Dynamic stability of thin elastic plates under the action of non-deterministic loads.
Thin elastic plates dynamic stability under random distribution edge loading using theory of linear stochastic systems
Fontenot, L. L.↗
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Determination of optimal stock level for a group of customers under conditions of random demand
Optimal stock level with algorithm for random distribution
Gipsh, L. A.↗
On the utilization of a flexible bar as a spatial filter
Flexible bar as spatial filter for measuring wave number-frequency spectra of distributed random processes
Aupperle, F. A.↗
Prediction of directional reflectance of a corn field under stress
A vegetative canopy model concept is developed and used to calculate the directional spectral reflectance of a corn field under stress. The problem has been idealized by assuming that the canopy is represented in several layers of uniform but randomly distributed biological components; horizontal and vertical projection of leaves, for example, replaces the actual leaf. An accumulative horizontal projection leads to a quantitative horizontal leaf area index while accumulated vertical projections provide the vertical leaf index area for each layer. The spectral properties of the projections are obtained from the spectral properties of the biological components. These techniques together with soil reflectance data provide a physical description for the vegetative canopy and adequately interprete multispectral scanning data.
Suits, G. H.↗
The earth and the moon /Harold Jeffreys Lecture/.
The internal structures of the earth and the moon are compared in the light of the latest extensive data on the earth structure, mobility of the earth outer layers, and the properties of lunar crust. The Monte Carlo method is applied to develop an earth model by a stepwise process beginning with a random distribution of two elastic velocities and the density as a function of de pth. Lunar seismic, magnetic, and rock analysis data are used to infer the properties of the moon. The marked planetological contrast between the earth and the moon is shown to consist in that the earth is highly differentiated and still undergoes a large-scale differentiation, while the moon has lost its volatiles in its early history and has a cold dynamically inactive shell which has been without basic changes for three billion years.
Press, F.↗
Programmable random interval generator
Random pulse generator can supply constant-amplitude randomly distributed pulses with average rate ranging from a few counts per second to more than one million counts per second. Generator requires no high-voltage power supply or any special thermal cooling apparatus. Device is uniquely versatile and provides wide dynamic range of operation.
Lindsey, R. S., Jr.↗
On the role of the radiation directivity in noise reduction for STOL aircraft.
The radiation characteristics of distributed randomly fluctuating acoustic sources when shielded by finite surfaces are discussed briefly. A number of model tests using loudspeakers as artificial noise sources with a given broadband power density spectrum are used to demonstrate the effectiveness of reducing the radiated noise intensity in certain directions due to shielding. In the lateral direction of the source array noise reductions of 12 dB are observed with relatively small shields. The same shields reduce the backward radiation by approximately 20 dB. With the results obtained in these acoustic model tests the potentials of jet noise reduction of jet flap propulsion systems applicable in future STOL aircraft are discussed. The jet flap configuration as a complex aerodynamic noise source is described briefly.
Gruschka, H. D.↗
X-ray observations of characteristic structures and time variations from the solar corona - Preliminary results from Skylab.
Examples taken from the S-054 X-ray telescope observations made during the first Skylab mission show the hot coronal plasma tracing the configuration of the magnetic fields. The high spectral resolution and sensitivity of the instrument has enabled the following two facts to be more firmly established: (1) that the 'quiet homogeneous corona' is in fact highly structured and that the structures observed appear to be the results of dispersed active region magnetic fields; and (2) that numerous bright points are distributed randomly on the disk. Their presence at high latitudes may play a role in solar cycle models. In addition, the capability of Skylab for studying time evolution has enabled the restructuring of coronal features to be seen at times of high activity, indicating a restructuring of the coronal magnetic fields.
Vaiana, G. S.↗
Viking orbiter 1975 articulation control actuators
The articulation subsystem actuators were rigorously tested in severe environments. They were operated through temperature ranges from -73 C to +121 C. In each case the temperature rate of change was at maximum. The actuator under test at room temperature was put into a pre-chilled or preheated chamber. Satisfactory performance was obtained throughout this full temperature range and under the temperature shock conditions above. However, at temperatures below -78 C some leakage was experienced through the O-ring seal around the shaft. The actuators were subjected to severe vibration and 500 g shock test with a time duration of 0.0007 seconds. The scan actuator was life tested by operating it from stop to stop through 2,000 cycles with 20,000 start-stop procedures randomly distributed through the 2,000 cycles.
Perkins, G. S.↗
Dual frequency scatterometer measurement of ocean wave height
A technique for remotely measuring wave height averaged over an area of the sea surface was developed and verified with a series of aircraft flight experiments. The measurement concept involves the cross correlation of the amplitude fluctuations of two monochromatic reflected signals with variable frequency separation. The signal reflected by the randomly distributed specular points on the surface is observed in the backscatter direction at nadir incidence angle. The measured correlation coefficient is equal to the square of the magnitude of the characteristic function of the specular point height from which RMS wave height can be determined. The flight scatterometer operates at 13.9 GHz and 13.9 - delta f GHz with a maximum delta f of 40 MHz. Measurements were conducted for low and moderate sea states at altitudes of 2, 5, and 10 thousand feet. The experimental results agree with the predicted decorrelation with frequency separation and with off-nadir incidence angle.
