Based on the models and the free-form surface formula, the moving envelope surface of ball-end mill is obtained by means of matrix calculating, the topography is modeled and simulated.

基于自由曲面方程，由矩阵运算得出刃线运动包络面，对球头铣刀加工的表面形貌进行了建模和仿真。

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Puffs of dust were evidence of the ball breaking the surface of the pitch as it landed - and batting last should be awkward.

BBC: Jonathan Agnew column

Then there's the vertical bounce of the ball which is affected by the stiffness of the surface.

BBC: SPORT | Tennis | Rules and Equipment | On the rebound

Then, on a smooth. flour-free surface, roll the ball under the palm of your hand until the dough is smooth and firm -- about 1 minute.

CNN: Pizza Dough