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Results for “parameter correlations”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A Comparison of Properties of Quasars with and without Rapid Broad Absorption Line Variability

We investigate the correlation between rest-frame UV flux variability of broad absorption line (BAL) quasars and their variability in BAL equivalent widths (EWs) in a various timescale from <10 days to a few years in the quasar rest frame. We use the data sets of BAL EWs taken by the Sloan Digital Sky Survey Reverberation Mapping project and photometric data taken by the intermediate Palomar Transient Factory in the g and R bands and the Panoramic Survey Telescope and Rapid Response System in grizy bands. Our results are summarized as follows: (1) the distributions of flux variability versus BAL variability show weak, moderate, or a strong positive correlation; (2) there is no significant difference in flux variability amplitudes between BAL quasars with significant short timescale EW variability (called class S1) and without (class S2); (3) in all timescales considered in this paper, the class S1 quasars show systematically larger BAL variability amplitudes than those of the class S2 quasars; and (4) there are possible correlations between BAL variability and physical parameters of the quasars such as black hole masses (moderate positive), Eddington ratios, and accretion disk temperature (strong negative) in the class S2 quasars. These results indicate that the BAL variability requires changing in the ionizing continuum and an ancillary mechanism such as variability in X-ray shielding gas located at the innermost region of an accretion disk.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Evidence for Cosmic Acceleration Is Robust to Observed Correlations between Type Ia Supernova Luminosity and Stellar Age

Type Ia supernovae (SNe Ia) are powerful standardizable candles for constraining cosmological models and provided the first evidence of the accelerated expansion of the universe. Their precision derives from empirical correlations, now measured from >1000 SNe Ia, between their luminosities, light-curve shapes, colors, and most recently with the stellar mass of their host galaxy. As mass correlates with other galaxy properties, alternative parameters have been investigated to improve SN Ia standardization though none have been shown to significantly alter the determination of cosmological parameters. We re-examine a recent claim, based on 34 SN Ia in nearby passive host galaxies, of a 0.05 mag Gyr -1 dependence of standardized SN Ia luminosity on host age, which, if extrapolated to higher redshifts, would be a bias up to 0.25 mag, challenging the inference of dark energy. We reanalyze this sample of hosts using both the original method and a Bayesian hierarchical model and find after a fuller accounting of the uncertainties the significance of a dependence on age to be ≤2σ and ~1σ after the removal of a single poorly sampled SN Ia. Here, to test the claim that a trend seen in old stellar populations can be applied to younger ages, we extend our analysis to a larger sample that includes young hosts. We find the residual dependence of host age (after all standardization typically employed for cosmological measurements) to be consistent with zero for 254 SNe Ia from the Pantheon sample, ruling out the large but low significance trend seen in passive hosts.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1973

Monitoring the vernal advancement and retrogradation (green wave effect) of natural vegetation

The author has identified the following significant results. The Great Plains Corridor rangeland project utilizes natural vegetation systems as phenological indicators of seasonal development and climatic effects upon regional growth conditions. A method has been developed for quantitative measurement of vegetation conditions over broad regions using ERTS-1 MSS data. Radiance values recorded in ERTS-1 spectral bands 5 and 7, corrected for sun angle, are used to compute a band ratio parameter which is shown to be correlated with green biomass and vegetation moisture content. This report details the progress being made toward determining factors associated with the transformed vegetation index (TVI) and limitations on the method. During the first year of ERTS-1 operation (cycles 1-20), an average of 50% usable ERTS-1 data was obtained for the ten Great Plains Corridor test sites.

Rouse, J. W., Jr.↗
NASA NTRS1974

Monitoring vegetation systems in the Great Plains with ERTS

The Great Plains Corridor rangeland project utilizes natural vegetation systems as phenological indicators of seasonal development and climatic effects upon regional growth conditions. A method has been developed for quantitative measurement of vegetation conditions over broad regions using ERTS-1 MSS data. Radiance values recorded in ERTS-1 spectral bands 5 and 7, corrected for sun angle, are used to compute a band ratio parameter which is shown to be correlated with aboveground green biomass on rangelands.

