• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.406-409
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• 2001

The conductivity properties and synthesis of $LaNiO_{3}$ ceramics from $La_{1+\delta}NiO_{3}(\delta=-0.06,0,0.06)$ were investigated. A single perovskite phase was realized at $800^{\circ}C$. $La_{2}NiO_{4}$ and other unexpected oxide were observed at $1000^{\circ}C$. The Microstructure was showed clearly that it is a low density porous material. $LaNiO_3$ ceramic showed a metallic conductivity. The conductivity of La rich samples had a higher value than the La poor samples.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1388-1393
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• 2004

Investigators have been perplexed with the thermal phenomena behind the recently discovered nanofluids, fluids with unprecedented stability of suspended nanoparticles although huge difference in the density of nanoparticles and fluid. For example, nanofluids have anomalously high thermal conductivities at very low fraction, strongly temperature-dependent and size-dependent conductivities, and three-fold higher critical heat flux than that of base fluids. Traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain why nanofluids have these intriguing features. So in this paper, we devise a theoretical model that accounts for the fundamental role of dynamic nanoparticles in nanofluids. The proposed model not only captures the concentration and temperature-dependent conductivity, but also predicts strongly size-dependent conductivity. Furthermore, we physically explain the new phenomena for nanofluids. In addition, based on a proposed model, the effects of various parameters such as the ratio of thermal conductivity of nanofluids to that of a base fluid, volume fraction, nanoparticle size, and temperature on the thermal conductivities of nanofluids are investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.406-409
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• 2001

The conductivity properties and synthesis of LaNiO$_3$ ceramics from La$\sub$1+$\delta$/NiO$_3$($\delta$=--0.06, 0, 0.06) were investigated. A single perovskite phase was realized at 800$^{\circ}C$. La$_2$NiO$_4$ and other unexpected oxide were observed at 1000$^{\circ}C$. The Microstructure was showed clearly that it is a low density porous material. LaNiO$_3$ ceramic showed a metallic conductivity. The conductivity of La rich samples had a higher value than the La poor samples.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.349-355
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• 2002

The ionic conductivity of cubic solid solutions in the systems of CaO-$ZrO_2$, $Y_2O_3-ZrO_2$ prepared by SHS was examined. The higher conductivity appears to be related to a lower activation energy rather than to the number of oxygen vacancies dictated by composition. Conductivity-temperature data was obtained at 1000 $^{\circ}C$ in atmosphere of low oxygen partial pressure (~$10^{-40}$ atm) for $Y_2O_3-ZrO_2$ cubic solid solutions. The data indicated that these materials could be reduced, and the decree of reduction would be related with the measuring electric field.

• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.77-82
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• 1999

In this paper, physical properties and electrical conductivity of electron beam irradiated low density polyethylene are studied. The specimens of thickness 100 $\mu\textrm{m}$ irradiated as each 1 Mrad, 2 Mrad, 4 Mrad, 8 Mrad, 16 Mrad and virgin are used in this experiment. FTIR analysis shows strong absorptions by methyl groups in wavenumbers 720 $cm^{-1}$ and 1463 $cm^{-1}$, and did not show any evidences of the presence of residual carbonyl groups. From the DSC analysis, the crystalline melting point of electron beam irradiated specimen is lower than that of virgin specimen. 1 Mrad irradiated sample shows the stable electrical conductivity characteristics with both temperature and electric field.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.527-530
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• 2015

The electrical properties of nanostructured Gd-doped $CeO_2$ (n-GDC) as a function of temperature and water partial-pressure were investigated using ac and dc measurements. For n-GDC, protonic conductivity prevails under wet condition and at low temperatures (< $200^{\circ}C$), while oxygen ionic conductivity occurs at high temperatures (> $200^{\circ}C$) under both dry and wet conditions. The grain boundaries in n-GDC were highly selective, being conductive for protonic transport but resistive for oxygen ionic transport. The protonic conductivity reaches about $4{\times}10^{-7}S/cm$ at room temperature (RT).

• Journal of Mechanical Science and Technology
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• v.19 no.10
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• pp.1932-1938
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• 2005

Graphite foams consist of a network of interconnected graphite ligaments and are beginning to be applied to thermal management of electronics. The thermal conductivity of the bulk graphite foam is similar to aluminum, but graphite foam has one-fifth the density of aluminum. This combination of high thermal conductivity and low density results in a specific thermal conductivity about five times higher than that of aluminum, allowing heat to rapidly propagate into the foam. This heat is spread out over the very large surface area within the foam, enabling large amounts of energy to be transferred with relatively low temperature difference. For the purpose of graphite foam thermosyphon design in electronics cooling, various effects such as graphite foam geometry, sub-cooling, working fluid effect, and liquid level were investigated in this study. The best thermal performance was achieved with the large graphite foam, working fluid with the lowest boiling point, a liquid level with the exact height of the graphite foam, and at the lowest sub-cooling temperature.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.310-315
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• 2000

We analyzed thermal stress of the STS VOD ladle by the variation of material property of refractory, and determined the location of back filler using FE analysis. Thermal distribution of refractory of ladle between hot face and back face were decreased by the increasing the thermal conductivity, and thermal stress of refractory were decreased about 2 to 4 times with the decreasing the young's modulus coefficients. Back filler, which is constructed to absorb the thermal expansion of dolomite refractory, has relatively low thermal conductivity. Inner side of refractory of ladle maintained high temperature, but temperature of outer side of ladle decreased low. Consequently, inner expansion and outer contraction were appeared. and thermal stress were increased, so thermal stress by the construction of back filler were increased.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.40-43
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• 2008

High temperature polymer electrolyte membranes incorporating ionic liquids (ILs) in different polymers such as commercial fluorinated polymers, sulfonated polymers and recasted nafion have been developed. ILs based on imidazolium cation and different anions possess high ionic conductivity and good thermal stability and have been used in the present study. The membranes containing IL show conductivity ${\sim}10^{-2}S\;cm^{-1}$ above $100^{\circ}C$ under anhydrous conditions and are thermally stable up to $250-300^{\circ}C$. IL acts as a conducting medium in these electrolytes and plays the same role as played by water in fully hydrated nafion membranes. Due to high conductivity and good thermal stability, these membranes are promising materials for PEFCs at higher temperatures under anhydrous conditions.

• Proceedings of the Safety Management and Science Conference
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• 2002.11a
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• pp.273-277
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• 2002

In the electrode fabrication of unit cell, we found that optimal the electrochemical characteristics were obtained with at 90 wt.% of activated carbon(BP-20), 5 wt.% of conducting agent(Ppy, Super P) and 5 wt.% of P(VdF-co-HFP)/PVP mixed binder. The electrochemical characteristics of unit cell with Ppy improver were as follows : 37.6 F/g of specific capacitance, 0.98 $\Omega$ of AC-ESR, 2.92 Wh/kg and 6.05 Wh/L of energy density, and 754 W/kg and 1,562 W/L of power density. It was confirmed that internal resistance were reduced due to the increase of electrical conductivity and filling density by the introduction of conductivity agent, and content of conducting agent was suitable in the range of 4~6 wt.%. According to the impedance measurement of the electrode with conductivity agent, we found that it was possible to charge rapidly by the fast steady-state current convergence due to low equivalent series resistance(AC-ESR), fast charge transfer rate at interface between electrode and electrolyte, and low RC time constant.