4f空间滤波系统需要完成从空域到频域,又从频域到空域的两次傅里叶变换过程。( )
周期函数的频率取值是连续的,所以周期函数只有连续谱。( )
Why does Zheyu Liu (刘哲瑜) want to learn English well?
A. He wants to communicate better with his friends.
B. He wants to go abroad to study.
C. He loves to learn English.
Kehai Meng (孟克海) suggests that the kid may have _______ if he or she lives with an American family.
A. cultural shock
B. a language barrier
C. difficulty in sharing their feelings
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