• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.560-563
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• 2008

A modified polyol process is developed to enhance Pt loading during the preparation of Pt/C catalysts. With the help of the zeta potential, the effect of pH on the electrostatic forces between the support and the Pt colloid is investigated. It is shown experimentally that the surface charge on the carbon support becomes more electropositive when the solution pH is changed from alkaline to acidic. However, this change does not affect the electronegative surface charge of Pt colloids already attained and stabilized by glycolate anions. This new behavior caused by the change in the solution pH accounts for the enhanced yield of the process and does not affect the Pt particle size. All our experimental results reveal that this simple modification is a cost effective method for the synthesis of highly Pt loaded Pt/C catalysts for fuel cells.

• Journal of the Korean Chemical Society
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• v.57 no.4
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• pp.461-471
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• 2013

Optimized geometrical structure, atomic charges, molecular electrostatic potential, nonlinear optical (NLO) effects and thermodynamic properties of the title compound N-(2,5-methylphenyl)salicylaldimine (I) have been investigated by using ab initio quantum chemical computational studies. Calculated results showed that the enol form of (I) is more stable than keto form. The solvent effect was investigated for obtained molecular energies, hardneses and the atomic charge distributions of (I). Natural bond orbital and frontier molecular orbital analysis of the title compound were also performed. The total molecular dipole moment (${\mu}$), linear polarizability (${\alpha}$), and first-order hyperpolarizability (${\beta}$) were calculated by B3LYP method with 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) basis sets to investigate the NLO properties of the compound (I). The standard thermodynamic functions were obtained for the title compound with the temperature ranging from 200 to 450 K.

• Asian-Australasian Journal of Animal Sciences
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• v.11 no.1
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• pp.13-16
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• 1998

A $2{\times}2{\times}4$ factorial study was conducted to examine the possibility of improving estimates of in vitro digestibility, using untreated (UBS) and ammonia-treated (ABS) barley straw, through homogenization of rumen fluid (RF) and by additions of urea (U) and casein (C) as N sources and Xylose + Glucose (XG) as energy sources into artificial saliva. Digestibiltiy of ABS was significantly greater than that of UBS (p < 0.001). There was a significant decrease in digestibility when additions (U, UC, UCXG) were compared with the control (p < 0.001). A 2-way interaction between RF and straw type was significant (p < 0.05) for dry matter digestibility (DMD). Homogenization of RF increased DMD of ABS (p < 0.05) whereas it decreased DMD of UBS (p > 0.05). The study showed that addition of N alone or in combination with energy sources was not better than control, rather the reverse, digestion was inhibited by a combination of U and casein (UC). It was concluded that sufficient N and branched chain fatty acids were supplied in the inoculum from sheep fed high protein grass cubes to support the growth of cellulolytic microbes during in vitro incubation. Further studies are, however, required to explore the potential of homogenization in improving the in vitro method to estimate digestibility of cereal straws.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.760-765
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• 2013

PID (potential induced degradation) of PV module is the degradation of module due to the high potential difference between the front surface of solar cells and ground when PV modules operate under high humidity and temperature conditions. PID is generally derived from the positive sodium ions in front glass that are accumulated on P-type solar cells. Therefore, some papers for the electrical characteristic of only front components as glass, EVA sheet, solar cell under PID generation condition were revealed. In this paper, we analyzed the different outputs of module with PID by considering the all parts of module including the back side elements such as glass, back sheet. Mini modules with one solar cell were fabricated with the various parts on front and back sided of module. To generate PID of module in a short time, the all modules were applied.1,000 V in $85^{\circ}C$, 85% RH. The outputs, dark IV curves and EL images of all modules before and after experiments were also measured to confirm the main components of module for PID generation. From the measured results, the outputs of all modules with front glass were remarkably reduced and the performances of modules with back and front glass were greatly deteriorated. We suggest that the obtained data could be used to reduce the PID phenomenon of diverse modules such as conventional module and BIPV (building integrated photovoltaic) module.

• Carbon letters
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• v.12 no.1
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• pp.31-38
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• 2011

This study experimentally investigated dicyclohexylammonium 2-cyanoacrylate (CA) as a potential comonomer for polyacrylonitrile (PAN) based carbon fiber precursors. The P(AN-CA) copolymers with different CA contents (0.19-0.78 mol% in the feed) were polymerized using solution polymerization with 2,2-azobis(isobutyronitrile) as an initiator. The chemical structure and composition of P(AN-CA) copolymers were determined by proton nuclear magnetic resonance and elemental analysis, and the copolymer composition was similar to the feeding ratio of the monomers. The effects of CA comonomer on the thermal properties of its copolymers were characterized differential scanning calorimetry (DSC) in nitrogen and air atmospheres. The DSC curves of P(AN-CA) under nitrogen atmosphere indicated that the initiation temperature for cyclization of nitrile groups was reduced to around $235^{\circ}C$. The heat release and the activation energy for cyclization reactions were decreased in comparison with those of PAN homopolymers. On the other hand, under air atmosphere, the P(AN-CA) with 0.78 mol% CA content showed that the initiation temperature of cyclization was significantly lowered to $160.1^{\circ}C$. The activation energy value showed 116 kJ/mol, that was smaller than that of the copolymers with 0.82 mol% of itaconic acids. The thermal stability of P(AN-CA), evidenced by thermogravimetric analyses in air atmosphere, was found higher than PAN homopolymer and similar to P(AN-IA) copolymers. Therefore, this study successfully demonstrated the great potential of P(AN-CA) copolymers as carbon fiber precursors, taking advantages of the temperature-lowering effects of CA comonomers and higher thermal stability of the CA copolymers for the stabilizing processes.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2101_2102
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• 2009

Solar energy has inestimable development potential. However, it is an extreme intermittent and inconstant energy source. The radiative energy output from the sun derives from a nuclear fusion reaction. So it is necessary to study the photovoltaic P-V characteristics according to the irradiation. The results show that the DC power of the photovoltaic system is increased along with the increasing values of irradiation and module.

