50,522 research outputs found

    High-altitude plume computer code development

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    The flowfield codes that have been developed to predict rocket motor plumes at high altitude were used to predict plume properties for the RCS motor which show reasonable agreement with experimental data. A systematic technique was established for the calculation of high altitude plumes. The communication of data between the computer codes was standardized. It is recommended that these outlined procedures be more completed, documented and updated as the plume methodology is applied to the varied problems of plume flow and plume impingement encountered by space station design and operation

    GRBlog: A Database for Gamma-Ray Bursts

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    GRBlog is an on-line database providing researchers with quick access to all information reported in the GCN Circulars. Users of the GRBlog web site (grad40.as.utexas.edu/grblog.php) can search the circulars and produce afterglow light curve plots, or compile data tables. The site also offers advanced search capabilities to aide in statistical studies or comparative research. Most of the GCNs have already been entered into the GRBlog database, with the remainder to follow shortly.Comment: 4 pages, 2 figures. Proceedings for the 2003 GRB Conference (Santa Fe, NM, 2003 Sep 8-12

    Amenability and co-amenability of algebraic quantum groups

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    We define concepts of amenability and co-amenability for algebraic quantum groups in the sense of A. Van Daele. We show that co-amenability of an algebraic quantum group always implies amenability of its dual. Various necessary and/or sufficient conditions for amenability or co-amenability are obtained. Co-amenability is shown to have interesting consequences for the modular theory in the case that the algebraic quantum group is of compact type.Comment: 25 pages, with some minor corrections, as to appear in the IJMM

    Numerical solutions of the one-dimensional nucleon-meson cascade equations

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    Numerical integration of meson-nucleon cascade equations for accelerator shielding calculation

    Firing squibs by low voltage capacitor discharge for spacecraft application

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    Low voltage capacitor discharge firing circuit to initiate hot bridgewire squibs for spacecraft application

    A stellar census of the nearby, young 32 Orionis group

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    The 32 Orionis group was discovered almost a decade ago and despite the fact that it represents the first northern, young (age ~ 25 Myr) stellar aggregate within 100 pc of the Sun (d≃93d \simeq 93 pc), a comprehensive survey for members and detailed characterisation of the group has yet to be performed. We present the first large-scale spectroscopic survey for new (predominantly M-type) members of the group after combining kinematic and photometric data to select candidates with Galactic space motion and positions in colour-magnitude space consistent with membership. We identify 30 new members, increasing the number of known 32 Ori group members by a factor of three and bringing the total number of identified members to 46, spanning spectral types B5 to L1. We also identify the lithium depletion boundary (LDB) of the group, i.e. the luminosity at which lithium remains unburnt in a coeval population. We estimate the age of the 32 Ori group independently using both isochronal fitting and LDB analyses and find it is essentially coeval with the {\beta} Pictoris moving group, with an age of 24±424\pm4 Myr. Finally, we have also searched for circumstellar disc hosts utilising the AllWISE catalogue. Although we find no evidence for warm, dusty discs, we identify several stars with excess emission in the WISE W4-band at 22 {\mu}m. Based on the limited number of W4 detections we estimate a debris disc fraction of 32−8+1232^{+12}_{-8} per cent for the 32 Ori group.Comment: Accepted for publication in MNRAS; 24 pages, 17 figures and 10 table

    Galaxies into the Dark Ages

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    We consider the capabilities of current and future large facilities operating at 2\,mm to 3\,mm wavelength to detect and image the [CII] 158\,μ\mum line from galaxies into the cosmic "dark ages" (z∼10z \sim 10 to 20). The [CII] line may prove to be a powerful tool in determining spectroscopic redshifts, and galaxy dynamics, for the first galaxies. We emphasize that the nature, and even existence, of such extreme redshift galaxies, remains at the frontier of open questions in galaxy formation. In 40\,hr, ALMA has the sensitivity to detect the integrated [CII] line emission from a moderate metallicity, active star-forming galaxy [ZA=0.2 Z⊙Z_A = 0.2\,Z_{\odot}; star formation rate (SFR) = 5\,M⊙M_\odot\,yr−1^{-1}], at z=10z = 10 at a significance of 6σ\sigma. The next-generation Very Large Array (ngVLA) will detect the integrated [CII] line emission from a Milky-Way like star formation rate galaxy (ZA=0.2 Z⊙Z_{A} = 0.2\,Z_{\odot}, SFR = 1\,M⊙M_\odot\,yr−1^{-1}), at z=15z = 15 at a significance of 6σ\sigma. Imaging simulations show that the ngVLA can determine rotation dynamics for active star-forming galaxies at z∼15z \sim 15, if they exist. Based on our very limited knowledge of the extreme redshift Universe, we calculate the count rate in blind, volumetric surveys for [CII] emission at z∼10z \sim 10 to 20. The detection rates in blind surveys will be slow (of order unity per 40\,hr pointing). However, the observations are well suited to commensal searches. We compare [CII] with the [OIII] 88μ\mum line, and other ancillary information in high zz galaxies that would aid these studies.Comment: 11pages, 8 figures, Accepted for the Astrophysical Journa
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