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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The dynamics of superclusters - Initial determination of the mass density of the universe at large scales

The radial velocities of cluster members of two rich, large superclusters have been measured in order to probe the supercluster mass densities, and simple evolutionary models have been computed to place limits upon the mass density within each supercluster. These superclusters represent true physical associations of size of about 100 Mpc seen presently at an early stage of evolution. One supercluster is weakly bound, the other probably barely bound, but possibly marginally unbound. Gravity has noticeably slowed the Hubble expansion of both superclusters. Galaxy surface-density counts and the density enhancement of Abell clusters within each supercluster were used to derive the ratio of mass densities of the superclusters to the mean field mass density. The results strongly exclude a closed universe.

Ford, H. C.↗
NASA NTRS1981

Evaluation and universal curves of the photon loss probability

In the transfer of radiation in a plasma, an important parameter (which measures the coupling between the radiation field and the electron gas) is the photon loss probability per scattering epsilon, defined as the ratio of collisional de-excitation to total de-excitation. The evaluation of epsilon requires normally knowledge of specific collisional excitation rates and radiative transition rate coefficients. In the considered investigation a general formula for epsilon is obtained which depends only on electron density, temperature, and line wavelength. Use is made of a simple Bethe-Coulomb expression recently derived by Kastner (1980) for the collisional excitation rate coefficient. Epsilon is obtained as a function of the three variables, and universal curves of it can be constructed with one of the variables as parameter. As an example of the application of the considered procedure, the variation of epsilon with height h in the solar atmosphere is shown in a graph for several solar lines.

Kastner, S. O.↗
NASA NTRS1981

NASA's University Program: Active projects, fiscal year 1981

Active university R and D activities funded by NASA which contribute to mission needs are documented. Technical rather than fiscal information is emphasized. A classification of government sponsored research is included. A cross index providing access to the project description is also included.

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NASA NTRS1980

A study of universal modulation techniques applied to satellite data collection

A universal modulation and frequency control system for use with data collection platform (DCP) transmitters is examined. The final design discussed can, under software/firmwave control, generate all of the specific digital data modulation formats currently used in the NASA satellite data collection service and can simultaneously synthesize the proper RF carrier frequencies employed. A novel technique for DCP time and frequency control is presented. The emissions of NBS radio station WWV/WWVH are received, detected, and finally decoded in microcomputer software to generate a highly accurate time base for the platform; with the assistance of external hardware, the microcomputer also directs the recalibration of all DCP oscillators to achieve very high frequency accuracies and low drift rates versus temperature, supply voltage, and time. The final programmable DCP design also employs direct microcomputer control of data reduction, formatting, transmitter switching, and system power management.

Source record↗
NASA NTRS1981

A meeting with the universe: Science discoveries from the space program

A general history of space exploration is presented. The solar system is discussed. The Sun-Earth relationship is considered, including magnetic fields, solar wind, the magnetosphere, and the Sun-weather relationship. The universe beyond the solar system is discussed. Topics include stellar and galactic evolution, quasars and intergalactic space. The effects of weightlessness and ionizing radiation on human beings are considered. The possibility of extraterrestrial life is discussed. Lunar and planetary exploration, solar-terrestrial physics, astrophysics, biomedical research and exobiology are reviewed. Numerons color illustrations are included.

French, B. M.↗
NASA NTRS1981

Matter-antimatter separation in the early universe by rotating black holes

Consideration of the effect of rotating black holes evaporating early in the universe shows that they would have produced oppositely directed neutrino and antineutrino currents, which push matter and antimatter apart. This separation mechanism is, however, too feeble to account for a present baryon-to-photon ratio of 10 to the -9th, and has no significant observational consequences.

Leahy, D. A.↗
NASA NTRS1982

Comparison of starting values for iterative solutions to a universal Kepler's equation

General starting values for the iterative numerical solution of a universal Kepler's equation for position in a conic orbit at a specified time are investigated. Three starting values based on recent refinements of previously obtained bounds on the solution are derived and tested numerically. Of these, a simple starting value based on a cubic approximation to Kepler's equation provides the most rapid convergence using both first and second order Newton algorithms. The performance of the starting values are compared with similar studies which used the restricted case of elliptical orbits with the initial epoch at periapse.