Rouse, J. W., Jr.↗
NASA NTRS1975

A study of cosmic rays on the artificial moon satellites Luna-11 and Luna-12

In the period from the end of August 1966 to January 1967 the primary cosmic radiation fluxes beyond the terrestrial magnetosphere were measured by means of the equipment mounted on the satellites Luna-11 and Luna-12. The altitude dependence of cosmic rays near the lunar surface as well as the intensity of protons and electrons of solar origin in the moon's vicinity were determined. The correlation of proton intensity with the parameters characterizing the solar and geomagnetic activities and the specific features of the angular distribution of the proton flux as revealed during measurements are given. Data on electron fluxes studied on September 1 and 8, 1966, when short term increases in the electron intensity were observed are included.

Grigorov, N. L.↗
NASA NTRS1975

Measurements and analysis of aircraft airframe noise

Flyover measurements of the airframe noise of AeroCommander, JetStar, CV-990, and B-747 aircraft are presented. Data are shown for both cruise and landing configurations. Correlations between airframe noise and aircraft parameters are developed and presented. The landing approach airframe noise for the test aircraft was approximately 10 EPNdB below present FAA certification requirements.

Putnam, T. W.↗
NASA NTRS1975

Atmospheric corrections for satellite water quality studies

Variations in the relative value of the blue and green reflectances of a lake can be correlated with important optical and biological parameters measured from surface vessels. Measurement of the relative reflectance values from color film imagery requires removal of atmospheric effects. Data processing is particularly crucial because: (1) lakes are the darkest objects in a scene; (2) minor reflectance changes can correspond to important physical changes; (3) lake systems extend over broad areas in which atmospheric conditions may fluctuate; (4) seasonal changes are of importance; and, (5) effects of weather are important, precluding flights under only ideal weather conditions. Data processing can be accomplished through microdensitometry of scene shadow areas. Measurements of reflectance ratios can be made to an accuracy of plus or minus 12%, sufficient to permit monitoring of important eutrophication indices.

Piech, K. R.↗
NASA NTRS1975

Scattering from specular surfaces

Diffraction by nearly specular Guassian surfaces is discussed according to the Beckmann Treatment and Fourier optics. It is shown that the fundamental parameters beta, the RMS roughness and correlation T, the correlation distance can be determined by scattering measurements.

Finkel, M. W.↗
NASA NTRS1975

Studies on the toxic elements and organic degradation products in aquatic bodies and sediments around Kennedy Space Center (KSC) Haulover Canal and Mosquito Lagoon

The work during the first year ending September, 1975, is reported. Indian River, Haulover Canal, Mosquito Lagoon, and other aquatic areas of discharge around Kennedy Space Center (KSC) were studied. The presentation and interpretation of data on water and sediment samples collected from Haulover Canal and Mosquito Lagoon are included. The field and laboratory data are presented and tentative conclusions were drawn in the various aspects of the study. An attempt was made to correlate the physical, chemical, and biological parameters.

Ghuman, G. S.↗
NASA NTRS1976

An empirical model for the mixing of a row of dilution jets with a confined crossflow

An empirical model has been developed for predicting the temperature distribution downstream of a row of cool jets injected normal to a hot confined crossflow. The model is based on the assumption that all properly non-dimensionalized vertical temperature profiles can be expressed in a self-similar form. The scaling parameters in this form have been correlated in terms of the independent flow and geometric variables. The effect of parametric variation of each of the independent variables on the experimental and predicted profiles are examined. The predicted distributions show excellent agreement with the data over a wide range of the independent variables.

Holdeman, J. D.↗
NASA NTRS1976

Chemical vapor deposition growth

A laboratory type CVD reactor system with a vertical deposition chamber and sample pedestal heated by an external RF coil has been extensively modified by installation of mass flow controllers, automatic process sequence timers, and special bellows-sealed air-operated valves for overall improved performance. Various film characterization procedures, including classical metallography, SEM analyses, X ray diffraction analyses, surface profilometry, and electrical measurements (resistivity, carrier concentration, mobility, spreading resistance profiles, and minority-carrier lifetime by the C-V-t method) area used to correlate Si sheet properties with CVD parameters and substrate properties. Evaluation procedures and measurements are given. Experimental solar cell structures were made both in epitaxial Si sheet (on sapphire substrates) and in polycrystalline material on alumina substrates, the former to provide an indication of what might be an upper limit on performance of the latter. Preliminary results are given, as obtained in cell structures not specially designed to allow for the unique properties of the sheet material, and fabricated in material known to be far from optimum for photovoltaic performance. Low power conversion efficiencies have been obtained in the epitaxial as well as the polycrystalline Si sheet.

