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| 2. |
- Bernekorn, Peter, et al.
(författare)
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Propagation of transient electromagnetic waves in inhomogeneous and dispersive waveguides
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Transient wave propagation in a waveguide filled with an inhomogeneous dispersive medium is analyzed. The waveguide is inhomogeneous in the longitudinal direction, but is homogeneously filled in the transverse directions. The analysis is performed in the time domain and is based upon a wave splitting technique and the method of propagators. The propagator maps the exciting field from one position in the waveguide to the field at another position. This mapping is represented as time convolution integrals. The theory is exemplified by numerical examples where it is shown how wave trains of different shapes are propagating in a waveguide filled with a homogeneous dispersive medium.
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| 3. |
- Björkberg, Jonas, et al.
(författare)
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Three-dimensional subterranean target identification by use of optimization techniques
- 1997
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Ingår i: Progress in Electromagnetics Research PIER. - 1070-4698. ; 15, s. 141-164
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Tidskriftsartikel (refereegranskat)abstract
- The identification of a subterranean metallic ore from scattering experiments, conducted on the surface of the ground or in a bore hole, is a classic geophysical problem. In general this problem is not well-posed. However, a priori information about the shape of the target provides enough regularization to make the problem numerically stable. The problem is solved by minimizing the mean-square error between an eleven parameter model, based on the null field approach, and the data. The optimization is done with a Newton technique in which a singular value decomposition of the model Jacobian is employed. The algorithm is very stable to noise and makes good reconstructions from feasible starting guesses, for realistically noise contaminated data.
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| 4. |
- Egorov, Igor, et al.
(författare)
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Transient electromagnetic wave propagation in laterally discontinuous, dispersive media
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper concerns propagation of transient electromagnetic waves in laterally discontinuous dispersive media. The approach, used here, employs a component decomposition of all fields. Specifically, the propagation operator that maps a transverse field on one plane to another plane is specified. Expansion of this mapping near the wave front determines the precursor or forerunner of the problem.
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| 5. |
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| 6. |
- Folkow, Peter D., et al.
(författare)
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Time domain Green functions for the homogeneous Timoshenko beam
- 1998
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Ingår i: Quarterly Journal of Mechanics and Applied Mathematics. - : Oxford University Press (OUP). - 0033-5614 .- 1464-3855. ; 51:1, s. 125-141
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a wave splitting technique is applied to a homogeneous Timoshenko beam. The purpose is to obtain a diagonal equation in terms of the split fields. These fields are calculated in the time domain from an appropriate set of boundary conditions. The fields along the beam are represented as a time convolution of Green functions with the excitation. The Green functions do not depend on the wave fields but only on the parameters of the beam. Green functions for a Timoshenko beam are derived, and the exponential behaviour of these functions as well as the split modes are discussed. A transformation that extracts the exponential part is performed. Some numerical examples for various loads are presented and compared with results appearing in the literature.
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| 7. |
- Folkow, Peter D., et al.
(författare)
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Time domain Green functions for the homogeneous Timoshenko beam
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, wave splitting technique is applied to a homogeneous Timoshenko beam. The purpose is to obtain a diagonal equation in terms of the split fields. These fields are calculated in the time domain from an appropriate set of boundary conditions. The fields along the beam are represented as a time convolution of Green functions with the excitation. The Green functions do not depend on the wave fields but only on the parameters of the beam. Green functions for a Timoshenko beam are derived, and the exponential behaviour of these functions as well as the split modes are discussed. A transformation that extracts the exponential part is performed. Some numerical examples for various loads are presented and compared with results appearing in the literature.
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| 8. |
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| 9. |
- Fridén, Jonas, et al.
(författare)
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Effect of dissipation on the constitutive relations of bi-anisotropic media - the optical response
- 1997
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Ingår i: Electromagnetics. - : Informa UK Limited. - 0272-6343 .- 1532-527X. ; 17:3, s. 251-267, s. 125-128
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the restrictions that dissipation forces on the material parameters and responses of bi-anisotropic media. The treatment is a general time domain analysis where six-vector formalism is applied. Energy conditions set limitations on the optical response dyadics and dyadic susceptibility kernels of the material that have to be satisfied regardless the time dependence of the fields. This paper will treat in detail the resulting restrictions for the optical response of bi-anisotropic media. Examples are given for some special cases. Also uniqueness and equivalence aspects of constitutive relations in the time domain are discussed.
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| 10. |
- Fridén, Jonas, et al.
(författare)
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Effect of dissipation on the constitutive relations of bi-anisotropic media - the optical response
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper discusses the restrictions that dissipation forces on the material parameters and responses of bi-anisotropic media. The treatment is a general time domain analysis where six-vector formalism is applied. Energy conditions set limitations on the optical response dyadics and dyadic susceptibility kernels of the material that have to be satisfied regardless the time dependence of the fields. This paper will treat in detail the resulting restrictions for the optical response of bi-anisotropic media. Examples are given for some special cases. Also uniqueness and equivalence aspects of constitutive relations in the time domain are discussed.
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