Kinetical systems—local analysis

The paper gives the answer to the question of the number and qualitative character of stationary points of an autonomous detailed balanced kinetical system.     

On Asymptotic Properties of a Strongly Nonlinear Differential Equation

The paper describes asymptotic properties of a strongly nonlinear system . The existence of an n/2 parametric family of solutions tending to zero is proved. Conditions posed on the system try to be independent of its linear approximation.     

Amplitude–shape approximation as an extension of separation of variables

Separation of variables is a well‐known technique for solving differential equations. However, it is seldom used in practical applications since it is impossible to carry out a separation of variables in most cases. In this paper, we propose the amplitude–shape approximation (ASA) which may be considered as an extension of the separation of variables method for ordinary differential equations. The main idea of the ASA is to write the solution as a product of an amplitude function and a shape function, both depending on time, and may be viewed as an incomplete separation of variables. In fact, it will be seen that such a separation exists naturally when the method of lines is used to solve certain classes of coupled partial differential equations. We derive new conditions which may be used to solve the shape equations directly and present a numerical algorithm for solving the resulting system of ordinary differential equations for the amplitude functions. Alternatively, we propose a numerical method, similar to the well‐established exponential time differencing method, for solving the shape equations. We consider stability conditions for the specific case corresponding to the explicit Euler method. We also consider a generalization of the method for solving systems of coupled partial differential equations. Finally, we consider the simple reaction diffusion equation and a numerical example from chemical kinetics to demonstrate the effectiveness of the method. The ASA results in far superior numerical results when the relative errors are compared to the separation of variables method. Furthermore, the method leads to a reduction in CPU time as compared to using the Rosenbrock semi‐implicit method for solving a stiff system of ordinary differential equations resulting from a method of lines solution of a coupled pair of partial differential equations. The present amplitude–shape method is a simplified version of previous ones due to the use of a linear approximation to the time dependence of the shape function. Copyright © 2007 John Wiley & Sons, Ltd.     

A STABILITY THEOREM FOR A CERTAIN FOURH-ORDER VECTOR DIFFERENTIAL FQUATION

ＡＳＴＡＢＩＬＩＴＹＴＨＥＯＲＥＭＦＯＲＡＣＥＲＴＡＩＮＦＯＵＲＨ－ＯＲＤＥＲＶＥＣＴＯＲＤＩＦＦＥＲＥＮＴＩＡＬＦＱＵＡＴＩＯＮ￥Ａ．Ｍ．Ａ．Ａｂｏｕ－Ｅｌ－Ｅｌａ＆Ａ．Ｉ．Ｓａｄｅｋ（ＦａｃｕｌｔｙｏｆＳｃｉｅｎｃｅ，ＡｓｓｉｕｔＵｎｉｖｅｒｓｉ...     

ASYMPTOTIC BEHAVIOUR OF THE SOLUTIONS OF A CERTAIN FOURTH-ORDER DIFFERENTIAL EQUATION

The present paper establishes sufficient conditions for the uniformly bounded of any solution of (1.1) and which tend to zero as t → ∞.     

关于一类带有慢变系数的二阶微分方程的渐近解

本文研究一类带有慢变系数的二阶常微分方程解的渐近展开式.指出已有工作的不足,利用改进的多重尺度法改进和拓广了文献[1～4]的结果.     

Special symmetric periodic solutions of differential systems with distributed delay

We discuss the existence of periodic solutions to a system of differential equations with distributed delay which shows a certain type of symmetry. For this, such solutions are related to the solutions of a system of second-order ordinary differential equations.     

Adaptive Model Reduction for Chemical Kinetics

An adaptive model reduction algorithm is proposed for systems of ODEs from chemical kinetics. Its goal is to provide an accurate approximation to the solution of these systems faster than could be obtained through straightforward numerical integration. The algorithm approximates a system with a sequence of reduced models, each one appropriate to the dynamics of the system during a period of the trajectory. Reduced models are identical to the original system except for the deletion of some chemical reactions. This saves the cost of computing unimportant reaction coefficients. Both the reduced models and the durations for which they are used are selected adaptively in order to efficiently yield an accurate approximate solution. The performance of the algorithm is assessed through numerical experiments.     

