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  • 11
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    CARS Temperature Measurements in Turbulent and Supersonic Facilities (1991)
    In:  CASI
    Details
    Publication Date: 2018-06-02
    Description: This paper documents the development of the National Aeronautics and Space Administration s (NASA) Langley Research Center ( LaRC) Coherent Antistokes Raman Spectroscopy (CARS) systems for measurements of temperature in a turbulent subsonic or supersonic reacting hydrogen-air environment. Spectra data provides temperature data when compared to a precalculated library of nitrogen CARS spectra. Library validity was confirmed by comparing CARS temperatures derived through the library with three different techniques for determination of the temperature in hydrogen-air combustion and an electrically heated furnace. The CARS system has been used to survey temperature profiles in the simulated flow of a supersonic combustion ramjet (scramjet) model. Measurement results will be discussed.
    Keywords: Fluid Mechanics and Thermodynamics
    Format: application/pdf
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  • 12
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    Supersonic combusting flow - A comparison of numerical and experimental results (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The flow field of an unconfined coaxial supersonic burner (SSB) was obtained numerically, using a CFD code. The explicit MacCormack algorithm, with point implicit treatment of chemistry source terms, was employed in the CFD code. Combustion of hydrogen and air was simulated by a two-step finite-rate combustion model whereas turbulence was accounted for by a Prandtl mixing length scheme. Boundary conditions and some important features of the numerical scheme were discussed. The qualitative features of the numerical solution were compared with those obtained by regular as well as schlieren photographs. General agreements of the CFD solution and the experimental photographs were observed.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 88-0095
    Format: text
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  • 13
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    Comparison of CARS combustion temperatures with standard techniques (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper describes a comparative study of temperatures measured with Coherent Anti-Stokes Raman Spectroscopy (CARS) and those using standard measurement techniques. CARS temperatures from nitrogen vibrational-rotational spectra have been obtained in a premixed hydrogen-air laboratory flame supported on a flat flame burner over a temperature range from about 1000 K to 2100 K. The techniques used for comparison were sodium line reversal, thin wire thermocouples and heat balance calculations. These studies show a good agreement over the entire temperature range studied.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 83-1482
    Format: text
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  • 14
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    Laboratory tank studies of a single species of phytoplankton using a remote sensing fluorosensor (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Phytoplankton were grown in the laboratory for the purpose of testing a remote fluorosensor. The fluorosensor uses a unique four-wavelength dye laser system to excite phytoplankton bearing chlorophyll and to measure the chlorophyll fluorescence generated by this excitation. Six different species were tested, one at a time, and each was grown two to four times. Fluorescence measured by the fluorosensor provides good quantitative measurement of chlorophyll concentrations for all species tested while the cultures were in log phase growth. Fluorescene cross section ratios obtained in the single species tank tests support the hypothesis that the shape of the fluorescence cross section curve remains constant with the species (differences in fluorescence cross section ratios are a basis for determining composition of phytoplankton according to color group when a multiwavelength source of excitation is used. Linear relationships exist between extracted chlorophyll concentration and fluorescence measured by the remote fluorosensor during the log phase growth of phytoplankton cultures tested.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-TP-1821 , L-14140
    Format: application/pdf
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  • 15
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    Visible absorbance spectra: A basis for in situ and passive remote sensing of phytoplankton concentration and community composition (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The concentration and composition of phytoplankton populations are measured by an optical method which can be used either in situ or remotely. This method is based upon the in vivo light absorption characteristics of phytoplankton. To provide a data base for testing assumptions relative to the proposed method, visible absorbance spectra of pure cultures of 20 marine phytoplankton were obtained under laboratory conditions. Descriptive and analytical statistics were computed for the absorbance spectra and were used to make comparisons between members of major taxonomic groups and between groups. Spectral variation between the members of the major taxonomic groups was observed to be considerably less than the spectral variation between these groups. In several cases the differences between the mean absorbance spectra of major taxonomic groups are significant enough to be detected with passive remote sensing techniques.
    Keywords: OCEANOGRAPHY
    Type: NASA-TP-2094 , L-15490 , NAS 1.60:2094
    Format: application/pdf
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  • 16
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    Multiple-laser-energy detection system (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Technique monitors energy output of each of four sequentially-pulsed dye lasers for the Airborne LIDAR Oceanographic Probing Experiment system. Fiber optics attached to output mirrors transmit optical signal proportional to output energy.
    Keywords: PHYSICAL SCIENCES
    Type: LAR-12017 , NASA Tech Briefs (ISSN 0145-319X); 2; 1; P. 3
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  • 17
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    Dye laser remote sensing of marine plankton (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Dye laser, emitting four wavelengths sequentially in time, has been incorporated into helicopter-borne lidar flight package, for performing studies of laser-induced fluorescence of chlorophyll A in algae. Data obtained by multicolor lidar technique can provide water-resource management with rapid-access wide-area coverage of the impact of various environmental factors for any body of water.
    Keywords: LIFE SCIENCES
    Type: LAR-11382
    Format: application/pdf
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  • 18
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    Velocity and thrust measurements in a quasi- steady magnetoplasmadynamic thruster (1970)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Quasi-steady MPD arc thrustor average thrust measurements, considering time-of-flight velocity determination by ion collecting probes
    Keywords: PROPULSION SYSTEMS
    Type: AIAA PAPER 70-1080
    Format: text
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  • 19
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    CARS system for turbulent flame measurements (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Simultaneous nitrogen number density and rotational-vibrational temperatures were measured in a turbulent diffusion flame with a Coherent Anti-Stokes Raman Scattering (CARS) instrument. The fuel jet was diluted with nitrogen (20 percent by volume) to allow temperature measurements across the entire jet mixing region. These measurements were compared with fluid dynamics computations. The CARS system incorporated a neodymium YAG laser, an intensified silicon photodiode array detector, and unique dynamic range enhancement methods. Theoretical calculations were based on a parabolic Navier-Stokes computer code. The comparison of these techniques will aid their development in the study of complex flowfields.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 84-1537
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  • 20
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    Laboratory studies of in vivo fluorescence of phytoplankton (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A lidar system is developed that uses four selected excitation wavelengths to induce chlorophyll 'a' fluorescence which is indicative of both the concentration and diversity of phytoplankton. The operating principles of the system and the results of measurements of phytoplankton fluorescence in a controlled laboratory environment are presented. A comparative study of results from lidar fluorosensor laboratory tank tests using representative species of phytoplankton in single and multispecies cultures from each of four color groups reveals that (1) there is good correlation between the fluorescence of chlorophyll 'a' remotely simulated and detected by the lidar system and in-situ measurements using four similar excitation wavelengths in a flow-through fluorometer; (2) good correlation exists between the total chlorophyll 'a' calculated from lidar-fluorosensor data and measurements obtained by the Strickland-Parsons method; and (3) the lidar fluorosensor can provide an index of population diversity.
    Keywords: OCEANOGRAPHY
    Type: In: Joint Conference on Sensing of Environmental Pollutants; Nov 06, 1977 - Nov 11, 1977; New Orleans, LA
    Format: text
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