On a spline collocation method for a singularly perturbed problem

We consider a singularly perturbed boundary value problem with two small parameters. The problem is numerically treated by a quadratic spline collocation method. The suitable choice of collocation points provides the inverse monotonicity enabling utilization of barrier function method in the error analysis. Numerical results give justification of the proposed method. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On a method for constructing one-frequency solutions of a nonlinear wave equation

A method for constructing one-frequency solutions of nonlinear wave equations is suggested. This approach is based on a modified representation of asymptotic expansions by using special periodic Atebfunctions. This method makes it possible to obtain approximate solution of the problem under consideration without difficulty. L'viv Polytechnic Institute, L'viv. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 6, pp. 782–784, June 1994.     

Numerical method for a singularly perturbed convection-diffusion problem with delay

This paper deals with the singularly perturbed boundary value problem for a linear second-order delay differential equation. For the numerical solution of this problem, we use an exponentially fitted difference scheme on a uniform mesh which is accomplished by the method of integral identities with the use of exponential basis functions and interpolating quadrature rules with weight and remainder term in integral form. It is shown that one gets first order convergence in the discrete maximum norm, independently of the perturbation parameter. Numerical results are presented which illustrate the theoretical results.     

On one method for the analysis of the Cauchy problem for a singularly perturbed inhomogeneous second-order linear differential equation

A sequence converging to the solution of the Cauchy problem for a singularly perturbed inhomogeneous second-order linear differential equation is constructed. This sequence is also asymptotic in the sense that the deviation (in the norm of the space of continuous functions) of its nth element from the solution of the problem is proportional to the (n + 1)th power of the perturbation parameter. A similar sequence is constructed for the case of an inhomogeneous first-order linear equation, on the example of which the application of such a sequence to the justification of the asymptotics obtained by the method of boundary functions is demonstrated.     

On a recurrence method for solving a singularly perturbed Cauchy problem for a second order equation

In the present article, the method of deviating argument is applied to solving a singularly perturbed Cauchy problem for an ordinary differential equation of the second order with variable coefficients.     

A uniform finite element method for a conservative singularly perturbed problem

We examine the problem ϵ(p(x)u′) + (q(x)u)′ − r(x)u = f(x) for 0 < x < 1, p>0, q>0, r ⩾ 0; p, q, r and f in C²[0, 1], ϵ in (0, 1], u(0) and u(1) given. Existence of a unique solution u and bounds on u and its derivatives are obtained. Using finite elements on an equidistant mesh of width h we generate a tridiagonal difference scheme which is shown to be uniformly second order accurate for this problem (i.e., the nodal errors are bounded by Ch², where C is independent of h and ϵ). With a natural choice of trial functions, uniform first order accuracy is obtained in the L^∞(0, 1) norm. Using trial functions which interpolate linearly between the nodal values generated by the difference scheme gives uniform first order accuracy in the L¹(0, 1) norm.     

A finite element method for a singularly perturbed boundary value problem

Summary We examine the problem:u+a(x)u–b(x)u=f(x) for 0<x<1,a(x)>0,b(x)>, ² = 4>0,a, b andf inC ² [0, 1], in (0, 1],u(0) andu(1) given. Using finite elements and a discretized Green's function, we show that the El-Mistikawy and Werle difference scheme on an equidistant mesh of widthh is uniformly second order accurate for this problem (i.e., the nodal errors are bounded byCh ², whereC is independent ofh and ). With a natural choice of trial functions, uniform first order accuracy is obtained in theL (0, 1) norm. On choosing piecewise linear trial functions (hat functions), uniform first order accuracy is obtained in theL ¹ (0, 1) norm.     

Asymptotic method for solving the time-optimal control problem for a nonlinear singularly perturbed system

The time-optimal control problem for a nonlinear singularly perturbed system with multidimensional controls bounded in the Euclidean norm is considered. An algorithm for constructing asymptotic approximations to its solution is proposed. The main advantage of the algorithm is that the original optimal control problem decomposes into two unperturbed problems of lower dimensions.     

Multifrequency oscillations of singularly perturbed systems

We consider a system of differential equations that consists of two parts, a regularly perturbed and a singularly perturbed one. We assume that the matrix of the linear part of the regularly perturbed system has pure imaginary eigenvalues, while the matrix of the singularly perturbed part is hyperbolic; i.e., all of its eigenvalues have nonzero real parts.     

The p-version of the finite element method for a singularly perturbed boundary value problem

The p-version of the finite element method is applied to solve the singularly perturbed two-point boundary value problem with or without turning point. With the special choice of mesh points, global error estimates are derived. In some cases, the exponential rate of convergence is obtained. Some numerical results are given to show the performance of the proposed method.     

