基于伪类光超曲面奇点分类的教学研究

在微分几何的教学中,曲线,曲面理论是最主要的基础理论知识.欧氏空间中密切曲线在微分几何学中具有重要的研究价值.主要运用具有类光向量的费雷内标架讨论在四维Minkowski空间中与欧氏空间不同的一类特殊密切曲线(伪类光曲线)的一些几何性质,同时通过横截性原理给出了由伪类光曲线生成的伪类光超曲面的局部几何性质与奇点分类.     

广义de Sitter空间中的类时超曲面的切触性质

从切触几何及Legendrian奇点理论的角度研究了广义de sitter空间中的类时超曲面的切触性质及gdS-高斯像的奇点的分类和几何意义.     

广义de Sitter空间中法向Lorentzian超曲面的nullcone Gauss映射的奇点

利用奇点理论研究了广义de Sitter空间中具有Lorentzian法空间的一类超曲面.介绍了这类超曲面的局部微分几何,定义了nullcone Gauss映射及nullcone高度函数族,进而研究了nullcone高度函数族的性质及nullcone高斯映射的几何意义,最后研究了这类超曲面的通有性质.     

三维Minkowski空间中非类光曲线的双曲达布像和从切高斯曲面

本文主要给出了三维Minkowski空间中非类光曲线的双曲达布像和从切高斯曲面的奇点分类,并且建立了奇点和曲线几何不变量之间的联系,其中曲线几何不变量与曲线同螺线切触的阶数密切相关.     

平面三次H-Bézier曲线的形状分析

本文对平面三次H-Bézier曲线的形状进行分析,讨论其诸如奇点、拐点、局部凸和全局凸的几何特征,得出曲线上含有奇点、拐点和曲线为局部凸或全局凸的用控制多边形边向量相对位置表示的充分必要条件.     

平面三次H-Bézier曲线的形状分析

本文对平面三次H-Bézier曲线的形状进行分析,讨论其诸如奇点、拐点、局部凸和全局凸的几何特征,得出曲线上含有奇点、拐点和曲线为局部凸或全局凸的用控制多边形边向量相对位置表示的充分必要条件.     

广义de Sitter空间中的类时超曲面

利用奇点理论研究广义de Sitter空间中的类时超曲面.介绍类时超曲面的局部微分几何,定义了广义de Sitter高斯像及广义de Sitter高度函数,研究广义deSitter高度函数族的性质及广义de Sitter高斯像的几何意义,介绍了一种证明高度函数为Morse族的新方法.最后研究了类时超曲面的通有性质.     

线性奇点的对称性质

本文研究奇点集为光滑流形的非孤立奇点的对称性质，证明了这类奇点具有与孤立奇点相类似的对称性质．     

具孤立奇点的完全交叉的上同调(三)

本文证明了不可约超曲面孤立奇点的无穷小邻域的全微分形式的上同调是有限维线性空间,并证明了它们与通常微分形式上同调之间的关系.     

闭曲面上C0流有伪轨跟踪性质的条件

给出了闭曲面上奇点孤立的C⁰流有伪轨跟踪性质的充分必要条件     

用边界曲线构造C~1 Coons曲面确定扭矢的方法

本文讨论了由四条边界曲线构造Ｃ１Ｃｏｏｎｓ曲面的问题，给出了确定角点扭矢的新方法．该方法沿四边形两对角线方向构造两条四次多项式曲线，每个角点处的扭矢，由一条四次曲线和两条边界曲线确定．跨界切矢由三次埃尔米特插值方法定义．文中还给出了一个用新方法构造曲面的实例．     

On the quartic curve of Han

The quartic curve of Han [X. Han, Piecewise quartic polynomial curves with shape parameter, Journal of Computational and Applied Mathematics 195 (2006) 34–45] can be considered as the generalization of the cubic B-spline curve incorporating shape parameters into the polynomial basis functions. We show that this curve can be considered as the linear blending of the original cubic B-spline curve and a fixed quartic curve. Moreover, we present the Bézier form of the curve, which is useful in terms of incorporating the curve into existing CAD systems. Geometric effects of the alteration of shape parameters is also discussed, including design oriented computational methods for constrained shape control of the curve.     

