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At least 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Nonsmooth trajectory optimization - An approach using continuous simulated annealing

An account is given of the properties of a continuous simulated annealing algorithm that can function as a global optimization tool for nonsmooth dynamic systems, as shown in the case of a trajectory-optimization program implementation. The approach is shown to successfully solve the problem of nonsmooth trajectory optimization for a high performance rigid-body aircraft. The results obtained demonstrate the superiority of the simulated annealing algorithm over widely used algorithms.

Lu, Ping↗
NASA NTRS1989

Locally optimal-digital redesign of continuous-time systems

This paper presents a new optimal digital redesign technique for finding a dynamic digital control law from the given continuous-time counterpart by minimizing a local quadratic performance index. The quadratic performance index is chosen as the integral of the weighted squared difference between the states of the original closed-loop system and those of the digitally controlled closed-loop system at any instant between each sampling period. The developed optimal digital redesign control law enables the states of the digitally controlled closed-loop system 10 closely match those of the original closed-loop system at any instant between each sampling period, and it can easily be implemented using microcomputers with a relatively large sampling period.

Shieh, Leang-San↗
NASA NTRS1988

Fatigue damage criteria - Matrix, fibers and interfaces of continuous fiber reinforced metal matrix composites

Continuous fiber reinforced metal matrix composites (MMC) are projected for use in high temperature, stiffness critical parts that will be subjected to cyclic loadings. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four catagories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage are discussed and illustrated by examples. The emphasis is on the fatigue of unnotched laminates.

Johnson, W. S.↗
NASA NTRS1992

Tunable diode laser-pumped Tm,Ho:YLF laser operated in continuous-wave and Q-switched modes

Tunable continuous-wave and pulsed laser output was obtained from a Tm-sensitized Ho:YLiF4 crystal at subambient temperatures when longitudinally pumped with a diode laser array. A conversion efficiency of 42 percent and slope efficiency of approximately 60 percent relative to the absorbed pumped power have been achieved at a crystal temperature of 275 K. The emission spectrum was etalon tunable over a range of 16/cm centered at 2067 nm with fine tuning capability of the transition frequency with crystal temperature at measured rate of -0.03/cm/K. Output energies of 0.22 mJ per pulse and 22 ns pulse duration were recorded at Q-switch frequencies that correspond to an effective upper laser level lifetime of 6 ms, and a pulse energy extraction efficiency of 64 percent.

Mcguckin, B. T.↗
NASA NTRS1943

Some Investigations of the General Instability of Stiffened Metal Cylinders IV : Continuation of Tests of Sheet-covered Specimens and Studies of the Buckling Phenomena of Unstiffened Circular Cylinders

This is the fourth of a series of reports covering an investigation of the general instability problem by the California Institute of Technology. The first five reports of this series cover investigations of the general instability problem under the loading conditions of pure bending and were prepared under the sponsorship of the Civil Aeronautics Administration. The succeeding reports of this series cover the work done on other loading conditions under the sponsorship of the National Advisory Committee for Aeronautics. This report is to deal primarily with the continuation of tests of sheet-covered specimens and studies of the buckling phenomena of unstiffened circular cylinders.

CYLINDERS, STEEL↗
NASA NTRS1943

Some investigations of the general instability of stiffened metal cylinders III : continuation of tests of wire-braced specimens and preliminary tests of sheet-covered specimens

This is the third of a series of reports covering an investigation of the general instability problem by the California Institute of Technology. The first five reports of this series cover investigations of the general instability problem under the loading conditions of pure bending and were prepared under the sponsorship of the Civil Aeronautics Administration. The succeeding reports of this series cover the work done on other loading conditions under the sponsorship of the National Advisory Committee for Aeronautics. This report is concerned primarily with the continuation of the tests of wire-braced specimens, and preliminary tests of sheet-covered specimens that had been made in the experimental investigation on the problem of the general instability of stiffened metal cylinders at the C.I.T.

ALUMINUM ALLOYS, SHEETS, ALCOA 17ST↗
NASA NTRS1931

A method of calculating the ultimate strength of continuous beams

The purpose of this study was to investigate the strength of continuous beams after the elastic limit has been passed. As a result, a method of calculation, which is applicable to maximum load conditions, has been developed. The method is simpler than the methods now in use and it applies properly to conditions where the present methods fail to apply.

Newlin, J A↗
NASA NTRS1994

Continuous-Wave, Diode-Pumped, Tunable Tm,Ho:YLF Laser

Unique features include high efficiency and tunability at wavelengths near 2.067 micrometers. Continuous-wave, diode-pumped Tm,Ho:YLF laser tuned by tilting Fabry-Perot etalon and/or adjusting temperature of Tm,Ho:YLF crystal. Proposed for use in remote sensing of winds and in remote sensing of CO2 and H2O, of which many strong absorption lines over-lap laser tuning range. Range extended by tuning to wave-length between CO2 and H2O absorption peaks.

