The thesis surveyed weed species and community structures of linseed fields in the main producing cities of Wuwei,Baiying, Lanzhou, Dingxi, Pingliang and Qi
To ensure the security of structure and decrease the space pollution, explosive bolt catchers are widely applied in separation mechanism and stage separatio
Due to the heavy weight of the launch vehicle and concentrated forces loaded at the lifting lug, lifting and turnover for large launch vehicles are difficul