6,678 research outputs found
Dynamical Properties of Multi-Armed Global Spirals in Rayleigh-Benard Convection
Explicit formulas for the rotation frequency and the long-wavenumber
diffusion coefficients of global spirals with arms in Rayleigh-Benard
convection are obtained. Global spirals and parallel rolls share exactly the
same Eckhaus, zigzag and skewed-varicose instability boundaries. Global spirals
seem not to have a characteristic frequency or a typical size ,
but their product is a constant under given experimental
conditions. The ratio of the radii of any two dislocations (,
) inside a multi-armed spiral is also predicted to be constant. Some of
these results have been tested by our numerical work.Comment: To appear in Phys. Rev. E as Rapid Communication
Generation of nonclassical photon states using a superconducting qubit in a microcavity
Based on the interaction between the radiation field and a superconductor, we
propose a way to engineer quantum states using a SQUID charge qubit inside a
microcavity. This device can act as a deterministic single photon source as
well as generate any Fock states and an arbitrary superposition of Fock states
for the cavity field. The controllable interaction between the cavity field and
the qubit can be realized by the tunable gate voltage and classical magnetic
field applied to the SQUID.Comment: 4 page
Shift estimation method based fringe pattern profilometry and performance comparison
In this paper, we present and study two approaches to fringe pattern profilometry (FPP) technique. Based on generalized analysis model for fringe pattern profilometry (FPP), Inverse Function based Shift Estimation (IFSE) and Gradient-based Shift Estimation (GSE) are proposed to calculate the shift between the projected and deformed fringe patterns. Further, computer simulations are utilized to compare the performance between these two methods. Meanwhile, we also compare these two algorithms with Phase Shift profilometry (PSP). It can be seen that both of these two shift estimation algorithms can significantly improve the measurement accuracy when the fringe patterns are nonlinearly distorted
Inductive Matrix Completion and Root-MUSIC-Based Channel Estimation for Intelligent Reflecting Surface (IRS)-Aided Hybrid MIMO Systems
This paper studies the estimation of cascaded channels in passive intelligent
reflective surface (IRS)- aided multiple-input multiple-output (MIMO) systems
employing hybrid precoders and combiners. We propose a low-complexity solution
that estimates the channel parameters progressively. The angles of departure
(AoDs) and angles of arrival (AoAs) at the transmitter and receiver,
respectively, are first estimated using inductive matrix completion (IMC)
followed by root-MUSIC based super-resolution spectrum estimation.
Forward-backward spatial smoothing (FBSS) is applied to address the coherence
issue. Using the estimated AoAs and AoDs, the training precoders and combiners
are then optimized and the angle differences between the AoAs and AoDs at the
IRS are estimated using the least squares (LS) method followed by FBSS and the
root-MUSIC algorithm. Finally, the composite path gains of the cascaded channel
are estimated using on-grid sparse recovery with a small-size dictionary. The
simulation results suggest that the proposed estimator can achieve improved
channel parameter estimation performance with lower complexity as compared to
several recently reported alternatives, thanks to the exploitation of the
knowledge of the array responses and low-rankness of the channel using
low-complexity algorithms at all the stages.Comment: Submitted to IEE
Lipschitz equivalence of subsets of self-conformal sets
We give sufficient conditions to guarantee that if two self-conformal sets E
and F have Lipschitz equivalent subsets of positive measure, then there is a
bilipschitz map of E into, or onto, F
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