6,704 research outputs found

    Modeling the near-UV band of GK stars, Paper II: NLTE models

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    We present a grid of atmospheric models and synthetic spectral energy distributions (SEDs) for late-type dwarfs and giants of solar and 1/3 solar metallicity with many opacity sources computed in self-consistent Non-Local Thermodynamic Equilibrium (NLTE), and compare them to the LTE grid of Short & Hauschildt (2010) (Paper I). We describe, for the first time, how the NLTE treatment affects the thermal equilibrium of the atmospheric structure (T(tau) relation) and the SED as a finely sampled function of Teff, log g, and [A/H] among solar metallicity and mildly metal poor red giants. We compare the computed SEDs to the library of observed spectrophotometry described in Paper I across the entire visible band, and in the blue and red regions of the spectrum separately. We find that for the giants of both metallicities, the NLTE models yield best fit Teff values that are ~30 to 90 K lower than those provided by LTE models, while providing greater consistency between \log g values, and, for Arcturus, Teff values, fitted separately to the blue and red spectral regions. There is marginal evidence that NLTE models give more consistent best fit Teff values between the red and blue bands for earlier spectral classes among the solar metallicity GK giants than they do for the later classes, but no model fits the blue band spectrum well for any class. For the two dwarf spectral classes that we are able to study, the effect of NLTE on derived parameters is less significant.Comment: Submitted to The Astrophysical Journal. Observed spectrophotometric library, and grids of NLTE and LTE) synthetic spectra for GK stars available at http://www.ap.smu.ca/~ishort/PHOENI

    Analysis of multispectral images simulating ERTS observations

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    Simulation studies of selected aircraft and spacecraft acquired images were initiated in response to anticipated desires of the user community for simulated imagery prior to launch of ERTS-A. Principal modes of simulation included: (1) areas of coverage comparable to ERTS; (2) spatial resolutions within these images similar to ERTS; (3) spectral responses analogous to that expected from each channel on both the return beam vidicon and multispectral scanner, leading to production of photographic images that should appear similar to those representing each band in the two sensors; and (4) runthroughs of several analytical techniques, such as color density slicing, color additive viewing, and computer-generated reflectance and surface temperature maps, by which ERTS data can be analyzed, interpreted, and applied. The two areas involved in the simulation study were Wyoming and the Chesapeake Bay region

    Aspects of Heart Disease in Old Age with Special Reference to Hypertension

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    The development of a prototype intelligent user interface subsystem for NASA's scientific database systems

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    The National Space Science Data Center (NSSDC) has initiated an Intelligent Data Management (IDM) research effort which has as one of its components the development of an Intelligent User Interface (IUI).The intent of the latter is to develop a friendly and intelligent user interface service that is based on expert systems and natural language processing technologies. The purpose is to support the large number of potential scientific and engineering users presently having need of space and land related research and technical data but who have little or no experience in query languages or understanding of the information content or architecture of the databases involved. This technical memorandum presents prototype Intelligent User Interface Subsystem (IUIS) using the Crustal Dynamics Project Database as a test bed for the implementation of the CRUDDES (Crustal Dynamics Expert System). The knowledge base has more than 200 rules and represents a single application view and the architectural view. Operational performance using CRUDDES has allowed nondatabase users to obtain useful information from the database previously accessible only to an expert database user or the database designer
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