Interlacing of Hurwitz series

In this paper, we introduce the notion of interlacing of Hurwitz series. We begin by reviewing some important properties of the ring of Hurwitz series over a commutative ring A of arbitrary characteristic, and we introduce and investigate properties of the maps exp and log. We show that solutions of linear homogeneous differential equations with constant coefficients from the ring A can be described simply as interlacings of solutions of a first order system of differential equations. We give several examples to illustrate this result, and we conclude by defining and investigating properties of trigonometric functions using interlacings of Hurwitz series.     

An analytical solution for two and three dimensional nonlinear Burgers' equation

This paper derives analytical solutions for the two dimensional and the three dimensional Burgers' equation. The two-dimensional and three-dimensional Burgers' equation are defined in a square and a cubic space domain, respectively, and a particular set of boundary and initial conditions is considered. The analytical solution for the two dimensional Burgers' equation is given by the quotient of two infinite series which involve Bessel, exponential, and trigonometric functions. The analytical solution for the three dimensional Burgers' equation is given by the quotient of two infinite series which involve hypergeometric, exponential, trigonometric and power functions. For both cases, the solutions can describe shock wave phenomena for large Reynolds numbers (R_e ≥ 100), which is useful for testing numerical methods.     

The Crank–Nicolson finite spectral element method and numerical simulations for 2D non-stationary Navier–Stokes equations

In this paper, we first build a semi-discretized Crank–Nicolson (CN) model about time for the two-dimensional (2D) non-stationary Navier–Stokes equations about vorticity–stream functions and discuss the existence, stability, and convergence of the time semi-discretized CN solutions. And then, we build a fully discretized finite spectral element CN (FSECN) model based on the bilinear trigonometric basic functions on quadrilateral elements for the 2D non-stationary Navier–Stokes equations about the vorticity–stream functions and discuss the existence, stability, and convergence of the FSECN solutions. Finally, we utilize two sets of numerical experiments to check out the correctness of theoretical consequences.     

三维坐标转换的两种方法及其比较研究

针对7参数法三维坐标转换问题,对比分析了传统的基于泰勒级数展开的线性模型转换方法和基于罗德里格矩阵的三维坐标转换方法.由于在基于罗德里格矩阵的转换方法中,不需进行三角函数的计算,也不需迭代计算,因而其计算速度更快;而且其解决了线性模型对旋转角大小的限制,不仅适用于小角度的空间直角坐标转换,也能用于大角度的空间坐标转换.实验结果也表明基于罗德里格矩阵的转换方法具有更好的适用性和更高的精度.     

Application of the method of special series to the representation of solutions of the Lin-Reissner-Tsien equation

For the two-dimensional Lin-Reissner-Tsien equation, which describes nonstationary gas flows, we construct new classes of solutions with functional arbitrariness in the form of series in powers of specially chosen functions. Coefficients of such series are found successively as solutions of linear ordinary differential equations or as solutions of linear partial differential equations. The use of special series whose coefficients are determined by linear partial differential equations allowed us to satisfy two given additional boundary conditions exactly. For one class of flows, these coefficients were found in an explicit form from linear equations of the hyperbolic type; for another one, they were found from linear equations of the parabolic type. This circumstance was used to prove the convergence of such series and to study the asymptotics of the solutions constructed. We present results of numerical calculations on nonstationary transonic flow around a wedge.     

Lattice Boltzmann model for two-dimensional generalized sine-Gordon equation

The nonlinear sine-Gordon equation arises in various problems in science and engineering. In this paper, we propose a numerical model based on lattice Boltmann method to obtain the numerical solutions of two-dimensional generalized sine-Gordon equation, including damped and undamped sine-Gordon equation. By choosing properly the conservation condition between the macroscopic quantity $u_t$ and the distribution functions and applying the Chapman-Enskog expansion, the governing equation is recovered correctly from the lattice Boltzmann equation. Moreover, the local equilibrium distribution function is obtained. The numerical results of the first three examples agree well with the analytic solutions, which indicates the lattice Boltzmann model is satisfactory and efficient. Numerical solutions for cases involving the most known from the bibliography line and ring solitons are given. Numerical experiments also show that the present scheme has a good long-time numerical behavior for the generalized sine-Gordon equation. Moreover, the model can also be applied to other two-dimensional nonlinear wave equations, such as nonlinear hyperbolic telegraph equation and Klein-Gordon equation.     

