Hole‐to‐hole resistivity signatures of cylindrical cavities: Dipole‐dipole electrode array

Geophysics ◽  
1986 ◽  
Vol 51 (3) ◽  
pp. 788-799 ◽  
Author(s):  
Jorge O. Parra ◽  
Thomas E. Owen
Keyword(s):  
General Solution ◽  
Numerical Procedure ◽  
Electrode Array ◽  
Processing Technique ◽  
Electrode Geometry ◽  
Host Medium ◽  
Resistivity Measurements ◽  
Array Configuration ◽  
Cylindrical Cavities ◽  
Conductivity Contrast

A numerical procedure for predicting cavity signatures for a dipole‐dipole array configuration in hole‐to‐ hole resistivity measurements has been developed. This electrode geometry is implemented from the general solution for a point source of current near an air‐filled cylindrical cavity or an air‐filled cylinder surrounded by a concentric conductive or resistive halo region embedded in a homogeneous conducting host medium to simulate hole‐to‐hole resistivity measurements. Cavity signatures obtained for several vertical offset distances between the source and detector dipoles as well as multiply spaced dipole‐dipole responses suggest that a processing technique may be devised to identify directly the position of the cavity inhomogeneity with respect to the boreholes. The results also show that the presence of a concentric halo region more conductive than the host medium influences the overall signature by either reducing or enhancing the effect of the air‐filled cavity depending upon the halo size and conductivity contrast. In comparison, a halo region more resistive than the host medium always influences the composite signature by enhancing the effect of the air‐filled cavity.

Fabrication of a novel laser-processed NiTi shape memory microgripper with enhanced thermomechanical functionality

2012 ◽  
Vol 24 (8) ◽  
pp. 984-990 ◽  
Author(s):  
Matthew Daly ◽  
Andrew Pequegnat ◽  
Yunhong N Zhou ◽  
Mohammad I Khan
Keyword(s):  
Shape Memory ◽  
Processing Technique ◽  
Thermomechanical Properties ◽  
Nickel Titanium ◽  
Testing Methods ◽  
Scanning Calorimetry ◽  
Resistivity Measurements ◽  
Processed Material ◽  
Significant Research

The thermomechanical properties of nickel-titanium shape memory alloys have sparked significant research efforts seeking to exploit their exotic capabilities. Until recently, the performance capabilities of nickel-titanium devices have been inhibited by the retention of only one thermomechanical response. In this article, the application of a novel laser-processing technique is demonstrated to create a monolithic self-positioning nickel-titanium shape memory microgripper. Device actuation and gripping maneuvers were achieved by thermally activating processed material regions which possessed unique phase transformation onset temperatures and thermomechanical recovery characteristics. The existence of each thermomechanical material domain was confirmed through differential scanning calorimetry analysis. Independent thermomechanical recoveries of each embedded shape memory were captured using tensile testing methods. Deployment of each embedded shape memory was achieved using resistive heating, and in situ resistivity measurements were used to monitor progressive phase transformations.

The face‐current concept and its application to survey design in electrical exploration

Geophysics ◽  
2003 ◽  
Vol 68 (3) ◽  
pp. 900-910 ◽  
Author(s):  
Carlos A. Mendonça
Keyword(s):  
Survey Design ◽  
Electrical Potential ◽  
Ground Surface ◽  
Electrode Array ◽  
Homogeneous Half Space ◽  
The Face ◽  
Geoelectrical Structure ◽  
Dipole Sources ◽  
Conductivity Contrast

This paper presents a new method to identify the regions over a 3D geoelectrical structure that produce major contributions to the electrical potential established in response to a dc source at the ground surface. The measured potential is represented by a sum of a known primary potential (due to a homogeneous half space) plus an unknown potential caused by conductivity inhomogeneities. Because the primary potential is continuous everywhere, the interfaces with a conductivity contrast act as sources or sinks of currents in order to maintain the continuity of the current density related to the primary flux. These disturbing face currents are responsible for the generation of the secondary potential, and mapping them over a given structure allows us to assess the regions where the secondary potential is generated. In general, the face currents vanish away from the source according to the decay of the primary electric field. For this reason, deeper investigations can be expected when using pole sources because its primary field decays with the inverse of the squared distance, instead of the cubed distance as for dipole sources. For thin sheets, the polarization decay with distance is one order higher than that for large 3D bodies, which makes the detection of a sheet yet more difficult. The quantification of the total face current over the structure for different positions along a profile helps one choose the proper electrode array and determine its optimum length. This is done in two steps: (1) identification of the offset where the dc source provides the highest polarization (face current) on the targeted structure, and (2) determination of the array length by locating the potential electrodes closest to the region with the highest polarization. This second criterion came from an analogy between the face‐current and artificial current sources, where it is intuitively seen that the resulting potential is highest close to the source. The proposed survey design technique is applied to three models commonly used in electrical exploration: a shallow conductive heterogeneity, a buried contact, and a thin conductive sheet.

