17,409 research outputs found

    Six-degree-of-freedom program to optimize simulated trajectories (6D POST). Volume 1: Formulation manual

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    The basic equations and models used in a computer program (6D POST) to optimize simulated trajectories with six degrees of freedom were documented. The 6D POST program was conceived as a direct extension of the program POST, which dealt with point masses, and considers the general motion of a rigid body with six degrees of freedom. It may be used to solve a wide variety of atmospheric flight mechanics and orbital transfer problems for powered or unpowered vehicles operating near a rotating oblate planet. Its principal features are: an easy to use NAMELIST type input procedure, an integrated set of Flight Control System (FCS) modules, and a general-purpose discrete parameter targeting and optimization capability. It was written in FORTRAN 4 for the CDC 6000 series computers

    The Spectral Energy Distribution of Fermi Bright Blazars

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    We have conducted a detailed investigation of the broadband spectral properties of the γ-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi γ-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/γ-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these γ-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log ν-log ν F _ν representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, α_(ro), and optical to X-ray, α_(ox), spectral slopes) and from the γ-ray spectral index. Our data show that the synchrotron peak frequency (ν^S _(peak)) is positioned between 10^(12.5) and 10^(14.5) Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10^(13) and 10^(17) Hz in featureless BL Lacertae objects. We find that the γ-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter γ-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum γ-ray sources, the correlation between ν ^S _(peak) and γ-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars

    Twisted K-theory and K-theory of bundle gerbes

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    In this note we introduce the notion of bundle gerbe K-theory and investigate the relation to twisted K-theory. We provide some examples. Possible applications of bundle gerbe K-theory to the classification of D-brane charges in non-trivial backgrounds are discussed.Comment: 29 pages, corrected typos, added references, included new section on twisted Chern character in non-torsion cas

    Concept design and alternate arrangements of orbiter mid-deck habitability features

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    The evaluations and recommendations for habitability features in the space shuttle orbiter mid-deck are summarized. The orbiter mission plans, the mid-deck dimensions and baseline arrangements along with crew compliments and typical activities were defined. Female and male anthropometric data based on zero-g operations were also defined. Evaluations of baseline and alternate feasible concepts provided several recommendations which are discussed

    Aircraft control system

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    An aircraft control system is described which is particularly suited to rotary wing aircraft. Longitudinal acceleration and course rate commands are derived from a manual control stick to control translational velocity of the aircraft along a flight path. In the collective channel the manual controls provide vertical velocity commands. In the yaw channel the manual controls provide sideslip or heading rate commands at high or low airspeeds, respectively. The control system permits pilots to fly along prescribed flight paths in a precise manner with relatively low work load

    Toward joint Medical Logistics 2010 and beyond: process innovation and redesign of Class VIII supply chain at a medical logistics company

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    The purpose of this thesis is to evaluate current Class VIII supply chain procedures at a U.S. Medical Logistics Company (Med Log Co), process map the "as is" baseline process and propose possible "to be" process redesign alternatives that will possibly improve efficiency and produce long-term cost savings. To perform this analysis, the 1st Med Log Co at Camp Pendleton, CA was chosen. The assessment of their "as is" process includes a historical background on medical logistics within the Department of Defense, a comprehensive material logistics literature review, site visits, personnel interviews, process mapping of the baseline "as is" process, and proposal of two redesign alternatives for the "to be" process. A comprehensive analysis was conducted using Thomas Davenport's Process Innovation Framework and quantitative measurements were obtained using the Knowledge-based Organizational Process Redesign (KOPeR) methodology to diagnosis existing pathologies. KOPeR measurements indicate that the 1st Med Log Co's existing "as is" process is a fragmented, mostly manual procurement process that can be innovated now using information technology as a process enabler. Our results indicate that by formally injecting the use of electronic mail and shared databases into the "as is" procurement process an immediate impact can be realized. Further efficiency and cost savings can be accomplished by coupling the injection of information technology with a web- based end-to-end procurement process that assigns a case manager to the "to be" process.http://www.archive.org/details/towardjointmedic00auguMajor, United States Marine CorpsLieutenant, United States NavyApproved for public release; distribution is unlimited

    Evolutionary calculations of phase separation in crystallizing white dwarf stars

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    We present an exploration of the significance of Carbon/Oxygen phase separation in white dwarf stars in the context of self-consistent evolutionary calculations. Because phase separation can potentially increase the calculated ages of the oldest white dwarfs, it can affect the age of the Galactic disk as derived from the downturn in the white dwarf luminosity function. We find that the largest possible increase in ages due to phase separation is 1.5 Gyr, with a most likely value of approximately 0.6 Gyr, depending on the parameters of our white dwarf models. The most important factors influencing the size of this delay are the total stellar mass, the initial composition profile, and the phase diagram assumed for crystallization. We find a maximum age delay in models with masses of 0.6 solar masses, which is near the peak in the observed white dwarf mass distribution. We find that varying the opacities (via the metallicity) has little effect on the calculated age delays. In the context of Galactic evolution, age estimates for the oldest Galactic globular clusters range from 11.5 to 16 Gyr, and depend on a variety of parameters. In addition, a 4 to 6 Gyr delay is expected between the formation of the globular clusters and that of the Galactic thin disk, while the observed white dwarf luminosity function gives an age estimate for the thin disk of 9.5 +/-1.0 Gyr, without including the effect of phase separation. Using the above numbers, we see that phase separation could add between 0 to 3 Gyr to the white dwarf ages and still be consistent with the overall picture of Galaxy formation. Our calculated maximum value of 1.5 Gyr fits within these bounds, as does our best guess value of 0.6 Gyr.Comment: 13 total pages, 8 figures, 3 tables, accepted for publication in the Astrophysical Journal on May 25, 199

    An Introduction to Sheep and Goat Parasite Management in Hawaii

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    This guide describes parasites in goats and sheep. It details symptoms, prevention, treatment of parasites, particularly gastrointestinal worms

    A lattice test of alternative interpretations of ``triviality'' in (λΦ4)4(\lambda \Phi^4)_4 theory

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    There are two physically different interpretations of ``triviality'' in (λΦ4)4(\lambda\Phi^4)_4 theories. The conventional description predicts a second-order phase transition and that the Higgs mass mhm_h must vanish in the continuum limit if vv, the physical v.e.v, is held fixed. An alternative interpretation, based on the effective potential obtained in ``triviality-compatible'' approximations (in which the shifted `Higgs' field h(x)Φ(x)h(x)\equiv \Phi(x)- is governed by an effective quadratic Hamiltonian) predicts a phase transition that is very weakly first-order and that mhm_h and vv are both finite, cutoff-independent quantities. To test these two alternatives, we have numerically computed the effective potential on the lattice. Three different methods were used to determine the critical bare mass for the chosen bare coupling value. All give excellent agreement with the literature value. Two different methods for obtaining the effective potential were used, as a control on the results. Our lattice data are fitted very well by the predictions of the unconventional picture, but poorly by the conventional picture.Comment: 16 pages, LaTeX, 2 eps figures (acknowledgements added in the replaced version
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