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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Meteorological adjustment of yearly mean values for air pollutant concentration comparison

Using multiple linear regression analysis, models which estimate mean concentrations of Total Suspended Particulate (TSP), sulfur dioxide, and nitrogen dioxide as a function of several meteorologic variables, two rough economic indicators, and a simple trend in time are studied. Meteorologic data were obtained and do not include inversion heights. The goodness of fit of the estimated models is partially reflected by the squared coefficient of multiple correlation which indicates that, at the various sampling stations, the models accounted for about 23 to 47 percent of the total variance of the observed TSP concentrations. If the resulting model equations are used in place of simple overall means of the observed concentrations, there is about a 20 percent improvement in either: (1) predicting mean concentrations for specified meteorological conditions; or (2) adjusting successive yearly averages to allow for comparisons devoid of meteorological effects. An application to source identification is presented using regression coefficients of wind velocity predictor variables.

Sidik, S. M.↗
NASA NTRS1976

Monitoring wheat growth with radar

The scattering properties of wheat in the 8-18 GHz band were studied as a function of frequency, polarization, incidence angle, and crop maturity. Supporting ground truth was collected at the time of measurement. The data indicate the radar backscattering coefficient is sensitive to both radar system parameters and crop characteristics, particularly at incidence angles near nadir. Linear regression analysis of the backscattering coefficient (dB) on both time and plant moisture content result in rather good correlation, as high as 0.9, with the slope of these regression lines being 0.55 dB/day and -0.275 dB% plant moisture at 9.4 GHz at nadir. It is found that the coefficient undergoes rapid variations shortly before and after the wheat is harvested. Both of these analyses suggest methods for estimating wheat maturity and for monitoring the progress of harvest.

Bush, T. F.↗
NASA NTRS1976

Palus Somni - Anomalies in the correlation of Al/Si X-ray fluorescence intensity ratios and broad-spectrum visible albedos

The positive correlation between Al/Si X-ray fluorescence intensity ratios determined during the Apollo 15 lunar mission and a broad-spectrum visible albedo of the moon is quantitatively established. Linear regression analysis performed on 246 1 degree geographic cells of X-ray fluorescence intensity and visible albedo data points produced a statistically significant correlation coefficient of .78. Three distinct distributions of data were identified as (1) within one standard deviation of the regression line, (2) greater than one standard deviation below the line, and (3) greater than one standard deviation above the line. The latter two distributions of data were found to occupy distinct geographic areas in the Palus Somni region.

Clark, P. E.↗
NASA NTRS1977

Application of LANDSAT system for improving methodology for inventory and classification of wetlands

The author has identified the following significant results. LANDSAT and aircraft data were compared for differences in absolute numbers of water bodies in the two data sets. This comparison was done using a linear regression analysis. The coefficients of determination were 0.65 and 0.74 for data of May and July, respectively. Standard statistical procedures were used to adjust the LANDSAT pond counts to actual pond numbers based on regression relationships.

Gilmer, D. S.↗
NASA NTRS1977

Utility of correlation techniques in gravity and magnetic interpretation

Internal correspondence uses Poisson's Theorem in a moving-window linear regression analysis between the anomalous first vertical derivative of gravity and total magnetic field reduced to the pole. The regression parameters provide critical information on source characteristics. The correlation coefficient indicates the strength of the relation between magnetics and gravity. Slope value gives delta j/delta sigma estimates of the anomalous source. The intercept furnishes information on anomaly interference. Cluster analysis consists of the classification of subsets of data into groups of similarity based on correlation of selected characteristics of the anomalies. Model studies are used to illustrate implementation and interpretation procedures of these methods, particularly internal correspondence. Analysis of the results of applying these methods to data from the midcontinent and a transcontinental profile shows they can be useful in identifying crustal provinces, providing information on horizontal and vertical variations of physical properties over province size zones, validating long wavelength anomalies, and isolating geomagnetic field removal problems.

Chandler, V. W.↗
NASA NTRS1982

Low-latitude cloudiness and climate feedback - Comparative estimates from satellite data

Three studies of the relative albedo to the IR components of cloud amount feedback are reviewed, and an approach to the seasonal variability in low-level cloud numbers is presented. Comparisons are made and uncertainties calculated for the predictions of cloud amounts from satellite data sets for outgoing IR flux. IR data is used directly for a linear regression analysis and seasonal and latitudinal variations are considered in terms of monthly-annual means for particular latitude zones. Investigations of NOAA-NESS satellite data revealed that cirrus clouds are transparent in the 10.5-12.5 microns range and cloud albedos decrease at wavelengths greater than 0.7 micron, which suggests a possibility of cloud-sky and clear-sky albedo comparisons at 0.5-0.7 micron. The inclusion of Rayleigh scattering and atmospheric water vapor absorption of sunlight is recommended to test the effects on observed contracts.

