12,672 research outputs found

    Flight comparison of the transonic agility of the F-111A airplane and the F-111 supercritical wing airplane

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    A flight research program was conducted to investigate the improvements in maneuverability of an F-111A airplane equipped with a supercritical wing. In this configuration the aircraft is known as the F-111 TACT (transonic aircraft technology) airplane. The variable-wing-sweep feature permitted an evaluation of the supercritical wing in many configurations. The primary emphasis was placed on the transonic Mach number region, which is considered to be the principal air combat arena for fighter aircraft. An agility study was undertaken to assess the maneuverability of the F-111A aircraft with a supercritical wing at both design and off-design conditions. The evaluation included an assessment of aerodynamic and maneuver performance in conjunction with an evaluation of precision controllability during tailchase gunsight tracking tasks

    Spectral Comparison of Weak Short Bursts to the Persistent X-rays from the Magnetar 1E 1547.0-5408 in its 2009 Outburst

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    In January 2009, the 2.1-sec anomalous X-ray pulsar 1E 1547.0-5408 evoked intense burst activity. A follow-up Suzaku observation on January 28 recorded enhanced persistent emission both in soft and hard X-rays (Enoto et al. 2010b). Through re-analysis of the same Suzaku data, 18 short bursts were identified in the X-ray events recorded by the Hard X-ray Detector (HXD) and the X-ray Imaging Spectrometer (XIS). Their spectral peaks appear in the HXD-PIN band, and their 10-70 keV X-ray fluences range from ~2e-9 erg cm-2 to 1e-7 erg cm-2. Thus, the 18 events define a significantly weaker burst sample than was ever obtained, ~1e-8-1e-4 erg cm-2. In the ~0.8 to ~300 keV band, the spectra of the three brightest bursts can be represented successfully by a two-blackbody model, or a few alternative ones. A spectrum constructed by stacking 13 weaker short bursts with fluences in the range (0.2-2)e-8 erg s-1 is less curved, and its ratio to the persistent emission spectrum becomes constant at ~170 above ~8 keV. As a result, the two-blackbody model was able to reproduce the stacked weaker-burst spectrum only after adding a power-law model, of which the photon index is fixed at 1.54 as measured is the persistent spectrum. These results imply a possibility that the spectrum composition employing an optically-thick component and a hard power-law component can describe wide-band spectra of both the persistent and weak-burst emissions, despite a difference of their fluxes by two orders of magnitude. Based on the spectral similarity, a possible connection between the unresolved short bursts and the persistent emission is discussed.Comment: 21 pages, 18 figures and 3 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journa

    Microwave radiometric studies and ground truth measurements of the NASA/USGS Southern California test site

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    The field measurement program conducted at the NASA/USGS Southern California Test Site is discussed. Ground truth data and multifrequency microwave brightness data were acquired by a mobile field laboratory operating in conjunction with airborne instruments. The ground based investigations were performed at a number of locales representing a variety of terrains including open desert, cultivated fields, barren fields, portions of the San Andreas Fault Zone, and the Salton Sea. The measurements acquired ground truth data and microwave brightness data at wavelengths of 0.8 cm, 2.2 cm, and 21 cm

    Effect of Electrolyte Balance in Low-Protein Diets on Broiler Performance and Tibial Dyschondroplasia Incidence

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    A proper dietary electrolyte balance (DEB) is essential to ensure an optimum acid-base equilibrium and broiler performance. In low-CP diets, this balance can be affected by reduction of soybean meal and inclusion of high levels of synthetic amino acids. Although, some studies have related low-protein diets supplemented with amino acids and DEB, these relations are not well explained, because some research demonstrates confusion about the deficiency and balance of nutrients. The objective of these experiments was to evaluate the DEB effects of diets with low levels of protein supplemented with amino acids on broiler performance and bone development. Results indicated that DEB and CP content influenced broiler chick performance in the starter and growing periods. There was no significant effect due to the interaction between DEB and CP content for tibial dyschondroplasia incidence (TD) or in bone breaking resistance during the growing period of either experiment. The incidence of TD was reduced with 253 mEq/kg DEB in the starter period

