃, and MnFe₂O₄ without any protective Al-bearing oxides. During oxidation, Fe, Mn, and a lesser amount of Al diffused outward, while oxygen diffused inward to form internal oxides. Both oxide scales and internal oxides consisted of Fe, Mn, and a small amount of Al. The oxidation of Mn and carbon transformed γ-matrix to α-matrix in the subscale. The oxidation led to the formation of relatively thick oxide scales due to inherently inferior oxidation resistance of alloys and the formation of voids and cracks due to evaporation of manganese, decarburization, and outward diffusion of cations across oxides.

• The Journal of Internal Korean Medicine
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• v.38 no.3
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• pp.367-375
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• 2017

Objective: To investigate the effect of Artemisiae Iwayomogii Herba, Curcumae Radix, and Aurantii Fructus Immaturus complex extract (ACA) on dyslipidemia-related factor expression and anti-oxidation in HepG2 cells. Method: After treatment with ACA in the HepG2 cells, DPPH, ABTS radical scavenging activity, ROS production, and glutathione (GSH) production were measured. The free fatty acid, lipid peroxidation (MDA), ACAT1, and HMG-CoA reductase mRNA expression were measured in the HepG2 cells after treatment with ACA. Results: 1. DPPH, ABTS radical scavenging activity increased in an ACA concentration-dependent manner. 2. ACA significantly decreased ROS production in comparison to the control group. 3. ACA significantly increased glutathione production. 4. ACA significantly decreased free fatty acid and lipid peroxidation (MDA) in the HepG2 cells. 5. ACA decreased the mRNA expression of ACAT1 and HMG-CoA reductase. Conclusion: These results suggest that Artemisiae Iwayomogii Herba, Curcumae Radix, and Aurantii Fructus Immaturus complex extract (ACA) inhibits dyslipidemia-related factor expression and that it is effective in anti-oxidation. A future in vivo experiment with ACA is needed to investigate the effect on anti-dyslipidemia. It is expected that ACA is effective in anti-dyslipidemia and applied to cardiovascular disease, ischemic heart disease, stroke, etc.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.4
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• pp.53-60
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• 1991

This study has been performed to investigate into the internal oxidation characteristics of low carbon steel with respect to the added amount of air in nitrogen-propane atmosphere after gas carburizing for various times at $930^{\circ}C$. The results obtained from the experiment are as follows ; (1) Optical micrographs have shown that the internal oxidation is unlikely to occur in the gas atmosphere without air and that oxidized zone in the outer surface layer is formed in the gas atmosphere with air revealing that the depth of oxidized zone increases with increasing the added amount of air. (2) The formation of internally oxidized zone in the outer surface layer has been found to be inhibited as Ni content increases, i. e, the amount of alloying element increases. (3) The depth of oxidation has been measured to increase with almost parabolically gas carburizing time of up to 6 hours.

• The Journal of Internal Korean Medicine
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• v.40 no.3
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• pp.425-442
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• 2019

Objectives: This study aimed to reveal the pharmacological properties of the newly prescribed herbal mixture, Chenmadansamgamibokhap-tang(CDBT), against hypoxia-induced neuronal cell injury (especially mouse hippocampal neuronal cell line, HT-22 cells) and their corresponding mechanisms. Methods: A cell-based in vitro experiment, in which a hypoxia condition induced neuronal cell death, was performed. Various concentrations of the CDBT were pre-treated to the HT-22 cells for 4 h before 18 h in the hypoxia chamber. The glial cell BV-2 cells were stimulated with $IFN{\gamma}$ and LSP to produce inflammatory cytokines and reactive oxygen species. When the neuronal HT-22 cells were treated with this culture solution, the drug efficacy against neuronal cell death was examined. Results: CDBT showed cytotoxicity in the normal condition of HT-22 cells at a dose of $125{\mu}g/mL$ and showed a protective effect against hypoxia-induced neuronal cell death at a dose of $31.3{\mu}g/mL$. CDBT prevented hypoxia-induced neuronal cell death in a dose-dependent manner in the HT-22 cells by regulating $HIF1{\alpha}$ and cell death signaling. CDBT prevented neuronal cell death signals and DNA fragmentation due to the hypoxia condition. CDBT significantly reduced cellular oxidation, cell death signals, and caspase-3 activities due to microglial cell activations. Moreover, CDBT significantly ameliorated LPS-induced BV-2 cell activation and evoked cellular oxidation through the recovery of redox homeostasis. Conclusions: CDBT cam be considered as a vital therapeutic agent against neuronal cell deaths. Further studies are required to reveal the other functions of CDBT in vivo or in the clinical field.

• The Korea Journal of Herbology
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• v.23 no.2
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• pp.123-136
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• 2008

Objectives : To estimate the value of the Gyungokgo as therapeutic agent preventing against aging with an analysis of the ingredients and the bio-activating effects by enzymologic methods. Methods : A quantitative analysis of general ingredients' of the Gyungokgo's extract was done first. The effects on electronic donating ability, SOD-like activity, nitric oxide inhibition, xanthine oxidase inhibition, whitening effect have been investigated in the physiological activity measurement of function experiment. Results : The contained hydrolyzed amino acid is Valine, Aspartic acid, Arginine, Isoleucine and the contained free amino acid is Arginine, Phenylalanine, Valine, Glycine. The derivative of free amino acid is Phosphoserine, Carnocine, ${\gammer}$-Aminoisobutyric acid. And the Gyungokgo contains 14 species of minerals, K>Na>Ca>Mg>Fe>Al>Mn. Then, to assure of the Gyungokgo's anti-oxidation, these following subjects -polyphenol, electronic donating ability, SOD-like activity, nitric oxide inhibition, xanthine oxidase inhibition, tyrosinase inhibation- are analyzed and show high activity especially the most in chloroform extracts, (every ingredients written by the order of high amount) Conclusions : The Gyungokgo contains many materials functioning as anti-oxidation, neurotransmitter, anti-fatigue and immune agent.