问题 多项选择题

某机电工程安装公司承包一电厂的设备安装工程,其中一项工程是直流电动机调速系统安装。机电安装公司派出一名精通机电专业知识的员工,对工程项目合理规划,根据自动控制的基本原理,选用正确的控制系统,按期完成电厂要求的工程任务。

下列关于自动控制系统,说法不正确的是()。

A.恒值控制系统的特点是给定输入一经设定就维持不变,希望输出维持在某一特定值上

B.程序控制系统的特点是给定信号的变化规律是事先不能确定的随机信号

C.随动控制系统的特点就是给定输入是按事先预定的规律变化

D.随动系统的任务是使输出快速、准确地随给定值的变化而变化

E.随动系统的抗干扰性能是这类系统第一位的主要性能

答案

参考答案:B, C, E

判断题
阅读理解

阅读理解

     Tom arrived at the bus station quite early for Paris bus. The bus for Paris would not leave until five

to twelve. He saw a lot of people waiting in the station. Some were standing in line(排队), others were

walking around. There was a group of schoolgirls. Their teacher was trying to keep them in line. Tom

looked around but there was no place for him to sit.

    He walked into the station cafe(咖啡馆). he looked up at the clock there. It was only twenty to

twelve. He found a seat and sat down before a large mirror(镜子) on the wall. Just then, Mike, one of

Tom's workmates came in and sat with Tom.

    "What time is your bus " asked Mike.

     "There's plenty of time yet," answered Tom.

     "Well, I'll get you some more tea then," said Mike.

     They talked while drinking. Then Tom looked at the clock again. "Oh! It's going backward(倒行)!"

he cried. "A few minutes ago it was twenty to twelve and now it's half past eleven."

     "You're looking at the clock in the mirror." said Mike. Tom was so sad(难过). The next bus was not

to leave for another hour. Since then Tom has never liked mirrors.

1. Tom went into the station cafe because______________ .

A. Mike asked him to have a cup of tea    

B. it was quite early and he could find a seat there

C. he didn't like to stay with the schoolgirls

D. he wanted to have a drink with his workmate there

2. What time was it in fact when Tom looked at the clock in the mirror? 

A. Half past twelve  

B. Twenty to twelve    

C. Half past eleven    

D. Half past one

3. From the story we know that when we look at a clock in a mirror, we will find___________ .

A. the time is right    

B .it's going slower    

C. it's going backward  

D. it's going faster

4. Which of the following is true?

A. Tom arrived in Paris on time          

B. The next bus would leave in half an hour

C. After that Tom didn't like clocks any longer

D. Tom looked at the clock in the mirror only once

5. Which of the following is the title(题目) of the story? 

A. The Mirror of the Station        

B. Not A Careful Man

C. Missing A Bus                

D. The Clock In The Mirror