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  • Other Sources  (15)
  • 1990-1994  (14)
  • 1970-1974  (1)
  • 1991  (14)
  • 1971  (1)
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  • 1990-1994  (14)
  • 1970-1974  (1)
Year
  • 1
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    Optical link demonstration with a lightweight transceiver breadboard (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A compact optical communications transceiver breadboard was constructed. In order to keep the mass of the breadboard as low as possible the design was made very simple. The entire package weighs less than 5 kg. The optical module uses a 40 mW diode laser and a two-axis voice coil actuator for beam steering. The breadboard is capable of locking onto a laser beacon within its field of view and transmitting the diode laser beam back toward the beacon. Design of the breaboard, details of each component in the breadboard, and current experiments with the package are described.
    Keywords: OPTICS
    Type: In: Free-space laser communication technologies III; Proceedings of the Meeting, Los Angeles, CA, Jan. 21, 22, 1991 (A93-18923 05-74); p. 476-483.
    Format: text
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  • 2
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    MPD work at MIT (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: MPD work at MIT is presented in the form of the view-graphs. The following subject areas are covered: the MIT program, its goals, achievements, and roadblocks; quasi one-dimensional modeling; two-dimensional modeling - transport effects and Hall effect; microscopic instabilities in MPD flows and modified two stream instability; electrothermal stability theory; separation of onset and anode depletion; exit plane spectroscopic measurements; phenomena of onset as performance limiter; explanations of onset; geometry effects on onset; onset at full ionization and its consequences; relationship to anode depletion; summary on self-field MPD; applied field MPD - the logical growth path; the case for AF; the challenges of AF MPD; and recommendations.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Lewis Research Center, Magnetoplasmadynamic Thruster Workshop; 17 p
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    NASA TECHNICAL REPORTS
  • 3
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    Static and Dynamic Pressure Distributions in a Short Labyrinth Seal (1991)
    In:  CASI
    Details
    Publication Date: 2014-09-24
    Description: As part of a study into turbine blade tip destabilizing forces, a seals test rig was built in which spin rate, circular whirl rate, direction and amplitude of inlet swirl angle, and eccentricity can all be controlled over wide ranges, and measurements can be made at gap Reynolds numbers up to about 2 x 10(exp 4). This facility is described and preliminary data is presented for a one cavity labyrinth seal with a flat, stator mounted land. The impact of different flow coefficients for the first and second knives on the rotordynamic coefficients was found. While this effect is dominant for the direct forces, it should also be incorporated into calculations of cross forces where it has an impact under many conditions.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center, Rotordynamic Instability Problems in High-Performance Turbomachinery, 1990; p 135-146
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  • 4
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    Seal test program at MIT (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: A seal test program is reported on which was conducted in a dynamic rig. Four different 1-gland labyrinths were tested. The eccentricity, spin rate, whirl rate, and flow are varied independently.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center, Seals Flow Code Development; p 163
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  • 5
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    Plume and wake dynamics, mixing, and chemistry behind an HSCT aircraft (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The chemical evolution and mixing and vortical motion of a High Speed Civil Transport's engine exhausts must be analyzed in order to track the gas and its speciation as emissions are mixed to atmospheric scales. Attention is presently given to an analytic model of the wake dynamical processes which accounts for the roll-up of the trailing vorticity, its breakup due to the Crow instability, and the subsequent evolution and motion of the reconnected vorticity. The concentrated vorticity is noted to wrap up the buoyant exhaust and suppress its continued mixing and dilution. The species tracked encompass those which could be heterogeneously reactive on the surfaces of the condensed ice particles, and those capable of reacting with exhaust soot particle surfaces to form active contrail and/or cloud condensation nuclei.
    Keywords: ENVIRONMENT POLLUTION
    Type: AIAA PAPER 91-3158
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Nonlinear dynamic analysis of shells of revolution by matrix displacement method (1971)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Nonlinear dynamic analysis of shells of revolution under symmetric and asymmetric loads, obtaining solutions for shallow cap buckling
    Keywords: STRUCTURAL MECHANICS
    Type: ; IENCES (|STRUCTURES, STRUCTURAL DYNAMICS AND MATERIALS CONFERENCE; Apr 22, 1970 - Apr 24, 1970; DENVER, CO; US
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    NASA TECHNICAL REPORTS
  • 7
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    Geochemistry and petrography of the MacAlpine Hills lunar meteorites (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: MacAlpine Hills 88104 and 88105, anorthositic lunar meteorites recovered form the same area in Antartica, are characterized. Petrographic studies show that MAC88104/5 is a polymict breccia dominated by impact melt clasts. It is better classified as a fragmental breccia than a regolith breccia. The bulk composition is ferroan and highly aluminous (Al2O3-28 percent).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 55; 3089-310
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  • 8
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    Lattice Boltzmann model for simulation of magnetohydrodynamics (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A numerical method, based on a discrete Boltzmann equation, is presented for solving the equations of magnetohydrodynamics (MHD). The algorithm provides advantages similar to the cellular automaton method in that it is local and easily adapted to parallel computing environments. Because of much lower noise levels and less stringent requirements on lattice size, the method appears to be more competitive with traditional solution methods. Examples show that the model accurately reproduces both linear and nonlinear MHD phenomena.
    Keywords: PLASMA PHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 67; 3776-377
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  • 9
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    New observations on the quartz monzodiorite-granite suite (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Five new fragments of quartz monzodiorite (QMD) were identified in particles from soil 15403, which was collected from the boulder sampled as rock 15405, an impact-melt breccia containing clasts of KREEP basalt, QMD, granite, and a more primitive alkali norite. Petrographic and geochemical studies of the fragments show considerable variation in modal proportions and bulk composition. This heterogeneity is due to unrepresentative sampling in small fragments of coarse-grained rocks. Variations in the proportions of accessory minerals have marked effects on incompatible-trace-element concentrations and ratios. Semiquantitative calculations support the derivation of QMD from 60-percent fractional crystallization of a KREEP basalt magma as suggested by Hess (1989). Apollo 15 KREEP basalt cannot be the actual parent magma because the evolved rocks predate volcanic KREEP basalts. It is suggested that ancient KREEP basalt magmas have crystallized as plutons, with alkali norite clasts offering the only direct evidence of this precursor.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 12, 1990 - Mar 16, 1990; Houston, TX; United States
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    NASA TECHNICAL REPORTS
  • 10
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    Temperature effects on high strain rate properties of graphite/epoxy composites (1991)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A unidirectional graphite epoxy material (AS4/3501-6) was characterized at strain rates ranging from 5 x 10(exp 6) s(exp -1) to 5(exp -1), at room temperature and at 128 C. Results are presented in the form of stress-strain curves to failure. The longitudinal properties remain nearly unchanged with strain rate and temperature. The transverse modulus increases with strain rate but decreases with temperature. The transverse strength and transverse ultimate tensile strain have a positive rate sensitivity at low rates, which changes to negative at intermediate rates and returns to positive rate sensitivity at the highest rates tested. A temperature-time equivalence principle was applied and master curves were obtained for the transverse mechanical properties. The in-plane shear modulus and in-plane shear strength have a positive rate sensitivity. The ultimate intralaminar shear strain has a positive rate sensitivity at low rates, which changes to negative at high rates. At the elevated temperature of 128 C, the ultimate shear strain is 25 to 30 percent higher than the room temperature value, but its strain rate dependence is moderate.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-189082 , NAS 1.26:189082
    Format: application/pdf
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