问题 问答题 简答题

反渗透原理

答案

参考答案:

在一个容器中用一层半透膜把容器隔成两部分,一边注入淡水,另一边注入盐水,并使两边液位相等,这时淡水会自然地透过半透膜至盐水一侧。盐水的液面达到某一高度后,产生一定压力,抑制了淡水进一步向盐水一侧渗透。此时的压力即为渗透压。如果在盐水一侧加上一个大于渗透压的压力,盐水中的水分就会从盐水一侧透过半透膜至淡水一侧,这一现象就称为反渗透。

阅读理解

United States President George W. Bush is expected to issue a directive in the next few weeks. It will give the US Air Force a green light for the development of space weapons, US media reported last week.

This would potentially start a new global arms race, some experts have warned.

To keep that from happening, last Wednesday the White House explained that it was not considering putting weapons in space. It said it was making a shift in US space policy to allow for protection of satellites.

But some defense analysts and arms control advocates argue that the policy will pave the way for the US to put both defensive and offensive  weapons in space.

“No one should be fooled,” said Theresa Hitchens, an American weapons expert.

The US is now restricted by a 1996 directive  signed by President Bill Clinton. Plans for space weapons were vetoed by the Clinton cabinet. The directive emphasized the peaceful use of space , in agreement with almost unanimous global opinion.

The US military has placed importance on space and has sent up numberous satellites for troop communications and to provide intelligence and data to guide bombs to their targets.

The US Air Force wants to develop space- based weapons that could strike targets anywhere in the world within 90 minutes of receiving the order to open fire.

These new weapons under development cover a wide range. They include hunter- killer satellites and orbiting weapons. And they use lasers, radio waves, or even dense metal tubes, known as “ Rods from God”, dropped from space to do the damage.

There are many barriers to the setting up of this kind of program, experts say.

First is the coast. It is estimated that the budget may be US $220 billion to US $ 1 trillion .

The technical difficulties of developing reliable space weapons are also a problem.

And, the program will draw strong criticism from around the world. Experts worry about starting a space arms race.

小题1:Which of the following might be the best title for the passage?

A.US Military Plans

B.The Global Arms Race

C.A Comparison between Two Presidents

D.President George W. Bush and the World Peace小题2:According to this passage, which of the following is NOT true?

A.President George W. Bush supports space weapon development.

B.The space weapon program will threaten world peace

C.Clinton government was poorer than Bush government.

D.The US space weapon project is very expensive.小题3:After reading this passage, it can be inferred that “___________ “.

A.George W. Bush’s directive to be issued will be against global opinions

B.The White House is right in explaining that US new space policy aims to protect satellites

C.US government has little difficulty in developing new space weapons

D.President George W. Bush and Bill Clinton share a lot in common小题4:The author’s attitude towards the coming space weapon development is _______.

A.optimistic

B.critical

C.excited

D.indifferent

单项选择题