• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.56.1-56.1
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• 2012

The microstructures and mechanical properties of Co-29Cr-6Mo alloy with C and N additions, produced by additive manufacturing using electron beam melting (EBM) method, were studied using X-ray diffraction, electron back scatter diffraction, transmission electron microscope, Vickers hardness tests, and tensile tests, focusing on the influences on the build direction and the various heat treatments after build. It is found that the microstructures for the as built specimens were changed from columnar to equiaxed grain structure with average grain size of approximately $10-20{\mu}m$ due to the heat treatment employing the reverse transformation from a lamellar (hcp + $Cr_2N$) phase to an fcc. Our results will contribute to the development of biomedical Ni-free Co-Cr-Mo-N-C alloys, produced by EBM method, with refined grain size and good mechanical properties, without requiring any hot workings.

• Journal of Microbiology and Biotechnology
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• v.33 no.1
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• pp.75-82
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• 2023

Lactic acid bacteria (LAB) isolated from kimchi (a traditional Korean dish typically made of fermented cabbage) can provide various health benefits, including anti-obesity, antioxidant, antiinflammatory, anticancer, and antimicrobial effects. In this study, we examined the antimicrobial and immunomodulatory effects of Lactiplantibacillus plantarum WiKim0125 cultured in de Man, Rogosa, and Sharpe (MRS) medium containing vegetable waste. Live bacterial cells were eliminated via supernatant filtration or heat treatment. The cell-free supernatant (CFS) obtained from culture broth containing kimchi cabbage waste (KCW), cabbage waste (CW), or onion waste (OW) showed significantly higher antimicrobial activity against skin pathogens (Propionibacterium acnes and Staphylococcus aureus) and foodborne pathogens (Escherichia coli and Salmonella typhimurium), with inhibition zones ranging between 4.4 and 8.5 mm, compared to that in conventional MRS medium (4.0-7.3 mm). In lipopolysaccharide-stimulated RAW264.7 cells, both supernatant and heat-inactivated Lb. plantarum WiKim0125 from culture media containing KCW and CW suppressed the production of inflammatory cytokines (72.8% and 49.6%, respectively) and nitric oxide (62.2% and 66.7%, respectively) without affecting cell viability. These results indicate that vegetable waste can potentially increase the antimicrobial and immunoregulatory potency of LAB while presenting a molecular basis for applying postbiotics to health products.

• Nutrition Research and Practice
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• v.8 no.5
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• pp.526-532
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• 2014

BACKGROUND/OBJECTIVES: Acanthopanax sessiliflorus is a native Korean plant and used as a traditional medicine or an ingredient in many Korean foods. The free radical theory of aging suggests that cellular oxidative stress caused by free radicals is the main cause of aging. Free radicals can be removed by cellular anti-oxidants. MATERIALS/METHODS: Here, we examined the anti-oxidant activity of Acanthopanax sessiliflorus extract both in vitro and in vivo. Survival of nematode C. elegans under stress conditions was also compared between control and Acanthopanax sessiliflorus extract-treated groups. Then, anti-aging effect of Acanthopanax sessiliflorus extract was monitored in C. elegans. RESULTS: Stem extract significantly reduced oxidative DNA damage in lymphocyte, which was not observed by leaves or root extract. Survival of C. elegans under oxidative-stress conditions was significantly enhanced by Acanthopanax sessiliflorus stem extract. In addition, Acanthopanax sessiliflorus stem increased resistance to other environmental stresses, including heat shock and ultraviolet irradiation. Treatment with Acanthopanax sessiliflorus stem extract significantly extended both mean and maximum lifespan in C. elegans. However, fertility was not affected by Acanthopanax sessiliflorus stem. CONCLUSION: Different parts of Acanthopanax sessiliflorus have different bioactivities and stem extract have strong anti-oxidant activity in both rat lymphocytes and C. elegans, and conferred a longevity phenotype without reduced reproduction in C. elegans, which provides conclusive evidence to support the free radical theory of aging.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.680-686
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• 2013

