Scale invariance of the low‐frequency electrical properties of inhomogeneous materials

Geophysics ◽  
1981 ◽  
Vol 46 (7) ◽  
pp. 1057-1059 ◽  
Author(s):  
Morrel H. Cohen
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Scale Invariance ◽  
Low Frequency ◽  
Inhomogeneous Material ◽  
Inhomogeneous Materials ◽  
Low Frequencies ◽  
Bulk Properties ◽  
Grain Sizes

We show that the electrical properties of an inhomogeneous material are invariant to the scale of the inhomogeneity at low frequencies when they are determined solely from local bulk properties, Thus the pore and grain sizes of rocks cannot be ascertained by low‐frequency conductivity and dielectric constant measurements.

UNIVERSAL MULTIFRACTAL CHARACTERIZATION AND SIMULATION OF SPEECH

1992 ◽  
Vol 02 (03) ◽  
pp. 715-719
Author(s):  
CHRIS LARNDER ◽  
NICOLAS DESAULNIERS-SOUCY ◽  
SHAUN LOVEJOY ◽  
DANIEL SCHERTZER ◽  
CLAUDE BRAUN ◽  
...  
Keyword(s):  
Time Scale ◽  
Scale Invariance ◽  
Characteristic Time ◽  
Low Frequency ◽  
Characteristic Time Scale ◽  
Low Frequencies ◽  
Universal Behavior ◽  
Nonlinear Mixing

In the 1970's it was found that; for low frequencies (<10 Hz), speech is scaling: it has no characteristic time scale. Now such scale invariance is associated with multiscaling statistics, and multifractal structures. Just as Gaussian noises frequently arise because they are generically produced by sums of many independent noise processes, scaling noises have an analogous universal behavior arising from nonlinear mixing of processes. We show that low frequency speech is consistent with these ideas, and use the measured parameters to produce stochastic speech simulations which are strikingly similar to real speech.

The Influence of Ion Beam Implantation on Electrical Properties of Polycrystalline MnNiCuFeO

1992 ◽  
Vol 279 ◽  
Author(s):  
Li Binbin ◽  
Tan Hui ◽  
Han Ying ◽  
Tao Wei ◽  
Lin Chenglu
Keyword(s):  
Electrical Properties ◽  
Grain Boundaries ◽  
Boundary Effect ◽  
Ion Beam ◽  
Low Frequency ◽  
Bulk Properties ◽  
Spreading Resistance ◽  
Impedance Analyzer ◽  
Ion Beam Implantation ◽  
Grain Boundary Effect

ABSTRACTPolycrystalline MnNiCuFeO was implanted by B+, P+ and Si+ ion beams and thermally annealed. The structure and electrical properties of the sample were measured using SEM, Microprobe (MP), Low Frequency Impedance Analyzer (LFIA) and Spreading Resistance Probe (SRP). The results show that the resistance of grain boundaries is much higher than that of grains. The spreading resistance of the implanted samples is lower by factor of 2 than that of the unimplanted ones. The ratio of the real part Rs (grain effect) to imaginary part Xs (grain boundary effect) decreases with ion beam implantation. From these results, we came to the conclusion that the behavior of the grain boundaries is important to the bulk properties of polycrystalline MnNiCuFeO.

Microstructure and Electrical Properties of Calcium Copper Titanate Ceramics

2007 ◽  
Vol 561-565 ◽  
pp. 551-555 ◽  
Author(s):  
Lai Jun Liu ◽  
Hui Qing Fan
Keyword(s):  
Electrical Properties ◽  
Dielectric Permittivity ◽  
High Frequency ◽  
Low Frequency ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Cell Parameters ◽  
Grain Sizes ◽  
Calcium Copper Titanate ◽  
Titanate Ceramics

The effect of stoichiometry, i.e. Ca/Cu ratios (CaCu3xTi4O12, x = 0.8, 0.9, 1.0, 1.1 and 1.2) on the microstructure and electrical properties was investigated. The grain sizes of CaCu3xTi4O12 composition increased sharply with the increase of copper, from ~1 μm with x = 0.8 to ~50 μm with x = 1.2. The real part of dielectric permittivity changed dramatically, the pellet with x = 1.0 had the highest dielectric permittivity ~160, 000 at 1 kHz. Furthermore, the dielectric permittivity of all pellets was impressively large values (between 10, 000 to 1, 000,000 at 100 Hz) and was nearly constant over a wide frequency range between 100 Hz to ~100 MHz. However, the dielectric permittivity of CaCu3xTi4O12 composition is not consistent with the amount of copper and cell parameters and grain sizes. Impedance spectroscopy exhibited that the CaCu3xTi4O12 composition had two semicircle at least at high frequency (~ 107 Hz) and low frequency (<100 Hz), respectively. The grain and grain boundary of the compositions had different impedance and relaxation behavior.

