433 research outputs found
A bibliography on parallel and vector numerical algorithms
This is a bibliography of numerical methods. It also includes a number of other references on machine architecture, programming language, and other topics of interest to scientific computing. Certain conference proceedings and anthologies which have been published in book form are listed also
Broadband high-gain planar leaky-wave antennas
High-gain, low-cost, planar antennas have attracted a lot of interest in recent years, with
regard to applications as fixed wireless access, satellite reception and various point-to-point
radio links. Microstrip patch arrays have primarily been good candidates, but the complex
feeding mechanisms degrade the antenna performance. A method of producing a high gain
planar antenna with a simple feed has been proposed in an earlier study. This technique
utilises a partially reflective surface (PRS) to introduce a leaky wave and beamforming
effect when placed in front of a waveguide aperture in a ground plane. The partial reflection
can be obtained from periodic arrays, also referred to as Frequency Selective Surfaces
(FSSs) when used for their filtering properties. The research effort in this thesis focuses on
the theory underpinning the beamforming effect of single and double-layer PRSs in a leaky-wave antenna configuration and subsequently on novel leaky-wave antenna designs. [Continues.
Supercomputing in Aerospace
Topics addressed include: numerical aerodynamic simulation; computational mechanics; supercomputers; aerospace propulsion systems; computational modeling in ballistics; turbulence modeling; computational chemistry; computational fluid dynamics; and computational astrophysics
Interaction of Chemistry, Turbulence, and Shock Waves in Hypervelocity Flow
Significant progress was made in the third year of an interdisciplinary experimental, numerical and theoretical program to extend the state of knowledge
and understanding of the effects of chemical reactions in hypervelocity flows. The program addressed the key problems in aerothermochemistry that arise from.the interaction between the three strongly nonlinear effects:
Compressibility; vorticity; and chemistry. Important new results included:
• New data on transition in hypervelocity carbon dioxide flows
• New method of free-piston shock tunnel operation for lower enthalpy
• Accurate new method for computation of self-similar flows
• New experimental data on flap-induced separation at high enthalpy
• Insight into mechanisms active in reacting shear layers from comparison of experiment and computation
• Extensive new data from Rayleigh scattering diagnostics of supersonic shear layer
• Comparison of new experiments and computation of hypervelocity double-wedge flow yielded important differences
• Further first-principles computations of electron collision cross-sections of CO, N_2 and NO
• Good agreement between EFMO computation and experiment of flow over a cone at high incidence
• Extension of LITA diagnostics to high temperature
The Third NASA Goddard Conference on Mass Storage Systems and Technologies
This report contains copies of nearly all of the technical papers and viewgraphs presented at the Goddard Conference on Mass Storage Systems and Technologies held in October 1993. The conference served as an informational exchange forum for topics primarily relating to the ingestion and management of massive amounts of data and the attendant problems involved. Discussion topics include the necessary use of computers in the solution of today's infinitely complex problems, the need for greatly increased storage densities in both optical and magnetic recording media, currently popular storage media and magnetic media storage risk factors, data archiving standards including a talk on the current status of the IEEE Storage Systems Reference Model (RM). Additional topics addressed System performance, data storage system concepts, communications technologies, data distribution systems, data compression, and error detection and correction
Dual-Use Space Technology Transfer Conference and Exhibition
This document contains papers presented at the Dual-Use Space Technology Transfer Conference and Exhibition held at the Johnson Space Center February 1-3, 1994. Possible technology transfers covered during the conference were in the areas of information access; innovative microwave and optical applications; materials and structures; marketing and barriers; intelligent systems; human factors and habitation; communications and data systems; business process and technology transfer; software engineering; biotechnology and advanced bioinstrumentation; communications signal processing and analysis; new ways of doing business; medical care; applications derived from control center data systems; human performance evaluation; technology transfer methods; mathematics, modeling, and simulation; propulsion; software analysis and decision tools systems/processes in human support technology; networks, control centers, and distributed systems; power; rapid development perception and vision technologies; integrated vehicle health management; automation technologies; advanced avionics; ans robotics technologies. More than 77 papers, 20 presentations, and 20 exhibits covering various disciplines were presented b experts from NASA, universities, and industry
Image analysis, modeling, enhancement, restoration, feature extraction and their applications in nondestructive evaluation and radio astronomy
The principal topic of this dissertation is the development and application of signal and image processing to Nondestructive Evaluation (NDE) and radio astronomy;The dissertation consists of nine papers published or submitted for publication. Each of them has a specific and unique topic related to signal processing or image processing in NDE or radio astronomy. Those topics are listed in the following. (1) Time series analysis and modeling of Very Large Array (VLA) phase data. (2) Image analysis, feature extraction and various applied enhancement methods for industrial NDE X-ray radiographic images. (3) Enhancing NDE radiographic X-ray images by adaptive regional Kalman filtering. (4) Robotic image segmentation, modeling, and restoration with a rule based expert system. (5) Industrial NDE radiographic X-ray image modeling and Kalman filtering considering signal-dependent colored noise. (6) Computational study of Kalman filtering VLA phase data and its computational performance on a supercomputer. (7) A practical and fast maximum entropy deconvolution method for deblurring industrial NDE X-ray and infrared images. (8) Local feature enhancement of synthetic radio images by adaptive Kalman filtering. (9) A new technique for correcting phase data of a synthetic-aperture antenna array
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