Design and modeling of an electromagnetic launcher for weft insertion system

2018 ◽  
Vol 89 (5) ◽  
pp. 834-844 ◽  
Author(s):  
Emad Owlia ◽  
Seyed Abbas Mirjalili ◽  
Mostafa Shahnazari
Keyword(s):  
Numerical Procedure ◽  
Processing Technique ◽  
Experimental Methodology ◽  
Image Processing Technique ◽  
Weft Yarn ◽  
The Finite Element Method ◽  
Projectile Velocity ◽  
Electromagnetic Launcher ◽  
The Relationship ◽  
Specific Amount

An electromagnetic launcher can be used as an accelerator for yarn attached to a ferromagnetic projectile. As a result, yarn endures a specific amount of tension. In addition to the yarn variables and the type of weft insertion system, the parameters of the weft yarn accelerator strongly affect the weft yarn velocity, its tension, and consequently the fabric quality. An applicable model that can represent the relationship between input and output parameters of this weft insertion system is very useful for predicting the strike of the projectile. Therefore, in this research a 3D imitating launching model was developed by the finite element method. A coil electromagnetic launcher was employed. An experimental methodology using an image-processing technique was also utilized to measure the projectile velocity. Numerical results were compared with experimental results to verify the numerical procedure. A validated model can be a reliable tool to investigate the effects of many process parameters on the strike of the projectile and to optimize them. Therefore, the system parameters can be scientifically defined by this model to insert a weft yarn.

MATLAB code for data-driven initial model of 1D Schlumberger sounding curve

Geophysics ◽  
2018 ◽  
Vol 83 (2) ◽  
pp. F21-F28 ◽  
Author(s):  
Jide Nosakare Ogunbo
Keyword(s):  
Random Noise ◽  
Electrode Array ◽  
Automatic Process ◽  
Model Parameters ◽  
Curve Matching ◽  
Nonlinear Inversion ◽  
Array Configuration ◽  
Matlab Code ◽  
Resistivity Model ◽  
Schlumberger Sounding

A MATLAB code automatically performs partial curve matching of 1D apparent resistivity data recorded with the Schlumberger electrode array configuration. The two-layer master and auxiliary curves are used to systematically match through the branches of data extracting the corresponding model properties. Partial curve matching is a classical interpretation procedure of the sounding curve, which has been done manually. Results from the manual and automatic procedures are compared. The matched geoelectric models from the automatic process are retrieved more quickly, and these results are consistent because the process is digitalized and are not dependent on human numerical accuracy judgment. Magnitudes of random noise affect the final matched model parameters, yet these values are sufficient to be initial models for subsequent nonlinear inversion. It is hoped that for an inversion workflow, the code can be included to automatically find an initial resistivity model.

Effects of Biased AC Electroosmotic Micro-Pumping on Symmetric and Asymmetric Electrode Arrays

2012 ◽  
Author(s):  
Nazmul Islam
Keyword(s):  
Electrode Array ◽  
Theoretical Models ◽  
Electrode Arrays ◽  
Flow Measurements ◽  
Flow Rates ◽  
Forward Flow ◽  
Electrically Conducting ◽  
Array Configuration ◽  
Mems Fabrication ◽  
Dc Bias

This paper presents an analysis and experiment results that were conducted to assess the effect of combining an AC signal with a DC bias when generating the electric field on electrode arrays needed to impart electroosmosis within a microchannel. The analysis was done using COMSOL 3.5a in which currently available theoretical models for EO flows were embedded in the software and solved numerically. The simulation evaluate the effects of channel geometry, frequency of excitation, electrode array geometry, and AC signal with a DC bias on the flow imparted on an electrically conducting fluid. For the AC driven flow, the simulation results indicate the existence of an optimized frequency of excitation and an optimum geometry that lead to the maximum net forward flow of the pump. No relevant net flows were generated with the symmetric electrode arrays with a constant magnitude of AC voltage applied to both electrodes. However, superimposing a DC signal over the AC signal on the same symmetric electrode array lead to a noticeable net forward flow of 18.70 μL/min. On the other hand asymmetric electrode pattern can generate flow in both cases and can improve the microflow inside the micro-channel. Experimental flow measurements were performed on several electrode array configurations manufactured using typical MEMS fabrication techniques. The experimental results are in good agreement with the simulation data. They confirm that using an asymmetric electrode array excited by an AC signal with a DC bias leads to a significant improvement in flow rates in comparison to the flow rates obtained in an asymmetric electrode array configuration excited just with an AC signal.

