Transformations between discrete-time and continuous-time algebraic Riccati equations

We introduce a transformation between the discrete-time and continuous-time algebraic Riccati equations. We show that under mild conditions the two algebraic Riccati equations can be transformed from one to another, and both algebraic Riccati equations share common Hermitian solutions. The transformation also sets up the relations about the properties, commonly in system and control setting, that are imposed in parallel to the coefficient matrices and Hermitian solutions of two algebraic Riccati equations. The transformation is simple and all the relations can be easily derived. We also introduce a generalized transformation that requires weaker conditions. The proposed transformations may provide a unified tool to develop the theories and numerical methods for the algebraic Riccati equations and the associated system and control problems.     

Use of an orthoexponential transformation in the study of the non-stationary equations of thermoelasticity and thermoviscoelasticity

A system of orthoexponential polynomials (OEP) orthogonal in the interval t ε [0, ∞) representing a special case of the orthoexponential Jacobi polynomials /1/ is studied. It is proposed to use the OEP as the kernels of an integral transformation (the OEP transformation) in time, since, compared with Laplace transformations, its use simplifies the procedure for obtaining the originals of the quantities required. The OEP transformation is used to solve the non-stationary equations of thermoelasticity and thermoviscoelasticity. The initial equations are reduced to the corresponding systems of ordinary triangular differential equations, and their general solutions are constructed.     

Application to differential transformation method for solving systems of differential equations

In this paper, we present an analytical solution for different systems of differential equations by using the differential transformation method. The convergence of this method has been discussed with some examples which are presented to show the ability of the method for linear and non-linear systems of differential equations. We begin by showing how the differential transformation method applies to a non-linear system of differential equations and give two examples to illustrate the sufficiency of the method for linear and non-linear stiff systems of differential equations. The results obtained are in good agreement with the exact solution and Runge–Kutta method. These results show that the technique introduced here is accurate and easy to apply.     

压电材料Ⅰ型裂纹动态问题的对偶方程组及其求解

首先引入势函数,用势函数表示压电材料的基本微分方程,并采用Laplace变换、半无限对称Fourier正弦变换和Fourier余弦变换,对微分方程进行变换和初步求解;然后通过Fourier反演和引入边界条件,建立了二维压电材料动态裂纹问题的对偶方程组; 再根据Bessel函数性质, 利用Abel型积分方程及其反演,将对偶方程组化为第二类Fredholm积分方程组．结果表明,方法是可行的,可以成为研究此类问题的一种有效方法．     

Characteristic decompositions and interactions of rarefaction waves of 2-D Euler equations

This paper is concerned with classical solutions to the interaction of two arbitrary planar rarefaction waves for the self-similar Euler equations in two space dimensions. We develop the direct approach, started in Chen and Zheng (in press) [3], to the problem to recover all the properties of the solutions obtained via the hodograph transformation of Li and Zheng (2009) [14]. The direct approach, as opposed to the hodograph transformation, is straightforward and avoids the common difficulties of the hodograph transformation associated with simple waves and boundaries. The approach is made up of various characteristic decompositions of the self-similar Euler equations for the speed of sound and inclination angles of characteristics.     

Nonlocal symmetries and formulae for generation of solutions for a class of diffusion-convection equations

New formulae of nonlocal nonlinear superposition and generation of solutions are proposed for nonlinear diffusion-convection equations which are linearizable or are invariant with respect to a generalized hodograph transformation or connected by this transformation. We study in what particular ways additional Lie symmetries of diffusion-convection equations induce nonlocal symmetries of equations obtained from the initial ones by nonlocal transformations. The formulae derived are used for the construction of exact solutions.     

Exact solutions of some mixed problems of uncoupled thermoelasticity for a truncated hollow circular cone with a groove along the generatrix

An elastic body of finite dimensions in the form of a truncated hollow circular cone with a groove along the generatrix is considered. The uncoupled problem of thermoelasticity is formulated for this body for different types of boundary conditions on all the surfaces. These are the conditions for specifying the displacements or sliding clamping on surfaces with fixed angular coordinates and the conditions for specifying the stresses on surfaces with a fixed radial coordinate (shear stresses are assumed to be zero). It is assumed that the temperature is a specified function of all the spherical coordinates. Some auxiliary functions, related to the displacements, are introduced first, and equations for these functions are then derived using Lamé's equations. A finite integral Fourier transformation with respect to one of the angular variables is then employed. After this, by solving certain Sturm-Liouville problems, a new integral transformation is constructed and is applied to the equations with respect to the other angular variable. As a result a one-dimensional system of differential equations is obtained, to solve which an integral Mellin transformation is employed in a special way. Finally, exact solutions of some problems of thermoelasticity are constructed in series for this body.     

Modified integral current methods in electrodynamics of nonhomogeneous media

The main difficulty in numerical solution of integral equations of electrodynamics is associated with the need to solve a high-order system of linear equations with a dense matrix. It is therefore relevant to develop numerical methods that lead to linear equation systems of lower order at the cost of more complex evaluation of the coefficients. In this article we propose a method for solving linear equations of electrodynamics which is a modification of the integral current method. The main distinctive feature of the proposed method is double integration of the electric Green’s tensor in the process of algebraization of the original integral equation. The solutions of the system of linear equations are thus integral means of the electric field inside the anomaly constructed by the proposed transformation formula. We prove convergence and derive error bounds for both the solution of the integral equation and the electromagnetic field components evaluated from approximate transformation formulas.     

