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  • 1995-1999  (3)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 165 (1996), S. 1-11 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent solar observations at Pic du Midi are reported that yield a value of J 2=(2.57 ± 2.36) x 10−6 for the quadrupole moment of the Sun. These observations were conducted from July 1993 to July 1994 after several improvements of the scanning heliometer. This instrument operates by fast photoelectric scans of opposite limbs of the Sun quasi-simultaneously, which provides the distance between both inflection points of the limb profiles. Any number of solar diameters in any position angle can be measured within a time interval short enough to minimize the scattering of the observational parameters. Errors due to atmospheric deterioration are discussed. From our results, compared to previous values obtained by other authors, it can be concluded than an upper limit for J 2 is probably 1.0 × 10-5.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 172 (1997), S. 11-18 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract For more than a decade, it has been suggested that the diameter of the Sun may vary in time. This not only concerns variations of the equatorial diameter, but also any other diameters. Thus the complete geometry of the Sun is may be not as ideal as a perfect sphere. The aim of this paper is to briefly review up to now the figure of the Sun, to deduce an upper bound to the solar oblateness (if any). To sum up over the last 15 years, the amplitude of the observed variations of the solar radius made at the Calern Observatory (France) does not exceed 0.7′ and has been probably less (0.3′) during the last five years. Recently, new measurements of the solar oblateness made at the Pic du Midi Observatory (France) seems to confirm a possible oscillation with the solar cycle, as previously conjectured by a Princeton group. Furthermore, an upper bound to the solar oblateness can be derived from the observations and compared with theoretical computations of the angular momentum of the Sun. Let us mention that between July 1993 and July 1994 the reported mean value difference between the equatorial radius and the polar one is 11.5 \± 3.4 arc ms, consistent with previous observations. Effects of the atmosphere are briefy discussed. Helioseismic measurements should eventually place useful limits on the strength and uniformity of the internal magnetic fields which may be responsible for the solar surface changes of different oscillation modes. A knowledge of the physical character of such an oscillation of the geometry of the Sun is still pending (rapidly rotating core?), as well as the question of this out-of-roundness of our nearby star.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 499-508 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Glass beads carrying different amounts of polystyrene (PS) grafted to their surface were prepared by solution and melt-mixing processes. These beads are mixed with a nearly mono-disperse PS. The morphology of polymers filled with different volume amounts, φ, of modified and unmodified glass beads was investigated by scanning electron microscopy (SEM). In the case of PS-grafted glass beads, the fracture surfaces show cohesive failure. The rheological properties of these filled polymers were investigated by mechanical spectroscopy. The material functions, the storage modulus G″ and the loss modulus G″, for PS melts filled with unmodified beads can be presented in an invariant from, e.g., independent of temperature and concentration. The temperature-shift factors follow WLF behavior, and the concentration shift factors a generalized Maron Pierce equation. The rheological material functions of melts filled with modified glass beads can be superposed for different temperatures. However, a concentration invariant representation is only possible in the frequency range belonging to the plateau region. For small frequencies, a systematic deviation occurs whose strength depends on the amount of polymer grafted to the filler surface. It is argued that this behavior may be attributed to an additional relaxation process originating from the hindered flow of the modified glass beads. This process has to be investigated in more detail in the future. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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