active Doppler velocity sensor

例句：

1. 1.The team is active in promoting environmental protection.
   该团队积极推广环境保护。
2. 2. She is an active member of the community.
   她是一个社区的积极成员。
3. 3. The new manager has made a lot of changes to make the company more active.
   新任经理已做出许多改变，使公司更加活跃。
4. 1.The Doppler effect causes the frequency of sound waves to shift as they travel through different mediums.
   多普勒效应导致声音波在通过不同介质时频率发生变化。
5. 2. The radar system uses the Doppler effect to detect moving objects.
   雷达系统利用多普勒效应来探测移动物体。
6. 3. The scientist used the Doppler effect to study the movement of stars.
   科学家利用多普勒效应研究恒星的运动。