Summation of Some Trigonometric and Schlömilch Series

In this paper we consider trigonometric series in terms of the Riemann zeta function and related functions of reciprocal powers. The obtained closed form formulas we apply to the evaluation of the Riemann zeta function and related functions of reciprocal powers. One can establish recursive relations for them and relations between any two of those functions. These closed formulas enable us also to find sums of some Schlömilch series. We give an example which shows how the convergence of a trigonometric series can be accelerated by applying Krylov's method and our formula (7).     

构造非线性微分差分方程精确解的一种方法

把最近提出的G′/G展开法推广到了非线性微分差分方程,利用该方法成功构造了一种修正的Volterra链和Toda链的双曲函数、三角函数以及有理函数三类涉及任意参数的行波解,当这些参数取特殊值时,可得这两个方程的扭状孤立波解、奇异行波解以及三角函数状的周期波解等.研究结果表明,该算法探讨非线性微分差分方程精确解十分有效、简洁.     

A method for solving partial differential equations using differentiate trigonometric fourier series

A method for representing a function of two variables u (x, y), that is defined in the square σ = [0, π] × [0, π], is presented in the form of a combination of polynomials and differentiable trigonometric series. Such a representation enables problems to be solved in which the unknown function is defined from partial differential equations and has some partial derivatives at the border of the square domain of higher order than the order of the equation. Expansion in a trigonometric series is carried out by a system of functions mx, M = 1, 2, 3 … that is full in [0, π] and in a double series by a system of functions mx sin ifny, m, N = 1,2,3,… that is full in σ. For solving real problems, expansion by such a system of functions can be preferable to expansion by an ordinary trigonometric system of sines and cosines /1, 2/. Using the representation of a function of two variables referred to aboye the problem of the bending of an anisotropic plate with non-uniform boundary conditions is solved.     

New algebraic approaches to classical boundary layer problems

Classical non-steady boundary layer equations are fundamental nonlinear partial differential equations in the boundary layer theory of fluid dynamics. In this paper, we introduce various schemes with multiple parameter functions to solve these equations and obtain many families of new explicit exact solutions with multiple parameter functions. Moreover, symmetry transformations are used to simplify our arguments. The technique of moving frame is applied in the three-dimensional case in order to capture the rotational properties of the fluid. In particular, we obtain a family of solutions singular on any moving surface, which may be used to study turbulence. Many other solutions are analytic related to trigonometric and hyperbolic functions, which reflect various wave characteristics of the fluid. Our solutions may also help engineers to develop more effective algorithms to find physical numeric solutions to practical models.     

Asymptotics of Eigenvalues for a Class of Jacobi Matrices with Limiting Point Spectrum

In this paper, we study a class of Jacobi matrices with very rapidly decreasing weights. It is shown that the Weyl function (the matrix element of the resolvent of the operator) for the class under study can be expressed as the ratio of two entire transcendental functions of order zero. It is shown that the coefficients in the expansion of these functions in Taylor series are proportional to the generating functions of the number of integral solutions defined by certain Diophantine equations. An asymptotic estimate for the eigenvalues is obtained.     

