• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.69-74
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• 2010

Methodologies to improve photovoltaic performance of dye-sensitized solar cell (DSSC) are reviewed. DSSC is usually composed of a dye-adsorbed $TiO_2$ photoanode, a tri-iodide/iodide redox electrolyte and a Pt counter electrode. Among the photovoltaic parameters of short-circuit photocurrent density, open-circuit voltage and fill factor, short-circuit photocurrent density is the collective measure of light harvesting, charge separation and charge collection efficiencies. Internal quantum efficiency is known to reach almost 100%, which indicates that charge separation occurs without loss by recombination. Thus, light harvesting efficiency plays an important role in improvement of photocurrent. In this paper, technologies to improve light harvesting efficiency, including surface area improvement by nano-dispersion, size-dependent light scattering efficiency, bi-functional nano material, panchromatic absorption by selective positioning of three different dyes and transparent conductive oxide (TCO)-less DSSC, are introduced.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.325-331
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• 2022

This study proposes a design method that minimizes a conduction loss of LCC resonant converter under rated condition. Through a simplified analysis of the waveform of the resonant current, the power transfer section and RMS value of the resonant current was analyzed mathematically and graphically. Based on this analysis, the design method that minimizes the RMS value of the resonant current is proposed. To demonstrate this method, this study designed a 7.5 kW (100 V, 75 A) capacitor charger based on LCC resonant converter and the design parameters were chosen according to the process of the design method. Then, the capacitor charger was implemented. An experiment was conducted to measure efficiency while satisfying design specifications under rated conditions. This design method was verified to be effective by achieving 97.7% maximum efficiency and design specifications under rated conditions.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.82-87
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• 1996

An optimized method for determining beta-emitting $^{241}$ Pu in the presence of alpha-emitting nuclides was developed using a liquid scintillation counting system. PSA-level was setting using pulse-shape discrimination. The $^{241}$ Pu counting channel was adjusted for maximum value of FM using the $^{241}$ Pu standard source. The volume of scintillant was determined for the maximum value of counting efficiency. The optimized method of $^{241}$ Pu has been applied to environmental samples to measure concentration of $^{241}$ Pu in soils and mosses. Also it has been identified the origin of Pu deposited in Korea from the activity ratio $^{241}$ Pu / $^{239,240}$Pu.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.129-129
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• 2012

Pumps are used widely in industry, the commercial sector and ships. A poorly selected pump or a pump that does not run at optimum design duty point is a classic symbol of wasted energy and money. It, therefore, becomes important to evaluate the efficiency of these pumps. This paper analyzes traditional technique and instrument to measure some parameters needed to calculate a pump efficiency. The pump efficiency measuring instrument (PEMI) was made and tested on real pump systems. It has been giver the accurate results compared with performance curve given by pump maker.

• Current Photovoltaic Research
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• v.4 no.1
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• pp.12-15
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• 2016

Screen printing technique followed by firing has commonly been used as metallization for both laboratory and industrial based solar cells. In the solar cell industry, the firing process is usually conducted in a belt furnace and needs to be optimized for fabricating high efficiency solar cells. The printed-Al layer on the silicon is rapidly heated at over $800^{\circ}C$ which forms a layer of back surface field (BSF) between Si-Al interfaces. The BSF layer forms $p-p^+$ structure on the rear side of cells and lower rear surface recombination velocity (SRV). To have low SRV, deep $p^+$ layer and uniform junction formation are required. In this experiment, firing process was carried out by using conventional tube furnace with $N_2$ gas atmosphere to optimize $V_{oc}$ of laboratory cells. To measure the thickness of BSF layer, selective etching was conducted by using a solution composed of hydrogen fluoride, nitric acid and acetic acid. The $V_{oc}$ and pseudo efficiency were measured by Suns-$V_{oc}$ to compare cell properties with varied firing condition.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.4
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• pp.41-49
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• 2016

Smart Grid is a next generation of new power growth electrical grid which provide high quality of electrical service by using Information Technologies to increase intelligence and performance. By using Smart Grid system, it can support energy management such as increase quality of electrical power, decrease energy and decrease emissions. However, Smart Grid uses information of energy consumption and when Smart Grid collects information, it will create private information. In this thesis, it will address issues of security private information which caused by Smart Grid for administrative measure and efficiency of Smart Grid in domestic. Also, cryptographic module algorithm, latest security solutions and strong wireless security policy for network environment such as wireless communication Iinternet are require for Smart Grid perform successfully and protect national power network equipment from cyber-attack and can stop leakage of user's personal information. Finally, it is urgent to prepare protection measures of National industrial facilities and power grid which can prepare for a cyber terrorism and penetration attacks and build emergency countermeasure management team for Smart Grid are require for safe Smart Grid environment.

