On sensitivity of surface‐to‐borehole resistivity measurements to the attitude and the depth to center of a three‐dimensional spheroid

Geophysics ◽  
1985 ◽  
Vol 50 (7) ◽  
pp. 1173-1178 ◽  
Author(s):  
F. W. Yang ◽  
S. H. Ward
Keyword(s):  
Apparent Resistivity ◽  
Current Source ◽  
Three Dimensional ◽  
The Body ◽  
Simple Method ◽  
Pilot Studies ◽  
Resistivity Measurements ◽  
Oblate Body ◽  
A Current

Borehole‐to‐surface and surface‐to‐borehole resistivity measurements are versatile but not totally tested methods for detecting anomalies in the vicinity of a borehole. The former method has been discussed by several authors (Alfano, 1962; Merkel, 1971; Merkel and Alexander, 1971; Barnett, 1972; Snyder and Merkel, 1973; Snyder, 1976; Daniels, 1977, 1978, and 1983), but the latter has not received much attention. Morrison (1971) and Daniels (1977) are among the few who have addressed the problem. Each method has its own advantages. Surface‐to‐borehole resistivity measurements are made by placing a current source on the surface and measuring the apparent resistivity in a borehole in which the measuring electrodes are closer to the body than in the borehole‐to‐surface case. Pilot studies presented here suggest that the surface‐to‐borehole method can provide indicators of the attitude and the depth to the center of a body. This paper illustrates a simple method for qualitatively determining the attitude and the depth to the center of a body for a thin three‐dimensional (3-D) conductive oblate body with the surface‐to‐borehole technique. Attitude conveys the orientation of the body— horizontal, vertical dipping toward a borehole, or dipping away from a borehole.

THREE‐DIMENSIONAL RESISTIVITY AND INDUCED‐POLARIZATION MODELING USING BURIED ELECTRODES

Geophysics ◽  
1977 ◽  
Vol 42 (5) ◽  
pp. 1006-1019 ◽  
Author(s):  
Jeffrey J. Daniels
Keyword(s):  
Electrical Properties ◽  
Apparent Resistivity ◽  
Three Dimensional ◽  
Equipotential Surface ◽  
Induced Polarization ◽  
The Body ◽  
Surface Electrode ◽  
Surface Integral ◽  
Drill Holes ◽  
Resistivity Modeling

The three‐dimensional induced‐polarization and resistivity‐modeling problem for buried source and receiver electrodes is solved by using a modified form of Barnett’s surface‐integral technique originally developed for surface‐electrode configurations. Six different buried electrode configurations are considered in this study: three types of hole‐to‐hole configurations, hole‐to‐surface and surface‐to‐hole configurations, and the single hole (bipole‐bipole) configuration. Results show there is no “best” method for all situations encountered in the field. The choice of method depends upon depth of the body, spacing of drill holes, and electrical properties of the body. In hole‐to‐hole measurements, the geometric factor (necessary for the computation of the apparent resistivity) becomes infinitely large or infinitely small whenever the receiving bipole is placed at a depth so that it lies on a zero equipotential surface. This leads to the formation of apparent resistivity anomalies that are extremely sensitive to the presence of the body but that are also complicated and not easily correlated with the position of the body. It is shown that diagnostic and easily interpretable anomalies are obtained by selecting the proper source‐receiver configurations.

scholarly journals Active Cloaking and Illusion of Electric Potentials in Electrostatics

2021 ◽  
Author(s):  
Andreas Helfrich-Schkabarenko ◽  
Alik Ismail-Zadeh ◽  
Aron Sommer
Keyword(s):  
Electric Potential ◽  
Superposition Principle ◽  
Current Source ◽  
Three Dimensional ◽  
Numerical Results ◽  
Research Fields ◽  
Electric Potentials ◽  
Three Dimensional Models ◽  
First Time ◽  
A Current

Abstract Cloaking and illusion has been demonstrated theoretically and experimentally in several research fields. Here we present for the first time an active exterior cloaking device in electrostatics operating in a two-horizontally-layered electroconductive domain, and use the superposition principle to cloak electric potentials. The device uses an additional current source pattern introduced on the interface between two layers to cancel the total electric potential to be measured. Also, we present an active exterior illusion device allowing for detection of a signal pattern corresponding to any arbitrarily chosen current source instead of the existing current source. The performance of the cloaking/illusion devices is demonstrated by three-dimensional models and numerical experiments using synthetic measurements of the electric potential. Sensitivities of numerical results to a noise in measured data and to a size of cloaking devices are analysed. The numerical results show quite reasonable cloaking/illusion performance, which means that a current source can be hidden electrostatically. The developed active cloaking/illusion methodology can be used in subsurface geo-exploration studies, electrical engineering, live sciences, and elsewhere.

Current Source Design for 3D Magnetic Field Simulation

2013 ◽  
Vol 760-762 ◽  
pp. 1354-1359
Author(s):  
Zhi Li ◽  
Shu Bao Pan
Keyword(s):  
Magnetic Field ◽  
Design Principle ◽  
Current Source ◽  
Three Dimensional ◽  
Calibration Method ◽  
Constant Current ◽  
Constant Current Source ◽  
Precision Error ◽  
Magnetic Field Simulation ◽  
A Current

This paper designs a current source which is used for simulating the three dimensional magnetic field. Gives the circuit schematic, Analyzes the design principle of the circuit and puts forward the calibration method of software which is suitable for the operation in microprocessor and improves the output accuracy of the constant current source. Actual test shows that the output of the constant current source is 0.1mA-500mA and the precision error is less than 0.03% of full scale. It has been used in the degaussing device testing and maintenance. The performance is stable and reliable achieves good results.

Analysis of multiple‐source bipole‐quadripole resistivity surveys using the apparent resistivity tensor

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 972-983 ◽  
Author(s):  
H. M. Bibby
Keyword(s):  
Electric Field ◽  
Apparent Resistivity ◽  
Extreme Values ◽  
Strong Dependence ◽  
Current Source ◽  
The Body ◽  
Multiple Source ◽  
Tensor Invariants ◽  
Resistivity Tensor ◽  
Receiver Array

Measurements of apparent resistivity made using the bipole‐dipole method depend upon the location and orientation of the current source relative to the body under study. Although it has been recognized that this dependence on orientation can be partially overcome by use of two current bipoles with different orientations, no agreement on the method of analysis of multiple source surveys has been reached. The most general form of presentation of such results is an apparent resistivity tensor. Various rotation invariants derived from the apparent resistivity tensor can be regarded as mean values of apparent resistivity, independent of the direction of the electric field, thus greatly reducing the “false anomalies” typical of single‐source bipole‐dipole survey results. Two of the tensor invariants obey the principle of reciprocity: if the roles of the current and potential electrodes are interchanged, the invariants are unchanged. The properties of the apparent resistivity tensor are demonstrated for selected simple models. For a horizontally layered medium, when the receiver array is far from the current source, the tensor is symmetric and has invariants which depend only on the distance from the current source. The extreme values of apparent resistivity occur when the electric field vector is tangential and radial relative to the current source. These extreme values correspond to the Schlumberger apparent resistivity and the “polar” dipole apparent resistivity, respectively. Lateral discontinuities in resistivity are modeled with both a single vertical discontinuity and a hemispherical model. The source‐dependent variations in the apparent resistivity derived from a single‐current bipole are greatly reduced in plots of the tensor invariants. For a vertical discontinuity, the tensor trace (the sum of the diagonal elements) is close to the resistivity underlying the receiver site, whereas for a hemisphere, the square root of the tensor determinant gives the best representation. Near lateral discontinuities in resistivity, the apparent resistivity tensor indicates strong dependence of apparent resistivity on the direction of the measured electric field. This apparent anisotropy can be used as an indicator of such discontinuities, yielding both position and orientation of the discontinuity.

