Qianshun Chang

A new algorithm for calculating Adomian polynomials

In this paper, a new algorithm for calculating Adomian polynomials for nonlinear operators will be established by parametrization. The algorithm requires less formula than the previous method developed by Adomian [Nonlinear Stochastic Operator Equations, Academic Press, 1986, G. Adomian, R. Rach, On composite nonlinearities and decomposition method. J. Math. Anal. Appl. 113 (1986) 504-509, G. Adomian, Applications of Nonlinear Stochastic Systems Theory to Physics, Kluwer, 1988]. Many forms of nonlinearity will be studied to illustrate the new algorithm. The new algorithm will be extended to calculate Adomian polynomials for nonlinearity of several variables.

A conservative numerical scheme for a class of nonlinear Schrödinger equation with wave operator

In this paper, the initial-boundary value problem of a class of nonlinear Schrodinger equation with wave operator is considered. An explicit and efficient finite difference scheme is presented. This is a scheme of four levels with a discrete conservative law. Convergence and stability are proved.

New time dependent model for image restoration

In this paper, we propose a new time dependent model for solving total variation (TV) minimization problems in image restoration. We present a proof of the existence, uniqueness and stability of the viscosity solution of our model. The results from our new model by explicit numerical schemes are compared with the results from those models introduced by several image researchers by simple and significant 2D numerical experiments. Experimental results demonstrate that our new model can get better results than the existing models.

New interpolation formulas of using geometric assumptions in the algebraic multigrid method

In this paper, new interpolation formulas for using geometric assumptions in the algebraic multigrid (AMG) method are reported. The theoretical and convergence analysis will be presented. The effectiveness and robustness of these interpolation formulas are demonstrated by numerical experiments. Not only is a rapid rate of convergence achieved, but the AMG algorithm used in conjunction with these formulas can also be used to solve various ill-conditioned systems of equations. The principal contribution of the present method is to extend the range of applications of the AMG method developed by Ruge and Stuben.

Remark on convergence of algebraic multigrid in the form of matrix decomposition

We introduce the convergence of algebraic multigrid in the form of matrix decomposition. The convergence is proved in block versions of the multi-elimination incomplete LU (BILUM) factorization technique and the approximation of their inverses to preserve sparsity. The convergence theorem can be applied to general interpolation operator. Furthermore, we discuss the error caused by the error matrix.

An adaptive algorithm for TV-based model of three norms Lq(q=12,1,2) in image restoration

In this paper, we present an adaptive method for the TV-based model of three norms Lq(q=12,1,2) for the image restoration problem. The algorithm with the L2 norm is used in the smooth regions, where the value of |∇u| is small. The algorithm with the L12 norm is applied for the jumps, where the value of |∇u| is large. When the value of |∇u| is moderate, the algorithm with the L1 norm is employed. Thus, the three algorithms are applied for different regions of a given image such that the advantages of each algorithm are adopted. The numerical experiments demonstrate that our adaptive algorithm can not only keep the original edge and original detailed information but also weaken the staircase phenomenon in the restored images. Specifically, in contrast to the L1 norm as in the Rudin–Osher–Fatemi model, the L2 norm yields better results in the smooth and flat regions, and the L12 norm is more suitable in regions with strong discontinuities. Therefore, our adaptive algorithm is efficient and robust even for images with large noises.