论拉普拉斯方程第三边值问题与变分问题的等价性

首先给出了柱坐标系下拉普拉斯方程的第三边值问题,进而证明了拉普拉斯方程的第三边值问题等价于一个泛函变分的极值问题,最后指出了将拉普拉斯方程第三边值问题转换为等价的泛函变分极值问题的好处.     

共振情形下四点泛函边值问题解的存在性

运用Mawhin重合度理论,讨论了一类二阶四点泛函边值问题解的存在性和多解性.分别在非线性项f有界和无界的条件下,获得了此类泛函边值问题解的存在性结果.     

关于二阶线性椭圆型边值问题的变分逆问题

<正> 本文要讨论的问题是,当给定椭圆型微分方程的边值问题以后,是否有其对应的泛函,使得该泛函的“驻值解”,恰好是椭圆型微分方程边值问题的解?如果回答肯定(在一定条件下),则要给出此泛函的具体形式.     

一类奇摄动泛函微分方程边值问题

该文研究一类泛函微分方程边值问题,利用微分不等式理论证明了边值问题解的存在性,并给出了解的一致有效渐近展开式．     

奇异二阶泛函微分方程边值问题的多重正解

本文把ＺｈａｏｌｉＬｉｕ和Ｅｒｂｅ等人关于常微分方程边值问题多重正解的工作推广到二阶奇异混合型泛函微分方程边值问题,证明了所考虑的方程边值问题存在至少两个正解的充分条件。     

一类非线性泛函边值问题的可解性

本文考虑非线性泛函边值问题，利用Ｂｏｒｓｕｋ定理与Ｌｅｒａｙ－Ｓｃｈａｕｄｅｒ不动点定理，得到了上述边值问题的若干可解性结果。     

自共轭常微分方程边值问题与变分问题的等价性

首先给出了自共轭常微分方程及其边值问题,进而证明了自共轭常微分方程边值问题等价于一个泛函变分的极值问题,最后指出了将自共轭常微分方程边值问题转换为等价的泛甬变分极值问题的好处.     

关于一个新泛函的锥拉伸与锥压缩不动点定理及应用

引进了一个新的泛函,它包含了已有的很多类型的泛函.关于此泛函建立了一个泛函形式的锥拉伸与锥压缩不动点定理,并应用此定理研究了一类二阶两点边值问题,得到了该问题至少一个正解的存在性.     

高阶泛函偏微分程边值问题的强迫振动

本文研究一类高阶泛函偏微分方程边值问题的强迫振动性．主要工具是平均技巧，利用它将问题归结于相应的泛函微分不等式的振动性的研究．     

一类奇异泛函微分方程边值问题的多重正解

本文研究一类二阶奇异泛函微分方程边值问题.利用锥理论和不动点指数方法得到了该边值问题至少存在两个正解的结论,推广了文[3]和文[4]的结果.     

微分多项式系统的约化算法理论

本文中，作者推广了纯代数形式的特征列集理论（吴方法）为微分形式的相应理论，即建立了在机器证明了诸多微分问题中非常重要的微分多项式组的约化算法理论。引入了一些新的概念和观点使函数微分（导数）具有直观的代数几何表示。给出了Coherent条件下的特征列集的算法。给出的算法易于在计算机上实现并适合应用于广泛的微分问题，如微分方程对称计算，各种微分关系的自动推理等问题。     

球壳轴对称弯曲问题精确的挠度微分方程及其奇异摄动解

本文提出了球壳轴对称弯曲问题精确的挠度(ω)微分方程和精确的转角(dω/da)微分方程.本文重点研究了挠度微分方程的精度,基本思路是:首先假设边缘效应时经线中面位移u=0,从而建立挠度微分方程,然后再精确地证明挠度微分方程与原来微分方程内力解答完全相同.再精确地证明边缘效应时经线中面位移u=0是精确解.本文给出了挠度微分方程的奇异摄动解,最后验算了平衡条件,证明摄动解求出的内力和外荷载是完全平衡的.这一方面表明摄动解的计算是正确的;另一方面也再二次表明挠度微分方程是精确的微分方程.新微分方程的优点是:1.新微分方程和原来微分方程精度完全相同;2.新微分方程满足的边界条件非常简单;3.新微分方程便于使用摄动解;4.新微分方程可以得到挠度(ω)和转角(dω/da)的表达式.新微分方程使球壳的计算得到很大的简化.本文采用的符号与徐芝纶《弹性力学》第二版下册相同[1].     

