• 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.

• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.75-88
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• 1999

A recent major subject of geophysical exploration is research into 3-D subsurface imaging with a composite information from the various geophysical data. In an attempt to interpret Schlumberger sounding data for the study area in 2-D and 3-D view, resistivity imaging was firstly performed and then pseudo-3-D resistivity volume was reconstructed by interpolating several 1-D resistivity plots. Electrical resistivity discontinuities such as fracture zone were successfully clarified in pseudo-3-D resistivity volume. The low resistivity zone mainly associated with fracture zone appears to develop down to granitic basement in the central part of the study area. Seismic velocity near the lineament is estimated to be approximately as small as 3,000 m/s, and weathering-layer for the southeastern part is interpreted to be deeper than for the northwestern part. Geophysical attributes such as electrical resistivity, seismic velocity, radioactivity for the Chojeong Area were analysed by utilizing a GIS software Arc/Info. The major fault boundaries and fracture zones were resolved through image enhancement of composite section (electrical resistivity and seismic refraction data) and were interpreted to develop in the southeastern part of the area, as characterized by low electrical resistivity and low seismic velocity. However, radioactivity attribute was found to be less sensitive to geological discontinuities, compared to resistivity and seismic velocity attributes.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.267-270
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• 2006

The Indium tin oxide (ITO) films were deposited on CR39 substrate using DC magnetron sputtering. ITO thin films deposited at room temperature because CR39 substrates its glass-transition temperature of is $130^{\circ}C$. ITO thin films used bottom and top electrode and for organic thin film transparent transistor.(OTFT) ITO thin film electrodes electrical properties and optical transparency properties in the visible wavelength range (300 - 800 nm) strongly dependent on volume of oxygen percent. For the optimum resistivity and transparency of ITO thin film electrode achieved with a 75 W plasma power, 10 % volume of oxygen and a 27 nm/min deposition rate. Above 85 % transparency in the visible wavelength range (300 - 800 nm) measured without post annealing process and $9.83{times}10{-4}{\Omega}cm$ a low resistivity was measured thickness of 300 nm.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.217-223
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• 1995

In this paper, we investigated physical properties and electrical characteristics of the fluorocarbon that used as coolants for large power gas-insulated transformer. Volume resistivity of the fluorocarbon was .rho.=1.87*10$^{15}$ [.ohm.cm] at 1 atm, 27.deg. C. Dielectric constant was 1.86 and decreases as temperature increase. The breakdown voltage at 1 atm was higher than that of transformer oil. The breakdown voltage of fluorocarbon vapor was about 18kV when pressure in a test chamber increases over lkg/cm$^{2}$. When fluorocarbon was mixed with SF$_{6}$ gas, breakdown voltage of the mixed was higher than that of fluorocarbon. Then fluorocarbon leads to increase over 4kg/cm$^{2}$ in pressure as temperature increase. Therefore, when a gas-insulated transformer is manufactured, the design must be taken into consideration a high-pressure.

• Electrical & Electronic Materials
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• v.10 no.8
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• pp.756-762
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• 1997

In this paper the change of electrical properties of transformer oil due to electron beam irradiation is investigated. The specimens are produced with a some different dose of 0.5[Mrad], 1[Mrad] and 2[Mard] except for original specimen. The physical properties of each specimen is analyzed by using the FT-IR spectrum. So it is confirmed that carbonyl groups are increased according to the increase of electron beam dose and also that the nitric compounds are disappeared. The magnitude of dielectric dissipation factor appears maximum value by the contribution of dipoles and ions in the low temperature low voltage region and it is stable due to the saturation of carriers in the high temperature high voltage region in the electric conduction characteristics. Volume resistivity is also measured one of original specimen is larger than irradiated specimen.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.61-63
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• 1988

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.24-30
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• 2010

The void ratio and elastic moduli are design parameters used in geotechnical engineering to understand soil behavior. Elastic and electromagnetic waves have been used to evaluate the various soil characteristics due to high resolution. The objective of this study is to evaluate the void ratio and elastic moduli based on elastic wave velocities and electrical resistivity. The Field Velocity Resistivity Probe (FVRP) is developed to obtain the elastic and electromagnetic wave profiles of soil during penetration. The Piezoelectric Disk Elements (PDE) and Bender Elements (BE) are used as transducers for measuring the elastic wave velocities such as compressional and shear wave velocities. The Electrical Resistivity Probe (ERP) is also installed for capturing the electrical resistivity profile. The application test is carried out on the southern coast of the Korean peninsula. The field tests are performed at a depth of 6~20 m, at 10 cm intervals for measuring elastic wave velocities and at 0.5cm intervals for measuring electrical resistivity. The elastic moduli such as constraint and shear moduli are calculated by using measured elastic wave velocities. The void ratios are also evaluated based on the elastic wave velocities and the electrical resistivity. Furthermore, the converted void ratios by using FVRP are compared with the volumetric void ratio obtained by a standard consolidation test. The comparison shows that the void ratios based on the FVPR match the volume based void ratio well. This study suggests that the FVRP may be a useful device to effectively determine the elastic moduli and void ratio in the field.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1447-1448
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• 2011

The CSPE cables are used for three years in nuclear power plant. The accelerated thermal aging of chloro sulfonate polyethylene(CSPE) jacket of test cables were carried out for the period equal to 10, 20 and 30 years in air at 90 and $100^{\circ}C$, respectively. The electrical volume resistivity, density, XPS, FE-SEM, EDS and XRF of the accelerated thermal aging of CSPE were measured. The validation of condition monitering method of accelerated thermal aging CSPE was estimated by them. The best validation of condition monitoring method of accelerated aging CSPE is electrical volume resistivity because change thermal of the specimen showed distinction.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.382-385
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• 1995

Electrical properties such as tracking resistance, dielectric constant, $tan\delta$, and volume resistivity, and mechanical properties such as tensile, and strength, and % elongation were measured with the alumina trihydrate filled with EPDM. The results were dicussed in terms of the effect of hydroxyl group. The test results show that the tracking resistance of EPDM improves with the increase in ATH content, whereas volume resistivity, dielectric constant, $tan\delta$ decrease wi th increasing ATH content due to polar nature of ATH. In the charge accumulation characteristics, the homocharge is formed in pure EPDM, and as the ATH content increases in the EPDM compound, the amount of homocharge decrease.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.86-92
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• 2000

Recently, more advanced electronic elements become, they consume powerful and radiate more heat in devices. So the most suitable packaging technique is keenly needed. The most important purpose of packaging is to protect devices within a system for a long time and to prevent life of devices from external environments; floating ions such as humidity or sodium, and exposure from ultraviolet rays. In order to study the electrical properties of silicone gels often used as packing material due to the curing condition, volume resistivity and AC breakdown experiment are performed. Specimens are made up at several cured times and temperatures condition ; 0.5[H], 1[H] and 2[H] at 100[$^{\circ}C$], 125[$^{\circ}C$], 150[$^{\circ}C$], 160[$^{\circ}C$], 170[$^{\circ}C$] and 180[$^{\circ}C$]. It is confirmed that from volume resistivity experiment liquid silicone become get state at 90~100 [$^{\circ}C$] and cured specimen for 1~2[H] at 170[$^{\circ}C$] are superior in electrical properties.