Cess, R. D.↗
NASA NTRS1984

Radiometric calibration and processing procedure for reflective bands on LANDSAT-4 protoflight Thematic Mapper

The radiometric subsystem of NASA's LANDSAT-4 Thematic Mapper (TM) sensor is described. Special emphasis is placed on the internal calibrator (IC) pulse shapes and timing cycle. The procedures for the absolute radiometric calibration of the TM channels with a 122-centimeter integrating sphere and the transfer of radiometric calibration from the channels to the IC are reviewed. The use of the IC to calibrate TM data in the ground processing system consists of pulse integration, pulse averaging, IC state identification, linear regression analysis, and histogram equalization. An overview of the SCROUNGE-era (before August 1983) method is presented. Procedural differences between SCROUNGE and the TIPS-era (after July 1983) and the implications of these differences are discussed.

Barker, J. L.↗
NASA NTRS1984

Estimating sunspot number

An empirical method is developed to predict certain parameters of future solar activity cycles. Sunspot cycle statistics are examined, and curve fitting and linear regression analysis techniques are utilized.

Wilson, R. M.↗
NASA NTRS1984

The temporal behavior of upper stratospheric ozone at low latitudes - Evidence from Nimbus 4 BUV data for short-term responses to solar ultraviolet variability

Ozone mixing ratios at pressure levels near 2 mbar are analyzed for the purpose of estimating the average response of the upper stratospheric ozone to solar UV variability on the time scale of the solar rotation period. The data were obtained from observations made with the Nimbus 4 backscattering UV radiometer in 13 latitude zones between 65 degrees N and 65 degrees S. The anaysis showed that temporal variations are negatively correlated with changes in zonally averaged equivalent temperature measured simultaneously by Nimbus 4 radiometer. A linear regression analysis is performed in order to obtain estimates of the average percent change of ozone at low latitudes, on the considered time scale for given changes in 10.7-cm flux, and in the UV flux model developed by Lean et al. (1982). Reproductions of the ozone profiles are provided.

Hood, L. L.↗
NASA NTRS1985

Sea surface temperature - Observations from geostationary satellites

Multispectral image data acquired from the VISSR atmospheric sounder (VAS) on the geostationary GOES satellites were used to estimate sea surface temperatures (SST). A procedure was developed to screen VAS visible and infrared data for cloud-free regions for estimation of SST from the clear infrared radiances. A data set of matches between the VAS radiances and high quality buoy estimates of SST was produced. A linear regression analysis of these matches was performed to generate an empirical algorithm relating the VAS window channel brightness temperatures to the estimates of SST recorded by NOAA fixed environment buoys. Daily maps of SST during Hurricanes Alicia (1983) and Debbie (1982) demonstrated the ability of VAS to monitor air-sea interactions at high temporal and spatial scales.

Bates, J. J.↗
NASA NTRS1986

Correlations between Nimbus-7 Scanning Multichannel Microwave Radiometer data and an antecedent precipitation index

Passive microwave brightness temperatures from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) can be used to infer the soil moisture content over agricultural areas such as the southern Great Plains of the United States. A linear regression analysis between three transforms of the five dual polarized SMMR wavelengths of 0.81, 1.36, 1.66, 2.80 and 4.54 cm and an antecedent precipitation index representing the precipitation history showed correlation coefficients greater than 0.90 for pixel aggregates of 25-50 km. The use of surface air temperatures to approximate the temperature of the emitting layer was not required to obtain high correlation coefficients between the transforms and the antecedent precipitation index.

Wilke, G. D.↗
NASA NTRS1987

Phase error statistics of a phase-locked loop synchronized direct detection optical PPM communication system

Receiver timing synchronization of an optical Pulse-Position Modulation (PPM) communication system can be achieved using a phased-locked loop (PLL), provided the photodetector output is suitably processed. The magnitude of the PLL phase error is a good indicator of the timing error at the receiver decoder. The statistics of the phase error are investigated while varying several key system parameters such as PPM order, signal and background strengths, and PPL bandwidth. A practical optical communication system utilizing a laser diode transmitter and an avalanche photodiode in the receiver is described, and the sampled phase error data are presented. A linear regression analysis is applied to the data to obtain estimates of the relational constants involving the phase error variance and incident signal power.

