| 41. |
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| 42. |
- Folkow, Peter D., et al.
(författare)
-
Time domain Green functions for the homogeneous Timoshenko beam
- 1998
-
Ingår i: Quarterly Journal of Mechanics and Applied Mathematics. - : Oxford University Press (OUP). - 0033-5614 .- 1464-3855. ; 51:1, s. 125-141
-
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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| 43. |
- Folkow, Peter D., et al.
(författare)
-
Time domain Green functions for the homogeneous Timoshenko beam
- 1996
-
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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| 44. |
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| 45. |
- Fridén, Jonas, et al.
(författare)
-
Calculation of antenna radiation center using angular momentum
- 2013
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 61:12, s. 5923-5930
-
Tidskriftsartikel (refereegranskat)abstract
- An algorithm to compute the radiation center of an antenna, using the Spherical wave expansion (SWE) of the far field or the far field directly, is introduced. The method is based on the angular momentum that is uniquely defined for any antenna far field pattern. The radiation center is defined as the phase reference point where the angular momentum is minimized and corresponds to minimizing the phase variations in the antenna far field pattern. In addition, this approach also allows for determination of the current distribution axis.
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| 46. |
- Friden, Jonas, et al.
(författare)
-
Calculation of antenna radiation center using angular momentum
- 2012
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- An algorithm to compute the Radiation Center of an antenna based on the Spherical Wave Expansion is introduced. The method is based on the angular momentum vector that is uniquely defined for any antenna far field pattern. The radiation center is defined as the phase reference point where the angular momentum is minimized and corresponds to minimizing the phase variations in the antenna far field pattern. In addition, this approach also allows for determination of the Current Distribution Axis.
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| 47. |
- Fridén, Jonas, et al.
(författare)
-
Calculation of antenna radiation center using angular momentum
- 2013
-
Ingår i: 7th European Conference on Antennas and Propagation (EuCAP), 2013. - 9781467321877 ; , s. 1531-1535
-
Konferensbidrag (refereegranskat)abstract
- An algorithm to compute the Radiation center of an antenna based on the Spherical wave expansion is introduced. The method is based on the angular momentum vector that is uniquely defined for any antenna far field pattern. The radiation center is defined as the unique point where the magnitude of the angular momentum is minimized with respect to translations of the far field. This corresponds to minimizing the phase variations in the antenna far field pattern. In addition the Current distribution axis can be determined, corresponding to minimization of the vertical component of angular momentum.
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| 48. |
- Fridén, Jonas, et al.
(författare)
-
Effect of dissipation on the constitutive relations of bi-anisotropic media - the optical response
- 1997
-
Ingår i: Electromagnetics. - : Informa UK Limited. - 0272-6343 .- 1532-527X. ; 17:3, s. 251-267, s. 125-128
-
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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| 49. |
- Fridén, Jonas, et al.
(författare)
-
Effect of dissipation on the constitutive relations of bi-anisotropic media - the optical response
- 1996
-
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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| 50. |
- Fridén, Jonas, et al.
(författare)
-
Transient electromagnetic wave propagation in anisotropic dispersive media
- 1993
-
Ingår i: Journal of the Optical Society of America A: Optics and Image Science, and Vision. - 1084-7529. ; 10:12, s. 2618-2627
-
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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