Bergam, M. J.↗
NASA NTRS1981

Software for universal noiseless coding

An overview is provided of the universal noiseless coding algorithms as well as their relationship to the now available FORTRAN implementations. It is suggested that readers considering investigating the utility of these algorithms for actual applications should consult both NASA's Computer Software Management and Information Center (COSMIC) and descriptions of coding techniques provided by Rice (1979). Examples of applying these techniques have also been given by Rice (1975, 1979, 1980). Attention is given to reversible preprocessing, general implementation instructions, naming conventions, and calling arguments. A general applicability of the considered algorithms to solving practical problems is obtained because most real data sources can be simply transformed into the required form by appropriate preprocessing.

Rice, R. F.↗
NASA NTRS1982

Finite-beta stabilization of the universal drift instability - Revisited

A numerical study has been made of the universal drift instability in finite beta plasmas, and a marginal stability curve has been plotted. Several limits have been considered to illustrate the various influences of finite beta. The mode is found to be stable for beta larger than or equal to 0.135; the most difficult waves to stabilize are those that have arbitrarily small wavenumbers. The stabilization mechanism is the ion Landau resonance which is enhanced by the coupling of electrostatic and transverse electromagneticc oscillations.

Huba, J. D.↗
NASA NTRS1982

Constraints on the density of baryons in the Universe

It is shown that it is possible to obtain a lower bound on the ratio of baryons to photons in the Universe, E, from Big Bang nucleosynthesis through the use of He-3 and deuterium, and that this limit is consistent with the Li-7 abundance. It is shown that this limit places very narrow bounds on the allowed value for E, thus tightly constraining the neutrino limits to no more than four species. The derived constraints are that E must be between 1.5 x 10 to the -10 and 7 x 10 to the -9 with a best fit between 3 and 6 x 10 to the -10. With reference to dark matter, the derived baryon density for Big Bang nucleosynthesis corresponds very closely with the implied density of matter in binaries and small groups of galaxies, implying that nonbaryonic matter is not dominant by a large factor on scales as large as binaries and small groups of galaxies.

Schramm, D. N.↗
NASA NTRS1982

Universal approach to analysis of cavitation and liquid-impingement erosion data

Cavitation erosion experimental data was analyzed by using normalization and curve-fitting techniques. Data were taken from experiments on several materials tested in both a rotating disk device and a magnetostriction apparatus. Cumulative average volume loss rate and time data were normalized relative to the peak erosion rate and the time to peak erosion rate, respectively. From this process a universal approach was derived that can include data on specific materials from different test devices for liquid impingement and cavitation erosion studies.

Rao, P. V.↗
NASA NTRS1981

Low-cost digital image processing at the University of Oklahoma

Computer assisted instruction in remote sensing at the University of Oklahoma involves two separate approaches and is dependent upon initial preprocessing of a LANDSAT computer compatible tape using software developed for an IBM 370/158 computer. In-house generated preprocessing algorithms permits students or researchers to select a subset of a LANDSAT scene for subsequent analysis using either general purpose statistical packages or color graphic image processing software developed for Apple II microcomputers. Procedures for preprocessing the data and image analysis using either of the two approaches for low-cost LANDSAT data processing are described.

Harrington, J. A., Jr.↗
NASA NTRS1981

Remote sensing education at the University of British Columbia

The development, current status, and organization of the University of British Columbia's interdisciplinary graduate program in remote sensing are described. Specialized programs are tailored to meet student's needs and interest and can range from the theoretical development of technology (sensor development, modelling, and computer analysis) to specialized application of remote sensing in resource analysis such as the determination of vegetation damage, land classification, and land use. The courses and faculty members are listed.

Murtha, P. A.↗
NASA NTRS1981

Low-cost digital image processing on a university mainframe computer

The advantages and limitations of using university mainframe computers in digital image processing instruction are listed. Aspects to be considered when designing software for this purpose include not only two general audience, but also the capabilities of the system regarding the size of the image/subimage, preprocessing and enhancement functions, geometric correction and registration techniques; classification strategy, classification algorithm, multitemporal analysis, and ancilliary data and geographic information systems. The user/software/hardware interaction as well as acquisition and operating costs must also be considered.

Williams, T. H. L.↗
NASA NTRS1981

Instructional image processing on a university mainframe: The Kansas system

An interactive digital image processing program package was developed that runs on the University of Kansas central computer, a Honeywell Level 66 multi-processor system. The module form of the package allows easy and rapid upgrades and extensions of the system and is used in remote sensing courses in the Department of Geography, in regional five-day short courses for academics and professionals, and also in remote sensing projects and research. The package comprises three self-contained modules of processing functions: Subimage extraction and rectification; image enhancement, preprocessing and data reduction; and classification. Its use in a typical course setting is described. Availability and costs are considered.

Williams, T. H. L.↗