• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.1
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• pp.54-63
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• 2010

Recently, as the function of largest supplier of biomass for "low carbon green growth", the necessity for systematic management of afforestation areas is emphasizing. The forestation of seedling, besides the afforestation cost itself, is required some additional follow-up management costs, like mowing and fertilizing of forestation area, and removal of bindweed. The mulching mat for afforestation seedlings is available for rooting of little seedlings as well as initial forestation expenses. Mulching technique is also used to control soil temperature and moisture by covering the surface of ground. In this study, the paper based-mulching film coated with biodegradable polymer and functional additive was specially produced using laboratory bar coater, and analyzed for its degradable behavior. Coating colors were prepared by dissolving PE (polyester) 80 % and PLA(polylactic acid) 20 % in chloroform and finally applied to handsheet prepared by preceding study conditions. Base paper and polymer-coated paper were artificially aged by 2 kinds of degradation methods, which are soil degradation by microorganism and light degradation by 257 nm UV wavelengths. Strength property, oxidation index and morphological property were evaluated by reduction rates of tensile strength, FTIR spectra ratio of carboxyl and carbonyl group and SEM micrograph. As these results, polymer coated-paper was superior to base paper in degradation behaviors, having results with lower reduction rate of strength properties.

• Polymer(Korea)
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• v.39 no.2
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• pp.346-352
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• 2015

Polyalphaolefin (PAO) is a synthetic lubricant that is superior to mineral-based lubricants in the terms of physical and chemical characteristics such as low pour point, high viscosity index (VI), and thermal and oxidation stability. Several kinds of PAOs have been synthesized by using 1-pentene, 1-hexene, 1-octene, or 1-dodecene as monomer with three kinds of aluminum-based Lewis acid catalysts via cationic polymerization. The control of the catalytic performance and physical properties of PAO such like molecular weight, kinematic viscosity, pour point, and viscosity index was done by changing polymerization parameters. The alkyl aluminum halide-based catalysts show better catalytic activity than that of the conventional $AlCl_3$ catalyst. The microstructure of PAO was investigated by means of TOF-MS (time of flightmass spectroscopy) analysis in order to elucidate the correlation between the performances of the lubricant (VI, pour point) and the molecular structure of PAO. The VI of PAO increases with increases in the carbon number of ${\alpha}$-olefin. In other words, the performances of PAO as a lubricant strongly depended on the branch length of PAO.

• Mycobiology
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• v.43 no.3
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• pp.280-287
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• 2015

In this study, transcriptome analysis of twelve laccase genes in Pleurotus ostreatus revealed that their expression was differentially regulated at different developmental stages. Lacc5 and Lacc12 were specifically expressed in fruiting bodies and primordia, respectively, whereas Lacc6 was expressed at all developmental stages. Lacc1 and Lacc3 were specific to the mycelial stage in solid medium. In order to investigate their biochemical characteristics, these laccases were heterologously expressed in Pichia pastoris using the pPICHOLI-2 expression vector. Expression of the laccases was facilitated by intermittent addition of methanol as an inducer and sole carbon source, in order to reduce the toxic effects associated with high methanol concentration. The highest expression was observed when the recombinant yeast cells were grown for 5 days at $15^{\circ}C$ with intermittent addition of 1% methanol at a 12-hr interval. Investigation of enzyme kinetics using 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) as a substrate revealed that the primordium-specific laccase Lacc12 was 5.4-fold less active than Lacc6 at low substrate concentration with respect to ABTS oxidation activity. The optimal pH and temperature of Lacc12 were 0.5 pH units and $5^{\circ}C$higher than those of Lacc6. Lacc12 showed maximal activity at pH 3.5 and $50^{\circ}C$, which may reflect the physiological conditions at the primordiation stage.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2185-2190
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• 2018

Methane activation through oxychlorination is in the spotlight due to the relatively mild reaction conditions at atmospheric pressure and in the temperature range of $450-550^{\circ}C$. Although $CeO_2$ is known to exhibit good activity for methane oxychlorination, significant amounts of by-products such as $CO_2$, CO and carbon deposits are produced during the reaction over $CeO_2$. We investigated the effect of iron in $FeO_x/CeO_2$ catalysts on methane oxychlorination. $FeO_x/CeO_2$ with 3 wt% iron shows the maximum yield at $510^{\circ}C$ with 23% conversion of methane and 65% selectivity of chloromethane. XRD and $H_2$ TPR results indicate that iron-cerium solid solution was formed, resulting in the production of more easily reduced cerium oxide and the suppression of catalysts sintering during the reaction. Furthermore, the selectivity of by-products decreased more significantly over $FeO_x/CeO_2$ than cerium oxide, which can be attributed to the facilitation of HCl oxidation arising from the enhanced reducibility of the former sample.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.173-187
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• 2021

