Electrical conductance in a porous medium

Geophysics ◽  
1983 ◽  
Vol 48 (9) ◽  
pp. 1258-1268 ◽  
Author(s):  
A. E. Bussian
Keyword(s):  
Porous Medium ◽  
Electrical Properties ◽  
Experimental Work ◽  
Electrical Conductance ◽  
Low Frequency ◽  
Water Model ◽  
Rock Matrix ◽  
Frequency Limit ◽  
Proposed Model ◽  
Two Component

The Hanai‐Bruggeman equation is applied to a model of a conductive rock matrix immersed in water. The result is a general two‐component equation which relates the electrical properties of a formation to the electrical properties of the rock matrix and the water at any frequency. The low‐frequency limit is compared with previous theoretical and experimental work on sand formations. From a comparison of the three‐resistor model of Wyllie and Southwick, the Waxman‐Smits model, the dual water model of Clavier et al (1977) and the proposed model, it is found that the only representation which is viable, conceptually sound, and in agreement with experiment, is the last one.

A new procedure for processing strong-motion earthquake signals

1982 ◽  
Vol 72 (2) ◽  
pp. 643-661
Author(s):  
S. Shyam Sunder ◽  
Jerome J. Connor
Keyword(s):  
United States ◽  
Filter Design ◽  
Response Spectrum ◽  
Low Frequency ◽  
Strong Motion ◽  
Sampling Period ◽  
Frequency Limit ◽  
Processing Scheme ◽  
Proposed Model ◽  
Band Pass

Abstract A new procedure for routinely processing strong-motion earthquake signals using state-of-the-art filter design and implementation techniques is presented. The model, shown to be both accuratet and efficient, is sufficiently flexible so that the signal sampling period and filter parameters can be easily varied. A comparison of results from the existing United States model (Trifunac and Lee, 1973) and the proposed model show significant differences in the ground motion and response spectrum characteristics for the same set of filter limits. Drifts in integrated velocity and displacement characteristics and theoretically incorrect asymptotic behavior of response spectrum curves arising out of the existing United States processing scheme have been eliminated. In addition to the importance of appropriately selecting a low-frequency limit for band-pass filtering the signals, this work demonstrates the sensitivity of the acceleration trace to the particular choice of a high-frequency limit.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Onset of size effects in lattice thermal conductivity and lifetime of low-frequency thermal phonons

2012 ◽  
Vol 1404 ◽  
Author(s):  
A.A. Maznev
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Size Effects ◽  
Lattice Thermal Conductivity ◽  
Low Frequency ◽  
Square Root ◽  
Relaxation Rates ◽  
Frequency Limit ◽  
Conductivity Of Thin Films ◽  
Closed Form Formula

ABSTRACTThe onset of size effects in phonon-mediated thermal transport along a thin film at temperatures comparable or greater than the Debye temperature is analyzed theoretically. Assuming a quadratic frequency dependence of phonon relaxation rates in the low-frequency limit, a simple closed-form formula for the reduction of the in-plane thermal conductivity of thin films is derived. The effect scales as the square root of the film thickness, which leads to the prediction of measurable size-effects even at “macroscopic” distances ~100 μm. However, this prediction needs to be corrected to account for the deviation from the ω−2 dependence of phonon lifetimes at sub-THz frequencies due to the transition from Landau-Rumer to Akhiezer mechanism of phonon dissipation.

