This paper compares the mean acquisition time performance of two serial search acquisition schemes over frequency-selective multipath Rayleigh fading channels. Both the conventional cell-by-cell detection and the novel joint twin-cell detection are characterised. In contrast to the majority of published results considering only one correct timing state (H1 cell) in the uncertainty region of the...

A shadowgraph optical setup is used to study the time evolution of Soret induced convection in a colloidal suspension. We obtain a scale invariant behavior for the solutal Nusselt number as a function of the Rayleigh number. In a typical Rayleigh-Bénard experiment a horizontal slab of a fluid is contained between a top and bottom plates maintained at two different temperatures (higher temperatu...

This paper examines a simplified active combustion model in which the reaction influences the flow. We consider front propagation in a reactive Boussinesq system in an infinite vertical strip. Nonlinear stability of planar fronts is established for narrow domains when the Rayleigh number is not too large. Planar fronts are shown to be linearly unstable with respect to long wavelength perturbati...

In this paper we consider linear Hamiltonian differential systems without the controllability (or normality) assumption. We prove the Rayleigh principle for these systems with Dirichlet boundary conditions, which provides a variational characterization of the finite eigenvalues of the associated self-adjoint eigenvalue problem. This result generalizes the traditional Rayleigh principle to possi...

Bounds for the bulk heat transport in Rayleigh-Benard convection for an infinite Prandtl number fluid are derived from the primitive equations. The enhancement of heat transport beyond the minimal conduction value (the Nusselt number Nu) is bounded in terms of the nondimensional temperature difference across the layer (the Rayleigh number Ra) according to Nu ≤ c Ra where c < 1 is an absolute co...

A thermal lattice Boltzmann method based on the BGK model has been used to simulate high Rayleigh number natural convection in a square cavity. The model uses the double populations approach to simulate hydrodynamic and thermal fields. The traditional lattice Boltzmann method on a uniform grid has unreasonably high grid requirements at higher Rayleigh numbers which renders the method impractica...

We study the localization of Rayleigh waves propagating in a semi-infinite and isotropic medium with inhomogeneities that are modeled as rods parallel to the incoming wave front and are distributed randomly up to a maximum depth. For a perfectly smooth surface, the localization length of a Rayleigh wave is predicted to reach a minimum at intermediate wavelength l and to diverge for both low and...

We consider a horizontal fluid layer between two rigid boundaries, maintained in a stationary thermal nonequilibrium state below the convective Rayleigh-Bénard instability. We derive an explicit expression for the nonequilibrium structure factor in a first-order Galerkin approximation valid for negative and positive Rayleigh numbers R up to the critical Rayleigh number R(c) associated with the ...

We present an experimental study of the spatial structure of the velocity field in the boundary layer region of a Rayleigh-Bénard convection cell, using water as the working fluid. Our results show that the mean flow, the shear rate, and the viscous boundary layer thickness all change significantly across the conducting horizontal surface of the cell. Moreover, the measurements reveal that the ...

The pattern and style of mantle convection govern the thermal evolution, internal dynamics, and large-scale surface deformation of the terrestrial planets. In order to characterize the nature of heat transport and convective behaviour at Rayleigh numbers, Ra, appropriate for planetary mantles (between 104 and 108), we perform a set of laboratory experiments. Convection is driven by a temperatur...