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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Systematics in auroral energy spectra.

Observation of a systematic increase in the mean energy of auroral electrons as the total precipitated energy increases. The change in 4278-A N2(+) intensity from about 50 R to about 10 kR correlates better with the change in mean energy of the precipitating electrons than with the change in number flux. Nightside aurora that exhibit this property superimpose on a wide region of soft (less than or about equal to 1 keV) precipitation that extends from the equatorial boundary of aurora to well poleward of normal visible aurora. On the dayside, the soft 'cusp' precipitation generates the statistical oval, although there may be larger energy inputs equatorward of the oval.

Eather, R. H.↗
NASA NTRS1972

The systematic evolution of a NASA software technology, Appendix C

A long range program is described whose ultimate purpose is to make possible the production of software in NASA within predictable schedule and budget constraints and with major characteristics such as size, run-time, and correctness predictable within reasonable tolerances. As part of the program a pilot NASA computer center will be chosen to apply software development and management techniques systematically and determine a set which is effective. The techniques will be developed by a Technology Group, which will guide the pilot project and be responsible for its success. The application of the technology will involve a sequence of NASA programming tasks graduated from simpler ones at first to complex systems in late phases of the project. The evaluation of the technology will be made by monitoring the operation of the software at the users' installations. In this way a coherent discipline for software design, production maintenance, and management will be evolved.

Deregt, M. P.↗
NASA NTRS1973

Multidimensional analysis of fast-spectrum material replacement measurements for systematic estimation of cross section uncertainties

A series of central core and core-reflector interface sample replacement experiments for 16 materials performed in the NASA heavy-metal-reflected, fast spectrum critical assembly (NCA) were analyzed in four and 13 groups using the GAM 2 cross-section set. The individual worths obtained by TDSN and DOT multidimensional transport theory calculations showed significant differences from the experimental results. These were attributed to cross-section uncertainties in the GAM 2 cross sections. Simultaneous analysis of the measured and calculated sample worths permitted separation of the worths into capture and scattering components which systematically provided fast spectrum averaged correction factors to the magnitudes of the GAM 2 absorption and scattering cross sections. Several Los Alamos clean critical assemblies containing Oy, Ta, and Mo as well as one of the NCA compositions were reanalyzed using the corrected cross sections. In all cases the eigenvalues were significantly improved and were recomputed to within 1 percent of the experimental eigenvalue. A comparable procedure may be used for ENDF cross sections when these are available.

Klann, P. G.↗
NASA NTRS1973

Systematic two-dimensional cascade tests. Volume 4: Cascade test data

The data pertaining to the performance characteristics of hydrofoils are presented. The hydrofoils are: (1) double circular arc, (2) multiple circular arc, and (3) slotted doubled circular arc. The experimental data are organized into a systematic presentation format and provided with scale factors and reference values for interpretation. The data include local pressure distributions upstream and downstream of the cascade test section, continuous records from flow angle and total pressure surveys, hydrofoil local pressure distributions, and cavitation data.

Murrin, T. A.↗
NASA NTRS1973

Rb-Sr systematics for chemically defined Apollo 15 and 16 materials

Concentrations of Rb and Sr and the Sr87/86 ratios are determined in a large number of Apollo 15 samples, including KREEP basalts, mare basalts, anorthosite breccia clasts, lithic fragments, a spinel-bearing clast, green glass samples, breccia matrix, and soils. Relative concentrations of Sm, Eu, Rb, and Sr are also examined in the samples, with particular attention to Rb/Sr systematics vs other trace element abundances and total chemical compositions of rocks. Analysis of crystalline KREEP samples rich in trace elements indicates that the differentiation of these rocks has extended to -4.25 AE age, a significantly later time than the presumed time of accretion of the moon.

Nyquist, L. E.↗
NASA NTRS1974

Are stellar surface heavy-element abundances systematically enhanced

Stellar surface heavy-element abundances may be substantially higher than interior abundances if there is appreciable accretion of chemically fractionated matter after Hayashi-phase convection has terminated. The plausibility of appreciable accretion is discussed, and some possible observational consequences of enhanced surface heavy-element abundances are investigated. These consequences include a reduced solar neutrino flux, systematic variations in surface abundance along the main sequence and along the giant branch, and relatively low heavy-element abundances among planetary nebulas and white dwarfs and in the interstellar medium. There is marginal observational evidence in support of the hypothesis of enhanced stellar surface heavy-element abundances.

Joss, P. C.↗
NASA NTRS1974

Aplanatic two-mirror telescopes: A systematic study. I - Cassegrainian configuration

A systematic performance analysis of aplanatic Cassegrainian telescopes has been accomplished by means of a ray trace program. The results indicate that the available field angle for a given geometric spot size is, to a very close approximation, a function of the relative back focal distance only. Image curvatures, as computed by third-order theory and by the ray trace program, were found to be in very close agreement. Image curvature is plotted as a function of the ray height ratio for a wide range of secondary magnification.

Wyman, C. L.↗
NASA NTRS1975

Some statistical analysis techniques for the effect of systematic instrument errors on the results of measurements in a space experiment

Mathematical models of certain systematic telemetry signal errors arising during the passage of the signal through the recording and transmitting blocks of the physical instruments aboard the spacecraft are classified and constructed. Statistical analysis methods are used to determine the background function and relative sensitivity coefficients of the channels of a charged particle detector. Results are presented. A block diagram for a method taking into account the effect of distortions is given.