Numerical simulation of seismic waves in porous media components

2021 ◽  
Vol 9 (1) ◽  
pp. 4-30
Author(s):  
M. Azeredo ◽  
◽  
V. Priimenko ◽  
Keyword(s):  
Numerical Simulation ◽  
Porous Medium ◽  
High Frequency ◽  
Seismic Waves ◽  
Computational Algorithm ◽  
Low Frequency ◽  
Physical Parameters ◽  
Mathematical Algorithm ◽  
Biot Equations ◽  
Attenuation And Dispersion

This work presents a mathematical algorithm for modeling the propagation of poroelastic waves. We have shown how the classical Biot equations can be put into Ursin’s form in a plane-layered 3D porous medium. Using this form, we have derived explicit for- mulas that can be used as the basis of an efficient computational algorithm. To validate the algorithm, numerical simulations were performed using both the poroelastic and equivalent elastic models. The results obtained confirmed the proposed algorithm’s reliability, identify- ing the main wave events in both low-frequency and high-frequency regimes in the reservoir and laboratory scales, respectively. We have also illustrated the influence of some physical parameters on the attenuation and dispersion of the slow wave.

scholarly journals Nonlinear interaction between acoustic gravity waves

1996 ◽  
Vol 14 (3) ◽  
pp. 304-308 ◽  
Author(s):  
P. Axelsson ◽  
J. Larsson ◽  
L. Stenflo
Keyword(s):  
Gravity Waves ◽  
Nonlinear Interaction ◽  
Low Frequency ◽  
Resonant Interaction ◽  
Coupling Coefficients ◽  
Symmetric Form ◽  
Frequency Limit ◽  
Acoustic Gravity Waves

Abstract. The resonant interaction between three acoustic gravity waves is considered. We improve on the results of previous authors and write the new coupling coefficients in a symmetric form. Particular attention is paid to the low-frequency limit.

Determination of Electric and Magnetic Properties of Commercial LTCC Soft Ferrite Material

2011 ◽  
Vol 8 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Nelu Blaž ◽  
Andrea Marić ◽  
Goran Radosavljević ◽  
Nebojša Mitrović ◽  
Ibrahim Atassi ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Low Frequency ◽  
Hysteresis Loops ◽  
Frequency Range ◽  
Dispersion Parameters ◽  
Simple Method ◽  
Component Design ◽  
Microwave Engineering ◽  
Characterization Procedure

This paper offers an effective, accurate, and simple method for permittivity and permeability determination of an LTCC (low temperature cofired ceramic) ferrite sample. The presented research can be of importance in the fields of ferrite component design and application, as well as for RF and microwave engineering. The characterization sample is a stack of LTCC tapes forming a toroid. Commercially available ferrite tape ESL 40012 was used and standard LTCC processing was applied for the sample fabrication. For the first time, the electrical properties of a ferrite toroid sample of ESL 40012 LTCC ferrite tape is presented at various frequencies. The electrical properties of LTCC ferrite materials, permittivity and specific resistivity, are shown in a frequency range from 10 kHz to 1 MHz using the capacitive method. The hysteresis properties of this material are also determined. B-H hysteresis loops were measured applying a maximum excitation of 2 kA/m and frequencies of 50 Hz, 500 Hz, and 1000 Hz. Permeability is determined in the frequency range from 10 kHz to 1 GHz and a characterization procedure is divided in two segments, for low and high frequencies. Low frequency measurements (from 10 kHz to 1 MHz) are performed using LCZ meter and discrete turns of wire, while a short coaxial sample holder and vector network analyzer were used for the higher frequency range (from 300 kHz to 1 GHz). In addition, another important factor required for the practical design of devices is presented, the temperature variation of the permeability dispersion parameters.

scholarly journals A study of the influence produced by the dynamics of the working bodies of cotton-processing machines on the cotton fibre quality

2021 ◽  
Vol 1 (1 (109)) ◽  
pp. 68-76
Author(s):  
Fazil Veliev
Keyword(s):  
Porous Medium ◽  
Speed Of Sound ◽  
Raw Materials ◽  
Dynamic Compression ◽  
Dynamic Change ◽  
Static Compression ◽  
Gaseous Component ◽  
Multicomponent Media ◽  
Two Component ◽  
Working Bodies

