back focusing meaning in English

后调焦

Its fundamental is that the ray emitted from a focus ( front ) of elliptical will flock together on the other focus ( back ) by the reflection on the elliptical surface . we set a scatter aperture on the back focus
椭圆柱面的前焦线上是射线源，晶体固定在一个椭圆基底上，其表面构成一椭圆柱面， x射线经晶体衍射后会聚于后焦线上。
Get your weight back as the grade get steeper , moving back focusing the weight on your feet , keeps your weight centered between the tires , this stance would give you confidence and stability , you won ' t get bounced around , and you would be positioned to counteract braking forces , and un - weight the front wheels so it can it can lower over obstacles
当坡度变陡把你的重心往后放，往后移动把重心放在你的双脚，保持你的重心在两轮中间，这个站姿让你有信心而且稳，你不会被弹来弹去，这个姿势可抵销煞车的力量，也让前轮较轻的去过障碍物。