Search Results - (Author, Cooperation:J. Oberst)
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1Latest Papers from Table of Contents or Articles in PressD. T. Blewett ; N. L. Chabot ; B. W. Denevi ; C. M. Ernst ; J. W. Head ; N. R. Izenberg ; S. L. Murchie ; S. C. Solomon ; L. R. Nittler ; T. J. McCoy ; Z. Xiao ; D. M. Baker ; C. I. Fassett ; S. E. Braden ; J. Oberst ; F. Scholten ; F. Preusker ; D. M. Hurwitz
American Association for the Advancement of Science (AAAS)
Published 2011Staff ViewPublication Date: 2011-10-01Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Latest Papers from Table of Contents or Articles in PressJ. W. Head ; C. R. Chapman ; R. G. Strom ; C. I. Fassett ; B. W. Denevi ; D. T. Blewett ; C. M. Ernst ; T. R. Watters ; S. C. Solomon ; S. L. Murchie ; L. M. Prockter ; N. L. Chabot ; J. J. Gillis-Davis ; J. L. Whitten ; T. A. Goudge ; D. M. Baker ; D. M. Hurwitz ; L. R. Ostrach ; Z. Xiao ; W. J. Merline ; L. Kerber ; J. L. Dickson ; J. Oberst ; P. K. Byrne ; C. Klimczak ; L. R. Nittler
American Association for the Advancement of Science (AAAS)
Published 2011Staff ViewPublication Date: 2011-10-01Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
3Latest Papers from Table of Contents or Articles in PressM. T. Zuber ; D. E. Smith ; R. J. Phillips ; S. C. Solomon ; G. A. Neumann ; S. A. Hauck, 2nd ; S. J. Peale ; O. S. Barnouin ; J. W. Head ; C. L. Johnson ; F. G. Lemoine ; E. Mazarico ; X. Sun ; M. H. Torrence ; A. M. Freed ; C. Klimczak ; J. L. Margot ; J. Oberst ; M. E. Perry ; R. L. McNutt, Jr. ; J. A. Balcerski ; N. Michel ; M. J. Talpe ; D. Yang
American Association for the Advancement of Science (AAAS)
Published 2012Staff ViewPublication Date: 2012-03-23Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
4Articles: DFG German National LicensesStaff View
ISSN: 0012-821XSource: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: GeosciencesPhysicsType of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesStaff View
ISSN: 0019-1035Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: PhysicsType of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesBerger, M. ; Brück, D. ; Fischer, M. ; Langenberg, K. J. ; Oberst, J. ; Schmitz, V.
Springer
Published 1981Staff ViewISSN: 1573-4862Keywords: Holographic reconstruction ; ultrasound ; NDE ; Rayleigh-Sommerfeld formulaSource: Springer Online Journal Archives 1860-2000Topics: Electrical Engineering, Measurement and Control TechnologyMathematicsNotes: Abstract For the purpose of ultrasonic nondestructive testing of materials, holography in connection with digital reconstruction algorithms has been proposed as a modern tool to extract crack sizes from ultrasonic scattering data. Defining the typical holographic reconstruction algorithm as the application of the scalar Kirchhoff diffraction theory to backward wave propagation, we demonstrate its general incapability of reconstructing equivalent sources, and hence, geometries of scattering bodies. Only the special case of a planar measurement recording surface, that is to say, a hologram plane, and a planar crack with perfectly rigid boundary conditions parallel to the hologram plane and perpendicular to the incident field yields a nearly perfect correlation between crack size and reconstructed image; the reconstruction algorithm is then referred to as the Rayleigh-Sommerfeld formula; it therefore represents the optimal case matched to that special geometrical situation and, hence, may be interpreted as a quasi-matched spatial filter. Using integral equation theory and physical optics, we compute synthetic holographic data for a linear cracklike scatterer for both plane and spherical wave incidence, the latter case simulating a synthetic aperture impulse echo situation, thus illustrating how the Rayleigh-Sommerfeld algorithm or its Fresnel approximation increasingly fail for cracks inclined to the hologram plane and excited nonperpendicularly. Furthermore, we point out how the physical data recording process may additionally influence the reconstruction accuracy, and, finally, guidelines for a careful and serious application of these holographic reconstruction algorithms are given. The theoretical results are supported by measurements.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesBoice, D. C. ; Soderblom, L. A. ; Britt, D. T. ; Brown, R. H. ; Sandel, B. R. ; Yelle, R. V. ; Buratti, B. J. ; Hicks ; Nelson ; Rayman ; Oberst, J. ; Thomas, N.
Springer
Published 2000Staff ViewISSN: 1573-0794Keywords: Coma ; comets ; Deep Space 1 ; nucleus ; spacecraft explorationSource: Springer Online Journal Archives 1860-2000Topics: GeosciencesPhysicsNotes: Abstract NASA's Deep Space 1 (DS1) spacecraft successfully encountered comet 19P/Borrelly near perihelion and the Miniature Integrated Camera and Spectrometer (MICAS) imaging system onboard DS1 returned the first high-resolution images of a Jupiter-family comet nucleus and surrounding environment. The images span solar phase angles from 88° to 52°, providing stereoscopic coverage of the dust coma and nucleus. Numerous surface features are revealed on the 8-km long nucleus in the highest resolution images(47–58 m pixel). A smooth, broad basin containing brighter regions and mesa-likestructures is present in the central part of the nucleus that seems to be the source ofjet-like dust features seen in the coma. High ridges seen along the jagged terminator lead to rugged terrain on both ends of the nucleus containing dark patches and smaller series of parallel grooves. No evidence of impact craters with diameters larger thanabout 200-m are present, indicating a young and active surface. The nucleus is very dark with albedo variations from 0.007 to 0.035. Short-wavelength, infrared spectra from 1.3 to 2.6 μm revealed a hot, dry surface consistent with less than about10% actively sublimating. Two types of dust features are seen: broad fans and highlycollimated “jets” in the sunward hemisphere that can be traced to the surface. The source region of the main jet feature, which resolved into at least three smaller “jets” near the surface, is consistent with an area around the rotation pole that is constantly illuminated by the sun during the encounter. Within a few nuclear radii, entrained dustis rapidly accelerated and fragmented and geometrical effects caused from extended source regions are present, as evidenced in radial intensity profiles centered on the jet features that show an increase in source strength with increasing cometocentric distance. Asymmetries in the dust from dayside to nightside are pronounced and may show evidence of lateral flow transporting dust to structures observed in the nightside coma. A summary of the initial results of the Deep Space 1 Mission is provided, highlighting the new knowledge that has been gained thus far.Type of Medium: Electronic ResourceURL: