| 1. |
- Fridén, Jonas, et al.
(författare)
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Transient electromagnetic wave propagation in anisotropic dispersive media
- 1993
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Ingår i: Journal of the Optical Society of America A: Optics and Image Science, and Vision. - 1084-7529. ; 10:12, s. 2618-2627
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Tidskriftsartikel (refereegranskat)abstract
- Transient electromagnetic wave propagation in a stratified, anisotropic, dispersive medium is considered. Specifically, the direct scattering problem is addressed. The dispersive, anisotropic medium is modeled by constitutive relations (a 3 3 matrix-valued susceptibility operator) containing time convolution integrals. In the general case, nine different susceptibility kernels characterize the medium. An incident plane wave impinges obliquely upon a finite slab consisting of a stratified anisotropic medium. The scattered fields are obtained as time convolutions of the incident field with the scattering kernels. The scattering (reflection and transmission) kernels are uniquely determined by the slab and are independent of the incident field. The scattering problem is solved by a wave-splitting technique. Two different methods for determining the scattering kernels are presented: an embedding and a Green's function approach. Explicit analytic expressions of the wave front are given for a special class of media. Some numerical examples illustrate the analysis.
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| 2. |
- Kristensson, Gerhard, et al.
(författare)
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The inverse scattering problem for a homogeneous bi-isotropic slab using transient data
- 1993
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Ingår i: Inverse problems in mathematical physics / Lecture notes in physics. - 0075-8450. - 3540571957 ; 422, s. 112-125
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Transient wave propagation in a finite bi-isotropic slab is treated. The incident field impinges normally on the slab, which can be inhomogeneous wrt depth. Dispersion and bi-isotropy are modeled by time convolutions in the constitutive relations. Outside the slab the medium is assumed to be homogeneous, non-dispersive and isotropic, and such that there is no phase velocity mismatch at the boundaries of the slab. Two alternative methods of solution to the propagation problem are given—the imbedding method and the Green function approach. The second method is used to solve the inverse problem and the first to generate synthetic data. The inverse scattering problem is to reconstruct the four susceptibility kernels of the medium using a set of finite time trace of reflection and transmission data.
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| 3. |
- Kristensson, Gerhard
(författare)
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Transient Electromagnetic Wave Propagation in Waveguides
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper focuses on propagation of transient electromagnetic waves in waveguides of general cross section with perfectly conducting walls. The solution of the transient wave propagation problem relies on a wave splitting technique, which has been frequently used in direct and inverse scattering problems during the last decade. The field in the waveguide is represented as a time convolution of a Green function and the excitation. Some numerical computations illustrate the method. Anew way of calculating the first precursor in a Lorentz medium is presented. This method, which is not based upon the classical asymptotic methods, gives an expression of the first precursor at all depths in the medium. The excitation of the waveguide modes for time dependent sources is also addressed.
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| 4. |
- Kristensson, Gerhard, et al.
(författare)
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Transient wave propagation in reciprocal bi-isotropic media at oblique incidence
- 1993
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Ingår i: Journal of Mathematical Physics. - : AIP Publishing. - 0022-2488 .- 1089-7658. ; 34:4, s. 1339-1359
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a new wave splitting is suggested that simplifies the analysis of wave propagation in reciprocal bi-isotropic media. Two different methods to solve the scattering problem are analyzed: the invariant imbedding and the Green function approach. The medium is modeled by constitutive relations in the time domain (time convolutions) and the slab is assumed to be inhomogeneous with respect to the depth. It is shown that the cross-polarized contribution to the reflected field at normal incidence is zero for the general reciprocal inhomogeneous slab. Moreover, the rotation and the attenuation of the wave front are calculated explicitly in the general inhomogeneous slab case. Special attention is paid to normal incidence and to the homogeneous semi-infinite medium.
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| 5. |
- Olsson, Peter, et al.
(författare)
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Wave splitting of the Timoshenko beam equation in the time domain
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, wave splitting in conjunction with invariant imbedding and Green’s function techniques has been applied with great success to a number of interesting inverse and direct scattering problems. The aim of the present paper is to derive a wave splitting for the Timoshenko equation, a fourth order PDE of importance in beam theory. An analysis of the hyperbolicity of the Timoshenko equation and its, in a sense, less physical relatives—the Euler-Bernoulli and the Rayleigh equations—is also provided.
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