【简答题】如图所示,用轮廓仪对一机械加工表面的粗糙度检测信号a(t)进行自相关分析,得到了其相关函数Ra(τ)。试根据Ra(τ)分析造成机械加工表面粗糙度的原因。
【简答题】翻译:熊猫的食物竹子 — 也深受中国人民的喜爱。
【单选题】. He always_________his time and his efforts .
A.
made the most of; paid off
B.
made good use of; paid back
C.
took the most of; paid for
【单选题】They ( ) him for the job because he is a good teacher.
【简答题】测量表面粗糙度轮廓幅度参数时,规定取样长度的目的是______。测量Ra的常用仪器是______;测量Rz的常用仪器是______。
【简答题】. He has made a lot of films, but __________ good ones. A.any B.some C.few D.many
【简答题】() 是中国抗日战争的起点,中国人民不屈不挠的局部抗战揭开了世界反战争的序幕。