291,732 research outputs found

    Optimum dry-cooling sub-systems for a solar air conditioner

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    Dry-cooling sub-systems for residential solar powered Rankine compression air conditioners were economically optimized and compared with the cost of a wet cooling tower. Results in terms of yearly incremental busbar cost due to the use of dry-cooling were presented for Philadelphia and Miami. With input data corresponding to local weather, energy rate and capital costs, condenser surface designs and performance, the computerized optimization program yields design specifications of the sub-system which has the lowest annual incremental cost

    A general framework for stochastic traveling waves and patterns, with application to neural field equations

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    In this paper we present a general framework in which to rigorously study the effect of spatio-temporal noise on traveling waves and stationary patterns. In particular the framework can incorporate versions of the stochastic neural field equation that may exhibit traveling fronts, pulses or stationary patterns. To do this, we first formulate a local SDE that describes the position of the stochastic wave up until a discontinuity time, at which point the position of the wave may jump. We then study the local stability of this stochastic front, obtaining a result that recovers a well-known deterministic result in the small-noise limit. We finish with a study of the long-time behavior of the stochastic wave.Comment: 43 pages, 3 figure

    Lattice Boltzmann Thermohydrodynamics

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    We introduce a lattice Boltzmann computational scheme capable of modeling thermohydrodynamic flows of monatomic gases. The parallel nature of this approach provides a numerically efficient alternative to traditional methods of computational fluid dynamics. The scheme uses a small number of discrete velocity states and a linear, single-time-relaxation collision operator. Numerical simulations in two dimensions agree well with exact solutions for adiabatic sound propagation and Couette flow with heat transfer.Comment: 11 pages, Physical Review E: Rapid Communications, in pres

    Asymptotic quasinormal modes of a coupled scalar field in the Gibbons-Maeda dilaton spacetime

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    Adopting the monodromy technique devised by Motl and Neitzke, we investigate analytically the asymptotic quasinormal frequencies of a coupled scalar field in the Gibbons-Maeda dilaton spacetime. We find that it is described by eβω=[1+2cos(2ξ+12π)]eβIω[2+2cos(2ξ+12π)] e^{\beta \omega}=-[1+2\cos{(\frac{\sqrt{2\xi+1}}{2} \pi)}]-e^{-\beta_I \omega}[2+2\cos{(\frac{\sqrt{2\xi+1}}{2}\pi)}], which depends on the structure parameters of the background spacetime and on the coupling between the scalar and gravitational fields. As the parameters ξ\xi and βI\beta_I tend to zero, the real parts of the asymptotic quasinormal frequencies becomes THln3T_H\ln{3}, which is consistent with Hod's conjecture. When ξ=91/18\xi={91/18} , the formula becomes that of the Reissner-Nordstr\"{o}m spacetime.Comment: 6 pages, 1 figur
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