In the present research, a simple electrochemical sensor based on a carbon paste electrode (CPE) modified with ZnO-Zn₂SnO₄-SnO₂ and graphene (ZnO-Zn₂SnO₄-SnO₂/Gr/CPE) was developed for the direct, simultaneous and individual electrochemical measurement of Acetaminophen (AC), Caffeine (Caf) and Ascorbic acid (AA). The synthesized nano-materials were investigated using scanning electron microscopy, X-ray Diffraction, Fourier-transform infrared spectroscopy, and electrochemical impedance spectroscopy techniques. Cyclic voltammetry and differential pulse voltammetry were applied for electrochemical investigation ZnO-Zn₂SnO₄-SnO₂/Gr/CPE, and the impact of scan rate and the concentration of H⁺ on the electrode's responses were investigated. The voltammograms showed a linear relationship between the response of the electrode for individual oxidation of AA, AC and, Caf in the range of 0.021-120, 0.018-85.3, and 0.02-97.51 μM with the detection limit of 8.94, 6.66 and 7.09 nM (S/N = 3), respectively. Also, the amperometric technique was applied for the measuring of the target molecules in the range of 0.013-16, 0.008-12 and, 0.01-14 μM for AA, AC and, Caf with the detection limit of 6.28, 3.64 and 3.85 nM, respectively. Besides, the ZnO-Zn₂SnO₄-SnO₂/Gr/CPE shows an excellent selectivity, stability, repeatability, and reproducibility for the determination of AA, AC and, Caf. Finally, the proposed sensor was successfully used to show the amount of AA, AC and, Caf in urine, blood serum samples with recoveries ranging between 95.8% and 104.06%.

• Korean Journal of Exercise Nutrition
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• v.16 no.2
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• pp.113-122
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• 2012

This study assessed the amount of energy consumed and fat deposition after endurance training in order to review the effect of 4-week endurance exercise on resting metabolic rate of a mouse during and after exercise and the effect of exercise. A total of 19 seven-week-old ICR male mice were used as the study subject. Those mice were divided into sedentary group (Sed) and trained group (Tr) after a week of environment adaption. The Tr group was trained with endurance exercise five times a week for four weeks. Weight and the amount of food intake were daily weighed and resting metabolic rate and metabolic rate after exercise were assessed before starting exercise and on the fourth week after training. Metabolic rate during exercise were measured four weeks after training. At the end of breeding period, statistically significant difference was shown in weights of trained and sedentary groups (p < 0.05). During a resting period, no significant difference was shown in oxygen intake, respiratory exchange ratio, and the amount of carbohydrate and fat oxidized. Moreover, no significant difference was shown in excess post-exercise oxygen consumption (EPOC) of an hour period after training. In contrast, the maximal oxygen uptake (VO₂ max) was approximately 11.1% higher in trained group after training compare to before. However, there was no significant difference in respiratory exchange ratio and carbohydrate and fat oxidization. During exercise, oxygen uptake, carbon dioxide production, and respiratory exchange ratio in energy metabolism during exercise showed no significant difference. However, significant difference was exhibited in the amount of fat oxidized in both groups. Summing up those results, endurance exercise could be concluded to be effective in weight control. However, weight loss is thought to be resulted from increase in fat oxidization during exercise unlike the conclusion made from previous studies where weight loss is prominently influenced by energy metabolism during a resting period and increased fat oxidation during post-exercise recovery. All experimental procedures were carried out at the Animal Experiment Research Center of Konkuk University. This study was conducted in accordance with the ethical guidelines of the Konkuk University Institutional Animal Care and Use Committee.