• 한국정보컨버전스학회:학술대회논문집
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• 2008.06a
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• pp.131-134
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• 2008

A Mobile Ad hoc NETwork(MANET) is a system of wireless mobile nodes that dynamically self-organize in arbitrary and temporary network topologies. In the highly dynamic environment of MANET, energy efficiency is an important performance measure since it directly affects the network lifetime. The failure of energy severely impacts a communications system in crucial communications environments, such as disasters salvage. In this study, we propose a new packet switching routing that can increase the durability of the energy resource and therefore, the lifetime of the mobile nodes and MANET. The performance of the packet switching routing on the node-disjoint multipath and that of AODV are compared by NS2 simulation. The simulation results indicate that this new switching routing can extend the lifetime of a MANET.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.664-675
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• 1990

In this study, the performance test and heat transfer experiment for a 4 cylinder and 4-cycle turbocharged gasoline engine were carried out in order to measure the heat transfer coefficient at the inner wall of the combustion chamber. From the result of heat transfer experiment, the energy balance of the fuel energy and the overall efficiency of the turbocharger were calculated, The variation of them was investigated as well with the engine operation conditions.

• Journal of the Korean Society of Combustion
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• v.19 no.4
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• pp.14-20
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• 2014

In the present study, an annular combustor for a 500 W class micro gas turbine generator was designed and its characteristics were investigated by using both numerical and experimental methods. For this purpose, geometrical configurations of the annular combustor were determined in the aspect of the aerodynamic and chemical consideration. Also, fluid flow and pressure drop characteristics in the combustor were numerically studied by using commercial tool, FLUENT. Based on the numerical results, the diameter and the angle of air admission holes in the primary zone were chosen to be 2.5 mm and $30^{\circ}$, respectively. Finally, an integrated test unit, which consisted of a compressor, combustor, turbine, and motor/generator, was developed in order to measure the combustor efficiency. As the temperature difference between the combustor inlet and the turbine inlet or the air mass flow rate increased, the combustor efficiency increased and it was over 90% when the air mass flow rate was larger than 7.30 g/s. It was shown that the annular combustor developed in this study met the design requirement for a 500 W class micro gas turbine generator.

• KIEAE Journal
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• v.15 no.1
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• pp.77-82
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• 2015

The purpose of this study is to compare the thermal insulation performance of windows according to the formation of air layer and to evaluate its energy efficiency on a selected standard house. A thermal insulation test, KS F 2278 was used to measure U-values (Heat transmission coefficients) for the following three cases: the first case (Case 1) is a Low-E pair glass (Argon injected), the second case (Case 2) is a Low-E pair glass with the air cap attached on the glass surface, and the third case (Case 3) is a Low-E pair glass, on the frame of which the air cap is attached. The evaluation of the energy efficiency was conducted according to a building energy calculation method from ISO 13790, calculation of energy use for space heating and cooling, using the U-values obtained from the thermal insulation tests. As results of the tests, the U-values of Case 1, Case 2, and Case 3 were $1.668W/m^2{\cdot}K$, $1.568W/m^2{\cdot}K$, and $1.319W/m^2{\cdot}K$ respectively. The Case 2 had about 5.9% lower value than the Case 1, and the Case 3 had about 20.9% lower value than the Case 1. It seems that the thermal performance of the windows is attributed to an increase of the heat resistance and the thickness of air layer. An evaluation of the energy efficiency of the three cases on the selected standard house showed that the amount of heating energy demand per unit area was $7.776kWh/m^2{\cdot}yr$ for the Case $1,6.856kWh/m^2{\cdot}yr$ for the Case 2, and $4.856kWh/m^2{\cdot}yr$ for the Case 3. This study suggests that the formation of air layer (by using air cap) and its thickness should reduce the heat energy demand and thus improve the energy saving efficiency