Oscillation-preserving Legendre-Galerkin methods for second kind integral equations with highly oscillatory kernels

Numerical Algorithms - The original solutions of highly oscillatory integral equations usually have rapid oscillation, which means that conventional numerical approaches used to solve these...     

A fast Petrov–Galerkin method for solving the generalized airfoil equation

In this paper we develop a fast Petrov–Galerkin method for solving the generalized airfoil equation using the Chebyshev polynomials. The conventional method for solving this equation leads to a linear system with a dense coefficient matrix. When the order of the linear system is large, the computational complexity for solving the corresponding linear system is huge. For this we propose the matrix truncation strategy, which compresses the dense coefficient matrix into a sparse matrix. We prove that the truncated method preserves the optimal order of the approximate solution for the conventional method. Moreover, we solve the truncated equation using the multilevel augmentation method. The computational complexity for solving this truncated linear system is estimated to be linear up to a logarithmic factor.     

A fast Fourier-collocation method for second boundary integral equations

In this paper we develop a fast collocation method for second boundary integral equations by the trigonometric polynomials. We propose a convenient way to compress the dense matrix representation of a compact integral operator with a smooth kernel under the Fourier basis and the corresponding collocation functionals. The compression leads to a sparse matrix with only O(nlog²n) number of nonzero entries, where 2n+1 denotes the order of the matrix. Thus we develop a fast Fourier-collocation method. We prove that the fast Fourier-collocation method gives the optimal convergence order up to a logarithmic factor. Moreover, we design a fast scheme for solving the corresponding truncated linear system. We establish that this algorithm preserves the quasi-optimal convergence of the approximate solution with requiring a number of O(nlog³n) multiplications.     

一种Cauchy型主值积分的求积公式的一致收敛性

该文首先给出Cauchy型主值积分φ(wf,x)的一种求积公式φ_m^*(wf,x),然后证明序列$φ_m^*(wf,x)}_m=2^∞在整个闭区间[-1,1]上是一致收敛到Cauchy型主值积分φ(wf,x)的,同时给出它的误差界.     

ON THE ESTIMATION OF GENERALIZED LEBESGUE CONSTANT AND MODULUS OF GENERALIZED SINGULAR QUADRATURE FORMULAS AND ITS APPLICATION

This article, first gives the estimaties of two modulus, namely, generalized Lebesgue constant and modulus of generalized singular integral quadrature formulas, then applies them to obtain the error bounds of the operator BLmp to the operator B.     

A fast Fourier-Galerkin method for solving integral equations of second kind with weakly singular kernels

We propose in this paper a convenient way to compress the dense matrix representation of a compact integral operator with a weakly singular kernel under the Fourier basis. This compression leads to a sparse matrix with only ${\mathcal{O}}(n\log n)$ number of nonzero entries, where 2n+1 denotes the order of the matrix. Based on this compression strategy, we develop a fast Fourier-Galerkin method for solving second kind integral equations with weakly singular kernels. We prove that the approximate order of the truncated equation remains optimal and that the spectral condition number of the coefficient matrix of the truncated linear system is uniformly bounded. Furthermore, we develop a fast algorithm for solving the corresponding truncated linear system, which preserves the optimal order of the approximate solution with only ${\mathcal{O}}(n\log^{2}n)$ number of multiplications required. Numerical examples complete the paper.     

Bifurcation of Limit Cycles for 3D Lotka-Volterra Competitive Systems

Bifurcation of limit cycles is discussed for three-dimensional Lotka-Volterra competitive systems. A recursion formula for computation of the singular point quantities is given for the corresponding Hopf bifurcation equation. Some new results are obtained for 6 classes 26–31 in Zeeman’s classification, especially, an example with four limit cycles in class 29 is given for the first time. The algorithm applied here is effective for solving the above general cyclicity.     

A Legendre-Galerkin method for solving general Volterra functional integral equations

We propose in this paper a fully discrete Legendre-Galerkin method for solving general Volterra functional integral equations. The focus of this paper is the stability analysis of this method. Based on this stability result, we prove that the approximation equation has a unique solution, and then show that the Legendre-Galerkin method gives the optimal convergence order \(\mathcal {O}(n^{-m})\), where m denotes the degree of the regularity of the exact solution and n+1 denotes the dimensional number of the approximation space. Moreover, we establish that the spectral condition constant of the coefficient matrix relative to the corresponding linear system is uniformly bounded for sufficiently large n. Finally, we use numerical examples to confirm the theoretical prediction.