In this paper, we study the acoustic impedance inversion of 1-dimensional wave equation excited by a wavelet. In order to avoid the ill-posedness, a stable method,which we call the characteristic band method, is const...
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In this paper, we study the acoustic impedance inversion of 1-dimensional wave equation excited by a wavelet. In order to avoid the ill-posedness, a stable method,which we call the characteristic band method, is constructed, and then used as the preconditioner in optimal inversion to increase the speed of convergence.
In this paper,we discuss a Schwarz alternating method for a kind of unboundeddomains, which can be decomposed into a bounded domain and a half-planar domain. Finite Element Method and Natural Boudary Reduction are use...
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In this paper,we discuss a Schwarz alternating method for a kind of unboundeddomains, which can be decomposed into a bounded domain and a half-planar domain. Finite Element Method and Natural Boudary Reduction are used alternatively. The uniform geometric convergence of both continuous and discrete problems is proved. The theoretical results as well as the numerical examples show thatthe convergence rate of this discrete Schwarz iteration is independent of the finiteelement mesh size, but dependent on the overlapping degree of subdomains.
The incompressible Navier-Stokes (INS) equations upon discretization on fixed meshes become a system of differential algebraic equations (DAE) of index 2. It is proved in this paper that for the general explicit and i...
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The incompressible Navier-Stokes (INS) equations upon discretization on fixed meshes become a system of differential algebraic equations (DAE) of index 2. It is proved in this paper that for the general explicit and implicit Runge-Kutta (RK)methods, the time accuracy of velocity is the same as that for the ordinary differential equations, by taking into consideration of the special form of the resulting DAE; (the time accuracy of pressure can be lower). For the three-stage secondorder explicit RK method, algorithms with less (than three) Poisson solutions of pressure are proposed and verified by numerical experiments. However, in practical computation of complex flows it is found that the method must satisfy the so-called consistency condition for the components of the solution (here the velocity and the pressure) of the DAE for the method to be robust.
In this papert we discuss the inverse problem of 1-dimensional acoustic wave equation and propose an approximate inversion method, called multi-reflection elimination method, with which the approximate reflectivity fu...
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In this papert we discuss the inverse problem of 1-dimensional acoustic wave equation and propose an approximate inversion method, called multi-reflection elimination method, with which the approximate reflectivity function can be directly obtained by applying a certain transform to the response. The computation efforts for such method is only of the order N log N, much less than that of solving the direct problem, which is O(N2). On the basis of the proposed method, we also construct an iterative algorithm, and prove that the convergent order of iteration is two.
A new finite volume scheme, based on first order monotone scheme and limited linear reconstruction, is constructed for scalar hyperbolic conservation laws in two dimension,the scheme satisfies the maximum principle an...
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A new finite volume scheme, based on first order monotone scheme and limited linear reconstruction, is constructed for scalar hyperbolic conservation laws in two dimension,the scheme satisfies the maximum principle and approximation the flux with second order accuracy. Numerical results for constant coefficient linear advection and Burgers’equation are presented.
SLMQN is a subspace limited memory quasi-Newton algorithm for solving largescale bound constrained nonlinear programming problems. The algorithm is suitable to these large problems in which the Hessian matrix is diffi...
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SLMQN is a subspace limited memory quasi-Newton algorithm for solving largescale bound constrained nonlinear programming problems. The algorithm is suitable to these large problems in which the Hessian matrix is difficult to compute or is dense,or the number of variables is too large to store and compute an n x n matris. Due to less storage requirement, this algorithm can be used in PCs for solving medium-sized and large problems. The algorithm is implemented in Fortran 77.
In this paper, the elastic contact problems in which no friction is present andtheir linear finite element approximation have been considered. First the elasticcontact problems are classified intuitively according to ...
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In this paper, the elastic contact problems in which no friction is present andtheir linear finite element approximation have been considered. First the elasticcontact problems are classified intuitively according to the different location ofcontact boundary, and for one cases a new proof of existence of the solution ofproblem has been presented. Next a general error estimation of linear finite elementapproximation to the contact problem has been obtained under weaker assumptionfor the regularity of the solution of problem.
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