scholarly journals Three different types of electric field disturbances affecting equatorial ionosphere during a long‐duration prompt penetration event

2015 ◽  
Vol 120 (6) ◽  
pp. 4993-5008 ◽  
Author(s):  
D. Chakrabarty ◽  
Diptiranjan Rout ◽  
R. Sekar ◽  
R. Narayanan ◽  
G. D. Reeves ◽  
...  
Keyword(s):  
Electric Field ◽  
Equatorial Ionosphere ◽  
Long Duration ◽  
Different Types

Microstructure-Based Simulation of the Dielectric Properties of Polymer-Ceramic Composites for Capacitor Applications

2006 ◽  
Vol 949 ◽  
Author(s):  
Jeffrey P. Calame
Keyword(s):  
Electric Field ◽  
Polymer Matrix ◽  
Matrix Material ◽  
Realistic Model ◽  
Ceramic Composites ◽  
Internal Electric Field ◽  
Large Particles ◽  
Different Types ◽  
Model Spaces ◽  
Electrostatic Modeling

ABSTRACTResearch on the microstructure-based modeling of composite dielectrics for capacitor applications is described. Methods for predicting the composite dielectric permittivity and internal electric field distributions within the microstructure using finite difference quasi-electrostatic modeling are described, along with methods of generating realistic model spaces of particulate microstructures. An existing algorithm for generating random, monosized spheres-in-a-dielectric matrix model spaces is modified to allow the treatment of bimodal composites in which small particles are deliberately segregated into the spaces between large particles. Such composites can have substantially higher total volumetric filling fractions of particles, leading to higher composite permittivity. The variations in permittivity with the filling fractions of bimodal inclusions are studied with the new model, with cases covering three different types of polymer matrix material. The effect of the small particle additions on the electric field statistics within the polymer matrix is also explored.

The Hertzian Spectrum of Rubber and Its Micellar Constitution

1946 ◽  
Vol 19 (4) ◽  
pp. 1085-1087
Author(s):  
Pierre Girard ◽  
Paul Abadie
Keyword(s):  
Dielectric Constant ◽  
Electric Field ◽  
Wave Length ◽  
Structural Features ◽  
Loss Angle ◽  
First Case ◽  
Dipolar Molecules ◽  
Alternating Electric Field ◽  
Different Types ◽  
Absorption And Dispersion

Abstract The spectra which were studied lie within the region of hertzian frequencies, and can be represented either by dispersion curves showing the dielectric constant of the substance as a function of the frequency (or wave length λ), or by absorption curves showing the loss angle as a function of this frequency. These two types of curves represent the same phenomenon, i.e., orientation of the dipolar molecules in the alternating electric field, in accordance with the theory of Debye. The spectra and their interpretation depend chiefly on whether the molecules are crystalloid with relatively small and similar dimensions, or are colloidal, with large and unequal dimensions. In the first case, the spectra gives evidence chiefly on the form of the molecules and their structural features. Dilution in a nonpolar solvent shows for certain dipolar compounds, e.g., alcohol, considerable deformations, which differ according to the solvent. In the case of colloids, e.g., rubber, which has a permanent moment, the spectra and the meaning of these spectra are far different. In this case the spectra indicate that the absorption and dispersion values in the hertzian region are closely related to the micellar constitution, i.e., to the different types of micelles, to their size, and to the proportion of each type.

scholarly journals Recombination and the long duration of the Balmer spectrum

1946 ◽  
Vol 186 (1005) ◽  
pp. 236-241 ◽  
Keyword(s):  
Electric Field ◽  
Experimental Conditions ◽  
Balmer Series ◽  
Electrodeless Discharge ◽  
Long Duration

Lord Rayleigh has recently found that the time of relaxation of the Balmer series of hydrogen excited by an electrodeless discharge is at least of the order 10 -5 sec. after it has been blown out of the electric field by its own expansion. Following Page, it is assumed that the luminosity is due to recombination of electrons with protons, and then Kramers’s theory yields halfvalue periods certainly larger than 10 -5 sec. under the special experimental conditions. Difficulties in the application of this theory raised by Cillié and Page are briefly discussed.

scholarly journals Finite-element analysis of microwave scattering from a three-dimensional human head model for brain stroke detection

2018 ◽  
Vol 5 (7) ◽  
pp. 180319
Author(s):  
Awais Munawar Qureshi ◽  
Zartasha Mustansar ◽  
Samah Mustafa
Keyword(s):  
Finite Element ◽  
Dielectric Properties ◽  
Electric Field ◽  
Three Dimensional ◽  
Human Head ◽  
Head Model ◽  
Different Types ◽  
Brain Stroke ◽  
Human Head Model ◽  
Brain Stroke Detection

In this paper, a detailed analysis of microwave (MW) scattering from a three-dimensional (3D) anthropomorphic human head model is presented. It is the first time that the finite-element method (FEM) has been deployed to study the MW scattering phenomenon of a 3D realistic head model for brain stroke detection. A major contribution of this paper is to add anatomically more realistic details to the human head model compared with the literature available to date. Using the MRI database, a 3D numerical head model was developed and segmented into 21 different types through a novel tissue-mapping scheme and a mixed-model approach. The heterogeneous and frequency-dispersive dielectric properties were assigned to brain tissues using the same mapping technique. To mimic the simulation set-up, an eight-elements antenna array around the head model was designed using dipole antennae. Two types of brain stroke (haemorrhagic and ischaemic) at various locations inside the head model were then analysed for possible detection and classification. The transmitted and backscattered signals were calculated by finding out the solution of the Helmholtz wave equation in the frequency domain using the FEM. FE mesh convergence analysis for electric field values and comparison between different types of iterative solver were also performed to obtain error-free results in minimal computational time. At the end, specific absorption rate analysis was conducted to examine the ionization effects of MW signals to a 3D human head model. Through computer simulations, it is foreseen that MW imaging may efficiently be exploited to locate and differentiate two types of brain stroke by detecting abnormal tissues’ dielectric properties. A significant contrast between electric field values of the normal and stroke-affected brain tissues was observed at the stroke location. This is a step towards generating MW scattering information for the development of an efficient image reconstruction algorithm.

Low-frequency fluctuations of the electric field in the equatorial ionosphere

Nature ◽  
1985 ◽  
Vol 313 (6003) ◽  
pp. 559-560 ◽  
Author(s):  
V. L. Patel ◽  
Pablo Lagos
Keyword(s):  
Electric Field ◽  
Low Frequency ◽  
Equatorial Ionosphere ◽  
Frequency Fluctuations

Electric field in the equatorial ionosphere

1992 ◽  
Vol 40 (7) ◽  
pp. 941-952 ◽  
Author(s):  
V.V. Denisenko ◽  
S.S. Zamay
Keyword(s):  
Electric Field ◽  
Equatorial Ionosphere
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