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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 649 records · Page 36

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NASA NTRS1980

Fundamental heat transfer research for gas turbine engines

Thirty-seven experts from industry and the universities joined 24 NASA Lewis staff members in an exchange of ideas on trends in aeropropulsion research and technology, basic analyses, computational analyses, basic experiments, near-engine environment experiments, fundamental fluid mechanics and heat transfer, and hot technology as related to gas turbine engines. The workshop proceedings described include pre-workshop input from participants, presentations of current activity by the Lewis staff, reports of the four working groups, and a workshop summary.

Metzger, D. E.↗

NASA NTRS1981

Fundamental limitations caused by RF propagation

Propagation phenomena affect the design of radio frequency (RF) transmission systems. Propagation phenomena limit the suitability of portions of the frequency band for some applications, limit the reliability of RF transmission systems, and provide a means of coupling unwanted signals from one system to another with the potential of producing interference. The possibility of interference is the fundamental limitation to the unrestricted use of the frequency band. Phenomena affecting suitability, reliability, and the potential for interference are considered for frequencies in the 1- to 300-GHz range.

Crane, R. K.↗

NASA NTRS1979

Mechanics of fracture - Fundamentals and some recent developments

An overview is presented of the fundamental aspects of and recent developments in fracture mechanics. Reference is made to linear elastic fracture mechanics including the state of stresses and displacements in the vicinity of cracks, effects of crack geometry and orientation on stress intensity factors, energy balance of Griffith, Irwin's stress intensity concept, and linear elastic fracture mechanics testing for fracture toughness. Other aspects of this paper include the non-linear behavior of materials and their influence on fracture mechanics parameters, consideration of viscoelasticity and plasticity, non-linear fracture toughness parameters as C.O.D., R-curve and J-integral, and a non-linear energy method, proposed by Liebowitz. Finite element methods applied to fracture mechanics problems are indicated. Also, consideration has been given to slow crack growth, dynamic effects on K(IC), Sih's criterion for fracture, Lee and Liebowitz's criterion relating crack growth with plastic energy, and applications of fracture mechanics to aircraft design. Suggestions are offered for future research efforts to be undertaken in fracture mechanics.

Liebowitz, H.↗

NASA NTRS1981

Spectral transmission measurements in the nu sub 6 fundamental of /C-12/H3D at 8.65 microns

Spectral transmission measurements were performed at 300 K in the 8.65-micron fundamental band of monodeuterated methane, a trace constituent in the atmosphere of Jupiter. A theoretical curve is obtained from line-by-line computation of the spectral transmission utilizing a triangular slit function with full width at half-maximum. The agreement between theoretical and experimental spectral transmission curves suggests that deuteration does not affect the collision-broadened half-widths significantly in the two extreme cases of broadening being considered.

Varanasi, P.↗

NASA NTRS1981

Antennas in matter: Fundamentals, theory, and applications

The volume provides an introduction to antennas and probes embedded within or near material bodies such as the earth, the ocean, or a living organism. After a fundamental analysis of insulated and bare antennas, an advanced treatment of antennas in various media is presented, including a detailed study of the electromagnetic equations in homogeneous isotropic media, the complete theory of the bare dipole in a general medium, and a rigorous analysis of the insulated antenna as well as bare and insulated loop antennas. Finally, experimental models and measuring techniques related to antennas and probes in a general dissipative or dielectric medium are examined.

King, R. W. P.↗

NASA NTRS1981

Prediction of absolute infrared intensities for the fundamental vibrations of H2O2

Absolute infrared intensities are predicted for the vibrational bands of gas-phase H2O2 by the use of a hydrogen atomic polar tensor transferred from the hydroxyl hydrogen atom of CH3OH. These predicted intensities are compared with intensities predicted by the use of a hydrogen atomic polar tensor transferred from H2O. The predicted relative intensities agree well with published spectra of gas-phase H2O2, and the predicted absolute intensities are expected to be accurate to within at least a factor of two. Among the vibrational degrees of freedom, the antisymmetric O-H bending mode nu(6) is found to be the strongest with a calculated intensity of 60.5 km/mole. The torsional band, a consequence of hindered rotation, is found to be the most intense fundamental with a predicted intensity of 120 km/mole. These results are compared with the recent absolute intensity determinations for the nu(6) band.

Rogers, J. D.↗

NASA NTRS1981

Fundamental studies in geodynamics

Research in fundamental studies in geodynamics continued in a number of fields including seismic observations and analysis, synthesis of geochemical data, theoretical investigation of geoid anomalies, extensive numerical experiments in a number of geodynamical contexts, and a new field seismic volcanology. Summaries of work in progress or completed during this report period are given. Abstracts of publications submitted from work in progress during this report period are attached as an appendix.

Anderson, D. L.↗

NASA NTRS1982

Introduction to some fundamental concepts of general relativity and to their required use in some modern timekeeping systems

Einstein's theory of gravity as curved space-time is presented. Emphasis is on the physical concepts, using only elementary mathematics. For the slow motions and weak gravitational fields experienced on Earth, the main curvature is that of time, not space. Experiments demonstrating this property are reviewed. The fundamental effects of motion and gravitational potential on clocks in many practical situations are discussed.

Alley, C. O.↗

NASA NTRS1982

Documentation for the machine-readable version of the first Santiago-Pulkovo Fundamental Stars Catalogue (SPF1 catalogue)

The machine-readable version of the first Santiago-Pulkovo Fundamental Stars catalog is described. It is intended to enable users to read and process the computerized catalog without the problems and guesswork often associated with such a task. The source reference should be consulted for additional details regarding the measurements, instrument characteristics, reductions, construction of the quasi-absolute system of right ascension, and star positions in the catalog.

