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  • Articles: DFG German National Licenses  (2)
  • 1970-1974  (2)
  • 1974  (1)
  • 1970  (1)
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  • Articles: DFG German National Licenses  (2)
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  • 1970-1974  (2)
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  • 1
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Long, reverberating trains of seismic waves produced by impacts and moonquakes may be interpreted in terms of scattering in a surface layer overlying a non-scattering elastic medium. Model seismic experiments are used to qualitatively demonstrate the correctness of the interpretation. Three types of seismograms are found, near impact, far impact and moonquake. Only near impact and moonquake seismograms contain independent information. Details are given in the paper of the modelling of the scattering processes by the theory of diffusion. Interpretation of moonquake and artificial impact seismograms in two frequency bands from the Apollo 12 site indicates that the scattering layer is 25 km thick, with a Q of 5000. The mean distance between scatterers is approximately 5 km at 25 km depth and approximately 2 km at 14 km depth; the density of scatterers appears to be high near the surface, decreasing with depth. This may indicate that the scatterers are associated with cratering, or are cracks that anneal with depth. Most of the scattered energy is in the form of scattered surface waves.
    Type of Medium: Electronic Resource
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  • 2
    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: Elastomers, based on cellulose fibers, were synthesized by grafting ethyl acrylate onto fibers preirradiated by a high-energy electron beam. The rheological properties and fine structure of the elastomers were investigated in order to determine factors in development of rubber-like elastomeric behavior. Mechanical properties of the elastomers depended on (1) degree of polymerization of irradiated cellulose molecules, (2) extent of grafting, and (3) experimental methods of evaluation, particularly in varying environmental conditions, for example, in making measurements in air, water, or ethyl acetate. Glass transition temperatures of the elastomers were dependent on the environmental conditions of evaluation; stiffnesses of the elastomers levelled off at about 0°C; and in all environments, a rubber-like plateau was observed. Poly(ethyl acrylate) separated from the elastomers was not soluble in acetone. The mean molecular weight of the separated poly(ethyl acrylate) of the elastomer was determined in ethyl acetate by the equilibrium swelling method. It was concluded that crosslinks existed in the elastomers. Electron microphotographs of cross sections of the elastomers, which exhibited rubber-like behavior, indicated that the fibrillar structure of the irradiated cellulose fibers formed a uniform network and that poly(ethyl acrylate) was uniformly distributed among the fibrils.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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