SEARCH · Engineering Papers

Results for “NpO”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS1990

More About Lens Antenna For Mobile/Satellite Communication

Report presents additional details of design of proposed phased-array antenna described in "Lens Antenna for Mobile/Satellite Communication" (NPO-16948). Intended to be compact and to lie flat on top of vehicle on ground. Transmits and receives circularly polarized radiation in frequency ranges of 821 to 825 MHz and 860 to 870 MHz. Transmitting and receiving beams electronically steerable to any of 48 evenly spaced directions to provide complete azimuth coverage, and would be fixed, but wide, in elevation, to provide coverage at elevation angles from 20 degrees to 60 degrees.

Rahmat-Samii, Y.↗

NASA NTRS1990

Directional Couplers For Detecting Circular Waveguide Modes

Samples of TE11 and TE12 modes coupled selectively out of circular waveguide. Report presents additional details of theory, construction, and measured operating characteristics of directional couplers described in "Microwave Transmitter With Multimode Output Section" (NPO-16826). Couplers consist of tapered rectangular-cross-section waveguides fastened lengthwise to outside of circular waveguide, with uniformly-lengthwise-spaced round coupling holes between each rectangular waveguide and circular waveguide.

Hoppe, Daniel J.↗

NASA NTRS1990

Electrostatic Dispersion Of Drops In Clusters

Electrical charging speeds evaporation. Report presents theoretical study of evaporation and dispersion of electrostatically charged clusters of drops in liquid fuel sprays. Represents extension of studies described in article, "More About Evaporation of Drops in Clusters" (NPO-17594). Undertaken in effort to learn how electrostatic atomization used to disperse fuel better in order to reduce formation of soot in diesel engines and other power and combustion systems.

Bellan, Josette↗

NASA NTRS1991

Environmental Control Of A Genetic Process

E. coli bacteria altered to contain DNA sequence encoding production of hemoglobin made to produce hemoglobin at rates decreasing with increases in concentration of oxygen in culture media. Represents amplification of part of method described in "Cloned Hemoglobin Genes Enhance Growth Of Cells" (NPO-17517). Manipulation of promoter/regulator DNA sequences opens promising new subfield of recombinant-DNA technology for environmental control of expression of selected DNA sequences. New recombinant-DNA fusion gene products, expression vectors, and nucleotide-base sequences will emerge. Likely applications include such aerobic processes as manufacture of cloned proteins and synthesis of metabolites, production of chemicals by fermentation, enzymatic degradation, treatment of wastes, brewing, and variety of oxidative chemical reactions.

Khosla, Chaitan↗

NASA NTRS1991

Trapped-Mercury-Ion Frequency Standard

Report describes principle of operation, design, and results of initial measurements on trapped-mercury-ion frequency-standard apparatus at NASA's Jet Propulsion Laboratory. New frequency standard being developed. Based on linear ion trap described in (NPO-17758). Expected to show much better short-term frequency stability because of increased ion-storage capacity.

Prestage, John D.↗

NASA NTRS1991

Stacking Oxygen-Separation Cells

Simplified configuration and procedure developed for assembly of stacks of solid-electrolyte cells separating oxygen from air electrochemically. Reduces number of components and thus reduces probability of such failures as gas leaks, breakdown of sensitive parts, and electrical open or short circuits. Previous, more complicated version of cell described in "Improved Zirconia Oxygen-Separation Cell" (NPO-16161).

Schroeder, James E.↗

NASA NTRS1991

Growing Cobalt Silicide Columns In Silicon

Codeposition by molecular-beam epitaxy yields variety of structures. Proposed fabrication process produces three-dimensional nanometer-sized structures on silicon wafers. Enables control of dimensions of metal and semiconductor epitaxial layers in three dimensions instead of usual single dimension (perpendicular to the plane of the substrate). Process used to make arrays of highly efficient infrared sensors, high-speed transistors, and quantum wires. For fabrication of electronic devices, both shapes and locations of columns controlled. One possible technique for doing this electron-beam lithography, see "Making Submicron CoSi2 Structures on Silicon Substrates" (NPO-17736).

Fathauer, Obert W.↗

NASA NTRS1991

Stacked-Gate FET's For Analog Memory Elements

Three-terminal, double-stacked-gate field-effect transistor (FET), developed as analog memory element. Particularly suited for use as synapse with variable connection strength in electronic neural network. Provides programmable, nonvolatile resistive connection, somewhat in manner of porous-gate FET described in "Porous-Floating-Gate Field-Effect Transistor" (NPO-17532). Resembles commercial erasable programmable read-only memory (EPROM) device, except for thickness of layers of silicon dioxide electrically isolating gates. Either p-channel or n-channel device.

Thakoor, Anilkumar P.↗

NASA NTRS1991

Alternative AlxGa1-xAs/GaAs Transistors For Neural Networks

Further development efforts yield alternative version of transistors described in "High-Gain AlxGa1-xAs/GaAs Transistors For Neural Networks" (NPO-18101). Efforts focused on determining effects of various aspects of design and of fabrication processes upon leakage currents and on current gain.

