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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 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

C IV and Si IV in IUE spectra of normal B8-A0 stars: UV identified Be/Ae stars

Archival IUE high dispersion spectra of 42 B6-A2 stars within 200 pc were surveyed. Five of the program stars show significant C IV and Si IV absorption. All of the stars with detected C IV have v sin i less than or = 190 km/sec. Sharp absorption cores are present in Si II lambda 1533 in 3 of the objects, indicating that these are previously unrecognized shell stars. Three of the stars have variable or asymmetric C IV profiles which are consistent with the C IV and Si IV being produced in stellar winds. One star has C IV in the form of a shortward-shifted discrete absorption component, similar to those observed in Be stars. The data are compared with similar data for Be and B shell stars.

Chiu, Weihsueh A.↗
NASA NTRS1988

Progress of research to identify rotating thunderstorms using satellite imagery

The possibility of detecting potentially tornadic thunderstorm cells from geosynchronous satelite imagery is determined. During the life of the contract, we examined eight tornado outbreak cases which had a total of 124 individual thunderstorm cells, 37 of which were tornadic.These 37 cells produced a total of 119 tornadoes. The outflow characteristics of all the cells were measured. Through the use of a 2-D flow field model, we were able to simulate the downstream developmemt of an anvil cloud plume which was emitted by the storm updraft at or near the tropopause. We used two parameters to characterize the anvil plume behavior: its speed of downstream propagation (U max) and the clockwise deviation of the centerline of the anvil plume from the storm relative ambient wind at the anvil plume outflow level (MDA). U max was the maximum U-component of the anvil wind parameter required to successfully maintain an envelope of translating particles at the tip of the expanding anvil cloud. MDA was the measured deviation angle acquired from McIDAS, between the storm relative ambient wind direction and the storm relative anvil plume outflow direction; tha latter being manipulated by controlling a tangential wind component to force the envelope of particles to maintain their position of surrounding the expanding outflow cloud.

Anderson, Charles E.↗
NASA NTRS1990

Identifying Bearing Balls With Radioisotopes

Proposed scheme for identification of members of manufactured lot of bearing balls based on detection of characteristic isotopes. All balls in lot irradiated to produce easily recognized radioactive isotopes in known concentrations and/or known ratios of concentrations and known rates of decay on their surfaces. Scheme conceived to track precise bearing balls through various stages of assembly, disassembly, and processing.

Butner, Myles F.↗
NASA NTRS1989

Study to identify future cryogen payload elements/users for space shuttle launch during period 1990 to 2000

This study provides a summary of future cryogenic space payload users, their currently projected needs and reported planning for space operations over the next decade. At present, few users with payloads consisting of reactive cryogens, or any cryogen in significant quantities, are contemplating the use of the Space Shuttle. Some members of the cryogenic payload community indicated an interest in flying their future planned payloads on the orbiter, versus an expendable launch vehicle (ELV), but are awaiting the outcome of a Rockwell study to define what orbiter mods and payloads requirements are needed to safely fly chemically reactive cryogen payloads, and the resultant cost, schedule, and operational impacts. Should NASA management decide in early 1990 to so modify orbiter(s), based on the Rockwell study and/or changes in national defense payloads launch requirements, then at least some cryo payload customers will reportedly plan on using the Shuttle orbiter vehicle in preference to an ELV. This study concludes that the most potential for possible future cryogenic space payloads for the Space Transportation System Orbiter fleet lies within the scientific research and defense communities.

Elim, Frank M.↗
NASA NTRS1988

Identifying motor and sensory myelinated axons in rabbit peripheral nerves by histochemical staining for carbonic anhydrase and cholinesterase activities

Carbonic anhydrase (CA) and cholinesterase (CE) histochemical staining of rabbit spinal nerve roots and dorsal root ganglia demonstrated that among the reactive myeliated axons, with minor exceptions, sensory axons were CA positive and CE negative whereas motor axons were CA negative and CE positive. The high specificity was achieved by adjusting reaction conditions to stain subpopulations of myelinated axons selectively while leaving 50 percent or so unstained. Fixation with glutaraldehyde appeared necessary for achieving selectivity. Following sciatic nerve transection, the reciprocal staining pattern persisted in damaged axons and their regenerating processes which formed neuromas within the proximal nerve stump. Within the neuromas, CA-stained sensory processes were elaborated earlier and in greater numbers than CE-stained regenerating motor processes. The present results indicate that histochemical axon typing can be exploited to reveal heterogeneous responses of motor and sensory axons to injury.

