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【单选题】
当管内的液体处于紊流状态时,管截面上流速最大的地方___。
A. 在靠近管壁处;
B. 在截面中心处;
C. 在管壁和截面中心之间;
D. 根据截面大小而不同
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答案
B
解析
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___用于接通和切断管道中的介质。
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B. 调节阀;
C. 逆止阀;
D. 安全阀。
【单选题】
灰斗的充满系数应为___。
A. 0.6:
B. 0.8;
C. 1.0;
D. 0.5以下。
【单选题】
下列哪一种气体是属于易燃气体 ___。
A. 二氧化碳;
B. 二氧化硫;
C. 氧气;
D. 乙炔。
【单选题】
一个工作负责人只能同时发给___工作票。
A. 一 张;
B. 两张;
C. 三张;
D. 实际工作需要。
【单选题】
利用___和继电器配合可实现装置的自动控制。
A. 闸刀开关;
B. 接触器;
C. 熔断器;
D. 高压隔离开关。
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当输送管线长度为___m时,宜采用压力式(仓泵)气力除灰系统。
A. 100~200;
B. 250~400;
C. 450~1000;
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【单选题】
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泵的轴功率P与有效功率Pe的关系是___。
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风机运行时,如因电流过大或摆动幅度大而跳闸,则___。
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闸阀与___的用途基本相同。
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【单选题】
运行中监视电机电流,电流指示应在___。
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【单选题】
在工程热力学中基本状态参数为压力、温度和___。
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【单选题】
减压阀是用来___介质压力的。
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【单选题】
管路运行中起关断作用的阀门应处于___状态。
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【单选题】
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一次电流和一次电压是指___ 。
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【单选题】
在220V电源上串联下列4个灯泡,其中最亮的是___。
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The President is directly voted into office by .
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According to the Constitution, a candidate for President must be .
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All the following except cannot make legislative proposal.
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The following except are guaranteed in the Bill of Rights.
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The Bill of Rights .
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The U. S. Constitution came into effect in .
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【单选题】
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【单选题】
President applied New Deal to deal with the problems of the Great Depression.
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The first shots of the American dependence were fired in .
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“No taxation without representation” was the rallying slogan of .
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The first successful English colony in North America was founded at in .
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The characteristic of dominant American culture is .
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The ImmiWar of Ingrants Act of 1924 restricted the further immigration into the United States, particularly from .
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The largest minority in the United States is the .
A. A. Pacific Islanders
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The native Alaskan population includes the following except the .
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is located on the U. S. –Canadian border between Lake Erie and Lake Ontario.
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Some of the world famous universities like Harvard, Yale and MIT are located .
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