Time delays in dyadic interactions on the example of relations between optimists and pessimists

In this paper, a delayed model of interactions between two actors in the context of their internal optimism and pessimism is studied. Considered model is based on the model proposed earlier in the context of romantic relationships. With the use of the system of nonlinear delay differential equations, we describe the change of emotions of two actors. Delays in the inertial component and in the influence function are introduced, and their influence on the system dynamics is investigated focusing on most beneficial meetings for actors. Finally, the modified systems are compared with the nondelayed case, and results are illustrated by numerical solutions for particular investigated scenarios.     

Nonoscillation theorems for second order nonlinear differential equations

We prove nonoscillation theorems for the second order Emden-Fowler equation (E): , , where and . It is shown that when is nondecreasing for any and is bounded above, then (E) is nonoscillatory. This improves a well-known result of Belohorec in the sublinear case, i.e. when and .

     

带转点的三阶常微分方程边值问题的渐近解

研究带转点的三阶常微分方程的边值问题,其中f(x;0)在(-a,b)具有多个多重零点。给出边值问题出现共振的必要条件,求得其一致有效渐近解和余项估计。     

A universal functional equation

It is shown that the S-chains solving Rubel's universal fourth-order differential equation also satisfy a third-order functional equation.

     

Nonlinear eigenvalue problem for second-order Hamiltonian systems

The nonlinear self-adjoint eigenvalue problem for a Hamiltonian system of two ordinary differential equations is examined under the assumption that the matrix of the system is a monotone function of the spectral parameter. Certain properties of eigenvalues that were previously established by the authors for Hamitonian systems of arbitrary order are now worked out in detail and made more precise for the above system. In particular, a single second-order ordinary differential equation is analyzed.     

General nonlinear self-adjoint eigenvalue problem for systems of ordinary differential equations

The general nonlinear self-adjoint eigenvalue problem for systems of ordinary differential equations is considered. A method is proposed for reducing the problem to one for a Hamiltonian system. Results for Hamiltonian systems previously obtained by the authors are extended to this system.     

On transformations z(t) = y(ϕ(t)) of ordinary differential equations

The paper describes the general form of an ordinary differential equation of the order n + 1 (n 1) which allows a nontrivial global transformation consisting of the change of the independent variable. A result given by J. Aczél is generalized. A functional equation of the form where are given functions, is solved on .     

Remark to transformations of linear differential and functional-differential equations

For linear differential and functional-differential equations of the n-th order criteria of equivalence with respect to the pointwise transformation are derived.     

On certain properties of a nonlinear eigenvalue problem for Hamiltonian systems of ordinary differential equations

Properties of the eigenvalues are examined in a nonlinear self-adjoint eigenvalue problem for linear Hamiltonian systems of ordinary differential equations. In particular, it is proved that, under certain assumptions, every eigenvalue is isolated and there exists an eigenvalue with any prescribed index.     

Limit cycles for cubic systems with a symmetry of order 4 and without infinite critical points

In this paper we study those cubic systems which are invariant under a rotation of radians. They are written as where is complex, the time is real, and , are complex parameters. When they have some critical points at infinity, i.e. , it is well-known that they can have at most one (hyperbolic) limit cycle which surrounds the origin. On the other hand when they have no critical points at infinity, i.e. there are examples exhibiting at least two limit cycles surrounding nine critical points. In this paper we give two criteria for proving in some cases uniqueness and hyperbolicity of the limit cycle that surrounds the origin. Our results apply to systems having a limit cycle that surrounds either 1, 5 or 9 critical points, the origin being one of these points. The key point of our approach is the use of Abel equations.