Mcguckin, Brendan T.↗
NASA NTRS1994

Continuous-Flow Gas-Phase Bioreactors

Continuous-flow gas-phase bioreactors proposed for biochemical, food-processing, and related industries. Reactor contains one or more selected enzymes dehydrated or otherwise immobilized on solid carrier. Selected reactant gases fed into reactor, wherein chemical reactions catalyzed by enzyme(s) yield product biochemicals. Concept based on discovery that enzymes not necessarily placed in traditional aqueous environments to function as biocatalysts.

Wise, Donald L.↗
NASA NTRS1994

Increasing Sensitivity In Continuous-Flow Electrophoresis

Sensitivity of continuous-flow electrophoresis (CFE) chamber increased by introducing lateral gradients in concentration of buffer solution and thickness of chamber. Such gradients, with resulting enhanced separation, achieved in CFE chamber with wedge-shaped cross section and collateral flow. Enables improved separations of homogeneous components of mixtures of variety of biologically important substances.

Sharnez, Rizwan↗
NASA NTRS1992

Ninth Annual NASA/Contractors Conference on Quality and Productivity. World Class Excellence: The Journey Continues. Conference presentations

The topics covered include the following: The George M. Low Trophy; total quality assessment and measurement; using award criteria to improve organizational effectiveness; results--keeping an eye on the bottom line; capturing customer satisfaction; moving from management to leadership; leadership versus management; transforming the management team; leadership success stories; success stories in the quest for excellence; small business successes; education success stories; government success stories; tools and techniques for total quality management (TQM) integration; planning and organizing for TQM integration; successful stories for implementing system level TQM/CI tools; assessing TQM results; establishing an environment for continuous improvement at NASA; empowerment; synergism of partnering; and partnerships in education.

Templeton, Geoffrey B.↗
NASA NTRS1993

Aeronautical engineering: A continuing bibliography with indexes (supplement 294)

This issue of Aeronautical Engineering - A Continuing Bibliography with Indexes lists 590 reports, journal articles, and other documents recently announced in the NASA STI Database. The coverage includes documents on the engineering and theoretical aspect of design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines) and associated components, equipment, and systems. It also includes research and development in aerodynamics, aeronautics, and ground support equipment for aeronautical vehicles. The bibliographic series is compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). Seven indexes are included: subject, personal author, corporate source, foreign technology, contract number, report number, and accession number.

Source record↗
NASA NTRS1994

Aeronautical engineering: A cumulative index to a continuing bibliography (supplement 300)

This publication is a cumulative index to the abstracts contained in supplements 288 through 299 of Aeronautical Engineering: A Continuing Bibliography. The bibliographic series is compiled through the efforts of the Center for Aerospace Information of the National Aeronautics and Space Administration (NASA). Seven indexes are included: subject, personal author, corporate source, foreign technology, contract number, report number, and accession number.

Source record↗
NASA NTRS1994

Continuous measurement of aircraft wing icing

Ice formation on the wings of aircraft is a problem that has plagued air travel since its inception. Several recent incidents have been attributed to ice formation on the lifting surfaces of wings. This paper describes a SBIR Phase 1 research effort on the use of small flat dielectric sensors in detecting a layer of ice above the sensor. The sensors are very small, lightweight, and inexpensive. The electronics package that controls the sensor is also small, and could be even smaller using commonly available miniaturization technologies. Thus, several sensors could be placed on a surface such that a representative ice thickness profile could be measured. The benefits offered by developing this technology go beyond the safety improvements realized by monitoring ice formation on the wings of an aircraft. Continuous monitoring of anti-icing fluid concentrations on the ground would warn the pilot of impending fluid failure as well as allowing the stations to use less de-icing solution per aircraft. This in turn would increase the safety of takeoffs and reduce the overall discharge of de-icing solution into the environment, thus reducing the biohazard of the de-icing procedure.

Yao, Stephen S. C.↗
NASA NTRS1994

Continuous unidirectional fiber reinforced composites: Fabrication and testing

The study of the anisotropic mechanical properties of an inexpensively fabricated composite with continuous unidirectional fibers and a clear matrix was investigated. A method has been developed to fabricate these composites with aluminum fibers and a polymer matrix. These composites clearly demonstrate the properties of unidirectional composites and cost less than five dollars each to fabricate.

Weber, M. D.↗
NASA NTRS1994

Continuous measurements of the total ozone content in the full moon period

Presented are the experimental data on the total ozone content obtained during continuous measurements (day-night-...-night-day) by Brewer 044 spectrophotometer near the Issyk Kul Lake (42.59N, 77.04W) at 1650 m above the sea level at full moon from 13 to 18 October 1989 under anomalously high transparent atmospheric conditions (the horizontal visibility range exceeded 50 km). At night the total O3 content decreased regularly to about 20 percent of the average daytime values. The minimum values at night were observed in 1-2 hours after the maximum solar dip below the horizon. In the daytime the measurements were carried out from direct Sun, at night - from the Moon. The values of the total ozone content for adjacent measurements from the Sun and from the Moon in the evening as well as in the morning are in good agreement.

Ishov, Alexander G.↗