Kondakov, S. P.↗
NASA NTRS1974

U-Th-Pb and Rb-Sr systematics of Apollo 17 boulder 7 from the North Massif of the Taurus-Littrow valley

Portions of highland breccia boulder 7 collected during the Apollo 17 mission were studied using U-Th-Pb and Rb-Sr systematics. A Rb-Sr internal isochron age of 3.89 plus or minus 0.08 b.y. with an initial Sr-87/Sr-86 of 0.69926 plus or minus 0.00008 was obtained for clast 1 (77135,57) (a troctolitic microbreccia). A troctolitic portion of microbreccia clast 77215,37 yielded a U-Pb internal isochron of 3.8 plus or minus 0.2 b.y. and an initial Pb-206/Pb-207 of 0.69. These internal isochron ages are interpreted as reflecting metamorphic events, probably related to impacts, which reset Rb-Sr and U-Pb mineral systems of older rocks.

Nunes, P. D.↗
NASA NTRS1976

Systematically disseminating technological information to potential users

Rapid technological information dissemination system related to the field of remote sensing is presented. The technology transfer staff systematically designed instructional materials and activities using the matrix as an organizer to meet the need of the students, scientists and users in a rapidly expanding technology.

Russell, J. D.↗
NASA NTRS1977

Microturbulence, systematic motions, and line formation in molecular clouds

Microturbulence and systematic motions are viewed as simplifying assumptions made to facilitate treatment of line formation in molecular clouds, and line intensities calculated in the two approximations are compared to estimate how uncertainties about the actual line-broadening mechanism affect the interpretation of molecular emission lines. For lines formed by two-level molecules in an isothermal homogeneous cloud, the alternative assumptions lead to peak and integrated line intensities which agree within the differences (up to a factor of 3) associated with the ignorance of cloud geometry. New multilevel calculations for CO in the same cloud model bear out the generality of this result. It follows that, within the geometrical uncertainties, the Sobolev (1960) approximation may be used confidently in the numerous applications for which this simple cloud model suffices.

White, R. E.↗
NASA NTRS1976

Rb-Sr ages and isotopic systematics of some Serenitatis mare basalts

Rb/Sr isotopic data and internal isochron ages are presented for some mare basalts from the Taurus-Littrow region. It is found that in age and in trace- and major-element chemistry as well as in Rb-Sr isotopic systematics, the Serenitatis mare basalts closely resemble the low-K Tranquility basalts, suggesting that over a wide region on the moon volcanism occurred at a discrete period 3.7-3.8 AE ago.

Murthy, V. R.↗
NASA NTRS1976

Thorium and uranium variations in Apollo 17 basalts, and K-U systematics

It is found that Apollo 11 low-K and in particular Apollo 17 mare basalts show a wide range of Th/U ratios unlike other rocks; such variations cannot be explained by near surface crystal fractionation. A two-stage fractional crystallization-partial melting model involving a clinopyroxene cumulate as the major phase can explain the variations in Th/U ratios. Due to the Sm-Nd systematics constraint, several source cumulates are invoked to explain the observed Th/U continuum.

Laul, J. C.↗
NASA NTRS1977

Random and systematic measurement errors in acoustic impedance as determined by the transmission line method

The effect of random and systematic errors associated with the measurement of normal incidence acoustic impedance in a zero-mean-flow environment was investigated by the transmission line method. The influence of random measurement errors in the reflection coefficients and pressure minima positions was investigated by computing fractional standard deviations of the normalized impedance. Both the standard techniques of random process theory and a simplified technique were used. Over a wavelength range of 68 to 10 cm random measurement errors in the reflection coefficients and pressure minima positions could be described adequately by normal probability distributions with standard deviations of 0.001 and 0.0098 cm, respectively. An error propagation technique based on the observed concentration of the probability density functions was found to give essentially the same results but with a computation time of about 1 percent of that required for the standard technique. The results suggest that careful experimental design reduces the effect of random measurement errors to insignificant levels for moderate ranges of test specimen impedance component magnitudes. Most of the observed random scatter can be attributed to lack of control by the mounting arrangement over mechanical boundary conditions of the test sample.

Parrott, T. L.↗
NASA NTRS1977

Procedures for dealing with certain types of noise and systematic errors common to many Hadamard transform optical systems

Sources of noise and error correcting procedures characteristic of Hadamard transform optical systems were investigated. Reduction of spectral noise due to noise spikes in the data, the effect of random errors, the relative performance of Fourier and Hadamard transform spectrometers operated under identical detector-noise-limited conditions, and systematic means for dealing with mask defects are among the topics discussed. The distortion in Hadamard transform optical instruments caused by moving Masks, incorrect mask alignment, missing measurements, and diffraction is analyzed and techniques for reducing or eliminating this distortion are described.

Harwit, M.↗
NASA NTRS1978

The execution of systematic measurements on plane cascades

The present state of development of the experimental technique regarding the flow through cascades and several points to be specially observed in the design of cascade wind tunnels were discussed. The equations required for the evaluation of the momentum measurements in two dimensional flow through cascades were developed. Regarding the effect of the jet contraction due to the boundary layer along the side walls a simple method for correction was also given in order to obtain two dimensional flow characteristics. Also given were the equations for the evaluation of the pressure distribution measurements. Another contribution was made regarding the presentation of the test results in the form of nondimensional quantities. The results of systematic measurements of cascades with symmetrical aerofoil were reported, and the above suggested method was applied for the evaluation of the measurements.

Scholz, N.↗