Structure and stability of discrete-time optimal systems
Discrete-time optimal linear systems structure and stability, assuming quadratic costs and perfect observability
Rappaport, D.↗
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Discrete radiation from rotating periodic sources
Discrete frequency sound radiation from rotating periodic sources covering rotor blade noise in near field and from disk loading asymmetries
Wright, S. E.↗
Exponential absolute stability of discrete systems
Exponential absolute stability of nonlinear discrete systems of Lure type, deriving modified frequency condition
Siljak, D. D.↗
Stability conditions derived from spectral theory - Discrete systems with periodic feedback
Stability conditions of linear discrete system with periodic feedback from spectrum location of bounded linear operator acting in Banach space
Davis, J. H.↗
Estimation of the mean of a discrete parameter, covariance stationary, stochastic process in rotation sampling
Discrete parameter covariance stationary stochastic process in rotation sampling, deriving minimum variance unbiased linear population mean estimator by constrained optimization procedure
Nishikawa, K.↗
Theoretical study of corrugated plates: Shear stiffness of a trapezoidally corrugated plate with discrete attachments to a rigid flange at the ends of the corrugations
Analysis and numerical results are presented for the elastic shear stiffness of a corrugated shear web with a certain type of discrete attachments at the ends of the trough lines of the corrugations, namely point attachments to a rigid flange which interferes with the deformations of the end cross sections by preventing downward movement but permitting upward (lifting off) movement. The analysis is based on certain assumed modes of deformation of the cross sections in conjunction with the method of minimum total potential energy and the calculus of variations in order to obtain equations for the manner in which the assumed modes of deformation vary along the length of the corrugation. The numerical results are restricted to the case of equal-width crests and troughs but otherwise apply to a wide variety of geometries. They are in the form of graphs which give the overall shear stiffness as a fraction of the overall shear stiffness that could be obtained by having continuous attachment at the ends of the corrugations.
Hsiao, C.↗
Low-energy electron transport with the method of discrete ordinates
The one-dimensional discrete ordinates code ANISN was adapted to transport low energy (a few MeV) electrons. Calculated results obtained with ANISN were compared with experimental data for transmitted electron energy and angular distribution data for electrons normally incident on aluminum slabs of various thicknesses. The calculated and experimental results are in good agreement for a thin slab (0.2 of the electron range), but not for the thicker slabs (0.6 of the electron range). Calculated results obtained with ANISN were also compared with results obtained using Monte Carlo methods.
Bartine, D. E.↗
Discrete ordinate theory of radiative transfer. 2: Scattering from maritime haze
Discrete ordinate theory was used to calculate the reflected and transmitted radiance of photons which have interacted with plane parallel maritime haze layers. The results are presented for three solar zenith angles, three values of the surface albedo, and a range of optical thicknesses from very thin to very thick. The diffuse flux at the lower boundary and the cloud albedo were tabulated. The forward peak and other features in the single scattered phase function caused the radiance in many cases to be very different from that for Rayleigh scattering. The variation of the radiance with both the zenith or nadir angle and the azimuthal angle is more marked, and the relative limb darkening under very thick layers is greater, for haze than for Rayleigh scattering. The downward diffuse flux at the lower boundary for A = O is always greater and the cloud albedo is always less for haze than for Rayleigh layers.
Kattawar, G. W.↗
Discrete input equipment design study
The study to improve the reliability of the LUT system by discrete input equipment (DIE) is reported. Subjects discussed include: specifications, packaging, aircraft integrated systems, and word formats DIE. It is recommended that maximal use of advanced technology be made, particularly the "know how' developed on the Saturn project.
Source record↗
Effects of roughness on heating and boundary-layer transition. Part 2: effects of discrete roughness on heating
A preliminary investigation on the effects of roughness on heating in delta wing orbiters was conducted on the windward surface of the vehicle. The purpose of the experiment was to determine the feasibility of using parametric relationships obtained from discrete roughness effects on heating in flat plates and cones, to complex shuttle configurations. An attempt was also made to characterize what parameters were needed to influence roughness. Experimental results show that effective roughness Reynolds numbers are less than or equal to those of flat plates at the same edge Mach number, but, the roughness correlations for plates and cones cannot be applied to the shuttle configuration.
