流量阀是如何实现流量调节的?如何分类?
参考答案:
流量控制阀是依靠改变阀口通流截面积,即改变液阻实现流量调节的阀。流量控制阀有调速阀、溢流节流阀和分流集流阀等。
The usual way to ensure reliable delivery is to provide the (71) with some feedback about what is happening at the other end of the line. Typically, the protocol calls for the receiver to send back special (72) frame bearing positive or negative (73) about the incoming frames. If the sender receives a positive acknowledgement about a frame, it knows the the frame has arrived safely. On the other hand, a negative acknowledgement means that something has gone wrong, and the frame must be transmitted again.An additional complication comes from the possibility that hardware troubles may cause a frame to (74) completely. In this case, the receiver will not react at all, since it has no any reason to react. It should be clear that a protocol in which the sender transmits a frame and then waits for an acknowledgement, positive or negative, will hang forever if a frame is ever lost due to, for example, (75) hardware.。
A.receiver
B.controller
C.sender
D.customer
在机械制图中,高平齐的基本视图是()。
A.主、左、右、俯视图
B.主、左、右、后视图
C.左、右、仰、俯视图
D.仰、俯、主、后视图