The diameter of a sphere is four times the focal length of a concave mirror cut from it.
凹面镜如果是从圆球上切下来的，圆球的直径会是凹面镜焦距的四倍。
Have a cut, mold, polishing, concave, deep carving and sandblasting the surface of a complete production line of laser engraving.
拥有切、模、抛光、打凹、表面喷砂深雕及激光内雕的完整生产流水线。
On seismic profile cross-cut the channel, it generally presents as a lenticle with flat top and concave bottom and has the character of infilling in reflection.
河道砂岩体在横切河道的地震剖面上一般表现为充填反射状的顶平底凹的单透镜体；
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