• Composites Research
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• v.15 no.6
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• pp.16-23
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• 2002

In this work, the effect of anodic oxidation on surface characteristics of high strength PAN-based carbon fibers was investigated in mechanical interfacial properties of composites. The surface properties of the carbon fibers were determined by acid-base values, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angles. And their mechanical interfacial properties of the composites were studied in interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$). As a result, the acidity or the $O_{ls}/C_{ls}$ ratio of carbon fiber surfaces was increased, due to the development of the oxygen functional groups. Consequently, the anodic oxidation led to an increase in surface free energy of the carbon fibers, mainly due to the increase of its specific (or polar) component. The mechanical interfacial properties of the composites, including ILSS and $K_{IC}$, had been improved in the anodic oxidation on fibers. These results were explained that good wetting played an important role in improving the degree of adhesion at interfaces between fibers and epoxy resin matrix.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.7
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• pp.675-681
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• 2012

The char oxidation characteristics of ashless coal with a relatively low ash content and high heating value were experimentally investigated at several temperatures (from $900^{\circ}C$ to $1300^{\circ}C$), in various oxygen concentrations (from 10% to 30%) under atmospheric pressure in a drop tube furnace. The char reaction rate was calculated from the exhaust gas concentrations (CO, $CO_2$) measured by FT-IR, and the particle temperature was measured by the two-color method. In addition, the activation energy and pre-exponential factor of ashless coal char were also calculated based on the Arrhenius equation. The results show that higher temperature and oxygen concentration result in a higher reaction rate of ashless coal, and the activation energy of ashless coal char is similar to that of bituminous coal.

• Fisheries and Aquatic Sciences
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• v.18 no.1
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• pp.21-26
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• 2015

Seasoned laver Pyropia spp. is a traditional Korean seafood that has gained popularity worldwide because of its unique taste, texture, and health benefits. It is prepared by roasting a sheet of dried laver, to which vegetable oils have been applied, at an ultra-high temperature (UHT) of $300^{\circ}C$. Therefore, the oxidative stability of the oils is the most important factor in determining the shelf life of seasoned laver products. In this study, we investigated changes in the thermal oxidative stability of six major vegetable oils (sesame, perilla, sunflower, rice bran, canola, and olive) during the seasoned laver processing. The oxidation induction time of each oil from the seasoned laver products was decreased compared with the fresh oil. These results indicate that the UHT treatment ($300^{\circ}C$, 10 s) induced thermal oxidation of the oils. Among the six seasoned laver oils, the induction times of olive (OL, 8.02 h) and sesame (SE, 5.31 h) oils were significantly higher than the other oils. The acid values (AVs) of OL and SE oils from the seasoned laver were 0.49 and 0.79, respectively. On the other hand, perilla oil had the overall worst thermal oxidative properties (induction time: 0.35 h, AV: 2.82). Our results provide useful information about seasoned laver products for researchers or manufactures.

• Journal of Energy Engineering
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• v.20 no.4
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• pp.346-352
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• 2011

The experiment was designed to study the char oxidation kinetics of pulverized coals commonly utilized in Korean power plants. The kinetics has been estimated using the Semenov's thermal spontaneous ignition theory adapted to coal char particle ignition temperature. The ignition temperature of coal char particle is obtained by a direct measurement of the particle temperature with photo detector as well as by means of a solid thermocouple which is used as both a heating and a measuring element. The ignition temperatures for subbituminous coal, Wira, and bituminous coal, Yakutugol, have been measured for 4 sizes in the range of 0.52-1.09 mm. The ignition temperature of the particle increases with the increasing diameter. The results were used to calculate the activation energy and the pre-exponential factor. As a result, the kinetic parameters are in an agreement with ones reported from other investigations.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.128-134
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• 2013

A study on the corrosion behavior of Inconel alloys and Incoloy 800H in molten salt of LiCl-$Li_2O$ was investigated at $650^{\circ}C$ for 24-312 hours in an oxidation atmosphere. The order of the corrosion rate was Inconel 600 < Inconel 601 < Incoloy 800H < Inconel 690. Inconel 600 showed the best performance suggesting that the content of Fe, Cr and Ni are the important factor for corrosion resistance in hot molten salt oxidation conditions. The corrosion products of Inconel 600 and Inconel 601 were $Cr_2O_3$ and $NiFe_2O_4$, In case of Inconel 690, a single layer of $Cr_2O_3$ was formed in the early stage of corrosion and an outer layer of $NiFe_2O_4$ and inner layer of $Cr_2O_3$ were formed with an increase of corrosion time. In the case of Incoloy 800H, $Cr_2O_3$ and $FeCr_2O_4$ were observed. Most of the outer scale of the alloys was observed to be spalled from the results of the SEM analysis and the unspalled scale which adhered to the substrate was composed of three layers. The outer layer, the middle one, and the inner one were Fe, Cr, and Ni-rich, respectively. Inconel 600 showed localized corrosion behavior and Inconel 601, 690 and Incoloy 800H showed uniform corrosion behavior. Ni improves the corrosion resistance and too much Cr and/or Fe content deteriorates the corrosion resistance.

• Journal of the Korean Chemical Society
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• v.18 no.2
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• pp.117-125
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• 1974

The catalytic reaction between carbon monoxide and oxygen was investigated in the presence of catalysts which were specially treated by applying an annealing method at different monoxide and oxygen and at reaction temperatures in the region of partial pressures of carbon $40^{\circ}C$ to $95^{\circ}C$. The oxidation rate is highest on NiO annealed at low temperature in vacuum. The data has been correlated with the first order kinetics, and the activation energies from the Arrhenius equation are found to be 4Kcal/mole in the region of the experimental temperatures. The excess oxygen in NiO obtained from the decomposition of $NiCO_3$does not cause activation at $95^{\circ}C$. But NiO catalysts annealed again in vacuum display activation even at $40^{\circ}C$. The quantity of the excess oxygen in NiO surfaces seems to be the controlling factor in determining the rates of oxidation of carbon monoxide.

