• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.686-686
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• 2013

Crystalline silicon solar cell is a semiconductor device that converts light into electrical energy. Screen printing is commonly used to form the front/back electrodes in silicon solar cell. Screen printing method is convenient but usually shows high resistance and low aspect ratio, which cause the efficiency decrease in crystalline silicon solar cell. Recently the plating method is applied in c-Si solar cell to reduce the resistance and improve the aspect ratio. In this paper, we investigated the effect of additional electroless Ag plating into screen-printed c-Si solar cell and compared their electrical properties. All wafers used in this experiment were textured, doped, and anti-reflection coated. The electrode formation was performed with screen-printing, followed by the firing step. Aften then we carried out electroless Ag plating by changing the plating time in the range of 20 sec~5 min and light intensity. The light I-V curve and optical microscope were measured with the completed solar cell. As a result, the conversion efficiency of solar cells was increased mainly due to the decreased series resistance.

• 한국재료학회지
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• 제17권9호
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• pp.489-492
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• 2007

Temperature and injection current dependence of elctroluminescence(EL) spectral intensity of the $In_{0.27}Ga_{0.73}N/GaN$ multi-quantum-well(MQW) have been studied over a wide temperature and as a function of injection current level. EL peaks also show significant broadening into higher photon energy region with the increase of injection current. This is explained by the band-filling effect. When temperature is slightly increased to 300 from 15 K, the EL emission peak showed red-blue-red shift. It can be explained by the carrier localization by potential fluctuation of multiple quantum well and band-gap shrinkage as temperature increase. It is found that a temperature-dependent variation pattern of the EL efficiency under very low and high injection currents show a drastic difference. This unique EL efficiency variation pattern with temperature and current is explained field effects due to the driving forward bias in presence of internal(piezo and spontaneous polarization) fields.

• KEPCO Journal on Electric Power and Energy
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• 제7권1호
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• pp.153-159
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• 2021

A two-step process for increasing the leaching efficiency of yttrium and neodymium from coal fly ash were investigated at solid loadings of 5.0 g ash ~1,000 g ash/l of 1.0 N~10.0 N H₂SO₄, temperature ranging from 30℃ to 90℃, ultrasonic leaching time of 1~10 hours, and ultrasonic power of 25~200 W. The yttrium and neodymium from coal fly ash were effectively leached into ion phases by step change of the first conventional dissolution at room temperature and then the second heating process with the aid of ultrasonic wave, and maximum leaching efficiency of yttrium and neodymium obtained were 66 % and 63 %, respectively. The activation energies for the leaching reaction of yttrium and neodymium at second heating process dependent on leaching time and temperature were derived to be 41.540 kJmol^-1 and 507.92 kJmol^-1, respectively. The optimum conditions for the maximum leaching of yttrium and neodymium were found to be the solid loading of 250 g ash/l of H₂SO₄, solvent concentration of 2.0 N H₂SO₄, and second step process of temperatures of 30℃ for 3 hours and then 90℃ for 4 hours with ultrasonic intensity of 100 W.

• 한국농공학회논문집
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• 제62권5호
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• pp.63-72
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• 2020

Solar-sharing, which is an agricultural photovoltaic system installing solar panels on the upper part of crop growing field, has especially drawn attention. Because paddy fields for cultivating crops are large flat areas, there have been various attempts to utilize solar energy for solar photovoltaic as well as growth of crops in agriculture. Solar-sharing was first proposed in Japan, and has been actively studied for optimization and practical uses. The domestic climate differs from the climate conditions in which the solar-sharing has been widely studied, therefore, it is required to develop the solar-sharing technology suitable for the domestic climate. In this study, a simulation model was developed to analyze the change of solar radiation resulted from the solar-sharing installation. Monthly solar illumination intensity and the change of illumination intensity according to the various conditions of solar panel installation were simulated. The results of monthly illumination analysis differed by altitude of the sun, which was related to season. In addition, it was analyzed that the monthly illumination decreased by up to 42% due to solar-sharing. Accordingly, it is recommended that solar-sharing should be installed as a way to maximize the efficiency of solar photovoltaic system while minimizing the decrease in solar radiation reaching the crops.

