Least-Squares Fitting of Algebraic Spline Surfaces

We present an algorithm for fitting implicitly defined algebraic spline surfaces to given scattered data. By simultaneously approximating points and associated normal vectors, we obtain a method which is computationally simple, as the result is obtained by solving a system of linear equations. In addition, the result is geometrically invariant, as no artificial normalization is introduced. The potential applications of the algorithm include the reconstruction of free-form surfaces in reverse engineering. The paper also addresses the generation of exact error bounds, directly from the coefficients of the implicit representation.     

两邻接B样条曲面的G1连续条件

本文得到了非均匀重内节点邻接B样条曲面间G1连续的充要条件 ,给出了一类G1连续的充分条件 ;基于对B样条曲线参数连续性的分析 ,本文着重给出了这类充分条件成立的内在约束 ,即对公共边界控制顶点的约束条件 .     

参数曲面的局部凸性条件

参数曲面的凸性分析在计算机辅助设计中有着重要的作用.给出了一般参数曲面局部凸的定义,利用曲面的第二基本量和高斯曲率.得到了一般参数曲面局部凸的几个必要条件.     

G~1 Continuity Conditions of B-spline Surfaces

According to the B-spline theory and Boehm algorithm, this paper presents several necessary and sufficient G1 continuity conditions between two adjacent B-spline surfaces. In order to meet the need of application, a kind of sufficient conditions of G1 continuity are developed, and a kind of sufficient conditions of G1 continuity among N(N > 2) patch B-spline surfaces meeting at a common corner are given at the end.     

一类双k次B样条曲面的G1连续性条件

本文针对两个k×k次B样条曲面的节点向量为端点插值、内部是单节点的情形 ,给出它们之间的G1光滑拼接条件 ,同时得到它们的公共边界曲线的控制顶点所要满足的本征方程 .其中本征方程是B样条曲面片所独有的现象 .     

Difference Method of General Schemes with Intrinsic Parallelism for One-dimensional Quasilinear Parabolic Systems with Bounded Measurable Coefficients

The difference method of the general finite difference schemes with intrinsic parallelism for the boundary value problem of the quasilinear parabolic system is studied without assuming heuristically that the original boundary value problem has the unique smooth vector solution.     

`CH~2中齐性曲面的分类(英文)

ＣＨ~２中的曲面 Ｍ称为（局部）齐性的,如果对任何一对点 ｐ,ｑ,存在变换。 σ　Ｕ（１,２）把含ｐ的一个邻域变为含ｑ的邻域,且把ｑ变为ｑ．本文给出ＣＨ２中齐性曲面的完全分类．     

Periodic Homogenization for Inner Boundary Conditions with Equi-valued Surfaces: the Unfolding Approach

Making use of the periodic unfolding method, the authors give an elementary proof for the periodic homogenization of the elastic torsion problem of an infinite — dimensional rod with a multiply-connected cross section as well as for the general electroconductivity problem in the presence of many perfect conductors (arising in resistivity well-logging). Both problems fall into the general setting of equi-valued surfaces with corresponding assigned total fluxes. The unfolding method also gives a general corrector result for these problems.     

具有特殊类型端口的极小曲面的构造

We proved that there exists a family of complete oriented minimal surfaces in R3 with finite total curvature-4nπ,each of which has 0 genus and two ends,and both of the ends have winding order n,where n ∈ N,and discussed the symmetric property for special parameters.     

Surfaces with harmonic inverse mean curvature in space forms

We define surfaces with harmonic inverse mean curvature in space forms and generalize a theorem due to Lawson by which surfaces of constant mean curvature in one space form isometrically correspond to those in another. We also obtain an immersion formula, which gives a deformation family for these surfaces.

     

Kinematic Generation of Ruled Surfaces

This paper presents a method for kinematic generation of free-form ruled surfaces. The method is based on the kinematic displacement of lines. The ruled surfaces are represented as curves on a dual unit sphere. The curves are created by using the Lie Group structure of the dual space to generate dual displacement matrices for the lines. Free-form surfaces are created by repeated geodesic interpolation using the displacement matrices. An application for these surfaces is presented in five-axis cylindrical milling.     

Surfaces with many solitary points

It is classically known that a real cubic surface in cannot have more than one solitary point (or -singularity, locally given by x ² + y ² + z ² = 0) whereas it can have up to four nodes (or -singularity, locally given by x ² + y ² − z ² = 0). We show that on any surface of degree d ≥ 3 in the maximum possible number of solitary points is strictly smaller than the maximum possible number of nodes. Conversely, we adapt a construction of Chmutov to obtain surfaces with many solitary points by using a refined version of Brusotti’s Theorem. Combining lower and upper bounds, we deduce: , where denotes the maximum possible number of solitary points on a real surface of degree d in . Finally, we adapt this construction to get real algebraic surfaces in with many singular points of type for all k ≥ 1.      

Minimal Surfaces with an Elastic Boundary

LetD:= { C ³ (

关于隐式代数曲面的一种几何连续性定义

本文利用函数的幂级数给出了隐式代数曲面的一种几何连续性定义．证明了在此定义下的ｋ阶几何连续即为ｋ阶变尺度（ｒｅｓｃａｌｉｎｇ）连续，并举例说明了其应用的方便性．     

Integral Models of Extremal Rational Elliptic Surfaces

Miranda and Persson classified all extremal rational elliptic surfaces in characteristic zero. We show that each surface in Miranda and Persson's classification has an integral model with good reduction everywhere (except for those of type X ₁₁(j), which is an exceptional case), and that every extremal rational elliptic surface over an algebraically closed field of characteristic p > 0 can be obtained by reducing one of these integral models mod p.     

K3 Surfaces with Nine Cusps

By a K3-surface with nine cusps I mean a surface with nine isolated double points A₂, but otherwise smooth, such that its minimal desingularisation is a K3-surface. It is shown that such a surface admits a cyclic triple cover branched precisely over the cusps. This parallels the theorem of Nikulin that a K3-surface with 16 nodes is a Kummer quotient of a complex torus.     

On Some Special Surfaces Connected with Convex Surfaces of the Lobachevskii Space

With a closed convex surface in a Lobachevskii space we associate four special surfaces: the inscribed and circumscribed spheres, a sphere rolling freely over the inner side of , and an equidistant surface over whose inner side rolls freely. We find an exact dependence between these four special surfaces.     

Parabolicity and Hyperbolicity Conditions for Boundary Elements of Surfaces

Mathematical Notes -     

$E^3$中的一类Weingarten曲面

In this paper, we construct a kind of Weingarten surfaces in E3 and study its geometric properties. We first derive an explicit diffierential relationship between the principal curvatures of them. Then we prove an existence theorem of this kind of surfaces with prescribed principal curvatures. At last, we present two examples involving the rotation surfaces as the special case, and present several figures to the second example.