题目内容

图7-17b中，显示器的X轴为10μs/div(格)，现测得底波（B波）与始波（T波）的距离为10格，缺陷波（F波）与T波的距离为3.5格。求：1）底波所经历的时间tδ；2）缺陷波所经历的时间tF；3）钢板的厚度δ；4）缺陷与表面的距离xF 。

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在图7-11的超声波流量测量中，流体密度ρ=900kg/m3，管道直径D=1m，α=45°，测得Δf=10Hz，求：1）管道横截面积A；2）流体流速v；3）每秒的体积流量qV；4）质量流量qm为多少千克每秒？5）1小时的累积流量q总为多少吨？

They ______thetrip until the rain stopped.

A. continued
B. didn’t continued
C. hadn’t continued
D. would continue

It’s ten years since we _______.

A. have parted
B. parted
C. part
D. were parted

On his next birthday he ________ married for ten years.

A. has been
B. will be
C. will have been
D. would have been