Riley, Danny A.↗
NASA NTRS1990

Identifying galaxies in the zone of avoidance

A set of IR color criteria was applied to sources in the IRAS Point Source Catalog at low Galactic latitudes in order to select candidate galaxies. A total of 371 of the selected sources within a Galactic latitude range (b) = 2-16 deg were searched for H I with the Arecibo 305 m radio telescope. Twenty-six percent (97) were detected, including 36 galaxies previously known only as IRAS sources. The H I spectra of the detected galaxies are presented together with their observed redshifts and velocity widths.

Lu, N. Y.↗
NASA NTRS1990

Application of a periodic lattice filter for identifying a flexible structure

Lattice filters have properties which make them attractive for the application to the identification of the parameters of flexible structures. Here, the problem of both order and parameter estimation is addressed, where the numerical difficulties of an embedded lattice filter are avoided by applying a periodic lattice filter. With this formulation, it is quite natural to estimate system order by applying Akaike's (1976) information criterion to each channel of the periodic lattice filter. Several examples including nonstationary cases are simulated to demonstrate these facts.

Lee, Young Jae↗
NASA NTRS1991

Overview of space propulsion systems for identifying nondestructive evaluation and health monitoring opportunities

The next generation of space propulsion systems will be designed to incorporate advanced health monitoring and nondestructive inspection capabilities. As a guide to help the nondestructive evaluation (NDE) community impact the development of these space propulsion systems, several questions should be addressed. An overview of background and current information on space propulsion systems at both the programmatic and technical levels is provided. A framework is given that will assist the NDE community in addressing key questions raised during the 2 to 5 April 1990 meeting of the Joint Army-Navy-NASA-Air Force (JANNAF) Nondestructive Evaluation Subcommittee (NDES).

Generazio, Edward R.↗
NASA NTRS1990

The use of spatial coherence techniques for identifying noise transmission paths on the MDC-UHB demonstrator aircraft

Application of partial coherence techniques to determination of the transmission paths of sound into an airplane cabin interior has been studied. Accurate quantitative information on the dominant paths of acoustic energy transmission can be obtained with this technique as well as the relative contributions from airborne and structure-borne paths. This information is useful in making design changes in the fuselage to reduce the interior cabin noise. The techniques are successfully applied to noise and vibration data collected during flight tests of the McDonnel Douglas Ultra-High Bypass Demonstrator aircraft, and these results are compared with other data measured during the flight program.

Tran, Boi N.↗
NASA NTRS1991

An inhomogeneous reference catalogue of identified intervening heavy element systems in spectra of QSOs

Identifications of heavy element line systems, observed in spectra of quasi-stellar objects between 1965 and 1989 inclusive, are collected and tabulated with references. Each system is assigned a quality grade based on the apparent reliability of the data. The highest quality systems are used to characterize the absorbers as a sample. A decrease in C IV line strength with redshift (z), and the corresponding decrease in line density per unit z with z are confirmed. The weakest C IV systems, at high z, are accompanied by relatively stronger Si IV lines, compared to the relative line strengths at low z. The space density of systems with strong lines of first ions is nearly independent of z below z = 3, though it drops at z greater than 3. Preliminary tests for quasar lensing by intervening systems and for clustering of absorbers on large scales are presented.

York, Donald G.↗
NASA NTRS1991

Pre-terrestrial oxidation products in carbonaceous meteorites identified by Mossbauer spectroscopy

The occurrence of ferric bearing assemblages, comprising phyllosilicates, oxide hydroxides and magnetite, in carbonaceous chondrites (CC) indicates that these meteorites underwent pre-terrestrial, sub-aqueous oxidation reactions. Reported here are results of a Mossbauer spectral study of a suite of CC demonstrating that a variety of ferrous and ferric bearing phases may be distinguished in different classes of this meteorite type.

Burns, Roger G.↗
NASA NTRS1991

Identifying tacit strategies in aircraft maneuvers

Two machine-learning methods are presently used to characterize the avoidance strategies used by skilled pilots in simulated aircraft encounters, and a general framework for the characterization of the strategic components of skilled behavior via qualitative representation of situations and responses is presented. Descriptions of pilot maneuvers that were 'conceptually equivalent' were ascertained by a concept-learning algorithm in conjunction with a classifier system that employed a generic algorithm; satisficing and 'buggy' strategies were thereby revealed.

