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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Pattern recognition for Space Applications Center director's discretionary fund

Results and conclusions are presented on the application of recent developments in pattern recognition to spacecraft star mapping systems. Sensor data for two representative starfields are processed by an adaptive shape-seeking version of the Fc-V algorithm with good results. Cluster validity measures are evaluated, but not found especially useful to this application. Recommendations are given two system configurations worthy of additional study,

Singley, M. E.↗
NASA NTRS1984

Fundamental remote science research program. Part 2: Status report of the mathematical pattern recognition and image analysis project

The Mathematical Pattern Recognition and Image Analysis (MPRIA) Project is concerned with basic research problems related to the study of he Earth from remotely sensed measurements of its surface characteristics. The program goal is to better understand how to analyze the digital image that represents the spatial, spectral, and temporal arrangement of these measurements for purposing of making selected inferences about the Earth. This report summarizes the progress that has been made toward this program goal by each of the principal investigators in the MPRIA Program.

Heydorn, R. P.↗
NASA NTRS1984

An experimental and theoretical investigation of deposition patterns from an agricultural airplane

A flight test program has been conducted with a representative agricultural airplane to provide data for validating a computer program model which predicts aerially applied particle deposition. Test procedures and the data from this test are presented and discussed. The computer program features are summarized, and comparisons of predicted and measured particle deposition are presented. Applications of the computer program for spray pattern improvement are illustrated.

Morris, D. J.↗
NASA NTRS1983

Dynamics of interfacial pattern formation

A phenomenological model of dendritic solidification incorporating interfacial kinetics, crystalline anisotropy, and a local approximation for the dynamics of the thermal diffusion field is proposed. The preliminary results are in qualitative agreement with natural dendrite-like pattern formation.

Ben-Jacob, E.↗
NASA NTRS1984

Lightning attachment patterns and flight conditions experienced by the NASA F-106B airplane from 1980 to 1983

The direct lightning strike data and associated flight conditions recorded from 1980 to 1983 during 742 thunderstorm penetrations with a NASA F-106B in Oklahoma and Virginia are studied with an emphasis on aircraft protection design. The individual lightning attachment spots were plotted on isometric projections of the aircraft to identify lightning entry and exit points and swept flash patterns. The altitudes, ambient temperatures, turbulence, and precipitation at which the strikes occurred are summarized and discussed. It was noted that peak strike rates (0.81 strikes/min and 3 strikes/penetration) occurred at altitudes between 11 km and 11.6 km corresponding to ambient temperatures between -40 C and -45 C. The data confirmed that initial entry and exit points most frequently occur at aircraft extremities, in this case the nose boom, the wing tips, the vertical fin cap, and the afterburner. The swept-flash attachment paths and burn marks found in this program indicate that the mid-span areas of swept aircraft may be more susceptible to lightning than previously thought. It was also found that lightning strikes may attach to spots within the engine tail pipe.

Fisher, B. D.↗
NASA NTRS1983

Ship motion pattern directed VTOL letdown guidance

This paper examines ship motion pattern directed letdown guidance strategies for landing a VTOL aircraft onboard a small aviation ship under adverse environmental conditions. Off-line computer simulation of the shipboard landing task is utilized for assessing the relative merits of the proposed guidance schemes. A sum of seventy sinusoids representation is used to model the ship motion time histories. The touchdown performance of a nonimal constant-rate-of-descent (CROD) letdown strategy serves as a benchmark for ranking the performance of the alternative letdown schemes.

Phatak, A. V.↗
NASA NTRS1984

Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns

Various flow visualization techniques were used to define the seondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious. Previously announced in STAR as N83-14435

Gaugler, R. E.↗
NASA NTRS1984

Cultural and environmental effects on crop spectral development patterns as viewed by Landsat

The typical patterns of spectral development (profiles) for corn and soybeans are presented, based on field-collected reflectance data transformed to correspond to Landsat-MSS Tasseled Cap coordinates. Reasonable variations in field conditions and cultural practices are shown to significantly influence profile features. The separability of the two crops is determined to be primarily related to the maximum value of the reflectance equivalent of Greenness, and to the plateau effect seen in corn Greenness profiles. The impact of changes in conditions on separability is described. In addition, association is made between profile features and stages of development for corn and soybeans. Corn is shown to peak at a stage well before tasseling or maximum LAI, while the characteristics of the soybean profile are shown to be unrelated to any particular stage of development.

Crist, E. P.↗
NASA NTRS1984

Fundamental remote sensing science research program. Part 1: Status report of the mathematical pattern recognition and image analysis project

The Mathematical Pattern Recognition and Image Analysis (MPRIA) Project is concerned with basic research problems related to the study of the Earth from remotely sensed measurement of its surface characteristics. The program goal is to better understand how to analyze the digital image that represents the spatial, spectral, and temporal arrangement of these measurements for purposing of making selected inference about the Earth.

Heydorn, R. D.↗
NASA NTRS1984

Patterns of behavior in lodgings exposed to traffic noise

Threshold values for public services interferent on the attenuation to noise nuisance were defined. Daily life at home was described and collected on the use of residences, the effects of noise on health and sleep, and the incidence of running away from home. A correlation was made with the equipment and noise insulation of homes. It is shown that there are behavior patterns in the modification of considerable manner in the way of life for people who live in apartments and in individual houses, above 66 dB during daytime.

