问题 问答题 简答题

在电渗析操作过程中,工作电流密度超过极限电流密度会出现什么现象,如何消除?

答案

参考答案:

(1)在操作过程中,工作电流密度超过极限电流密度会出现浓差极化现象。

(2)消除浓差极化现象的方法有:

①控制操作电流密度小于极限电流密度(或使i②定期倒换电极;

③增大水流速度;

④定期酸洗;

⑤进行预处理。(⑤可不答)

阅读理解

Jurassic Park could become a reality with dinosaurs making a comeback after a discovery last week. Scientists found remains of a dinosaur’s blood vessels(血管)and cells .In theory, DNA from these cells could be used to clone the longdead dinosaur.

A team from North Carolina State University found the remains in a fossil(化石)of the leg bone of a Tyrannosaurus rex(暴龙)in Montana, US.

The last dinosaurs on Earth died some 65 million years ago, but they left bits of themselves behind wherever they lived. Around the world ,dug-up bones and fossils have given scientists many ideas about what the animals were like.

Preserved by minerals, the newly discovered leg bone was hard. So the scientists used a liquid to dissolve(溶解)the minerals. A week later, the remaining material was soft and stretchy(有弹性的),which surprised the researchers.

Some of the materials appeared to be a network of blood vessels. Out of these, the researchers were able to squeeze(挤出)tiny , round, dark-red and deep-brown structures that seemed to be ancient blood cells.

Scientists are overjoyed by this discovery because most fossils come from hard body parts, like bones and shells, which last a long time. Soft tissues, like skin, muscle, and organs are very hard to find because they tend to break down more quickly.

Scientists think that the new discovery will help them to better understand how fossils form. Future finds should also help flesh out how the dinosaurs lived.

They were also very excited by the possibility of having some dinosaur DNA.From that scientists could create a real life “Jurassic Park”.

In the Hollywood movie, scientists reproduced dinosaurs from the DNA they found in a mosquito fossil and disaster soon followed.

小题1:Scientists are excited _________________________ .

A.because they have got dinosaur DNA

B.about making a movie called “Jurassic Park”

C.because they found the liquid to dissolve fossils

D.because it,s very hard to find soft tissues in fossils小题2: The latest discovery can tell us       .

A.what the animals were like

B.how fossils form

C.how the dinosaur lived

D.how to get dinosaur DNA小题3:What does the underlined phrase“flesh out”mean in the article?

A.add more details or information to

B.take more photos of

C.make the public know more about

D.find the answer to小题4:Why is the latest discovery very important?

A.It could make it possible to make dinosaurs return to the former position.

B.It could throw light on how dinosaurs lived many years ago.

C.It could prove what dinosaurs were like.

D.It could explain why dinosaurs died some 65 million years ago.

单项选择题