将信号<img src="https://storage.tutusouti.com/pzst/question_bank/res/fd/56/fd5624e003bf7e8e5d6de8156407d5690fb77049.jpg?x-oss-process=image/sharpen,200"/>变换为（）称为对信号<img src="https://storage.tutusouti.com/pzst/question_bank/res/fd/56/fd5624e003bf7e8e5d6de8156407d5690fb77049.jpg?x-oss-process=image/sharpen,200"/>的平移或移位。