246,858 research outputs found
Fast mode of rotating atoms in one-dimensional lattice rings
We study the rotation of atoms in one-dimensional lattice rings. In
particular, the "fast mode", where the ground state atoms rotate faster than
the stirring rotating the atoms, is studied both analytically and numerically.
The conditions for the transition to the fast mode are found to be very
different from that in continuum rings. We argue that these transition
frequencies remain unchanged for bosonic condensates described in a mean field.
We show that Fermionic interaction and filling factor have a significant effect
on the transition to the fast mode, and Pauli principle may suppress it
altogether.Comment: 4 pages, 5 figure
Multivariable Repetitive-predictive Controllers using Frequency Decomposition
Repetitive control is a methodology for the tracking of a periodic reference signal. This paper develops a new approach to repetitive control systems design using receding horizon control with frequency decomposition of the reference signal. Moreover, design and implementation issues for this form of repetitive predictive control are investigated from the perspectives of controller complexity and the effects of measurement noise. The analysis is supported by a simulation study on a multi-input multi-output robot arm where the model has been constructed from measured frequency response data, and experimental results from application to an industrial AC motor
Consequences of covariant kaon dynamics in heavy ion collisions
The influence of the chiral mean field on the kaon dynamics in heavy ion
reactions is investigated. Inside the nuclear medium the kaons are described as
dressed quasi-particles carrying effective masses and momenta. A momentum
dependent part of the interaction which resembles a Lorentz force originates
from spatial components of the vector field and provides an important
contribution to the in-medium kaon dynamics. This contribution is found to
counterbalance the influence of the vector potential on the in-plane flow
to a strong extent. Thus it appears to be difficult to restrict the in-medium
potential from the analysis of the corresponding transverse flow.Comment: 14 pages, RevTex, 3 PS figures, accepted for publication in Phys.
Lett.
Adaptive multibeam phased array design for a Spacelab experiment
The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio
Radial flow of kaon mesons in heavy ion reactions
This work investigates the collective motion of kaons in heavy ion reactions
at SIS energies (about 1-2 GeV/nucleon). A radial collective flow of
mesons is predicted to exist in central Au + Au collisions, which manifests in
a characteristic "shoulder-arm" shape of the transverse mass spectrum of the
midrapidity mesons. The radial flow arises from the repulsive
mean field in nuclear matter. In spite of a strong reabsorption and
rescattering the attractive mean field leads as well to a collective
radial flow of mesons. The radial flow, however, is different from
that of mesons and can be observed by a characteristic "concave"
structure of the transverse mass spectrum of the mesons emitted at
midrapidity. The kaon radial flows can therefore serve as a novel tool for the
investigation of kaon properties in dense nuclear matter.Comment: 30 pages RevTex, 5 PS figures, accepted for publication in Phys. Rev.
Axisymmetric Dynamic Response of Spherical and Cylindrical Shells
Axisymmetric dynamic response of spherical and cylindrical shell
Collective Fluorescence Enhancement In Nanoparticle Clusters
Many nanoscale systems are known to emit light intermittently under continuous illumination. In the fluorescence of single semiconductor nanoparticles, the distributions of bright and dark periods (\u27on\u27 and \u27off\u27 times) follow Levy statistics. Although fluorescence from single-quantum dots and from macroscopic quantum dot ensembles has been studied, there has been little study of fluorescence from small ensembles. Here we show that blinking nanorods (NRs) interact with each other in a cluster, and the interactions affect the blinking statistics. The on-times in the fluorescence of a NR cluster increase dramatically; in a cluster with N NRs, the maximum on-time increases by a factor of N or more compared with the combined signal from N well-separated NRs. Our study emphasizes the use of statistical properties in identifying the collective dynamics. The scaling of this interaction-induced increase of on-times with number of NRs reveals a novel collective effect at the nanoscale
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