• Journal of the Korean Society of Groundwater Environment
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• v.2 no.2
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• pp.78-84
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• 1995

In 1983, 83 Wenner vertical electrical sounding(VES)s and 22 pumping tests had been carried out by Korea Agricultural Development Corporation(KADC) in Guam Myun, Yeoju Gun, Kyounggi Province. Also, 10 boreholes had been constructed in the area. Using these data electrical and hydraulic properties of aquifer in the Ganam area are investigated in this study. Assuming that the underground is 1-D, VES data are analyzed. Data analysis shows that the subsurface of study area can be interpreted as 4-layer structure and the 3rd layer which is regarded as aquifer has mean thickness of 10 m and mean resistivity of 506 ohm-m and rests on resistive bedrock. Under the circumstances, as most part of electric current flows parallel to the bedding, longitudinal unit conductance is an important parameter controlling VES curves and very closely correlates with transmissivity of aquifer in the study area. Thus, relation between longitudinal unit conductance and transmissivity is investigated in this study. Since resistivity and thickness of each layer are obtained from interpretation of VES data, the relations between transmissivity and resistivity, and between hydraulic conductivity and resistivity are also studied. Studies of such relations show that longitudinal conductance is proportional to transmissivity, and resistivity is inversely proportional to transmissivity and hydraulic conductivity.

• Economic and Environmental Geology
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• v.13 no.3
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• pp.159-166
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• 1980

A model study was conducted for the investigation of apparent resistivity variation along with electric resistivity variation of host rock and dip variation of bed. Experiments were carried out for the cases of horizontal and dipping beds in a water tank by using Wenner and Schlumberger arrays and by changing salinity of water. The ratios of resistivity values of the bed to that of brine were 1 : 10, 1 : 50, 1 : 100 and 1 : 500. Natural coally-shale of $55cm{\times}35cm{\times}3.5cm$ was used as a bed for experimental model, and brine as a host rock. Equi-resistivity curves and characteristic curves were obtained for each case of the experiment. The equi-resistivity curve was drawn both on the cross section parallel to strike of bed and longitudinal section perpendicular to it. The characteristic curve was drawn on the cross section. In the case of dipping bed of different dips, the curves are parallel to the boundary of the bed in the upper part of the bed, and are inclined to the opposite direction with the same angle of the dip of bed in the lower part. We can deduce, from the equi-resistivity curves, the location, shape and dip of the bed. It is shown in the characteristic curves that when the ratio of resistivity value of bed to that of host rock increases, the slope of curves becomes steeper, location of low-resistivity zone lower, and the width of it narrower. The slope of curves also becomes steeper when dip of bed increases. We can deduce, from the characteristic curves, the ratio of resistivity values between adjacent beds. It was found out from the experiments that electric resistivity method could be applicable to prospecting for underground geology with an electric resistivity contrast of 1 : 10. This fact strongly suggests that distinction of coal from coally-shale could be possible in a certain field condition.

• Progress in Superconductivity
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• v.7 no.2
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• pp.103-108
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• 2006

We have measured the Hall resistivity (${\rho}_{xy}$) and the longitudinal resistivity (${\rho}_{xy}$) on superconducting $MgB_2$ thin films in extended fields up to 18 T. We found a universal scaling behavior between the Hall resistivity and the longitudinal resistivity, which is independent of the temperature and the magnetic field. At a wide magnetic field region from 1 to 18T, a universal power law of ${\beta}=2.0{\pm}0.1$ in a scaling relation, ${\rho}_{xy}={A{\rho}_{xx}}^{\beta}$, was observed in c-axis-oriented $MgB_2$ thin films. These results can be well interpreted by using recent models.

• Journal of Soil and Groundwater Environment
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• v.7 no.4
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• pp.59-67
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• 2002

As a parameter for hydrodynamic modeling to define the range of seawater intrusion, dispersivities are frequently determined from pre-experiments or theoretical studies because field experiments need a lot of time and expenses. If the dispersivities are inadequate for an aquifer, the numerical results may have some errors. We examined the validity of longitudinal dispersivities by comparing the ranges of seawater intrusion with numerical modeling, field data and apparent resistivity sections. In the numerical modeling the TDS distributions simulated by the Xu's longitudinal dispersivity are more similar to the values of TDS measured at monitoring wet]s and boreholes than those by the Neuman's longitudinal dispersivity. The ranges of seawater intrusion by numerical simulations using Xu's longitudinal dispersivity show that the contour line of 1000 ㎎/L. as TDS is located at 480 m from the coast in May, while at 390 m in July. The difference is originated from the shift of the interface between seawater and fresh water. It moved toward the coast in July because of the seasonal increase of hydraulic gradient according to rainfall. A contour line of 15 ohm-m was used to define the range of seawater intrusion in apparent resistivity sections. From this criterion on the interface between seawater and fresh water, the range of seawater intrusion is located at 450 m from the coast. This result is similar to the range of seawater intrusion simulated by the numerical modeling using Xu's dispersivity. Therefore the range of seawater intrusion shows the difference due to the dispersivities used for the hydrodynamic modeling and the dispersivity generated by the Xu's equation is considered more effective to decide the range of seawater intrusion in this study area.

