The rate of change of momentum of a body is proportional to the impressed force and takes place in the direction of that force. 一物体动量的变化率与外加力成正比,并与外加力的方向一致。
The nitrate-nitrogen variation rate was one of the important parameters to describe ammonia-nitrogen nitrification status in biological treatment of slightly polluted source water. 硝酸盐氮变化率是描述微污染水源水生物处理系统氨氮硝化状况的重要参数。