问题 问答题 简答题

如何对压力钢管的空蚀和磨蚀进行处理?

答案

参考答案:

钢管内壁出现空蚀主要是钢板表面不平整所引起的,应将突起物铲除或采取研磨措施使管壁达到要求的平整度;钢管内壁的磨蚀破坏主要是水流挟沙较多造成的,应尽量减少磨蚀介质来源;磨蚀严重的应采用抗磨性能良好的环氧基液、不饱和聚脂涂料等涂抹处理。

阅读理解

阅读理解。

How Time Changes around the World?

  Strange things happen to time when you travel because the earth is divided

into twenty-four zones(时区),one hour apart(一个时区相差一个小时). You can

have days with more or fewer than twenty-four hours, and weeks with more or

fewer than seven days. 

  If you make a five-day trip across the Atlantic Ocean(大西洋), your ship

enters a different time zone every day. As you enter each zone, the time changes

one hour. Travelling west, you set your clock back, travelling east, you set it

ahead (向前). Each day of your trip has either twenty-five or twenty-three hours. 

  If you travel by ship across the Pacific. You cross the international date line

(国际日期变更线). By agreement, this is the point where a new day begins.

When you cross the line, you change your calender one full day, backward or

forward. Travelling east, today becomes yesterday. Travelling west, it is

tomorrow.

1. Strange things happen to time when you travel because ______.  

A. no day really has twenty-four hours 

B. no one knows where time zones begin 

C. the earth is divided into time zones

2. The difference in time between zones is ______.    

A. one hour

B. more than seven days

C. seven days

3. If you travel across the Atlantic Ocean, going east, you set your clock ______.

A. one hour ahead in each time zone 

B. one hour ahead for the whole trip

C. one full day back for each time zone

4. From this selection, it seems true that the Atlantic ______.

A. is in one time zone

B. is divided into twenty-four zones

C. is divided into five time zones

5. The international date line is the name for ______.

 A. the beginning of any new time zone

B. any point where time changes by one hour

C. the point where a new day begins

单项选择题