• Korean Journal of Agricultural Science
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• v.43 no.2
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• pp.249-257
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• 2016

In this study, rapeseed extracts were obtained by supercritical carbon dioxide fluid extraction of defatted rapeseed to evaluate the stability and antioxidant activity of an oil-in-water (O/W) emulsion system. The oil-in-water emulsions were prepared from stripped soybean oil with different concentrations (0.3, 0.4, 0.5, and 0.6%) of rapeseed extract as an emulsifier. Their emulsion stability was compared to that of emulsions prepared with the commercial emulsifier, Tween 20 (Polysorbate 20, 0.2%). After stripping the soybean oil, the total tocopherol content was reduced from 51.4 g/100 g to 1.1 g/100 g. Emulsion stability and oxidative stability of emulsions prepared with Tween 20 and rapeseed extract as emulsifiers were evaluated. For 30 days droplet sizes of emulsions containing rapeseed extract (0.4, 0.5, and 0.6%) were not significantly different (p > 0.05). Similar results were obtained for emulsion stability (ES) and Turbiscan analysis, suggesting that the addition of rapeseed extract increased emulsion stability. The addition of rapeseed extract at more than 0.4% resulted in an emulsion stability comparable to the addition of 0.2% Tween 20. The antioxidative ability of rapeseed extract increased with the amount added in the emulsion. Moreover, the addition of 0.6% rapeseed extract resulted in the lowest emulsion peroxide values (10.3 mEq/L) among all treatments. Therefore, according to the stability of its antioxidative and physical stability properties, rapeseed extract from super critical extraction could be successfully applied to the food and cosmetic industries.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.802-807
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• 2015

In this study, we synthesized a new biocatalyst consisting of glucose oxidase (GOx), polyethyleneimine (PEI) and carbon nanotube (CNT) with addition of terephthalaldehyde (TPA) (TPA/GOx/PEI/CNT) for fabrication of glucose sensor that shows improved sensing ability and stability compared with that using other biocatalysts. Main bonding of the new TPA/GOx/PEI/CNT catalyst is formed by Aldol condensation reaction of functional end groups between GOx/PEI and TPA. Such formed bonding structure promotes oxidation reaction of glucose. Catalytic activity of TPA/GOx/PEI/CNT is evaluated quantitatively by electrochemical measurements. As a result of that, large sensitivity value of $41{\mu}Acm^{-2}mM^{-1}$ is gained. Regarding biosensor stability of TPA/GOx/PEI/CNT catalyst, covalent bonding formed between GOx/PEI and TPA prevents GOx molecules from becoming leaching-out and contributes improvement in biosensor stability. With estimation of the biosensor stability, it is found that the TPA/GOx/PEI/CNT catalyst keeps 94.6% of its initial activity even after three weeks.

• Korean Journal of Materials Research
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• v.26 no.7
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• pp.393-399
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• 2016

Flower-like nickel oxide (NiO) catalysts were coated on NiCrAl alloy foam using a hydrothermal method. The structural, morphological, and chemical bonding properties of the NiO catalysts coated on the NiCrAl alloy foam were investigated by field-emission scanning electron microscopy, scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, respectively. To obtain flower-like morphology of NiO catalysts on the NiCrAl alloy foam, we prepared three different levels of pH of the hydrothermal solution: pH-7.0, pH-10.0, and pH-11.5. The NiO morphology of the pH-7.0 and pH-10.0 samples exhibited a large size plate owing to the slow reaction of the hydroxide ($OH^-$) and nickel ions ($Ni^+$) in lower pH than pH-11.5. Flower-like NiO catalysts (${\sim}4.7{\mu}m-6.6{\mu}m$) were formed owing to the fast reaction of $OH^-$ and $Ni^{2+}$ by increased $OH^-$ concentration at high pH. Thus, the flower-like morphology of NiO catalysts on NiCrAl alloy foam depends strongly on the pH of the hydrothermal solution.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.670-676
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• 2016

Hydrogen town in Republic of Korea was established in 2013. Hydrogen as a byproduct produced by various processes of factories is used in hydrogen town facilities. As cell performance is affected by contaminations in fuel gas, various standards about impurities of fuel have been determined by many countries. This study shows performance degradation of single cell with impurities concentrations. Traces of carbon monoxide (CO) and hydrogen sulfide ($H_2S$)can cause considerable cell performance losses. For comparing the performances by poisoning of CO, acceleration test, I-V curve, constant current are performed. Both the CO and $H_2S$ poisoning rate are a function of their concentration. With the higher concentrations the higher poisoning rates are observed. And, it was confirmed that, oxidation behavior and side reaction generation are not affected. Under the lower $H_2S$ concentration condition, the poisoning rate is much higher than that of CO because of its different adsorption intensity. It can be possible that the result of this study can be used for enacting regulation as a baseline data.