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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Edge and line detection in ERTS imagery: A comparative study

Several local edge detection operators were applied to a set of ERTS pictures of the Monterey, Calif. area. Gradient operators performed consistently better than laplacian operators in detecting edges. It was also found that if a grayscale normalization operation, histogram flattening, was applied to the pictures first, the edge detector outputs were greatly enhanced. The use of interpolation for more accurate location of edges on a digital picture was also briefly investigated. Curve detection operators were applied to the edge detector outputs; this had the effect of enhancing the edges while suppressing noise.

Eberlein, R.↗
NASA NTRS1973

Structural analysis of vibroacoustical processes

The method of automatic identification of acoustical signals, by means of the segmentation was used to investigate noises and vibrations in machines and mechanisms, for cybernetic diagnostics. The structural analysis consists of presentation of a noise or vibroacoustical signal as a sequence of segments, determined by the time quantization, in which each segment is characterized by specific spectral characteristics. The structural spectrum is plotted as a histogram of the segments, also as a relation of the probability density of appearance of a segment to the segment type. It is assumed that the conditions of ergodic processes are maintained.

Gromov, A. P.↗
NASA NTRS1974

Correlation of hippocampal theta rhythm with changes in cutaneous temperature

A possible role for the hippocampus in alerting an animal to changes in cutaneous temperature was examined. Following local warming or cooling of the ears of unanesthetized, loosely restrained rabbits, theta waves (4-7 Hz EEG waves) were recorded from electrodes straddling the hippocampus. The onset of the hippocampal theta rhythm was correlated with changes in cutaneous temperature, an observation consistent with studies indicating that the theta rhythm is a nonspecific response evoked by stimulation of several sensory modalities. Additional data from cats and rabbits were correlated with specific neurons within the hippocampus, namely pyramidal cells. Post stimulus time histograms obtained by excitation of the dorsal fornix were interpreted in terms of excitatory and inhibitory inputs to pyramidal cells. Thus, the theta rhythm, which appears to be evoked by changes in cutaneous temperature, can be related to a specific type of hippocampal neuron which is in turn connected with other areas of the brain involved in temperature regulation.

Horowitz, J. M.↗
NASA NTRS1974

Results of X-ray and optical monitoring of SCO X-1

Sco X-1 was monitored at optical and X-ray wavelengths from 1970 April 26 to 1970 May 21. The optical observations were made at six observatories around the world and the X-ray observations were made by the Vela satellites. There was a tendency for the object to show greater variability in X-ray when the object is optically bright. A discussion of the intensity histograms is presented for both the optical and X-ray observations. No evidence for optical or X-ray periodicity was detected.

Mook, D. E.↗
NASA NTRS1974

An analysis of Jupiter data from the RAE-1 satellite

The analysis of Radio Astronomy Explorer Satellite data are presented. Radio bursts from Jupiter are reported in the frequency range 4700 KHz to 45 KHz. Strong correlations with lo were found at 4700, 3930, and 2200 KHz, while an equally strong Europa effect was observed at 1300, 900, and 700 KHz. Histograms indicating the relative probability and the successful identification of Jupiter activity were plotted, using automatic computer and visual search techniques.

Carr, T. D.↗
NASA NTRS1974

Program for the analysis of time series

A digital computer program for the Fourier analysis of discrete time data is described. The program was designed to handle multiple channels of digitized data on general purpose computer systems. It is written, primarily, in a version of FORTRAN 2 currently in use on CDC 6000 series computers. Some small portions are written in CDC COMPASS, an assembler level code. However, functional descriptions of these portions are provided so that the program may be adapted for use on any facility possessing a FORTRAN compiler and random-access capability. Properly formatted digital data are windowed and analyzed by means of a fast Fourier transform algorithm to generate the following functions: (1) auto and/or cross power spectra, (2) autocorrelations and/or cross correlations, (3) Fourier coefficients, (4) coherence functions, (5) transfer functions, and (6) histograms.

