scholarly journals Influence of the probe dimensions on the display of the low-frequency dispersion of the earth’s electromagnetic properties for measure-ments in marine waters up to 100 m deep

2020 ◽  
Vol 43 (3) ◽  
pp. 325-338
Author(s):  
E. V. Ageenkov ◽  
A. A. Sitnikov ◽  
E. N. Vodneva
Keyword(s):  
Eddy Currents ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Water Layer ◽  
Conducting Medium ◽  
Transient Signal ◽  
Electromagnetic Properties ◽  
Time Range ◽  
Electric Line ◽  
Different Dimensions

The purpose of the study is to show the effect of the probe dimensions on the display of the low-frequency dispersion of the geological formations’ electromagnetic properties in transient measurements by electric lines in the axial area of the source for the water areas up to 100 m deep. The study analyzes the change in the transient signal, the finite difference, and the transform (the ratio of the above two) as a function of the length of the source (a horizontal grounded electric line (AB) 50 to 2,000 m), the receiver (a three-electrode electric line (MON) 50 to 2,000 m), and the distance between their centers (spacing) 100 to 4,000 m. The values obtained from the conductive and conductive polarizing models are compared for the identical probes installed at the same depth. The grounded electric line is located within the conducting medium with a conductive polarizable base. The conducting medium is associated with the seawater thickness in the marine shelves up to 100 m deep. The conductive polarizable base is a geological environment (earth) covered with a layer of water. The polarizability of the base is registered by introducing frequency-dependent electrical resistivity by the Cole-Cole formula. The calculations show the display of different transient components associated with the transient buildup and the earth’s low-dispersion properties caused by both galvanic and eddy currents. These components manifest themselves differently for the probes with different dimensions of the source line, receiving line, and spacing. Based on the calculations, it can be argued that in the time range from 1 ms to 16 s, at the probes that have different dimensions and are immersed in the water layer up to 100 m thick, the signal changes depending on the immersion depth for “small” installations (AB of 50 and 100 m), while there is no such dependence for the rest of the probes used in the calculations (AB of 250, 500, 1,000, and 2,000 m).

scholarly journals TRANSIENT SIGNAL IN THE AXIAL DOMAIN OF THE ELECTRIC LINE FOR GEOELECTRIC CONDITIONS OF THE OFFSHORE AREA

2021 ◽  
Vol 2 (1) ◽  
pp. 316-322
Author(s):  
Evgenii V. Ageenkov
Keyword(s):  
Transient Process ◽  
Water Layer ◽  
Transient Signal ◽  
Axial Region ◽  
Offshore Area ◽  
Electric Line

The behavior of the transient process (TP) signal in the axial region of the electric line located in the water layer of the sea shelf is described.

Magnetic Permeability and Relaxation Frequency in High Frequency Magnetic Materials.

2001 ◽  
Vol 674 ◽  
Author(s):  
M.I. Rosales ◽  
H. Montiel ◽  
R. Valenzuela
Keyword(s):  
High Frequency ◽  
Domain Walls ◽  
Magnetocrystalline Anisotropy ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Anisotropy Constant ◽  
Relaxation Frequency ◽  
Resonance Relaxation ◽  
Frequency Behavior

ABSTRACTAn investigation of the frequency behavior of polycrystalline ferrites is presented. It is shown that the low frequency dispersion (f < 10 MHz) of permeability is associated with the bulging of pinned domain walls, and has a mixed resonance-relaxation character, closer to the latter. It is also shown that there is a linear relationship between the magnetocrystalline anisotropy constant, K1, and the relaxation frequency. The slope of this correlation depends on the grain size. Such a relationship could allow the determination of this basic parameter from polycrystalline samples.

