题目内容

离心泵基本方程推导的假设条件:

A. 叶轮为具有无限薄、无限多叶片的理想叶轮
B. 泵内所有液体质点的运动都相同
C. 被输送的是理想液体,液体在叶轮内流动不存在流动阻力

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离心泵的静压头由()构成:

A. 离心力做功
B. 动压头转换

Using the Right WordFill in the blanks with the words given below, changing the form if necessary. Fill in each blank with one word only.1. She was __________ by his sweet words.2. She was so __________ that she went to the kitchen three times to see whether the fish had been cooked.3. The book was __________ the newspaper. That’s why he couldn’t find it at first.4. The __________ wall of the house was badly damaged by the storm.5. The school __________ that it is doing everything it can to cooperate.6. I’m not at all __________ with the service at the restaurant.7. The results of the research were completely __________ to what we had expected.8. There was a sad __________ on her face when she said she had lost her new cellphone.

Working with ExpressionsFill in each of the blanks in the following sentences with a suitable preposition or adverb.1. Although they are roommates, they are not close _______each other.2. For them, there is no social life to speak _______. They are too busy.3. I’m afraid that he will be overcome _______shock on hearing the news.4. Don’t try to travel to too many places _______a time. You will be tired out.5. Our next discussion will focus _______how to improve the city’s air quality.6. Contrary _______what most of us believed, she is married and has already had a baby.7. _______the past three years, he has been attending evening classes to study English.8. He knew it was his carelessness that had caused the accident, but he didn’t want to admit _______it in public.

叶轮的主要作用:

A. 直接给液体传递能量
B. 汇聚液体
C. 转换能量
D. 改变液体流动方向

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