8,776 research outputs found
A study of a collision avoidance system mounted on a curved ground plane
Research conducted on a traffic advisory and collision avoidance system (TCAS 2) mounted on a curved ground plane is described. It is found that a curved finite ground plane can be used as a good simulation model for the fuselage of an aircraft but may not be good enough to model a whole aircraft due to the shadowing of the vertical stabilizer, wings, etc. The surface curvature of this curved disc significantly affects the monopulse characteristics in the azimuth plane but not as much in the elevation plane. These variations of the monopulse characteristics verify the need of a lookup table for the 64 azimuth beam positions. The best location of a TCAS 2 array on a Boeing 737 is to move it as far from the vertical stabilizer as possible
Impact of noise on a dynamical system: prediction and uncertainties from a swarm-optimized neural network
In this study, an artificial neural network (ANN) based on particle swarm
optimization (PSO) was developed for the time series prediction. The hybrid
ANN+PSO algorithm was applied on Mackey--Glass chaotic time series in the
short-term . The performance prediction was evaluated and compared with
another studies available in the literature. Also, we presented properties of
the dynamical system via the study of chaotic behaviour obtained from the
predicted time series. Next, the hybrid ANN+PSO algorithm was complemented with
a Gaussian stochastic procedure (called {\it stochastic} hybrid ANN+PSO) in
order to obtain a new estimator of the predictions, which also allowed us to
compute uncertainties of predictions for noisy Mackey--Glass chaotic time
series. Thus, we studied the impact of noise for several cases with a white
noise level () from 0.01 to 0.1.Comment: 11 pages, 8 figure
Influence of the photon - neutrino processes on magnetar cooling
The photon-neutrino processes ,
and are investigated
in the presence of a strongly magnetized and dense electron-positron plasma.
The amplitudes of the reactions and
are obtained. In the case of a cold degenerate
plasma contributions of the considering processes to neutrino emissivity are
calculated. It is shown that contribution of the process to neutrino emissivity is supressed in comparision with the
contributions of the processes and
. The constraint on the magnetic field strength in the
magnetar outer crust is obtained.Comment: 8 pages, LaTeX, 2 PS figures, based on the talk presented by D.A.
Rumyantsev at the XV International Seminar Quarks'2008, Sergiev Posad, Moscow
Region, May 23-29, 2008, to appear in the Proceeding
Division Algebras and Extended N=2,4,8 SuperKdVs
The first example of an N=8 supersymmetric extension of the KdV equation is
here explicitly constructed. It involves 8 bosonic and 8 fermionic fields. It
corresponds to the unique N=8 solution based on a generalized hamiltonian
dynamics with (generalized) Poisson brackets given by the Non-associative N=8
Superconformal Algebra. The complete list of inequivalent classes of
parametric-dependent N=3 and N=4 superKdVs obtained from the ``Non-associative
N=8 SCA" is also furnished. Furthermore, a fundamental domain characterizing
the class of inequivalent N=4 superKdVs based on the "minimal N=4 SCA" is
given.Comment: 14 pages, LaTe
Spin Pumping and Inverse Spin Hall Effect in Platinum: The Essential Role of Spin-Memory Loss at Metallic Interfaces
Through combined ferromagnetic resonance, spin-pumping and inverse spin Hall
effect experiments in Co|Pt bilayers and Co|Cu|Pt trilayers, we demonstrate
consistent values of spin diffusion length
nm and of spin Hall angle for Pt. Our
data and model emphasize on the partial depolarization of the spin current at
each interface due to spin-memory loss. Our model reconciles the previously
published spin Hall angle values and explains the different scaling lengths for
the ferromagnetic damping and the spin Hall effect induced voltage.Comment: 6 pages, 3 figures (main text) and 8 pages supplementary. Published
with small modifications in Phys. Rev. Let
Ultralow-Dissipation Superfluid Micromechanical Resonator
Micro and nanomechanical resonators with ultra-low dissipation have great
potential as useful quantum resources. The superfluid micromechanical
resonators presented here possess several advantageous characteristics:
straightforward thermalization, dissipationless flow, and in situ tunability.
We identify and quantitatively model the various dissipation mechanisms in two
resonators, one fabricated from borosilicate glass and one from single crystal
quartz. As the resonators are cryogenically cooled into the superfluid state,
the damping from thermal effects and from the normal fluid component are
strongly suppressed. At our lowest temperatures, damping is limited solely by
internal dissipation in the substrate materials, and reach quality factors up
to 913,000 at 13 mK. By lifting this limitation through substrate material
choice and resonator design, modelling suggests that the resonators should
reach quality factors as high as 10 at 100 mK, putting this architecture in
an ideal position to harness mechanical quantum effects.Comment: 25 pages, 12 figures, 3 table
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