On Optimization of Direct Methods of Solving Weakly Singular Integral Equations

We find the exact order of optimal accuracy of adaptive direct methods for the approximate solution of integral equations with potential-type kernels and for Peierls integral equations arising in transport theory. Moreover, for these equations we indicate the adaptive direct method of optimal order.     

Positive solutions of systems of singular Hammerstein integral equations with applications to semilinear elliptic equations in annuli

The existence of multiple positive solutions of systems of singular Hammerstein integral equations is studied, where the nonlinearities involved are allowed to have singularities in their second variables and satisfy weaker conditions involving the first eigenvalues of the corresponding linear Hammerstein integral operators. Such systems contain some mathematical models arising in science and engineering. Applications are given to the existence of multiple positive radial solutions of systems of semilinear singular elliptic equations in annuli on which, to the best of our knowledge, there has been little study.     

Conditions for well-posedness of integral models of some living systems

We study the existence, uniqueness, and nonnegativity of solutions of a family of delay integral equations used in mathematical models of living systems. Conditions ensuring these properties of solutions on an infinite time interval are obtained. The continuous dependence of solutions on the initial data on finite time intervals is analyzed. Special cases in the form of delay differential and integro-differential equations arising in population dynamics models are presented.     

The conditioning of some projection methods for Fredholm and singular integral equations

We consider a general scheme for bounding the condition number of matrices arising from projection methods for solving linear operator equations. Applications are given for some Galerkin and collocation methods for Fredholm and Cauchy singular integral equations.     

Numerical solutions of integral and integro-differential equations using Legendre polynomials

In this paper, a finite Legendre expansion is developed to solve singularly perturbed integral equations, first order integro-differential equations of Volterra type arising in fluid dynamics and Volterra delay integro-differential equations. The error analysis is derived. Numerical results and comparisons with other methods in literature are considered.      

On Boundary Integral Equations of the First Kind

A large class of elliptic boundary value problems in elasticity and fluid mechanics can be reduced to systems of boundary integral equations of the first kind. This paper summarizes some of the basic concepts and results concerning the mathematical foundation of boundary element methods for treating such a class of boundary integral equations.     

一些高振荡积分、高振荡积分方程的高性能计算

电磁、声波散射问题的研究涉及一类数学物理问题, 此类问题具有深刻的理论价值和重要的应用背景, 亟待解决. 高振荡微分、积分方程是刻画这些问题的重要的数学模型, 其数值计算存在许多挑战性研究课题. 本文从积分方程解法角度出发, 综述了求解这类高振荡问题的一些最新进展, 特别是针对广义Fourier 变换、Bessel 变换的高效算法、高振荡核Volterra 积分方程的数值解法作了详细介绍. 这些数值方法共有特点是振荡频率越高算法精度愈高, 且可望为电磁计算的研究提供一些新的高效算法.     

Dual integral equations related to the kontorovich-lebedev transform : PMM vol. 38, n 6, 1974, pp. 1090–1097

We study the dual integral equations related to the Kontorovich-Lebedev integral transforms arising in the course of solution of the problems of mathematical physics, in particular of the mixed boundary value problems for the wedge-shaped regions. We show that the solutions of these equations can be expressed in quadratures, using the auxilliary functions satisfying the integral Fredholm equation of second kind with a symmetric kernel.At present, the dual equations investigated in most detail are those connected with the Fourier and Hankel integral transforms. The results obtained and their applications are given in [1–3]. A large number of papers also deal with the theory and applications of the dual integral equations connected with the Mehler-Fock integral transform and its generalizations [4–11]., The dual integral transforms considered in the present paper belong to a more complex class than those listed above, and so far, no effective solution has been obtained for them. The only relevant results known to the authors are those in [12, 13]. In [12] a method of solving the equations (1.2) is given for a single particular value of the parameter γ = π/2, while in [13] the dual equations of the type under consideration are reduced to a solution of an infinite system of linear algebraic equations.     

