SCATTERING FROM A CYLINDER COATED WITH AN INHOMOGENEOUS DIELECTRIC SHEATH

1963 ◽  
Vol 41 (1) ◽  
pp. 143-151 ◽  
Author(s):  
C. Yeh ◽  
Z. A. Kaprielian
Keyword(s):  
Dielectric Constant ◽  
Scattering Problem ◽  
Plane Waves ◽  
Space Vehicle ◽  
Plasma Sheath ◽  
Scattering Coefficients ◽  
Average Value ◽  
Inhomogeneous Dielectric ◽  
Specific Variation ◽  
Plane Wave Scattering

As a space vehicle re-enters the atmosphere, a plasma sheath, surrounding the vehicle, is generated. It is well known that the sheath is inhomogeneous. However, to make this problem suitable for theoretical analysis, most investigators make the assumption that the sheath is homogeneous. To investigate the validity of this assumption, the idealized problem of the scattering of plane waves by a conducting cylinder coated with a stratified dielectric sheath is considered. The wave equation is separated using the vector wave-function method of Hansen and Stratton. It is then applied to the plane-wave scattering problem. The backscattering cross section is defined and obtained. Analytical expressions for the scattering coefficients of a thin inhomogeneous sheath are also given. Numerical computations are carried out for a specific variation of the dielectric sheath: i.e., ε(r) = ε0α/k0r, where α is a constant, k02 = ε2 με0, and ε0 is the free-space dielectric constant. Results are compared with the homogeneous sheath problem; the dielectric constant of the homogeneous sheath is taken to be the average value of that for the inhomogeneous sheath. It is found that in general rather distinct differences are observed except when the sheath is very thin.

scholarly journals Rigorous Solution to Plane Wave Scattering by an Arbitrary-Shaped Particle Embedded into a Cylindrical Cell of Similar Material

2009 ◽  
Vol 2009 ◽  
pp. 1-6 ◽  
Author(s):  
Constantine A. Valagiannopoulos
Keyword(s):  
Plane Wave ◽  
Electromagnetic Scattering ◽  
Hypergeometric Functions ◽  
Integral Formula ◽  
Scattering Problem ◽  
Double Series ◽  
Infinite Cylinder ◽  
Shaped Particle ◽  
Plane Wave Scattering ◽  
Good Agreement

An infinite cylinder of arbitrary shape is embedded into a circular one, and the whole structure is illuminated by a plane wave. The electromagnetic scattering problem is solved rigorously under the condition that the materials of the two cylinders possess similar characteristics. The solution is based on a linear Taylor expansion of the scattering integral formula which can be useful in a variety of different configurations. For the specific structure, its own far field response is given in the form of a double series incorporating hypergeometric functions. The results are in good agreement with those obtained via eigenfunction expansion. Several numerical examples concerning various shape patterns are examined and discussed.

Acoustic Scattering Cross Sections of Smart Obstacles: A Case Study

2011 ◽  
Vol 10 (3) ◽  
pp. 672-694
Author(s):  
Lorella Fatone ◽  
Maria Cristina Recchioni ◽  
Francesco Zirilli
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Space Shuttle ◽  
Scattering Problem ◽  
Plane Waves ◽  
Acoustic Scattering ◽  
Scattering Cross Section ◽  
Scattering Cross ◽  
Scattering Cross Sections

AbstractAcoustic scattering cross sections of smart furtive obstacles are studied and discussed. A smart furtive obstacle is an obstacle that, when hit by an incoming field, avoids detection through the use of a pressure current acting on its boundary. A highly parallelizable algorithm for computing the acoustic scattering cross section of smart obstacles is developed. As a case study, this algorithm is applied to the (acoustic) scattering cross section of a “smart” (furtive) simplified version of the NASA space shuttle when hit by incoming time-harmonic plane waves, the wavelengths of which are small compared to the characteristic dimensions of the shuttle. The solution to this numerically challenging scattering problem requires the solution of systems of linear equations with many unknowns and equations. Due to the sparsity of these systems of equations, they can be stored and solved using affordable computing resources. A cross section analysis of the simplified NASA space shuttle highlights three findings: i) the smart furtive obstacle reduces the magnitude of its cross section compared to the cross section of a corresponding “passive” obstacle; ii) several wave propagation directions fail to satisfactorily respond to the smart strategy of the obstacle; iii) satisfactory furtive effects along all directions may only be obtained by using a pressure current of considerable magnitude. Numerical experiments and virtual reality applications can be found at the website: http://www.ceri.uniromal.it/ceri/zirilli/w7.