Cotton mass is considered as a compressible porous two-component medium, consisting of a mixture of cotton fibres and air included in the porous medium, which is essential in dynamic treatment processes and requires consideration when planning technological modes. It was found that the speed of sound in multicomponent media significantly decreases with an increase in the content of the gaseous component. With a certain content of components, it can become less than in each of the components separately. This is due to the fact that with an increase in the content of the gaseous component, the density of the medium increases insignificantly, and the compressibility of air sharply decreases in the pores. As a result of the research, it was found that the value of the dynamic change in the density of cotton raw materials can significantly exceed its density during static compression. This kind of influence can have both adverse and desirable effects on the primary stage of cotton processing. The dynamic characteristics of raw cotton as an object of mechanical technology were studied. The values of the speed of sound as a function of the density of cotton raw materials were determined on the basis of the theory of a two-component porous medium. The types of the dynamic compression curve of raw cotton have been established. Experimental studies on the compressibility of raw cotton are generalized. From the analysis of the cleaning processing of fibres and seeds on cleaning machines, it follows that when assigning a technological processing mode, it is necessary to comply it with the value of the sound speed for a given density of raw materials. It is necessary to avoid such rates of penetration of the working bodies into raw materials that are commensurate with the speed of sound at a given raw material density. This local dramatic increase in cotton media characteristics is a significant cause of fibre damage

scholarly journals Structural and Electrical Properties of Sprayed In2S3 Films on ITO/Glass Substrate

2021 ◽  
Author(s):  
J. Koaib ◽  
N. Bouguila ◽  
M. Kraini ◽  
I. Halidou ◽  
K. Khirouni ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Indium Tin Oxide ◽  
Glass Substrate ◽  
Spray Pyrolysis Technique ◽  
Electrical Conductance ◽  
Average Crystallite Size ◽  
Chemical Spray Pyrolysis ◽  
Electrical Equivalent Circuit ◽  
Ito Glass

Abstract In2S3 thin films were grown on indium tin oxide (ITO) glass substrate by chemical spray pyrolysis technique at 360°C. The structural analysis of the deposited films shows a combination of tetragonal and cubic structures. The average crystallite size is about 25 nm. The electrical properties of In2S3 thin films have been investigated in a wide frequency (40Hz-100MHz) and temperature (400 K-660 K) ranges.We find that the electrical conductance of the In2S3 thin films is frequency and temperature dependent. The dc conductance shows a semi-conductor behavior for In2S3 films over the explored range of temperature and it follows the Arrhenius law with different activation energies. The variation of ac conductance and the frequency exponent `s’ are explained by the correlated barrier hopping (CBH) model. The Nyquist plots of impedance exhibit semicircle arcs and an electrical equivalent circuit has been suggested to interpret the impedance results.

Effects of director rotation relaxation on viscoelastic wave dispersion in nematic elastomer beams

2018 ◽  
Vol 24 (4) ◽  
pp. 1103-1115 ◽  
Author(s):  
Dong Zhao ◽  
Ying Liu
Keyword(s):  
Wave Motion ◽  
Relaxation Times ◽  
Low Frequency ◽  
Wave Dispersion ◽  
Frequency Limit ◽  
Anisotropic Parameter ◽  
Acoustic Design ◽  
Phase Velocities ◽  
Nematic Elastomer ◽  
Viscoelastic Wave

In this paper, the transverse wave dispersion in a nematic elastomer (NE) Timoshenko beam is studied by considering anisotropy and viscoelasticity of NEs in the low frequency limit. Firstly, the characteristic equations of wave motion in an NE beam are derived, and then numerically solved to obtain the corresponding phase velocities and attenuation factors. The influences of anisotropic parameter, director rotation and rubber relaxation times on the wave dispersion in an NE beam are discussed. Results show that unlike the situation in general isotropic viscoelastic beam, non-classical viscoelastic wave dispersion is found in NE beams. Geometric dispersion is restrained with the vanishing of cut-off frequencies for shear waves due to director rotation relaxation of NEs. This unique property promises prospective applications of NE beams in optic or acoustic design.

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