The physical foundation of the ultrasonic waves is presented. A contactless ultrasonic sensor in seam tracing is developed.
介绍了超声波的物理基础，研制了焊缝跟踪中的非接触超声波传感器。
The influence of weight training on the athletes physical performances was investigated by a series of tracing tests.
运用追踪测试的方法考察了负重训练对运动员运动能力的影响。
The influence of weight training on the athletes physical performances was investigated by a series of tracing tests.
运用追踪测试的方法考察了负重训练对运动员运动能力的影响。
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