一种广义周期Besov类的多元周期多项式样条逼近

本文证明多元多项式周期样条空间是某些多元周期光滑函数类的关于Kolmogorov n-宽度的弱渐近极子空间．给出了广义周期Besov类的一种推广，得到了空间元素的一种表示定理，不仅给出了一种多元周期多项式样条算子．而且证明了所得的结果．     

代数体函数的因子分解

本文阐述了代数体函数的因子分解之概念,并讨论了周期代数体函数与非常数多项式的和、积之因子分解。证明有穷下级周期整代数体函数与非常数多项式之和是左素的。     

一类三次多项式微分系统的周期解

根据Mironenko的反射函数理论,给出一种利用多项式方程探讨三次多项式微分系统周期解的几何性质的新方法.该文首先研究一类系统具有满足特定关系式的反射函数的结构,由此建立三次多项式微分系统与多项式方程之间的解的对应关系,然后利用此对应关系探讨三次多项式微分系统的周期解的几何性质.     

二次多项式微分系统的广义反射函数

利用广义反射函数理论,讨论多项式微分系统的广义反射函数的结构形式.并利用所得结论探讨二次多项式微分系统的周期解的几何性质.     

双周期缺项插值多项式的平均逼近阶

本文首先对双周期缺项插值多项式得到了一个不等式,它是Birkhoff插值的不等式的推广.然后,应用这个不等式研究双周期缺项插值多项式平均逼近A(|z|≤1)中的函数得到了阶的估计.最后,还得到了一般的双周期缺项插值多项式收敛性的结果.     

周期映射单调性的新证法

研究方程d2xdt2 + g(x)= 0 周期解的周期映射,给出了当g(x)为二次多项式时其周期单调的新证法.     

一类拟齐次多项式中心的极限环个数

考虑一类具有全局中心的(m,1)型拟齐次多项式平面微分系统,通过探讨阿贝尔积分的零点个数,分别研究该系统在n次多项式和在(n,1)型拟齐次多项式扰动下,从中心的周期环域分支出来的极限环个数,给出了这些个数的上界并证明它们是可达的.     

二次微分系统的反射函数及其周期解

本文给出了二镒多项式微分系统具有满足特定关系式的反射函数和存在周期解的充要条件，以及在此条件下反射函数的具体表达式及周期解的稳定性态。     

周期映射单调性的新证法

研究方程d2x dr2 g(x)=o周期解的周期映射,给出了当g(x)为二次多项式时其周期单调的新证法．     

环Z/(m)上线性递归序列的若干特性

本文研究 Z/(m)上线性递归序列的特征多项式的理想。得出了其理想的结构及周期.     

LIMIT CYCLES OF QUARTIC AND QUINTIC POLYNOMIAL DIFFERENTIAL SYSTEMS VIA AVERAGING THEORY

We study the maximum number of limit cycles that can bifurcate from the period annulus surrounding the origin of a class of cubic polynomial differential systems using the averaging theory. More precisely,we prove that the perturbations of the period annulus of the center located at the origin of a cubic polynomial differential system,by arbitrary quartic and quintic polynomial differential systems,there respectively exist at least 8 and 9 limit cycles bifurcating from the periodic orbits of the period annu...     

Multi-particle dynamical systems and polynomials

Polynomial dynamical systems describing interacting particles in the plane are studied. A method replacing integration of a polynomial multi-particle dynamical system by finding polynomial solutions of partial differential equations is introduced. The method enables one to integrate a wide class of polynomial multi-particle dynamical systems. The general solutions of certain dynamical systems related to linear second-order partial differential equations are found. As a by-product of our results, new families of orthogonal polynomials are derived.     

Planar polynomial vector fields having a polynomial first integral can be obtained from linear systems

We consider in this work planar polynomial differential systems having a polynomial first integral. We prove that these systems can be obtained from a linear system through a polynomial transformation of variables.     

Polynomial first integrals of quadratic vector fields

We classify all quadratic polynomial differential systems having a polynomial first integral, and provide explicit normal forms for such systems and for their first integrals.     

微分多项式系统的近微分特征列集

本文对微分多项式系统的近微分特征列集与微分特征列集之间的一些关系进行了研究,给出了在某些条件下近微分特征列集是微分特征列集的结论,从而对微分多项式系统特征列集理论（吴方法）进行了改进,并且建立的算法较大地提高了计算微分特征列集的效率.     

Integrability and solvability of polynomial Liénard differential systems

We provide the necessary and sufficient conditions of Liouvillian integrability for Liénard differential systems describing nonlinear oscillators with a polynomial damping and a polynomial restoring force. We prove that Liénard differential systems are not Darboux integrable excluding subfamilies with certain restrictions on the degrees of the polynomials arising in the systems. We demonstrate that if the degree of a polynomial responsible for the restoring force is greater than the degree of a polynomial producing the damping, then a generic Liénard differential system is not Liouvillian integrable with the exception of linear Liénard systems. However, for any fixed degrees of the polynomials describing the damping and the restoring force we present subfamilies possessing Liouvillian first integrals. As a by-product of our results, we find a number of novel Liouvillian integrable subfamilies. In addition, we study the existence of nonautonomous Darboux first integrals and nonautonomous Jacobi last multipliers with a time-dependent exponential factor.     

Polynomial inverse integrating factors for quadratic differential systems

We characterize all the quadratic polynomial differential systems having a polynomial inverse integrating factor and provide explicit normal forms for such systems and for their associated first integrals. We also prove that these families of quadratic systems have no limit cycles.     

Polynomial first integrals for weight-homogeneous planar polynomial differential systems of weight degree 3

Our main result is the classification of all weight-homogeneous planar polynomial differential systems of weight degree 3 having a polynomial first integral.     

Computational bounds on polynomial differential equations

In this paper we study from a computational perspective some properties of the solutions of polynomial ordinary differential equations.We consider elementary (in the sense of Analysis) discrete-time dynamical systems satisfying certain criteria of robustness. We show that those systems can be simulated with elementary and robust continuous-time dynamical systems which can be expanded into fully polynomial ordinary differential equations in Q[π]. This sets a computational lower bound on polynomial ODEs since the former class is large enough to include the dynamics of arbitrary Turing machines.We also apply the previous methods to show that the problem of determining whether the maximal interval of definition of an initial-value problem defined with polynomial ODEs is bounded or not is in general undecidable, even if the parameters of the system are computable and comparable and if the degree of the corresponding polynomial is at most 56.Combined with earlier results on the computability of solutions of polynomial ODEs, one can conclude that there is from a computational point of view a close connection between these systems and Turing machines.     

Limit cycles for two classes of planar polynomial differential systems with uniform isochronous centers

In this article, we study the maximum number of limit cycles for two classes of planar polynomial differential systems with uniform isochronous centers. Using the first-order averaging method, we analyze how many limit cycles can bifurcate from the period solutions surrounding the centers of the considered systems when they are perturbed inside the class of homogeneous polynomial differential systems of the same degree. We show that the maximum number of limit cycles, $m$ and $m+1$, that can bifurcate from the period solutions surrounding the centers for the two classes of differential systems of degree $2m$ and degree $2m+1$, respectively. Both of the bounds can be reached for all $m$.