Approximate calculation of cumulative probability from a moment-generating function
Numerical method for calculating cumulative distribution of positive random variable
Helstrom, C. W.↗
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Results for “Distributed Generation”
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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The Onset of the Madden-Julian Oscillation Within an Aquaplanet Model
A series of numerical experiments using a two-level atmospheric general circulation model (AGCM) were performed for the purpose of investigating the coupling between sea surface temperature (SST) profile and the onset of the Madden-Julian Oscillation (MJO). The AGCM was modified to run as an aquaplane with all seasonal forcing removed. SST distributions based on the New Global Sea-Ice and Sea Surface Temperature (GISST) Data Set for 1903-1994 were generated then modified to vary the north-south gradient and tropical temperatures. It was found that the MJO signal did not depend on the SST temperature gradients but rather on the absolute temperature of the equatorial region, EOF analysis revealed that the SST distribution which generated the strongest MJO signal produced a periodic fluctuation in velocity potential at the 250 millibar level with a phase speed of 15 m/s, and a periodicity of 30 days which falls within the shortest limit of observed oscillations. This distribution also possessed the coolest equatorial SSTs which suggests that increased stability in the atmosphere favors the occurrence of organized MJO propagation.
Colon, Edward↗
Automated Planning and Scheduling for Planetary Rover Distributed Operations
Automated planning and Scheduling, including automated path planning, has been integrated with an Internet-based distributed operations system for planetary rover operations. The resulting prototype system enables faster generation of valid rover command sequences by a distributed planetary rover operations team. The Web Interface for Telescience (WITS) provides Internet-based distributed collaboration, the Automated Scheduling and Planning Environment (ASPEN) provides automated planning and scheduling, and an automated path planner provided path planning. The system was demonstrated on the Rocky 7 research rover at JPL.
Backes, Paul G.↗
Results of investigation of muon fluxes of superhigh energy cosmic rays with X-ray emulsion chambers
The overall data from the investigation of the cosmic ray muon flux in the range of zenith angles (0-90) deg within the energy range (3.5 to 5.0) TeV is presented. The exposure of large X-ray emulsion chambers underground was 1200 tons. year. The data were processe using the method which was applied in the experiment Pamir and differred from the earlier applied one. The obtained value of a slope power index of the differential energy spectrum of the global muon flux is =3.7 that corresponds to the slope of the pion generation differential spectrum, gamma sub PI = 2.75 + or - .04. The analysis of the muon zenith-angular distribution showed that the contribution of rapid generation muons in the total muon flux agree the best with the value .2% and less with .7% at a 90% reliability level.
Ivanenko, I. P.↗
Science data processing in the Mission to Planet Earth era
The data-processing systems developed to support NASA's Mission to Planet Earth (MPE) are described in an overview of the system architectures. The MPE program is discussed in terms of flight segments and data types to examine the required elements of the information systems. The data-processing segments are described for the Atmospheric Laboratory for Applications and Science, the Tropical Rainfall Measuring Mission, the Earth Observing System, and the Geostationary Earth Observatory. The data and information systems for the separate segments provide some redundant processing services. Distributed active archive centers are employed for each segment composed of three subelements: (1) a product-generation system, (2) a data archive and distribution system, and (3) an information management system. The data processing design for the MPE is expected to facilitate the understanding of the entire earth system on a global scale.
Goodman, H. M.↗
Computer simulation of the effects of a distributed array antenna on synthetic aperture radar images
The ARL:UT orbital SAR simulation has been upgraded to use three-dimensional antenna gain patterns. This report describes the modifications and presents quantitative image analyses of a simulation using antenna patterns generated from the modeling of a distributed array antenna.
Estes, J. M.↗
Peeking through the picket fence - What astrophysical surprises may be present in the 100-200 A region?
In anticipation of more sensitive EUV and FUV spectroscopic instruments, spectra are simulated including interstellar absorption of solarlike, RS CVn, and flare stars as folded through the instrument parameters of the EUVE, Lyman/FUSE Phase A, and a desirable next-generation spectrometer. Even the relatively insensitive EUVE spectrometer is able to detect sufficient spectral lines from many active binary and dMe stars to determine their coronal-emission-measure distributions. The Lyman/FUSE or next-generation spectrometers are needed to study solar-type stars or flaring stars with high time resolution. The high throughput and effective area of a nex-generation spectrometer is needed for Doppler imaging studies, stellar wind and downflow measurements, and high time and spectral resolution of stellar flares.
Linsky, Jeffrey L.↗
Statistical characterization of life drivers for a probabilistic design analysis
This paper discusses the issue of statistical characterization of life drivers for a probabilistic design analysis (PDA) approach to support the conventional deterministic structural design methods that are currently used. The probabilistic approach takes into consideration the modeling inadequacies and uncertainties in many design variables such as loads, environments, and material properties. The importance of the distributional assumption is motivated by illustrating an example where the results differ substantially due to the distribution selected. Different types of distributions are discussed and techniques for estimating the parameters are given. Given this information, procedures are outlined for selecting the appropriate distribution based on the particular type of variable (i.e., dimensional, performance) as well as the information that is available (i.e., test data, engineering analysis). Finally, techniques are given for generating random numbers from these selected distributions within the PDA process.
