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At least 379 records · Page 21

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NASA NTRS1972

Comparative evolution of the inverse problems (Introduction to an interdisciplinary study of the inverse problems)

The progressive realization of the consequences of nonuniqueness imply an evolution of both the methods and the centers of interest in inverse problems. This evolution is schematically described together with the various mathematical methods used. A comparative description is given of inverse methods in scientific research, with examples taken from mathematics, quantum and classical physics, seismology, transport theory, radiative transfer, electromagnetic scattering, electrocardiology, etc. It is hoped that this paper will pave the way for an interdisciplinary study of inverse problems.

Sabatier, P. C.↗

NASA NTRS1973

ERTS-B imagery interpretation techniques in the Tennessee Valley

There are no author-identified significant results in this report. The proposed investigation is a continuation of an ERTS-1 project. The principal missions are to serve as the principal supporter on computer and image processing problems for the multidisciplinary ERTS effort of the University of Tennessee, and to carry out research in improved methods for the computer processing, enhancement, and recognition of ERTS imagery.

Gonzalez, R. C.↗

NASA NTRS1973

Marshes and turbid waters in the French Atlantic littoral

The author has identified the following significant results. The multispectral information provided by ERTS-1 is very rich for the coastal regions but the cloud cover, even when only partial, often cuts up the data, and lessens its practical value. The research by densitometric methods has thus far been the most fruitful. It consists of measuring densities along preferential axes. This method has enabled the investigators to perfect a system of computer cartography for the best image. Comparative study of microdensitometric transects in four MSS bands for carefully dilimited profiles on the ground, makes it possible to isolate and recognize various types of countryside: (1) countryside of coastal plains; (2) countryside of coastal sand dunes and beaches; and (3) forms and processes of offshore domains. This study shows the usefulness of the ERTS program in establishing a rapid cartography of the physiographic units of the coastal plains in the interest of a rational program of exploitation and development.

Verger, F.↗

NASA NTRS1974

Methods of radar studies of the moon and the planets from spacecraft

Radar studies of the moon and planets from the earth have been valuable but limited in comparison to radar studies from spacecraft. Autonomous and non-autonomous methods of radar research from space satellites and probes are considered. Results of both the Luna and Surveyor series of lunar spacecraft are presented. It is concluded that use of radar in spacecraft allows valuable, high resolution measurement even near the limb and on the back side of the moon.

Krupenio, N. N.↗

NASA NTRS1975

Design and fabrication of Rene 41 advanced structural panels

The efficiency was investigated of curved elements in the design of lightweight structural panels under combined loads of axial compression, inplane shear, and bending. The application is described of technology generated in the initial aluminum program to the design and fabrication of Rene 41 panels for subsequent performance tests at elevated temperature. Optimum designs for two panel configurations are presented. The designs are applicable to hypersonic airplane wing structure, and are designed specifically for testing at elevated temperature in the hypersonic wing test structure located at the NASA Flight Research Center. Fabrication methods developed to produce the Rene panels are described, and test results of smaller structural element specimens are presented to verify the design and fabrication methods used. Predicted strengths of the panels under several proposed elevated temperature test load conditions are presented.

Greene, B. E.↗

NASA NTRS1976

NASA software specification and evaluation system design, part 1

The research to develop methods for reducing the effort expended in software and verification is reported. The development of a formal software requirements methodology, a formal specifications language, a programming language, a language preprocessor, and code analysis tools are discussed.

Source record↗

NASA NTRS1976

NIM and CAMAC module studies

The feasibility of adapting two NIM and two CAMAC modules for space research was studied. Methods are outlined for reducing the power in each module by approximately fifty percent. Components that could not be replaced from the NASA approved component list are identified. Special problems associated with grounding, vacuum operation, temperature variations, vibration and shock are outlined. Suggested solutions for these problems are discussed.

Pierce, J. F.↗

NASA NTRS1978

Laboratory and community studies of aircraft noise effects

The noise effects programs objective is to develop aircraft noise criteria and noise reduction methods for achieving greater community and passenger acceptance of air transportation systems. The approach consists of laboratory tests to subjectively evaluate the properties of aircraft-generated noise that are responsible for causing annoyance and field surveys to study the broader problems of community and passenger acceptability. The program is organized into two major thrusts: community acceptance and passenger acceptance. The community acceptance includes subjective response studies of single and multiple aircraft overflights as well as longer term community noise exposure. Emphasis is on the development of units and indices which accurately quantify annoyance. The passenger acceptance program includes studies to determine acceptably levels of interior noise and vibration for speech intelligibility and comfort of crew and passengers. Selected results from several recent studies are presented to indicate the nature, scope, and methods of the research program.

Stephens, D. G.↗

NASA NTRS1977

A comparison of digitally simulated holographic images with actual holographic images

In making digitally generated holograms the digital computer and its associated plotting equipment degrade the quality of the hologram. It is necessary then to study the computer generated hologram in terms of these degradations. A computer simulated optical processor allows the results to be observed via computer simulated images. This research reports a method for optimizing the computer image reconstruction and compares these images with optically produced holographic images. The versatility of the simulated optical processor is illustrated by several spatial filtering and hologram reconstructions.

