Effects of pipelines on spectral induced‐polarization surveys

Geophysics ◽  
1984 ◽  
Vol 49 (11) ◽  
pp. 1979-1992 ◽  
Author(s):  
Jorge O. Parra
Keyword(s):  
Electromagnetic Coupling ◽  
Low Frequency ◽  
Electrode Array ◽  
Interfacial Polarization ◽  
Skin Depth ◽  
External Observer ◽  
Array Configuration ◽  
Data Distortion ◽  
Arbitrary Position ◽  
Induced Currents

The formal electromagnetic coupling solution for a dipole-dipole electrode array configuration has been modified to include cultural coupling in a uniform conducting half‐space. Solutions are obtained for survey lines oriented at an arbitrary position and angle with respect to a cylindrical structure. The convergence properties of the general mutual impedance solution are analyzed using a low‐frequency approximation which is useful in predicting cultural anomalies in the frequency range of spectral IP surveys as long as all significant dimensions are less than one skin depth. Both interfacial polarization and induced currents in the cylindrical conductor are considered in examining the behavior of the overall spectrum as seen by an external observer. Spectral responses for dipole-dipole arrays oriented perpendicular and parallel to the buried conductor show that the phase shift is the most diagnostic parameter for pipe depth and survey data distortion. The results also show that field survey procedures can be devised to minimize such interference effects when the pipe position is known.

Immediate and 1-Year Outcomes with a Slim Modiolar Cochlear Implant Electrode Array

2020 ◽  
Vol 162 (5) ◽  
pp. 731-736
Author(s):  
Nedim Durakovic ◽  
Dorina Kallogjeri ◽  
Cameron C. Wick ◽  
Jonathan L. McJunkin ◽  
Craig A. Buchman ◽  
...  
Keyword(s):  
Pure Tone ◽  
Signal To Noise Ratio ◽  
Case Series ◽  
Low Frequency ◽  
Electrode Array ◽  
Hearing Preservation ◽  
X Rays ◽  
Case Volume ◽  
Pure Tone Average ◽  
Academic Center

Objective To explore the immediate and 1-year outcomes of patients who underwent implantation with the slim modiolar electrode (SME). Study Design Consecutive case series with chart review. Setting Tertiary referral academic center. Subject and Methods Between May 2016 and August 2018, a total of 326 cochlear implantations (CIs) were performed. Intraoperative x-rays were performed in all cases to identify tip rollovers. Scalar location was identified for 76 CIs that had postoperative computed tomography reconstructions. Speech outcomes were measured at 3, 6, and 12 months with consonant-nucleus-consonant word and AzBio sentences in quiet and noise (+10-dB signal-to-noise ratio). Preservation of hearing was defined as maintaining a low-frequency pure tone average ≤80 dB at 250 and 500 Hz. Results Among 326 CIs, 23 (7%) had tip rollovers. Postoperative reconstructions revealed 5 of 76 (6.6%) scalar translocations. A subset of 177 cases met criteria for evaluation of speech perception scores. The marginal mean differences between presurgery and 12 months for speech tests were as follows: consonant-nucleus-consonant, 43.7 (95% CI, 39.8-47.6); AzBio in quiet, 49.7 (95% CI, 44.9-54.4); and AzBio in noise, 29.9 (95% CI, 25.2-34.7). Sixty-one patients were identified with preservable hearing (low-frequency pure tone average ≤80 dB), and 12 of 61 (20%) preserved hearing at 1 year. Conclusion CI with SME provides reliable scala tympani insertion in a consistent perimodiolar position. An initially increased tip rollover rate improved with case volume and sheath design improvement. For long-term outcomes, speech performance was comparable to that of other cochlear implants. While hearing preservation for the SME may be better than prior perimodiolar electrodes, consistent outcomes are unlikely.

scholarly journals Influence of Erbium Doping on Dielectric Properties of Zinc Borotellurite Glass System

2016 ◽  
Vol 846 ◽  
pp. 161-171 ◽  
Author(s):  
Siti Shafinas Zulkefly ◽  
Halimah Mohamed Kamari ◽  
Muhammad Nor Azlan Abdul Azis ◽  
Wan Mohd Daud Wan Yusoff
Keyword(s):  
Dielectric Properties ◽  
Molar Volume ◽  
Structural Changes ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Xrd Analysis ◽  
Glass System ◽  
Response Measurement ◽  
Xrd Pattern ◽  
Higher Temperature

