91.  .But the expectation may become s kind of pressure.

92.  So, we need to do something to prevent this abnormal social phenomenon , we need to improve the college student s psychological diaeresis , help they solve mental trouble , encourage they never give up !

93.  It is reported for instance that a chip of paint as small as 1mm in size orbiting in space at speeds of 7 km/s could prove fatal it hits an astronaut in space, a debris of 1 square centimeter, moving at the speed of 15 kilometer per second has the power equal to a grenade.

94.  Their impact speed is 6.8 km/s, which caused a crater and rear wall spollations (Pic. 3).