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  • 1990-1994  (4)
  • 1990  (4)
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  • 1990-1994  (4)
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  • 1
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    The compressible vortex pair (1990)
    Cambridge University Press
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    Publication Date: 1990-11-01
    Description: A numerical solution for the flow field associated with a compressible pair of counter-rotating vortices is developed. The compressible, two-dimensional potential equation is solved utilizing the numerical method of Osher et al. (1985) for flow regions in which a non-zero density exists. Close to the vortex centres, vacuum ‘cores’ develop owing to the existence of a maximum achievable flow speed in a compressible flow field. A special treatment is required to represent these vacuum cores. Typical streamline patterns and core boundaries are obtained for upstream Mach numbers as high as 0.3, and the formation of weak shocks, predicted by Moore & Pullin (1987), is observed. © 1990, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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    PAPER CURRENT
  • 2
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    A case for subgenera in a foraminiferal classification (1990)
    Copernicus
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    Publication Date: 1990-07-01
    Description: There has been a progression in palaeobiological classifications from the more primitive empirical “stamp collecting” stage where similar shapes were grouped together, to the more sophisticated phylogenetic classifications where supposed genetically related foraminiferal taxa are categorised together. But how do we know that certain extinct taxa were genetically related? This is a major problem where a number of factors interplay together: a belief in evolution, the experience of the operator and consequent recognition of phyletic lineages. In the study of Cenozoic planktonic foraminifera we are fortunate to have recognised a number of now well established lineages; also we have some data on amino-acids found in the tests of living species (King and Hare, 1972) which range back well into the Neogene. These latter data not only provide us with essential genetic information but they also give us confidence when dealing with the classification of extinct species.So how do we build this evolutionary knowledge into a classification? Clearly, genetically related species can be grouped together into subgenera, and related subgenera into broader genera. In their classification Loeblich and Tappan (1988) held a different view and decided not to use subgenera because (1) their usage produces an unwieldy classification, and (2) lineage concepts change when additional data are collected. If we follow their classification, then when you read about Globorotalia menardii, Globorotalia fohsi and Globorotalia hirsuta you could assume that they are closely related; this is not true. The three species have similar test morphologies but these have resulted from iterative. . .
    Print ISSN: 0262-821X
    Electronic ISSN: 2041-4978
    Topics: Geosciences
    Published by Copernicus on behalf of Micropalaeontological Society.
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  • 3
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    Codeless GPS Applications to Multi-Path: CGAMP (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Cordless Global Positioning System (GPS) Applications to Multi-Path (CGAMP) is meeting the challenge of exploiting the L-band signals from the Global Positioning System (GPS) satellites for the measurement of the impulse response of radio transmission channels over space-Earth paths. This approach was originally suggested by E. K. Smith and has been pursued by J. Lemmon, without an affordable implementation being identifiable. In addition to the high cost of a suitable P code correlating GPS receiver, there is also the major impediment of the often announced Department of Defense policy of selective availability/anti-spoof (SA/AS) that clouds reliable access to the wideband (20 MHz) P channel of the GPS signals without cryptographic access. A technique proposed by MacDoran utilizes codeless methods for exploiting the P channel signals implemented by the use of a pair of antennas and cross correlation signal detection.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, California Inst. of Tech.,Proceedings of; JPL, California Inst
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    The compressible vortex pair (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A numerical solution for the flow field associated with a compressible pair of counter-rotating vortices is developed. The compressible, two-dimensional potential equation is solved utilizing the numerical method of Osher et al. (1985) for flow regions in which a non-zero density exists. Close to the vortex centers, vacuum 'cores' develop owing to the existence of a maximum achievable flow speed in a compressible flow field. A special treatment is required to represent these vacuum cores. Typical streamline patterns and core boundaries are obtained for upstream Mach numbers as high as 0.3, and the formation of weak shocks, predicted by Moore and Pullin (1987), is observed.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 220; 339-354
    Format: text
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