Dynamic characteristics of collaborated system mainly include natural vibration frequency and principal mode, which is the base and precondition of dynamic analysis for collaborated system.
协作体系的动力特性主要包括体系的自振频率和主振型，它是协作体系结构动力分析的基础和前提。
2
Face contour extraction is a significant precondition of facial image analysis such as facial features detection and face recognition.
人脸轮廓提取是人脸特征检测和人脸识别等人脸图像分析的重要前提。
3
When to make quantitative analysis, thermal-stress is the first precondition, the temperature field can be conducted on the basis of the thermal stress solution.