Kim, Jae-Hoon↗

NASA NTRS1991

Three-Dimensional Acousto-Optical Spectrum Analyzer

Experimental acousto-optical Bragg-cell spectrum analyzer achieves subhertz frequency resolution. System represents extension to three dimensions of two-dimensional spectrum-analyzer concept described in, "Two-Dimensional Acousto-Optical Spectrum Analyzer" (NPO-18092). First and second dimensions two spatial dimensions of charge-coupled-device (CCD) imaging array. Third dimension time, as sampled at frame rate of CCD array.

Ansari, Homayoon↗

NASA NTRS1991

Detection Of Motion With A Phase-Conjugate Mirror

Photorefractive image-processing apparatus generates images of rapidly moving objects and suppresses images of stationary and slowly moving objects. Resembles apparatus described in article, "Improved Interferometric Photorefractive Optical Processor", NPO-17773. Principle of operation similar, except system includes two video cameras and instead of transparencies, electro-optical spatial light modulators used to impress image information from video camera on laser beams.

Cheng, Li-Jen↗

NASA NTRS1991

Estimating SAR Doppler Shifts From Quasi-Homogeneous Targets

Linear-estimator subalgorithm optimized for local terrain. Algorithm processes some of information in synthetic-aperture-radar echoes from quasi-homogeneous targets, yielding optimal estimates of Doppler frequency shifts. Differs from one described in article, "Estimating SAR Doppler Shifts From Homogeneous Targets", NPO-17869, though offers similar advantages for measurements of wind shears and speeds of ocean currents. Derivation of algorithm involves some of same terminology and simplifying assumptions, however, target area considered quasi-homogeneous in sense it consists of patchwork of subareas, each of which is homogeneous target differing from its neighbors. This assumption more realistic than assumption of homogeneity.

Jin, Michael Y.↗

NASA NTRS1991

Two-Period Gratings For Surface-Emitting Lasers

Grating surfaces having two spatial periods tailored to obtain desired proportions of output coupling and inward reflection. Solid-state lasers of type emitting light perpendicularly to their broad surfaces made more efficient. Same principle also applicable to "Annular-Bragg-Grating Surface-Emitting Laser", (NPO-17912).

Lang, Robert J.↗

NASA NTRS1992

Orifices For Fuel-Film Cooling Of Combustion Chamber

Boundary-layer film of fuel flows along wall of combustion chamber mentioned in article, "Rhenium-Foil Witness Cylinders" (NPO-18224), cooling wall and neutralizing excess of oxidizer in vicinity of wall. Enters chamber through 16 small, replaceable nozzles placed around periphery of fuel-and-oxidizer injector. Adjusted, independently of main injected flow of fuel and oxidizer, by selection of nozzle passing larger or smaller flow.

Knight, B. L.↗

NASA NTRS1992

Single-Event-Upset Laser Scanner With Optical Bias

Light-assisted microelectronic advanced laser scanner (LAMEALS) is augmented version of microelectronic advanced laser scanner (MEALS) described in article, "Laser Scanner Tests For Single-Event Upsets", (NPO-18216). Only major difference, steady illumination from helium/neon laser, argon-ion laser, and/or other source(s) combined with pulsed dye-laser illumination of MEALS into single illuminating beam.

Kim, Quiesup↗

NASA NTRS1992

AlxGa1-xAs Single-Quantum-Well Surface-Emitting Lasers

Surface-emitting solid-state laser contains edge-emitting Al0.08Ga0.92As single-quantum-well (SQW) active layer sandwiched between graded-index-of-refraction separate-confinement-heterostructure (GRINSCH) layers of AlxGa1-xAs, includes etched 90 degree mirrors and 45 degree facets to direct edge-emitted beam perpendicular to top surface. Laser resembles those described in "Pseudomorphic-InxGa1-xAs Surface-Emitting Lasers" (NPO-18243). Suitable for incorporation into optoelectronic integrated circuits for photonic computing; e.g., optoelectronic neural networks.

Kim, Jae H.↗

NASA NTRS1992

Algorithm Calculates Cumulative Poisson Distribution

Algorithm calculates accurate values of cumulative Poisson distribution under conditions where other algorithms fail because numbers are so small (underflow) or so large (overflow) that computer cannot process them. Factors inserted temporarily to prevent underflow and overflow. Implemented in CUMPOIS computer program described in "Cumulative Poisson Distribution Program" (NPO-17714).

Bowerman, Paul N.↗

NASA NTRS1992

Creative-Dynamics Approach To Neural Intelligence

Paper discusses approach to mathematical modeling of artificial neural networks exhibiting complicated behaviors reminiscent of creativity and intelligence of biological neural networks. Neural network treated as non-Lipschitzian dynamical system - as described in "Non-Lipschitzian Dynamics For Modeling Neural Networks" (NPO-17814). System serves as tool for modeling of temporal-pattern memories and recognition of complicated spatial patterns.

Zak, Michail A.↗