在液压系统中为什么要设置背压回路?可以做背压阀的元件有哪些?

可以在（）阶段采用Make-or-buy决策分析。

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.

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

顺序阀在系统中作卸荷阀用时，应选用外控内泄式型，作背压阀时，应选用（）型。

顺序阀在系统中作卸荷阀用时，应选用（）型，作背压阀时，应选用内控内泄式型。

单向阀可以用来作背压阀。