Which of the listed conditions can lead to cavitation气穴in a centrifugal pump?（） Vapor pockets formed in the suction flow stream。 Rough easing volute surfaces。 Worn wearing rings。 Heavy fluid in the flow stream。
有三个密码子不编码氨基酸（终止密码子），下列哪个是终止密码子？（） UCG。 UAG。 UGC。 UAA。
如何计算打桩工程量？
青泥苔的防治方法是什么？
A centrifugal bilge pump requires priming （）. primarily to lubricate the shaft seals。 due to the inability of this type of pump to lift water to cover the suction (eye) of the impeller。 to initially unload the pump by having its head pressure equal to discharge pressure。 in order to overcome the potential energy of water in the discharge line。
研究地下油水分布状况的目的是为了了解（），以便采取相应的措施。