Mateer, G. G.↗
Discrete component S-band power amplifier
A spacecraft S-band power amplifier for Nimbus satellite is reported that achieves stability by use of moderate Q input and output circuits. The discrete component amplifier uses distributed inductance and small piston capacitors for resonance and impedance matching of the transistor to 50 ohm input and output.
Block, A. F.↗
Computational requirements for a discrete Kalman filter.
Computational requirements - i.e., computing time per cycle (iteration) and required storage - which determine minimum sampling rates and computer memory size, were obtained as functions of the dimensions of the important system matrices for a discrete Kalman filter. Two types of measurement processing are discussed: simultaneous and sequential. It is shown that it is often better to process statistically independent measurements in more than one batch and then use sequential processing than to process them together via simultaneous processing.
Mendel, J. M.↗
Theory of discrete wave packets in the solar wind.
Discrete wave packets were observed by Ogo 5 and earlier satellites. These waves were believed to be in the whistler mode. Since their group velocities were found to be smaller than the solar-wind speed, these waves could not have been generated in the bow shock and could not have propagated upstream later. The present theory discusses a mechanism similar to that of the echo phenomenon in plasma physics discovered in recent years. The present theory enables us to explain (a) why the wave packets were associated with the bow shock, (b) why the wave packets were characterized by coherent oscillations, and (c) why the wave packets had group velocities smaller than the solar wind and yet could still occur in the solar wind. In short, our theory is able to interpret all the essential features deduced from the observational data.
Wu, C. S.↗
Application of positive-real functions in hyperstable discrete model-reference adaptive system design.
Proposal of an algorithmic procedure, based on mathematical programming methods, to design compensators for hyperstable discrete model-reference adaptive systems (MRAS). The objective of the compensator is to render the MRAS insensitive to initial parameter estimates within a maximized hypercube in the model parameter space.
Karmarkar, J. S.↗
Stability conditions derived from spectral theory - Discrete systems with periodic feedback.
By use of the spectral theory of linear operators, necessary and sufficient conditions are derived for the stability of a class of discrete time feedback systems with a periodically time-varying feedback gain. These conditions involve a Nyquist plot for an equivalent time-invariant system which may be determined from the frequency response function of the system under consideration. In the special case of a scalar-input scalar-output system, these conditions may be given in a particularly simple form.
Davis, J. H.↗
Discrete rotor noise.
Description of a single unified theory to account generally for the discrete radiation from the whole family of heavily loaded axial flow rotors, including helicopter rotors, propellers, and compressors. The approach used is to analyze, in a Fourier way, the periodic blade loading variation (azimuth profile) into blade loading harmonics (BLH) and then sum the total radiation from each BLH. The basic differences between high and low solidity rotor spectrums are considered, emphasizing the difference between subsonic and supersonic rotor noise. The special effect of helicopter blade slap and compressor rotor-stator interaction is discussed, and measured rotor spectrums have been included to help illustrate the theory.
Wright, S. E.↗
Diffuse galactic X-rays from discrete sources.
The galactic ridge is interpreted as a population of intrinsically weak X-ray sources, and calculations are presented of the predicted intensity as a function of scale height and radial gradient. Observations of diffuse galactic X-radiation above 1 keV impose severe constraints on discrete-source interpretations of the galactic-plane excess observed at 0.25 keV.
Silk, J.↗
Discrete-time demodulation of continuous-time signals.
Nonlinear stochastic estimation theory is applied to the problem of obtaining discrete-time demodulator structures for the common types of analog communication signals. A stochastic communication model is presented that can be treated with current results in estimation theory. Approximate algorithms are developed for the estimation problem that yield mathematically realizable receiver structures for the cases of AM, PC, and FM. The digital receivers yield performance characteristics that compare favorably with those of their analog counterparts.
Kelly, C. N.↗