A geometric approach to Euler’s addition formula A direct formulation of the addition law for elliptic curves given in?terms of Weierstra? quartics

Plane quartic curves given by equations of the form y ²=P(x) with polynomials P of degree 4 represent singular models of elliptic curves which are directly related to elliptic integrals in the form studied by Euler and for which he developed his famous addition formulas. For cubic curves, the well-known secant and tangent construction establishes an immediate connection of addition formulas for the corresponding elliptic integrals with the structure of an algebraic group. The situation for quartic curves is considerably more complicated due to the presence of the singularity. We present a geometric construction, similar in spirit to the secant method for cubic curves, which defines an addition law on a quartic elliptic curve given by rational functions. Furthermore, we show how this addition on the curve itself corresponds to the addition in the (generalized) Jacobian variety of the curve, and we show how any addition formula for elliptic integrals of the form ò(1/?{P(x)}) dx\int (1/\sqrt{P(x)})\,\mathrm{d}x with a quartic polynomial P can be derived directly from this addition law.     

A geometric approach to Euler’s addition formula

Plane quartic curves given by equations of the form y ²=P(x) with polynomials P of degree 4 represent singular models of elliptic curves which are directly related to elliptic integrals in the form studied by Euler and for which he developed his famous addition formulas. For cubic curves, the well-known secant and tangent construction establishes an immediate connection of addition formulas for the corresponding elliptic integrals with the structure of an algebraic group. The situation for quartic curves is considerably more complicated due to the presence of the singularity. We present a geometric construction, similar in spirit to the secant method for cubic curves, which defines an addition law on a quartic elliptic curve given by rational functions. Furthermore, we show how this addition on the curve itself corresponds to the addition in the (generalized) Jacobian variety of the curve, and we show how any addition formula for elliptic integrals of the form \(\int (1/\sqrt{P(x)})\,\mathrm{d}x\) with a quartic polynomial P can be derived directly from this addition law.     

On Affine Surface That can be Completed by A Smooth Curve

In C⁶, we consider a non linear system of differential equations with four invariants: two quadrics, a cubic and a quartic. Using Enriques-Kodaira classification of algebraic surfaces, we show that the affine surface obtained by setting these invariants equal to constants is the affine part of an abelian surface. This affine surface is completed by gluing to it a one genus 9 curve consisting of two isomorphic genus 3 curves intersecting transversely in 4 points.     

QUADRATIC SYSTEM WITH HOMOCLINIC CYCLE DESCRIBED BY SEXTIC CURVE

In [2-5], cubic, quartic or quintic homoclinic cycles are found. In this paper, we present a quadratic system with homoclinic cycle which is described by a sextic curve. quadratic system, homoclinic cycle, algebratic invariant curve     

具有四次曲线解的Kolmogorov三次系统极限环的存在性问题

证明了具有退化四次曲线解[y-(x-1)2]2=0的Kolmogorov三次系统是可以存在极限环的.并举出了具体的例子.     

MODIFIABLE QUARTIC AND QUINTIC CURVES WITH SHAPE-PARAMETERS

1　IntroductionBecause of their good properties,the cubic Bézier,B-spline and NURBScurves play animportantrole in CAD,CAGD and modeling systems.When interpolation by the abovecurvesto all ora partofthe control pointsisrequired,itis necessary eitherto find new control pointsby solving a system of linear equations or to insert additional control points. Moreover,thewhole interpolating curve may be affected by moving an individual control point[1～ 6] .By uisng the matrix form ofthe Bernst…     

Low-degree points on Hurwitz-Klein curves

We investigate low-degree points on the Fermat curve of degree 13, the Snyder quintic curve and the Klein quartic curve. We compute all quadratic points on these curves and use Coleman's effective Chabauty method to obtain bounds for the number of cubic points on each of the former two curves.