11,541 research outputs found
Structural geologic interpretation from radar imagery
Structural geologic interpretations from side- looking radar photograph
Two-dimensiosnal electron beam charging model for polymer films
A two dimensional model was developed to describe the charging of thin polymer films exposed to a uniform mon-energetic electron beam. The study was motivated by observed anomalous behavior of geosynchronous satellites which was attributed to electrical discharges associated with the differential charging of satellite surfaces of magnetospheric electrons. Electric fields both internal and external to the irradiated specimen were calculated at steady state in order to identify regions of high electrical stress. Particular emphasis was placed on evaluating the charging characteristics near the material's edge. The model was used to identify and quantify the effects of some of the experimental parameters notably: beam energy; beam angle of incidence; beam current density; material thickness; and material width. Simulations of the following situations were also conducted: positive or negative precharging over part of the surface; a central gap in the material; and a discontinuity in the material's thickness
NASA/ESA CV-990 Spacelab Simulation (ASSESS 2)
To test the validity of the ARC approach to Spacelab, several missions simulating aspects of Spacelab operations have been conducted as part of the ASSESS Program. Each mission was designed to evaluate potential Shuttle/Spacelab concepts in increasing detail. For this mission, emphasis was placed on development and exercise of management techniques planned for Spacelab using management participants from NASA and ESA who have responsibilities for Spacelab 1 which will be launched in 1980
Applications of remote sensor data to geologic and economic analysis on the Bonanza Test Site, Colorado
Recent studies conducted in the Bonanza Test Site, Colorado, area indicated that: (1) more geologic structural information is available from remote sensing data than from conventional techniques; (2) greater accuracy results from using remote sensing data; (3) all major structural features were detected; (4) of all structural interpretations, about 75% were correct; and (5) interpretation of remote sensing data will not supplant field work, but it enables field work to be done much more efficiently
Development and application of a non-Gaussian atmospheric turbulence model for use in flight simulators
A method is described for generating time histories which model the frequency content and certain non-Gaussian probability characteristics of atmospheric turbulence including the large gusts and patchy nature of turbulence. Methods for time histories using either analog or digital computation are described. A STOL airplane was programmed into a 6-degree-of-freedom flight simulator, and turbulence time histories from several atmospheric turbulence models were introduced. The pilots' reactions are described
A simultaneous XMM-Newton and BeppoSAX observation of the archetypal Broad Line Seyfert 1 galaxy NGC 5548
We report the spectral analysis of a long XMM-Newton observation of the
well-studied, moderate luminosity Broad Line Seyfert 1 galaxy NGC 5548. The
source was at an historically average brightness and we find the hard (3-10
keV) spectrum can be well fitted by a power law of photon index gamma ~ 1.75,
together with reflection. The only feature in the hard X-ray spectrum is a
narrow emission line near 6.4 keV, with an equivalent width of ~ 60 eV. The
energy and strength of this line is consistent with fluorescence from `neutral'
iron distant from the central continuum source. We find no evidence for a broad
Fe K line, with an upper limit well below previous reports, suggesting the
inner accretion disc is now absent or highly ionised. The addition of
simultaneous BeppoSAX data allows the analysis to be extended to 200 keV,
yielding important constraints on the total reflection. Extrapolation of the
hard X-ray power law down to 0.3 keV shows a clear `soft excess' below ~ 0.7
keV. After due allowance for the effects of a complex warm absorber, measured
with the XMM-Newton RGS, we find the soft excess is better described as a
smooth upward curvature in the continuum flux below ~ 2 keV. The soft excess
can be modelled either by Comptonised thermal emission or by enhanced
reflection from the surface of a highly ionised disc.Comment: 9 pages, 11 figures, accepted by MNRAS; minor changes to text and
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A changing inner radius in the accretion disc of Q0056-363?
Q0056-363 is the most powerful X-ray quasar known to exhibit a broad, likely
relativistic iron line (Porquet & Reeves 2003). It has been observed twice by
XMM-, three and half years apart (July 2000 and December 2003). In the
second observation, the UV and soft X-ray fluxes were fainter, the hard X-ray
power law flatter, and the iron line equivalent width (EW) smaller than in the
2000 observation. These variations can all be explained, at least
qualitatively, if the disc is truncated in the second observation. We report
also on the possible detection of a transient, redshifted iron absorption line
during the 2003 observation.Comment: Accepted for publication in A&
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