• International Journal of Highway Engineering
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• v.15 no.2
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• pp.29-37
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• 2013

PURPOSES : This study aims to review the possibility of developing a road snow-melting system that can prevent slip accidents by maintaining a constant temperature of the winter roads and enhance performance of structures, including improvement of compressive strength by mixing carbon nanotube (hereafter referred to as CNT) with cement paste, the basic material. METHODS : To achieve the above purpose, an experiment was conducted by mixing power-type CNT and wrap-type CNT up to cement paste formulation by weight of 0.0wt%~4.1wt% in accordance with "KS L ISO 679(of cement strength test method)", and compressive strength was measured at 28 days of curing. In addition, the volume resistivity of the specimen was measured to test thermal and electrical characteristics, and the rate of temperature changes in specimen surface by power consumption was measured by passing electricity through the cross-sections of the specimen. Meanwhile, the criteria for checking the performance as a road snow-melting system was determined as volume resistivity of $100{\Omega}{\cdot}cm$ or less. RESULTS : A comparative analysis between specimen with 0wt% CNT content in plain status and specimen containing various types of CNTs was carried out. From its results, it was found that compressive strength increased approximately 19%, showing the highest rate when 0.2wt% of wrap-type CNT was contained, but volume resistivity of $100{\Omega}{\cdot}cm$ or less appeared only in specimens containing more than 0.2wt% CNT. In addition, it was observed that the surface temperature increased by $4.62^{\circ}C$ per minute on average in specimens containing 3.2wt% CNT. CONCLUSIONS : In this study, CNT was examined as an underlying material for a road snow-melting system, and the possibility of developing the road now-melting system was reviewed by conducting various experiments using CNT-Cement composites. From the experimental results, the specimens were found to have a superior performance when compared to the existing road snow-melting systems that place the heat transfer medium such as copper on the road. However, satisfactory strength performance were not obtained from the specimen containing CNT(2.0% or more) that functions as a heating element, which leads to the need for reviewing methods to increase the strength by using plasticizer or admixture.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1244-1249
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• 2002

In this study, the physical characteristics of steel-wire sound absorbing materials with different thickness and bulk density is experimentally obtained in terms of the porosity and specific flow resistivity. Based on the experimental results, the following conclusions can be made. The porosities of steel-wire sound absorbing materials are smaller than those of general absorbing materials, which are inversely proportional to the volume densities. For the porosity measurement with a good accuracy, the dynamic correction based on the system compliance should be involved in porosity measurement. In addition, the flow condition for the precise measurement of the specific flow resistivity of steel-wire sound absorbing materials should be limited in the laminar flow region.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3C
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• pp.127-136
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• 2009

The objective of this study is the development and verification of the 4-electrode resistivity probe (4ERP) for the estimation of electrical properties of the saturated soils. The 4ERPs with wedge and plane types are manufactured to obtain the electrical resistivity without polarization at the electrodes by using Wenner array. The wedge type is for the penetration into the soil samples and the plane type is for the installation into the cells used for the laboratory tests. The consolidation tests are carried out by using 6 types of glass beads and 3 types of sands in size. The test results show that the electrical resistivity increases with a decrease in the porosity, and the constant m used in Archie's law is dependent on the particle shape rather particle size. The one dimensional liquefaction tests show that the porosity obtained by the 4ERP is similar to that determined by the volume fraction. The penetration of the 4ERP into the large scale calibration chamber produces the resistivity profiles. This study demonstrates that the 4ERP may effectively estimate the porosity of the saturated soils.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.423-431
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• 2008

In general, water-saturated silt or clay alluvium is characterized with relatively low-resistivity. Thus we often encountered the problem that such a low-resistivity layer is misguided to be good aquifer of high-permeability and low-resistivity in the development of groundwater. This research was conducted with an emphasis on the identification of saturated silt or clay layer from the aquifer by performing the laboratory experiment of IP and resistivity methods on the various materials consisting of alluvium aquifer. Silt or clay layer is found to be characterized with the higher chargeability zone, compared to the sand layer. Regarding the mixture of sand and clay, the higher clay volume, the lower resistivity and the higher chargeability. Subsequently chargeability decreases.

• Elastomers and Composites
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• v.38 no.3
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• pp.235-242
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• 2003

A vulcanization reaction characteristics of an isoprene rubber (IR)-modified natural rubber/carbon black (NR/CB) composite was studied using in-situ electrical property measuring technique. Since the electrical conductivity of the sample composite would be changed continuously during the vulcanization reaction by rearranging of the carbon black particles within the sample, volume resistivity (${\rho}$) might be obtained as a function or reaction time. A stabilization time ($t_i$), maximum reaction speed time ($t_p$), and volume resistivity at that time(${\rho}_p$) were defined from the data for the Arrhenius analysis. Volume resistivity ${\rho}$ showed a comparatively high value of ${\sim}10^8$ order before the reaction started, and dramatically decreased to be stabilized within $1{\sim}2$ minutes as soon as the reaction started. As the more time elapsed, thereafter, ${\rho}$ decreased monotonously to a certain constant value through a peak, ${\rho}_p$ at time $t_p$, which was considered as the maximum reaction rate. As a result, while $t_i$ values were comparatively constant as $1{\sim}2$ minutes, $t_p$ values showed to become shorter and shorter as the reaction temperature.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.383-389
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• 2003