Existence, uniqueness and exponential stability of traveling wave solutions of some integral differential equations arising from neuronal networks

The author is concerned with the existence and exponential stability of traveling wave solutions of some integral differential equations arising from neuronal networks. Previous methods do not apply in solving these problems because there is no maximum principle or conservation laws available to the integral differential equations. He applies fixed point theorems to prove the existence of the traveling waves. Then, he makes use of linearization technique as well as eigenvalue functions to study the exponential stability of the waves.     

On the Nyström discretization of integral equations on planar curves with corners

The Nyström method can produce ill-conditioned systems of linear equations when applied to integral equations on domains with corners. This defect can already be seen in the simple case of the integral equations arising from the Neumann problem for Laplace?s equation. We explain the origin of this instability and show that a straightforward modification to the Nyström scheme, which renders it mathematically equivalent to Galerkin discretization, corrects the difficulty without incurring the computational penalty associated with Galerkin methods. We also present the results of numerical experiments showing that highly-accurate solutions of integral equations on domains with corners can be obtained, irrespective of whether their solutions exhibit bounded or unbounded singularities, assuming that proper discretizations are used.     

A numerical method based on hybrid orthonormal Bernstein and improved block-pulse functions for solving Volterra–Fredholm integral equations

This paper deals with the numerical solution of the integral equations of linear second kind Volterra–Fredholm. These integral equations are commonly used in engineering and mathematical physics to solve many of the problems. A hybrid of Bernstein and improved block-pulse functions method is introduced and used where the key point is to transform linear second-type Volterra–Fredholm integral equations into an algebraic equation structure that can be solved using classical methods. Numeric examples are given which demonstrate the related features of the process.     

Numerical solutions of distributed order fractional differential equations in the time domain using the Müntz–Legendre wavelets approach

In this paper, a numerical method is presented to obtain and analyze the behavior of numerical solutions of distributed order fractional differential equations of the general form in the time domain with the Caputo fractional derivative. The suggested method is based on the Müntz–Legendre wavelet approximation. We derive a new operational vector for the Riemann–Liouville fractional integral of the Müntz–Legendre wavelets by using the Laplace transform method. Applying this operational vector and collocation method in our approach, the problem can be reduced to a system of linear and nonlinear algebraic equations. The arising system can be solved by the Newton method. Discussion on the error bound and convergence analysis for the proposed method is presented. Finally, seven test problems are considered to compare our results with other well‐known methods used for solving these problems. The results in the tabulated tables highlighted that the proposed method is an efficient mathematical tool for analyzing distributed order fractional differential equations of the general form.     

用于解析函数复分析的共轭边界元法

由2个共轭的实调和函数构建1个复解析函数,其复分析在应用数学和力学领域具有重要的作用.提出了一个加权残数方程组,证明了该方程组为2个共轭函数的域内控制方程、边界条件和边界上Cauchy Riemann(柯西-黎曼)条件的近似解,等效为复解析函数的逼近方程.在离散空间中,由该加权残数方程分别推导出2个位势问题的直接边界积分方程和1个表示Cauchy-Riemann条件的有限差分方程,随后解决了弱奇异线性方程组的求解难题,并提出用Cauchy积分公式求内点值的方法,从而建立了一种用于复分析的常单元共轭边界元法.最后,用3个算例证明了所提出方法适用于域内或域外的幂函数、指数函数或对数函数形式的解析函数,而且其误差与2维位势问题是同等量级的.     

Asynchronous multisplitting two-stage iterations for systems of weakly nonlinear equations

For the large sparse systems of weakly nonlinear equations arising in the discretizations of many classical differential and integral equations, this paper presents a class of asynchronous parallel multisplitting two-stage iteration methods for getting their solutions by the high-speed multiprocessor systems. Under suitable assumptions, we study the global convergence properties of these asynchronous multisplitting two-stage iteration methods. Moreover, for this class of new methods, we establish their local convergence theories, and precisely estimate their asymptotic convergence factors under some reasonable assumptions when the involved nonlinear mapping is only assumed to be directionally differentiable. Numerical computations show that our new methods are feasible and efficient for parallely solving the system of weakly nonlinear equations.     