Tungsten oxide films were prepared by an electrochemical deposition method for use as the anode in rechargeable lithium batteries. Continuous potentiostatic deposition of the film led to numerous cracks of the deposits while pulsed deposition significantly suppressed crack generation and film delamination. In particular, a crack-free dense tungsten oxide film with a thickness of ca. 210 nm was successfully created by pulsed deposition. The thickness of tungsten oxide was linearly proportional to deposition time. Compositional and structural analyses revealed that the as-prepared deposit was amorphous tungsten oxide and the heat treatment transformed it into crystalline triclinic tungsten oxide. Both the as-prepared and heat-treated samples reacted reversibly with lithium as the anode for rechargeable lithium batteries. Typical peaks for the conversion processes of tungsten oxides were observed in cyclic voltammograms, and the reversibility of the heat-treated sample exceeded that of the as-prepared one. Consistently, the cycling stability of the heat-treated sample proved to be much better than that of the as-prepared one in a galvanostatic charge/discharge experiment. These results demonstrate the feasibility of using electrolytic tungsten oxide films as the anode in rechargeable lithium batteries. However, further works are still needed to make a dense film with higher thickness and improved cycling stability for its practical use.

• Journal of the East Asian Society of Dietary Life
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• v.23 no.2
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• pp.257-263
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• 2013

The free radical scavenging activities of extracts from kimchi, as well as various antioxidant activities, such as 2,2-azinobis-( 3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, and ferric reducing antioxidant power (FRAP) were examined. Specifically, the ABTS radical scavenging and FRAP activities of ethanolic extracts from kimchi (kimchi with non-treated salt fermented anchovy, treated non-heat salt fermented anchovy, treated heat salt fermented anchovy and commercial salt-fermented anchovy) were $0.749{\pm}0.26$, $0.895{\pm}0.15$, $0.758{\pm}0.12$, and $0.769{\pm}0.02$ mM Trolox eq./mg extract and $0.727{\pm}0.11$, $0.901{\pm}0.03$, $0.811{\pm}0.17$, and $0.843{\pm}0.16$ mM $FeSO_4$ eq./mg extract, respectively. In addition, the antioxidant activity of extract from kimchi was estimated in vivo. Mice were randomly divided into six groups (n=6), and treated with LPS for 10 days, which resulted in lower antioxidant capacities as well as increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) values in the blood serum. Furthermore, antioxidant enzymes (catalase and superoxide dismutase) in blood serum increased in the presence of the kimchi. The present results reveal antioxidant activities from kimchi and encourage their application for the food industry and cooking.

• Korean Journal of Food Science and Technology
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• v.28 no.5
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• pp.928-934
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• 1996

Rice bran, treated with heat or ${\gamma}-radiation$, was stored at $-15^{\circ}C,\;4^{\circ}C,\;37^{\circ}C$ and room temperature to determine its lipid stability by monitoring the changes in moisture, free fatty acids (FFA) and peroxide value (POV). Initial moisture content of rice bran was 14% and decreased with time. The higher storage temperature, the more moisture loss. The moisture content became 9% after 80 days of storage at $37^{\circ}C$. The initial FFA of rice bran was 2.5% which increased with time except the samples stored at $-15^{\circ}C$. The higher storage temperature, the more FFA was produced, by 9 times the initial FAA after 80 days of storage at $37^{\circ}C$. POV increased about twice the initial value after 80 days of storage at $-15^{\circ}C,\;4^{\circ}C$, and room temperature, and 5 times at $37^{\circ}C$. Rice bran was treated with heat at $70^{\circ}C,\;90^{\circ}C\;or\;105^{\circ}C$ and stored for 2 weeks at $30^{\circ}C$: The higher the heat treatment temperature and the longer the heat treatment time, the more moisture was lost. The not show any significant changes. Irradiation at $1{\sim}30\;kGy$ and subsequent storage for 4 weeks at $5^{\circ}C\;or\;30^{\circ}C$ caused negligible changes in moisture content. The FFA contents of rice bran irradiated up to 10 kGy were almost similar to these of nonirradiated one when measured just after irradiation. The samples irradiated at 30 kGy were 1.5 times higher in the FFA contents than nonirradiated ones. But there was little influence of irradiation doses on the FFA contents during storage. Irradiation caused the increase in POV of rice bran. resulting in 4 times increase in case of 30 kGy irradiated sample. During the storage, however, the POV of irradiated rice bran decreased significantly.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.235-243
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• 2002

