第2题
A.初始上电和正常工作期间,RST端维持2个机器周期的高电平
B.初始上电和正常工作期间,RST端维持20毫秒的高电平
C.初始上电需20毫秒,正常工作期间只需2个机器周期的高电平
第4题
平面色谱中,相对比移值Rst是样品移行距离与______移行距离之比,它可消除______误差。
第7题
某笼型异步电动机用来拖动一生产机械(如电葫芦),为了平滑地慢加速起动,电动机定子一相内接入电阻Rst,如下图所示。电动机的数据为:PN=7.5kW, U1N=380V,nN=905r/min, I1N=19.3A,KI=4.4,Kst=3,cosψN=0.44。设起动转矩为0.7TN,试计算起动电阻Rst及流过Rst的起动电流。
第8题
某笼型异步电动机用来拖动一生产机械(如电葫芦),为了平滑地慢加速起动,电动机定子一相内接入电阻Rst,如下图所示。电动机的数据为:PN=7.5kW, U1N=380V,nN=905r/min, I1N=19.3A,KI=4.4,Kst=3,cosψN=0.44。设起动转矩为0.7TN,只是sinψ≈1。如果将下图中的Rst用起动电抗器Xst代替,以达到同样的慢加速起动的目的。如果要求起动转矩减到0.7TN,试计算起动电阻Xst及流过Xst的起动电流。
第9题
选出应填入下面一段英语中______内的正确答案。
When the system upon which a transport entity is running fails and subsequently restarts, the(1)information of all active connections is lost. The affected connections become half-open, as the side that did not fail does not yet realize the problem.
The still active side of a half-open connections can close the connection using a(2)timer. This timer measures the time transport machine will continue to await an(3)of a transmitted segment after the segment has been retransmitted the maximum number of times. When the timer(4)the transport entity assumes that either the other transport entity or the intervening network has failed. As a result, the timer closes the connection, and signals an abnormal close to the TS user.
In the event that a transport entity fails and quickly restart, half-open connections can be terminated more quickly by the use of the RST segment. The failed side returns an RST i to every segment i that it receives. When the RST i reaches the other side, it must be checked for validity based on the(5)number i, as the RST could be in response to an old segment. If the reset is valid, the transport entity performs an abnormal termination.
第10题
A.定义一个自定义符号的程序段
B.定义一个自定义段名的程序段
C.定义一个自定义运算的程序段
D.定义一个自定义数组的程序段