Changes in the Electrical Properties of Natural Rubber/Carbon Black Compounds during Vulcanization

1958 ◽  
Vol 31 (3) ◽  
pp. 631-649 ◽  
Author(s):  
H. Desanges ◽  
R. Chasset ◽  
P. Thirion
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Natural Rubber ◽  
Direct Current ◽  
Colloidal Particles ◽  
Low Frequency ◽  
Frequency Measurement ◽  
Point Of View ◽  
Sudden Decrease

Abstract To conclude, let us sum up the advantages of direct current or low frequency measurement of the electrical properties of natural rubber compounds, when operating inside the mold in which vulcanization is occurring. In this way, it is possible to follow the changes in properties during heating or vulcanization more closely and accurately than when operating with samples outside the mold. An orientation of the colloidal structure of compounds above 10% by volume of MPC black is thus easily demonstrated. The dielectric properties of the compounds depend, in this case, on the size of the samples, since this orientation is a function of the dimensions, especially of the thickness of the molded compound. On the other hand, from the behavior of vulcanizable and nonvulcanizable compounds, a distinction may be made between the respective effects of both the vulcanization and the special state of agglomeration of the black colloidal particles in the compounds. This ‘structure’ of the black affects apparently both the losses and the dielectric constant through an electronic polarization phenomenon which can, in principle, be analyzed through the Maxwell-Wagner general theory of heterogeneous dielectrics. The effect of ‘structure’ on low-frequency losses depends essentially upon the nature and ratio of the black and varies like direct current conductivity. This ‘structure’ seems to be influenced also—although to a much smaller extent—by vulcanization, since the level of losses during heating is lower than with a nonvulcanizable compound containing the same ratio of black. When this ratio does not exceed 10% by volume, vulcanization governs the dielectric properties more directly, both by a fixation of polar sulfur to molecular chains, and by an ionic dissociation of vulcanizing ingredients. In the range of this study the only effect of molecular polarization is a rather limited increase of the dielectric constant; the losses are not affected. The sudden decrease of losses noted during the vulcanization of a gum compound is explained by a disappearance of the ions formed by the vulcanization reactions. This ionic polarization of the Maxwell-Wagner type plays no marked part in Compounds containing large amounts of black, no doubt because the ions are adsorbed by the black. By extending this study, as it is hoped, into the field of radio frequencies, it should be possible to improve the theory of the evolution of dielectric properties during vulcanization. From the practical point of view, such work would provide useful experimental data for a rational application of radio-vulcanization.

Low‐frequency electrical properties

Geophysics ◽  
1985 ◽  
Vol 50 (12) ◽  
pp. 2492-2503 ◽  
Author(s):  
G. R. Olhoeft
Keyword(s):  
Electrical Properties ◽  
Low Frequency ◽  
Induced Polarization ◽  
Toxic Waste ◽  
Petroleum Exploration ◽  
Low Frequencies ◽  
Oxidation Reduction ◽  
Metallic Mineral ◽  
Active Chemical ◽  
Nonlinear Character

In the interpretation of induced polarization data, it is commonly assumed that metallic mineral polarization dominantly or solely causes the observed response. However, at low frequencies, there is a variety of active chemical processes which involve the movement or transfer of electrical charge. Measurements of electrical properties at low frequencies (such as induced polarization) observe such movement of charge and thus monitor many geochemical processes at a distance. Examples in which this has been done include oxidation‐reduction of metallic minerals such as sulfides, cation exchange on clays, and a variety of clay‐organic reactions relevant to problems in toxic waste disposal and petroleum exploration. By using both the frequency dependence and nonlinear character of the complex resistivity spectrum, these reactions may be distinguished from each other and from barren or reactionless materials.

Enhanced Dielectric and Electrical Properties in Polyurethane Composites with Graphene Nanosheets

2018 ◽  
Vol 917 ◽  
pp. 117-121 ◽  
Author(s):  
Ardimas ◽  
Chatchai Putson
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Graphene Nanosheets ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Polyurethane Elastomers ◽  
Solution Casting Method ◽  
Lcr Meter ◽  
Polyurethane Composites ◽  
Polyurethane Matrix

The Electrical properties of polyurethane (PU) filled with graphene nanosheets (GRN) at low frequency is investigated. In last decade, polyurethane elastomers have attracted attention in transducer and actuator applications. The dielectric constant is one of the key factors for increasing actuator ability. Graphene nanosheets as conducting fillers have to be filled to increase the dielectric constant. In order to prove this idea, polyurethane composites with various graphene contents have been characterized by SEM and DSC. And their electrical capability has been measured at various frequencies of 101-104 by using LCR meter. To gain the films, polyurethane composites filled with various graphene contents were prepared by solution casting method. The results showed a well homogenous dispersion of the graphene filler in the polyurethane matrix. In addition, it was found that the glass transition temperature (Tg) of the PU/GRN increase as the content of filler increased and it can be affected the interfacial polarization between PU matrix with the GRN fillers. Therefore, it is found that graphene in the polyurethane matrix exhibit high enhanced the electrical properties and the optimal dielectric constant at 2wt% graphene of 9.74.

