问题 问答题 简答题

常见的破碎方法有几种?

答案

参考答案:

(一)压碎法:利用两破碎工作面逼进物料时加压,使物料破碎。这种方法的特点是作用力逐渐加大,力的作用范围较大。

(二)劈碎法:利用尖齿楔入物料的劈力,使物料破碎,其特点是力的作用范围较为集中,发生局部破裂。

(三)折断法:物料在破碎时,由于受到相对方向力量集中的弯曲力,使物料折断而破碎;这种方法的特点是除了在外力作用点处受劈力外,还受到弯曲力的作用,因而易于使矿石破碎。

(四)磨剥法:破碎工作面在物料上相对移动,从而产生对物料的剪切力。这种力使作用在矿石表面的,适于对细小物料的磨碎。

(五)冲击法:击碎力是瞬间作用在物料上,所以又称为动力破碎。

完形填空

【1】People study their family history for different reasons. For some, genealogy(家谱学) is important to their religion. Other people who get involved in genealogy may want to confirm stories they heard about a family member. Some people say their interest in genealogy came from an eight-part series on television called Roots. Roots was first broadcast in 1977 and was based on a book which describes how the author’s ancestor, long ago in Africa, as slave was brought to America. After watching Roots, many Americans wanted to study ________________.

【2】Finding family roots is not always easy. So how exactly does someone start a genealogical research ?

【3】Experts say you should start with yourself. Write down your own history. One idea is to ask your parents what they can remember about their parents or grandparents. You can often find a lot of information in family pictures, letters and other documents.

【4】Resources on local history may also provide useful information. Large libraries may have hundreds of helpful books. In the United States, several groups have large collections of genealogical materials. These collections are open to the public.

【5】Governments often have many helpful records of genealogists. Governments usually keep official copies of birth, marriage and death records. Local governments may have copies of wills. These statements of final wishes often contain details about a person’s life and wealth.

【6】Today, many people use the Internet. There are thousands of web sites related to genealogy. They can guide people to historical records and provide information about how to write down their family’s history.

小题1:What is the passage mainly about ? (no more than 10 words)

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小题2:How many ways are mentioned in how to start a genealogical research ? (no more than 2 words)

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小题3:Fill in the blank in Paragraph 1 with proper words. (no more than 6 words)

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小题4:Why should people ask governments for help in the study of genealogy ? (no more than 8 words)

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小题5:What does the underlined word “They ” (Paragraph 6 ) probably refer to ? (no more than 5 words)

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