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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Several recent findings concerning the dynamics of the earth's magnetotail

Several recent results concerning the nature of earth's magnetotail are briefly reviewed. These observational findings include: (1) the three-dimensional character of the plasma sheet via a comprehensive survey of proton bulk flows, (2) a region of earthward-flowing plasmas at the interfaces of the plasma sheet and magnetotail lobes during magnetic substorm recovery, and (3) the signature of electrostatic acceleration for protons within the jetting plasmas from magnetotail fireballs.

Frank, L. A.↗
NASA NTRS1980

Errors in magnetic direction finding due to nonvertical lightning channels

A theory showing that errors in lightning magnetic direction finding due to nonvertical source orientations are minimized by detecting the field from the lowest possible channel section is presented. For 99 cloud-to-ground lightning channels photographed in Arizona, 45 exhibited a bottom few hundred meters within about 8 deg of the vertical, the standard deviation of the distribution of lower-channel tilt angles being about 18 deg. These experimental results, coupled with theory, suggest that if a wideband gated direction finder is used, polarization errors due to nonvertical sources can be kept less than 1 deg for lightning beyond 10 km.

Uman, M. A.↗
NASA NTRS1985

Research on the effect of noise at different times of day: Models, methods and findings

Social surveys of residents' responses to noise at different times of day are reviewed. Some of the discrepancies in published reports about the importance of noise at different times of day are reduced when the research findings are classified according to the type of time of day reaction model, the type of time of day weight calculated and the method which is used to estimate the weight. When the estimates of nighttime weights from 12 studies are normalized, it is found that they still disagree, but do not support stronger nighttime weights than those used in existing noise indices. Challenges to common assumptions in nighttime response models are evaluated. Two of these challenges receive enough support to warrant further investigation: the impact of changes in numbers of noise events may be less at night than in the day and nighttime annoyance may be affected by noise levels in other periods. All existing social survey results in which averages of nighttime responses were plotted by nighttime noise levels are reproduced.

Fields, J. M.↗
NASA NTRS1984

Documentation for the machine-readable version of A Finding List for the Multiplet Tables of NSRDS-NBS 3, Sections 1-10 (Adelman, Adelman, Fischel and Warren 1984)

The machine-readable finding list, as it is currently being distributed from the Astronomical Data Center, is described. This version of the list supersedes an earlier one (1977) containing only Sections 1 through 7 of the NSRDS-NBS 3 multiplet tables publications. Additional sections are to be incorporated into this list as they are published.

Warren, W. H., Jr.↗
NASA NTRS1985

A finding list for the multiplet tables of NSRDS-NBS3, Sections 1-10

The preparation of a magnetic-tape finding list for the first 10 sections of the U.S. National Bureau of Standards Reference Data System (NSRDS-NBS3) tables of optical multiplets of astrophysical interest (Moore, 1965-1983) is reported. The format of the list is described, and a sample page is provided.

Adelman, C. J.↗
NASA NTRS1986

Range finding using frequency-modulated laser diode

A coherent-optical time-of-flight range-finding technique is proposed which uses a simple inexpensive device. Target range is determined by modulating a laser diode's optical frequency and measuring the change in the phase of the light reflected back into the laser. Target velocity as well as range can be measured using this approach. The device is described, and experimental evidence is presented to show the feasibility of measuring distance with subcentimeter resolution over a 1.5-m range.

Beheim, G.↗
NASA NTRS1985

Intelligence/Electronic Warfare (IEW) direction-finding and fix estimation analysis report. Volume 2: Trailblazer

An analysis of the direction finding (DF) and fix estimation algorithms in TRAILBLAZER is presented. The TRAILBLAZER software analyzed is old and not currently used in the field. However, the algorithms analyzed are used in other current IEW systems. The underlying algorithm assumptions (including unmodeled errors) are examined along with their appropriateness for TRAILBLAZER. Coding and documentation problems are then discussed. A detailed error budget is presented.

Gardner, Robert↗
NASA NTRS1988

Cretaceous-Tertiary findings, paradigms and problems

The asteroid hypothesis has stimulated numerous studies of the paleontological record at Cretaceous/Tertiary time as well as of geological indicators of environmental crisis preserved in the rock record. Both extinctions and geological anomalies often occur at times that do not appear to be synchronous or instantaneous. The record includes paleontological indicators of dinosaurs, terrestrial flora, marine planktonic organisms, and shallow water marine macrofauna and geological phenomena include occurrences of iridium and other platinum metals, trace elements, clay mineralogy, shocked minerals, soot, microspherules, and isotopes of osmium, strontium and carbon. These findings are reviewed in the context of the alternate hypotheses of an exogenic cause, involving either a single asteroid impact or multiple commentary impacts, and an endogenic cause, involving intense global volcanism and major sea level regression.

Officer, C. B.↗
NASA NTRS1990

Processor Would Find Best Paths On Map

Proposed very-large-scale integrated (VLSI) circuit image-data processor finds path of least cost from specified origin to any destination on map. Cost of traversal assigned to each picture element of map. Path of least cost from originating picture element to every other picture element computed as path that preserves as much as possible of signal transmitted by originating picture element. Dedicated microprocessor at each picture element stores cost of traversal and performs its share of computations of paths of least cost. Least-cost-path problem occurs in research, military maneuvers, and in planning routes of vehicles.

