On locally convex hypersurfaces in Hadamard manifolds

Locally convex compact hypersurfaces immersed in a hollow simply connected Riemannian space of nonpositive sectional curvature are considered. They are proved to be convex hypersurfaces homeomorphic to the sphere. A similar result for immersed hypersurfaces with nonpositive definite second quadratic form of rank no smaller than one is obtained. Translated fromMatematicheskie Zametki, Vol. 67, No. 4, pp. 498–507, April, 2000.     

基于空间分解变换的模糊错误矩阵方程求解

模糊错误逻辑对现实世界的对象用(u,x)表示为((U,S(t),■T(t),L(t)),(x(t)=f((u(t),■),GU(t)),GU(t)),用模糊错误变换矩阵可以表示分解、相似、增加、置换、毁灭、单位变换等6种变换方法,本论文基于求解方程XA′=B,针对■的分解,研究了基于空间分解变换的错误矩阵方程求解。以期从矩阵方程求解的角度对错误转化规律进行探索研究。     

泰劳公式的拉格朗日型余项中介值点的研究

当区间长度趋于0时,泰劳公式的拉格朗日型余项中介值点的变化规律.     

Explicit peakon and solitary wave solutions for the modified Fornberg-Whitham equation

In this paper, the modified Fornberg-Whitham equation is studied by using the bifurcation theory and the method of phase portraits analysis. In some parametric conditions, some peakons and solitary waves are found and their exact parametric representations in explicit form are obtained.     

Fast computation of Hermite normal forms of random integer matrices

This paper is about how to compute the Hermite normal form of a random integer matrix in practice. We propose significant improvements to the algorithm by Micciancio and Warinschi, and extend these techniques to the computation of the saturation of a matrix. We describe the fastest implementation for computing Hermite normal form for large matrices with large entries.     

Bäcklund transformation and multi-soliton solutions for a (2 + 1)-dimensional Korteweg-de Vries system via symbolic computation

In this paper, the (2 + 1)-dimensional Korteweg-de Vries system is symbolically investigated. By the bilinear method, the N-soliton solution is presented. Then, based on the Bäcklund transformation in bilinear form, a new Bäcklund transformation is obtained and new representation of the N-soliton solution is derived. A class of novel multi-soliton solutions are obtained by the new Bäcklund transformation and the availability of symbolic computation is demonstrated.     

A minimal Cantor set in the space of 3-generated groups

We construct and study a family of 3-generated groups parametrized by infinite binary sequences w. We show that two groups of the family are isomorphic if and only if the sequences are cofinal and that two groups cannot be distinguished by finite sets of relations. We show a connection of the family with 2-dimensional holomorphic dynamics.      

Shear Buckling Form of a Circular Sandwich Ring under Uniform External Pressure

The problem on the stability of a circular sandwich ring under uniform external pressure is considered. It is shown that, along with a mixed flexural-shear buckling form (BF), a pure shear BF can be realized in the core. This form is accompanied by rotation of the load-carrying layers at the cost of the transverse shear strain (constant in the circumferential direction) in the core. It is found that the simplified equations of the theory of shallow shells cannot describe this nonclassical BF. The critical loads corresponding to the shear BF may prove to be smaller than the critical load of the classical mixed flexural BF for a circular sandwich ring of medium thickness at a low shear modulus of the core. The results obtained contribute greatly to the understanding of buckling mechanisms of sandwich structures and supplement the existing classification of BFs.     

射影半对称联络的一个不变量

本文研究与Levi-Civita联络▽射影等价地射影半对称联络D。获得了一个射影不变量,并给出其成立的一个充分必要条件。进而给出其保持相应共变导数不变的另一充分条件。