Brown, T. J.↗
NASA NTRS1973

A numerical study of rays in random media

Statistics of electromagnetic rays in a random medium are studied numerically by the Monte Carlo method. Two dimensional random surfaces with prescribed correlation functions are used to simulate the random media. Rays are then traced in these sample media. Statistics of the ray properties such as the ray positions and directions are computed. Histograms showing the distributions of the ray positions and directions at different points along the ray path as well as at given points in space are given. The numerical experiment is repeated for different cases corresponding to weakly and strongly random media with isotropic and anisotropic irregularities. Results are compared with those derived from theoretical investigations whenever possible.

Youakim, M. Y.↗
NASA NTRS1974

Cluster analysis based on dimensional information with applications to feature selection and classification

A new clustering algorithm is presented that is based on dimensional information. The algorithm includes an inherent feature selection criterion, which is discussed. Further, a heuristic method for choosing the proper number of intervals for a frequency distribution histogram, a feature necessary for the algorithm, is presented. The algorithm, although usable as a stand-alone clustering technique, is then utilized as a global approximator. Local clustering techniques and configuration of a global-local scheme are discussed, and finally the complete global-local and feature selector configuration is shown in application to a real-time adaptive classification scheme for the analysis of remote sensed multispectral scanner data.

Eigen, D. J.↗
NASA NTRS1974

Study of the redundancy of telemetry information of the Luna-9 and Luna-13 automatic lunar probes

Knowledge of the statistical characteristics of natural telemetry information is important for the development of principles and methods of reduction of redundancy of telemetry messages as well as planning of on-board information compression devices. An evaluation was made to determine these characteristics for the telemetry information of the Luna-9 and Luna-13 automatic lunar probe, to allow estimation of the redundancy of the information. Histograms as well as numerical characteristics were used.

Kantor, A. V.↗
NASA NTRS1974

Data compression

An approach to data compression is discussed in which the effect achieved by compression is evaluated by the closeness of the approach to the minimum possible volume. An attempt is made to systematize the known results on data compression. The review contains: description of methods of data compression based on statistical coding and information theory; application of methods of interpolation and extrapolation; a specific compression method (related to description of the histogram of a sample); some criteria of effectiveness and methods of service information representation; and discussion of models suggested for theoretical analysis.

Babkin, V. F.↗
NASA NTRS1974

Design data collection with Skylab/EREP microwave instrument S-193

The author has identified the following significant results. The Skylab S-193 radiometer/scatterometer collected thousands of measurements of scattering coefficient and brightness temperature over various parts of the United States during the summer of 1973 at angles of incidence between vertical and about 45 deg. These measurements have been combined to produce histograms of the response at each of several angles within this range, and to establish average scattering coefficient vs angle curves with 10% and 90% exceedance levels as well. The variation of the radiometeric measurements is primarily in the region from 255 K to 285 K, with very few measurements giving values down to and even below 200 K. The scattering coefficient varies, for the mean, from about 0 db at 1 deg off vertical to a low in the neighborhood of -10 db at 45 deg. The variability of the scattering coefficient measurements with this coarse resolution sensor is surprisingly small. The number of distinguishable levels is slightly more for the scatterometer than for the radiometer, but the amount of variation in brightness temperature caused by the physical temperature of the ground is enough so that the scatterometer can be used to distinguish significantly more meaningful levels than the radiometer.

Sobti, A.↗
NASA NTRS1974

Statistics of Ku-band microwave response of the United States with a satellite borne radiometer/scatterometer

The author has identified the following significant results. The Skylab S-193 radiometer/scatterometer collected thousands of measurements of scattering coefficient and brightness temperature over various parts of the United States during the summer of 1973 at angles of incidence between vertical and about 45 deg. These measurements have been combined to produce histograms of the response at each of several angles within this range, and to establish average scattering coefficient vs angle curves with 10% and 90% exceedance levels as well. The variation of the radiometric measurements is primarily in the region from 255 K to 285 K, with very few measurements giving higher values, but a significant, though small, number giving values down to and even below 200 K. The scattering coefficient varies, for the mean, from about 0 db at 1 deg off vertical to a low in the neighborhood of -10 db at 45 deg. The variability of the scattering coefficient measurements with this coarse resolution sensor is surprisingly small. The number of distinguishable levels is slightly more for the scatterometer than for the radiometer, but the amount of variation in brightness temperature caused by the physical temperature of the ground is enough so that the scatterometer can be used to distinguish significantly more meaningful levels than the radiometer.

