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.

THE APPARENT RESISTIVITY TENSOR

Geophysics ◽  
1977 ◽  
Vol 42 (6) ◽  
pp. 1258-1261 ◽  
Author(s):  
H. M. Bibby
Keyword(s):  
Electric Field ◽  
Apparent Resistivity ◽  
Geometric Mean ◽  
Field Station ◽  
Tensor Invariants ◽  
Resistivity Tensor ◽  
Reduced Data

The scalar apparent resistivity was originally defined for simple linear electrode resistivity arrays such as Wenner and Schlumberger arrays. With the extension of resistivity surveying into bipole‐dipole arrays, several different and not obviously related definitions of apparent resistivity have been used by different authors despite similar field procedure. In this note we show that when a pair of current sources (or quadripole source) is used, and the corresponding electric field vectors are measured at each field station, the most comprehensive expression of the reduced data is as an apparent resistivity tensor. Other definitions of apparent resistivity can be simply related to this tensor. For example, the quadripole‐quadripole apparent resistivity of Doicin (1976) is one of the tensor invariants; the maximum and minimum resistivities defined by the rotating dipole method of Furgerson and Keller (1975) can be simply derived, and their geometric mean is shown to be the quadripole‐quadripole value.

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.

scholarly journals A High Efficiency Low Noise RF-to-DC Converter Employing Gm-Boosting Envelope Detector and Offset Canceled Latch Comparator

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1078
Author(s):  
Thi Thuy Pham ◽  
Dongmin Kim ◽  
Seo-Hyeong Jeong ◽  
Junghyup Lee ◽  
Donggu Im
Keyword(s):  
Power Consumption ◽  
High Efficiency ◽  
Supply Voltage ◽  
Current Source ◽  
Low Noise ◽  
The Body ◽  
Common Source ◽  
Conversion Gain ◽  
Input Transistor ◽  
Envelope Detector

This work presents a high efficiency RF-to-DC conversion circuit composed of an LC-CL balun-based Gm-boosting envelope detector, a low noise baseband amplifier, and an offset canceled latch comparator. It was designed to have high sensitivity with low power consumption for wake-up receiver (WuRx) applications. The proposed envelope detector is based on a fully integrated inductively degenerated common-source amplifier with a series gate inductor. The LC-CL balun circuit is merged with the core of the envelope detector by sharing the on-chip gate and source inductors. The proposed technique doubles the transconductance of the input transistor of the envelope detector without any extra power consumption because the gate and source voltage on the input transistor operates in a differential mode. This results in a higher RF-to-DC conversion gain. In order to improve the sensitivity of the wake-up radio, the DC offset of the latch comparator circuit is canceled by controlling the body bias voltage of a pair of differential input transistors through a binary-weighted current source cell. In addition, the hysteresis characteristic is implemented in order to avoid unstable operation by the large noise at the compared signal. The hysteresis window is programmable by changing the channel width of the latch transistor. The low noise baseband amplifier amplifies the output signal of the envelope detector and transfers it into the comparator circuit with low noise. For the 2.4 GHz WuRx, the proposed envelope detector with no external matching components shows the simulated conversion gain of about 16.79 V/V when the input power is around the sensitivity of −60 dBm, and this is 1.7 times higher than that of the conventional envelope detector with the same current and load. The proposed RF-to-DC conversion circuit (WuRx) achieves a sensitivity of about −65.4 dBm based on 45% to 55% duty, dissipating a power of 22 μW from a 1.2 V supply voltage.

scholarly journals Electrochemotherapy Effectiveness Loss due to Electric Field Indentation between Needle Electrodes: A Numerical Study

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
José Alvim Berkenbrock ◽  
Rafaela Grecco Machado ◽  
Daniela Ota Hisayasu Suzuki
Keyword(s):  
Electric Field ◽  
In Silico ◽  
Treatment Effectiveness ◽  
Numerical Study ◽  
Specific Treatment ◽  
The Body ◽  
Membrane Selectivity ◽  
Chemotherapy Drugs ◽  
Mast Cell Tumor ◽  
Anticancer Treatment

Electrochemotherapy is an anticancer treatment based on applying electric field pulses that reduce cell membrane selectivity, allowing chemotherapy drugs to enter the cells. In parallel to electrochemotherapy clinical tests, in silico experiments have helped scientists and clinicians to understand the electric field distribution through anatomically complex regions of the body. In particular, these in silico experiments allow clinicians to predict problems that may arise in treatment effectiveness. The current work presents a metastatic case of a mast cell tumor in a dog. In this specific treatment planning study, we show that using needle electrodes has a possible pitfall. The macroscopic consequence of the electroporation was assessed through a mathematical model of tissue electrical conductivity. Considering the electrical and geometrical characteristics of the case under study, we modeled an ellipsoidal tumor. Initial simulations were based on the European Standard Operating Procedures for electrochemotherapy suggestions, and then different electrodes’ arrangements were evaluated. To avoid blind spots, multiple applications are usually required for large tumors, demanding electrode repositioning. An effective treatment electroporates all the tumor cells. Partially and slightly overlapping the areas increases the session’s duration but also likely increases the treatment’s effectiveness. It is worth noting that for a single application, the needles should not be placed close to the tumor’s borders because effectiveness is highly likely to be lost.

