消除螺旋桨鸣音的具体办法是将桨叶随边0.4R～0.8R部分（）等抗鸣

【名词&注释】

锯齿状(zigzag)、具体办法(concrete methods)、螺旋桨鸣音

[单选题]消除螺旋桨鸣音的具体办法是将桨叶随边0.4R～0.8R部分（）等抗鸣边缘，从而改变涡流引起的振动频率，也就不会与桨叶固有振动频率产生共振。Ⅰ.加厚；Ⅱ.减薄；Ⅲ.形成锯齿状；Ⅳ.质量改变；Ⅴ.钻孔。

A. Ⅱ＋Ⅲ
B. Ⅰ＋Ⅱ＋Ⅲ＋Ⅴ
C. Ⅲ＋Ⅳ＋Ⅴ
D. Ⅰ＋Ⅱ＋Ⅲ＋Ⅳ

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学习资料：

[单选题]The term （） refers to one complete sequence of operations required to produce power in an engine.

A. diesel engine
B. stroke
C. cycle
D. compression ratio

[单选题]With the shell and cap assembled as for running, a check must be made that the clearance between the cap and the housing （）.

A. has a nip
B. is large enough
C. is zero
D. are suitable

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