55,565 research outputs found
Distributed active control of large flexible space structures
This progress report summarizes the research work performed at the Catholic University of America on the research grant entitled Distributed Active Control of Large Flexible Space Structures, funded by NASA/Goddard Space Flight Center, under grant number NAG5-749, during the period of March 15, 1986 to September 15, 1986
Bound states and extended states around a single vortex in the d-wave superconductors
Making use of the Bogoliubov-de Gennes equation for the d-wave
superconductors, we investigate the quasi-particle spectrum around a single
vortex. Taking , we found that there are bound states which are
localized around the vortex core, and extended states which are rather uniform,
for where is the quasi-particle energy and is the
asymptotic value of the order parameter for away from the vortex.Comment: 4 pages, 6 figure
Dynamics of horizontal-like maps in higher dimension
We study the regularity of the Green currents and of the equilibrium measure
associated to a horizontal-like map in C^k, under a natural assumption on the
dynamical degrees. We estimate the speed of convergence towards the Green
currents, the decay of correlations for the equilibrium measure and the
Lyapounov exponents. We show in particular that the equilibrium measure is
hyperbolic. We also show that the Green currents are the unique invariant
vertical and horizontal positive closed currents. The results apply, in
particular, to Henon-like maps, to regular polynomial automorphisms of C^k and
to their small pertubations.Comment: Dedicated to Professor Gennadi Henkin on the occasion of his 65th
birthday, 37 pages, to appear in Advances in Mat
QCD dynamics in mesons at soft and hard scales
Using a ladder-rainbow kernel previously established for the soft scale of
light quark hadrons, we explore, within a Dyson-Schwinger approach, phenomena
that mix soft and hard scales of QCD. The difference between vector and axial
vector current correlators is examined to estimate the four quark chiral
condensate and the leading distance scale for the onset of non-perturbative
phenomena in QCD. The valence quark distributions, in the pion and kaon,
defined in deep inelastic scattering, and measured in the Drell Yan process,
are investigated with the same ladder-rainbow truncation of the Dyson-Schwinger
and Bethe-Salpeter equations.Comment: 6 pages, 1 double panel figure, invited talk presented at the
Workshop on Achievements and New Directions in Subatomic Physics, Adelaide,
Australia, February 2010, to be published by AIP Conf. Pro
Soft and Hard scale QCD Dynamics in Mesons
Using a ladder-rainbow kernel previously established for the soft scale of
light quark hadrons, we explore the extension to masses and electroweak decay
constants of ground state pseudoscalar and vector quarkonia and heavy-light
mesons in the c- and b-quark regions. We make a systematic study of the
effectiveness of a constituent mass concept as a replacement for a heavy quark
dressed propagator. The difference between vector and axial vector current
correlators is examined to estimate the four quark chiral condensate. The
valence quark distributions, in the pion and kaon, defined in deep inelastic
scattering, and measured in the Drell Yan process, are investigated with the
same ladder-rainbow truncation of the Dyson-Schwinger and Bethe-Salpeter
equations.Comment: 10 pages, 2 double panel figures, invited talk presented at the XII
Mexican Workshop on Particles and Fields, Mazatlan, Sinaloa, Mexico, November
2009; to be published by AIP Conf. Pro
Towards a Base UML Profile for Architecture Description
This paper discusses a base UML profile for architecture description as supported by existing Architecture Description Languages (ADLs). The profile may be extended so as to enable architecture modeling both as expressed in conventional ADLs and according to existing runtime infrastructures (e.g., system based on middleware architectures).
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Implementation of polarization diversity pulse-pair technique using airborne W-band radar
This work describes the implementation of polarization diversity on the National Research Council Canada W-band Doppler radar and presents the first-ever airborne Doppler measurements derived via polarization diversity pulse-pair processing. The polarization diversity pulse-pair measurements are interleaved with standard pulse-pair measurements with staggered pulse repetition frequency, this allows a better understanding of the strengths and drawbacks of polarization diversity, a methodology that has been recently proposed for wind-focused Doppler radar space missions. Polarization diversity has the clear advantage of making possible Doppler observations of very fast decorrelating media (as expected when deploying Doppler radars on fast-moving satellites) and of widening the Nyquist interval, thus enabling the observation of very high Doppler velocities (up to more than 100 m s−1 in the present work). Crosstalk between the two polarizations, mainly caused by depolarization at backscattering, deteriorated the quality of the observations by introducing ghost echoes in the power signals and by increasing the noise level in the Doppler measurements. In the different cases analyzed during the field campaigns, the regions affected by crosstalk were generally associated with highly depolarized surface returns and depolarization of backscatter from hydrometeors located at short ranges from the aircraft. The variance of the Doppler velocity estimates can be well predicted from theory and were also estimated directly from the observed correlation between the H-polarized and V-polarized successive pulses. The study represents a key milestone towards the implementation of polarization diversity in Doppler space-borne radars
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