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Now showing items 1-10 of 20

#### Large Deviation Principle and Inviscid Shell Models

Contributor:Bessaih, Hakima; Millet, A.

Date:2009-11-26

Date:2009-11-26

A LDP is proved for the inviscid shell model of turbulence. As the viscosity coefficient v converges to 0 and the noise intensity is multiplied by root v, we prove that some shell models of turbulence with a multiplicative ...

#### Renormalization Group Analysis of Nonlinear Diffusion Equations with Time Dependent Coefficients : Analytical Results

Contributor:Braga, G. A.; Furtado, Fred; Moreira, J. M.; Rolla, L. T.

Date:2007-06-01

Date:2007-06-01

We study the long-time asymptotics of a certain class of nonlinear diffusion equations with time-dependent diffusion coefficients which arise, for instance, in the study of transport by randomly fluctuating velocity fields. ...

#### Reconstruction of a Spherically Symmetrical Speed of Sound

Contributor:McLaughlin, J. R.; Polyakov, Peter; Sacks, P. E.

Date:1994-10-01

Date:1994-10-01

Consider the inverse acoustic scattering problem for a spherically symmetric inhomogeneity of compact support that arises, among other places, in nondestructive testing. Define the corresponding homogeneous and inhomogeneous ...

#### Set of All MXN Rectangular Real Matrices of Rank-R Is Connected by Analytic Regular Arcs, The

Contributor:Evard, J. C.; Jafari, Farhad

Date:1994-02-01

Date:1994-02-01

It is well known that the set of all square invertible real matrices has two connected components. The set of all m x n rectangular real matrices of rank r has only one connected component when m ≠ n or r < m = n. We show ...

#### Spatiotemporal Distributions of Migratory Birds : Patchy Models with Delay

Contributor:Gourley, S. A.; Liu, Rongsong; Wu, J. H.

Date:2010-01-01

Date:2010-01-01

We derive and analyze a mathematical model for the spatiotemporal distribution of a migratory bird species. The birds have specific sites for breeding and winter feeding, and usually several stopover sites along the migration ...

#### Evolution of a Random Vortex Filament, The

Contributor:Bessaih, Hakima; Gubinelli, M.; Russo, F.

Date:2005-09-01

Date:2005-09-01

We study an evolution problem in the space of continuous loops in a three-dimensional Euclidean space modeled upon the dynamics of vortex lines in 3d incompressible and inviscid fluids. We establish existence of a local ...

#### Scaling Analysis for the Tracer Flow Problem in Self-Similar Permeability Fields

Contributor:Borges, M. R.; Furtado, Fred; Pereira, Felipe; Souto, H. P. A.

Date:2008-01-01

Date:2008-01-01

The spatial variations in porous media (aquifers and petroleum reservoirs) occur at all length scales (from the pore to the reservoir scale) and are incorporated into the governing equations for multiphase flow problems ...

#### Renormalization Group Analysis of Nonlinear Diffusion Equations with Periodic Coefficients

Contributor:Braga, G. A.; Furtado, Fred; Moreira, J. M.; Rolla, L. T.

Date:2003-01-01

Date:2003-01-01

In this paper we present an efficient numerical approach based on the renormalization group method for the computation of self-similar dynamics. The latter arise, for instance, as the long-time asymptotic behavior of ...

#### Sign Patterns That Allow a Positive or Nonnegative Left Inverse

Contributor:Kim, I. J.; Olesky, D. D.; Shader, Bryan L.; Van den Driessche, P.

Date:2006-01-01

Date:2006-01-01

An m by n sign pattern S is an m by n matrix with entries in {+,-, 0}. Such a sign pattern allows a positive (resp., nonnegative) left inverse, provided that there exist an m by n matrix A with the sign pattern S and an n ...

#### Comment on "A Dynamic Nonlinear Subgrid-Scale Stress Model" [Phys. Fluids 17, 035109, (2005)]

Contributor:Heinz, Stefan

Date:2005-09-01

Date:2005-09-01