Novel Signal Processing Technique for Capture and Isolation of Blink-Related Oscillations Using a Low-Density Electrode Array for Bedside Evaluation of Consciousness

2020 ◽  
Vol 67 (2) ◽  
pp. 453-463 ◽  
Author(s):  
Careesa C. Liu ◽  
Sujoy Ghosh Hajra ◽  
Shaun D. Fickling ◽  
Gabriela Pawlowski ◽  
Xiaowei Song ◽  
...  
Keyword(s):  
Signal Processing ◽  
Electrode Array ◽  
Processing Technique ◽  
Low Density ◽  
Signal Processing Technique

scholarly journals Analysis Of Electrical Resistivity Data For The Delineation Of Ground Water Prospective Zones At Karchana Block Of Allahabad District. U. P. India

2018 ◽  
Vol 1 (7) ◽  
pp. 1-10
Author(s):  
Vinit J.Ganvir ◽  
Arjun Singh ◽  
Pushpesh Kumar ◽  
Amaresh Kr. Singh ◽  
Vineet Kumar
Keyword(s):  
Electrical Resistivity ◽  
Natural Resources ◽  
Ground Water ◽  
Imaging Technique ◽  
Electrode Array ◽  
Resistivity Imaging ◽  
Array Configuration ◽  
Resistivity Data ◽  
Selection Of

Electrical resistivity of sounding of Karchana block was conducted to delineating the ground water feasibility and selection of sites for installation of bore wells. The reason for choosing this area have undergone stress for the natural resources like water is continuous declining of ground water due to urbanization and industrialization also it was dark block in 2008. 2 D resistivity imaging technique was utilized. The 2 D resistivity technique/electrical resistivity technique utilized the Schlumberger electrode array configuration because this array is moderately sensitive to both vertical and horizontal structures.Twenty (20) vertical electrical resistivity soundings were acquired with ABEM resistivity Terameter in Schlumberger configuration.

scholarly journals On the Effects of Package on the PMUTs Performances—Multiphysics Model and Frequency Analyses

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 307 ◽  
Author(s):  
Gianluca Massimino ◽  
Alessandro Colombo ◽  
Raffaele Ardito ◽  
Fabio Quaglia ◽  
Alberto Corigliano
Keyword(s):  
Numerical Procedure ◽  
Design Guidelines ◽  
Ultrasonic Transducers ◽  
Acoustic Transmission ◽  
Acoustic Structure ◽  
Mechanical Coupling ◽  
Structure Interaction ◽  
Array Configuration ◽  
Propagation Pattern ◽  
Complete Set

This paper deals with a multiphysics numerical modelling via finite element method (FEM) of an air-coupled array piezoelectric micromachined ultrasonic transducers (PMUTs). The proposed numerical model is fully 3D with the following features: the presence of the fabrication induced residual stresses, which determine a geometrically non-linear initial deformed configuration of the diaphragms and a remarkable shift of the fundamental frequency; the multiple coupling between different physics, namely electro-mechanical-coupling for the piezo-electric model, acoustic-structure interaction at the acoustic-structure interface and pressure acoustics in the surrounding air. The model takes into account the complete set of PMUTs belonging to the silicon die in a 4 × 4 array configuration and the protective package, as well. The results have been validated by experimental data, in terms of initial static pre-deflected configuration of the diaphragms and frequency response function of the PMUT. The numerical procedure was applied, to analyze different package configurations of the device, to study the influence of the holes on the acoustic transmission in terms of SPL and propagation pattern and consequently extract a set of design guidelines.

Application of the pole‐dipole resistivity technique to the detection of solution cavities beneath highways

Geophysics ◽  
1986 ◽  
Vol 51 (3) ◽  
pp. 833-837 ◽  
Author(s):  
Douglas L. Smith
Keyword(s):  
Electrical Resistivity ◽  
Water Table ◽  
Strong Correlation ◽  
Country Rock ◽  
Electrode Array ◽  
High Resistivity ◽  
Switching System ◽  
Resistivity Measurements ◽  
Lower Electrical Resistivity

Using a multiconductor electrode cable and a 30‐post switching system, pole‐dipole electrical resistivity measurements with a linear electrode array demonstrated a strong correlation between resistivity anomalies and subsurface voids at four sites in Florida. Solution cavities below the water table are filled with a groundwater‐solute mixture which is characterized by a lower electrical resistivity than the enclosing country rock (Eocene and younger limestone). Air‐filled cavities above the water table exhibit markedly high‐resistivity anomalies. Confirmation drilling of postulated cavities and other anomalies suggests the method can be used with confidence for identification and location of highway‐threatening solution cavities with diameters as small as 3 to 5 m to a depth of 25 to 30 m.

Sign in / Sign up

Export Citation Format

Share Document