• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.2
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• pp.127-132
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• 1999

Both motion of free metallic particles from which most GIS internal failures are caused and partial discharges from the particles were examined using EHV GIS test chamber. Effects from particle length and gas pressure which are main factors to lead to breakdown failure were investigated theoretically and experimentally. Magnitude of both lift-off voltage and partial discharge inception voltage were measured respectively and, through these measurements, this paper showed the possibility of predicting breakdown fault and of taking action to prevent the fault in advance. The measurement of partial discharge when the particles began to move could be adopted to decide minimum sensitivity in developing predictive diagnostic equipments. Both the amount of apparent discharge and real discharge in GIS were examined theoretically and experimentally, then experimental results were analyzed on the basis of the theory.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.595-596
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• 2012

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1773-1775
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• 2003

In this Study, the insulation safety for Closing Resistor and Disconnect Switch(DS) of 362kV GIS was estimated through 3 dimensional electric field analysis. In addition, the basic study to secure the electric insulation design technique was carried out through the research on the effect of a metallic particle which is generated in the GIS. As a result of 3 dimensional electric field analysis, it was found that the insulation capability of Closing Resistor and DS of 362kV GIS is stable electrically. Also, the fundamental data to improve the insulation capability of spacer was obtained by analyzing the maximum electric field according to the attached angle of a metallic particle which is attached on the surface of a spacer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1883-1889
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• 2013

Although Fe-Si based alloy has lower figure of merit than Si-Ge alloy applied for space probe, its low cost related to abundant raw material, rather simple processing, high temperature resistance and reliability up to $800^{\circ}C$ made it one of the most promising middle temperature thermoelectric generation materials. The effect of particle size and additive on the thermoelectric properties of p-$FeSi_2$ prepared by a RF inductive furnace was investigated. The electrical conductivity increased slightly with decreasing particle size and hence better grain-to-grain connectivity due to the increase of density. The Seebeck coefficient exhibited the maximum value at about 600~800K and decreased slightly with increasing particle size. This must be due to the amount of residual metallic phase ${\varepsilon}$-FeSi. $Fe_2O_3$ and/or $Fe_3O_4$-doped specimens showed the higher electrical conductivity and the lower Seebeck coefficient due to increase of the metallic phase and Si-vacancy. On the other hand, $SiO_2$-doped specimen showed the higher electrical conductivity and the higher Seebeck coefficients.

• Journal of Powder Materials
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• v.27 no.4
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• pp.339-342
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• 2020

Since the interaction between the second-phase particle and grain boundary was theoretically explained by Zener and Smith in the late 1940s, the interaction of the second-phase particle and grain boundary on the microstructure is commonly referred to as Zener pinning. It is known as one of the main mechanisms that can retard grain growth during heat treatment of metallic and ceramic polycrystalline systems. Computer simulation techniques have been applied to the study of microstructure changes since the 1980s, and accordingly, the second-phase particle-grain boundary interaction has been simulated by various simulation techniques, and further diverse developments have been made for more realistic and accurate simulations. In this study, we explore the existing development patterns and discuss future possible development directions.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.673-679
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• 2014

This study aims to investigate the indoor air quality by analyzing $PM_{10}$ concentration and metallic elements collected from high school(classroom, science room, assembly room). $PM_{10}$ concentration of a classroom, a science room, and an assembly hall during the research period was 87.7 ${\mu}g/m^3$, $75.3{\mu}g/m^3$, $64.6{\mu}g/m^3$, respectively. Si of $PM_{10}$ had highest concentration with 15,427 $ng/m^3$ followed by Na which had 7,205 $ng/m^3$, and the order was Si>Na>Ca>Mg>Fe>K in the classroom. $PM_{10}$ concentration of a classroom and a science room was each 104.8 ${\mu}g/m^3$ and 75.3 ${\mu}g/m^3$ during the semester and $PM_{10}$ concentration of a classroom and an assembly hall was each 80.9 ${\mu}g/m^3$ and 64.6 ${\mu}g/m^3$ during the summer vacation. Based on $PM_{10}$ and metallic concentration at a classroom on day of week, the concentration of Friday was highest with 112.0 ${\mu}g/m^3$, and that of Monday was lowest with 65.3 ${\mu}g/m^3$.

