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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Observing stellar coronae with the Goddard High Resolution Spectrograph. 1: The dMe star AU microscopoii

We report on an observation of AU Mic taken with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The data consist of a rapid sequence of spectra covering the wavelength range 1345-1375 A with a spectral resolution of 10,000. The observations were originally intended to search for spectral variations during flares. No flares were detected during the 3.5 hr of monitoring. A method of reducing the noise while combining the individual spectra in the time series is described which resulted in the elimination of half of the noise while rejecting only a small fraction of the stellar signal. The resultant spectrum was of sufficient quality to allow the detection of emission lines with an integrated flux of 10(exp -15) ergs/sq cm(sec) or greater. Lines of C I, O I, O V, Cl I, and Fe XXI were detected. This is the first indisputable detection of the 1354 A Fe XXI line, formed at T approximately = 10(exp 7) K, on a star other than the Sun. The line was well resolved and displayed no significant bulk motions or profile asymmetry. From the upper limit on the observed line width, we derive an upper limit of 38 km/s for the turbulent velocity in the 10(exp 7) K plasma. An upper limit is derived for the flux of the 1349 A Fe XII line, formed at T approximately = 1.3 x 10(exp 6) K. These data are combined with contemporaneous GHRS and International Ultraviolet Explorer (IUE) data to derive the volume emission measure distribution of AU Mic over the temperature range 10(exp 4)-10(exp 7) K. Models of coronal loops in hydrostatic equilibrium are consistent with the observed volume emission measures of the coronal lines. The fraction of the stellar surface covered by the footprints of the loops depends upon the loop length and is less than 14% for lengths smaller than the stellar radius. From the upper limit to the estimated width of the Fe XXI line prfile we find that the we cannot rule out Alfven wave dissipation as a possible contributor to the required quiescent loop heating rate.

Maran, S. P.↗
NASA NTRS1978

The capability of satellite borne remote sensors to measure stratospheric trace constituents. Volume 1: Background and requirements

Volume 1 of a three volume report issued as MITRE/METREX Technical Report is presented. This volume contains a synthesis of the results of two previous MITRE/METREX studies and an update of the information. These studies deal with a comprehensive review of stratospheric trace constituent measurement requirements. The scope of the study was restricted to those contituents which fall into the general category of air pollutants.

Keitz, E. L.↗
NASA NTRS1997

Characterization and Demonstrations of Laser-Induced Incandescence in both Normal and Low-Gravity

Knowledge of soot volume fraction is important to a wide range of combustion studies in microgravity. Laser-induced incandescence (LII) offers high sensitivity, high temporal and spatial resolution in addition to geometric versatility for real-time determination of soot volume fraction. Implementation of LII into the 2.2 see drop tower at The NASA-Lewis Research Center along with system characterization is described. Absolute soot volume fraction measurements are presented for laminar and turbulent gas-jet flames in microgravity to illustrate the capabilities of LII in microgravity. Comparison between LII radial intensity profiles with soot volume fraction profiles determined through a full-field light extinction technique are also reported validating the accuracy of LII for soot volume fraction measurements in a microgravity environment.

VanderWal, Randall L.↗
NASA NTRS2001

[Measurement of left atrial and ventricular volumes in real-time 3D echocardiography. Validation by nuclear magnetic resonance]

The measurement of the left ventricular ejection fraction is important for the evaluation of cardiomyopathy and depends on the measurement of left ventricular volumes. There are no existing conventional echocardiographic means of measuring the true left atrial and ventricular volumes without mathematical approximations. The aim of this study was to test anew real time 3-dimensional echocardiographic system of calculating left atrial and ventricular volumes in 40 patients after in vitro validation. The volumes of the left atrium and ventricle acquired from real time 3-D echocardiography in the apical view, were calculated in 7 sections parallel to the surface of the probe and compared with atrial (10 patients) and ventricular (30 patients) volumes calculated by nuclear magnetic resonance with the simpson method and with volumes of water in balloons placed in a cistern. Linear regression analysis showed an excellent correlation between the real volume of water in the balloons and volumes given in real time 3-dimensional echocardiography (y = 0.94x + 5.5, r = 0.99, p < 0.001, D = -10 +/- 4.5 ml). A good correlation was observed between real time 3-dimensional echocardiography and nuclear magnetic resonance for the measurement of left atrial and ventricular volumes (y = 0.95x - 10, r = 0.91, p < 0.001, D = -14.8 +/- 19.5 ml and y = 0.87x + 10, r = 0.98, P < 0.001, D = -8.3 +/- 18.7 ml, respectively. The authors conclude that real time three-dimensional echocardiography allows accurate measurement of left heart volumes underlying the clinical potential of this new 3-D method.

