高压泵提供了反渗透的推动力，应在其出口管路上设置止回阀和电动慢开阀。前者可防止停机时

如图（甲）所示，一对平行光滑轨道放置在水平面上，两轨道间距L=0.20m，电阻R=10Ω，有一质量为1kg的导体杆平放在轨道上，与两轨道垂直，杆及轨道的电阻皆可忽略不计，整个装置处于垂直轨道平面向下的匀强磁场中，现用一外力F沿轨道方向拉杆，使之做匀加速运动，测得力F与时间t的关系如图（乙）所示，试求：

（1）杆运动的加速度a．

（2）磁场的磁感应强度B．

（3）导体杆运动到第20s时，电阻R的电功率．

（4）若改为恒定拉力作用，但仍要导体棒以该加速度做匀加速运动，你对该装置能提出什么合理的改进措施，请做简要说明．

9的相邻数是（    ）和（    ）。

属于氮苷类化合物的是（）

A．红景天苷

B．水扬苷

C．芥子苷

D．腺苷

E．牡荆素

患者女性，35岁，因车祸致全身多发伤，体检：BP：55/40mmHg，HR：112次／分，T：36.1℃。面色苍白、脉搏细弱，四肢冷、出汗，X线片示右下肢粉碎性骨折，颅骨骨折。入院诊断为：低血容量性休克，该患者处于休克的（）。

A.休克初期

B.休克期

C.休克后期

D.微循环衰竭期

E.以上都不对

A punctual person is in the habit of doing a thing at the proper time and is never late in keeping an appointment.
The unpunctual man, on one hand, never does what he has to do at the proper time. He is always in a hurry and in the end loses both time and his good name. A lost thing may be found again, but lost time can never be regained. Time is more valuable than material things. In fact, time is life itself. The unpunctual man is for ever wasting and mismanaging his most valuable asset as well as other’s. The unpunctual person is always complaining that he finds no time to answer letters, or return calls or keep appointments promptly. But the man who really has a great deal to do is very careful of his time and seldom complains of want of it. He knows that he can not get through his huge amount of work unless he faithfully keeps every piece of work when it has to be attended to.
Failure to be punctual in keeping one’s appointments is the sign of disrespect towards others. If a person is invited to dinner and arrives later than the appointed time, he keeps all the other guests waiting for him. Usually this will be regarded as a great disrespect to the host and all other guests present.
Unpunctuality, moreover, is very harmful when it comes to do one’s duty, whether public or private. Imagine how it would be if those who are put in charge of important tasks failed to be at their proper place at the appointed time. A man who is known to be habitually unpunctual is never trusted by his friends or fellow men.

According to the third paragraph, when you are invited to dinner, you should arrive there ______.

A. after other guests have arrived
B. before all other guests
C. at the appointed time
D. after the host has got things ready