• Advances in Energy Research
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• v.4 no.3
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• pp.189-202
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• 2016

This work emphasized optimum production of biodiesel using non-edible Prunus armeniaca (Bitter Apricot) oil via transesterification collected from the high altitude areas of Himachal Pradesh, India. In this study the author produced biodiesel through the process of transesterification by using an alkali catalyst with alcohol (methanol and ethanol), under the varying molar ratio (1:6, 1:9, 1:12), variable catalyst percentage (1% and 2%) and temperature ($70^{\circ}C$, $75^{\circ}C$, $80^{\circ}C$, $85^{\circ}C$). Furthermore, a few strong base catalysts were used that includes sodium hydroxide, potassium hydroxide, sodium metal and freshly prepared sodium methoxide. After screening the catalyst, response surface methodology (RSM) in connection with the central composite design (CCD) was used to statistically evaluate and optimize the biodiesel production operation using NaOH as catalyst. It was found that the production of biodiesel achieved an optimum level biodiesel yield with 97.30% FAME conversion under the following reaction conditions: 1) Methanol/oil molar ratio: 1:6, 2) Reaction time: 3h, 3) Catalyst amount: NaOH 2 wt. %, and 4) Reaction temperature: $85^{\circ}C$. The experimental results showed that the optimum production and conversion of biodiesel through the process of transesterification could be achieved under an optimal set of reaction conditions. The biodiesel obtained showed appropriate fuel properties as specified in ASTM, BIS and En- standards.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.1015-1020
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• 2012

Resistance of the front electrode is the highest proportion of the ingredients of the series resistance in crystalline silicon solar cell. While resistance of the front electrode is decreased with larger area, it induces the optical loss, causing the conversion efficiency drop. Therefore the front electrode with high aspect ratio increasing its height and decreasing is necessary for high-efficiency solar cell in considering shadowing loss and resistance of front electrode. In this paper, we used the screen printing method to form high aspect ratio electrode by multiple printing. Screen printing is the straightforward technology to establish the electrodes in silicon solar cell fabrication. The several printed front electrodes with Ag paste on silicon wafer showed the significantly increased height and slightly widen finger. As a result, the resistance of the front electrode was decreased with multiple printing even if it slightly increased the shadowing loss. We showed the improved electrical characteristics for c-Si solar cell with repeatedly printed front electrode by 0.5%. It lays a foundation for high efficiency solar cell with high aspect ratio electrode using screen printing.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.502-507
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• 2014

In this paper, performance characteristics of cycles were studied when mixed working fluid was used for ocean thermal energy conversion (OTEC). Among the various mixed refrigerants for industrial heat-pump, R32/R152a used in ocean thermal energy conversion system. For simulations, R32/R152a were used in existing closed cycle and Kalina cycle which is used only ammonia and water as mixed refrigerant. Temperature of the warm heat source was 26 and 29 celsius degree, temperature of the cold heat source was 5 celsius degree. In results of simulation, Gross power of the closed cycle on R32 was 22kW, and efficiency of the cycle was 2.02%. When the mixed refrigerant of R32/R152a, in the ratio of 90 to 10, gross power of the closed cycle was 29.93kW, and efficiency of the cycle was 2.78%. Gross power and cycle efficiency of R32/R152a increased by 36% and 37% than those of existing single refrigerant. Additionally, the same simulations were conducted in Kalina cycle with the same various composition ratio of mixed refrigerant.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.4
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• pp.323-330
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• 2017

Ash remaining after coal combustion was used as a catalyst support for tar steam reforming with various proportions of $Al_2O_3$ added for higher reforming efficiency. At a constant Ni content of 12 wt%, a coal ash and $Al_2O_3$ were mixed at a ratio of 5:5, 7:3, 9:1. As a result, the catalytic activity for toluene steam reforming was improved by adding $Al_2O_3$ at $500-600^{\circ}C$. The catalysts with ratio 7:3 and 5:5 reached toluene conversion of 100% above $700^{\circ}C$. When comparing the catalysts in which the coal ash and $Al_2O_3$ mixed at a ratio of 5:5 and 7:3 with the Ni/Al catalyst, it was concluded that this coal ash catalyst has efficient catalytic performance.

• Journal of Animal Science and Technology
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• v.61 no.6
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• pp.305-312
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• 2019

