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  • Other Sources  (2)
  • 1975-1979  (2)
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  • 1
    facet.materialart.
    Unknown
    Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing. The membrane functions as the ground plate of a parallel plate capacitor, the other plate being a dc biased electrode recessed approximately 10 microns from the electrically grounded membrane. An ultrasonic wave incident on the membrane varies the membrane-electrode gap spacing and generates an electrical signal proportional to the wave amplitude. The entire assembly is sealed for immersion in a liquid environment. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 15 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. The use of the ESAT as a broadband ultrasonic transducer in liquids with a predictable frequency response is promising.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 50; Jan. 197
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    The structure and the magnetic field of Uranus (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The two-layer model of Uranus is recalculated using a rotation period of 24 rather than 10.8 hours and also the melting temperatures of H2O and of the constituents of the core are evaluated. It appears that the core is solid and the H2O-containing mantle is liquid. The conductivities of H2O, 'metallic' H2 and metallic H are roughly in the ratio of 1:100:10000 so that the convective velocities required for the operation of a dynamo would have to be about 10, 0.1 and 0.001 cm/sec, respectively. The very low thermal flux from Uranus suggests that, unless a precessional dynamo is invoked, metallically conducting H2 or metallic hydrogen has to be present in the mantle.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Aug. 197
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
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