问题 单项选择题

离心泵装置系统,已知该泵的性能曲线(图3-59),静扬程(几何给水高度)Hg=19m,管道总阻抗S=76000s2/m5,水泵的流量Q为()L/s及扬程为()m、效率为(),轴功率为()kW。

A.6.8;24.5;64%;2.55

B.8.8;24.5;64%;3.3

C.8.9;24.5;64%;2.55

D.6.8;24.5;64%;3.3

答案

参考答案:A

解析:

利用H=Hg+SQ2,给出不同的Q得到相应的H后可在泵性能曲线图描出此管路性能曲线,其交点就是泵的工作点,Q=6.8L/s,H=24.5m,对应的效率为64%,轴功率

阅读理解

阅读理解。

     "USA? Britain? Which country is better to study in?" We often hear such discussions. As China opens its

doors, studying abroad has become a dream for many Chinese students. They want to learn about the world.

     It's true that studying abroad can help students develop themselves. Language skills (技能) will improve

and it may be easier to find jobs.

     But there are problems that should be considered (考虑). Language is the first. Students must spend a lot

of time learning another language and getting used to a different culture.

     Students must also learn to live without parents' care and deal with all kinds of things they haven't had to

do before, like looking after themselves. There are reports about Chinese students abroad sinking into an ocean

of difficulties and giving up easily. When they have to take care of themselves, it is hard for students to study

well.

     Finally, studying abroad brings a heavy burden (负担) to the family. For most Chinese parents, the cost

of studying abroad is very high. But is it worth it?

     We know that there are many famous people who succeed in great things through their hard work in

China. Liu Xiang is a good example. Once an American teacher invited him there but he refused. He kept

training hard with his Chinese teacher. He surprised the world when he won a gold medal (金牌) at the Athens

Olympics. So when you wonder which country is better to study in,consider whether studying abroad is the

right choice (选择).

1. From the passage, we learn that many Chinese students dream about studying abroad to ______.

A. taste a new life

B. make a lot of money

C. learn about the world

D. learn to look after themselves

2. The writer thinks ______ should be considered first before students study abroad.

A. places

B. time

C. money

D. language

3. The writer mentions Liu Xiang in the passage in order to tell us that ______.

A. Chinese teachers are better than American ones

B. studying abroad is not the right choice

C. people can also be successful in China if they work hard

D. Liu Xiang was a gold medal winner

4. Which of the following is NOT true?

A. Studying abroad will cost students' families a lot of money.

B. Studying abroad will make it easy for students to learn well.

C. Studying abroad will help students to improve language skills.

D. Studying abroad will bring students a lot of difficulties in their life.

5. This passage is mainly about ______.

A. the question of studying abroad

B. the dream of studying abroad

C. the choice of studying abroad

D. the story of studying abroad

问答题