    II in generalized supergravity

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    We showed in previous work that for homogeneous Yang-Baxter (YB) deformations of AdS5×_5\timesS5^5, the open string metric and coupling, and as a result the closed string density e2Φge^{-2 \Phi} \sqrt{g}, remain undeformed. In this work, in addition to extending these results to the deformation associated with the modified CYBE, or η\eta-deformation, we identify the Page forms as the open string counterpart for RR fields and demonstrate case by case that the non-zero Page forms remain invariant under YB deformations. We give a physical meaning to the Killing vector II of generalized supergravity and show for all YB deformations: 1) II appears as a current for center of mass motion on the worldvolume of a D-branes probing the background, 2) II is equal to the divergence of the noncommutativity parameter, 3) II exhibits "holographic" behavior, where the radial component of II vanishes at the AdS boundary, and 4) in pure spinor formalism II is related to a certain state in the BRST cohomology.Comment: 11 pages, 2 column; v2 references updated; v3 to appear in EPJ

    Magnetic translation groups in an n-dimensional torus

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    A charged particle in a uniform magnetic field in a two-dimensional torus has a discrete noncommutative translation symmetry instead of a continuous commutative translation symmetry. We study topology and symmetry of a particle in a magnetic field in a torus of arbitrary dimensions. The magnetic translation group (MTG) is defined as a group of translations that leave the gauge field invariant. We show that the MTG on an n-dimensional torus is isomorphic to a central extension of a cyclic group Z_{nu_1} x ... x Z_{nu_{2l}} x T^m by U(1) with 2l+m=n. We construct and classify irreducible unitary representations of the MTG on a three-torus and apply the representation theory to three examples. We shortly describe a representation theory for a general n-torus. The MTG on an n-torus can be regarded as a generalization of the so-called noncommutative torus.Comment: 29 pages, LaTeX2e, title changed, re-organized, to be published in Journal of Mathematical Physic

    An Easy-to-Construct Automated Winkler Titration System

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    The instrument described in this report is an updated version of the high precision, automated Winkler titration system described by Friederich et al.(1984). The original instrument was based on the work of Bryan et al. (1976) who developed a colorimetric endpoint detector and on the work of Williams and Jenkinson (1982) who produced an automated system that used this detector. The goals of our updated version of the device described by Friederich et al. (1984) were as follows: 1) Move control of the system to the MS-DOS environment because HP-85 computers are no longer in production and because more user-friendly programs could be written using the IBM XT or AT computers that control the new device. 2) Use more "off the shelf" components and reduce the parts count in the new system so that it could be easily constructed and maintained. This report describes how to construct and use the new automated Winkler titration device. It also includes information on the chemistry of the Winkler titration, and detailed instructions on how to prepare reagents, collect samples, standardize and perform the titrations (Appendix I: Codispoti, L.A. 1991 On the determination of dissolved oxygen in sea water, 15pp.). A disk containing the program needed to operate the new device is also included. (pdf contains 33 pages

    Self-Consistent Velocity Dependent Effective Interactions

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    The theory of self-consistent effective interactions in nuclei is extended for a system with a velocity dependent mean potential. By means of the field coupling method, we present a general prescription to derive effective interactions which are consistent with the mean potential. For a deformed system with the conventional pairing field, the velocity dependent effective interactions are derived as the multipole pairing interactions in doubly-stretched coordinates. They are applied to the microscopic analysis of the giant dipole resonances (GDR's) of 148,154Sm{}^{148,154}Sm, the first excited 2+2^+ states of Sn isotopes and the first excited 33^- states of Mo isotopes. It is clarified that the interactions play crucial roles in describing the splitting and structure of GDR peaks, in restoring the energy weighted sum rule, and in reducing the values of B(Eλ)B(E\lambda).Comment: 35 pages, RevTeX, 7 figures (available upon request), to appear in Phys.Rev.

    A year in the life of GW170817: the rise and fall of a structured jet from a binary neutron star merger

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    We present the results of our year-long afterglow monitoring of GW170817, the first binary neutron star (NS) merger detected by advanced LIGO and advanced Virgo. New observations with the Australian Telescope Compact Array (ATCA) and the Chandra X-ray Telescope were used to constrain its late-time behavior. The broadband emission, from radio to X-rays, is well-described by a simple power-law spectrum with index ~0.585 at all epochs. After an initial shallow rise ~t^0.9, the afterglow displayed a smooth turn-over, reaching a peak X-ray luminosity of ~5e39 erg/s at 160 d, and has now entered a phase of rapid decline ~t^(-2). The latest temporal trend challenges most models of choked jet/cocoon systems, and is instead consistent with the emergence of a relativistic structured jet seen at an angle of ~22 deg from its axis. Within such model, the properties of the explosion (such as its blastwave energy E_K~2E50 erg, jet width theta_c~4 deg, and ambient density n~3E-3 cm^(-3)) fit well within the range of properties of cosmological short GRBs.Comment: 11 pages, 8 figures, 2 tables, MNRAS, in press. Final version, minor changes only relative to original submission dated 21 August 201
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