同一台泵用于输送密度分别为ρ1和ρ2的液体时,保持转速不变且流动相似,其对应的扬程分

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问题:

同一台泵用于输送密度分别为ρ1和ρ2的液体时,保持转速不变且流动相似,其对应的扬程分别是H1和是H2,对应的轴功率分别为P1和P2,若ρ1>ρ2,则下列关系式中正确的是()。

A、H1>H2P1=P2

B、H1=H2P1>P2

C、H1>H2P1>P2

D、H1=H2P1=P2

考点:电气工程公共基础第二节流体动力学基础第二节流体动力学基础题库
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社会制度的构成要素有:()、规则系统、()和设备系统。

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“氢能”是人类未来最理想的新能源之一。

(1)实验测得,1 g氢气燃烧生成液态水时放出142.9 kJ热量,则表示氢气燃烧热的热化学方程式为__________________________。

(2)利用核能把水分解制氢气,是目前正研究的课题。如图是其中的一种流程,流程中用了过量的碘(提示:反应②的产物是O2、SO2和H2O)。

完成下列反应的化学方程式:反应①________________;反应②________________。此法制取氢气的最大优点是____________________。

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克劳斯反器入口温度对装置有何影响?

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2006年浙江省外商直接投资项目数为3583个,合同外资金额为1910261万美元。实际外资金额为888935万美元。2007年直接投资项目数为2919个,合同外资金额为2040043万美元,实际外资金额为1036576万美元。2008年直接投资项目数为1858个,合同外资金额为1781995万美元,具体数据如图1所示:

2008年浙江省外商直接投资的合同外资金额比实际外资多()

A.178.2亿美元

B.100.7亿美元

C.77.5亿美元

D.61.9亿美元

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Statuses are marvelous human inventions that enable us to get along with one another and to determine where we "fit" in society. As we go about our everyday lives, we mentally attempt to place people in terms of their statuses. For example, we must judge whether the person in the library is a reader or a librarian, whether the telephone caller is a friend or a salesman, whether the unfamiliar person on our property is a thief or a meter reader, and so on.

The statuses we assume often vary with the people we encounter and change throughout life. Most of us can, at very high speed, assume the statuses that various situations require. Much of social interaction consists of identifying and selecting among appropriate statuses and allowing other people to assume their statuses in relation to us. This means that we fit our actions to those of other people based on a constant mental process of appraisal and interpretation. Although some of us find the task more difficult than others, most of us perform it rather effortlessly.

A status has been compared to ready-made clothes. Within certain limits the buyer choose style and fabric. But an American is not free to choose the costume of a Chinese peasant or that of a Hindu prince. We must choose from among the clothing presented by fit, as well as by our pocketbook. Having made a choice from minor adjustments, we tend to be limited to what the stores choice among them is limited.

In the last sentence of the second paragraph, the pronoun "it" refers to ()".

A.fitting our actions to those of other people appropriately

B.identification of other people’s statuses

C.selecting one’s own statuses

D.constant mental process

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