Non-NASA Center↗
NASA NTRS1985

Simultaneous cabin and ambient ozone measurements on two Boeing 747 airplanes. Volume 3: October 1978 - July 1979

Measurements of ozone concentrations at cruise altitudes both outside and in the cabin of a Boeing 747SP and Boeing 747-100 airliners in routine commercial service are presented. Plotted and tabulated data are identified by route and are arranged chronologically for each airplane. These data were taken at 5- or 10-min intervals by automated instruments used in the NASA Global Atmospheric Sampling Program (GASP). All GASP cabin ozone data obtained from October 1978 to early July 1979 are presented.

Holdeman, J. D.↗
NASA NTRS2000

SeaWIFS Postlaunch Technical Report Series: The SeaWiFS Photometer Revision for Incident Surface Measurement (SeaPRISM) Field Commissioning - Volume 13

This report documents the scientific activities that took place at the Acqua Alta Oceanographic Tower (AAOT) in the northern Adriatic Sea off the coast of Italy from 2-6 August 1999. The ultimate objective of the field campaign was to evaluate the capabilities of a new instrument called the SeaWiFS Photometer Revision for Incident Surface Measurements (SeaPRISM). SeaPRISM is based on a CE-318 sun photometer made by CIMEL Electronique (Paris, France). The CE-318 is an automated, robotic system which measures the direct sun irradiance plus the sky radiance in the sun plane and in the almucantar plane. The data are transmitted over a satellite link, and this remote operation capability has made the device very useful for atmospheric measurements. The revision to the CE-318 that makes the instrument potentially useful for SeaWiFS calibration and validation activities is to include a capability for measuring the radiance leaving the sea surface in wavelengths suitable for the determination of chlorophyll a concentration. The initial evaluation of this new capability involved above- and in-water measurement protocols. An intercomparison of the water-leaving radiances derived from SeaPRISM and an in-water system showed the overall spectral agreement was approximately 8.6%, but the blue-green channels intercompared at the 5% level. A blue-green band ratio comparison was at the 4% level.

Hooker, Stanford B.↗
DOE OSTI2020

Simulating the optical properties of soot using a stochastic soot model

KL extinction measurements are common in literature concerning soot producing sprays because of their nonintrusiveness. Unfortunately, these measurements often rely on bold assumptions of uniform and monodisperse spherical particles. In this work, a Spray A case is simulated using a highly detailed 3D stochastic soot model and the measured and simulated soot volume fraction are compared. Although the simulated volume fraction magnitude is approximately correct, features are much sharper than in the measured data. Optical models based on particle shape are applied to the simulated soot particles to nd the local optical thickness. The modeled optical thickness aligns with the measured volume fraction much more closely than the simulated volume fraction indicating KL extinction measurements are not simply related to soot volume fraction.

Strickland, Tyler↗
NASA NTRS1994

Variability of measured sonic boom signatures. Volume 1: Technical report

Sonic boom signatures from two databases, the BOOMFILE and the XB-70, were analyzed in terms of C-weighted sound exposure level (CSEL), A-weighted sound exposure level (ASEL), and Stevens Mark VII perceived level (PLdB), as well as the more traditional peak positive overpressure and rise time. The variability of these parameters due to propagation through atmosphere was analyzed for different aircraft Mach number and altitude groups. The low Mach number/low altitude group had significantly greater variation in rise time, overpressure, and loudness level than the high Mach number/high altitude group. The loudness of measured booms were found to have a variation of up to 25 dB relative to the loudness of boom predicted for a non-turbulent atmosphere. This is due primarily to the steeper ray paths of the high Mach number/high altitude group and the corresponding shorter distances traveled by these rays through the lower atmosphere resulting in reduced refraction effects. The general trend of decreased overpressure and loudness level with increasing lateral distance was also seen. Sonic boom signatures from early morning flights had less variation in rise time and overpressure than afternoon flights because of reduced turbulence. Measures of asymmetry (difference between compression and expansion portion of the signature) showed that the variability in Delta loudness level was greater than the variability in Delta overpressure due to the large influence of turbulence on rise time. Lastly, analysis of data within 50 percent of lateral cutoff showed that the mean value for overpressure and loudness level was independent of time of day but that the frequency with which it occurred was greater in the morning. This is a clear indicator of increased turbulence in the afternoon.

Elmer, K. R.↗
NASA NTRS1994

Variability of measured sonic boom signatures. Volume 2: Data report

Sonic boom signatures from two databases, the BOOMFILE and the XB-70, were analyzed in terms of C-weighted sound exposure level (CSEL), A-weighted sound exposure level (ASEL), and Stevens Mark VII perceived level (PLdB), as well as the more traditional peak positive overpressure and rise time. The variability of these parameters due to propagation through atmosphere was analyzed for different aircraft Mach number and altitude groups. The low Mach number/low altitude group had significantly greater variation in rise time, overpressure, and loudness level than the high Mach number/high altitude group. The loudness of measured booms were found to have a variation of up to 25 dB relative to the loudness of boom predicted for a non-turbulent atmosphere. This is due primarily to the steeper ray paths of the high Mach number/high altitude group and the corresponding shorter distances traveled by these rays through the lower atmosphere resulting in reduced refraction effects. The general trend of decreased overpressure and loudness level with increasing lateral distance was also seen. Sonic boom signatures from early morning flights had less variation in rise time and overpressure than afternoon flights because of reduced turbulence. Measures of asymmetry (difference between compression and expansion portion of the signature) showed that the variability in Delta loudness level was greater than the variability in Delta overpressure due to the large influence of turbulence on rise time. Lastly, analysis of data within 50 percent of lateral cutoff showed that the mean value for overpressure and loudness level was independent of time of day but that the frequency with which it occurred was greater in the morning. This is a clear indicator of increased turbulence in the afternoon.