On the number of interior peak solutions for a singularly perturbed Neumann problem

We consider the following singularly perturbed Neumann problem: where Δ = Σ ?²/?x is the Laplace operator, ? > 0 is a constant, Ω is a bounded, smooth domain in ?^N with its unit outward normal ν, and f is superlinear and subcritical. A typical f is f(u) = u^p where 1 < p < +∞ when N = 2 and 1 < p < (N + 2)/(N ? 2) when N ≥ 3. We show that there exists an ?₀ > 0 such that for 0 < ? < ?₀ and for each integer K bounded by where α_{N, Ω, f} is a constant depending on N, Ω, and f only, there exists a solution with K interior peaks. (An explicit formula for α_{N, Ω, f} is also given.) As a consequence, we obtain that for ? sufficiently small, there exists at least [α_{N, Ωf}/?^N (|ln ?|)^N] number of solutions. Moreover, for each m ∈ (0, N) there exist solutions with energies in the order of ?^N?m. © 2006 Wiley Periodicals, Inc.     

On a domain decomposition algorithm for a singularly perturbed reaction-diffusion problem

This paper deals with an iterative algorithm for domain decomposition applied to the solution of a singularly perturbed reaction-diffusion problem. This algorithm is based on finite difference domain decomposition approach and suitable for parallel computing. Convergence properties of the algorithm are established. Numerical results for a test singularly perturbed problem are presented.     

A parameter-uniform numerical method for a singularly perturbed two parameter elliptic problem

In this paper, a class of singularly perturbed elliptic partial differential equations posed on a rectangular domain is studied. The differential equation contains two singular perturbation parameters. The solutions of these singularly perturbed problems are decomposed into a sum of regular, boundary layer and corner layer components. Parameter-explicit bounds on the derivatives of each of these components are derived. A numerical algorithm based on an upwind finite difference operator and a tensor product of piecewise-uniform Shishkin meshes is analysed. Parameter-uniform asymptotic error bounds for the numerical approximations are established.     

On higher-dimensional contrast structure of singularly perturbed Dirichlet problem

In this paper,we address the existence and asymptotic analysis of higher-dimensional contrast structure of singularly perturbed Dirichlet problem.Based on the existence,an asymptotical analysis of a steplike contrast structure (i.e.,an internal transition layer solution) is studied by the boundary function method via a proposed smooth connection.In the framework of this paper,we propose a first integral condition,under which the existence of a heteroclinic orbit connecting two equilibrium points is ensured in a higher-dimensional fast phase space.Then,the step-like contrast structure is constructed,and the internal transition time is determined.Meanwhile,the uniformly valid asymptotical expansion of such an available step-like contrast structure is obtained.Finally,an example is presented to illustrate the result.     

Parameter-uniform numerical method for singularly perturbed convection-diffusion problem on a circular domain

A linear singularly perturbed elliptic problem, of convection-diffusion type, posed on a circular domain is examined. Regularity constraints are imposed on the data in the vicinity of the two characteristic points. The solution is decomposed into a regular and a singular component. A priori parameter-explicit pointwise bounds on the partial derivatives of these components are established. By transforming to polar co-ordinates, a monotone finite difference method is constructed on a piecewise-uniform layer-adapted mesh of Shishkin type. Numerical analysis is presented for this monotone numerical method. The numerical method is shown to be parameter-uniform. Numerical results are presented to illustrate the theoretical error bounds established.     

Uniform error estimates in the finite element method for a singularly perturbed reaction-diffusion problem

Consider the problem with homogeneous Neumann boundary condition in a bounded smooth domain in . The whole range is treated. The Galerkin finite element method is used on a globally quasi-uniform mesh of size ; the mesh is fixed and independent of .

A precise analysis of how the error at each point depends on and is presented. As an application, first order error estimates in , which are uniform with respect to , are given.

     

Superconvergence analysis of a finite element method for a two-parameter singularly perturbed problem

We consider a singularly perturbed elliptic problem with two small independent parameters and its discretization by a finite element method using piecewise bilinear elements on a layer-adapted mesh. We analyze superconvergence property of the method as well as a postprocessing technique which yields more accurate discrete solution. Numerical tests confirm our theoretical results.     

On one mathematical problem in the theory of nonlinear oscillations

We consider one mathematical problem that was discussed by the author and A. M. Samoilenko at the Third International Conference on the Theory of Nonlinear Oscillations (Transcarpathia, 1967). __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 60, No. 1, pp. 56–62, January, 2008.