IP AND RESISTIVITY TYPE CURVES FOR THREE‐DIMENSIONAL BODIES

Geophysics ◽  
1969 ◽  
Vol 34 (4) ◽  
pp. 615-632 ◽  
Author(s):  
K. Dieter ◽  
N. R. Paterson ◽  
F. S. Grant
Keyword(s):  
Arbitrary Shape ◽  
Apparent Resistivity ◽  
Three Dimensional ◽  
Spherical Shape ◽  
The Body ◽  
Electrode Arrays ◽  
Method Of Least Squares ◽  
Straightforward Manner ◽  
Type Curves ◽  
Actual Field

A new method for calculating anomaly patterns and type curves of apparent resistivity and apparent chargeability over three‐dimensional bodies imbedded in a half‐space is practicable. The solution of the boundary‐value problem for a point source of current near a body of arbitrary shape in the form of an inhomogeneous integral equation is solved numerically by the method of least squares. The solution is then used to construct the apparent resistivity and apparent chargeability functions for three and four‐electrode arrays in the vicinity of the body in a straightforward manner. Type curves show the application to an actual field example. Finally, some simple, direct aids for interpreting anomalies over mineralized zones of compact (i.e. roughly spherical) shape result. This study represents the results of the first phase of a continuing program of research into resistivity and IP interpretation theory.

ANALYTIC MODELS FOR THE INTERPRETATION OF ELECTRICAL SURVEYS USING BURIED CURRENT ELECTRODES

Geophysics ◽  
1973 ◽  
Vol 38 (3) ◽  
pp. 513-529 ◽  
Author(s):  
Donald D. Snyder ◽  
Richard M. Merkel
Keyword(s):  
Apparent Resistivity ◽  
Three Dimensional ◽  
Drill Hole ◽  
Surface Electrode ◽  
Sphere Model ◽  
Current Electrode ◽  
Anomaly Pattern ◽  
Lateral Offset ◽  
Analytic Models ◽  
A Current

The IP response and the apparent resistivity resulting from a buried current pole in the presence of a stratigraphic target and a three‐dimensional target have been studied. The targets were modeled using a layered model to simulate the stratigraphic target and a buried sphere model to simulate the three‐dimensional target. The results show that there is a substantial increase in the response of the target measured at the surface for current electrode depths of greater than half the depth to the top of the target. A larger anomalous response is of particular importance when dealing with deeply buried targets from which little or no response is measured using conventional surface electrode methods. Furthermore, the results indicate that a survey around a drill hole containing a current electrode can be used to outline mineralization in the immediate vicinity of the drill hole. Some empirical observations resulting from our study are presented which relate the lateral offset of the target from the drill hole and its depth to characteristics of the anomaly pattern as measured on the surface.

scholarly journals Three‐dimensional mise‐à‐la‐masse modeling applied to mapping fracture zones

Geophysics ◽  
1986 ◽  
Vol 51 (1) ◽  
pp. 98-113 ◽  
Author(s):  
Craig W. Beasley ◽  
Stanley H. Ward
Keyword(s):  
Cross Section ◽  
Apparent Resistivity ◽  
Three Dimensional ◽  
The Body ◽  
Near Miss ◽  
Geothermal System ◽  
Volume Integral ◽  
Fracture Zones ◽  
Current Case ◽  
Similar Shape

A numerical scheme applying the method of volume integral equations has been developed for borehole‐to‐borehole and borehole‐to‐surface modeling of the apparent resistivity response of a thin conductive body in a half‐space; the inhomogeneity simulates a fracture zone in a geothermal system. The algorithm is applicable for the direct‐current case when the buried electrode is either inside (mise‐à‐la‐masse) or outside (near‐miss) the body. In implementing the scheme, the integral equation is transformed into a matrix equation as a result of discretizing the inhomogeneity into rectangular cells. All physical properties are assumed constant within each cell. The rectangular cells are used through‐out execution of the algorithm. The computed surface and subsurface apparent resistivity responses are examined for bodies of similar shape and size but with different orientations: (1) vertical, (2) horizontal, (3) dipping at 60 degrees, and (4) dipping at 30 degrees. The four bodies produce apparent resistivity cross‐section plots which differ little from each other except in orientation. Varying the depth to the top of a body does not significantly alter the subsurface apparent resistivity response in the vicinity of the body. In both section and plan views, estimates of orientation, areal extent, and dip can often be made. The maximum depth at which a body can be located and still produce a detectable surface anomaly is dependent upon the position of the buried electrode and upon the contrast in conductivity. Locating the buried electrode just outside the body does not significantly alter the results from those when the electrode is embedded in the inhomogeneity. However, the similarity between the results of these two cases decreases as the distance between the electrode and the body is increased.

