建立了砂轮的球基渐开螺旋面方程和分度球面螺旋线方程,给出螺旋运动参数、螺旋线导程.The mechanism of grinding internal gear of spherical worm emery - wheel is researched.正圆锥螺旋面是正圆柱螺旋面被同轴正圆锥面截得.The ortho cone helicoid was used interrsect intercept by the ortho con...
In 1742 he suffered a fatal attack of smallpox.1742年,他染上了致命的天花.He gave money to the World Health Organisation to help defeat smallpox.他向世界卫生组织提供资金以帮助消灭天花。He gave money to the World Health Organisation to help defeat smal...
The five small arthropod were still very serious pest, especially aphid, scale and whitefly.其中,五小害虫的危害仍然非常严重, 尤其是蚜虫 、 蚧壳虫和粉虱.The outermost layer of cuticle of an arthropod exoskeleton, composed mostly of wax.主要为水生的节肢动物,通...