一束由发光二极管发射出的红外线光立刻进入到使用者眼前的空间，这样一个小型摄像机装置，可分析人们的手势轨迹。
A ring of LEDs projects infrared light into the space immediately in front of the user so a camera in the device can interpret gestures.
这种方法可直接获得向径、轨道速度等参数随时间或极角（绕地心的转动角）的变化，便于分析轨道转移与逃逸运动，有助于飞行使命与运动轨迹的设计。
Radius and orbital velocities can be directly expressed as functions of time or polar angle, which is helpful for designing flight mission and motion trajectory.
在厚壁管、压力容器及电站锅炉的窄间隙全位置焊接中，钨极运动轨迹是动态的。
The synthesizing control scheme is put forward based on the requilement of narrow-gap all-position welding technology in terms of the moving track of tungsten electrode.
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