• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4587-4592
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• 2013

GPS is recognized the essential method to obtain the best result in the sphere of earth science that is setting of International Reference Frame, decision of the rotation coefficient about the earth rotation axis, detection of the crustal deformation, and observation of the diastrophism by high precision positioning except for navigation, geodetic survey and mapping. Therefore, in this study, it was attempted to build an expert service that enables non-experts to use high-precision GPS data processing. As a result, an Precise Point Positioning Solution that can maximize user convenience simply by entering the minimum required information for GPS data processing was developed, and the result of Precise Point Positioning Solution using GPS data provided by National Geographic Information Institute was compared with result of ITRF.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.5
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• pp.222-228
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• 2019

In this study, we carried out the experiment to prepare lithium carbonate powder through gas-liquid reactions with a lithium-containing solution and $CO_2$ gas using lithium hydroxide, lithium chloride, and lithium sulfate. Thermodynamically, the carbonation reaction of a lithium-containing solution showed that aqueous reaction of lithium hydroxide occurs spontaneously, but aqueous reactions of lithium chloride and lithium sulfate does not occur spontaneously. In the case of lithium hydroxide solution, the recovery rate of lithium carbonate was 69.8 % at room temperature ($25^{\circ}C$), and increased to 89.4 % at $60^{\circ}C$. In the case of lithium chloride and lithium sulfate solution, lithium carbonate could be prepared using sodium hydroxide as an additive, but the recovery rates were 19.2 % and 16.7 %, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2409-2414
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• 2002

The surfaces of prototypes become rough due to the stair-stepping which is the inevitable phenomenon in the Rapid Prototypes are not used only for the verification of feature. The grinding, coating, or the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. The solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. the solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the regions for post-processing. the factors to cause the surface roughness and their effects are analyzed through the experiments. Software modules are developed to predict the surface roughness of each face in the prototyping with the result. An experimental compensation method is developed to apply the modules to various RP equipments, materials and build styles. The build direction is searched with use of genetic algorithm to maximize the total areas of the surface of which roughness is better than the user-defined value.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.351-360
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• 1999

A large NaX type zeolite crystal of a uniform particle size of 20${\mu}{\textrm}{m}$ are grown with various H2O content by hydrothermal reaction and added seed crystal (2~3 ${\mu}{\textrm}{m}$) to reactant solution as a function of different adding seed levels from 3 to 15 %. The result that increased purity of NaX zeolite above 95% and homogeneity of crystal size by increasing adding seed levels, also decreased crystallization time. It was explained that adding seed to synthesis solution leaded out increase of surface area of physical contact reaction and directed growth of seed crystal, so more rapid consumption of reaction gel as increase seeding levels.

• ETRI Journal
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• v.22 no.1
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• pp.20-29
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• 2000

In this paper, we present a design of video and audio single chip encoder/decoder for portable multimedia application. The single-chip called as video audio signal processor (VASP) consists of a video signal processing block and an audio single processing block. This chip has mixed hardware/software architecture to combine performance and flexibility. We designed the chip by partitioning between video and audio block. The video signal processing block was designed to implement hardware solution of pixel input/output, full pixel motion estimation, half pixel motion estimation, discrete cosine transform, quantization, run length coding, host interface, and 16 bits RISC type internal controller. The audio signal processing block is implemented with software solution using a 16 bits fixed point DSP. This chip contains 142,300 gates, 22 Kbits FIFO, 107 kbits SRAM, and 556 kbits ROM, and the chip size is $9.02mm{\times}9.06mm$ which is fabricated using 0.5 micron 3-layer metal CMOS technology.

• Journal of Korea Foundry Society
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• v.36 no.6
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• pp.195-201
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• 2016

The effects of Mg addition on heat treatment and mechanical properties of A356 alloy were investigated. With increased amounts of Mg addition to A356 alloy, the grain size decreased and eutectic Si was refined. And, this process can improve the mechanical properties. Solid solution heat treatment causes the spheroidizing of eutectic Si. In this study, although eutectic Si was refined with Mg addition, solid solution time increased from 2 hours to 6 hours with Mg addition, and aging time also increased, from 4 hours to 8 hours. After heat treatment, Mg2Si remained in a formation of Chinese script. And, Chinese script Mg2Si formed with Mg addition caused a reduction of the elongation of the alloys according to the stress concentration.

• Journal of Surface Science and Engineering
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• v.50 no.2
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• pp.114-118
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• 2017

Bismuth telluride ($Bi_2Te_3$) and its alloys are well-known thermoelectric materials for ambient temperature applications. In this study, the dissolved Bi-Te precursor solution was used to synthesis metallic $Bi_2Te_3$ powder via ultrasonic spray pyrolysis and reduction process. The droplets of the Bi-Te precursor solution were decomposed to Bi-Te oxide powders by ultrasonic spray pyrolysis. The spherical $Bi_2Te_3$ powders were synthesized by reduction reaction in atmosphere of hydrogen gas at the temperature above $375^{\circ}C$ for 6h. The reduced $Bi_2Te_3$ powders have a mean particle size of $1.5{\mu}m$. The crystal structure of the powder was evaluated by X-Ray diffraction(XRD), and the microstructure with size and shape powders was observed by fieldemission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM).

• Proceedings of the Korean Society of Rheology Conference
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• 2003.05a
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• pp.3-6
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• 2003

• Bulletin of Food Technology
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• v.26 no.4
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• pp.296-306
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• 2013

• Resources Recycling
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• v.17 no.1
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• pp.80-87
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• 2008

Cementation and solvent extraction processes were studied to separate nickel and iron ions from the $H_2SO_4$ leaching solution with 47 g/L $Fe(Fe^{2+}/Fe^{3+}=1.03),$, 23.5 g/L Ni and 0.90M $H_2SO_4$ which leached from Fe-Ni alloy. Iron powder was used as a reducing agent for the cementation of Ni ion from the leaching solution. The reduction percentage of Ni ion was $17{\sim}20%$ by adding 4 times stoichiometric amount of iron powder at $60{\sim}80$. This may result from the fact that the cementation of Ni ion occurred after the reduction of $Fe^{3+}$ to $Fe^{2+}$ and the neutralization of $H_2SO_4$ with iron powder. The cementation process was proved to be unfeasible for the separation/recovery of Ni ion from the leaching solution including $Fe^{3+}$ as a major component. $Fe^{2+}$ present in the leaching solution was converted to $Fe^{3+}$ for solvent extraction of Fe ion using D2EHPA in kerosene as a extractant. The oxidation of $Fe^{2+}$ to $Fe^{3+}$ was completed by the addition of 1.2 times stoichiometric amount of 35% $H_2SO_4$. 99.6% $Fe^{3+}$ was extracted from the leaching solution (23.5 g/L $Fe^{3+}$) by 4 stages cross-current extraction using 20 vol.% D2EHPA in kerosene. $NiSO_4$ solution with 98.5% purity was recovered from the $H_2SO_4$ leaching solution of scrapped Fe-Ni alloy.