• Journal of Food and Nutrition Research
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• v.9 no.3
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• pp.163-169
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• 2021

Decreased adipocyte fatty acid oxidation (FAO) and impaired preadipocyte differentiation characterize hypertrophic expansion of adipose tissue (AT) from obese and insulin resistant humans and are recognized as potential mechanisms for obesity-mediated dyslipidemia. Supplementation of formononetin (FMN), one of the principal isoflavones extracted from red clover or Huangqi (Astragalus roots), has been shown to have beneficial effects on obesity-related hyperlipidemia, a well-established cardiovascular risk factor. However, a target tissue and underlying mechanism(s) through which FMN acts have been under-investigated. Thus, we investigated whether FMN promotes adipocyte FAO and preadipocyte differentiation using 3T3-L1 preadipocytes to provide potential mechanisms of FMN action. We further extended this to the culture of 10T1/2 mesenchymal stem cells (MSCs) as well as mouse AT explants to reflect in vivo effects of FMN. In fully differentiated 3T3-L1 adipocytes, FMN-treatment significantly increased the expression levels of FAO-related proteins such as pAMPK, pACC, and CPT1, all of which were consistently upregulated in AT explant cultures treated with 10 μM FMN. In addition, FMN significantly enhanced the degree of differentiation of both 3T3-L1 preadipocytes and 10T1/2 MSCs into adipocytes as evidenced by Oil Red O staining of cellular lipids. This observation correlated with increased expression levels of key adipogenic transcription factors (PPARγ and C/EBPα) and their down-stream target proteins (FABP4, Glut4 and adiponectin). Moreover, FMN failed to exert its stimulatory effects on preadipocyte differentiation in both cell types in the presence of a PPARγ antagonist, suggesting a PPARγ-dependent effect of FMN. Collectively, these data provide possible mechanisms of action of FMN on lipid metabolism and further support the favorable in vivo effects of FMN in diet and obesity-induced dyslipidemia.

• Environmental Mutagens and Carcinogens
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• v.17 no.2
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• pp.78-91
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• 1997

Peroxisome is a single membrane-bounded organelle found in hepatic parenchymal cells and kidney tubular epithelial cells. A number of enzymes exist in peroxisome contributing to anabolic and catabolic peroxisomal functions. Extramitochontriai $\beta$-oxidation of fatty acid is a major function of peroxisome. Peroxisomes can be proliferated by many structually unrelated compounds such as hypolipidemic drugs, plasticizers, pesticides, some pharmaceutical agents and high fat diet. These chemicals, called peroxisome proliferators, act via the peroxisome proliferator activated receptor, to induce peroxisome proliferation, hepatomegaly and hepatocellular carcinoma in rodent. The clear mechanisms of peroxisome proliferator-induced hepatocarcinogenesis have been not demonstrated. Since they are not genotoxic, biochemical changes or changes in gene expressions may be involved. A free radical theory has been suggested based on the finding of oxidative damages of macromolecules by hydrogen peroxide released in the peroxisomal $\beta$-oxidation of fatty acid. Increased cell proliferation by a peroxisome proliferator has been also thought to be an important factor in the hepatocarcinogenesis as suggested in other cases of nongenotoxic carcinogenesis. The alternation of eicosanoid concentrations by peroxisome proliferators may be important in the peroxisome proliferator-induced hepatocarcinogenesis since peroxisome proliferators decrease the concentration of eicosanoids, and the peroxisome proliferator ciprofibrate-eicosanoid combination is comitogenic and costimulates some mitogenic signals in hepatocytes. All of proposed mechanisms should be considered in the peroxisome prolifrator-induced hepatocarcinogenesis.

• Journal of Hydrogen and New Energy
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• v.28 no.1
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• pp.70-76
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• 2017

To synthesize copper nanoparticle a thermal decomposition was adopted. And to solve the problem of surface oxidation of the synthesized copper powder an electroless Ag plating method was used. The size and shape of synthesized Cu nanoparticle were affected by the size of copper oxalate used as a precursor, reaction solvent, reaction temperature and amount of reducing agent. Especially reaction solvent is dominant factor to control shape of Cu nano-particle which can have the shapes of sphere, polygon and rod. In case of glycerol, it produced spherical shape of about 500 nm in size. Poly ethylene produced uniform polygonal shape in about 700 nm and ethylene glycol produced both of polygon and rod having size range between 500 and 1500 nm. The silver coated copper powder showed a high electrical conductivity.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.168-177
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• 1998

The effects of the regeneration parameters such as inlet gas temperature, space velocity, oxygen concentration of the exhaust gas, and initial particulate loading on the oxidation of the particulate inside ceramic cordierite filter have been investigated through an engine experiment. As the inlet gas temperature increases, the remarkable filter temperature occurs owing to the rapid combustion rate. Though the higher space velocity affirms the safe regeneration, it also requires much fuel consumption of the burner. For that reason, the space velocity should be compromised considering the fuel economy. The excessive accumulation of the particulate may cause undesirable regeneration temperatures inside filer even under the optimized regeneration condition. The inlet gas temperature should be selected to overcome the variation of the oxygen concentration which is inherent feature of the diesel engine. It is the most important factor in the regeneration control techniques.