• Journal of Nutrition and Health
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• v.33 no.3
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• pp.296-303
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• 2000

We examined the folate intakes and assessed folate nutritional status of Korean women with childbearing potential. A total of 91 healthy women aged between 15 and 49 participated. They were divided into three groups by their age : A(15-24 yrs), B(25-34 yrs) and C(35-49 yrs). Folate intakes were determined by direct analysis. The foods consumed for 24 hours were collected proportionally and assessed folate. Their blood drawn in fasting state were analyzed folate levels. Folate contents of food homogenate, plasma and erythrocyte were determined a microbiological method using Lactobacillus. casei (ATCC 7469). Prior to the micro-assay, the food homogenate were treated with alpha-amylase, protease and folate conjugase. Mean daily folate intake of the total subjects was 145.8$\mu\textrm{g}$/d and in each group of A, B, and C was 114.0$\mu\textrm{g}$/d, 141.6$\mu\textrm{g}$/d, and 164.6$\mu\textrm{g}$/d, respectively. That of group C was significantly higher than that of group A(p<0.05). However, those of all the groups were lower than compared to the Korean Recommened Dietary Allowances(RDA) for folate. Especially the subjects in the group A consumed folate least that was below the half of the Korean RDA. The mean energy intake of all subjects was 1638㎉/d and those in each group of A, B, and C did not meet the Korean RDA for energy. The energy intake were significantly correlated with folate intakes(r=0.5050, p<0.001). Mean plasma and erythrocyte folate concentrations of total subjects were 6.9ng/mL and 266.3ng/mL, respectively. None were found to be deficient both in plasma(<3ng/mL)and erythrocyte (<140ng/mL) folate levels. There was only one subject who had red blood cell folate level below 157ng/mL concentration. These results show that folate status of the Korean women of reproductive age is not much bad. But it should be better that letting them improve their folate status by increasing energy intake, choosing high folate foods.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.553-558
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• 2014

Microalgae are a promising alternative feedstock for biodiesel production because their growth rates and oil contents are higher than those of conventional energy crops. Microalgal lipid is mainly triacylglyceride that can be converted to biodiesel as fatty acid methyl esters through trans-esterification. In this paper, the influence of several important lipid inducing factors such as nutrient limitation and changes in salinity and metallic components in microalgae and their potential strategies to be used for biodiesel production are reviewed. Depending upon strains/species that we use, microalgae react to stresses by producing different amount of triacylglyceride and/or by altering their fatty acids composition. Although the most widely applied method is the nitrogen starvation, other potential factors, including nutrient surplus conditions and changes in salinity, pH, temperature and metal concentrations, should be considered to increase biodiesel productivity.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.12
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• pp.1663-1668
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• 2004

This study was carried out to evaluate the potential nutritive value of commonly found grasses collected at native pasture in West Sumatra, Indonesia during dry and rainy seasons. Variables measured included chemical composition, in vitro digestibility, concentration of Ca, P and Mg, gas production and metabolizable energy (ME) content of the grasses. The results showed that species and season had significant effect on chemical composition and mineral concentration. Crude protein content in the dry season ranged from 6.5% (B. decumbens) to 14.4% (P. maximum) and increased slightly from 7.8% (B. decumbens) to 14. 8% (A. compressus) in the rainy season. Data on fiber fraction showed that grass contained more NDF, ADF and ADL in dry season than in rainy season. Data on mineral concentration showed that C. plectostachyus and P. maximum in dry season had higher Ca than those of other species, while in rainy season P. maximum had highest Ca concentration. In dry season, the DMD varied from 50. 4% (P.purpuphoides) to 59.1% (P. purpureum), while in rainy season ranged from 50.3% (A. gayanus) to 61.8% (P. purpureum). The potential and rate of gas production were significantly (p<0.05) affected by species and season. During dry season, potential of gas production ranged from 21.8 ml/200 mg (A. compressus) to 45.1 ml/200 mg (C. plectostachyus), while in rainy season it varied from 35.6 ml/200 mg (A. gayanus) to 47.5 ml/200 mg (P. purpureum). ME content of grasses varied from 6.0 to 8.3 MJ/kg in dry season and increased slightly from 6.4 to 8.6 MJ/kg in rainy season. Both in dry and rainy seasons, the highest ME content was occurred in P. purpureum and C. plectostachyus. In conclusion, nutritive value of the observed grasses in West Sumatra, Indonesia was relatively higher during rainy season compared with dry season. Pennisetum purpureum and Cynodon plectostachyus had the best nutritive value in both dry and rainy seasons.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.43-49
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• 2013

This work investigated the effects of engine speed and injection timing on combustion and emissions characteristics in a partially premixed charge compression ignition (pPCCI) engine fueled with DME. pPCCI engine especially has potential to achieve more homogeneous mixture in the cylinder, which results in lower NOx and smoke emission. In this study single cylinder engine was equipped with common rail and injection pressure is 700 bar. Total injected fuel mass is 64.5 $mm^3$ per cycle. The amount of pilot injection of the entire injection 12.5% is tested. Results show that NOx emission is decreased while IMEP is increased as the retard of injection timing. Besides, NOx emissions are slightly rised as well as IMEP is increased with the increase of engine speed.