Development and Optimization of Randomized Functional Numerical Methods for Solving the Practically Significant Fredholm Integral Equations of the Second Kind

Under study are the randomized algorithms for numerical solution of the Fredholm integral equations of the second kind (from the viewpoint of their application for the practically important problems of mathematical physics). The projection, grid and projection-grid methods are distinguished. Certain advantages of the projection and projection-grid methods are demonstrated (allowing using them for numerical solution of the equations with the integrable singularities in kernels and free terms).     

Mathematical models based on singular integral equations with non-Carleman shift. Analysis of solvability and numerical methods of solution

We consider some examples of systems whose functionality can be described with the help of mathematical models based on singular integral equations with non-Carleman shift. For this type of equations, we have obtained an estimate for the dimension of the kernel of the corresponding operator and proposed numerical methods for both evaluating the dimension of the kernel and constructing solutions.     

Nontrivial solvability of a class of nonlinear integro-differential equations of second order

The article is devoted to the study of nontrivial solvability and the asymptotic behavior of solutions for some classes of nonlinear integro-dofferential equations with a noncompact operator in a special case. Combining special factorization methods with the methods of the theory of linear integral equations of convolution type, we prove existence theorems for these classes of equations. With the help of a priori estimates, we calculate the limits of solutions obtained at infinity. The examples exhibited in the article are of mathematical interest in their own right. They are particular cases of the equations considered and have important applications in quantum mechanics.     

The operator equations of Lippmann–Schwinger type for acoustic and electromagnetic scattering problems in L 2

This article is concerned with the scattering of acoustic and electromagnetic time harmonic plane waves by an inhomogeneous medium. These problems can be translated into volume integral equations of the second kind – the most prominent example is the Lippmann–Schwinger integral equation. In this work, we study a particular class of scattering problems where the integral operator in the corresponding operator equation of Lippmann–Schwinger type fails to be compact. Such integral equations typically arise if the modelling of the inhomogeneous medium necessitates space-dependent coefficients in the highest order terms of the underlying partial differential equation. The two examples treated here are acoustic scattering from a medium with a space-dependent material density and electromagnetic medium scattering where both the electric permittivity and the magnetic permeability vary. In these cases, Riesz theory is not applicable for the solution of the arising integral equations of Lippmann–Schwinger type. Therefore, we show that positivity assumptions on the relative material parameters allow to prove positivity of the arising volume potentials in tailor-made weighted spaces of square integrable functions. This result merely holds for imaginary wavenumber and we exploit a compactness argument to conclude that the arising integral equations are of Fredholm type, even if the integral operators themselves are not compact. Finally, we explain how the solution of the integral equations in L ² affects the notion of a solution of the scattering problem and illustrate why the order of convergence of a Galerkin scheme set up in L ² does not suffer from our L ² setting, compared to schemes in higher order Sobolev spaces.     

On the existence of a solution to a singular integral equation in electromagnetic reflection

For a singular integral equation arising in a modified approach to boundary integral equations for exterior boundary-value problems from the theory of electromagnetic reflection an existence proof is given.     

Numerical solution of stochastic differential problems in the biosciences

Stochastic differential equations (SDEs) models play a prominent role in many application areas including biology, epidemiology and population dynamics, mostly because they can offer a more sophisticated insight through physical phenomena than their deterministic counterparts do. So, suitable numerical methods must be introduced to simulate the solutions of the resulting stochastic differential systems. In this work we take into account both Euler–Taylor expansion and Runge–Kutta-type methods for stochastic ordinary differential equations (SODEs) and the Euler–Maruyama method for stochastic delay differential equations (SDDEs), focusing on the most relevant implementation issues. The corresponding Matlab codes for both SODEs and SDDEs problems are tested on mathematical models arising in the biosciences.