15,039 research outputs found

    The pressure moments for two rigid spheres in low-Reynolds-number flow

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    The pressure moment of a rigid particle is defined to be the trace of the first moment of the surface stress acting on the particle. A Faxén law for the pressure moment of one spherical particle in a general low-Reynolds-number flow is found in terms of the ambient pressure, and the pressure moments of two rigid spheres immersed in a linear ambient flow are calculated using multipole expansions and lubrication theory. The results are expressed in terms of resistance functions, following the practice established in other interaction studies. The osmotic pressure in a dilute colloidal suspension at small Péclet number is then calculated, to second order in particle volume fraction, using these resistance functions. In a second application of the pressure moment, the suspension or particle-phase pressure, used in two-phase flow modeling, is calculated using Stokesian dynamics and results for the suspension pressure for a sheared cubic lattice are reported

    Functorial properties of Putnam's homology theory for Smale spaces

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    We investigate functorial properties of Putnam's homology theory for Smale spaces. Our analysis shows that the addition of a conjugacy condition is necessary to ensure functoriality. Several examples are discussed that elucidate the need for our additional hypotheses. Our second main result is a natural generalization of Putnam's Pullback Lemma from shifts of finite type to non-wandering Smale spaces.Comment: Updated to agree with published versio

    Farmland Prices

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    land, price, Ontario, Canada, Agricultural and Food Policy, Agricultural Finance, Demand and Price Analysis, Land Economics/Use,

    Evaluation of liquid methane storage and transfer problems in supersonic aircraft

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    Evaluation of liquid methane storage and transfer problems for future supersonic aircraft cryogenic fuel requirement

    Classical Robustness of Quantum Unravellings

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    We introduce three measures which quantify the degree to which quantum systems possess the robustness exhibited by classical systems when subjected to continuous observation. Using these we show that for a fixed environmental interaction the level of robustness depends on the measurement strategy, or unravelling, and that no single strategy is maximally robust in all ways.Comment: 8 Pages, 2 figures, Version 2. Minor changes to wording for clarification and some references added. Accepted for publication in Europhysics Letter

    Stability of degenerate Cauchy horizons in black hole spacetimes

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    In the multihorizon black hole spacetimes, it is possible that there are degenerate Cauchy horizons with vanishing surface gravities. We investigate the stability of the degenerate Cauchy horizon in black hole spacetimes. Despite the asymptotic behavior of spacetimes (flat, anti-de Sitter, or de Sitter), we find that the Cauchy horizon is stable against the classical perturbations, but unstable quantum mechanically.Comment: Revtex, 4 pages, no figures, references adde

    An Application of a Second Order Upwinding Scheme for an Implicit LES CFD Solver

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    The flow past a right square cylinder in a duct at a Reynolds number of 22 x 103 has been employed to validate the use of second order upwinding, instead of a subgrid model in a largeeddy simulation. In this extensively studied problem, all the numerical work has been based on a simplifying assumption that the square cylinder is infinite, which resulted in all previous workers using cyclic boundary conditions so as to reduce the required domain size. It is not clear how the size of the domain had been established and, therefore, whether it was sufficiently large to adequately represent the experimental flow in a duct. The integral quantities of the drag and lift coefficient and the Strouhal number, converged towards the experimental values as the grid resolution is increased. However, the cyclic boundary condition assumption leads to a flow width that provides too small a region of uncorrelated flow. A model of the full duct case, identical to experimental domain, was used to contrast the cyclic domain results. Surprisingly the second order upwind model generates power spectra that appear to correctly capture the energy cascade down to the inertial and viscous ranges
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