Glasses of the system {[ (TeO2)70 (B2O3)30]70 (ZnO)30}100-y (Er2O3)y containing different concentration of Er2O3 (ranging from 0 to 5 mol %) was prepared from melt-quenching technique. The structural changes were studied by XRD analysis and FTIR analysis. The XRD pattern shows the glasses are amorphous. The higher concentration of Er2O3, the more unit of TeO3 would transform to TeO4 and formation of B-O vibrational groups. The density and molar volume was obtained attribute to non-bridging oxygen (NBO) and are found the density and molar volume of the glass system are increasing. The densities range from 3630 kg/m3 to 3960 kg/m3. The dielectric constant ε’ and dielectric loss factor ε’’ which were characterized in the frequency range 10-2 – 106 Hz over temperature range 50°C – 200 °C, show a larger value at lower frequency and higher temperature (above 110°C ). The results of dielectric response measurement show that interfacial polarization at low frequency, and orientation polarization at intermediate and high frequency.Keywords: Dielectric properties; Activation Energy; Rare Earth; Polarization; Non-Bridging Oxygen;

Effects of skeletal muscle anisotropy on induced currents from low frequency magnetic fields

2011 ◽  
Vol 56 (3) ◽  
pp. 879-879
Author(s):  
Nikolaos J Tachas ◽  
Theodoros Samaras ◽  
Konstantinos Baskourelos ◽  
John N Sahalos
Keyword(s):  
Skeletal Muscle ◽  
Magnetic Fields ◽  
Low Frequency ◽  
Induced Currents

scholarly journals Extra- and Intracochlear Electrocochleography in Cochlear Implant Recipients

2015 ◽  
Vol 20 (5) ◽  
pp. 339-348 ◽  
Author(s):  
Adrian Dalbert ◽  
Flurin Pfiffner ◽  
Christof Röösli ◽  
Konrad Thoele ◽  
Jae Hoon Sim ◽  
...  
Keyword(s):  
Cochlear Implant ◽  
Middle Ear ◽  
Cochlear Implantation ◽  
Low Frequency ◽  
Electrode Array ◽  
Postoperative Phase ◽  
Residual Hearing ◽  
Middle Ear Effusion ◽  
Cochlear Function ◽  
Ear Effusion

Objective: To monitor cochlear function by extra- and intracochlear electrocochleography (ECoG) during and after cochlear implantation and thereby to enhance the understanding of changes in cochlear function following cochlear implantation surgery. Methods: ECoG responses to acoustic stimuli of 250, 500 and 1,000 Hz were recorded in 9 cochlear implant recipients with presurgical residual hearing. During surgery extracochlear ECoG recordings were performed before and after insertion of the cochlear implant electrode array. After insertion of the electrode array, intracochlear ECoG recordings were conducted using intracochlear electrode contacts as recording electrodes. Intracochlear ECoG recordings were performed up to 6 months after implantation. ECoG findings were correlated with findings from audiometric tests. Results: Extra- and intracochlear ECoG responses could be recorded in all subjects. Extracochlear ECoG recordings during surgery showed moderate changes. Loss or reduction of the ECoG signal at all three frequencies did not occur during cochlear implantation. During the first week following surgery, conductive hearing loss, due to middle ear effusion, led to a decrease in intracochlear ECoG signal amplitudes. This was not attributable to changes of cochlear function. All persistent reductions in ECoG response magnitude after normalization of the tympanogram occurred during the first week following implantation. Thresholds of ECoG signals were at or below hearing thresholds in all cases. Conclusion: Gross intracochlear trauma during surgery appears to be rare. In the early postoperative phase the ability to assess cochlear status by ECoG recordings was limited due to the regular occurrence of middle ear effusion. Still, intracochlear ECoG along with tympanogram recordings suggests that any changes of low-frequency cochlear function occur mainly during the first week after cochlear implantation. ECoG seems to be a promising tool to objectively assess changes in cochlear function in cochlear implant recipients and may allow further insight into the mechanisms underlying the loss of residual hearing.