Johnson, J. W.↗
A dual frequency radar for ocean roughness sampling
A microwave technique for determining the roughness (rms wave height) of a randomly varying air-water interface has been developed theoretically, verified with laboratory wavetank studies and is currently being implemented for ocean surface measurements in a series of applications flight experiments. These aircraft observations will be near the Chesapeake Light Tower and will include a range of altitudes and sea conditions. The measurement concept involves cross-correlating the envelope fluctuations on two received carriers that are monochromatic when transmitted in a normal direction to the interface and are observed in a backscatter direction after reflection by the large number of randomly distributed specular points on the surface. The measured correlation coefficient (normalized covariance) as a function of carrier frequency separation will depend on the surface roughness, specifically the probability density function of the specular point height. Details of the flight system are discussed, and preliminary flight results are presented.
Weissman, D. E.↗
Particles from comet Kohoutek detected by the micrometeoroid experiment on HEOS 2
HEOS B measurements on particles ejected from comet Kohoutek reflect average particle rate as a function of particle speed and mass in relation to random distribution with known speed from the interplanetary region. The micrometeoroid experiment detector onboard the satellite passed through the orbital plane of the comet and encountered ejected particles for approximately two months.
Hoffmann, H. J.↗
Large-scale kinetic energy spectra from Eulerian analysis of EOLE wind data
A data set of 56,000 winds determined from the horizontal displacements of EOLE balloons at the 200 mb level in the Southern Hemisphere during the period October 1971-February 1972 is utilized for the computation of planetary- and synoptic-scale kinetic energy space spectra. However, the random distribution of measurements in space and time presents some problems for the spectral analysis. Two different approaches are used, i.e., a harmonic analysis of daily wind values at equi-distant points obtained by space-time interpolation of the data, and a correlation method using the direct measurements. Both methods give similar results for small wavenumbers, but the second is more accurate for higher wavenumbers (k above or equal to 10). The spectra show a maximum at wavenumbers 5 and 6 due to baroclinic instability and then decrease for high wavenumbers up to wavenumber 35 (which is the limit of the analysis), according to the inverse power law k to the negative p, with p close to 3.
Desbois, M.↗
Mafic silicates in the Orgueil carbonaceous meteorite
Iron-bearing olivines and pyroxenes occurring in Orgueil may represent a separate population distinct from the magnesian varieties previously reported. Compositions of these iron-bearing silicates are inconsistent with an origin by direct equilibrium condensation in the nebula. Such an origin is more plausible for the magnesian silicates, but lacks conclusive evidence. An extra-solar system origin for either mafic population is possible, though similarly lacking in evidence. About 15% of the olivines, randomly distributed with respect to iron content, retain particle track evidence of a precompaction irradiation.
Kerridge, J. F.↗
Effective defect density for MOS breakdown - Dependence on oxide thickness
A new procedure for measuring effective defect density takes time-dependent primary dielectric breakdown in MOS devices into account. A time-varying breakdown probability is obtained by applying a constant field stress to a statistically sufficient number of MOS capacitors. Effective defects are assumed distributed randomly in two dimensions, hence indistinguishable. The effective defect density is found to vary with oxide thickness; tentative explanations are ventured to account for this (interfacial tensile stress, ion patching enhanced by local trapping, breakdown in the form of filamentary discharges with release of stored electrostatic energy).
Li, S. P.↗
A note on the consistency of maximum likelihood estimates for finite families of stochastic processes
The note considers families of stochastic processes indexed by a finite number of alternative parameter values. For general classes of stochastic processes, it is shown that maximum-likelihood estimates converge almost surely to the correct parameter value. This is established by use of a submartingale property of the sequence of maximized-likelihood ratios together with a technique first employed by Wald (1949) in the case of independent identically distributed random variables.
Caines, P. E.↗
Detectability of auditory signals presented without defined observation intervals
Ability to detect tones in noise was measured without defined observation intervals. Latency density functions were estimated for the first response following a signal and, separately, for the first response following randomly distributed instances of background noise. Detection performance was measured by the maximum separation between the cumulative latency density functions for signal-plus-noise and for noise alone. Values of the index of detectability, estimated by this procedure, were approximately those obtained with a 2-dB weaker signal and defined observation intervals. Simulation of defined- and non-defined-interval tasks with an energy detector showed that this device performs very similarly to the human listener in both cases.
Watson, C. S.↗
Observations of Uranus occultation events
An analysis of photometric data obtained during the Uranus appulse to SAO 158687 shows three occultation events which appear to coincide with portions of the Uranian ring system. Two occultation events were associated with the alpha ring and one with the beta ring of the planet; the alpha ring event suggests a ring model with a random distribution of occulting bodies of about 1 km diameter, and an areal density of about 50% over a band 10 km wide. Calculations indicate that neither the inner nor outer rings of the planet are truly concentric circles (to within their radius). In addition, determination of the ring centers can be used to locate the center of mass of the planet, and an upper limit of 26,300 km can be assigned to its radius.
Hubbard, W. B.↗