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Träfflista för sökning "WFRF:(Bååth L.B. 1948 ) "

Sökning: WFRF:(Bååth L.B. 1948 )

  • Resultat 1-10 av 71
  • [1]234567...8Nästa
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1.
  • Möllerström, Erik, et al. (författare)
  • Noise directivity from a vertical axis wind turbine
  • 2015
  • Ingår i: Proceedings of the 6th International Conference on Wind Turbine Noise 2015. - New Brighton, UK : INCE/Europe.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • The directivity of wind turbine noise is of widespread interest and has received attention over an extended period. The reason for this is partly that noise optimization procedures can be implemented in order to increase the efficiency of the power output. Although directivity of horizontal axis wind turbines (HAWTs) are well understood, the directivity pattern around vertical axis wind turbines (VAWTs) are less well investigated.This paper presents measurements of directivity on a 200 kW VAWT, a so called H-rotor, with variable speed and a tower height of 40 m. The turbine, which is situated in a flat agricultural landscape close to Falkenberg at the Swedish west coast, is one of the world’s largest today operational VAWTs. Experimental results as well as a theoretical model based on the turbulent-boundary-layer trailing-edge (TBL-TE) noise suggest higher noise levels upwind of the rotor and the lowest noise levels in the perpendicular directions. Moreover, modulation analysis of the measurements indicates the presence of modulations but the results are inconclusive.
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2.
  • Akujor, Chidi E., et al. (författare)
  • Combined-Array Imaging of Extra-Galactic Radio Sources
  • 1994
  • Ingår i: Astronomy with Millimeter and Submillimeter Wave Interferometry. - San Francisco : Astronomical Society of the Pacific. - 0937707783 ; , s. 123-124
  • Konferensbidrag (refereegranskat)
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3.
  • Bartel, N., et al. (författare)
  • The Compact Radio Source 2021+614 : Simultaneous 2.3 and 8.3 GHz Mark III VLBI Observations
  • 1984
  • Ingår i: Astrophysical Journal. - Philadelphia, PA : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 279:1, s. 116-121
  • Tidskriftsartikel (refereegranskat)abstract
    • Second-epoch VLBI observations of the flat-spectrum radio source 2021+614 made simultaneously at 2.3 and 8.3 GHz with the Mark III system are reported. The maps derived from these observations reveal a complex, frequency-dependent radio structure on the milliarcsecond scale. The object has four nearly collinear components oriented at a position angle of about 35 degrees and embedded in an extended region. Two of these are optically thin, one has a flat spectrum, and the other appears to be synchrotron self-absorbed in the frequency range 2.3-8.3 GHz. No significant structural variation is found at either frequency between epochs separated by about three years. The formal estimate of the transverse velocity between two components, one with a flat and the other with an inverted spectrum, is v/c = 0.7 + or - 2.3. Remarkable similarities between 2021+614 and the unusual source 0316+413 are discussed.
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4.
  • Booth, R. S., et al. (författare)
  • High-resolution observations of quasars from the Parkes +/- 4 deg. sample
  • 1979
  • Ingår i: Monthly notices of the Royal Astronomical Society. - Oxford : Oxford University Press. - 0035-8711 .- 1365-2966. ; 188, s. 159-163
  • Tidskriftsartikel (refereegranskat)abstract
    • VLBI observations of 20 compact quasars have been made between Jodrell Bank and Onsala at a frequency of 1666 MHz. Twelve of the quasars have inverted or peaked spectra at centimetre wavelengths and these are all unresolved, having angular diameters of less than 0.015 arcsec. Two out of five quasars with overall flat spectra are partially resolved on this scale size, as are three steep-spectrum quasars.
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5.
  • Borkowski, Kazimierz M., et al. (författare)
  • Determination of the Toruń Antenna Position from VLBI Observations
  • 1992
  • Ingår i: Acta Astronomica. - Warsaw : Fundacja Astronomii Polskiej im. Mikolaja Kopernika / Copernicus Foundation for Polish Astronomy. - 0001-5237. ; 42, s. 371-375
  • Tidskriftsartikel (refereegranskat)abstract
    • Four strong radio sources were observed over a 12-hr session in March, 1990 between radio telescopes at Onsala and Torun at wavelength of 6 cm in the standard VLBI Mark II setup for the purpose of improving the coordinates of the Torun 15-meter antenna. The Cartesian coordinates of the antenna derived from the presented measurements are (in meters): 3638609.62 +/- 0.19, 1221773.23 +/- 0.54 and 5077024.50 +/- 1.66 in the x, y, and z directions, respectively.
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6.
  • Bååth, L.B. 1948-, et al. (författare)
  • 0735+178 : The cosmic conspiracy
  • 1991
  • Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 250:1, s. 50-56
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper discusses a radio outburst in the BL Lac-object 0735+178 which started in early 1988, ended during 1990 and was succeeded by a new outburst which is still in progress. Our image obtained with a global VLBI network shows the source to mainly consist of a core-jet like structure ending in diffuse emission region of low surface brightness located to the east of the core. We identify two new components as having been produced during the late 1980's. They are moving out with apparent superluminal motion in a viewing angle of greater-than-or-similar-to 10-degrees at a distance of less-than-or-similar-to 2 mas from the core. The core includes another new component, but our resolution is just sufficient to resolve out this component from the core at our epoch of observation. We suggest that the weak emission region is caused by an older component reaching the point at which the Doppler boosting is at its maximum and that the long time scale flux variation are due to successive events when evolved components reach that point.
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7.
  • Bååth, L.B. 1948- (författare)
  • A closer look at active galactic nuclei — the great engines of the universe
  • 1992
  • Ingår i: Physica scripta. T. - Stockholm, Sweden : Kungliga Vetenskapsakademien. - 0281-1847. ; T43, s. 57-66
  • Tidskriftsartikel (refereegranskat)abstract
    • The intensive radio emission from powerful radio galaxies and quasars Make these attractive candidates to become "standard candles" to probe the Universe. This paper discusses this possibility and the physics of the radio sources.
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8.
  • Bååth, L.B. 1948- (författare)
  • AGN Variability and VLBI
  • 1994
  • Ingår i: Multi-Wavelength Continuum Emission of Agn. - Dordrecht : Kluwer Academic Publishers. - 0792327446 - 0792327454 ; , s. 181-186
  • Bokkapitel (refereegranskat)abstract
    • This contribution discusses the connection between variability in radio and optical with structural variations observed with VLBI. Structural changes do not have to start in the core, and intensity variations may be caused by components in the jet outside the core. The scenario is probably more complicated than present day theories assume.
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9.
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10.
  • Bååth, L.B. 1948-, et al. (författare)
  • EVN as a phase stable interferometer
  • 1991
  • Ingår i: Radio Interferometry. - San Francisco, USA : Astronomical Society of the Pacific Conference. - 0937707384 - 9780937707388 ; , s. 298-301
  • Konferensbidrag (refereegranskat)
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  • Resultat 1-10 av 71
  • [1]234567...8Nästa
 
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