SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "LAR1:lu ;pers:(Kristensson Gerhard)"

Sökning: LAR1:lu > Kristensson Gerhard

  • Resultat 1-10 av 245
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Karlsson, Anders, et al. (författare)
  • Transient wave propagation in gyrotropic media
  • 1992
  • Ingår i: Invariant inbedding and inverse problems. - SIAM. - 0-89871-305-6 ; s. 77-89
  • Bokkapitel (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.
  •  
2.
  • Karlsson, Anders, et al. (författare)
  • Wave splitting and imbedding equations for a spherically symmetric dispersive medium
  • 1992
  • Ingår i: Invariant inbedding and inverse problems. - SIAM. - 0-89871-305-6 ; s. 103-113
  • Bokkapitel (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.
  •  
3.
  • Kristensson, Gerhard, et al. (författare)
  • Time domain inversion techniques for electromagnetic scattering problems
  • 1992
  • Ingår i: Invariant imbedding and inverse problems. - SIAM. - 0-89871-305-6 ; s. 1-29
  • Bokkapitel (övrigt vetenskapligt)abstract
    • This paper presents a review of and a comparison between two different methods<br /> to solve an inverse scattering problem in the time domain. The problem<br /> is that of propagation of transient electromagnetic waves in spatially inhomogeneous<br /> slabs of finite length. The permittivity and conductivity profiles<br /> are assumed to vary only with depth and the scattering problem is thus onedimensional.<br /> Several algorithms to solve the direct and inverse scattering<br /> problems for continuous and discontinuous permittivity profiles are suggested.<br /> Some of these algorithms have not been published before. The aim of this paper<br /> is to compare and review these methods. More specifically, the numerical<br /> performance of the invariant imbedding approach (layer-stripping)and the<br /> Green functions formulation (downward continuation)is compared. Some<br /> new results based upon time reversal techniques for a lossless slab are presented<br /> in an appendix.
  •  
4.
  •  
5.
  • Åberg, Ingegerd, et al. (författare)
  • Propagation of transient electromagnetic waves in time-varying media - Direct and inverse scattering problems
  • 1994
  • Rapport (övrigt vetenskapligt)abstract
    • Wave propagation of transient electromagnetic waves in time-varying media<br /> is considered. The medium, which is assumed to be inhomogeneous and dispersive,<br /> lacks invariance under time translations. The spatial variation of<br /> the medium is assumed to be in the depth coordinate, i.e., it is stratified.<br /> The constitutive relations of the medium is a time integral of a generalized<br /> susceptibility kernel and the field. The generalized susceptibility kernel depends<br /> on one spatial and two time coordinates. The concept of wave splitting<br /> is introduced. The direct and inverse scattering problems are solved by the<br /> use of an imbedding or a Green functions approach. The direct and the inverse<br /> scattering problems are solved for a homogeneous semi-infinite medium.<br /> Explicit algorithms are developed. In this inverse scattering problem, a function<br /> depending on two time coordinates is reconstructed. Several numerical<br /> computations illustrate the performance of the algorithms.
6.
  • Åberg, Ingegerd, et al. (författare)
  • Propagation of transient electromagnetic waves in time-varying media-direct and inverse scattering problems
  • 1995
  • Ingår i: Inverse Problems. - IOP Publishing. - 1361-6420 .- 0266-5611. ; 11:1, s. 29-49
  • Tidskriftsartikel (refereegranskat)abstract
    • Wave propagation of transient electromagnetic waves in time-varying media is considered. The medium, which is assumed to be inhomogeneous and dispersive, lacks invariance under time translations. The spatial variation of the medium is assumed to be in the depth coordinate, i.e. it is stratified. The constitutive relations of the medium are a time integral of a generalized susceptibility kernel and the field. The generalized susceptibility kernel depends on one spatial and two time coordinates. The concept of wave splitting is introduced. The direct and inverse scattering problems are solved by the use of an imbedding or a Green function approach. The direct and the inverse scattering problems are solved for a homogeneous semi-infinite medium. Explicit algorithms are developed. In this inverse scattering problem, a function depending on two time coordinates is reconstructed. Several numerical computations illustrate the performance of the algorithms.
  •  
7.
  • Åberg, Ingegerd, et al. (författare)
  • Transient waves in non-stationary media
  • 1994
  • Rapport (övrigt vetenskapligt)abstract
    • This paper treats propagation of transient waves in non-stationary media,<br /> which has many applications in e.g. electromagnetics and acoustics. The underlying<br /> hyperbolic equation is a general, homogeneous, linear, first order 2×2<br /> system of equations. The coefficients in this system depend only on one spatial<br /> coordinate and time. Furthermore, memory effects are modeled by integral<br /> kernels, which, in addition to the spatial dependence, are functions of two different<br /> time coordinates. These integrals generalize the convolution integrals,<br /> frequently used as a model for memory effects in the medium. Specifically, the<br /> scattering problem for this system of equations is addressed. This problem is<br /> solved by a generalization of the wave splitting concept, originally developed<br /> for wave propagation in media which are invariant under time translations,<br /> and by an imbedding or a Green functions technique. More explicitly, the<br /> imbedding equation for the reflection kernel and the Green functions (propagator<br /> kernels) equations are derived. Special attention is paid to the problem<br /> of non-stationary characteristics. A few numerical examples illustrate this<br /> problem.
