问题 问答题 简答题

何谓水锤现象?它有什么危害?

答案

参考答案:

在有压力的管道中,由于某一管道部分工作状态突然改变,使液体的流速发生急剧变化,从而引起液体压强突然大幅度波动,这种现象称为水锤现象。

发生不锤现象时,管内液体压强骤然大幅度波动,所产生的压强可能达到管内原来液体正常压强的几十倍甚至上百倍,可能导致管道系统强烈振动并产生噪声,甚至使管道严重变形或破裂损坏。

阅读理解

阅读理解。

     The Queen's English is now sounding less upper-class, a scientific study of the Queen's Christmas

broadcasts had found. Researchers have studied each of her messages to the Commonwealth countries

since 1952 to find out the change in her pronunciation from the noble Upper Received to the Standard

Received.

     Jonathan Harrington, a professor at Germany's University of Munich, wanted to discover whether

accent (口音) changers recorded over the past half century would take place within one person. "As far

as I know, there just is nobody else for whom there is this sort of broadcast records," he said.

     He said the noble way of pronouncing vowels (元音) had gradually lost ground as the noble upper-

class accent over the past years. "Her accent sounds slightly less noble than it did 50 years ago. But these

are very, very small and slow changes that we don't notice from year to year."

     "We may be able to relate it to changes in the social classes," he told The Daily Telegraph, a British

newspaper. "In 1952 she would have been hears saying 'thet men in the bleck het'. Now it would be 'that

man in the black hat'. And 'hame' rather than 'home'. In the 1950s she would have been 'lorst', but by the

1970s 'lost'."

     The Queen's broadcast is a personal message to the Commonwealth countries. Each Christmas, the

10-minute broadcast is put on TV at 3 pm in Britain as many families are recovering from their traditional

turkey lunch. (传统火鸡午餐).

     The results were published (发表) in the Journal of Phonetics.

1. The Queen's broadcasts were chosen for the study mainly because _____.

A. she has been Queen for many years

B. she has a less upper-class accent now

C. her speeches are familiar to many people

D. her speeches have been recorded for 50 years

2. Which of the following is an example of a less noble accent in English? 

A. "duaty"

B. "citee"

C. "hame"

D. "lorst"

3. We may infer from the text that the Journal of Phonetics is a magazine on _____.

A. speech sounds

B. Christmas customs

C. TV broadcasting

D. personal messages

4. What is the text mainly about?

A. The relationship between accents and social classes.

B. The Queen's Christmas speeches on TV.

C. The changes in a person's accent.

D. The recent development of the English language.

单项选择题