Study of Inhomogeneities in Non-Magnetic Tubes by Means of a Contactless Inductive Technique

2008 ◽  
Vol 587-588 ◽  
pp. 258-262 ◽  
Author(s):  
J. Íñiguez ◽  
V. Raposo ◽  
Pablo Hernández-Gómez
Keyword(s):  
Skin Effect ◽  
Low Frequency ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Simple Manner ◽  
Metal Coatings ◽  
Magnetic Screening ◽  
Induced Currents ◽  
Non Destructive

An accurate technique for contact-less measurement of resistivity in non-magnetic conductive tubes has been developed. It is intended for application in non-destructive testing (NDT) in tube manufacturing by simple study of the induced currents. Inhomogeneities or minimal imperfections in the tube thickness are immediately detected. This measuring technique is also suitable for determining the thickness of very thin metal coatings on non-conductive tubes. The experimental setup corresponds to an electrical transformer, the tube being the core. A first coil is placed around the tube under test, whereas the detecting coil is placed inside it. The study of the magnetic screening caused by the currents induced in the tube, allows its conductivity to be determined. The use of low frequency guarantees the almost complete absence of the skin effect in such a way that the results are obtained in a very simple manner. The method is based on the determination of the phase angle of the complex mutual inductance between the two coils working under low frequency conditions.

Impact of Electric Stimulation on Residual Hearing

2015 ◽  
Vol 26 (08) ◽  
pp. 732-740 ◽  
Author(s):  
Margaret T. Dillon ◽  
Andrea L. Bucker ◽  
Marcia C. Adunka ◽  
English R. King ◽  
Oliver F. Adunka ◽  
...  
Keyword(s):  
Cochlear Implant ◽  
Electric Stimulation ◽  
Bone Conduction ◽  
Low Frequency ◽  
Electrode Array ◽  
Hearing Preservation ◽  
Acoustic Stimulation ◽  
First Year ◽  
Residual Hearing ◽  
Listening Experience

Background: Candidacy criteria for cochlear implantation are expanding to include patients with substantial low-to-mid frequency hearing sensitivity. Postoperative hearing preservation has been achieved in cochlear implant recipients, though with variable outcomes. Previous investigations on postoperative hearing preservation outcomes have evaluated intraoperative procedures. There has been limited review as to whether electric stimulation influences hearing preservation. Purpose: The purpose of this analysis was to evaluate whether charge levels associated with electric stimulation influence postoperative hearing preservation within the first year of listening experience. Research Design: Retrospective analysis of unaided residual hearing and charge levels. Study Sample: Twenty-eight cochlear implant recipients with postoperative residual hearing in the operative ear and at least 12 mo of listening experience with electric-acoustic stimulation (EAS). Data Collection and Analysis: Assessment intervals included initial cochlear implant activation, initial EAS activation, and 3-, 6-, and 12-mo postinitial EAS activation. A masked low-frequency bone-conduction (BC) pure-tone average (PTA) was calculated for all participants at each assessment interval. Charge levels for each electrode were determined using the most comfortable loudness level and pulse width values. Charge levels associated with different regions of the electrode array were compared to the change in the low-frequency BC PTA between two consecutive intervals. Results: Charge levels had little to no association with the postoperative change in low-frequency BC PTA within the first year of listening experience. Conclusions: Electric charge levels do not appear to be reliably related to the subsequent loss of residual low-frequency hearing in the implanted ear within the first year of EAS listening experience.

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.

scholarly journals Surface impedance of electromagnetic field excited by a grounded horizontal antenna in the Earth–ionosphere waveguide

2019 ◽  
pp. 181-189
Author(s):  
E. D. Tereshchenko ◽  
P. E. Tereshchenko
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Surface Impedance ◽  
Low Frequency ◽  
Wave Impedance ◽  
Skin Layer ◽  
Skin Depth ◽  
Plane Waveguide ◽  
The Earth ◽  
Horizontal Antenna

Analytical formulas for the tangential components of extremely-low-frequency (ELF) electromagnetic field in the Earth–ionosphere plane waveguide excited by a grounded linear horizontal antenna are obtained. The behavior of surface impedance is studied as a function of electrodynamic characteristics of the waveguide and the distance from the source. It is shown that surface impedance coincides with the plane wave impedance on the Earth’s surface at distances from the source larger than the skin depth provided that the skin layer is thinner than double the waveguide’s height. The influence of the ionosphere on the amplitude of the ELF and lower-frequency magnetic field and, thus, on the impedance at the distances shorter than two ionospheric heights is theoretically substantiated. This type of effect was observed in the experiments conducted on the Kola Peninsula where the low conductivity of the Earth allowed the detection of the effect of the ionosphere on the amplitude of the magnetic field in the low-frequency band.

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