scholarly journals Active cloaking and illusion of electric potentials in electrostatics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andreas Helfrich-Schkabarenko ◽  
Alik Ismail-Zadeh ◽  
Aron Sommer
Keyword(s):  
Electric Potential ◽  
Superposition Principle ◽  
Current Source ◽  
Three Dimensional ◽  
Numerical Results ◽  
Research Fields ◽  
Electric Potentials ◽  
Three Dimensional Models ◽  
First Time ◽  
A Current

AbstractCloaking and illusion has been demonstrated theoretically and experimentally in several research fields. Here we present for the first time an active exterior cloaking device in electrostatics operating in a two-horizontally-layered electroconductive domain, and use the superposition principle to cloak electric potentials. The device uses an additional current source pattern introduced on the interface between two layers to cancel the total electric potential to be measured. Also, we present an active exterior illusion device allowing for detection of a signal pattern corresponding to any arbitrarily chosen current source instead of the existing current source. The performance of the cloaking/illusion devices is demonstrated by three-dimensional models and numerical experiments using synthetic measurements of the electric potential. Sensitivities of numerical results to a noise in measured data and to a size of cloaking devices are analysed. The numerical results show quite reasonable cloaking/illusion performance, which means that a current source can be hidden electrostatically. The developed active cloaking/illusion methodology can be used in subsurface geo-exploration studies, electrical engineering, live sciences, and elsewhere.

Scanning electron microscopy of freeze-fractured prescapular lymph node of caprine

1984 ◽  
Vol 42 ◽  
pp. 244-245
Author(s):  
O. Faroon ◽  
F. Al-Bagdadi ◽  
T. G. Snider ◽  
C. Titkemeyer
Keyword(s):  
Lymph Node ◽  
Lymph Nodes ◽  
Lymphatic System ◽  
Three Dimensional ◽  
Meat Products ◽  
The Body ◽  
Morphological Data ◽  
The World ◽  
Cellular Constituent ◽  
Scanning Electron

The lymphatic system is very important in the immunological activities of the body. Clinicians confirm the diagnosis of infectious diseases by palpating the involved cutaneous lymph node for changes in size, heat, and consistency. Clinical pathologists diagnose systemic diseases through biopsies of superficial lymph nodes. In many parts of the world the goat is considered as an important source of milk and meat products.The lymphatic system has been studied extensively. These studies lack precise information on the natural morphology of the lymph nodes and their vascular and cellular constituent. This is due to using improper technique for such studies. A few studies used the SEM, conducted by cutting the lymph node with a blade. The morphological data collected by this method are artificial and do not reflect the normal three dimensional surface of the examined area of the lymph node. SEM has been used to study the lymph vessels and lymph nodes of different animals. No information on the cutaneous lymph nodes of the goat has ever been collected using the scanning electron microscope.

scholarly journals Fabrication of Eutectic Ga-In Nanowire Arrays Based on Plateau–Rayleigh Instability

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4616
Author(s):  
Takashi Ikuno ◽  
Zen Somei
Keyword(s):  
Integrated Circuits ◽  
Substrate Surface ◽  
Three Dimensional ◽  
Average Diameter ◽  
Nanowire Arrays ◽  
Scanning Probe ◽  
Rayleigh Instability ◽  
Simple Method ◽  
Flat Substrate ◽  
Metal Nanowire

We have developed a simple method of fabricating liquid metal nanowire (NW) arrays of eutectic GaIn (EGaIn). When an EGaIn droplet anchored on a flat substrate is pulled perpendicular to the substrate surface at room temperature, an hourglass shaped EGaIn is formed. At the neck of the shape, based on the Plateau–Rayleigh instability, the EGaIn bridge with periodically varying thicknesses is formed. Finally, the bridge is broken down by additional pulling. Then, EGaIn NW is formed at the surface of the breakpoint. In addition, EGaIn NW arrays are found to be fabricated by pulling multiple EGaIn droplets on a substrate simultaneously. The average diameter of the obtained NW was approximately 0.6 μm and the length of the NW depended on the amount of droplet anchored on the substrate. The EGaIn NWs fabricated in this study may be used for three-dimensional wiring for integrated circuits, the tips of scanning probe microscopes, and field electron emission arrays.

Sign in / Sign up

Export Citation Format

Share Document