变直径管,直径D1=320mm,D2=160mm,流速v1=1.5m/s,v2为()
A. 3m/s
B. 4m/s
C. 6m/s
D. 9m/
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Shell plating that has curvature in two directions and must be heated and hammered to shape over specially prepared forms is called().
A. compound plate
B. furnaced plate
C. flat plate
D. rolled plate
油坊桥车场检修线的线路长度为()米。
A. 155
B. 156
C. 165
D. 166
采用德尔菲预测法邀请的专家人数通常()为宜。
A. 5人以内
B. 10人以内
C. 15~50人之间
D. 50人以上