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  • AERODYNAMICS  (764)
  • INSTRUMENTATION AND PHOTOGRAPHY
  • 1985-1989
  • 1975-1979  (1,218)
  • 1978  (616)
  • 1977  (602)
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Years
  • 1985-1989
  • 1975-1979  (1,218)
Year
  • 1
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    Real time reflectometer (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A real time reflectometer with the particular utility of measuring fairly rapid (transient) changes in the specular reflectance of a sample which is continuously exposed to a perturbing environment is described. A fixed radiation source, a fixed detector, a uniformly rotating sample wheel, and a uniformly rotating optical wheel protect against misalignment problems. The reflectometer operates by comparing the measurings of a reflected signal with that of a reference signal made within fractions of a second of one another. Reflectance is measured in the infrared, visible, and vacuum ultraviolet regions.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Theoretical response of condenser microphones (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Modifications to prior theory yield expressions for the frequency response and equivalent lumped elements of a condenser microphone in terms of its fundamental geometrical and material properties. Results of the analysis show excellent agreement with experimental data taken on B&K pressure microphone types 4134 and 4146.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Acoustical Society of America; vol. 64
    Format: text
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  • 3
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    A high-temperature wideband pressure transducer (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A condenser microphone AM carrier system, which has been developed to measure pressure fluctuations at elevated temperatures, consists of the following components: a condenser microphone designed for operation at elevated temperatures; existing carrier electronics developed under two previous research grants but adapted to meet present requirements; a 6 m cable operating as a half-wavelength transmission line between the microphone and carrier electronics; and a voltage-controlled oscillator used in a feedback loop for automatic tuning control. Both theoretical and practical aspects of the development program are considered. The three predominant effects of temperature changes are changes in the membrane-backplate gap, membrane tension, and air viscosity. The microphone is designed so that changes in gap and membrane tension tend to have compensating effects upon the microphone sensitivity.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-149789 , PGSTR-PH77-48
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Optical polarimetry of particulate surfaces (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Reflection polarimetry is a remote-sensing tool sensitive to the refractive index and microtexture of solid surfaces. Mechanisms producing linear polarization within a rough, porous, or particulate surface are discussed, and laboratory techniques for precise measurements are described in some detail. Polarimetry of atmosphereless solar-system bodies provides valuable indications of albedo for objects too small and distant for direct diameter determinations, and reveals that even quite small asteroids and satellites have particulate surfaces
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical polarimetry: Instrumentation and applications; Seminar; Aug 23, 1977 - Aug 24, 1977; San Diego, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Wake flow measurements with a mobile laser Doppler velocimeter system (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Wake flow measurements were conducted with a mobile laser Doppler velocimeter (LDV). The measurements included surveys of aircraft wake vortices behind a B-747 aircraft, aircraft carrier wake measurements from aboard the U.S.S. Nimitz, and tower wake measurements for a 100 kW wind turbine. Results of these tests demonstrated that a mobile ground-based LDV is a versatile and useful tool for the measurement of full-scale three-dimensional wake flows. The potential is demonstrated for utilization of this system to study complex wakes for a variety of applications.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 78-823 , Aerodynamic Testing Conference; Apr 19, 1978 - Apr 21, 1978; San Diego, CA
    Format: text
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  • 6
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    Simultaneous velocity and particle size measurement in two phase flows by Laser Anemometry (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A technique for particle size measurement by using Laser Doppler Anemometry is discussed. An additional gate photomultiplier has been introduced at right angles to the optical axis in order to select only those particles passing through the central region of the measurement control volume. Particle sizing measurements have been made in sprays of glass particles using the modified Laser Anemometry system. Measurements in fuel sprays are also reported and compared with the results obtained by a photographic technique. The application of the particle sizing technique to opaque particles is investigated and suitable optical arrangements are suggested. Light scattering characteristics of Laser Anemometry systems for different optical geometries are calculated to select the optimum optical arrangement for the particle sizing measurements.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 78-74 , Aerospace Sciences Meeting; Jan 16, 1978 - Jan 18, 1978; Huntsville, AL
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Particle size and velocity measurement by laser anemometry (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The use of a forward scattering Laser Anemometer system for the measurement of particle diameters larger than the fringe spacing is investigated. A systematic calibration experiment demonstrates a direct relationship between signal amplitude and particle diameter for transparent particles between 30 microns and 240 microns in diameter. A light scattering analysis confirms these measurements and indicates how the range of particles which can be measured using the peak (mean) signal depends on the optical arrangement and particle properties. On the basis of this work a real time Laser Anemometer signal processor is modified so that the peak of the mean of each signal can be measured. A method of correcting data for the effect of particles which do not go through the center of the measurement volume is derived. Good agreement is found between particle size distributions measured in sprays by using the Laser Anemometer and size distributions measured by collecting the particles on a slide and using an image analysis computer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 77-214 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Unsteady transonic flow computations (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The numerical procedures previously developed for computing nonlinear and time-linearized small-perturbation unsteady transonic flows are briefly reviewed, and the effects of unsteady modes of motion on two-dimensional transonic flows are evaluated. The numerical procedure used comprises an alternating-direction implicit scheme and treats shock waves as discontinuities in the flow. Comparison of the time-linearized results with fully nonlinear calculations delineates their range of applicability. The unsteady behavior due to harmonic pitching and flap oscillations of an NACA airfoil is also examined.
    Keywords: AERODYNAMICS
    Type: Symposium on Unsteady Aerodynamics; Sept. 26-28, 1977; Ottawa; Canada
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Versatile LDV burst simulator (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A device for generating burst signals is reported that can be used to determine whether or not a laser Doppler velocimeter is operating properly. A high frequency signal which corresponds to the information frequency of the laser Doppler velocimeter is modulated by a low frequency signal to provide an envelope for the high frequency signal. The high frequency signal is modulated by any modulator means such as, for example, an analog multiplier. The low frequency signal is added to the modulated signal to provide pedestals for the resulting series of burst pulses. The means are provided for selecting different combinations of these burst signals. Also means are provided for making the burst signals asymmetrical as desired. In addition, means are provided for varying the frequencies, and amplitudes of the information, envelope and pedestal frequency signals in the burst signals.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Photodiode and photomultiplier areal sensitivity anomalies (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Several silicon photodiodes and photomultipliers were tested to determine signal variations as a light spot was scanned over the photosensitive surface of these detectors. Qualitative and quantitative data is presented to demonstrate the areal sensitivity anomalies. These anomalies are related back to the fabrication techniques of the manufacturers.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Southeast Region 3 Conference; Apr 04, 1977 - Apr 06, 1977; Williamsburg, VA
    Format: text
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