| 1. |
- Karlsson, Anders, et al.
(författare)
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Transient wave propagation in gyrotropic media
- 1992
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Ingår i: Invariant inbedding and inverse problems. - 0898713056 ; , s. 77-89
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Bokkapitel (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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| 2. |
- Karlsson, Anders, et al.
(författare)
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Wave splitting and imbedding equations for a spherically symmetric dispersive medium
- 1992
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Ingår i: Invariant inbedding and inverse problems. - 0898713056 ; , s. 103-113
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Bokkapitel (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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| 3. |
- Angerbjörn, Anders, et al.
(författare)
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Dietary Variation in Arctic Foxes (Alopex-Lagopus) - an Analysis of Stable Carbon Isotopes
- 1994
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Ingår i: Oecologia. ; 99:3-4, s. 226-232
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Tidskriftsartikel (refereegranskat)abstract
- We used stable carbon isotopes to analyse individual variation in arctic fox diet. We extracted collagen from bones (the lower jaw), and measured stable carbon isotopes. The foxes came from three different localities: Iceland, where both microtines and reindeer are rare; west Greenland, where microtines are absent; and Sweden, where seat analyses showed the primary food to be microtine rodents and reindeer. The Icelandic samples included foxes from both coastal and inland habitats, the Swedish sample came from an inland area, and the Greenland sample from coastal sites. The spatial variation in the isotopic pattern followed a basic division between marine and terrestrial sources of protein. Arctic foxes from inland sites had delta(13)C values of -21.4 (Ice land) and -20.4 parts per thousand (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine Values of -14.9 parts per thousand, whereas coastal foxes from Iceland had intermediate values of -17.7 parts per thousand. However, there was individual variation within each sample, probably caused by habitat heterogeneity and territoriality among foxes. The variation on a larger scale was related to the availability of different food items. These results were in accordance with other dietary analyses based on seat analyses. This is the first time that stable isotopes have been used to reveal individual dietary patterns. Our study also indicated that isotopic values can be used on a global scale.
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| 4. |
- Kristensson, Gerhard, et al.
(författare)
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Time domain inversion techniques for electromagnetic scattering problems
- 1992
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Ingår i: Invariant imbedding and inverse problems. - 0898713056 ; , s. 1-29
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a review of and a comparison between two different methods to solve an inverse scattering problem in the time domain. The problem is that of propagation of transient electromagnetic waves in spatially inhomogeneous slabs of finite length. The permittivity and conductivity profiles are assumed to vary only with depth and the scattering problem is thus onedimensional. Several algorithms to solve the direct and inverse scattering problems for continuous and discontinuous permittivity profiles are suggested. Some of these algorithms have not been published before. The aim of this paper is to compare and review these methods. More specifically, the numerical performance of the invariant imbedding approach (layer-stripping)and the Green functions formulation (downward continuation)is compared. Some new results based upon time reversal techniques for a lossless slab are presented in an appendix.
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| 5. |
- LIDEN, F, et al.
(författare)
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ALIGNMENT PROCESSES IN CS-119, CS-121 AND CS-123
- 1992
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 550:2, s. 365-390
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Tidskriftsartikel (refereegranskat)abstract
- Rotational band structures have been observed in the odd-A Cs isotopes 119Cs, 121Cs and 123Cs. The previously known bands have been extended to higher spin values and several new bands have been established. Alignments of both h11/2 protons and neutrons are seen. Of special interest are the alignment frequencies in the (tentative) [422]3/2+ and [404]9/2+ bands which indicate a configuration-dependent proton pairing. Furthermore, the variation of the interaction strength at the first band crossing in the h11/2 bands does not follow the standard cranked-shell-model predictions. This feature is in line with previous systematic observations of alignment processes in high-j intruder bands, and might infer an additional band mixing due to a neutron-proton interaction.(~)[GRAPHICS]
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