水力最优梯形断面的水力半径是（）。

Every deliberate act of wrongdoing by the master or any of the crew against the ship or cargo，without the authorization or privity of the Shipowner or his agent，is（）.

（）, or drum is used for hauling in or letting out the wires or ropes which will fasten the ship to the shore.

A salvor may be（）the whole or part of the payment due under Salvage Convention to the extent that the salvage operations have become necessary or more difficult because of fault or neglect on his part or if the salvor has been guilty of fraud or other dishonest conduct.

The （） is used for hauling in or letting out the wires or ropes.

Vessels must be（）valid certificate of nationality or certificated of registry or license.

When loading or discharging dry mud or cement，crew members should use goggles and（）.

Effects which are dutiable or subject to prohibitions or restrictions should be declared in （）.

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

矩形断面长直渠道通过流量Q=5m3/s，渠壁粗糙系数n=0.016，底坡i=0.001，按水力最优断面设计，渠道底宽b应为（）m。

已知某渠道设计流量为20.3m3/s，渠底比降ｉ＝1/5000，沿线土质为粘壤土。分别计算最优水力断面、实用经济断面、相对稳定断面的设计水深和底宽。

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。