23 research outputs found

    The Cauchy problem for a fourth order parabolic equation by difference methods

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    Thesis (Ph.D.)--Boston UniversityThis paper deals with the solution of parabolic partial differential equations by difference methods. It is first concerned with obtaining certain basic results for the nth order equation... This enables one to exhibit a stable difference equation compatible with (5). Once assured of the existence of such an equation, it is employed in proving an existence theorem for a solution of the differential equation. The theorem states that if the coefficients a;(x,t) and the function d(x, t) in (5), and the function f(x) in:(2) possess a sufficient number of uniformly continuous and bounded derivatives in R, and a0(x,t) is negative and bounded away from zero, then there exists a solution of (5), (2) possessing a certain number of uniformly continuous and bounded derivatives. [TRUNCATED

    Convergence of the Generalized Volume Averaging Method on a Convection-Diffusion Problem: A Spectral Perspective

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    A mixed formulation is proposed and analyzed mathematically for coupled convection-diffusion in heterogeneous medias. Transfer in solid parts driven by pure diffusion is coupled with convection-diffusion transfer in fluid parts. This study is carried out for translation-invariant geometries (general infinite cylinders) and unidirectional flows. This formulation brings to the fore a new convection-diffusion operator, the properties of which are mathematically studied: its symmetry is first shown using a suitable scalar product. It is proved to be self-adjoint with compact resolvent on a simple Hilbert space. Its spectrum is characterized as being composed of a double set of eigenvalues: one converging towards −∞ and the other towards +∞, thus resulting in a nonsectorial operator. The decomposition of the convection-diffusion problem into a generalized eigenvalue problem permits the reduction of the original three-dimensional problem into a two-dimensional one. Despite the operator being nonsectorial, a complete solution on the infinite cylinder, associated to a step change of the wall temperature at the origin, is exhibited with the help of the operator’s two sets of eigenvalues/eigenfunctions. On the computational point of view, a mixed variational formulation is naturally associated to the eigenvalue problem. Numerical illustrations are provided for axisymmetrical situations, the convergence of which is found to be consistent with the numerical discretization

    Introduction to ordinary differential equations

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    xi, 609 p. : il.; 23 cm

    Differential Equations

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    IV, 807 tr.; 25 cm

    Introduction to Ordinary Differential Equations

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    VII, 503 tr.; 25 cm

    Differential equations /

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