Lewis, Charles M.↗
NASA NTRS1992

Meteor fireball sounds identified

Sounds heard simultaneously with the flight of large meteor fireballs are electrical in origin. Confirmation that Extra/Very Low Frequency (ELF/VLF) electromagnetic radiation is produced by the fireball was obtained by Japanese researchers. Although the generation mechanism is not fully understood, studies of the Meteorite Observation and Recovery Project (MORP) and other fireball data indicate that interaction with the atmosphere is definitely responsible and the cut-off magnitude of -9 found for sustained electrophonic sounds is supported by theory. Brief bursts of ELF/VLF radiation may accompany flares or explosions of smaller fireballs, producing transient sounds near favorably placed observers. Laboratory studies show that mundane physical objects can respond to electrical excitation and produce audible sounds. Reports of electrophonic sounds should no longer be discarded. A catalog of over 300 reports relating to electrophonic phenomena associated with meteor fireballs, aurorae, and lightning was assembled. Many other reports have been cataloged in Russian. These may assist the full solution of the similar long-standing and contentious mystery of audible auroral displays.

Keay, Colin↗
NASA NTRS1993

Model atmospheres - Tool for identifying interstellar features

Model atmosphere parameters are derived for 14 early A stars with rotation velocities, from optical spectra, in excess of 80 km/s. The models are compared with IUE observations of the stars in regions where interstellar lines are expected. In general, with the assumption of solar abundances, excellent fits are obtained in regions longward of 2580 A, and accurate interstellar equivalent widths can be derived using models to establish the continuum. The fits are poorer at shorter wavelengths, particularly at 2026-2062 A, where the stellar model parameters seem inadequate. Features indicating mass flows are evident in stars with known infrared excesses. In gamma TrA, variability in the Mg II lines is seen over the 5-year interval of these data, and also over timescales as short as 26 days. The present technique should be useful in systematic studies of episodic mass flows in A stars and for stellar abundance studies, as well as interstellar features.

Frisch, P. C.↗
NASA NTRS1991

Identifying the unmodified structural characteristics using multiple modifications

This paper describes a procedure for estimating the free-free modal characteristics of a system by testing multiple constrained states. The procedure eliminates the influences of the constraints on the modal parameters and provides important information at the connection points. For very stiff or very flexible test articles, it is difficult to support the test article and to measure uncompromised modal parameters. The method described in this paper measures the forces and/or responses at constraint-connection points and uses a direct parameter estimation algorithm to calculate the system's free-free characteristics. These free-free characteristics retain the local information at the connection or boundary points, thereby including the important local high frequency residual effects in the modal model.

Barney, Patrick↗
NASA NTRS1994

An evaluation of criteria that may be used to identify species surviving a mass extinction

One of the most difficult obstacles to establishing a causal connection between mass extinctions and large body impacts is the existence of what appear to be many more KT survivor species than previously suspected. Though interpretations of 'Cretaceous' faunal elements in lowermost Danian sediments differ, this enigmatic fauna has not been recovered from every biozone-complete boundary section, including the El Kef stratotype. In terms of their potential for providing constraints on scenarios seeking to account for the KT extinction event, the significance of such observations cannot be overstated. Owing to the consistency with which these observations have been made over the last several years, the possibility of widespread trans-KT biotic survivorship can no longer be dismissed. Rather, the survivorship hypothesis must be tested alongside its alternative (the reworking hypothesis) to determine which explains the available data in the most complete yet parsimonious manner. Moreover, valid tests for survivorship cannot be based on negative evidence or on the assumption that only a small cohort of species could have survived the KT boundary event. Several authors have recently proposed various criteria that might be used to test alternative interpretations for this aspect lowermost Danian biotic record.

Macleod, N.↗
NASA NTRS1994

A test apparatus and facility to identify the rotordynamic coefficients of high-speed hydrostatic bearings

A facility and apparatus are described which determine stiffness, damping, and added-mass rotordynamic coefficients plus steady-state operating characteristics of high speed hydrostatic journal bearings. The apparatus has a current top speed of 29,800 rpm with a bearing diameter of 7.62 cm (3 in.). Purified warm water, 55 C (130 F), is used as a test fluid to achieve elevated Reynolds numbers during operation. The test-fluid pump yields a bearing maximum inlet pressure of 6.9 Mpa (1000 psi). Static load on the bearing is independently controlled and measured. Orthogonally mounted external shakers are used to excite the test stator in the direction of, and perpendicular to, the static load. The apparatus can independently calculate all rotordynamic coefficients at a given operating condition.

Childs, Dara↗