Lambert, J.↗
NASA NTRS1985

Direct-strike lightning photographs, swept-flash attachment patterns, and flight conditions for storm hazards 1982

As part of the NASA Langley Research Center Storm Hazards Program, 241 thunderstorm penetrations were made in 1982 with an F-106B airplane in order to record direct-strike lightning data and the associated flight conditions. During these penetrations, the airplane received 156 direct lightning strikes; in addition, lightning transient data were recorded from 26 nearby lightning flashes. The tests were conducted within 150 nautical miles of Hampton, Virginia, assisted by ground-based weather-radar guidance from the NASA Wallops Flight Facility. The photographs of the lightning attachments taken from two onboard 16-mm color movie cameras and the associated strike attachment patterns are presented. A table of the flight conditions recorded at the time of each lightning event, and a table in which the data are cross-referenced with the previously published lightning electromagnetic waveform data are included.

Zaepfel, K. P.↗
NASA NTRS1985

Objective Determination of Heat Wave Patterns

A simple index was developed in order to objectively characterize a heat wave pattern in either analyses or forecasts of 500 mb height. 500 mb height was chosen because this parameter is usually among the most accurate fields predicted by numerical models. In addition, it is highly correlated with the surface air temperature on many time scales. The heat index IN is designed to be applied to any region of interest and to be used for any objectively analyzed data and specifically those of NWP models.

Wolfson, N.↗
NASA NTRS1985

Pattern selection in a boundary-layer model of dendritic growth in the presence of impurities

Presently analyzed, in the context of a boundary-layer model, is the problem of pattern selection in dendritic growth in a situation where impurities are present in the undercooled liquid. It is found that the tip-velocity selection criterion that has been proposed recently for the geometrical model and the boundary-layer model of a pure substance can be extended, in a nontrivial way, to this more complex situation where two coupled diffusion fields (temperature and solute) determine the interface dynamics. This model predicts a sharp enhancement of tip velocity in good qualitative agreement with experiment. This agreement is consistent with the conjecture that a solvability condition can be used to determine the operating point of the dendrite in the full nonlocal problem.

Karma, A.↗
NASA NTRS1984

Influence of clinostat rotation on fertilized amphibian egg pattern specification

Pattern specification in fertile Xenopus eggs rotated on horizontal clinostats was monitored with respect to primary embryonic axis formation, subsequent morphogenesis, and compartmentalization of the cytoplasm. At the speeds of 1 to 24 rpm (which are believed to simulate microgravity) a large percentage of eggs developed normal axial structures. Eggs clinostated at 12 rpm showed a randomization of dorsal/ventral polarity. The cytoplasmic compartments showed some clinostat effects but no abnormal mixing, disruption or dislocation of compartments. It is predicted that Xenopus eggs fertilized and allowed to develop in space will retain normal cytoplasmic density compartments, establish primary axes and undergo normal morphogenesis in space. Their dorsal/ventral polarity may not, however, be determined by the sperm entrance site (as is the case for 1 g eggs).

Neff, A. W.↗
NASA NTRS1985

Strategy for reflector pattern calculation: Let the computer do the work

Using high frequency approximations, the secondary pattern of a reflector antenna can be calculated by numerically evaluating a radiation integral I(u,v). In recent years, tremendous effort has been expended to reducing I(u,v) to Fourier integrals. These reduction schemes are invariably reflector geometry dependent. Hence, different analyses/computer software development must be carried out for different reflector shapes/boundaries. it is pointed out, that, as the computer power improves, these reduction schemes are no longer necessary. Comparable accuracy and computation time can be achieved by evaluating I(u,v) by a brute force FFT described in this note. Furthermore, there is virtually no restriction on the reflector geometry by using the brute force FFT.

Lam, P. T.↗
NASA NTRS1985

Global view of the upper level outflow patterns associated with tropical cyclone intensity changes during FGGE

The characteristics of the upper tropospheric outflow patterns which occur with tropical cyclone intensification and weakening over all of the global tropical cyclone basins during the year long period of the First GARP Global Experiment (FGGE) are discussed. By intensification is meant the change in the tropical cyclone's maximum wind or central pressure, not the change of the cyclone's outer 1 to 3 deg radius mean wind which we classify as cyclone strength. All the 80 tropical cyclones which existed during the FGGE year are studied. Two-hundred mb wind fields are derived from the analysis of the European Center for Medium Range Weather Forecasting (ECMWF) which makes extensive use of upper tropospheric satellite and aircraft winds. Corresponding satellite cloud pictures from the polar orbiting U.S. Defense Meteorological Satellite Program (DMSP) and other supplementary polar and geostationary satellite data are also used.

Chen, L.↗
NASA NTRS1985

Secondary pattern computation of an arbitrarily shaped main reflector

The secondary pattern of a perfectly conducting offset main reflector being illuminated by a point feed at an arbitrary location is studied. The method of analysis is based upon the application of the Fast Fourier Transform (FFT) to the aperture fields obtained using geometrical optics (GO) and geometrical theory of diffraction (GTD). Key features of the present work are (1) the reflector surface is completely arbitrary, (2) the incident field from the feed is most general with arbitrary polarization and location, and (3) the edge diffraction is calculated by either UAT or by UTD. Comparison of this technique for an offset parabolic reflector with the Jacobi-Bessel and Fourier-Bessel techniques shows good agreement. Near field, far field, and scan data of a large refelctor are presented.

Lee, S. W.↗