Tuning the mechanical and dielectric properties of zinc incorporated hydroxyapatite

2020 ◽  
Vol 16 ◽  
Author(s):  
Alliya Qamar ◽  
Rehana Zia ◽  
Madeeha Riaz
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bone Growth ◽  
Healing Process ◽  
Secondary Phase ◽  
Chemical Precipitation ◽  
Hexagonal Structure ◽  
Precipitation Method ◽  
Low Frequencies ◽  
A Minor

Background: Hydroxyapatite is similar to bone mineral in chemical composition, has good biocompatibility with host tissue and bone. Objective: This work aims to tailor the mechanical and dielectric properties of hydroxyapatite with zinc sudstitution, to improve wearability of implant and accelerate the healing process. Method: Pure and zinc incorporated hydroxyapatite Ca10(PO4)6(OH)2 samples have been successfully prepared by means of the chemical precipitation method. Results: The results showed that hydroxyapatite(Hap) having hexagonal structure was the major phase identified in all the samples. It was found that secondary phase of β-tricalcium phosphate (β-TCP) formed due to addition of Zinc resulting in biphasic structure BCP (Hap + β-TCP). A minor phase of ZnO also formed for higher concentration of Zn (Zn ≥ 2mol%) doping. It was found that the Zn incorporation to Hap enhanced both mechanical and dielectric properties without altering the bioactive properties. The microhardness increased upto 0.87 GPa for Zn concentration equal to 1.5mol%, which is comparable to the human bone ~0.3 - 0.9 GPa. The dielectric properties evaluated in the study showed that 1.5 mol% Zn doped hydroxyapatite had highest dielectric constant. Higher values of dielectric constant at low frequencies signifies its importance in healing processes and bone growth due to polarization of the material under the influence of electric field. Conclusion: Sample Z1.5 having 1.5 mol% Zn doping showed the most optimized properties suitable for bone regeneration applications.

scholarly journals Earless toads sense low frequencies but miss the high notes

2017 ◽  
Vol 284 (1864) ◽  
pp. 20171670 ◽  
Author(s):  
Molly C. Womack ◽  
Jakob Christensen-Dalsgaard ◽  
Luis A. Coloma ◽  
Juan C. Chaparro ◽  
Kim L. Hoke
Keyword(s):  
High Frequency ◽  
Species Differences ◽  
Low Frequency ◽  
Auditory Brainstem ◽  
Low Frequencies ◽  
Hearing Sensitivity ◽  
Sensory Pathways ◽  
Airborne Sound ◽  
Vibrational Sensitivity ◽  
Species Specific

Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment. We used auditory brainstem recordings to compare hearing and vibrational sensitivity among 10 species (six eared, four earless) within the Neotropical true toad family (Bufonidae). We found that species lacking middle ears are less sensitive to high-frequency sounds, however, low-frequency hearing and vibrational sensitivity are equivalent between eared and earless species. Furthermore, extratympanic hearing sensitivity varies among earless species, highlighting potential species differences in extratympanic hearing mechanisms. We argue that ancestral bufonids may have sufficient extratympanic hearing and vibrational sensitivity such that earless lineages tolerated the loss of high frequency hearing sensitivity by adopting species-specific behavioural strategies to detect conspecifics, predators and prey.

A waveform inversion technique for measuring elastic wave attenuation in cylindrical bars

Geophysics ◽  
1992 ◽  
Vol 57 (6) ◽  
pp. 854-859 ◽  
Author(s):  
Xiao Ming Tang
Keyword(s):  
Elastic Wave ◽  
Wave Attenuation ◽  
Waveform Inversion ◽  
Finite Size ◽  
Low Frequency ◽  
Frequency Range ◽  
Multiple Reflections ◽  
Low Frequencies ◽  
The Time Domain ◽  
Attenuation Values

A new technique for measuring elastic wave attenuation in the frequency range of 10–150 kHz consists of measuring low‐frequency waveforms using two cylindrical bars of the same material but of different lengths. The attenuation is obtained through two steps. In the first, the waveform measured within the shorter bar is propagated to the length of the longer bar, and the distortion of the waveform due to the dispersion effect of the cylindrical waveguide is compensated. The second step is the inversion for the attenuation or Q of the bar material by minimizing the difference between the waveform propagated from the shorter bar and the waveform measured within the longer bar. The waveform inversion is performed in the time domain, and the waveforms can be appropriately truncated to avoid multiple reflections due to the finite size of the (shorter) sample, allowing attenuation to be measured at long wavelengths or low frequencies. The frequency range in which this technique operates fills the gap between the resonant bar measurement (∼10 kHz) and ultrasonic measurement (∼100–1000 kHz). By using the technique, attenuation values in a PVC (a highly attenuative) material and in Sierra White granite were measured in the frequency range of 40–140 kHz. The obtained attenuation values for the two materials are found to be reliable and consistent.

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