On the Calculation of Radiation Force on Spheres Due to Arbitrary Spatially Distributed Acoustic Beams

2005 ◽  
Author(s):  
Glauber T. Silva ◽  
Mostafa Fatemi
Keyword(s):  
Acoustic Radiation ◽  
Scattering Problem ◽  
Plane Waves ◽  
Acoustic Scattering ◽  
Radiation Force ◽  
Solid Sphere ◽  
Force Function ◽  
Cross Section Area ◽  
Spatially Distributed ◽  
Sphere Radius

This work presents a theory for the acoustic radiation force exerted on a solid sphere by an arbitrary spatially distributed beam. The theory is developed for an sphere suspended in an ideal fluid. We assume that the acoustic beam can be decomposed in a set of plane waves with same frequency, propagating in different directions. The sphere radius is considered to be much smaller than the wavelength of the beam. Bulk properties of the sphere such as shear and compressional sound speed are taken into account. The radiation force is obtained by solving the linear acoustic scattering problem for the sphere. Theoretically, the radiation force depends on the sphere cross section area, the radiation force function, and the vector energy flux upon the sphere. The radiation force function is related to the sphere scattering properties. We apply the developed theory to study the radiation force produced by an spherical concave transducer. The generated radiation force can be decomposed into two components, namely, axial and transverse with respect to the wave propagation direction. The ratio between the transverse and axial components of the force depends on the transducer F-number and wave frequency. Results show that this ratio for a 2 MHz transducer with 3.5 F-number on the focal plane is less than 5%.

Study of Electromagnetic Scattering Characteristics from Typical Land Surface with Integral Equation Method

2012 ◽  
Vol 571 ◽  
pp. 631-635
Author(s):  
Yuan Yuan Zhang ◽  
Zhen Sen Wu ◽  
Ya Qing Li ◽  
Han Lu Zhang
Keyword(s):  
Integral Equation ◽  
Dielectric Constant ◽  
Electromagnetic Scattering ◽  
Land Surface ◽  
Integral Equation Method ◽  
Equation Method ◽  
Surface Model ◽  
Scattering Coefficients ◽  
Dielectric Model ◽  
Good Agreement

Based on the equivalent dielectric model, the permittivity of the soil and simple plants which are assumed to satisfy exponential rough surface model is calculated. The electromagnetic scattering coefficients for the two types of rough surfaces are investigated by the Integral Equation Method (IEM) with the changing dielectric constant. The detailed analysis and discussions are made. And the results obtained are in good agreement with the experimental results.

TWO VERSIONS OF QUASI-NEWTON METHOD FOR MULTIDIMENSIONAL INVERSE SCATTERING PROBLEM

1993 ◽  
Vol 01 (02) ◽  
pp. 197-228 ◽  
Author(s):  
SEMION GUTMAN ◽  
MICHAEL KLIBANOV
Keyword(s):  
Newton Method ◽  
Inverse Scattering ◽  
Born Approximation ◽  
Scattering Problem ◽  
Plane Waves ◽  
Inverse Scattering Problem ◽  
Circular Cylinders ◽  
Iterative Sequence ◽  
Scattering Field ◽  
Quasi Newton

Suppose that a medium with slowly changing spatial properties is enclosed in a bounded 3-dimensional domain and is subjected to a scattering by plane waves of a fixed frequency. Let measurements of the wave scattering field induced by this medium be available in the region outside of this domain. We study how to extract the properties of the medium from the information contained in the measurements. We are concerned with the weak scattering case of the above inverse scattering problem (ISP), that is, the unknown. spatial variations of the medium are assumed to be close to a constant. Examples can be found in the studies of the wave propagation in oceans, in the atmosphere, and in some biological media. Since the problems are nonlinear, the methods for their linearization (the Born approximation) have been developed. However, such an approach often does not produce good results. In our method, the Born approximation is just the first iteration and further iterations improve the identification by an order of magnitude. The iterative sequence is defined in the framework of a Quasi-Newton method. Using the measurements of the scattering field from a carefully chosen set of directions we are able to recover (finitely many) Fourier coefficients of the sought parameters of the model. Numerical experiments for the scattering from coaxial circular cylinders as well as for simulated data are presented.

scholarly journals Exact Matrix Representation of the Transverse Magnetic Multiple Scattering of Obliquely Incident Plane Waves by the Diffraction Grating of Penetrable Cylinders

2012 ◽  
Vol 2012 ◽  
pp. 1-17
Author(s):  
Ömer Kavaklıoğlu ◽  
Roger Henry Lang
Keyword(s):  
Multiple Scattering ◽  
Diffraction Grating ◽  
Plane Waves ◽  
Transverse Magnetic ◽  
Circular Cylinders ◽  
Scattering Coefficients ◽  
Obliquely Incident ◽  
Incident Plane ◽  
Inversion Procedure ◽  
Exact Matrix

“An exact matrix conformation model” associated with the equations describing the exact behavior of the Fourier-Bessel multiple scattering coefficients of the diffraction grating consisting of an infinite number of infinitely long parallel penetrable circular cylinders, corresponding to the obliquely incident transverse-magnetic plane waves in “Twersky-Wait-Kavaklıoğlu representation,” originally excogitated in (Kavaklıoğlu, 2000), is acquired, and the exact solution for “the Fourier-Bessel multiple scattering coefficients of the diffraction grating at oblique incidence” is obtained by a matrix inversion procedure.

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