Focus hold

Homogeneous Second System of Center-focus Type to System Concluding Parameters;

中心-焦点型齐二次系统参数化简问题

Designed principle of the rotational stand uses for measuring a camber with double focuses;

一种双焦点曲面的测量用转动架的设计原理

A kind of directness arithmetic about conic′s focus;

二次曲线焦点的直接求法

The focal points of their arguments such as advance informed agreement (AIA), risk assessment and risk management, information exchange and other related issues have been expounded and analyzed.

生物技术的安全性（生物安全）问题已经引起了国际社会的严重关注，不同国家的生物安全能力的巨大差异，使他们对国际生物安全立法的内容和形式等问题产生了很大的分歧，争论的焦点集中在提前知情同意、风险评估和风险管理、资料交换等问题上；本文就上述问题进行了阐述和分析，并指出了国际生物安全立法的发展趋

Based on the Lyapunov stability theory,through improving related theorem,obtain simple and effective methods of judging center or the focal point of nonlinear system and estimating the attraction territory of non-autonomous system.

从Lyapunov稳定性理论出发,通过将有关定理改进,得到判断非线性系统的中心或焦点及估计非自治系统的吸引域的简便而有效的方法。

By the definitions of the conjugate point and the focal point in a geodesic,the paper proves that for any geodesic γ:［0,+∞)→M,in a complete Gauss surface M with positive curvature,there exists t＞0 such that γ(t) is a focal point of γ(0).

从测地线的共轭点、焦点的定义出发,证明了对任意具正曲率的完备二维Gauss曲面,γ:[0,+∞)→M为测地线,则存在t>0,γ(t)是γ(0)之焦点。

Study on the twin-focus technique in laser welding;

激光焊接中的双焦点技术

The most popular detection methods both at home and aboard are introduced,and a method on the position control system for beam focus is presented during laser beam cutting process based on CCD,which can accurate detect and control the laser focus position during laser beam cutting process by using the laser triangulation and CCD imaging system coordination digital image proce.

激光焦点位置的检测与控制是激光切割系统中的关键技术之一。