各向异性矩形板自由振动的一般解析解法

根据各向异性矩形薄板自由振动横向位移函数的微分方程建立了一般性的解析解．该一般解包括三角函数和双曲线函数组成的解,它能满足4个边为任意边界条件的问题．还有代数多项式和双正弦级数解,它能满足4个角的边界条件问题．因此,这一解析解可用于精确地求解具有任意边界条件的各向异性矩形卞的振动问题．解中的积分常数可由4边和4角的边界条件来确定．由此得出的齐次线性代数方程系数矩阵行列式等于零可以求得各阶固有频率及其振型,以四边平夹的对称角铺设复合材料迭层板为例进行了计算和讨论．     

A kind of explicit Riemann theta functions periodic waves solutions for discrete soliton equations

In this paper, Riemann theta functions are used to construct one-theta function and two-theta functions solutions to a class of Hirota bilinear equations, such as extended version of the discrete mKdV equation and deautonomization of the two-dimensional Toda lattice equation. To get the Riemann theta function periodic waves solutions (the quasi-periodic solutions), this method is direct and simple which use only the identities of the theta functions.     

Aesthetic fields: a two-dimensional lattice solution satisfying integrability

In our previous paper we obtained examples of lattice solutions to the aesthetic field equations. A drawback with these solutions was that the integrability equations were not satisfied. In this paper we find a solution to the aesthetic field equations which describes a two-dimensional lattice structure. The integrability equations are satisfied in this case. We work within a six-dimensional framework in this paper. Three of the coordinates are real and three of the coordinates are pure imaginary. It is a generalization of the Minkowski version of aesthetic field theory.     

Variable-coefficient Jacobi elliptic function expansion method for (2+1)-dimensional Nizhnik-Novikov-Vesselov equations

In this paper, a variable-coefficient Jacobi elliptic function expansion method is proposed to seek more general exact solutions of nonlinear partial differential equations. Being concise and straightforward, this method is applied to the (2+1)-dimensional Nizhnik-Novikov-Vesselov equations. As a result, many new and more general exact non-travelling wave and coefficient function solutions are obtained including Jacobi elliptic function solutions, soliton-like solutions and trigonometric function solutions. To give more physical insights to the obtained solutions, we present graphically their representative structures by setting the arbitrary functions in the solutions as specific functions.     

A series of complexiton soliton solutions for non-linear Hirota–Satsuma equations using the generalized multiple Riccati equations rational expansion method

In this article, the generalized multiple Riccati equations rational expansion method has been used to construct a series of complexiton soliton solutions for the non-linear Hirota–Satsuma equations. With the help of symbolic computation software as Maple or Mathematica, we obtain many new types of complexiton soliton solutions, i.e. various combination of trigonometric periodic function and hyperbolic function solutions, various combination of trigonometric periodic function and rational function solutions, and various combination of hyperbolic function and rational function solutions.     

Travelling wave solutions of nonlinear evolution equations by using the first integral method

In this paper, we established travelling wave solutions for some (2 + 1)-dimensional nonlinear evolution equations. The first integral method was used to construct travelling wave solutions of nonlinear evolution equations. The travelling wave solutions are expressed by the hyperbolic functions, the trigonometric functions and the rational functions. The first integral method presents a wider applicability for handling nonlinear wave equations.     

Generalized Cauchy Matrix Approach for Lattice Boussinesq-Type Equations

The authors generalize the Cauchy matrix approach to get exact solutions to the lattice Boussinesq-type equations:lattice Boussinesq equation,lattice modified Boussinesq equation and lattice Schwarzian...     

An exponential matrix method for solving systems of linear differential equations

This paper presents an exponential matrix method for the solutions of systems of high‐order linear differential equations with variable coefficients. The problem is considered with the mixed conditions. On the basis of the method, the matrix forms of exponential functions and their derivatives are constructed, and then by substituting the collocation points into the matrix forms, the fundamental matrix equation is formed. This matrix equation corresponds to a system of linear algebraic equations. By solving this system, the unknown coefficients are determined and thus the approximate solutions are obtained. Also, an error estimation based on the residual functions is presented for the method. The approximate solutions are improved by using this error estimation. To demonstrate the efficiency of the method, some numerical examples are given and the comparisons are made with the results of other methods. Copyright © 2012 John Wiley & Sons, Ltd.