Elmer, K. R.↗
NASA NTRS1974

ASRDI oxygen technology survey. Volume 4: Low temperature measurement

Information is presented on temperature measurement between the triple point and critical point of liquid oxygen. The criterion selected is that all transducers which may reasonably be employed in the liquid oxygen (LO2) temperature range are considered. The temperature range for each transducer is the appropriate full range for the particular thermometer. The discussion of each thermometer or type of thermometer includes the following information: (1) useful temperature range, (2) general and particular methods of construction and the advantages of each type, (3) specifications (accuracy, reproducibility, response time, etc.), (4) associated instrumentation, (5) calibrations and procedures, and (6) analytical representations.

Sparks, L. L.↗
NASA NTRS1976

Remote measurement utilizing NASA's scanning laser Doppler systems. Volume 2: Laser Doppler dust devil velocity profile measurement program

The first detailed velocity profile data on thermally induced dust vortices are presented. These dust devils will be analyzed and studied to determine their flow fields and origin in an effort to correlate this phenomena with the generation and characteristics of tornadoes. A continuing effort to increase mankind's knowledge of vortex and other meteorological phenomena will hopefully allow the prediction of tornado occurrence, their path, and perhaps eventually even lead to some technique for their destruction.

Howle, R. E.↗
NASA NTRS1980

Measurements of the sampling volume of an infrared laser doppler velocimeter for the study of feasibility of simultaneous three-dimensional velocity profile mapping

High resolution incoherent mapping of the sampling volume was performed to determine the three dimensional profile of the volume of the beam from which information can be obtained by scattering. The incoherent sampling volume of the infrared laser Doppler velocimeter was found to be heavily dependent upon the configuration of the outgoing laser beam. In general when only half the beam is allowed to focus at the focal plane, the x, y traverses indicate a broader beam with nominal side lobes. However, if the total beam is permitted to impinge on the focal plane there is substantial narrowing of the beam with increased maximum intensity and an increase in side lobes. The double maximum indicated by the coherent sampling volume appears to be an artifact of the scanning process not a fundamental entity of the sampling volume.

Bond, R. L.↗
NASA NTRS1991

The 1983 tail-era data series. Volume 3: Geosynchronous particle measurements

Geosynchronous particle measurements are presented for comparison with same-scale plots of ISEE 3 plasma and field data. Shown for each day are electron and proton fluxes measured with the low-energy-range electron and the low-energy-range proton detectors of the Los Alamos Charged Particle Analyzer. This instrument has flown aboard several geosynchronous orbit satellites, including the three spacecraft from which the presented data were obtained. The presented data are 5-min averages of the integral flux in each of several energy channels.

Fairfield, D. H.↗
NASA NTRS2003

Measurements of Erosion Wear Volume Loss on Bare and Coated Polymer Matrix Composites

An investigation was conducted to examine the erosion behavior of uncoated and coated polymer matrix composite (PMC) specimens subjected to solid particle impingement using air jets. The PMCs were carbon-Kevlar (DuPont, Wilmington, DE) fiber-epoxy resin composites with a temperature capability up to 393 K (248 F). Tungsten carbide-cobalt (WC-Co) was the primary topcoat constituent. Bondcoats were applied to the PMC substrates to improve coating adhesion; then, erosion testing was performed at the University of Cincinnati. All erosion tests were conducted with Arizona road-dust (ARD), impinging at angles of 20 and 90 on both uncoated and two-layer coated PMCs at a velocity of 229 m/s and at a temperature of 366 K (200 F). ARD contains primarily 10-m aluminum oxide powders. Vertically scanning interference microscopy (noncontact, optical profilometry) was used to evaluate surface characteristics, such as erosion wear volume loss and depth, surface topography, and surface roughness. The results indicate that noncontact, optical interferometry can be used to make an accurate determination of the erosion wear volume loss of PMCs with multilayered structures while preserving the specimens. The two-layered (WC-Co topcoat and metal bondcoat) coatings on PMCs remarkably reduced the erosion volume loss by a factor of approximately 10. The tenfold increase in erosion resistance will contribute to longer PMC component lives, lower air friction, reduced related breakdowns, decreased maintenance costs, and increased PMC reliability. The decrease in the surface roughness of the coated vanes will lead to lower air friction and will subsequently reduce energy consumption. Eventually, the coatings could lead to overall economic savings.

Miyoshi, Kazuhisa↗