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  • INSTRUMENTATION AND PHOTOGRAPHY  (2)
  • OCEANOGRAPHY  (2)
  • ELECTRONIC SYSTEMS  (1)
  • Statistics and Probability  (1)
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Keywords
Years
  • 1
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    The modulation of a radar signal from the ocean surface due to slope and hydrodynamic effects (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The modulation of the signal level of a tower-based radar scatterometer illuminating a small area of the ocean surface is predicted from direct measurements of the hydrodynamic conditions of the ocean surface and compared with X band radar measurements taken simultaneously. The radar backscatter is assumed to be due to Bragg resonance between the signal and the ripple waves. The effects of the slope of the ocean surface due to passing long waves are modeled by converting a measured wave height series into a slope time series. Laser-slope-gauge measurements of the spectrum of the ripple waves that ride upon the long ocean waves are used to predict the hydrodynamic effects. Comparisons with the measured radar signal show that the slope modulation alone gives a poor prediction of the modulation. Inclusion of the hydrodynamic effects in the simulation appears more promising, although it also is not entirely successful with this data set.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 16291-16
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    A system to measure flow moisture content in hypersonic wind tunnels (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The technique and equipment is described which is used for obtaining data on the moisture content in two NASA Langley Hypersonic Wind Tunnels. A detailed description of the sampling system and its operation is presented along with the moisture analyzer used. The procedure used for converting dew point to parts of water per million by volume (ppmv) is included with graphs that show tunnel moisture content at various pressures.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-107628 , NAS 1.15:107628
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Optical Detection Of Flameout In A Combustor (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Fuel supply shut down in time to prevent explosion. Optical flameout detector designed to signal control system of facility to cut off supply of fuel into combustion chamber if flame goes out. Combustor which optical flameout detector designed burns methane in air to provide hot gases for 8-ft high-temperature test chamber. Acoustical flameout detector for same combustor described in "Acoustical Detection of Flameout in Combustor" (LAR-14900). Fiber optic probes mounted to fuel-spray bar upstream of flame. No focusing optics used, and probes aimed across flow of gases at spot on combustion chamber wall downstream from spray bar. Arrangement enables flameout detection system to respond quickly to potential loss of flame since it detects movement of flame front away from spray bar face. Overall response time of detection system under 10 milliseconds.
    Keywords: ELECTRONIC SYSTEMS
    Type: LAR-14997 , NASA Tech Briefs (ISSN 0145-319X); 18; 11; P. 48
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Synthetic-aperture-radar imaging of the ocean surface using the slightly-rough facet model and a full surface-wave spectrum (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A new model of synthetic-aperture-radar (SAR) imaging of ocean waves is described. The model is based on mapping individual, slightly-rough surface facets through the SAR processor into the image and responses of the facets in the image domain are added together coherently to give the composite image. A windowing technique allows both the orbital motion and the phase velocity of the long waves to be included. It is determined that the azimuthal cut-off is due to a smearing of the response of the facets in the image induced by the random orbital motion of the intermediate large-scale waves and that the focus adjustment that gives the greatest image contrast is half the phase velocity of the dominant long wave. The optimal processing technique, however, may consist of spatially offsetting the multiple looks on the image domain to compensate the propagation of long waves during the integration time of the SAR.
    Keywords: OCEANOGRAPHY
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 11; 1451-148
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Optical flameout detector (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A device has been developed which monitors the presence of a flame within a combustion chamber. The optical flameout detection system responds to gross changes in combustor light intensity, which is monitored in two spectral bands. A photomultiplier tube makes optical measurements in the ultraviolet portion of the spectrum, and a silicon photodiode covers the visible region. The detectors, located outside the combustion chamber, receive the light energy radiated from the combustion process through fiber optic probes designed to operate in a high pressure environment. The optical fibers are aimed diagonally through the center of the injector at the combustion chamber wall downstream of the injector. The probes observe events occurring within a narrow conical-shaped field of view so that the system can quickly detect longitudinal movement of the flame front away from the injector. If a change in intensity of the flame is detected, the fuel supply to the combustion chamber is shut off, limiting the amount of unburned fuel in the combustion chamber which could reignite.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NAS 1.71:LAR-14997-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Modal Q Factor and Modal Overlap of Electrically Small Avionics Box (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Estimating the electromagnetic field strength in avionics boxes and other small enclosures at the design stage requires an estimate of the Q factor of the cavity modes. When the enclosure is small, it is typically under-moded so that Q measurement techniques which are standard practice in over-moded reverberation chambers may not be a robust measure. Furthermore, practical antenna used to measure Q in a small cavity may have a strong influence on the result obtained, as reported by Tait et al, IEEE Trans. EMC 55 2 2012. This paper reports the results of testing to determine the Q factor of a small aperture enclosure, used in a statistical power balance model to predict the electric field strength. The contributors to the total Q are identified. A novel S(sub 11) curve fitting method to measure modal Q is introduced and compared with the time domain method for measuring Q.
    Keywords: Statistics and Probability
    Type: KSC-E-DAA-TN59105 , IEEE Symposium on Electromagnetic Compatibility, Signal & Power Integrity (EMC+SIPI); Jul 20, 2018 - Aug 03, 2018; Long Beach, CA; United States
    Format: application/pdf
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