• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.519-523
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• 2006

$LiFePO_4$ has been received attention as a potential cathode material for the lithium secondary batteries. In our study, $LiFePO_4$ cathode active materials were synthesized by a solid-state reaction. It was modified by coating $TiO_2$ and carbon in order to enhance cyclic performance and electronic conductivity. $TiO_2$ and carbon coatings on $LiFePO_4$ materials enhanced the electronic conductivity and its charge/discharge capacity. For lithium polymer battery applications, $LiFePO_4$/solid polymer electrolyte (SPE)/Li and $LiFePO_{4}-TiO_{2}/SPE/Li$ cells were characterized by a cyclic voltammetry and charge/discharge cycling. The electrode with $LiFePO_{4}-carbon-TiO_{2}$ in PVDF-PC-EC-$LiClO_{4}$ electrolyte showed promising capacity of above 100 mAh/g at 1C rate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.368-369
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• 2006

The pure $LiFePO_4$, carbon added $LiFePO_4(LiFePO_4/C$) and pyrene added $LiFePO_4(LiFePO_4/P$) are synthesized by using solid-state reaction. XRD patterns show no impurity phase in the three kinds of the cathode materials. The 10wt% pyrene added $LiFePO_4$ shows around 140mAh/g of discharge capacity at 3rd cycle compared to the pure $LiFePO_4$. The carbon added $LiFePO_4$ shows 145mAh/g of discharge capacity at 3rd cycle and stable cycle-life compared to the others.

• Proceedings of the Korean Society of Crop Science Conference
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• 2005.04a
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• pp.48-49
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• 2005

• Proceedings of the Korean Society of Crop Science Conference
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• 2005.04a
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• pp.50-51
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• 2005

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.9
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• pp.662-670
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• 1991

Fast analysis method for calculating the radiation pattern of offset dual reflector antenna are presented. The validity of proposed method was verified by comparing with results of PO/PO, GO/PO, and the equivalent paraboloid method. Proposed method is the series expansion method using the Zernike polynomials. The calculated results by using the Zernike polynomials are in good agreement with obtained results by GO/PO and equivalent paraboloid method except PO/PO.

• Transactions on Electrical and Electronic Materials
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• v.13 no.4
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• pp.177-180
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• 2012

In this study, we prepared $LiFePO_4$- poly (sodium 4-styrenesulfonate) (PSS) composite by the hydrothermal method and ball-milling process. Different wt% PSS were added to $LiFePO_4$. The cathode electrodes were made from mixtures of $LiFePO_4$-PSS: SP-270: PVDF in a weighting ratio of 70%: 25%: 5%. $LiFePO_4$-PSS powders were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). The electrochemical properties of $LiFePO_4$-PSS/Li batteries were analyzed by cyclic voltammetry, charge/discharge tests, and AC impedance spectroscopy. A Li/$LiFePO_4$-PSS battery with 4.75 wt% PSS shows the best electrochemical properties, with a discharge capacity of 128 mAh/g.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1495-1498
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• 2005

Due to an efficient red emission, $Eu^{+3}$ ions have doped in various host materials. Eu-doped $LaPO_4/LaPO_4$ core/shell nanophosphor which emits red light in visible range, was synthesized by using a solution system. The mean size of the nanoparticle observed by TEM was about 7-8 nm. In this core/shell system, the thickness of $LaPO_4$ shell was optimized on the basis of relative PL emission intensity. In addition, the luminescent properties of $LaPO_4:Eu/LaPO_4$ core/shell particle have been compared with Eu-doped $LaPO_4$ bulk particle and nanoparticle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05b
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• pp.5-9
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• 2005

$LiFePO_4$ is a potential candidate for the cathode material of the lithium polymer batteries. $LiFePO_4$ cathode active materials were synthesized by coating on the $LiFePO_4$ was tried using $TiO_2$ and corbon in oreder to increase cyclic performance and electronic conductivity. Highly dispersed on the particles enhances the electronic conductivity and increases the capacity. For lithium polymer battery applications, $LiFePO_4$/SPE/Li and $LiFePO_4$-$TiO_2$/SPE/Li 'cells were characterized electrochemically by cyclic volatammetry and charge/discharge cycling. The $LiFePO_4$-carbon-$TiO_2$ cathode in PVDF-PC-EC-$LiCIO_4$ electrolyte showed high capacity at high current density.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.319-322
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• 2006

Under the national project for the development of 2MW wind energy convert system, we are under development of the prototype of 2MW wind turbine with low speed gearbox. This system adopts low speed gear box with planetary and spur gear and is pitch regulated variable speed type with the synchronous permanent magnet generator. The compromised size of generator in diameter and width are adopted to meet the structural design requirements. In this paper, the concept study for the type, the aerodynamic design for the blade and the details of load calculation will be presented. The detailed characteristics of the system will also be introduced.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.4
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• pp.1389-1408
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• 2021

Proof-of-Work (PoW) is the first and still most common consensus protocol in blockchain. But it is costly and energy intensive, aiming at addressing these problems, we propose a consensus algorithm named Proof-of-Work-and-Block-Compression (PoW-BC). PoW-BC is an improvement of PoW to compress blocks and adjust consensus parameters. The algorithm is designed to encourage the reduction of block size, which improves transmission efficiency and reduces disk space for storing blocks. The transaction optimization model and block compression model are proposed to compress block data with a smaller compression ratio and less compression/ decompression duration. Block compression ratio is used to adjust mining difficulty and transaction count of PoW-BC consensus protocol according to the consensus parameters adjustment model. Through experiment and analysis, it shows that PoW-BC improves transaction throughput, and reduces block interval and energy consumption.