• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2619-2621
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• 2005

Electrical resistance tomography(ERT) maps resistivity values of the soil subsurface and characterizes buried objects. The characterization includes location, size, and resistivity of buried objects. In this paper, Gauss-Newton and truncated least squares(TLS) are presented for the solution of the ERT image reconstruction. Computer simulations show that the spatial resolution of the reconstructed images by the TLS approach is improved as compared to that obtained by the Gauss-Newton method.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.576-579
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• 2008

Electrical impedance(EIT) for the multi-phase flow visualization is an imaging modality in which the resistivity distribution of the unknown object is estimated based on the known sets of injected currents and measured voltages on the surface of the object. In this paper, an EIT reconstruction algorithm based on the extended Kalman filter(EKF) is proposed. The EIT reconstruction problem is formulated as a dynamic model which is composed of the state equation and the observation equation, and the unknown resistivity distribution is estimated recursively with the aid of the EKF. To verify the reconstruction performance of the proposed algorithm, experiments with simulated multi-phase flow are performed.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.129-136
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• 2005

The groundwater survey was carried out by electrical resistivity and resistivity tomography using several kinds of electrode array to delineate the depth of the saturated zone and basement complex, the aquifer system of fractured rock, and the 2-D resistivity structure was obtained by inversion technique. And the hole-to-surface and crosshole tomography were applied for two boreholes and the inverted resistivity tomogram are obtained. The comparison of those data with core logging data was performed and those results were relatively well correlated. And it was possible to find out the configuration of basement and the fracture zone and the aquifer system from the 2-D resistivity structure and resistivity tomogram.

• Journal of the Korean earth science society
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• v.32 no.6
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• pp.537-547
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• 2011

Electrical resistivity tomography surveys using boreholes were applied to reveal the cause of a catastrophic land subsidence accompanied by the excessive groundwater withdrawal in urban karst area and to map the connectivity of disseminated cavities over the study area. In order to understand the hydrogeological characteristics, resistivity using exsitu core samples, groundwater level for five boreholes, and hydraulic conductivity using slug test were measured. The hydraulic conductivity variation ranging from 0.8 to $9.3{\times}10^{-4}\;cm/s$ for five boreholes and a gentle slope of groundwater level indicated that there is no significant characteristics of hydraulic heterogeneity. Core samples of the lime-silicated rock were classified as three groups including cracked, weathered, and fresh and measured the resistivity values ranged from 103 to 161, 218 to 277, and 597 to 662 ohm-m, respectively. Drilling results that showed the cavity filled with clay materials and tomogram for this region indicated resistivity value lower than 50 ohm-m. From the inverted resistivity results for each section with five boreholes, cavity and fractured layer were distributed along the depth between 10 and 20 m overall area and cavities ranging from 4 to 6 m filled with clay materials.

• Journal of Biomedical Engineering Research
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• v.10 no.2
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• pp.102-105
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• 1989

In electrical impedance tomography(EIT), we use boundary current and voltage measurements toprovide the information about the cross-sectional distribution of electrical impedance or resistivity. One of the major problems in EIT has been the inaccessibility of internal voltage or current data in finding the internal impedance values. We propose a new image reconstruction method using internal current density data measured by NMR. We obtained a two-dimensional current density distribution within a phantom by processing the real and imaginary MR images from a 4.77 NMR machine. We implemented a resistivity mage reconstruction algorithm using the finite element method and sensitivity matrix. We presented computer simulation results of the mage reconstruction algorithm and furture direction of the research.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.3
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• pp.123-128
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• 2004

In electrical impedance tomography (EIT), the internal resistivity distribution of the unknown object is computed using the boundary voltage data induced by different current patterns using various reconstruction algorithms. This paper presents a new image reconstruction algorithm based on the genetic algorithm (GA) via a two-step approach for the solution of the EIT inverse problem, in particular for the reconstruction of "static" images. The computer simulation for the 32 channels synthetic data shows that the spatial resolution of reconstructed images in the proposed scheme is improved compared to that of the modified Newton-Raphson algorithm at the expense of an increased computational burden.rden.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.215-218
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• 2007

Tunnel detection is known to be one of the challenging problems in geophysical society. Among various geophysical methods, we tried to examine the applicability of electrical resistivity tomography (ERT) method to detect empty tunnel. In this study, we analyzed the ERT data acquired at the test site for tunnel detection. The inversion results have shown reasonable image of the tunnel although the resolution is quite poor. Moreover, we could obtain the three-dimensional attitude of tunnel through 3-D ERT imaging. Therefore, we expect that ERT can make contribution to the tunnel detection problem and further research effort such as fusion of geophysical methods will provide more reliable tunnel detection capability.

• 한국지구물리탐사학회:학술대회논문집
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• 1999.08a
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• pp.92-116
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• 1999

Tomographic approaches to image underground structure using electrical properties, can be divided into DC resistivity, electromagnetic, and radar tomography, based on the operating frequency. DC resistivity and radar tomography methods have been recently applied to site investigation for engineering purpose in Korea. This paper review these two tomography methods, through the case histories acquired in Korea. As another method of borehole radar survey, borehole radar reflection method is included, and its inherent problem and solution are discussed, how to find the azimuth angle of reflector using direction-finding-antenna. Since the velocity anisotropy of radar wave has been commonly encountered in field data, anisotropic radar tomography is discussed in this paper. In DC resistivity tomography, two subjects are focussed, electrode arrays, and borehole effect owing to the conductive fluid in borehole. Using the numerical modeling data, various kinds of electrode ways are compared, and borehole effect is illustrated. Most of the case histories presented in this paper are compared with known geology, core logging data, and/or Televiewer images.

• Geophysics and Geophysical Exploration
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• v.7 no.4
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• pp.217-224
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• 2004

Self-potential and electrical resistivity methods were conducted for locating the auriferous mineralized zone, called Jija Vein, of Sambo mine, Limsu-ri, Haeje-myeon, Muahn-gun, Jeollanam-do. The host rocks of the mineralization include gneiss, rhyolite and felsic dyke. Ore vein is mainly fissured-filling type and sulfide minerals, such as pyrite, are disseminated in country rock. By the electrical responses from SP and surface resistivity methods., the mineralized zone is supposed to extend about 360 m directed N5W with the width of 20 m to 30 m. From resistivity tomograms using inclined borehole to surface, the ore body shape is interpreted as the width of 20 m in depth 40 m to 50 m.

• Geophysics and Geophysical Exploration
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• v.19 no.2
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• pp.59-66
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• 2016

The electrical resistivity method is an effective geophysical tool to detect subsurface contamination because the contaminated zones show generally lower electrical resistivity. In this study, the electrical resistivity surveys were applied to a waste landfill site to image the subsurface structure around the landfill and to identify the contaminated zones. First, the dipole-dipole 2D resistivity surveys were conducted along the boundaries of landfill to define the developed contaminated zones. Then the crosshole resistivity tomography was applied to confirm the suspected contaminated zones at depth. The results of drilling and geochemical analysis of ground water supported that the low resistivity zones coincide well with the contaminated zones and the leachate pathways could be delineated effectively from the resistivity survey.