12,672 research outputs found
Flight comparison of the transonic agility of the F-111A airplane and the F-111 supercritical wing airplane
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
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
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
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
in generalized supergravity
We showed in previous work that for homogeneous Yang-Baxter (YB) deformations
of AdSS, the open string metric and coupling, and as a result the
closed string density , remain undeformed. In this work,
in addition to extending these results to the deformation associated with the
modified CYBE, or -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 of generalized supergravity and show for all YB
deformations: 1) appears as a current for center of mass motion on the
worldvolume of a D-branes probing the background, 2) is equal to the
divergence of the noncommutativity parameter, 3) exhibits "holographic"
behavior, where the radial component of vanishes at the AdS boundary, and
4) in pure spinor formalism 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
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
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
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 , the first excited
states of Sn isotopes and the first excited 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 .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
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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