• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.991-993
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• 1999

The method of measurement for contactless eddy-current conductivity using magnetic dipole field theory was suggested by M.C Chen[1], which calculate the eddy-current caused by exciting coil with Faraday's induction law. In this work, we have developed the apparatus for contactless measurement of conductivity or resistivity with the dipole field theory. The resistivity can be measured from several to a dozen $m{\Omega}{\cdot}cm$ range within maximum 30% error. At the high resistivity range above $100{\Omega}{\cdot}cm$, the standard deviation of measurement was very large as the induced voltage of sensing coil is small so it was difficult to measure the value precisely.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.10
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• pp.792-795
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• 2001

we present a electrical transport(resistivity, Hall effect) measurements in varying temperature ranges between 78K and 300K on HoSi$_2$ composites by hot-pressed sintering. It has been found that this sintered HoSi$_2$ has a orthorhombic structure, and lattices constant is a=9.8545$\AA$, b=7.7935$\AA$, c=7.8071$\AA$. The measured electrical resistivity is about 1.608$\Omega$ cm and carrier mobility is about 6.9$\times$10$^{1}$cm $^{2}$V.sec at low room temperature. The Hall effect shows a n-type conductivity in the sintered HoSi$_2$.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1529-1535
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• 1994

Electrical conduction mechanisms of RuO2-based thick film resistors were investigated with frequency depandence on AC conductivity. Electrical conduction mechanisms of lower resistivity system (100{{{{ OMEGA }}/sq) sintered at 600~90$0^{\circ}C$ were all metallic conduction mechanism. In case of higher resistivity (10K{{{{ OMEGA }}/sq) system, the electrical conduction mechanisms were very depenent on sintering temperature. When sintering temperature was $600^{\circ}C$, the electrical conduction mechamism was ionic, and as increasing the sintering temperature, the electrical conduction mechanism was changed from ionic to hopping conduction mechanism.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.119-124
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• 2015

This paper investigates the change of the percolation threshold in the carbon powder-filled polystyrene matrix composites based on the experimental results of changes in the resistivity and relative permittivity of the carbon powder filling, the electric field dependence of the current, and the critical exponent of conductivity. In this research, the percolation behavior, the critical exponent of resistivity, and electrical conduction mechanism of the carbon powder-filled polystyrene matrix composites are discussed based on a study of the overall change in the resistivity. It was found that the formation of infinite clusters is interrupted by a tunneling gap in the volume fraction of the carbon powder filling, where the change in the resistivity is extremely large. In addition, it was found that the critical exponent of conductivity for the universal law of conductivity is satisfied if the percolation threshold is estimated at the volume fraction of carbon powder where non-ohmic current behavior becomes ohmic. It was considered that the mechanism for changing the gaps between the carbon powder aggregates into ohmic contacts is identical to that of the connecting conducting phases above the percolation threshold in a random resister network system. The electric field dependence is discussed with a tunneling mechanism. It is concluded that the percolation threshold should be defined at this volume fraction (the second transition of resistivity for the carbon powder-filled polystyrene matrix composites) of carbon powder.

• Geophysics and Geophysical Exploration
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• v.7 no.3
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• pp.184-190
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• 2004

To analyze soil properties of unsaturated zone, we applied electrical resistivity tomography(ERT) of high resolution image. From linear relationship with each soil texture between results of ERT and soil properties such as electrical conductivity of pore water, water contents and ionic contents, we could be analyzed the result of ERT more effectively. Consequently, ERT can be useful for estimating soil properties between the two holes and evaluating indirectly pH and organic contents of soil.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.316-316
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• 2014

Two different transparent conducting oxide (TCO) layers of Al-doped ZnO (AZO) and $WO_3$ were prepared by a rf sputtering process. Working pressure, deposition time, and target-to-substrate distance were varied for the sputtering process to improve electrical properties of the resulting layer. Thickness of the TCO layers was measured by a profile meter of ${\alpha}$-step. To evaluate the electrical conductivity, surface resistivity of the TCO layers was measured by a four-point probe technique. Decrease of the working pressure resulted in increase of deposition rate and decrease of surface resistivity of the resulting layer. Increase of the layer thickness due to increased deposition time resulted in decrease of surface resistivity of the resulting layer. The shorter the target-to-substrate distance was, the lower was the surface resistivity of the resulting layer.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.432-435
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• 2006

To evaluate geology and extent of leachate migration around the landfills, electrical resistivity survey were conducted in area of uncontrolled landfills in Cheonan and Wonju. The Cheonan landfill is located above the paddy fields and the resistivity survey lines were crossed to confirm possible pollution of the paddy fields by leakage of the landfill leachate. In Wonju, the landfill and the downgradient paddy fields are divided by a concrete barrier wall. At the bottom of the landfill, there is a leachate settlement system but has not been in operation. And a total of 4 survey line installed (1 parallel and 3 perpendicular to mean groundwater flow direction). According to the resistivity survey results, the landfill leachate in Cheonan appeared to be restricted only within the interior of the landfill, not to migrate into the subsurface of the paddy fields. These results are well consistent with electrical conductivity values of groundwaters obtained from a periodic analysis of water qualities. In Wonju, however, it was inferred that the leachate emanating from the landfill migrated beneath the abandoned leachate settlement system and it would reach the downgradient paddy field.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.6-10
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• 2013

We investigate the electrical and thermal transport properties of a sesquicarbide superconductor $La_2C_3$, including electrical resistivity, thermoelectric power, and thermal conductivity. The electrical resistivity exhibits a typical metallic character with a saturation behavior at high temperatures. The thermoelectric power shows a metallic behavior with pronounced phonon-drag effect, comparable with pure metals. The broad peak of the thermal conductivity is observed in the superconducting state, which is rapidly suppressed by magnetic fields. These observations suggest that the electron-phonon scattering is significant in $La_2C_3$, which is relevant with the relatively high-$T_c$ in $La_2C_3$ through strong electron-phonon coupling with low frequency phonon modes.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.2
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• pp.104-108
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• 1999

The electrical conductive mechanism and temperature dependence of electrical resistivity of $\alpha-SiC-ZrB_2$ composites with $ZrB_2$ contents were investigated. The electrical resistivity of hot-pressed composites was measured by the Pauw method form $25^{\circ} to 700^{\circ}C$. The electrical resistivity of the composites follow the electrical conduction model for a homogeneous mixture of two kind of particles with different conductivity. Also, the electrical resistivity versus temperature curves indicate the formation of local chains of $ZrB_2$ particles. In case of $\alpha-SiC-ZrB_2$ composites containing above 39vol.% $ZrB_2$ showed positive temperature coefficient resistance(PTCR), whereas the electrical resistivity of $\alpha-SiC-21vol.% ZrB_2$ showed negative temperature coefficient resistance(NTCR).

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.4
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• pp.157-160
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• 2007

The van der Pauw technique is one of the popular methods for determining the conductivity of flat metal samples. Traceability of the national standard for the conductivity has been achieved by direct current measurement techniques in national measurement institutes of many countries. But recently, alternative current measurement techniques for determining the conductivity of flat metal samples is also interested. In this study, we measured the conductivity of non-ferrous and ferrous flat metals at alternative current using van der Pauw technique. As measurement results, the conductivities of the samples were decreased according to increasing the test frequency even though the decreasing ratio was different.