曲面

For a general parametric curve/surface, we usually cannot compute its exact implicit form. Even though its exact implicit form can be computed, the curve/surface implicitization involves relatively complicated computation and the degree is higher. Moreover, it may have unexpected components and self-intersections. All these unsatisfied properties limit the applications of the exact implicitization. So finding curve/surface approximate implicitization has become a practical problem. In this paper, we present an algorithm to solve the approximate implicitization of a given parametric curve by using a quadratic algebraic spline curve.

由于精确隐式化过程不一定可以实现，即使可以实现隐式曲线曲面的阶数高计算复杂，并且具有不希望的自交点和奇异分支，从而限制了隐式化的运用，所以寻求参数曲线曲面的近似隐式化问题成为很实际又重要的问题，提出利用二次代数样条曲线来实现一般平面参数曲线近似隐式化的一种算法。

The procedure of transform the parametric form into algebraic form is calledimplicitization.

将参数形式的曲线曲面转化为代数形式的曲线曲面的过程称为隐式化。

In this paper, we have made a systemic theoretic research on modelling and reshaping several types of spline curves/surfaces in CAGD. And some creative productions are given as follows. At first, the uniform C-B-spline basis is proved to be a normalized totally positive basis, and can be extended to a normalized B-basis. C-B-spline and C-Bézier basis, similar to B-spline basis and Bézier basis in algebraic space, are two bases in algebraic trigonometric space.

本文围绕着CAGD中常用的几种曲线曲面造型和形状调整进行了深入的研究，主要获得了以下一些成果：首先，证明了代数三角空间中的n次均匀C-B-spline基是一组标准全正基，并进一步扩充为一组标准B基。C-B-spline基与C-Bézier基是多项式与三角混合空间中的两组基，是适应工程实践中设计特殊曲线曲面的需要而产生的，类似于多项式空间中的B-spline基与Bézier基，是CAGD中重要的造型工具。

We posed the concept of sufficient intersection about s(1≤s≤n) algebraic hypersurfaces in n-dimensional space and proved the dimension of polynomial space Pm(which denotes the space of all multivariate polynomials of total degree≤m) on the algebraic manifold S=s(f1,…, fs) where f1(X=0,…, f s=0denote s algebraic hypersurfaces of sufficient intersection, then gave a convenient expression for dimension calculation by using the backw ard difference operator.

给出了n维空间中s(1≤s≤n)个代数超曲面充分相交的概念，证明了n元m次多项式空间Pm在充分相交的代数流形S=s(f1，…， fs)（f1=0，…， fs=0表示s个代数超曲面）上的维数，并利用倒差分算子给出一个方便计算的表达式；构造了沿代数流形上插值适定结点组的叠加插值法；证明了在充分相交的代数流形上任意次插值适定结点组的存在性；给出代数流形上插值适定结点组的性质和判定条件。

Since the visualization of implicit algebraic surface is still a difficult problem, it is doubtlessly meaningful to construct some convenient and effective parameterization method for some kind of concrete implicit surfaces.

由于隐式代数曲面的显示问题始终是困扰人们的一个关键性难题，从而针对具体形式的代数曲面，能给出方便有效的参数化方法无疑是有意义的。

By using very general implicit shape primitive—algebraic surface, our scheme can represent more general 3D surfaces than other implicit surface reconstruction techniques.

同其它隐曲面重建方法相比，我们的方法通过使用很具一般性的隐式形状单元—代数曲面—可以表示更一般的三维表面。

In this paper, we discuss parameterization of implicit blending algebraic surfaces of three quadratic surfaces.

本文研究了三个二次曲面的隐式光滑拼接代数曲面的参数化。

In this paper, we mainly study the alternating group A_4 actions on spin 4-manifolds. First we discuss the special action of A_4 on K3 surfaces of Fermat type, we compute the fixed points set of this action and some invariants of the group action, also we get some topological properties. Then we study the A_4 actions on general K3 surfaces and obtain some similar results.

本文主要是以交错群A_4在K3曲面上的作用为研究对象，从Fermat型K3曲面上的特殊的A_4作用出发，得到了Fermat型K3曲面上A_4作用的不动点，利用不动点集计算了群作用的一些不变量并得到了相关的拓扑性质，在此基础上进一步把其中的一些结果推广到一般情形下的同伦K3曲面上。

Sea area measurement usually uses GPS timely processing the position data for the boundary of sea area, and then calculates the sea area of anomalistic area.

海域面积是一个封闭且不规则的曲面区域，对海域面积测算通常是先使用GPS定时测定待测海域边界位置点的地理坐标，再求取其围成的不规则曲面区域的面积。

It has been widely used in recent years, for it not only preserves several advantages of B-spline surface, especially the affine- invariance, but also has some special advantages such as adaptability to arbitrary topology which parameter surface doesn't have.

它不仅具备B样条曲面仿射不变性等良好性质，还具有参数曲面所没有的任意拓扑适应性等特点，因而近年来得到了广泛的应用。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。