This study was carried out to investigate the effects of dietary energy levels on growth performance, blood parameter, and intestinal morphology of Pekin ducks in low temperature. A total of 500, 21-d-old Pekin ducks (initial BW = 1,089 ± 5.21 g) were evenly assigned to five dietary treatments (2,950, 3,000, 3,050, 3,100, or 3,150 kcal AME/kg, calculated on an as-is basis) with four replicates (pens) for each treatment (25 ducks per pen). During the experiment, hens were provided with feed and water ad libitum. Overall, increasing dietary energy levels corresponded to an increase of final body weight and body weight gain (linear, p < 0.01). Feed intake decreased (linear, p < 0.01) and feed conversion ratio increased (linear, p < 0.01) with increasing levels of energy. There were no significant differences (p < 0.05) in the level of leukocytes between groups. However, heterophils decreased (quadratic, p < 0.05) and lymphocytes increased (linear, p < 0.01) as inclusion of dietary energy levels increased. The H/L ratio increased (linear, p < 0.01) with increasing dietary energy levels while serum corticosterone levels decreased at overall experimental periods. Triglycerides increased (linear and quadratic, p < 0.05) with increasing dietary energy levels. There were no significant changes in villus height or crypt depth of the jejunum at overall experimental. In conclusion, increasing concentrations of dietary energy levels up to 2,950-3,150 kcal/kg in diet. Additionally, 3,150 kcal/kg dietary energy had been revealed more beneficial and could be practiced as protective management for the Pekin ducks reared under low ambient temperature (8℃ to 10℃).

• Clean Technology
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• v.26 no.1
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• pp.72-78
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• 2020

The use of fossil fuel and biogas production causes air pollution and climate change problems. Research endeavors continue to focus on converting methane and carbon dioxide, which are the major causes of climate change, into quality energy sources. In this study, a novel plasma-carbon converter was proposed to convert biogas into high quality gas, which is linked to photovoltaic and wind power and which poses a problem on generating electric power continuously. The characteristics of conversion and gas production were investigated to find a possibility for biogas conversion, involving parametric tests according to the change in the main influence variables, such as O₂/C ratio, total gas feed rate, and CO₂/CH₄ ratio. A higher O₂/C ratio gave higher conversions of methane and carbon dioxide. Total gas feed rate showed maximum conversion at a certain specified value. When CO₂/CH₄ feed ratio was decreased, both conversions increased. As a result, the production of solar fuel by plasma oxidation destruction-carbon material gasification conversion, which was newly suggested in this study, could be known as a possibly useful technology. When O₂/C ratio was 0.8 and CO₂/CH₄ was 0.67 while the total gas supply was at 40 L min^-1 (VHSV = 1.37), the maximum conversions of carbon dioxide and methane were achieved. The results gave the highest production for hydrogen and carbon dioxide which were high-quality fuel.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.1
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• pp.1-7
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• 2015

In this study, characteristics of reforming process of automotive liquefied petroleum gas (LPG) fuel using plasma reactor are investigated. Because plasma reformer technology has advantages of a fast start-up and wide fuel/oxidizer ratio of operation, and reactor size is smaller and more simple compared to typical combustor and catalytic reactor, plasma reforming is suitable to the on-board vehicle reformer. To evaluate the characteristics of the reforming process, parametric effect of $O_2/C$ ratios, reactant flow rate and metal form on the process were investigated. In the test of varying $O_2/C$ ratio from partial oxidation to stoichiometry combustion, conversion of LPG was increased but selectivity of $H_2$ decreased. The optimum condition of $O_2/C$ ratio for the highest $H_2$ yield was determined to be around 1.0 for 20~50 lpm, and 1.35 for 100 lpm. Specific energy density (SED) was major factor in reforming process and higher SED leads to higher $H_2$ yield. And metal form in the reformer increased $H_2$ yield of about 34 % as compared to the case of no metal form. The result can be a guide to map optimal condition of reforming process.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.84-90
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• 2015

Hydrogen has some remarkably high values of the key properties for transport processes, such as kinematic viscosity, thermal conductivity and diffusion coefficient. Hydrogen, as an energy medium, has some distinct benefits for its high efficiency and convenience in storage, transportation and conversion. Hydrogen has much wider limits of flammability in air than methane, propane or gasoline and the minimum ignition energy is about an order of magnitude lower than for other combustibles. Statistical thermodynamics provides the relationships that we need in order to bridge this gap between the macro and the micro. Our most important application will involve the calculation of the thermodynamic properties of the ideal gas.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.281-288
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• 1993

We have investigated the output characteristics and optimal conditions of a multi-stage amplifier system of Rhodamine 6G dye laser. The parameters in this simulation work were the beam diameter of the dye laser oscillator, the size of dye cell, the dye concentration, the number of stages in the amplifier system, and the pumping energy ratio of each amplifier at given pump energy. As a result, the output energy 10 mJ and the conversion efficiency of 40% in the two stage amplifier system were obtained with the pumping energy of 25mJ and the oscillator energy of 0.01 mJ.

• Bulletin of the Korean Chemical Society
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• v.21 no.8
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• pp.805-808
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• 2000

Mixed crystal powders based on Cd,Fe, and S have been synthesized by varying the ratio of CdS and $FeS_2in$ order to find a suitable material usefuI for the effectivc conversion of solar energy. Hydrogen gas was evolved only with CdS/Ptby photocatal ytic reaction under white light in an aqueous 1 M sodiumsulfite solution. From electrochemical studies of semiconductor electrodes. itwas shown that the onset potential shifted to the positive direction and that the bandgap energy also decreased as the molar ratio of Fe increased. A hydrogen evolution mechanism in terms of the conduction band potential and hydrogen evolution potential is proposed.