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  • Instrumentation and Photography  (1)
  • non-linear finite elements  (1)
  • 2000-2004  (2)
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  • 2000-2004  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Space debris 2 (2000), S. 225-232 
    ISSN: 1572-9664
    Keywords: failure criteria ; high velocity impacts ; non-linear finite elements ; space debris ; spall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Spall caused by hypervelocity impacts at the lower range of velocities could result in significant damage to spacecraft. A number of polycrystalline alloys, used in spacecraft manufacturing, exhibit a pronounced anisotropy in their mechanical properties. The aluminium alloy AA 7010, whose orthotropy is a consequence of the meso-scale phase distribution or grain morphology, has been chosen for this investigation. The material failure observed in plate impact was simulated using a number of spall models. The Hugoniot elastic limit and spall strength have been studied as a function of orientation, and compared to experimental results.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2018-06-06
    Description: Micro-pulse lidar (MPL) systems are small, autonomous, eye-safe lidars used for continuous observations of the vertical distribution of cloud and aerosol layers. Since the construction of the first MPL in 1993, procedures have been developed to correct for various instrument effects present in MPL signals. The primary instrument effects include afterpulse, laser-detector cross-talk, and overlap, poor near-range (less than 6 km) focusing. The accurate correction of both afterpulse and overlap effects are required to study both clouds and aerosols. Furthermore, the outgoing energy of the laser pulses and the statistical uncertainty of the MPL detector must also be correctly determined in order to assess the accuracy of MPL observations. The uncertainties associated with the afterpulse, overlap, pulse energy, detector noise, and all remaining quantities affecting measured MPL signals, are determined in this study. The uncertainties are propagated through the entire MPL correction process to give a net uncertainty on the final corrected MPL signal. The results show that in the near range, the overlap uncertainty dominates. At altitudes above the overlap region, the dominant source of uncertainty is caused by uncertainty in the pulse energy. However, if the laser energy is low, then during mid-day, high solar background levels can significantly reduce the signal-to-noise of the detector. In such a case, the statistical uncertainty of the detector count rate becomes dominant at altitudes above the overlap region.
    Keywords: Instrumentation and Photography
    Format: application/pdf
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