Calhoun, M. D.↗

NASA NTRS1982

Measuring Interdiffusion in Binary Liquids

Liquid-phase binary interdiffusion sample is prepared by enclosing wires of two metals in a capillary tube with ends touching. While sample is at elevated temperature, tube is kept oriented with lighter metal at top to prevent convection. New method is potential research tool in such areas as zone refining of metals, recycling of spent fuel rods, and improving removal of slag and inclusions from steel castings.

Gelles, S. H.↗

NASA NTRS1981

Recent progress towards predicting aircraft ground handling performance

Capability implemented in simulating aircraft ground handling performance is reviewed and areas for further expansion and improvement are identified. Problems associated with providing necessary simulator input data for adequate modeling of aircraft tire/runway friction behavior are discussed and efforts to improve tire/runway friction definition, and simulator fidelity are described. Aircraft braking performance data obtained on several wet runway surfaces are compared to ground vehicle friction measurements. Research to improve methods of predicting tire friction performance are discussed.

Yager, T. J.↗

NASA NTRS1982

An overview of NASA's role in maneuvering missile aerodynamic technology

This paper presents an overview of the role NASA has had and continues to pursue in providing missile aerodynamic technology. In the past, NASA has provided considerable support to the missile industry and the military. The support has generally taken the form of theoretical aerodynamic analyses, experimental studies to provide solutions for specific problems, and the documentation of existing foreign missile systems and domestic missiles. In 1975, NASA shifted its missile-related efforts in aerodynamics from this largely service role to one of conducting more basic research. The areas of research include: innovative methods for roll control of cruciform missiles, airbreathing missiles with maneuver requirements, and an advanced generation of monoplanar missiles for efficient supersonic carriage and delivery.

Sawyer, W. C.↗

NASA NTRS1983

Nonlinear transformat

A technique for designing automatic flight controllers for aircraft which utilizes the transformation theory of nonlinear systems to linear systems is presently being developed at NASA Ames Research Center. A method is considered in which a given nonlinear is transformed to a controllable linear system in Brunovsky canonical form. A linear approximation is introduced to the nonlinear system called the modified tangent model. This model is easily computed. Constructing the transformation for this model enables the designer to find an approximate transformation for the nonlinear system.

Ford, H.↗

NASA NTRS1984

Research in computer science

The research efforts of University of Virginia students under a NASA sponsored program are summarized and the status of the program is reported. The research includes: testing method evaluations for N version programming; a representation scheme for modeling three dimensional objects; fault tolerant protocols for real time local area networks; performance investigation of Cyber network; XFEM implementation; and vectorizing incomplete Cholesky conjugate gradients.

Ortega, J. M.↗

NASA NTRS1986

Estimating Crop Yields From Multispectral Reflectance

Three reports describe research on proposed method for estimating crop yields by combining meteorological data with satellite measurements of reflected radiation to estimate crop-absorbed radiation. Concept, when tested over large areas, forms basis for evaluating crop conditions and estimating yields over regions where ground observations too costly or too difficult.

Daughtry, C.↗

NASA NTRS1984

Ultrapressure materials science

Three active areas of research at ultra pressure are pursued, i.e., diffraction studies with the Cornell High Energy Synchrotron Source (CHESS), band gap and absorption edge effects, indentor-anvil experiments and theory and research to attain higher pressures. The range over which X-ray diffraction data and absorption edge data are obtained is extended to 700 kbars. Using the indentor technique pressures of 2.1 Mbars are obtained. Research results and methods are discussed.

Ruoff, A. L.↗

NASA NTRS1985

Experiences with a preliminary NICE/SPAR structural analysis system

Development of a new structural analysis system based on the original SPAR finite element code and the NICE system is described. The system is denoted NICE/SPAR. NICE was designed at Lockheed Palo Alto Research Laboratory and contains data management utilities, a command language interpreter, and a command language definition for integrating engineering computational modules. SPAR is a system of programs used for finite element structural analysis developed for NASA by Engineering Information Systems, Inc. It includes many complementary structural analysis and utility functions which communicate through a common database. The work on NICE/SPAR was motivated by requirements for a highly modular and flexible structural analysis system to use as a tool in carrying out research in computational methods and exploring new computer hardware. Analysis examples are presented which demonstrate the benefits gained from a combination of the NICE command language with the SPAR computational modules.

Lotts, C. G.↗

NASA NTRS1986

The influence of velocity variability on the determination of wind profiles

High sensitivity radars allow the determination of velocity estimates at time resolutions down to one minute or better. Because of the variability introduced to the mean wind due to turbulence and waves, the high resolution profiles may not be too useful for forecasting applications, although they yield the most realistic estimate of the instantaneous wind profile. Profiles of wind speed and direction, vertical velocity and echo power, which were deduced in real-time on 23 August 1981 with the spaced antenna drift mode of the SOUSY-VHF-Radar are shown. Whereas these profiles were measured within 1 minute, the operating routine allowed the selection of variable (longer) measuring periods, and one has to search for the optimum duration of the data averaging period. A high time resolution wind vector diagram is given which gives an idea of the temporal variability. The data were obtained with the spaced antenna technique, which allows a good estimate of the horizontal wind without having to correct for the vertical velocity component. The wind vectors specifically indicate a quasi-periodic variation in direction. This is assumed to be due to gravity waves since the vertical velocity also shows periodical variations with the same period. The consistency of these spaced-antenna VHF radar results along with the radiosonde data convinced researchers that the method is quite suitable for wind profiling applications.

Rottger, J.↗