切曲面

We propose a unified method to approximate important geometric attributes, including normal vector, gauss curvature, mean curvature, principal curvatures and principal directions on point sampled surface. Based on MLS projection our method is robust to noise and stable to the sampling density.

曲面的微分性质包括法向量和切平面、高斯曲率、平均曲率、主曲率和主方向，在计算机图形学、机器视觉和计算机辅助设计等领域发挥了重要的作用，比如曲面绘制、内外测试、曲面重建、曲面简化、去除曲面噪声和模型分割等。

The surface representation in discrete form and its differential computation are important issues in computer graphics and geometric design.

0引言一般来说，曲面的一阶微分量是指曲面的切平面方向和法向量，二阶微分量是指曲面的曲率等有关量·它们作为重要的曲面信息度量指标，在计算机图形学，机器人视觉和计算机辅助设计等领域发挥了重要的作用·传统的曲面是连续形式的参数曲面和隐式曲面，其微分量的计算已经有了较完备的方法·随着激光测距扫描等三维数据采样技术和硬件设备的长足进步，以及图形工业对任意拓扑结构光滑曲面造型的需求日益迫切，离散形式的曲面———细分曲面、网格曲面和点云曲面正在逐渐成为计算机图形学和几何设计领域的新宠·于是，对这种离散形式的曲面如何估

All quadrilateral mesh automatic generation for regular quadric surfaces based on Auto CAD AME;2. Represent Quadric Surfaces Using NURBS and Calculate the Control Vertecs and Weights;3. Through study,the property is found out that planes cutting edgewise quadric curve and quadric intersections from the quadric surfaces become the harmonic division.

文中采用了射影几何的方法，证明了画法几何中关于两个二次曲面相交的著名的复切定理和蒙日定理，通过研究得出了周切线平面和交线平面成调和分割的性质，同时还得出了处于复切的二次曲面必存在相公切的二次曲面的性

The pattern of camber die-drawing are optimized. The physical innate character of drawing with camber die is analyzed thoroughly. For the first time, the periodical relation between the limit drawing coefficient and the large longitudinal stress in dangerous section is established. Furthermore, the rationale to judge limit deforming degree is developed. Then, the limit drawing coefficient of drawing with camber die is proposed. Based on the criterion that the large stress in flange is smaller than that of limit value, the formula of drawing with camber die without wrinkles is deduced.

对拉深凹模的型式进行了优化；深入地分析了曲面凹模拉深成形的物理本质，首次定量地确定了极限拉深系数与危险断面最大径向应力的关系，提出了判断极限变形程度的依据，分析了极限承载能力，建立了曲面凹模拉深的极限拉深系数的表达式；以凸缘切向最大压应力小于凸缘切向压应力临界值为准则，推导出了曲面凹模拉深不起皱的理论表达式。

This paper researches the part third-order contact condition of tool and the surfaces by the contact principle of deferential geometry in to the 5-axis NC machining and analyzes the contact degree of the intersection line of the cutter and the surfaces.

运用微分几何中的切触原理，研究了在多轴数控机床中铣刀铣削圆与零件曲面的切触条件和局部坐标系下的局部三阶切触条件，并用截形对铣刀铣削圆与曲面的贴近程度进行了分析。

The judging speed is accelerated To assure generating correct tool paths in 3-axis NC machining, the processing plans of undercut and overcut situations for whole tool trajectories are discussed Sometimes certain of complex problems can be simplified using an approximating surface offset strategy presented The surface reconstruction technology in reverse engineering is studied deeply.

讨论了三轴数控加工球头铣刀关于整个刀轨路径的漏切与过切的检查和处理方法，保证最终生成正确的刀具路径。研究了曲面偏距问题，提出了一种曲面近似偏距新策略，在保证正确结果的前提下，将复杂问题简单化。深入研究了逆向工程中散乱数据点的曲面重构技术。

By the definition of Darboux type vector and rectifying Darboux type vector ,we constructed the rectifying type developable surfaces and Darboux type developable surfaces and tangential Darboux type developable surfaces ,and study these three developable surfaces relationship with Minkowski slant helices and Minkowski conical geodesic curves. Bying applying the singularity theoerical knowledge, We give a classification of special developable surfaces under the condition of the existence of such a special curve as geodesic.

通过定义三维Minkowski空间中的达布型向量以及修正达布型向量，构造出三维Minkowski空间中的三类可展曲面，即修正型可展曲面、达布型可展曲面和切达布型可展曲面，研究Minkowski斜螺线和Minkowski锥面测地线这两种特殊曲线和这些曲面的关系，并研究Minkowski斜螺线和Minkowski锥面测地线作为这些曲面的测地线的条件下，运用奇点理论的知识，对这三种可展曲面进行奇点分类。

Firstly, the quadric surface with three points which doesn't on one line is fitted, and then the tangent plane of this fitting surface is got. Meanwhile, the random tangent plane of surface patch subdivided is got also. Finally, the distance can be obtained through iteration between two tangent planes.

首先对点云数据中邻域不在同一直线的三个点进行局部二次曲面拟合，并求取该拟合曲面的切平面，同时求得细分曲面片任意一点处的切平面，最后在两个切平面上进行点对迭代运算，得到点到曲面片的最短距离。

In each step the tangent plane of limit state surface at the previous iterative point is calculated firstly, and then a line from origin to a point on the plane is determined whose intersection with limit state surface satisfies the requirement of feasible direction and convergence.

算法在每步迭代中先计算极限状态曲面在前步迭代点处的切平面，然后在此切平面上选定一个点，使该点和原点的连线与极限状态曲面的交点满足可行方向和收敛的要求。

This paper applies the concept of "contact" in Differential Geometry into the machining of sculptured surfaces, presentes the contact principle of the machining of complicated surfaces, using the circumference circle of the cylindrical cutter to sweep curved surfaces instead of ball-end mill .

把微分几何中曲线与曲面之间的&切触&概念应用于复杂曲面的数控加工，提出用圆柱铣刀和圆锥盘铣刀的外圆在五坐标联动中加工三维自由曲面的最佳切触条件。

We have no common name for a mime of Sophron or Xenarchus and a Socratic Conversation; and we should still be without one even if the imitation in the two instances were in trimeters or elegiacs or some other kind of verse--though it is the way with people to tack on 'poet' to the name of a metre, and talk of elegiac-poets and epic-poets, thinking that they call them poets not by reason of the imitative nature of their work, but indiscriminately by reason of the metre they write in.

索夫农 、森那库斯和苏格拉底式的对话采用的模仿没有一个公共的名称；三音步诗、挽歌体或其他类型的诗的模仿也没有——人们把&诗人&这一名词和格律名称结合到一起，称之为挽歌体诗人或者史诗诗人，他们被称为诗人，似乎只是因为遵守格律写作，而非他们作品的模仿本质。

The relationship between communicative competence and grammar teaching should be that of the ends and the means.

交际能力和语法的关系应该是目标与途径的关系。