5,734 research outputs found

    Procedure for generating global atmospheric engine emissions data from future supersonic transport aircraft. The 1990 high speed civil transport studies

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    The input for global atmospheric chemistry models was generated for baseline High Speed Civil Transport (HSCT) configurations at Mach 1.6, 2.2, and 3.2. The input is supplied in the form of number of molecules of specific exhaust constituents injected into the atmosphere per year by latitude and by altitude (for 2-D codes). Seven exhaust constituents are currently supplied: NO, NO2, CO, CO2, H2O, SO2, and THC (Trace Hydrocarbons). An eighth input is also supplied, NO(x), the sum of NO and NO2. The number of molecules of a given constituent emitted per year is a function of the total fuel burned by a supersonic fleet and the emission index (EI) of the aircraft engine for the constituent in question. The EIs for an engine are supplied directly by the engine manufacturers. The annual fuel burn of a supersonic fleet is calculated from aircraft performance and economic criteria, both of which are strongly dependent on basic design parameters such as speed and range. The altitude and latitude distribution of the emission is determined based on 10 Intern. Air Transport Assoc. (IATA) regions chosen to define the worldwide route structure for future HSCT operations and the mission flight profiles

    Multi-community command and control systems in law enforcement: An introductory planning guide

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    A set of planning guidelines for multi-community command and control systems in law enforcement is presented. Essential characteristics and applications of these systems are outlined. Requirements analysis, system concept design, implementation planning, and performance and cost modeling are described and demonstrated with numerous examples. Program management techniques and joint powers agreements for multicommunity programs are discussed in detail. A description of a typical multi-community computer-aided dispatch system is appended

    Application of computer-aided dispatch in law enforcement: An introductory planning guide

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    A set of planning guidelines for the application of computer-aided dispatching (CAD) to law enforcement is presented. Some essential characteristics and applications of CAD are outlined; the results of a survey of systems in the operational or planning phases are summarized. Requirements analysis, system concept design, implementation planning, and performance and cost modeling are described and demonstrated with numerous examples. Detailed descriptions of typical law enforcement CAD systems, and a list of vendor sources, are given in appendixes

    A general inversion for end-member ratios in binary mixing systems

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    Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q11007, doi:10.1029/2005GC000975.Binary mixing is one of the most common models used to explain variations in geochemical data. When the data being modeled are ratios of elements or isotopes, the mixtures follow hyperbolic trends with curvatures that depend on a cross-term representing the relative concentrations of the elements or isotopes under consideration in the mixing components. The inverse problem of estimating mixing components is difficult because of the cross-term in the hyperbolic equation, which requires the use of nonlinear methods to estimate the mixing parameters, and because the end-member ratio values are intrinsically underdetermined unless the mixing proportions of the samples are known a priori, which is not generally the case. I use maximum likelihood methods to address these issues and derive a general inversion for binary mixing model parameters from ratio-ratio data. I apply the method to synthetic test data and a global compilation of 230Th/232Th versus 87Sr/86Sr data from oceanic basalts and find that the concentration ratio parameter is well-constrained by the inversion while the end-member ratio estimates are strongly dependent on the initial guesses used to start the iterative solver, reflecting the underdetermined nature of the end-member positions on the mixing hyperbola. Monte Carlo methods that randomly perturb the initial guesses can be used to improve error estimates, and goodness-of-fit statistics can be used to assess the performance of the mixing model for explaining data variance

    Hot Populations in M87 Globular Clusters

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    We have obtained HST/STIS far- and near-UV photometry of globular clusters in four fields in the gE galaxy M87. To a limit of m(FUV) = 25 we detect a total of 66 globular clusters (GCs) in common with the deep HST optical-band study of Kundu et al. (1999). Despite strong overlap in V- and I-band properties, the M87 GCs have UV/optical properties that are distinct from clusters in the Milky Way and in M31. M87 clusters, especially metal-poor ones, produce larger hot HB populations than do Milky Way analogues. Cluster mass is probably not a factor in these distinctions. The most metal-rich M87 GCs in our sample are near Z_sun and overlap the local E galaxy sample in estimated Mg_2 line indices. Nonetheless, the clusters produce much more UV light at a given Mg_2, being up to 1 mag bluer than any gE galaxy in (FUV-V) color. The M87 GCs do not appear to represent a transition between Milky Way-type clusters and E galaxies. The differences are in the correct sense if the clusters are significantly older than the E galaxies. Comparisons with Galactic open clusters indicate that the hot stars lie on the extreme horizontal branch, rather than being blue stragglers, and that the EHB becomes well populated for ages > 5 Gyr. We find that 43 of our UV detections have no optical-band counterparts. Most appear to be UV-bright background galaxies, seen through M87. Eleven NUV variable sources detected at only one epoch in the central field are probably classical novae. [Abridged]Comment: 70 pages, 25 figures (including 4 jpgs), 7 tables. To appear in AJ. Full resolution version available at http://www.astro.virginia.edu/~rwo/m87/m87-hotpops.pd