• Korean Journal of Materials Research
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• v.4 no.1
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• pp.97-106
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• 1994

The dependence of the electrical resistivity on the eutectic composition and growth rates was investigated in the unidirectionally solidified Sb-InSb and Sn-Bi eutectic alloy systems, which were generally classified into the groups of f-f and nf-f eutectic system. Sb-InSb alloys containing 26-34wt.% In and Sn-Bi alloys containing 53-65wt.%Bi were prepared in vacuum sealed in a silica tube, and then these were unidirectionally solidified. Electrical resistivity of the specimens prepared by cutting the crystal section in parallel with the transverse direction and by cutting in longitudinal direction was measured. As the growth rate increased, the Sb-InSb and Sn-Bi eutectic alloys showed that the resistivity of longitudinal to the growth direction was increased but that of transverse to the growth direction was decreased. In the case of Sb-InSb eutectic alloy, increas~ng the phase boundary area and decreasing the fiber directionallity caused to increase the $p \; \parallel$ , while increasing the phase boundary area increased the $p \; \\perp$ As expected, the eutectic microstructure could be analysed well in terms of electrical resistivity.

• Journal of Magnetics
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• v.9 no.3
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• pp.89-95
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• 2004

Magnetization and electrical resistivity measurements in the wide temperature and field ranges were performed on single crystals of $UGe_2$. The presence of extremely large anisotropy in the temperature dependence of the susceptibility and magnetization has confirmed the previously published results. The dependence of spontaneous magnetization, ${\sigma}_s$, on temperature has been inferred from the Arrot plot and compared to that determined from neutron diffraction data. The earlier transversal and present longitudinal results on the magnetoresistivity are discussed in the terms of possible f-electron dualism in $UGe_2$ and its connection with the occurrence of superconductivity under pressure in this compound.

• Journal of Sensor Science and Technology
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• v.13 no.4
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• pp.303-308
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• 2004

This paper descibes on the characteristics of Ta-N(tantalum nitride) ceramic thin-film strain gauges which were deposited on Si substrates by DC reactive magnetron sputtering in an argon-nitrogen atmosphere (Ar-$(4{\sim}16%)N_{2}$) for high-temperature applications. These films were annealed in $2{\times}10^{-6}$ Torr vacuum furnace at the range of $500{\sim}1000^{\circ}C$. Optimum deposition atmosphere and annealing temperature were determined at $900^{\circ}C$ for 1 hr. in 8% $N_{2}$ gas flow ratio. Under optimum formation conditions, the Ta-N thin-film for strain gauges was obtained a high-resistivity of $768.93{\mu}{\Omega}{\cdot}cm$, a low temperature coefficient of resistance (TCR) of -84 ppm/$^{\circ}C$ and a good longitudinal gauge factor (GF) of 4.12.

• Economic and Environmental Geology
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• v.12 no.1
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• pp.1-12
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• 1979

A model study was conducted for the interpretation of simple geologic structures. Experiments were carried out for the cases of two horizontal beds and dipping beds in a water tank by using Wenner and Schlumberger arrays respectively. As a geologic stratum of experimental model, cement be (cement: sand=1:2) of $70cm{\times}60cm{\times}10cm$ was used. It was found out from a preliminary experiment that a measuring sounding of Wenner arrays is one third of the distance between two current electrodes, and Schlumberger arrays is one fourth of the distance which is a half of the value determined by usual method of calculation. Equi-resistivity curves were obtained for the cases of horizontal beds and dipping beds, and mapped on the longitudinal and cross sections of the water tank. These curves delineate the shape and degree of dip of bed to some extent. The calculation of depth to beds by using a master curve is somewhat complicated and inexact. In this study, new method for this calculation using a ${\rho}_a/{\rho}_1-a$ graph was proposed, and turned out that this method is simpler and exact.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.334-337
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• 2002

The Quantum Hall Resistance(QHR) device which consists of GaAs/AlGaAs heterojunction structure is used for the realization of QHR Standard based on QHE. In order to characterize electrical contact resistances and dissipations of the device, it is slowly cooled down for eliminating thermal shock and unwanted noise. Then, the two properties are measured under 1.5 K and 5.15 T. Contact resistances are all within 1.2 Ω and longitudinal resistivities are all within 1 mΩ up to DC 90${\mu}$A. The results mean the device is operated well to realize the QHR Standard. To confirm it, the QHR Standard having the device is compared using a direct current comparator bridge with a 1 Ω resistance standard which the calibrated value is known from QHR standards maintained by other countries. The difference between them is agreed well within measurement uncertainty. It is thus considered that the properties of the device is estimated well and has good performance.

• Smart Structures and Systems
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• v.18 no.2
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• pp.335-354
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• 2016

This contribution presents an extended one-dimensional theory for piezoelectric beam-type structures with non-ideal electrodes. For these types of electrodes the equipotential area condition is not satisfied. The main motivation of our research is originated from passive vibration control: when an elastic structure is covered by several piezoelectric patches that are linked via resistances and inductances, vibrational energy is efficiently dissipated if the electric network is properly designed. Assuming infinitely small piezoelectric patches that are connected by an infinite number of electrical, in particular resistive and inductive elements, one obtains the Telegrapher's equation for the voltage across the piezoelectric transducer. Embedding this outcome into the framework of Bernoulli-Euler, the final equations are coupled to the wave equations for the longitudinal motion of a bar and to the partial differential equations for the lateral motion of the beam. We present results for the wave propagation of a longitudinal bar for several types of electrode properties. The frequency spectra are computed (phase angle, wave number, wave speed), which point out the effect of resistive and inductive electrodes on wave characteristics. Our results show that electrical damping due to the resistivity of the electrodes is different from internal (=strain velocity dependent) or external (=velocity dependent) mechanical damping. Finally, results are presented, when the structure is excited by a harmonic single force, yielding that resistive-inductive electrodes are suitable candidates for passive vibration control that might be of great interest for practical applications in the future.