Algebraic theory of differential inequalities

We obtain differential-algebraic analogues of some basic theorems of real algebra and semialgebraic geometry. Proofs are based on: a differential version of the real spectrum of a differential ring containing Q; an Artin-Schreier theory for such rings; the model theory of ordered differential fields. Results include: an algebraic characterization of the differential inequalities which are consequences of a given finite set of algebraic differential equations and inequalities; a differential counterpart of the Hormander-Lojasiewicz inequality.     

The ring of differential Fourier expansions

For a fixed prime we prove structure theorems for the kernel and the image of the map that attaches to any differential modular function its differential Fourier expansion. The image of this map, which is the ring of differential Fourier expansions, plays the role of ring of functions on a “differential Igusa curve”. Our constructions are then used to perform an analytic continuation between isogeny covariant differential modular forms on the differential Igusa curves belonging to different primes.     

On One Class of Systems of Differential Equations and on Retarded Equations

We establish a connection between solutions to a broad class of large systems of ordinary differential equations and solutions to retarded differential equations. We prove that solving the Cauchy problem for systems of ordinary differential equations reduces to solving the initial value problem for a retarded differential equation as the number of equations increases unboundedly. In particular, the class of systems under consideration contains a system of differential equations which arises in modeling of multiphase synthesis.     

Construction of differential equation approximations to delay differential equations

A constructive method is presented for obtaining differential equation approximations to general functional delay differential equations. It is shown that the approximating differential equation systems can be used to determine the stability of the functional differential equations     

New examples (and counterexamples) of complete finite-rank differential varieties

Differential algebraic geometry seeks to extend the results of its algebraic counterpart to objects defined by differential equations. Many notions, such as that of a projective algebraic variety, have close differential analogues but their behavior can vary in interesting ways. Workers in both differential algebra and model theory have investigated the property of completeness of differential varieties. After reviewing their results, we extend that work by proving several versions of a “differential valuative criterion" and using them to give new examples of complete differential varieties. We conclude by analyzing the first examples of incomplete, finite-rank projective differential varieties, demonstrating a clear difference from projective algebraic varieties.     

Solving systems of fractional differential equations using differential transform method

This paper presents approximate analytical solutions for systems of fractional differential equations using the differential transform method. The fractional derivatives are described in the Caputo sense. The application of differential transform method, developed for differential equations of integer order, is extended to derive approximate analytical solutions of systems of fractional differential equations. The solutions of our model equations are calculated in the form of convergent series with easily computable components. Some examples are solved as illustrations, using symbolic computation. The numerical results show that the approach is easy to implement and accurate when applied to systems of fractional differential equations. The method introduces a promising tool for solving many linear and nonlinear fractional differential equations.     

Functional differential inequalities and estimation of the Cauchy function of an equation with aftereffect

We consider scalar functional differential inequalities that are used to estimate solutions to differential equations with deviating argument. A theorem on positiveness of the Cauchy function of a differential equation with aftereffect is derived from a theorem on a functional differential inequality with nonlinearmonotone operator, which is a direct generalization of the simplest classical theorem on a differential inequality. The suggested proofs rely on local properties of continuous functions only.     

On the equivalence of two differential equations by means of reflecting functions coinciding

In this article, we discuss the equivalence of two differential systems by using the method of reflecting functions. We obtain some necessary and sufficient conditions under which certain differential equations are equivalent. Given these results, new types of differential systems equivalent to the given systems can be found. We also discussed the qualitative behavior of the periodic solutions of such differential systems. These results are new, in the sense that they generalize previous discussions on the equivalence of differential systems.