问题 问答题 简答题

试分析比例带和积分的区别。

答案

参考答案:

δ和Ti过大都会使被调量大幅度偏差增大,但二者是有区别的。Ti值偏大的显著特点是被调量只在横坐标轴的一侧波动,很少越过横轴,而且消除稳态偏差的动作缓慢。δ偏大时,过调量小,曲线漂浮绕大弯,但很快稳定下来。

阅读理解

阅读理解。

     June 5 is World Environment Day. This makes us pay more attention to (更注意) our enveironment and

we need to protect it.

     When Wang Boxuan, a Beijing high schoolboy, uses up (用尽) his exercise books, he does not throw

them away. Each one is stored at his school with hundreds of exercise books given by other students. Then

they are sold to a Beijing paper making factory.   

     The paper is recycled and used again by students and teachers in the school. At the same time, the money

made from the sales goes towards schools in Inner Mongolia for planting trees and grass. This place is one

of the sources (源头) of the sandstorms that often attack Beijing during springtime.   

     Wang's school is one of the schools in the capital that take part in the "green promise (承诺)"

environmental protection (保护) activity. So far, nearly 210,000 students have taken part in the activity,

collecting more than 87 tons (吨) of waste paper.   

     With the Olympic Games coming to Beijing in 2008, students are eager (渴望) to help make the capital a

more pleasant place.   

    "There are some environment problems in the city, such as sandstorms," said Wang. "We should do our

duty and encourage others to do so as well."   

     Vice-Premier (副 * * ) Zeng Peiyan has written a letter to the teachers and students to encourage them

to go on supporting (支持) environmental protection.

1. What do Wang Boxuan and his schoolmates do with the waste exercise books? [ ]

A.Throw them away. 

B.Store and sell them.  

C.Cut them into pieces.

D.Give them to the students in Inner Mongolia.

2. What is the money used for? [ ]

A.Buying new exercise books.   

B.Helping poor students.  

C.Planting trees and grass.   

D.Being stored.

3. What can we infer (推断) from the third paragraph (段落)? [ ]

A.Many years later, students will have no exercise books to use.   

B.Many years later, there will be no waste paper.   

C.Many years later, the sandstorms will be weaker in Beijing.   

D.Many years later, Beijing will be much dirtier.

4. Choose the right order (顺序) according to (根据) this passage?   

    ①Trees and grass were planted.   

    ②Schools in Inner Mongolia received the money.    

    ③Students collected waste paper.   

    ④Vice-Premier encouraged the teachers and students. [ ]

A.③②④①  

B.②①④③  

C.②①③④  

D.③②①④

5. Which is the best title (题目) for the passage? [ ]

A.Planting trees.       

B.Green promises.   

C.Collecting waste paper.   

D.Making money.

单项选择题 A1/A2型题