Ruth, R. P.↗
NASA NTRS1976

The human operator in manual preview tracking /an experiment and its modeling via optimal control/

A manual preview tracking experiment and its results are presented. The preview drastically improves the tracking performance compared to zero-preview tracking. Optimal discrete finite preview control is applied to determine the structure of a mathematical model of the manual preview tracking experiment. Variable parameters in the model are adjusted to values which are consistent to the published data in manual control. The model with the adjusted parameters is found to be well correlated to the experimental results.

Tomizuka, M.↗
NASA NTRS1977

An analysis of the first two years of GASP data

Distributions of mean ozone levels from the first two years of data from the NASA Global Atmospheric Sampling Program (GASP) show spatial and temporal variations in agreement with previous measurements. The standard deviations of these distributions reflect the large natural variability of ozone levels in the altitude range of the GASP measurements. Monthly mean levels of ozone below the tropopause show an annual cycle with a spring maximum which is believed to result from transport from the stratosphere. Correlations of ozone with independent meteorological parameters, and meteorological parameters obtained by the GASP systems show that this transport occurs primarily through cyclogenesis at mid-latitudes.

Holdeman, J. D.↗
NASA NTRS1978

Electron paramagnetic resonance studies of slowly tumbling vanadyl spin probes in nematic liquid crystals

An analysis of EPR line shapes by the method of Polnaszek, Bruno, and Freed is made for slowly tumbling vanadyl spin probes in viscous nematic liquid crystals. The use of typical vanadyl complexes as spin probes for nematic liquid crystals is shown to simplify the theoretical analysis and the subsequent interpretation. Rotational correlation times tau and orientational ordering parameters S sub Z where slow tumbling effects are expected to be observed in vanadyl EPR spectra are indicated in a plot. Analysis of the inertial effects on the probe reorientation, which are induced by slowly fluctuating torque components of the local solvent structure, yield quantitative values for tau and S sub Z. The weakly ordered probe VOAA is in the slow tumbling region and displays these inertial effects throughout the nematic range of BEPC and Phase V. VOAA exhibits different reorientation behavior near the isotropic-nematic transition temperature than that displayed far below this transition temperature.

Bruno, G. V.↗
NASA NTRS1978

An experimental study of the influence of elevated buoyancy levels on flame spread rate over thermally thin cellulosic materials

The role of buoyancy on the flame spread rate over paper and its effect on extinction was studied by changing the gravity level and pressure. It was found that the flame spread rate decreases as the buoyancy induced flow increases. A method for correlating flame spread data using dimensionless parameters is presented. The Damkohler number is shown to be the dependent variable.

Shang, P. C.↗
NASA NTRS1979

Geosynchronous satellite operating anomalies caused by interaction with the local spacecraft environment

The dependence of a spacecraft anomaly or event upon geophysical parameters established on the basis of statistical analysis is presented. Examples are provided for establishing relationships between events and parameters such as geomagnetic activity, local time, and events on other spacecraft. Examples illustrated the potential dangers of not using quantitative statistical techniques it was recommended that the data collection planning and statistical analysis planning be done together. Results demonstrate a high correlation between the events and the goephysical parameter being investigated.

Grajek, M. A.↗
NASA NTRS1978

Global crop production forecasting - A simulation analysis of the data system problems and their solutions

Alternative data systems for a global crop production forecasting system were studied with the aid of a unique simulation facility called the Data System Dynamic Simulator (DSDS). Information system requirements were determined and compared with existing and planned data systems, and deficiencies were identified and analyzed. A first step was to determine the data load for an operational global crop production forecasting system as a function of data frequency, crop types, biophases, cloud coverage, and number of satellites. The DSDS was used to correlate the interrelated influence of orbital parameters, crop calendars, and cloud conditions to generate global data loading profiles. Some of the more important conclusions and the main features of the simulation system are presented.

Golden, H.↗