问题 问答题

可靠性何谓抽样寿命截尾试验中的有替换试验和无替换试验?

答案

参考答案:可靠性截尾试验可分为有替换和无替换两种。有替换试验是在试验中每发生一个样品失效,即用同一批中的新样品替换,使总的试验样品数保持不变(2.5 分)。反之,若在试验过程中失效样品撤下后,不再补充新的,只对残存样品进行试验,则称为无替换寿命试验。(2.5 分)

阅读理解

阅读理解。

     The students were having their chemistry class. Miss Li was telling the children what water was like.

After that, she asked her students, "What's water?" No one spoke for a few minutes. Miss Li asked again. "Why don't you answer my question? Didn't I tell you what water is like?"

     Just then a boy put up his hand and said, "Miss Li, you told us that water has no color and no smell.

But where can we find Such kind of water? The water in the river behind my house is always black and it

has a bad smell. " Most of the children agreed with him.

     "I am sorry, children," said the teacher."Our water is getting dirtier and dirtier. That's a problem. "

1. The students were having their _______ class.

A. English                  

B. Chinese

C. chemistry                  

D. math

2. Miss Li was telling the children what          __was like.

A. water                    

B. air

C. earth                      

D. weather

3. A boy said, "The water in the river behind my house is always      ____  .

A. whit e                    

B. black

C. clean                    

D. clear

4. Most of the children _       __  the boy.

A. agreed with            

B. wrote to

C. heard from              

D. sent for

5.The water in the river has color and smell because it is getting         ___.

A. more and more        

B. less and less

C. cleaner and cleaner      

D. dirtier and dirtier

单项选择题