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Sökning: swepub > (1990-1994) > Rapport > Karlsson Anders > Kristensson Gerhard > Engelska

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  • Karlsson, Anders, et al. (författare)
  • Transient wave propagation in gyrotropic media
  • 1990
  • Rapport (övrigt vetenskapligt)abstract
    • In this paper transient electromagnetic wave propagation in an inhomogeneous,<br /> cold plasma is considered. It is assumed that a constant magnetic<br /> induction is present and that the plasma is spatially inhomogeneous in the<br /> direction of the magnetic induction. Losses in the plasma are modeled with a<br /> collision frequency ν. The direct problem, which is to calculate the reflected<br /> and transmitted responses of the plasma, is considered in this paper. Special<br /> attention is paid to the precursor effects in the plasma and several examples<br /> of precursor effects in an inhomogeneous plasma are showed.
  • Karlsson, Anders, et al. (författare)
  • Wave splitting and imbedding equations for a spherically symmetric dispersive medium
  • 1991
  • Rapport (övrigt vetenskapligt)abstract
    • The direct problem of time dependent electromagnetic scattering in the dispersive<br /> sphere is solved by a wave splitting technique. The electric field is<br /> expanded in a series involving vector spherical harmonics, leading to a system<br /> of wave equations for each term. These systems are reduced to scalar<br /> wave equations for each term, which are solved via reflection operators. Some<br /> preliminary numerical results are presented.
  • Malmqvist, Lennart, et al. (författare)
  • Electromagnetic fields in boreholes-measurements and theory in three dimensions
  • 1990
  • Rapport (övrigt vetenskapligt)abstract
    • A comparison between experimental measurements of the electromagnetic<br /> field in boreholes and a mathematical model is made. The transmitting antenna<br /> is a rectangular wire loop on the ground and the three orthogonal<br /> components of the magnetic field are measured below the ground in the borehole.<br /> In the mathematical model the ground is assumed to be a stratified half<br /> space with a rectangular wire antenna on the ground. Excellent agreement<br /> was found between the experimental results and the theoretical ones in most<br /> cases and where deviations were found, the assumption of a stratified ground<br /> was inaccurate due to present conductive inhomogeneities. The method presented<br /> in this paper is capable of determining an ore body within a radius of<br /> 100 m from the borehole. The position (direction and distance) of the target<br /> can be estimated from the measurements in the borehole. The impact on<br /> the economical effectiveness of a drilling programme is considerable when a<br /> prediction of the location of additional boreholes can be made. In the case of<br /> reconnaissance drilling of a geological structure or trend the distance between<br /> adjacent boreholes can be considerably enlarged.
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  • Resultat 1-3 av 3
fritt online (3)
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övrigt vetenskapligt (3)
Malmqvist, Lennart (1)
Otterheim, Henrik (1)
Kreider, Kevin (1)
Pantze, Robert (1)
Lunds universitet (3)
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