二次曲面

To improve the imaging quality of CCD camera and make the lens small in size,compact in structure,the wide field of view optical lens with the standard quadric surface and even aspheric surface was designed.

为提高CCD摄像机的成像质量，同时使镜头结构紧凑、小型化，在大视场光学镜头的设计中，引入标准二次曲面和偶次非球面。

The segmentation results are proper for quadric surface identification and NURBS approximating in reverse engineering.

该算法在大量的噪声网格模型上获得了较好的分割结果，适用于逆向工程中的二次曲面识别和NURBS曲面逼近。

We call this surface the stress quadric.

我们称这个曲面为应力二次曲面。

An algorithm of feature surface recognition based on quadric surface fitting and geometry property was presented.

提出了基于二次曲面拟合误差分析和几何属性分析的特征曲面识别算法。

This paper proposes an algorithm to recognize and reconstruct the skewed quadric surfaces based on the analysis of their projection features.

在分析斜截切二次曲面在三视图中的投影特性的基础上，提出识别和重建这类曲面的算法。

Quadric surfaces are the simplest curved surfaces and are widely used in CAD/CAM or solid modeling.

二次曲面作为表示形式最简单的一种曲面，在CAD／CAM以及立体造型中有非常广泛的应用。

Based on mathematical analysis, elastic geostress field is a symmetric second-order tensor, which can be expressed as symmetric matrix and studied by its eigenvalue and eigenvector.

根据对二阶张量的数学分析，通过求取二阶张量的特征值与特征向量，导出了对称张量在空间几何学中对应的二次曲面。

We use least squre method to form conicoid mathematic model and fit the point cloud which has been grouped by octree subdivision method.

应用最小二乘法建立二次曲面的数学模型，对于已用八叉树分组的点云数据实现隐函数拟合。

The surface of image can be looked as a curved surface, and we can simulate a conicoid function in local area. Based on this function we can estimate the gradient and the curvature of the curved surface points, and set proper thresholds of gradient and curvature, we can detect the centre lines of roads with correlative process including removing small areas, area growth, thinning, etc. Lastly through seting proper thresholds of the gradient and the curvature again, the original road junctions can be detected and then verified by the road lines detected formerly.

基于微分几何的道路交叉口识别方法：把影像的灰度表面看作是一个曲面，在局部区域内拟合一个二次曲面函数，通过该函数来估算梯度和曲率并设定合适的梯度和曲率阈值来检测道路中心线，并进行相关处理，例如去除小区域、区域增长、细化等，然后再设定合适的梯度和曲率阈值，检测出初始道路交叉口，并用检测出来的道路来进行确认。

Based on the forenamed theory, Estimated the Total Electron Content including the second-order ionospheric error. Established the 2°×2° geomagnetic vector grid-model over mostly area of China , then processed some dual-frequency data to indicate the algorithm is feasible and correct. Obtained some useful conclusion after analyzing the result of data processing.

本文计算了基于中心电离层单层模型的覆盖中国区域的2°×2°地磁场格网点的矢量值，对计算结果的X、Y、Z三个方向分量进行二次曲面拟合，对两种考虑地磁场影响计算包含电离层延迟误差二阶项的TEC估计结果进行了计算，验证了拟合模型的正确性和可行性，并对试算结果进行了分析，得到了一些有益的结论。

But we don't care about Battlegrounds.

但我们并不在乎沙场中的显露。

Ah! don't mention it, the butcher's shop is a horror.

啊！不用提了。提到肉，真是糟透了。