问题 问答题 简答题

为了使设计的玻璃析晶倾向小,选择组成要注意哪些问题?

答案

参考答案:

可以参考有关相图,在接近共熔点或相界线处选择组成点。这些组成点在析晶时会形成二种以上不同的晶体,引起相互干扰,成核的几率减小,不易析晶。同时这些组成点熔制温度也低。应用玻璃形成图时,应当远离析晶区选择组成点,设计的组成应当是多组份的,这也有利于减小折晶倾向,一般工业玻璃其组成氧化物在5~6种以上。

阅读理解

阅读理解。

     Ireland has had a very difficult history. The problems started in the 16th century when English rulers

fried to conquer (征服) Ireland. For hundreds of years, the Irish people fought against the English. Finally,

in 1921, the British government was forced to give independence to the south of Ireland. The result is that

today there are two "Irelands". Northern Ireland, in the north, is part of the United Kingdom. The republic

of Ireland, in the south, is an independent country.

     In the 1840s the main crop, potatoes was affected by disease and about 750,000 people died of bunger.

This, and a shortage (短缺) of work, forced many people to leave Ireland and live in the USA, the UK,

Australia and Canada. As a result of these problems, the population fell from 8.2 million in 1841 to 6.6

million in 1851.

     For many years, the majority of Irish people earned their living as farmers. Today, many people still work

on the land but more and more people are moving to the cities to work in factories and offices. Life in the

cities is very different from life in the countryside, where things move at a quieter and slower pace.

     The Irish are famous for being warm-hearted and friendly, Oscar Wilde, a famous Irish writer, once said

that the Irish were "the greatest talkers since the Greeks". Since independence, Ireland has revived (复兴) its

own culture of music, language, literature and singing. Different areas have different styles of old Irish song

which are sung without instruments. Other kinds of Irish music use many different instruments such as the

violin, whistles, etc.

1. What does the author tell us in paragraph 1?

A. how the Irish fought against the English.

B. how Ireland gained independence.

C. how English rulers tried to conquer Ireland.

D. how two "Irelands" came into being.

2. We learn from the text that in Ireland _____.

A. food shortages in the 1840s led to a decline in population

B. people are moving to the cities for lack of work in the countryside

C. it is harder to make a living as a farmer than as a factory worker

D. different kinds of old Irish songs are all sung with instruments

3. The last paragraph is mainly about _____.

A. the Irish character

B. Irish culture

C. Irish musical instruments

D. a famous Irish writer

4. What can be the best title for the text?

A. life in Ireland

B. A Very difficult history

C. Ireland, past and present

D. the independence of Ireland

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