13,945 research outputs found
Occurrence, stratigraphic distribution and palaeoecology of Quaternary foraminifera from CRP-1
Multi-wavelength Signatures of Cosmic Rays in the Milky Way
Cosmic rays (CRs) propagate in the Milky Way and interact with the
interstellar medium and magnetic fields. These interactions produce emissions
that span the electromagnetic spectrum, and are an invaluable tool for
understanding the intensities and spectra of CRs in distant regions, far beyond
those probed by direct CR measurements. We present updates on the study of CR
properties by combining multi-frequency observations of the interstellar
emission and latest CR direct measurements with propagation models.Comment: 8 pages, 4 figures. Proceedings of the 35th International Cosmic Ray
Conference, ICRC201
Mass spectrometry in structural and stereochemical problems. Part 178 - The electron-impact promoted fragmentation of 1,2-cyclohexene oxide
Mass spectra of 1,2-cyclohexane oxide and three deuterium labeled analog
Comparison of phase-coherent and non-phase- coherent coded communications
Word-error probability versus signal-to-noise ratio evaluation for five communications system
Motion detection in astronomical and ice floe images
Two approaches are presented for establishing correspondence between small areas in pairs of successive images for motion detection. The first one, based on local correlation, is used on a pair of successive Voyager images of the Jupiter which differ mainly in locally variable translations. This algorithm is implemented on a sequential machine (VAX 780) as well as the Massively Parallel Processor (MPP). In the case of the sequential algorithm, the pixel correspondence or match is computed on a sparse grid of points using nonoverlapping windows (typically 11 x 11) by local correlations over a predetermined search area. The displacement of the corresponding pixels in the two images is called the disparities to cubic surfaces. The disparities at points where the error between the computed values and the surface values exceeds a particular threshold are replaced by the surface values. A bilinear interpolation is then used to estimate disparities at all other pixels between the grid points. When this algorithm was applied at the red spot in the Jupiter image, the rotating velocity field of the storm was determined. The second method of motion detection is applicable to pairs of images in which corresponding areas can experience considerable translation as well as rotation
Parallel algorithm for determining motion vectors in ice floe images by matching edge features
A parallel algorithm is described to determine motion vectors of ice floes using time sequences of images of the Arctic ocean obtained from the Synthetic Aperture Radar (SAR) instrument flown on-board the SEASAT spacecraft. Researchers describe a parallel algorithm which is implemented on the MPP for locating corresponding objects based on their translationally and rotationally invariant features. The algorithm first approximates the edges in the images by polygons or sets of connected straight-line segments. Each such edge structure is then reduced to a seed point. Associated with each seed point are the descriptions (lengths, orientations and sequence numbers) of the lines constituting the corresponding edge structure. A parallel matching algorithm is used to match packed arrays of such descriptions to identify corresponding seed points in the two images. The matching algorithm is designed such that fragmentation and merging of ice floes are taken into account by accepting partial matches. The technique has been demonstrated to work on synthetic test patterns and real image pairs from SEASAT in times ranging from .5 to 0.7 seconds for 128 x 128 images
Techniques for carrying out radiative transfer calculations for the Martian atmospheric dust
A description is given of the modification of a theory on the reflectance of particulate media so as to apply it to analysis of the infrared spectra obtained by the IRIS instrument on Mariner 9. With the aid of this theory and the optical constants of muscovite mica, quartz, andesite, anorthosite, diopside pyroxenite, and dunite, modeling calculations were made to refine previous estimates of the mineralogical composition of the Martian dust particles. These calculations suggest that a feldspar rich mixture is a very likely composition for the dust particles. The optical constants used for anorthosite and diopside pyroxenite were derived during this program from reflectance measurements. Those for the mica were derived from literature reflectance data. Finally, a computer program was written to invert the measured radiance data so as to obtain the absorption coefficient spectrum which should then be independent of the temperature profile and gaseous component effects
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