Ni-base superalloys are used extensively in industry, both in aeroengines and land based turbines. About 60% by weight of most modern gas turbine engine structural components are made of Ni-base superalloys. To satisfy practical demands, the efficiency of gas turbine engines has been steadily and systematically increased by design modifications to handle higher turbine inlet or firing temperatures. However, the increase in operating temperatures has lead to a decrease in the life of components and increase in costs of replacement. Moreover, around 80% of the large frame size industrial/utility gas turbines operating in the world today were installed in the mid-sixties to early seventies and are now 25 to 30 years old. Consequently, there are greater opportunities now to repair and refurbish the older models. Basically, there are two major factors influencing the weldability of the cast alloys: strain-age cracking and liquation cracking. Susceptibility to strain-age cracking is due to the total Ti plus AI content of the alloy; Liquation cracking is due either to the presence of low melting constituents or constitutional liquation of constituents. Though Rene 41 superalloy has 4.5wt.% total Ti and Al content and falls just below the safe limit proposed by Prager et al., controlled grain size and special heat treatments are needed to obtain crack-free welds. Varying heat treatments and filler materials were used in a laboratory study, then the actual welding of service parts was carried out to verity the possibility of crack-tree weld of components fabricated from Rene 41 superalloy. The microstructural observations indicated that there were two kinds of carbides in the FCC matrix. MC carbides were located along the grain boundaries, while M$_{23}$C$_{6}$ carbide was located both inter and intra granularly. Two kinds of filler materials, Rene 41 and Hastelloy X were used to gas tungsten arc weld a patch into the sheet metal, along with varying pre-weld heat treatments. The microstructure, hardness and tensile tests were determined. The service distressed parts were categorized into three classes: with large cracks, with medium cracks and with small or no visible cracks. No significant difference in microstructure among the specimens was observed. Specimens were cut from the corner and the straight edge of the patch repair, away from the corner. The only cracks present were found to be associated with inadequate surface preparation to remove oxidation. Guidelines for oxide removal and the welding procedures developed in the research enabled crack-free welds to be produced.d.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.146-149
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• 2001

The functionalized dendrimer containing 48 azobenzene was synthesized. Many isolated featureless domains were explicitly observed even at the air/water interface. Also, these monolayers were representatively observed, showing the change of surface pressure with irradiation time and wavelength. In AFM images, larger domains irregularly shaped structures on the top, while smaller ones were free from such defects. In the optical absorption spectra of the monolayer films by UV irradiation and heat treatment, only the photoiosmerization of the G4-48 Azo monolayers was observed, revealing a decrease of absorbance peaks without any change of the spectral shape. This suggests that the functional group and the symmetric chain affect optical behavior and morphological change.

• Electrical & Electronic Materials
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• v.7 no.6
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• pp.481-489
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• 1994

The $SnO_2$/(n)Si solar cell was fabricated by electron beam evaporation method, and their properties were investigated. In proportion to increase of substrate and annealing temperature, the conductivity of $SnO_2$ thin film was increased, but its optical transmission decreases because of increasing optical absorption of free electrons in the thin film. $SnO_2$/Si Solar cell characteristics were improved by annealing, but the solar cells was deteriorated by heat treatment above 500[.deg. C]. The optimal outputs of $SnO_2$/Si solar cell through above investigations were $V_{\var}$:350[mV], $J_{sc}$ ;16.53[mA/c $m^{2}$], FF;0.41, .eta.=4.74[%]

• Journal of the Korean Ceramic Society
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• v.29 no.11
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• pp.870-876
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• 1992

Lead lanthanum zirconate titanate (PLZT, 6/65/35) powders, crack-free and dense thin films have been prepared by polymeric sol-gel process. Pyrolysis of the gel, crystallization and optical transmittance behavior of the PLZT thin film onto sapphire substrate have been studied. Esterification occurs during synthesis of PLZT complexation. Crystalline Pb phase was transiently formed near 450$^{\circ}C$. Content of perovskite phase in the films were increased with increasing thickness of film, but the kinetics of formation of perovskite phase in films was slower than that of powders. Transmittance of the films was decreased with increasing the temperature of heat treatment. Ferroelectric hysteresis loop measurements indicated increments of remanent polarization and coercive field for plenty more of perovskite phase.