• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1237-1239
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• 2005

In this study, we estimate the thermal conductivity of stainless steel reinforced Bi-2223/Ag tape which was made from American Superconductor. The equipments for thermal conductivity measurement was set up using conduction cooled cryocooler. Two direction of thermal conductivity was measured. The one is the direction of cut length, and the other is direction of transverse of wounded coil with insulation material. It was observed that the thermal conductivity of transverse direction of coil was extremely lower than that of cut length direction. It was mainly seems that superconducting filaments and insulation material were effected on thermal conductivity in thermal conductivity of transverse direction.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.25.2-25.2
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• 2005

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.26.2-26.2
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• 2005

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.22-24
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• 1995

The electrical conductivity of TiO$_2$doped ZnO was investigated by means of complex impedance measurement and voltage-current source and meaurement unit. The e1ectrical conductivity of TiO$_2$added ZnO was increased with increasing the concentration of TiO$_2$. The calculated relative dielectric constant was decreased with increasing the concentration of TiO$_2$. The increase of electrical conductivity seems to be the effect of TiO$_2$donor doping.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.447-450
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• 1997

Temperature distribution measurements in the mockup apparatus of reactor vessel were performed to determine the effective thermal conductivity of Al powder porous media where stainless steel tubes were installed with different geometry. The temperature distributions at four separated sections with different arrangements of porous media have different slopes according to the geometrical configuration. From the measured temperature distribution, effective thermal conductivity have been derived using the least square fitting method.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.45-52
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• 2013

PURPOSES : This study is to construct the regression models of drainage asphalt concrete specimens and to provide the appropriate coefficients of hydraulic conductivity prediction models. METHODS: In terms of easy calculation of the hydraulic conductivity from porosity of asphalt concrete pavement, the estimation model of hydraulic conductivity was proposed using regression analysis. 10 specimens of drainage asphalt concrete pavement were made for measurement of the hydraulic conductivity. Hydraulic conductivity model proposed in this study was calculated by empirical model based on porosity and the grain size. In this study, it shows the compared results from permeability measured test and empirical equation, and the suitability of proposed model, using regression analysis. RESULTS: As the result of the regression analysis, the hydraulic conductivity calculated from the proposal model was similar to that resulted from permeability measured test. Also result of RMSE (Root Mean Square Error) analysis, a proposed regression model is resulted in more accurate model. CONCLUSIONS: The proposed model can be used in case of estimating the hydraulic conductivity at drainage asphalt concrete pavements in fields.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.311-319
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• 1999

The thermal conductivity ${\lambda}_b$, thermal diffusivity ${\alpha}_b$ of the thin black paint layer sprayed on solid surface and absorptivity a for laser beam are measured by applying a non-contact measurement method of the thermophysical properties of solids. The values of a=0.67, ${\lambda}_b=1.45W/mK$ and ${\alpha}_b=1.24{\times}10^{-6}m^2/s$ are obtained for the sprayed lay~ thickness $z_b{\fallingdotseq}40\;{\mu}m$. Furthermore, for the $z_b{\fallingdotseq}24\;{\mu}m$ thick layers which arc formed by rubbing with a glass rod after spraying, the values of a=0.73, ${\lambda}_b=1.85W/mK$. and ${\alpha}_b=1.09{\times}10^{-6}m^2/s$ are obtained. It is also shown that the present thermal diffusivity ${\alpha}_b$ for $z_b{\fallingdotseq}40\;{\mu}m$ Is about 30~80% larger than those obtained by Araki et al. for the thicker layer $z_b{\fallingdotseq}150{\sim}248\;{\mu}m$. This method could be applied to the measurement of thermophysical properties of thin layer on solids.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.3
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• pp.89-96
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• 2005

To improve the mean-life and reliability of power cables, we have investigated the volume resistivity and thermal properties demonstrated by changing the content of carbon black, an additive of the semiconductive shield for underground power transmission. Nine specimens were made of sheet form for measurement. Volume resistivity of the specimens was measured by a volume resistivity meter after 10 minutes in a preheated oven at temperatures of both 25$\pm$1[$^{\circ}C$] and 90$\pm$ 1[$^{\circ}C$]. As well, specific heat (Cp) and thermal conductivity were measured by Nano Flash Diffusivity and DSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from 0[$^{\circ}C$] to 200[$^{\circ}C$], and heating temperature was 4[$^{\circ}C$/min]. From these experimental results, volume resistivity was high according to an increase of the content of carbon black. Specific heat was decreased, while thermal conductivity was increased according to a rise in the content of carbon black. Furthermore, both specific heat and thermal conductivity were increased by heating temperature because the volume of materials was expanded according to a rise in temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.10
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• pp.825-829
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• 2015

Theoretical calculations suggest that the thermoelectric figure of merit (ZT) can be improved by introducing a core-shell heterostructure to a semiconductor nanowire because of the reduced thermal conductivity of the nanowire. To experimentally verify the decrease in thermal conductivity in core-shell nanowires, the thermal conductivity of Ge-SixGe1-x core-shell nanowires grown by chemical vapor deposition (CVD) was measured using suspended microdevices. The silicon composition (Xsi) in the shells was measured to be about 0.65, and the remainder of the germanium in the shells was shown to play a role in decreasing defects originating from the lattice mismatch between the cores and shells. In addition to the standard four-point current- voltage (I-V) measurement, the measurement configuration based on the Wheatstone bridge was attempted to enhance the measurement sensitivity. The measured thermal conductivity values are in the range of 9-13 W/mK at room temperature and are lower by approximately 30 than that of a germanium nanowire with a comparable diameter.

• Journal of the Korean Ceramic Society
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• v.44 no.2 s.297
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• pp.116-123
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• 2007

Electrical properties of AlN ceramics sintered with 1 wt% $Y_2O_3$ have been investigated. From the impedance spectroscopy, electrical conductivity of grain boundary was found to be much lower than that of grain. DC conductivity measurement showed the electrode polarization effects caused by blocking electrode. The heat-treatment at $1700^{\circ}C$ of the specimen sintered at $1850^{\circ}C$ transformed continuous pain boundary phases along triple boundary junctions into isolated particles in grain comers. The heat-treatment induced decreases both in grain and grain boundary conductivity, and in DC electrical conductivities. From the analysis on the transference number, ionic conductivity was shown to be more dominant than electron conductivity, which was due to ion compensation mechanism during oxygen incorporation into grain.