Two-dimensional scattering of a plane compressional wave by surface imperfections

1969 ◽  
Vol 59 (3) ◽  
pp. 1349-1364
Author(s):  
Ivor K. McIvor
Keyword(s):  
Order Approximation ◽  
Strong Dependence ◽  
Plane Waves ◽  
Compressional Wave ◽  
Elastic Half Space ◽  
Kernel Functions ◽  
The Body ◽  
Angle Of Incidence ◽  
Small Surface ◽  
Surface Imperfections

abstract A perturbation method for treating the scattering of plane waves by small surface imperfections on an elastic half space is presented. The solution to the first order approximation is given as convolution integrals of the surface imperfection with kernel functions defined by Fourier inversion integrals. The evaluation of these integrals is discussed and their asymptotic representations determined. The far field scattered displacements are explicitly obtained for arbitrary imperfections. The scattered field consists of a Rayleigh surface wave and four body phases which at the free surface travel with the speed of dilational or distortional waves. Numerical examples are given. In particular the error in the apparent angle of emergence due to the scattered waves is obtained. The body phases exhibit the familiar 3/2 geometric attenuation, but still may make a significant contribution at moderately long distances. A strong dependence of the magnitude of the error on the angle of incidence is demonstrated.

Effect of the Electric Field Profile on the Accuracy of E-FISH Measurements in Ionization Waves

2021 ◽  
Author(s):  
Tat Loon Chng ◽  
David Z. Pai ◽  
Olivier Guaitella ◽  
Svetlana M Starikovskaia ◽  
Anne Bourdon
Keyword(s):  
Electric Field ◽  
Intermediate Phase ◽  
Second Harmonic ◽  
Strong Dependence ◽  
Field Profile ◽  
Test Configuration ◽  
True Value ◽  
Field Evolution ◽  
Electric Field Profile ◽  
Fish Signal

Abstract Electric field induced second harmonic (E-FISH) generation has emerged as a versatile tool for measuring absolute electric field strengths in time-varying, non-equilibrium plasmas and gas discharges. Yet recent work has demonstrated that the E-FISH signal, when produced with tightly focused laser beams, exhibits a strong dependence on both the length and shape of the applied electric field profile (along the axis of laser beam propagation). In this paper, we examine the effect of this dependence more meaningfully, by predicting what an E-FISH experiment would measure in a plasma, using 2D axisymmetric numerical fluid simulations as the true value. A pin-plane nanosecond discharge at atmospheric pressure is adopted as the test configuration, and the electric field evolution during the propagation of the ionization wave (IW) is specifically analyzed. We find that the various phases of this evolution (before and up to the front arrival, immediately behind the front and after the connection to the grounded plane) are quite accurately described by three unique electric field profile shapes, each of which produces a different response in the E-FISH signal. As a result, the accuracy of an E-FISH measurement is generally predicted to be comparable in the first and third phases of the IW evolution, and significantly poorer in the second (intermediate) phase. Fortunately, even though the absolute error in the field strength at certain time instants could be large, the overall shape of the field evolution curve is relatively well captured by E-FISH. Guided by the simulation results, we propose a procedure for estimating the error in the initial phase of the IW development, based on the presumption that the starting field profile mirrors that of its corresponding Laplacian conditions before evolving further. We expect that this approach may be readily generalized and applicable to other IW problems or phenomena, thus extending the utility of the E-FISH diagnostic.

Bias correction of extreme values of high resolution climate simulations for risk analysis.

2021 ◽  
Author(s):  
luis Augusto sanabria ◽  
Xuerong Qin ◽  
Jin Li ◽  
Robert Peter Cechet
Keyword(s):  
Climate Change ◽  
Bias Correction ◽  
Extreme Values ◽  
The Body ◽  
Future Climate ◽  
Return Periods ◽  
Climate Conditions ◽  
Mitigation And Adaptation ◽  
Climate Simulations ◽  
The Impact

Abstract Most climatic models show that climate change affects natural perils' frequency and severity. Quantifying the impact of future climate conditions on natural hazard is essential for mitigation and adaptation planning. One crucial factor to consider when using climate simulations projections is the inherent systematic differences (bias) of the modelled data compared with observations. This bias can originate from the modelling process, the techniques used for downscaling of results, and the ensembles' intrinsic variability. Analysis of climate simulations has shown that the biases associated with these data types can be significant. Hence, it is often necessary to correct the bias before the data can be reliably used for further analysis. Natural perils are often associated with extreme climatic conditions. Analysing trends in the tail end of distributions are already complicated because noise is much more prominent than that in the mean climate. The bias of the simulations can introduce significant errors in practical applications. In this paper, we present a methodology for bias correction of climate simulated data. The technique corrects the bias in both the body and the tail of the distribution (extreme values). As an illustration, maps of the 50 and 100-year Return Period of climate simulated Forest Fire Danger Index (FFDI) in Australia are presented and compared against the corresponding observation-based maps. The results show that the algorithm can substantially improve the calculation of simulation-based Return Periods. Forthcoming work will focus on the impact of climate change on these Return Periods considering future climate conditions.

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