Volume low-frequency dispersion in a semi-insulating system

1988 ◽  
Vol 23 (2) ◽  
pp. 209-213 ◽  
Author(s):  
A.K. Jonscher ◽  
L. Levesque
Keyword(s):  
Low Frequency ◽  
Frequency Dispersion

scholarly journals The Hybrid FEM-DBCI for the Solution of Open-Boundary Low-Frequency Problems

Mathematics ◽  
2021 ◽  
Vol 9 (16) ◽  
pp. 1968
Author(s):  
Giovanni Aiello ◽  
Salvatore Alfonzetti ◽  
Santi Agatino Rizzo ◽  
Nunzio Salerno
Keyword(s):  
Integral Equation ◽  
Eddy Currents ◽  
Computing Time ◽  
Low Frequency ◽  
Dirichlet Condition ◽  
Open Boundary ◽  
Coordinate Transformations ◽  
External Layer ◽  
Electromagnetic Problems ◽  
Electrostatic Fields

This paper describes a particular use of the hybrid FEM-DBCI, for the computation of low-frequency electromagnetic fields in open-boundary domains. Once the unbounded free space enclosing the system has been truncated, the FEM is applied to the bounded domain thus obtained, assuming an unknown Dirichlet condition on the truncation boundary. An integral equation is used to express this boundary condition in which the integration surface is selected in the middle of the most external layer of finite elements, very close to the truncation boundary, so that the integral equation becomes quasi-singular. The method is described for the computation of electrostatic fields in 3D and of eddy currents in 2D, but it is also applicable to the solution of other kinds of electromagnetic problems. Comparisons are made with other methods, concluding that FEM-DBCI is competitive with the well-known FEM-BEM and coordinate transformations for what concerns accuracy and computing time.

Theory of the ferroelectric Mott-Hubbard phase in organic conductors

2002 ◽  
Vol 12 (9) ◽  
pp. 149-152
Author(s):  
S. Brazovskii
Keyword(s):  
Activation Energy ◽  
Phase Transitions ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Organic Conductors ◽  
The State ◽  
Charge Disproportionation ◽  
Subsequent Phase

Recently the ferroelectric FE anomaly (Nad, Monceau, et al.) followed by the charge disproportionation CD (Brown, et al) have been discovered in ($TMTTF)_2X$ compounds. A theory of the combined Mott-Hubbard state describes both effects by interference of the build-in nonequivalence of bonds and the spontaneous one of sites. The state gives rise to three types of solitons: $\pi -$ solitons (holons) are observed via the activation energy A in conductivity G; noninteger $\alpha -$ solitons provide the frequency dispersion of the FE response; combined spin-charge solitons determine $G(T)$ below subsequent phase transitions. The optical edge lies well below the conductivity gap 2A; the critical FE mode coexists with a combined electron-phonon resonance and a phonon antiresonance. The CD and the FE can exists hiddenly even in the Se subfamily giving rise to the unexplained yet low frequency optical peak, the enhanced pseudogap and traces of phonons activation.

scholarly journals Percolative Composites with Carbon Nanohorns: Low-Frequency and Ultra-High Frequency Response

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1848 ◽  
Author(s):  
Olga V. Sedelnikova ◽  
Kseniya I. Baskakova ◽  
Artem V. Gusel’nikov ◽  
Pavel E. Plyusnin ◽  
Lyubov G. Bulusheva ◽  
...  
Keyword(s):  
Arc Discharge ◽  
Thermo Gravimetric Analysis ◽  
Low Frequency ◽  
Graphite Powder ◽  
Electromagnetic Properties ◽  
Gravimetric Analysis ◽  
Carbon Nanohorns ◽  
High Frequency Response ◽  
High K Materials ◽  
Graphite Rods

We systematically studied the electromagnetic properties of carbon nanohorns (CNHs) and polystyrene composites filled with CNHs in static regime, low frequency and microwave regions. CNHs were synthesized using the direct current arc-discharge method using solid graphite rods and graphite rods filled by melamine mixed with graphite powder. Transmission electron microscopy and thermo-gravimetric analysis showed that CNH agglomerates are the main product, while the addition of melamine promotes the formation of graphite balls. Graphitic contamination causes the internal leakage of inter-agglomerate capacity, lowering the permittivity and enhancing the conductivity of composites. The permittivity of CNH/polystyrene composites increases with the filler fraction, and near the dielectric threshold electromagnetic characteristics of the composites exhibit critical behaviour. Our results suggest that CNHs with relatively high values of permittivity and contact resistance could be used as high-k materials.

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