• Journal of Powder Materials
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• v.10 no.4
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• pp.228-234
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• 2003

In the present study, the focus is on the synthesis of titanium carbide/cobalt composite powder by the spray thermal conversion process using metallic salt solution as the raw materials. Two types of oxide powders of Ti-Co-O system were prepared by the spray drying of two types of metallic salt solutions : titanium chloride-cobalt nitrate and $TiO_2$ powder-cobalt nitrate solutions. These oxide powders were mixed with carbon black, and then these mixtures were carbothermal reduced under a flowing argon atmosphere. The changes in the phase structure and thermal gravity of the mixtures during carbothermal reduction were analysed using XRD and TG-DTA. In the case of using the titanium chloride-cobalt nitrate solution, it could not be obtained TiC/Co composite powder due to contamination of the impurities during the spray drying of the solution. However, in tile case of using the $TiO_2$ powder-cobalt nitrate scullion, TiC-15 wt. %Co composite powder could be synthesized by the spray thermal conversion process. The synthesized TiC-15 wt. %Co composite powder at 120$0^{\circ}C$ for 2 hours has average particle size of 150 nm.

• Journal of Powder Materials
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• v.28 no.1
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• pp.25-30
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• 2021

The surface of silicon dummy wafers is contaminated with metallic impurities owing to the reaction with and adhesion of chemicals during the oxidation process. These metallic impurities negatively affect the device performance, reliability, and yield. To solve this problem, a wafer-cleaning process that removes metallic impurities is essential. RCA (Radio Corporation of America) cleaning is commonly used, but there are problems such as increased surface roughness and formation of metal hydroxides. Herein, we attempt to use a chelating agent (EDTA) to reduce the surface roughness, improve the stability of cleaning solutions, and prevent the re-adsorption of impurities. The bonding between the cleaning solution and metal powder is analyzed by referring to the Pourbaix diagram. The changes in the ionic conductivity, H2O2 decomposition behavior, and degree of dissolution are checked with a conductivity meter, and the changes in the absorbance and particle size before and after the reaction are confirmed by ultraviolet-visible spectroscopy (UV-vis) and dynamic light scattering (DLS) analyses. Thus, the addition of a chelating agent prevents the decomposition of H2O2 and improves the life of the silicon wafer cleaning solution, allowing it to react smoothly with metallic impurities.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.548-551
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• 1999

The cure characteristics of metal particle filled DGEBA/MDA/SN/ zeolite epoxy resin composite system for EMI shielding were investigated by dynamic DSC run method and FT-lR spectroscopy. As the heating rate increased, the peak temperature on dynamic DSC curve increased because of the rapid cure reaction. From the straight line of the Kissinger plot, the curing reaction activation energy and pre-exponential factor could be obtained. As the post-curing time at 15$0^{\circ}C$ increased, the glass increased the glass transition temperature or the thermal stability increased. When the post curing time is too long, the system filled with metallic Al particle can be thermally oxidized by the catalytic reaction of metal filler and the thermal stability of the composite for the EMI shielding application may be decreased.

• Particle and aerosol research
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• v.5 no.4
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• pp.171-178
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• 2009

$PM_{2.5}$ is one of critical air pollutants due to its high absorbability of heavy metallic fumes, PAH and bacillary micro organisms. Such a fine particulate matter is often formed through various nucleation processes including condensation. This study attempts to find the nucleation behaviors of $PM_{2.5}$ arisen from coal power stations using a classical heterogeneous Fletcher's theory. The numerical simulation by C-language could approximate the nucleation process of $PM_{2.5}$ from water vapor, of which approach revealed the required energy for embryo formation and embryo size and nucleation rate. As a result of the calculation, it was found that wetting agents could affect the particle nucleation in vapor condensation. In particular, critical contact angle relates closely with the vapor saturation. Particle condensation could be reduced by lowering the angles. The wetting agents aid to decrease the contact angle and surface tensions, thereby may contribute to save the formation energy.