Natarajan, Suresh↗
NASA NTRS1987

Calibration of the spin-scan ozone imager aboard the dynamics Explorer 1 satellite

The calibration technique, which contains the calibrated backscattered radiance values necessary for performing the calibrations, is presented. The calibration constants for September to October 1981 to determine total columnar ozone from the Spin-Scan Ozone Imager (SOI), which is a part of the auroral imaging instrumentation aboard the Dynamics Explorer 1 Satellite, are provided. The precision of the SOI-derived total columnar ozone is estimated to be better than 2.4 percent. Linear regression analysis was used to calculate correlation coefficients between total columnar ozone obtained from Dobson ground stations and SOI which indicate that the SOI total columnar ozone determination is equally accurate for clear or cloudy weather conditions.

Bressette, Walter E.↗
NASA NTRS1987

Effect of alloy composition on the sodium-sulfate induced hot corrosion attack of cast nickel-base superalloys at 900 C

The effects of Cr, Al, Ti, Mo, Ta, Nb, and W content on the hot corrosion of Ni-base alloys were examined experimentally. The superalloys were tested for 300 1-hr cycles at 900 C in a Mach 0.3 burner rig flame containing 0.5 ppmw sodium. The data reveal that the best corrosion resistance is obtained when the Cr content is greater than 12 percent; however, good resistance is detected in some alloys with Cr content less than 10 percent provided that the Al content is less than 2.5 wt pct and the Ti content is less than 4 wt pct. It is observed that the influence of W, Ta, Mo, and Nb content on resistance is dependent on Al and Ti contents. The derivation of an equation for estimating hot corrosion attack as a function of alloy composition using multiple linear regression analysis is described. The applicability of the equation is tested using various data sets of alloys. It is noted that the equation can be used to explain the effects of alloy composition on attack rates.

Stearns, C. A.↗
NASA NTRS1987

Echocardiographic measurements of left ventricular mass by a non-geometric method

The accuracy of a new nongeometric method for calculating left ventricular myocardial volumes from two-dimensional echocardiographic images was assessed in vitro using 20 formalin-fixed normal human hearts. Serial oblique short-axis images were acquired from one point at 5-deg intervals, for a total of 10-12 cross sections. Echocardiographic myocardial volumes were calculated as the difference between the volumes defined by the epi- and endocardial surfaces. Actual myocardial volumes were determined by water displacement. Volumes ranged from 80 to 174 ml (mean 130.8 ml). Linear regression analysis demonstrated excellent agreement between the echocardiographic and direct measurements.

Parra, Beatriz↗
NASA NTRS1988

Comparison of aerobic fitness and space motion sickness during the Shuttle program

Space motion sickness (SMS) is an important problem for short-duration space flight; 71 percent of STS crewmembers develop SMS symptoms. The search for effective countermeasures and factors that correlate with sensitivity has been extensive. Recently, several investigators have linked aerobic fitness with motion sickness sensitivity in the 1-G or high-G environment. This paper compares the aerobic fitness of 125 Shuttle crewmembers with their SMS symptom category. Aerobic fitness data were obtained from the exercise tolerance test conducted nearest the time of launch. SMS data were derived from the medical debrief summaries. Mean maximum oxygen consumption values for crewmembers in four SMS categories (none, mild, moderate, severe) were 44.55, 44.08, 46.5, and 44.24 ml/kg per min, respectively. Scattergrams with linear regression analysis, comparing aerobic fitness and SMS symptom classification are presented. Correlation coefficients comparing SMS categories vs. aerobic fitness for men and women reveal no definite relationship between the two factors.

Jennings, Richard T.↗
NASA NTRS1988

A modified ATI technique for nowcasting convective rain volumes over areas

This paper explores the applicability of the area-time-integral (ATI) technique for the estimation of the growth portion only of a convective storm (while the rain volume is computed using the entire life history of the event) and for nowcasting the total rain volume of a convective system at the stage of its maximum development. For these purposes, the ATIs were computed from the digital radar data (for 1981-1982) from the North Dakota Cloud Modification Project, using the maximum echo area (ATIA) no less than 25 dBz, the maximum reflectivity, and the maximum echo height as the end of the growth portion of the convective event. Linear regression analysis demonstrated that correlations between total rain volume or the maximum rain volume versus ATIA were the strongest. The uncertainties obtained were comparable to the uncertainties which typically occur in rain volume estimates obtained from radar data employing Z-R conversion followed by space and time integration. This demonstrates that the total rain volume of a storm can be nowcasted at its maximum stage of development.

Makarau, Amos↗
NASA NTRS1990

Modeling Solar Lyman Alpha Irradiance

Solar Lyman alpha irradiance is estimated from various solar indices using linear regression analyses. Models developed with multiple linear regression analysis, including daily values and 81-day running means of solar indices, predict reasonably well both the short- and long-term variations observed in Lyman alpha. It is shown that the full disk equivalent width of the He line at 1083 nm offers the best proxy for Lyman alpha, and that the total irradiance corrected for sunspot effect also has a high correlation with Lyman alpha.

Pap, J.↗