问题 问答题 简答题

试述混合的机制。

答案

参考答案:

(1)对流混合:固体粒子群在机械转动的作用下,产生较大的位移而进行的总体混合。

(2)剪切混合:由于粒子群内部剪切力的作用结果,产生滑动面,破坏粒子群的凝聚状态而进行的局部混合。(3)扩散混合:相邻粒子间产生无规则运动时相互交换位置所进行的局部混合。

阅读理解

According to sociologists(社会学家),every modern industrial society has some form of social stratification(阶层).Class,power and status are important in deciding people’s rank in society.

Class means a person’s economic position in society.A commonly used classification is lower class,middle class and upper class.While sociologists disagree on how these terms should be exactly defined,they do describe societies like the United States quite well.One study shows that 53% of Americans belong to the lower class,46% the middle class,and 1% the upper class.Interestingly,a surgeon earning $500,000 a year and a bus driver earning $50,000 a year both regard themselves as the middle class!

Power refers to the amount of control a person has over other people.Obviously,people in positions of great power (such as governors) exercise(行使)big power,but people who take orders from others have less power.Power and class do not always go hand in hand,however.For example,the governor of a state has great power,but he or she may not belong to a corresponding (相应的)economic class.Generally,however,there is a relationship between power and class.To our knowledge,there aren’t too many people who aren’t millionaires in the U.S.Senate!

Status is the honor or respect attached to a person’s position in society.It can also be affected by power and class,but not necessarily so.For example,a university professor may have a high status but not belong to a high social class or have a lot of power over others.

小题1:What can we learn about“the middle class”from Paragraph 2?

A.People earning $50,000 a year belong to the middle class.

B.Nearly half Americans belong to the middle class.

C.People generally consider bus drivers as the middle class.

D.Sociologists have a clear definition of the middle class.小题2:According to the text,we know that________.

A.power and class do not always correspond with each other

B.status refers to a person’s economic position in society

C.people with high status have a lot of control over others

D.class is less important in deciding a person’s social rank小题3:.Which of the following shows the structure of the whole text?

单项选择题