针对高原地区哨位战士站岗缺氧问题,依据变压吸附制氧基本原理,设计一种适合高原地区哨位使用的小型供氧机.结果表明:产品气的氧体......

We introduce nil 3-Armendariz rings, which are generalization of 3-Armendariz rings and nil Armendaiz rings and investig......

The birth of the new South Africa signifies the end of international isolation ofthe old racist regime, the return of th......