Moore, R. K.↗
NASA NTRS1975

Study of recreational land and open space using Skylab imagery

The author has identified the following significant results. The data quality, production of photographic enlargements, and digital printout that displayed the Gratiot-Saginaw game area were assessed, using histogramming of each spectral channel. Results showed some dissimilarities in the ranges of data values for even and odd numbered SDO's in order to depict many of the major scene classes. Major cover types were identified and located on aerial photos and maps.

Sattinger, I. J.↗
NASA NTRS1975

Comparison of Skylab and Landsat Lineaments with Joint Orientations in Northcentral Pennsylvania

The author has identified the following significant results. The histogram peaks of lineaments mapped from Skylab photograph at a scale of 1:517,000 lie subparallel, within 20 deg, to major shale joints and coal cleats on part of the Allegheny Plateau. The Landsat lineament, mapped at 1:989,000 are biased by illumination and scan line directions. While there is an illumination bias in the Skylab photograph, its direction does not coincide with the main transverse lineament trend, thus providing an independent assessment of the illumination direction bias. The coincidence in direction regardless of scale of the linear features suggests a mechanical relationship between joints, fracture traces, and lineaments which is more consistent with a tensional model than a shear model of origin.

Mcmurtry, G. J.↗
NASA NTRS1975

Asteroids - Spectral reflectance and color characteristics

We present visible and near-infrared spectral reflectance curves for 35 asteroids, making a total sample of 67 including our previous work. Several previously unknown spectral types have been discovered. Absorption bands and other features, from which information about the surface composition of the asteroids can be derived, continue to appear. Sampling statistics suggest we have observed about half of the significantly different mineralogical assemblages present in the asteroid belt. There is a general, but imperfect, correlation between spectral type and semimajor axis, which is consistent with the hypothesis that meteorites are derived from the asteroid belt. The color-frequency histogram for the 67 objects is bimodal, probably associated with 'stony' objects and 'carbonaceous' objects. Hirayama family pairs usually show disparate spectral types. 19 Fortuna may show strikingly different photometric properties on opposite sides.

Mccord, T. B.↗
NASA NTRS1975

Variations in the solar wind stand-off distance at Mercury

The intrinsic dipole model of the magnetosphere of Mercury is combined with statistics on the solar wind dynamic pressure from Explorers 33 and 35 to obtain histograms of the solar wind stand-off distance for aphelion, perihelion and median distance of Mercury from the sun. The results show that even at perihelion the stand-off distance lies above the surface the great majority of the time. On rare occasions, direct impact of the solar wind onto the surface will occur.

Siscoe, G.↗
NASA NTRS1975

Results of X-ray and optical monitoring of Scorpius X-1 in 1970

Scorpius X-1 was monitored at optical and X-ray wavelengths from 1970 April 26 to 1970 May 20. The optical observations were made at six observatories around the world, and the X-ray observations were made by the Vela satellites. There was a tendency for the object to show greater variability in X-ray emission when the object was optically bright. The intensity histograms for both the optical and X-ray observations are discussed, as well as periodic variations in the optical intensity.

Mook, D. E.↗
NASA NTRS1974

U-Th-Pb systematics of some Apollo 17 lunar samples and implications for a lunar basin excavation chronology

U, Th, and Pb concentrations and lead isotopic compositions of selected Apollo 17 soil and rock samples are presented. Concordia treatments of U-Pb whole samples of Apollo 17 mare basalts and highland rocks probably reflect several early thermal events about 4.5 b.y. old more consistently than do U-Pb ages of samples collected at other lunar sites. We propose that all lunar U-Th-Pb data reflect a multistate U-Pb evolution history most easily understood as being related to a complex planetesimal bombardment history of the moon which apparently dominated lunar events from about 4.5 to about 3.9 b.y. ago. Semi-distinct events at about 4.0, about 4.2, and 4.4-4.5 b.y. are evident on whole-rock frequency versus Pb-207/Pb-206 age histograms. Each of these events may reflect multiple cratering episodes. For mare basalts, complete resetting of the source rock U-Pb systems owing to Pb loss relative to U was apparently often approached after a major planetesimal impact.

Nunes, P. D.↗