三次曲线

In order to overcome shortcomings that the circular arc and ellipse could not be accurately represented by CE-Bézier curves, this method used the continuity condition of CE-Bézier curves and C-Bézier curves to resolve the representation of circular arc and ellipse in CE-Bézier curve modeling.

该方法首先构造了一种具有优良形状可调性和更好逼近性的带3个形状参数α，β，γ的三次扩展Bézier曲线(CE-Bézier曲线)；并针对CE-Bézier曲线无法精确表示圆弧和椭圆弧等二次曲线的缺点，利用CE-Bézier曲线与C-Bézier曲线间的拼接技术，解决了CE-Bézier曲线造型中圆弧和椭圆弧的表示问题。

Based on vector expression of parametric equation of a third－order Bezier curve, Bezier curve interpolation algorithm is proposed in order to imitate tabulation curve.

为了描述列表曲线，本文从三次Bezier曲线参数方程的矢量表达式出发，推导出CNC系统三次Bezier曲线插补法。

In the first part of the paper, we construct a family of 1 parameter cubic algebraic curves interpolating four given points and two tangent lines at the endpoints, and one can manipulate the shape of cubic algebraic curves by controlling the points or the tangent line directly.

该文提出的代数曲线的结构有两种，一种是插值平面上四点及两端点切线的三次代数曲线；另一种是插值两端点、两切线及两曲率的三次代数曲线。

In the last part of the paper, we construct a family of 2 parameter cubic algebraic curves interpolating two given endpoints and two given tangent lines and two given curvatures at these two endpoints with different initial cases in detail.

引 言三次参数曲线在计算机辅助几何设计与计算机图形学领域一直扮演着十分重要的角色，这主要是由于三次参数曲线是具有奇异性的次数最低的曲线，这些奇异性包括尖点、拐点和闭圈。

Because of cubic B spline curve have several advantages such as local controllable, continuity etc, an active contour model based on cubic B spline curve is proposed in this dissertation.

针对以上问题，结合三次B样条曲线连续性及局部可控性的特点，本文提出了一种基于三次B样条曲线的主动轮廓模型。

Through analyses, we can make the conclusion that, the relation of seed fresh weight dry weight and days after pollination, fat percent content, protein nut content, starch nut content can be expressed with Logistic equation; the change of kernel volume, moisture content of kernel and days after pollination accorded with three ascend curve equation. Kernel protein content, starch content and the changes of days after pollination tallied with reciprocal equation and they had high relation.

经过统计与分析，可以看出籽粒鲜重积累量与授粉后时间、籽粒干重与授粉后的时间、脂肪净含量、脂肪百分含量、蛋白质净含量、淀粉净含量与授粉后的时间均可以用Logistic方程描述，籽粒体积变化与授粉后的时间关系表现为三次上升型曲线方程；籽粒的水分含量与授粉后的时间关系表现为三次下降型曲线方程；籽粒中蛋白质百分含量与授粉后时间的动态变化规律、籽粒中淀粉百分含量与授粉后时间的动态变化规律符合倒数方程，均具有较高的拟合度。

With the shape parameter, the trigonometric polynomial curves can be close to the cubic Bécurves or close to the given control polygon then the cubic Bécurves.

由四个控制顶点生成的曲线具有与三次B zier曲线类似的性质，但具有比三次B zier曲线更好的逼近性。

As an example to cubic trigonometric polynomial Bézier,the characters of trigonometric polynomial Bézier curve is analyzed,and deduced that cubic trigonometric polynomial Bézier curve is more smooth than cubic polynomial Bézier curve.

Bézier曲线是计算机辅助几何设计中的一类重要曲线，文献[1]介绍了三次Bézier曲线插值，文献[2]介绍了三次Bézier曲线的保凸插值，但难以解决一端曲率为0，另一端曲率比较大的插值问题。

When t=1/2, Path of the C-curves and H-curves ofdegree two and three are lines, but not for the Path of degree four, weneed more about the control polygon. Paths are commonly curves. Butthe reference [38] pointed out that they can closely be approximated bylines. By this method we can get a C-curve passing a given point easily.

一般情况下，C曲线族的Path也是曲线，文献[38]以三次C曲线为例，提出用直线进行近似，应用这一方法，我们可以简洁的求出过一定点的C曲线，只要给定的点在C曲线族的范围内，则可以首先求出过这一点的C曲线族的Path，然后可以确定过这一点的C曲线的形状参数α，以及曲线参数t.H曲线的情况与C曲线类似。

By invoking a suitable measure of shape, e.g., the absolute rotation index or elastic bending energy, a "good" interpolant is selected. A new means to differentiate among the solutions is introduced here, namely, the winding number of the closed loopformed by a union of the hodographs of the couple of PH cubic and of the unique "ordinary" cubic interpolant.

已有的插值算法都是依赖于构造出所有四个解，利用绝对旋转数或弹性弯曲能量来找出这条&好&的插值曲线，本文介绍一种新的方法来区分这些解，即用由三次PH曲线偶和惟一传统三次插值曲线的速端曲线形成的闭环的弯曲数来区分。

Do you know, i need you to come back

你知道吗，我需要你回来

Yang yinshu、Wang xiangsheng、Li decang,The first discovery of haemaphysalis conicinna.

1〕 杨银书，王祥生，李德昌。安徽省首次发现嗜群血蜱。