8.
  • Åberg, Ingegerd, et al. (författare)
  • Transient waves in nonstationary media
  • 1996
  • Ingår i: Journal of Mathematical Physics. - American Institute of Physics. - 0022-2488. ; 37:5, s. 2229-2252
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper treats propagation of transient waves in nonstationary media, which has many applications in, for example, electromagnetics and acoustics. The underlying hyperbolic equation is a general, homogeneous, linear, first-order 2×2 system of equations. The coefficients in this system depend on one spatial coordinate and time. Furthermore, memory effects are modeled by integral kernels, which, in addition to the spatial dependence, are functions of two different time coordinates. These integrals generalize the convolution integrals, frequently used as a model for memory effects in the medium. Specifically, the scattering problem for this system of equations is addressed. This problem is solved by a generalization of the wave splitting concept, originally developed for wave propagation in media which are invariant under time translations, and by an imbedding or a Green&#39;s functions technique. More explicitly, the imbedding equation for the reflection kernel and the Green&#39;s functions (propagator kernels) equations are derived. Special attention is paid to the problem of nonstationary characteristics. A few numerical examples illustrate this problem.
  •  
9.
  • Alayon Glazunov, Andres, et al. (författare)
  • Branch cross-correlation in presence of spatially selective interference Expressed in Terms of the spherical vector wave expansion of the electromagnetic field
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • In this paper we present an analysis of the cross-correlation coe±cient between signals at two antennabranches (ports) in the presence of spatially selective interference and additive white gaussian noise. Morespeci¯cally, we look at a §45± slanted polarization diversity arrangement, which is rotated around the axisperpendicular to the plane containing the antennas. Results are provided as a function of the rotation angle.The analysis is based on the spherical vector wave multi-pole expansion of both the ¯eld impinging on theantennas and the antenna radiation properties.
10.
  • Alayon Glazunov, Andres, et al. (författare)
  • On the mean effective gain expressed in terms of the spherical vector wave expansion of the electromagnetic field
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • The mode expansion o®ers a general framework for the analysis of the interaction between antennas andpropagation channels. In this paper, the Mean E®ective Gain (MEG) of an antenna is expressed in termsof the spherical vector wave expansion of the electromagnetic ¯eld. An explicit expression of the MEG isprovided as a function of the normalized average power of modes excited in the propagation channel andthe correlation between the channel modes due to the polarization and spatial selectivity of plane wavesimpinging at the antenna.
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 245
Åtkomst
fritt online (135)
Typ av publikation
konferensbidrag (82)
rapport (74)
tidskriftsartikel (63)
bokkapitel (9)
annan publikation (7)
bok (6)
visa fler...
proceedings (redaktörskap) (3)
samlingsverk (redaktörskap) (1)
visa färre...
Typ av innehåll
refereegranskat (136)
övrigt vetenskapligt (107)
populärvet., debatt m.m. (2)
Författare/redaktör
Gustafsson, Mats, (66)
Sohl, Christian (42)
Rikte, Sten (25)
Karlsson, Anders (21)
Larsson, Christer (16)
visa fler...
Derneryd, Anders (15)
Wellander, Niklas (11)
Sihvola, Ari (11)
Persson, Kristin, (10)
Wall, David J. N. (10)
Molisch, Andreas (8)
Nordebo, Sven, (8)
Andersson, Michael (8)
Fridén, Jonas (8)
Ioannidis, Andreas, (8)
Åberg, Ingegerd (6)
Bernland, Anders (6)
Lau, Buon Kiong (5)
Bach Andersen, Jørge ... (5)
Tufvesson, Fredrik (4)
Alayon Glazunov, And ... (4)
Ying, Zhinong (4)
Bolin, Thomas (4)
Plicanic, Vanja (4)
Cheney, Margaret (4)
Abdelmassih Waller, ... (3)
Wall, David (3)
Cronberg, Nils (3)
Olsson, Peter (3)
Bernekorn, Peter (3)
Olsson, Kjell-Arne (3)
Otterheim, Henrik (3)
Rosengren, Frida (3)
Åkerberg, Martin (3)
Lindell, Ismo V. (3)
Nilsson, Nils-Otto (3)
Gustavsson, Magnus, (2)
Waller, Peter (2)
Cismasu, Marius (2)
Malmqvist, Lennart (2)
Egorov, Igor (2)
Weston, Vaughan H (2)
Stewart, Rodney D. (2)
Friden, Jonas (2)
Fuks, Peter (2)
Larson, Gunnar (2)
Stratis, Ioannis (2)
Kreider, Kevin (2)
Corones, J. P. (2)
visa färre...
Lärosäte
Lunds universitet (245)
Linnéuniversitetet (6)
Kungliga Tekniska Högskolan (4)
Umeå universitet (3)
Chalmers tekniska högskola (2)
Språk
Engelska (238)
Svenska (7)
Forskningsämne (UKÄ/SCB)
Teknik (241)
Naturvetenskap (12)

År

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy