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Träfflista för sökning "WFRF:(Kristensson Gerhard) srt2:(1985-1989)"

Sökning: WFRF:(Kristensson Gerhard) > (1985-1989)

  • Resultat 1-8 av 8
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2.
  • Cheney, Margaret, et al. (författare)
  • Three-dimensional inverse scattering: layer-stripping formulas and ill-posedness results
  • 1988
  • Ingår i: Inverse Problems. - : IOP Publishing. - 0266-5611 .- 1361-6420. ; 4:3, s. 625-642
  • Tidskriftsartikel (refereegranskat)abstract
    • The authors consider the three-dimensional direct and inverse scattering problems for the Schrodinger equation and for the reduced wave equation with variable velocity. The scatterer is probed with either point sources or plane waves of fixed frequency. They ask the question, 'How does the wave field change when the scatterer is truncated?' Simple formulae for the derivative of the wave field with respect to the truncation parameter are obtained. Similar formulae are obtained for the scattering amplitudes. These formulae are used to derive ill-posedness results for various inverse scattering problems. The ill-posedness results apply when data are collected over a range of frequencies.
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3.
  • Karlsson, Anders, et al. (författare)
  • Constitutive relations, dissipation and reciprocity for the Maxwell equations in the time domain
  • 1989
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • The main goal of this paper is to establish general constitutive relations for the electromagnetic fields E,D,B and H in a time domain setting. The four basic assumptions of the medium are linearity, invariance to time translations, causality and continuity. These four assumptions imply that the constitutive relations are convolutions of Riemann-Stieltjes type. A review of the classifi- cation of media in bianisotropic, biisotropic, anisotropic and isotropic media, respectively, is made. Dissipation and reciprocity are defined and the constraints these concepts make on the constitutive relations are analyzed in detail. Furthermore, an appropriate form of time reversal and functions of positive type are introduced and some consequences of these concepts are showed.
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  • Karlsson, Anders, et al. (författare)
  • Wave splitting in the time domain for a radially symmetric geometry
  • 1989
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A decomposition of the field of the wave equation in three dimensions is suggested. This wave splitting decomposes the field into two components such that in free space simple propagation properties are obtained. The inhomogeneous region is assumed to have a phase velocity variation that varies only in the radial coordinate r from the origin. The suggested wave splitting is a generalization of the wave splitting concept in one spatial dimension. Specifically, the propagation properties in free space in the three-dimensional wave splitting are very analogous to the corresponding propagation properties in free space in one dimension. The three-dimensional decomposition is illustrated in an example of scattering by a sound-soft sphere of radius a.
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8.
  • Pantze, Robert, et al. (författare)
  • Directional EM measurements in boreholes
  • 1986
  • Ingår i: Borehole Geophysics for Mining and Geotechnical Applications. ; , s. 79-88
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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  • Resultat 1-8 av 8

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