Eberhardt, Silvio P.↗
NASA NTRS1989

Finding idle machines in a workstation-based distributed system

The authors describe the design and performance of scheduling facilities for finding idle hosts in a workstation-based distributed system. They focus on the tradeoffs between centralized and decentralized architectures with respect to scalability, fault tolerance, and simplicity of design, as well as several implementation issues of interest when multicast communication is used. They conclude that the principal tradeoff between the two approaches is that a centralized architecture can be scaled to a significantly greater degree and can more easily monitor global system statistics, whereas a decentralized architecture is simpler to implement.

Theimer, Marvin M.↗
NASA NTRS1990

Basic formulas find oscillator power gain

Traditional circuit analysis defines the power gain of an oscillator to be finite, since there is an output without an input. By defining power gain as the ratio of output power to input power, however, finite power gain can be characterized. Several simple circuit equations which can be used to find power gain in an oscillator circuit are presented and discussed.

Kleinberg, Leonard L.↗
NASA NTRS1990

Finding fixed satellite service orbital allotments with a k-permutation algorithm

A satellite system synthesis problem, the satellite location problem (SLP), is addressed. In SLP, orbital locations (longitudes) are allotted to geostationary satellites in the fixed satellite service. A linear mixed-integer programming model is presented that views SLP as a combination of two problems: the problem of ordering the satellites and the problem of locating the satellites given some ordering. A special-purpose heuristic procedure, a k-permutation algorithm, has been developed to find solutions to SLPs. Solutions to small sample problems are presented and analyzed on the basis of calculated interferences.

Reilly, Charles H.↗
NASA NTRS1991

Preliminary findings of the LDEF materials special investigation group

Presented here are the charter and scope of the Long Duration Exposure Facility's (LDEF) Space Environmental Effects on Materials Special Investigation Group (MSIG) activities, and an overview of of preliminary observations. These observations of low-Earth orbit environmental effects on material were made in space during during LDEF retrieval and during LDEF tray deintegration. Also included are initial findings of laboratory analysis of LDEF materials.

Stein, Bland A.↗
NASA NTRS1991

Advanced Photovoltaic Experiment, S0014: Preliminary Flight Results and Post-Flight Findings

The Advanced Photovoltaic Experiment (APEX) is an LDEF experiment designed to provide reference solar cell standards for laboratory measurements as well as to investigate the solar spectrum and the effects of long term exposure of solar cells to the LEO environment. Silicon and gallium arsenide solar cells were flown with the appropriate instrumentation to periodically measure cell performance and temperature. The experimental objectives, the design employed to realize these objectives and the solar cells and instrumentation selected for the flight are presented. A discussion of the flight data returned are included. Preliminary results from the post flight analysis of the absolute cavity radiometer, the digital solar angle sensor, and the Barr Associates narrow bandpass optical filters are also presented. The initial findings of work to determine the chemical nature of contamination layers on APEX are also presented.

Brinker, David J.↗
NASA NTRS1991

Extension of and improvements to the ERDC low frequency magnetic direction finding system

In 1985, a three station direction finding lightning location system was established in the United Kingdom. A description of its evolution from an experimental system to a five station commercial system providing both on-line and historical location information is presented. A method of error reduction which enables simultaneous optimization of strike location and calculation of aerial twist error is described, together with results of the analysis of four station data from 1989. It is demonstrated that one station with a twist error can produce an apparent bearing dependent error in a station without errors. Application of the bearing corrections has significantly improved the accuracy of the system. Average location errors of better that 1 km can be achieved at a distance of 200 km from the stations.

Lees, M. I.↗
NASA NTRS1991

Network of dedicated processors for finding lowest-cost map path

A method and associated apparatus are disclosed for finding the lowest cost path of several variable paths. The paths are comprised of a plurality of linked cost-incurring areas existing between an origin point and a destination point. The method comprises the steps of connecting a purality of nodes together in the manner of the cost-incurring areas; programming each node to have a cost associated therewith corresponding to one of the cost-incurring areas; injecting a signal into one of the nodes representing the origin point; propagating the signal through the plurality of nodes from inputs to outputs; reducing the signal in magnitude at each node as a function of the respective cost of the node; and, starting at one of the nodes representing the destination point and following a path having the least reduction in magnitude of the signal from node to node back to one of the nodes representing the origin point whereby the lowest cost path from the origin point to the destination point is found.

Eberhardt, Silvio P.↗
NASA NTRS1992

Preliminary findings of the LDEF Materials Special Investigation Group

The retrieval of NASA's LDEF from low Earth orbit provided an opportunity for the study of long duration space environmental effects on materials. The five year, nine month flight of the LDEF greatly enhanced the potential value of most LDEF materials. NASA recognized this potential by forming the LDEF Space Environmental Effects on Materials Special Investigation Group (MSIG). Its goal is to explore the expanded materials analysis opportunities available in the LDEF structure and on experiment trays. The charter and scope of MSIG activities is presented, followed by an overview of the preliminary MSIG observations. These observations of low Earth orbit environmental effects on materials were made in-space during LDEF retrieval and during LDEF tray disintegration. Also presented are initial findings of lab analyses of LDEF materials. Included are effects of individual environmental parameters: atomic oxygen, ultraviolet radiation, meteoroid and debris impacts, thermal cycling, vacuum, and contamination, plus combined effects of these parameters. Materials considered include anodized aluminum, polymer matrix composites, polymer films, silvered Teflon thermal blankets, and a white thermal control paint.

Stein, Bland A.↗