    Danish values, the foundation of the Folkeskole

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    We have imaged with Hubble Space Telescope WFC3/UVIS the central 2′7 × 2′7 region of the giant elliptical galaxy M87, using the ultraviolet filter F275W. In combination with archival ACS/WFC data taken through the F606W and F814W filters, covering the same field, we have constructed integrated-light UV-optical colors and magnitudes for 1460 objects, most of which are believed to be globular clusters (GCs) belonging to M87. The purpose was to ascertain whether the multiple-populations syndrome, ubiquitous among Galactic GCs, also exists among the M87 family of clusters. To achieve this goal, we sought those GCs with exceptionally blue UV-to-optical colors because helium-enriched sub-populations produce a horizontal-branch morphology that is well populated at high effective temperature. For comparison, integrated, synthetic UV-optical and purely optical colors and magnitudes have been constructed for 45 Galactic GCs, starting from individual-star photometry obtained with the same instruments and the same filters. We identify a small group of M87 clusters exhibiting a radial UV-optical color gradient, representing our best candidate GCs hosting multiple populations with extreme helium content. We also find that the central spatial distribution of the bluer GCs is flattened in a direction parallel to the jet, while the distribution of redder GCs is more spherical. We release to the astronomical community our photometric catalog in F275W, F606W, and F814W bands and the high-quality image stacks in the same bands

    Connecting the Milky Way potential profile to the orbital timescales and spatial structure of the Sagittarius Stream

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    Recent maps of the halo using RR Lyrae from Pan-STARRS1 have clearly depicted the spatial structure of the Sagittarius stream. These maps show the leading and trailing stream apocenters differ in galactocentric radius by a factor of two, and also resolve substructure in the stream at these apocenters. Here we present dynamical models that reproduce these features of the stream in simple Galactic potentials. We find that debris at the apocenters must be dynamically young, in the sense of being stripped off in the last two pericentric passages, while the Sagittarius dwarf is currently experiencing a third passage. The ratio of apocenters is sensitive to both dynamical friction and the outer slope of the Galactic rotation curve. These dependences can be understood with simple regularities connecting the apocentric radii, circular velocities, and orbital period of the progenitor. The effect of dynamical friction on the stream can be constrained using substructure within the leading apocenter. Our ensembles of models are not intended as statistically proper fits to the stream. Nevertheless, out of the range of models we consider, we consistently find the mass within 100 kpc to be ∼7×1011 M⊙\sim 7 \times 10^{11} \, M_{\odot}, with a nearly flat rotation curve between 50 and 100 kpc. This points to a more extended Galactic halo than assumed in some current models. As in previous work, we find prolate or triaxial halos ease agreement with the track of the leading stream. We display the behavior of our models in various observational spaces and characterize the substructure expected within the stream. In particular, the young trailing stream visible near trailing apocenter should exhibit a tight trend of velocity with distance separate from the older debris, and we suggest that this will serve as an especially useful probe of the outer Galactic potential.Comment: Submitted to MNRA

    Significance of low energy impact damage on modal parameters of composite beams by design of experiments

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    This paper presents an experimental study on the effects of multi-site damage on the vibration response of composite beams damaged by low energy impacts around the barely visible impact damage limit (BVID). The variation of the modal parameters with different levels of impact energy and density of damage is studied. Vibration tests have been carried out with both burst random and classical sine dwell excitations in order to compare that which of the methods among Polymax and Half Bandwidth Method is more suitable for damping estimation in the presence of damage. Design of experiments (DOE) performed on the experimental data show that natural frequency is a more sensitive parameter for damage detection than the damping ratio. It also highlighted energy of impact as the factor having a more significant effect on the modal parameters. Half Bandwidth Method is found to be unsuitable for damping estimation in the presence of damage

    The Extended Shapes of Galactic Satellites

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    We are exploring the extended stellar distributions of Galactic satellite galaxies and globular clusters. For seven objects studied thus far, the observed profile departs from a King function at large r, revealing a ``break population'' of stars. In our sample, the relative density of the ``break'' correlates to the inferred M/L of these objects. We discuss opposing hypotheses for this trend: (1) Higher M/L objects harbor more extended dark matter halos that support secondary, bound, stellar ``halos''. (2) The extended populations around dwarf spheroidals (and some clusters) consist of unbound, extratidal debris from their parent objects, which are undergoing various degrees of tidal disruption. In this scenario, higher M/L ratios reflect higher degrees of virial non-equilibrium in the parent objects, thus invalidating a precept underlying the use of core radial velocities to obtain masses.Comment: 8 pages, including 2 figures Yale Cosmology Workshop: The Shapes of Galaxies and Their Halo

    Dark cloud cores and gravitational decoupling from turbulent flows

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    We test the hypothesis that the starless cores may be gravitationally bound clouds supported largely by thermal pressure by comparing observed molecular line spectra to theoretical spectra produced by a simulation that includes hydrodynamics, radiative cooling, variable molecular abundance, and radiative transfer in a simple one-dimensional model. The results suggest that the starless cores can be divided into two categories: stable starless cores that are in approximate equilibrium and will not evolve to form protostars, and unstable pre-stellar cores that are proceeding toward gravitational collapse and the formation of protostars. The starless cores might be formed from the interstellar medium as objects at the lower end of the inertial cascade of interstellar turbulence. Additionally, we identify a thermal instability in the starless cores. Under par ticular conditions of density and mass, a core may be unstable to expansion if the density is just above the critical density for the collisional coupling of the gas and dust so that as the core expands the gas-dust coupling that cools the gas is reduced and the gas warms, further driving the expansion.Comment: Submitted to Ap
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