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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.

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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

On the control of linear systems using two level periodic output feedback.

A class of second order linear time-invariant systems which are unstable for any constant feedback but which are stabilized by a two level periodic feedback is identified. Necessary and sufficient conditions for this type of stabilization are found. In addition, the sensitivity of the closed-loop system to changes in feedback gains is investigated.

Welch, R. V.↗
NASA NTRS1973

Design of nonlinear resistive networks with prescribed input-output behavior.

This paper considers the problem of designing nonlinear multiport resistive networks for prescribed driving point and transfer characteristics. It is shown that, if the topology of the desired network is given, then the i-v characteristics of the nonlinear elements can be obtained iteratively. This is achieved by implementation of a newly developed steepest descent criterion.

Peikari, B.↗
NASA NTRS1974

Optimal output feedback control of linear systems in presence of forcing and measurement noise

The problem of obtaining an optimal control law, which is constrained to be a linear feedback of the available measurements, for both continuous and discrete time linear systems subjected to additive white process noise and measurement noise was Necessary conditions are obtained for minimizing a quadratic performance function for both finite and infinite terminal time cases. The feedback gains are constrained to be time invariant for the infinite terminal time cases. For all the cases considered, algorithms are derived for generating sequences of feedback gain matrices which successively improve the performance function. A continuous time numerical example is included for the purpose of demonstration.

Joshi, S. M.↗
NASA NTRS1974

Spaceflight tracking and data network operational reliability computer output for MTBF and availability. Appendix V to CSC-1-395

Tables of data are provided to show the availability of Skylab data to selected ground stations during the phases of Skylab preflight, Skylab unmanned condition, and Skylab manned condition. The mean time between failure (MTBF) of the same Skylab functions is tabulated for the selected ground stations. All reliability data are based on a 90 percent confidence interval.

Seneca, V. I.↗
NASA NTRS1975

Psychological stress measurement through voice output analysis

Audio tape recordings of selected Skylab communications were processed by a psychological stress evaluator. Strip chart tracings were read blind and scores were assigned based on characteristics reported by the manufacturer to indicate psychological stress. These scores were analyzed for their empirical relationships with operational variables in Skylab judged to represent varying degrees of situational stress. Although some statistically significant relationships were found, the technique was not judged to be sufficiently predictive to warrant its use in assessing the degree of psychological stress of crew members in future space missions.

Older, H. J.↗
NASA NTRS1977

Stabilized Nd:YAG laser output

Stabilization system consists of feedback-loop-controlled piezoelectric crystal to one of the reflectors to vary optical path length within laser cavity. Average second harmonic of fundamental 1.06 micrometer laser radiation is detected by integrating detector.

Osmundson, J.↗
NASA NTRS1975

Computer output microfilm (FR80) systems software documentation, volume 2

The system consists of a series of programs which convert digital data from magnetic tapes into alpha-numeric characters, graphic plots, and imagery that is recorded on the face of a cathode ray tube. A special camera photographs the face of the tube on microfilm for subsequent display on a film reader. The applicable documents which apply to this system are delineated. The functional relationship between the system software, the standard insert routines, and the applications programs is described; all the applications programs are described in detail. Instructions for locating those documents are presented along with test preparations sheets for all baseline and/or program modification acceptance tests.

Source record↗
NASA NTRS1976

On the total energy output of the nova outburst

It is shown that the postmaximum decline in optical light during the outburst of a normal classical nova is caused by a shift in the wavelength of maximum energy to the ultraviolet. The constant-luminosity phase which was directly observed in Nova FH Ser 1970 may, therefore, be common to all novae, regardless of speed class. This implies that all speed classes of novae have similar energy budgets and that it is the total energy involved in the outburst which produces the variation in the observed characteristics of the novae. Recent thermonuclear runaway models for the outburst also show an extended period of high luminosity and high effective temperature following the initial outburst.

Gallagher, J. S.↗
NASA NTRS1976

Dual output variable pitch turbofan actuation system

An improved actuating mechanism was provided for a gas turbine engine incorporating fan blades of the variable pitch variety, the actuator adapted to rotate the individual fan blades within apertures in an associated fan disc. The actuator included means such as a pair of synchronizing ring gears, one on each side of the blade shanks, and adapted to engage pinions disposed thereon. Means were provided to impart rotation to the ring gears in opposite directions to effect rotation of the blade shanks in response to a predetermined input signal. In the event of system failure, a run-away actuator was prevented by an improved braking device which arrests the mechanism.

Griswold, R. H., Jr.↗
NASA NTRS1973

High speed electrostatic photomultiplier tube for the 1.06 micrometer wavelength. Cup and slat dynode chain combined with flat cathode and coax output produces 0.25 nsec rise time

The Varian cup and slat dynode chain was modified to have a flat cathode. These modifications were incorporated in an all-electrostatic photomultiplier tube having a rise time of 0.25 n sec. The tube delivered under the contract had a flat S-20 opaque cathode with a useful diameter of 5 mm. The design of the tube is such that a III to V cathode support is mounted in place of the existing cathode substrate. This cathode support is designed to accept a transferred III to V cathode and maintain the cathode surface in the same position as the S-20 photocathode.

Sparks, S. D.↗
NASA NTRS1976

The specific light output of cesium iodide crystals

Large area ion chambers for a high energy cosmic ray experiment, scintillating plastic fibers as light pipes for a cosmic ray hodoscope, and an evaluation of clad scintillating light pipes were considered.

Gregory, J. C.↗