The Air Waybill is the most important document for goods transportation by()
Air
B. Road
C. Sea
D. Train
查看答案
If the L/C stipulates that the shipment date is “on or about May10th, 2008”, them the goods can be shipped ()
A. from 10th to 20th
B. from 5th to 15th
C. from 1st to 10th
D. from 1st to 15th
如下图所示，已知管道总长度等于20m，直径等于0.1m，水箱水面高于管道出口2m，沿程阻力系数等于0.03，90°弯头的阻力系数等于0.25，管道中的流速等于()。
A. 2.09m/s
B. 2.21m/s
C. 2.29m/s
D. 2.33m/s
如下图所示，水流由水平放置的90°弯管流出，流量为Q，流速为υ，液体密度为ρ，水流对弯头的作用力()。
A. Rx＞ρQυ，Ry＞ρQυ
B. Rx=ρQυ，Ry＞ρQυ
C. Rx＞ρQυ，Ry=ρQυ
D. Rx=ρQυ，Ry=ρQυ
以下叙述正确的为()。
A. 系统误差呈正态分面
B. 系统误差又称可测误差
C. 系统误差包括操作误差
D. 方法误差属于系统误差
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