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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Quadratic performance index generation for optimal regular design.

Application of optimal control theory to practical problems has been limited by the difficulty of prescribing a performance index which accurately reflects design requirements. The task of deriving equivalent performance indices is considered in the present paper for a plant that is a completely controllable, scalar linear system with state feedback. A quadratic index is developed which leads to an optimal design performance satisfying some of the classical performance criteria.

Bullock, T. E.↗
NASA NTRS1974

Regularity in the control of the free-running sleep-wakefulness rhythm

In the present experiment, rigid control over the sleep and wake-up times was employed in an attempt to contain the natural rhythm to a 24-hr cycle. Eight subjects were isolated from all time and social cues for 10 days. They were placed on a rigid schedule of sleep between 11 p.m. and 7 a.m. The results indicate that, for practical purposes, the free-running sleep-wakefulness rhythm can be contained to a 24-hr cycle by rigid control of the sleep portion of the cycle. When part of the control was released by allowing the subjects to sleep beyond 7 a.m., they slept an average of 67 min longer and showed sleep latencies which averaged 73 min. From these data it is concluded that control of the sleep portion of the sleep-wakefulness cycle, particularly control of the wake-up time, is sufficient to contain the free-running sleep-wakefulness rhythm to a 24-hr cycle.

Webb, W. B.↗
NASA NTRS1975

Regular radiation field pulses produced by intracloud lightning discharges

Sequences or bursts of uniform pulses have been recorded during a large fraction of intracloud lightning discharges in Florida and Arizona. The wave form of a typical pulse begins with a fast large-amplitude portion followed by a small and slowly varying overshoot. The full width and half maximum of the large amplitude peak is typically 0.75 microsec, and the time intervals between pulses are typically 5 microsec in both maritime and continental storms. The pulse shapes and interval times suggest that the source of these pulses in an intracloud dart-stepped leader process similar to that which has been photographed in discharges to ground.

Krider, E. P.↗
NASA NTRS1975

Certain regularities of geomagnetic and Baric fields at high latitudes

The existence of a relation between the variations of magnetic field at earth's surface in near-pole regions and the sector structure of the interplanetary magnetic field is considered as the evidence of the influence of the solar wind with its magnetic field on the processes proceeding in the magnetosphere. Two peculiarities between geomagnetic and interplanetary fields are discussed in detail: the north-south and spring-autumn asymmetry.

Mansurov, S. M.↗
NASA NTRS1976

Diffraction of a shock wave by a compression corner. I - Regular reflection

The unsteady, two-dimensional flowfield resulting from the interaction of a moving planar shock wave with a compression corner is determined using a second-order, discontinuity-fitting, finite-difference approach. The time-dependent Euler equations are transformed to normalize the distance between the body and peripheral shock and to include the existing self-similar property of the flow. The resulting set of partial differential equations in conservation-law form is then solved in a time-dependent fashion using MacCormack's scheme. The vortical singularity, which lies on the body surface, and the single reflected shock are both treated as discontinuities in the numerical procedure. The results of the numerical simulation compare quite favorably with existing experimental interferograms and yield better flowfield resolution than previous first-order, shock-capturing, numerical solutions.

Kutler, P.↗
NASA NTRS1977

The critical velocity phenomenon and the origin of the regular satellites

A theory is developed for the formation of the satellite systems which are likely to have been formed in situ, that is, not by capture of the satellite by the central planet. The foundation of the theory is the observation of the similarity between the band structure of such satellites and the band structure of cosmically abundant elements. That means that the values of the quantity log Gamma, where Gamma is the ratio of the mass of the central body to the orbital radius of the secondary body, are grouped into three bands which can be identified with the three bands into which are grouped the values of the ratio of the mass of a central body to the distance at which the kinetic energy of a freely falling cloud of atoms of a given kind equals the ionization energy. A coherent series of processes that could have led to the formation of satellites is outlined. The theory is valid also for planets, since the above-mentioned band structure is noted for the sun-planets system also.

De, B. R.↗
NASA NTRS1985

The discovery of a 25 min regular modulation in the X-ray flux from 2S0142 + 61

A 13 hr observation of 2S0142 + 61 on August 27, 1984 by EXOSAT shows the X-ray flux of 2S0142 + 61 to be modulated with a period of 1456+/-6 s. The 1-10 keV spectrum is two component with an approximately 0.7 keV thermal and 0.0 energy index power law, with 30 percent of the total luminosity in the thermal component. The spectrum is absorbed by about 1 x 10 to the 22nd H per sq cm. Only the hard component is pulsed with a 3 to 10 keV peak to mean amplitude of 35 percent. Below 2 keV the modulation is less than a few percent. The total 1-10 keV luminosity is 3.5 x 10 to the 32nd erg/s for a distance of 100 pc. Possible optical counterparts are discussed.

White, N. E.↗