Warren, W. H., Jr.↗

NASA NTRS1981

National Aeronautics and Space Administration fundamental research program. Information utilization and evaluation

In the second half of the 1980's NASA can expect to face difficult choices among alternative fundamental and applied research, and development projects that could potentially lead to improvements in the information systems used to manage renewable resources. The working group on information utilization and evaluation believes that effective choices cannot be made without a better understanding of the current and prospective problems and opportunities involved in the application of remote sensing to improve renewable research information systems. A renewable resources information system is defined in a broad context to include a flow of data/information from: acquisition through processing, storage, integration with other data, analysis, graphic presentation, decision making, and assessment of the affects of those decisions.

Estes, J. E.↗

NASA NTRS1981

Microwave remote sensing: Active and passive. Volume 1 - Microwave remote sensing fundamentals and radiometry

The three components of microwave remote sensing (sensor-scene interaction, sensor design, and measurement techniques), and the applications to geoscience are examined. The history of active and passive microwave sensing is reviewed, along with fundamental principles of electromagnetic wave propagation, antennas, and microwave interaction with atmospheric constituents. Radiometric concepts are reviewed, particularly for measurement problems for atmospheric and terrestrial sources of natural radiation. Particular attention is given to the emission by atmospheric gases, clouds, and rain as described by the radiative transfer function. Finally, the operation and performance characteristics of radiometer receivers are discussed, particularly for measurement precision, calibration techniques, and imaging considerations.

Ulaby, F. T.↗

NASA NTRS1982

Positions of type II fundamental and harmonic sources in the 30-100 MHZ range

An excellent example of a type III-V burst followed by a type II burst with fundamental and harmonic bands was observed on June 18, 1979 at the Clark Lake Radio Observatory. The observations are described in detail and their implications are discussed with regard to the problem of directionality with respect to the magnetic field lines of the collisionless MHD shock wave generated at the start of the flash phase. It is found that the positions of type III and type II (F) bursts at a number of frequencies are essentially the same, which implies that the shock responsible for the type II radiation follows the path of the type III exciter, that is, the shock propagates along the open field lines.

Sawant, H. S.↗

NASA NTRS1982

Fundamentals of ultrasonic NDE for microstructure/material property interrelations

Some fundamental aspects of ultrasonic nondestructive evaluation for material properties and microstructure assessment are given. Ultrasonic wave interaction concepts, some recent findings, and practical ramifications are illustrated. The concepts are discussed in nonmathematical, narrative form. Additional information can be found in the references cited herein.

A. Vary↗

NASA NTRS1981

Fundamental procedures of geographic information analysis

Analytical procedures common to most computer-oriented geographic information systems are composed of fundamental map processing operations. A conceptual framework for such procedures is developed and basic operations common to a broad range of applications are described. Among the major classes of primitive operations identified are those associated with: reclassifying map categories as a function of the initial classification, the shape, the position, or the size of the spatial configuration associated with each category; overlaying maps on a point-by-point, a category-wide, or a map-wide basis; measuring distance; establishing visual or optimal path connectivity; and characterizing cartographic neighborhoods based on the thematic or spatial attributes of the data values within each neighborhood. By organizing such operations in a coherent manner, the basis for a generalized cartographic modeling structure can be developed which accommodates a variety of needs in a common, flexible and intuitive manner. The use of each is limited only by the general thematic and spatial nature of the data to which it is applied.

Berry, J. K.↗

NASA NTRS1983

Fundamental research data base

A fundamental research data base was created on a single 9-track 1600 BPI tape containing ground truth, image, and Badhwar profile feature data for 17 North Dakota, South Dakota, and Minnesota agricultural sites. Each site is 5x6 nm in area. Image data has been provided for a minimum of four acquisition dates for each site. All four images have been registered to one another. A list of the order of the files on tape and the dates of acquisition is provided.

Source record↗

NASA NTRS1983

Fundamental research data base

A fundamental research data base containing ground truth, image, and Badhwar profile feature data for 17 North Dakota, South Dakota, and Minnesota agricultural sites is described. Image data was provided for a minimum of four acquisition dates for each site and all four images were registered to one another.

Source record↗

NASA NTRS1983

The fundamental structure function of oscillator noise models

Continuous-time models of oscillator phase noise x(t) usually have stationary nth differences, for some n. The covariance structure of such a model can be characterized in the time domain by the structure function: D sub n (t;gamma sub 1, gamma sub 2) = E delta (n) sub gamma sub 1 x(s+t) delta(n) sub gamma sub 2 x (s). Although formulas for the special case D sub 2 (0;gamma,gamma) (the Allan variance times 2 gamma(2)) exist for power-law spectral models, certain estimation problems require a more complete knowledge of (0). Exhibited is a much simpler function of one time variable, D(t), from which (0) can easily be obtained from the spectral density by uncomplicated integrations. Believing that D(t) is the simplest function of time that holds the same information as (0), D(t) is called the fundamental structure function. D(t) is computed for several power-law spectral models. Two examples are D(t) = K/t/(3) for random walk FM, D(t) = Kt(2) 1n/t/ for flicker FM. Then, to demonstrate its use, a BASIC program is given that computes means and variances of two Allan variance estimators, one of which incorporates a method of frequency drift estimation and removal.

Greenhall, C. A.↗

NASA NTRS1983

Fundamental linewidth in solitary, ultranarrow output PbS(1-x)Se(x) diode lasers

The fundamental, quantum phase noise limited Lorentzian linewidth was directly measured from the beat-note spectra generated by heterodyning PbS(1-x)Se(x) diode lasers with a stable CO gas laser. The experimental results were matched by calculated theoretical line profiles. Linewidths as narrow as 22 kHz full width at half-maximum power were observed.

Freed, C.↗