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Träfflista för sökning "swepub ;srt2:(1990-1994);mspu:(report);pers:(Karlsson Anders)"

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

  • Resultat 1-9 av 9
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1.
  • Karlsson, Anders, et al. (författare)
  • Modulation and Noise Properties of Multi-element Semiconductor Lasers
  • 1991
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • In this report a previously presented theory for the modulation and noise properties of multi-element lasers is revised. Explicit formulas for modulation response, amplitude and frequency noise are found. The theory is illustrated by numerical examples.
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2.
  • Fuks, Peter, et al. (författare)
  • Direct and inverse scattering from dispersive media
  • 1993
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Direct and inverse scattering from dispersive media are studied in the time domain. The media are one-dimensional and homogeneous but can be impedance mismatched to the surrounding media. A time domain method is introduced where the reflection and transmission kernels are obtained from Volterra equations of the second kind. Numerical examples are given based upon both synthetic and measured data for the inverse problem.
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3.
  • Hellberg, Rasmus, et al. (författare)
  • Design of reflextionless slabs for transient electromagnetic waves
  • 1994
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A method for modeling reflectionless conductive dispersive slabs is presented. The slabs are impedance matched to the surrounding half-spaces and are temporally dispersive with a spatially varying impedance. It is shown that the effects from the variation of the impedance can be matched by the temporal dispersive effects and the conductivity so that for a normally incident plane wave the slab does not reflect any field regardless of the shape of the incident transient field. The problem of finding reflectionless media is formulated as an inverse problem where the constitutive relation is to be determined as a function of depth given a reflection kernel which is zero. The inverse problem is solved by a time domain Green functions technique.
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4.
  • Karlsson, Anders, et al. (författare)
  • Transient Electromagnetic Wave Propagation in Transverse Periodic Media
  • 1994
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • In this paper, wave propagation of electromagnetic pulses in media that are periodic in one spatial direction is analyzed by a time domain technique. The special case of wave propagation in an inhomogeneous planar waveguide with perfectly conducting walls is also discussed. The wave equation is reduced to a set of one dimensional first order hyperbolic equations by an expansion in a complete set of basis functions and by utilizing a wave splitting technique. The method is especially useful for the propagation of broad pulses.
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5.
  • Karlsson, Anders, et al. (författare)
  • Transient wave propagation in composite media: A Green functions approach
  • 1992
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A generalized Green functions technique for wave propagation of transient fields in one-dimensional media is developed. The medium is partitioned into an arbitrary number of subslabs for which Green operators, that map the incident field to the internal fields, are defined. Relations between the Green operators for the entire medium and the Green operators for the subslabs are derived. The technique leads to fast numerical algorithms which are especially efficient for dispersive media. The numerical examples focus on the comparison between wave propagation in dispersive and non-dispersive media.
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6.
  • Karlsson, Anders, et al. (författare)
  • Transient wave propagation in gyrotropic media
  • 1990
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • In this paper transient electromagnetic wave propagation in an inhomogeneous, cold plasma is considered. It is assumed that a constant magnetic induction is present and that the plasma is spatially inhomogeneous in the direction of the magnetic induction. Losses in the plasma are modeled with a collision frequency ν. The direct problem, which is to calculate the reflected and transmitted responses of the plasma, is considered in this paper. Special attention is paid to the precursor effects in the plasma and several examples of precursor effects in an inhomogeneous plasma are showed.
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7.
  • Karlsson, Anders, et al. (författare)
  • Wave propagators for transient waves in periodic media
  • 1994
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • One-dimensional propagation of transient EM-waves in periodic media is studied. The media are periodic in the direction of propagation and can be of finite or infinite length. Wave propagators, that map a transient field from one point in the medium to another, are introduced. A number of useful relations for the propagators are presented. Some of these relations are used in the determination of explicit expressions for the short time behavior of a transient wave as it propagates in a periodic medium. The theory is exemplified by several numerical examples.
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8.
  • Karlsson, Anders, et al. (författare)
  • Wave splitting and imbedding equations for a spherically symmetric dispersive medium
  • 1991
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • The direct problem of time dependent electromagnetic scattering in the dispersive sphere is solved by a wave splitting technique. The electric field is expanded in a series involving vector spherical harmonics, leading to a system of wave equations for each term. These systems are reduced to scalar wave equations for each term, which are solved via reflection operators. Some preliminary numerical results are presented.
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9.
  • Malmqvist, Lennart, et al. (författare)
  • Electromagnetic fields in boreholes-measurements and theory in three dimensions
  • 1990
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A comparison between experimental measurements of the electromagnetic field in boreholes and a mathematical model is made. The transmitting antenna is a rectangular wire loop on the ground and the three orthogonal components of the magnetic field are measured below the ground in the borehole. In the mathematical model the ground is assumed to be a stratified half space with a rectangular wire antenna on the ground. Excellent agreement was found between the experimental results and the theoretical ones in most cases and where deviations were found, the assumption of a stratified ground was inaccurate due to present conductive inhomogeneities. The method presented in this paper is capable of determining an ore body within a radius of 100 m from the borehole. The position (direction and distance) of the target can be estimated from the measurements in the borehole. The impact on the economical effectiveness of a drilling programme is considerable when a prediction of the location of additional boreholes can be made. In the case of reconnaissance drilling of a geological structure or trend the distance between adjacent boreholes can be considerably enlarged.
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  • Resultat 1-9 av 9

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