Fox, Eric P.↗
Some observations of the aerodynamics of a large MHD generator channel
Large MHD generator channel aerodynamics, discussing pressure distributions to stall and stagnation pressure loss
Luchuk, W.↗
Ionization instabilities in a continuous- electrode generator
Continuous electrode MHD generator ionization instabilities, measuring current distribution and transverse electric field
Evans, R. M.↗
Impeller blade design method for centrifugal compressors
The design of a centrifugal impeller with blades that are aerodynamically efficient, easy to manufacture, and mechanically sound is discussed. The blade design method described here satisfies the first two criteria and with a judicious choice of certain variables will also satisfy stress considerations. The blade shape is generated by specifying surface velocity distributions and consists of straight-line elements that connect points at hub and shroud. The method may be used to design radially elemented and backward-swept blades. The background, a brief account of the theory, and a sample design are described.
Jansen, W.↗
Digital computer programs for generating oblique orthographic projections and contour plots
User and programer documentation is presented for two programs for automatic plotting of digital data. One of the programs generates oblique orthographic projections of three-dimensional numerical models and the other program generates contour plots of data distributed in an arbitrary planar region. A general description of the computational algorithms, user instructions, and complete listings of the programs is given. Several plots are included to illustrate various program options, and a single example is described to facilitate learning the use of the programs.
Giles, G. L.↗
Distributed feedback acoustic surface wave oscillator
Using a simple model, the feasibility of applying the distributed feedback concept to the generation of acoustic surface waves is evaluated. It is shown that surface corrugation of the piezoelectric boundary in a semiconductor-piezoelectric surface acoustic wave amplifier could lead to self-sustained oscillations.
Elachi, C.↗
Vortex simulation of the pressure field of a jet
Fluctuations of the pressure field of a jet are simulated numerically by a flow model consisting of axisymmetric vortex rings with viscous cores submerged in an inviscid uniform stream. Vortex shedding time intervals, randomly created to imitate the time-history characteristics of the pressure signals of a jet, are generated based on a probability distribution of the intervals between successive pressure peaks obtained from experiments. It is found that, up to five diameters downstream of the jet exit, the characteristics of the pressure fluctuations and the most probable time intervals between experimental and numerical results show good qualitative agreements. The role played by the axisymmetric vortex model in pressure field as well as extensions of the model is also discussed.
Fung, Y. T.↗
Investigation of spatial misregistration effects in multispectral scanner data
The author has identified the following significant results. A model for estimating the expected proportion of multiclass pixels in a scene was generalized and extended to include misregistration effects. Another substantial effort was the development of a simulation model to generate signatures to represent the distributions of signals from misregistered multiclass pixels, based on single class signatures. Spatial misregistration causes an increase in the proportion of multiclass pixels in a scene and a decorrelation between signals in misregistered data channels. The multiclass pixel proportion estimation model indicated that this proportion is strongly dependent on the pixel perimeter and on the ratio of the total perimeter of the fields in the scene to the area of the scene. Test results indicated that expected values computed with this model were similar to empirical measurements made of this proportion in four LACIE data segments.
Nalepka, R. F.↗
On the formation and evolution of clumps of galaxies in an expanding universe
Results are derived for the development of phase-space clumps of mass points in a background spectrum of gravitational-potential fluctuations. The Vlasov equation and the pair correlation equation (in the weak coupling limit) are solved exactly in an Einstein-de Sitter cosmology, and the plasma-clumping theory is used to identify terms that yield important collective effects. Various astrophysical implications are discussed, including the formation of large-scale inhomogeneity and the enhanced generation of correlations in the distribution of galaxies.
Norman, C. A.↗
Combined strength and aeroelastic wing synthesis via constraint approximation
A numerical optimization program using constraint approximations for preliminary sizing of wing structural design parameters to satisfy simultaneous strength and aeroelastic requirements is described. The effects of wing flexibility on loads and flutter are included. The iterative procedure approximates wing internal load distributions and flutter response in generating design constraints. Though a linear Taylor series approximation to the variation of flutter speed is made, constraints in general are formulated as nonlinear and solved in a minimum weight problem using a feasible directions search. The technique is demonstrated for the determination of the optimal ply orientations and for simultaneous sizing for strength and flutter with simple constraint approximations.
Mullen, J., Jr.↗
How thick are lunar mare basalts
It is argued that De Hon's estimates of the thickness of lunar mare basalts, made by analyzing 'ghost' craters on mare surfaces, were inflated as the result of the crater morphometric data of Pike (1977) to reconstruct rim heights of degraded craters. Crater rim heights of 82 randomly selected highland craters of various states of degradation were determined, and median rim height was compared to that of corresponding fresh impact structures. Results indicate that the thickness estimates of De Hon may be reduced by a factor of 2, and that the total volume of mare basalt produced throughout lunar history could be as little as 1-2 million cubic kilometers. A survey of geochemical and petrographic evidence indicates that lateral transport of regolith components over distances of much greater than 10 km is relatively inefficient; it is suggested that vertical mixing of a highland substrate underlying the basaltic fill may have had a primordial role in generating the observed mare width distributions and high concentrations of exotic components in intrabasin regoliths.
Hoerz, F.↗