• 대한기계학회논문집B
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• 제28권3호
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• pp.281-288
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• 2004

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by improving the burning rate and by increasing the flame temperature. Flame figures, OH radical intensities, temperature distributions and emissions concentration were examined according to oxygen enriched concentration(OEC) in a turbulent diffusion flat flame. As long as the oxygen enriched concentration was increased, the length and volume of the flat flame was decreased while OH radical intensity was raised and the flame temperature was increased. However, RMS of the fluctuating temperature was decreased, and more homogeneous temperature field was formed. Thermal NO also was increased with increase of oxygen enriched concentration, but CO was decreased due to the increase of chemical reaction rate.

• 전기학회논문지P
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• 제62권2호
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• pp.79-83
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• 2013

An electronic ballast and magnetic ballast are two major types of ballasts used in HID(High Intensity Discharge) lamp. Compared with magnetic ballasts which can last for over 30 years and are recyclable at the end of their long lifetime, electronic ballasts have very short lifetimes due to the use of the electronic devices. In this paper, we developed a magnetic ballast for dual lamps and analyzed electrical characteristics and efficiency. As the experimental results, we confirm that the magnetic ballast for dual lamps makes it possible to effectively reduce current, active and reactive powers than conventional ballast.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 추계 학술대회논문집
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• pp.132-137
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• 2001

We used In-line orifice mixer for efficient chemicals mixing in water treatment. The method of using In-line orifice mixer has been already proved the improvement of water treatment efficiency. Code of computational fluid dynamics for numerical analysis was performed using FLUENT, a commercial code. As variable for exactly standardizing, a proper ratio between an outer diameter of deflector and a diameter of pipe, the distance between deflector and orifice, a determination of orifice diameter fur an optimal mixing, a distance between injection nozzle's position and cone, Numerical study has been performed for optimal standard and analyzed flow field on a basis of turbulent intensity in an orifice downstream.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1150-1151
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• 2008

Titanium-doped indium oxide (ITiO) films were prepared on soda-lime glass substrate using a magnetic null discharge (MND) sputter source. The ITiO thin films containing 10 wt.% Ti showed the minimum resistivity of ${\rho}=5.5{\times}10^{-3}{\Omega}cm$. The optical transmittance increases from 70% at 450 nm to 80% at 700 nm in visible spectrum. The surface roughness of the sample showed a change from 10 nm to 50 nm. The ITiO film used for TCO layer of DSCs exhibited an energy conversion efficiency of about 3.8 % at light intensity of 100 $mW/cm^2$.

• 한국레이저가공학회지
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• 제7권1호
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• pp.29-36
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• 2004

The dynamics of laser-induced plasma/shock wave and the interaction with a surface in the laser shock cleaning process are analyzed by optical diagnostics. Shock wave is generated by a Q-switched Nd:YAG laser in air or with N$_2$, Ar, and He injection into the focal spot. The shock speed is measured by monitoring the photoacoustic probe-beam deflection signal under different conditions. In addition, nanosecond time-resolved images of shock wave propagation and interaction with the substrate are obtained by the laser-flash shadowgraphy. The results reveal the effect of various operation parameters of the laser shock cleaning process on shock wave intensity, energy-conversion efficiency, and flow characteristics. Discussions are made on the cleaning mechanisms based on the experimental observations.

• Journal of Ceramic Processing Research
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• 제21권5호
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• pp.602-608
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• 2020

Bioelectromethanation was tested using an isolated strain, Methanothermobacter sp., for biogas upgrading. The investigated method showed faster bioelectrochemical conversion of carbon dioxide to methane with higher coulombic efficiency than previously reported without additional hydrogen and mediator supplementation. Bioelectromethanation can utilize carbon dioxide, unlike gas separation methods, and actually requires a less negative potential than in water electrolysis. The isolated methanogens showed a relatively fast conversion to methane compared to the previously reported methane production rate and current intensity. Through further research on electroactive methanogens and the development of operation technology, bioelectromethanation can be applied for biogas upgrading with a lower energy requirement but without CO2 emissions.