ACOUSTIC WAVES AND THEIR EFFECTS ON ANTENNA IMPEDANCE

1967 ◽  
Vol 45 (3) ◽  
pp. 1251-1269 ◽  
Author(s):  
J. Carlin ◽  
R. Mittra
Keyword(s):  
Acoustic Waves ◽  
Exact Expression ◽  
Acoustic Velocity ◽  
Dielectric Sphere ◽  
Hydrodynamic Description ◽  
Spherical Boundary ◽  
Warm Plasma ◽  
Compressibility Effects ◽  
Phase Length ◽  
Variational Expression

Expressions have been derived for the terminal admittance of a biconical dipole encased in a dielectric sphere which is immersed in a warm plasma. A linearized hydrodynamic description is used for the plasma. For thin-angle cones an exact expression is derived. For thick-angle cones the terminal admittance is related to the aperture fields at the spherical boundary of the cones by means of a variational expression. The admittance was found to be strongly dependent on the ratio of the velocity of light in free space to the acoustic velocity in the plasma. Compressibility effects seem to be quite significant if the acoustical "phase length" of the antenna is between approximately 0.5 and 10.

Cylindrical ion-acoustic waves in a warm multicomponent plasma

2000 ◽  
Vol 63 (4) ◽  
pp. 343-353 ◽  
Author(s):  
S. K. EL-LABANY ◽  
S. A. EL-WARRAKI ◽  
W. M. MOSLEM
Keyword(s):  
Perturbation Theory ◽  
Acoustic Waves ◽  
Vries Equation ◽  
Negative Ions ◽  
Ion Acoustic Waves ◽  
Multicomponent Plasma ◽  
Reductive Perturbation ◽  
Ion Acoustic ◽  
Ion Acoustic Solitons ◽  
Warm Plasma

Cylindrical ion-acoustic solitons are investigated in a warm plasma with negative ions and multiple-temperature electrons through the derivation of a cylindrical Korteweg–de Vries equation using a reductive perturbation theory. The results are compared with those for the corresponding planar solitons.

Weakly relativistic effect on the modulation of nonlinear ion-acoustic waves in a warm plasma

1995 ◽  
Vol 54 (3) ◽  
pp. 295-308 ◽  
Author(s):  
S. K. El-Labany
Keyword(s):  
Perturbation Theory ◽  
Acoustic Waves ◽  
Relativistic Effect ◽  
Type Equation ◽  
Oscillatory Solution ◽  
Ion Temperature ◽  
Ion Acoustic Waves ◽  
Ion Density ◽  
Ion Acoustic ◽  
Warm Plasma

The derivative expansion perturbation method is applied to investigate the modulation of nonlinear ion-acoustic waves in a weakly relativistic warm plasma. At the second order of perturbation theory, a nonlinear Schrödingertype equation for the complex amplitude of the perturbed ion density is obtained. The coefficients in this equation show that the condition of modulational stability is modified by the relativistic effect as well as by the finite ion temperature. The association between the small-wavenumber limit of the nonlinear Schrödinger-type equation and the oscillatory solution of the Korteweg-de Vries equation obtained by reductive perturbation theory is considered. Different limits are considered in order to compare with previous work.

RESONANCES OF ACOUSTIC WAVES INTERACTING WITH AN ELASTIC SEABED

2001 ◽  
Vol 09 (03) ◽  
pp. 1079-1093 ◽  
Author(s):  
MARGARETE S. FOKINA ◽  
VLADIMIR N. FOKIN
Keyword(s):  
Reflection Coefficient ◽  
Half Space ◽  
Acoustic Waves ◽  
Elastic Half Space ◽  
Exact Expression ◽  
Ocean Bottom ◽  
Sediment Layer ◽  
Resonance Theory ◽  
Space Characteristic ◽  
Exact Calculations

An exact expression for the reflection coefficient is obtained with the Thomson–Haskell technique for the geoacoustical model of an ocean bottom consisting of an elastic homogeneous sediment layer overlying an elastic half-space. Characteristic equations for explicit determination of the position of each individual resonance contribution to the reflection coefficient are derived. Analytical expressions for the angular and frequency resonance positions are found. The resonance expression for the reflection coefficient is written in the form of a sum of resonance terms. Comparison between resonance theory and exact calculations for the elastic layer covering the elastic half-space is presented. The results of resonance formalism show excellent agreement with exact theory in all the cases.

scholarly journals Comparative between (LiNbO3) and (LiTaO3) in detecting acoustics microwaves using classification

2019 ◽  
Vol 8 (1) ◽  
pp. 33
Author(s):  
Hafdaoui Hichem ◽  
Benatia Djamel
Keyword(s):  
Neural Network ◽  
Numerical Analysis ◽  
Lithium Niobate ◽  
Imaginary Part ◽  
Acoustic Waves ◽  
Probabilistic Neural Network ◽  
Lithium Tantalate ◽  
Acoustic Velocity ◽  
Bulk Acoustic Waves ◽  
Piezoelectric Substrate

Our work is mainly about detecting acoustics microwaves in the type of BAW (Bulk acoustic waves), where we compared between Lithium Niobate (LiNbO3) and Lithium Tantalate (LiTaO3) ,during the propagation of acoustic microwaves in a piezoelectric substrate. In this paper, We have used the classification by Probabilistic Neural Network (PNN) as a means of numerical analysis in which we classify all the values of the real part and the imaginary part of the coefficient attenuation with the acoustic velocity for conclude whichever is the best in utilization for generating bulk acoustic waves.This study will be very interesting in modeling and realization of acoustic microwaves devices (ultrasound) based on the propagation of acoustic microwaves.

Nonlinear ion acoustic waves in a quantum degenerate warm plasma with dust grains

2011 ◽  
Vol 37 (1) ◽  
pp. 64-74 ◽  
Author(s):  
A. E. Dubinov ◽  
D. Yu. Kolotkov ◽  
M. A. Sazonkin
Keyword(s):  
Acoustic Waves ◽  
Dust Grains ◽  
Ion Acoustic Waves ◽  
Ion Acoustic ◽  
Warm Plasma

scholarly journals Elastic properties and plane acoustic velocity of cubic Sr2CaMoO6 and Sr2CaWO6 from first-principles calculations

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 826-831
Author(s):  
Zhenyuan Jia ◽  
Peida Wang ◽  
Willie Smith
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Acoustic Waves ◽  
Density Functional ◽  
Local Density ◽  
Three Dimensional ◽  
Double Perovskite ◽  
Acoustic Velocity ◽  
Generalized Gradient ◽  
Functional Theory

Abstract The elastic properties and plane acoustic velocity of double perovskite Sr2CaMoO6 and Sr2CaWO6 are investigated with the plane wave pseuedopotential method based on the first-principles density functional theory within the local density approximate (LDA) and the generalized gradient approximation (GGA). The calculations indicate that Sr2CaMoO6 and Sr2CaWO6 respectively have the the Mo-O and W-O stable octahedral structure. The bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio ν and Debye temperature were calculated based on the elastic constants. The three dimensional plane acoustic velocities and their projection are in calculated for each direction by solving the Christoffel’s equation systematically based on the theory of acoustic waves in anisotropic solids, the result shows of anisotropy of lattice vibration for Sr2CaMoO6 is stronger than Sr2CaWO6.

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