变形色散水波方程的Auto-Backlund变换、多孤子解和有理分式解

利用未知数变换并借助Ｍａｔｈｅｍａｔｉｃａ软件,给出了变形色散水波方程的Ａｕｔｏ－Ｂａｅｃｋｌｕｎｄ变换以及它与热传导方程和线性方程之间的Ｄａｒｂｏｕｘ变换。进而用此变换,获得了变形色散水波方程的多孤子解,有理分式解及其他精确解。这种思路也适用于其它的非线性方程。     

Higher-order Darboux transformations with foreign auxiliary equations and equivalence with generalized Darboux transformations

We show that a recently developed modified Darboux transformation that uses foreign auxiliary equations, can be unified with the Darboux transformation for generalized Schrödinger equations. As a consequence of this unification, we obtain explicit Darboux transformations with foreign auxiliary equations of arbitrary order.     

Darboux transformation and explicit solutions for two integrable equations

A new N-fold Darboux transformation for two integrable equations is constructed with the help of a gauge transformation for the spectral problem proposed by Qiao [Z.J. Qiao, Phys. Lett. A 192 (1994) 316-322]. By the Darboux transformation, explicit soliton and multi-soliton solutions for the two equations are obtained. In particular, soliton and complexiton solutions are shown through some figures.     

Group method analysis of melting effect on MHD mixed convection flow from radiate vertical plate embedded in a saturated porous media

The linear transformation group approach is developed to simulate problem of hydromagnetic heat transfer by mixed convection along vertical plate in a liquid saturated porous medium in the presence of melting and thermal radiation effects for opposing external flow. The application of a one-parameter transformation group reduces the number of independent variables by one so that the governing partial differential equations with the boundary conditions reduce to an ordinary differential equations with appropriate corresponding conditions. The Runge-Kutta shooting method is used to solve the determining equations of the set of nonlinear ordinary differential equations. are presented in the form of the temperature and flow fields in the melting region within the boundary layer for different parameters entering into the analysis. Also the effects of the pertinent parameters on the rate of the heat transfer in terms of the local Nusselt number at the solid–liquid interface are also discussed.     

单向拉伸镍钛合金带从奥氏体到马氏体的相变分析

单向拉伸镍钛合金带中从奥氏体到马氏体的相变已在实验中观测到,并被看作为局部变形进行了数值模拟．该文采用相变理论对其进行分析,考虑了两相界面处变形梯度的跳跃以及Maxwell关系,导出了相变的控制方程．相变分析归结为寻求载荷的最小值,使在该值下控制方程具有唯一的、物理上可以接受的实数解．控制方程被数值求解,证明了该唯一解确实存在．相变的Maxwell 应力,马氏体相与奥氏体相内的应力与应变,以及相边界的倾角都可求出,并与实验所观测到的结果相吻合．     

Solution of Functional Equations of the First and Second Kind Whose Kernels are Transformations with Orthogonal Coordinates

The notion of coordinates for a linear continuous transformation of a Hilbert space is introduced. A complete solvability theory of functional equations of the first and second kind whose kernels have orthogonal coordinates is constructed, and all solutions of such equations are obtained. In particular, this theory is applicable to equations with compact operators. Bibliography: 5 titles.     

On mean periodic functions

Summary. Mean periodic functions play an important role in the theory of functional equations. Based on fundamental results on spectral synthesis it is possible to introduce a Fourier type transformation for mean periodic functions on the real line. This transformation can be used to solve convolution-type functional equations. It turns out that this transformation has a close relation to some kind of conditional expectation.     

The method of potential functions in problems of the theory of elasticity for bodies with a defect

The method of potential functions using a Fourier transformation in the class of slowly increasing distributions, corresponding to the classical method of complex potentials, is proposed for solving well-known problems of the theory of elasticity for bodies with a defect. It is shown that when a Fourier transformation with respect to all the spatial variables is used, the solution of the dynamic problem of the theory of elasticity can also be represented in terms of a jump in the stresses and displacements at the defect. The correctness of the transformed problem is considered (in terms of an analogue of the Lopatinskii condition). The solution of the system of Helmholtz equations, to which the system of Lamé equations is reduced in the case of the two-dimensional dynamic problem, is expressed in terms of the jump in the stresses and displacements at the defect as a result of solving the corresponding singular integral equations.     

Oscillation criteria for certain third-order variable delay functional dynamic equations on time scales

The oscillation of certain third-order nonlinear variable delay functional dynamic equations with nonlinear neutral on time scales is discussed in this article. By using the generalized Riccati transformation and a lot of inequality techniques, some new oscillation criteria for the equations are established. Many of the results are new for the corresponding third-order difference equations and differential equations are as special cases. Some examples are given to illustrate the importance of our results.     

变形浅水波方程组的一个非线性变换及其应用

本文用齐次平衡方法导出了变形浅水波方程组的一个非线性变换,借助该变换得到了方程组的精确孤立波解。     

Differential transformation approach to thermal conductive problems with discontinuous boundary condition

A two-dimensional differential transformation method is employed to reduce the partial differential equations of the non-continuous thermal conductive boundary value problem to a Taylor series in a polynomial form. The partial differential equations are solved by the two-dimensional T-spectra method of differential transformation and by the use of trial initial polynomial conditions. The investigative parameters include the time-step of the differential transformation and the number of sub-domain segments. The numerical simulation results indicate that the proposed approach using the two-dimensional T-spectra method of differential transformation is applicable to the solution of non-continuous thermal conductive boundary value problems.     

应用(G'/G~2)-展开法求解非线性分数阶微分方程（英文）

In the current paper, based on fractional complex transformation, the GG2-expansion method which is used to solve differential equations of integer order is developed for finding exact solutions of nonlinear fractional differential equations with Jumarie's modified Riemann-Liouville derivative. And then, time-fractional Burgers equation and space-fractional coupled Konopelchenko-Dubrovsky equations are provided to show that this method is effective in solving nonlinear fractional differential equations.