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  • ASTROPHYSICS  (2)
  • Engineering  (1)
  • 2000-2004
  • 1985-1989  (3)
  • 1985  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 21 (1985), S. 1295-1314 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Three formulations of the boundary element method (BEM) and one of the Galerkin finite element method (FEM) are compared according to accuracy and efficiency for the spatial discretization of two-dimensional, moving-boundary problems based on Laplace's equation. The same Euler-predictor, trapezoid-corrector scheme for time integration is used for all four methods. The model problems are on either a bounded or a semi-infinite strip and are formulated so that closed-form solutions are known. Infinite elements are used with both the BEM and FEM techniques for the unbounded domain. For problems with the bounded region, the BEM using the free-space Green's function and piecewise quadratic interpolating functions (QBEM) is more accurate and efficient than the BEM with linear interpolation. However, the FEM with biquadratic basis functions is more efficient for a given accuracy requirement than the QBEM, except when very high accuracy is demanded. For the unbounded domain, the preferred method is the BEM based on a Green's function that satisfies the lateral symmetry conditions and which leads to discretization of the potential only along the moving surface. This last formulation is the only one that reliably satisfies the far-field boundary condition.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2011-08-19
    Description: The interpretation of the infrared excess from Alpha Lyrae as seen by the Infrared Astronomy Satellite in terms of thermal emission from a circumstellar shell of large particles follows from the recognition that small dust grains would be removed from the vicinity of the star by radiation pressure and Poynting-Robertson drag. However, this explanation is viable only if there is no resupply of small grains via mass loss from Alpha Lyr itself. Radio-continuum observations were used to constrain the stellar mass loss to less than 3.4 x 10 to the -10th solar mass/yr. The observations thus support the conclusion that the infrared excess is due to residual solid matter from the prestellar nebula.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 294; 646-648
    Format: text
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  • 3
    Publication Date: 2019-06-28
    Description: Comet 1983d was named IRAS-Araki-Alcock in honor of its codiscoverers, including the Infrared Astronomical Satellite (IRAS) and two amateur astronomers. It is pointed out that the apparition of Comet 1983d was the closest cometary approach to earth since the development of modern astronomy. Because of the evolution of electromagnetic detector technology, a large range of ground-based observations of this object were possible. In the present investigation, attention is given to observations and some interpretations of the spectrum of Comet IRAS-Araki-Alcock in the wavelength region from 1.5 to 20 microns. In addition to the observations made with a bolometer and discrete filters, spectrophotometric observations were made of the nuclear condensation of Comet 1983d in the 1.5- to 2.6-micron wavelength region at 5 percent resolution.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 62; 273-281
    Format: text
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