超音波法液位元元元元元元测定
ultra-sonic method of liquid meaduremert
差分四相相移健控
difference quarter phase shift keying
电流切换式四相位调变器
current-commutating quadrature modulator
可换四元数
commutative quaternion algebra
可交换四元数
commutative quaternion algebra
可交换四元数代数
commutative quaternion algebra