Clay minerals show a distinct induced-polarization phenomenon, which is one of the most important factors for predicting groundwater flow and contaminant transport. This paper presents a step-by-step process to estimate Cole-Cole parameters from spectral induced-polarization (IP) data measured on the surface of three-dimensional earth. First, the inversion of low-frequency resistivity survey data is made to identify the dc resistivity ${\rho}_dc$ of a volume having IP effects. The other parameters, chargeability m, time constant $\tau$, and frequency dependence c, are sought for the polarizable volume. Next, using multi-frequency data, c can be obtained as high or low asymptotes of the slope of log phase vs. log frequency. Further, for low m, intrinsic $\tau$ is approximated by apparent one, ${\tau}_a$, which is derived from the relation ${{\omega}{\tau}}_a$=1 at an angular frequency $\omega$, where the imaginary component of spectral IP data has an extreme value. Finally, to obtain intrinsic m a two-step linearized procedure has been derived. For a body of given $\tau$ and c, forward modeling with a progression of m values yields a plot of observed vs. intrinsic imaginary components for a frequency. Since this plot is essentially linear, to extract the intrinsic imaginary component is quite simple with an observed value. Using the plot of intrinsic imaginary component vs. m, intrinsic m is determined. We present a synthetic example to illustrate that the Cole-Cole parameters can be recovered from spectral IP data.

• Carbon letters
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• v.13 no.4
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• pp.230-235
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• 2012

In this study, reduced graphene oxide/polyimide (r-GO/PI) composite films, which showed significant enhancement in their electrical conductivity, were successfully fabricated. GO was prepared from graphite using a modified Hummers method. The GO was used as a nanofiller material for the preparation of r-GO/PI composites by in-situ polymerization. An addition of 20 wt% of GO led to a significant decrease in the volume resistivity of composite films by less than nine orders of magnitude compared to that of pure PI films due to the electrical percolation networks of reduced GO created during imidization within the films. A tensile test indicated that the Young's modulus of the r-GO/PI composite film containing 20 wt% GO increased drastically from 2.3 GPa to 4.4 GPa, which was an improvement of approximately 84% compared to that of pure PI film. In addition, the corresponding tensile strength was found to have decreased only by 12%, from 113 MPa to 99 MPa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.510-513
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• 2003

In this paper, we have investigated the physical, dielectric and electrical conduction properties of polyethylene terephthalate(PET) film due to temperature variation. From FT-IR spectrum as an analysis of physical properties, the strong absorption in wavenumber 1019[$cm^{-1}$], 1266[$cm^{-1}$], and 1752[$cm^{-1}$] observed by the C=O and benzene ring. the characteristics of volume resistivity used to highmegohm meter is measured from 1 to 10 minutes when the specimen applied the voltage according to the step voltage appling method. and dielectric characteristics were measured in the temperature range from room temperature to 120[$^{\circ}C$] due to frequency variation.. also we measured in the voltage rang of 1[V] to 20[V] according to the voltage application method.

• Transactions on Electrical and Electronic Materials
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• v.1 no.4
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• pp.25-29
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• 2000

In this paper, PET(Ployethylene Terephthalate) films with semiconducting and interface layers were investigated, The electrical properties, such as volume resistivity, tan$\delta$(dissipation factor) and breakdown strength at various temperatures were measured. Thermal analysis of PET and semiconducting films were measured and compared by differential scanning calorimeter(DSC) of each film. It is found that the volume resistivity of films(dependence on semiconducting interface layers)and electrical properties of PET films are changed ,Breakdown strength and dissipation factor of PET films with semiconducting layer (PET/S/PET) are decreased more greatly than PET and PET/PET films, due to the increase of charge density of charges at two contacted interfaces between PET and semiconductor, The dissipation factor of each films in increased with temperature,. For PET/S/PET film, is depended on temperature more than PET of PET/PET. However, the breakdown strength is increased up to 85$\^{C}$ and then decreased over 100$\^{C}$The electrical properties of PET films with semiconducting/interface layer are worse than without it It is due to a result of temperature dependency, which deeply affects thermal resistance property of PET film more than semiconducting/interface layers.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.193-195
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• 1996

Low-density polyethylene(LDPE ; thickness 100[${\mu}m$] as a experimental specimen is irradiated with electron beam by using electron beam accelerator, and as an experimental specimen, the nonirradiated specimen and the specimen irradiated with electron beam is produced according to the classification of dose. From the analysis of DSC, the crystalline melting point of the specimen irradiated with electron beam is lower than that of virgin specimen. It is confirmed thai the volume resistivity is increased from the temperature over $50[^{\circ}C]{\sim}60[^{\circ}C]$ to the crystalline melting point because of the defects of solid structure and the formation of many trap centers by means of electron beam irradiation, but decreased in the temperature over the crystalline melting point because of the melt of crystalline.