The requirements for silica sol and refractory powder for mold shell in face layer differ from that in back layer.

硅溶胶型壳的面层和背层对硅溶胶和耐火粉料的要求是不一样的。

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If gypsum is adopted as the face layer because the surface is smooth and flat secondary surface-rolling procedure for surface can be omitted.

若采用石膏作面层，其光洁平整的表面可以省去表面的二次抹平工序。

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A example was given by using the face-back-changing weave in the last, explained how to change face layer and back layer to construct the simulating unit matric.

以表里换层组织的模拟方法为例，探讨了在计算机模拟中，表里换层的实现方法。

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As Ms. DeSimone advises, I waited until it dried to wash it off and ended up with a rich emollient layer on my face long after removal.

WSJ: Face Masks: Please Do Try This at Home | Outer Beauty

We had two six-wheeler trucks, too, but it was warmer in the buggy: you have an extra layer of clothing and a full-face helmet.

BBC: Polar express

They could see it in the layer of sweat that was gathering on his face.

NEWYORKER: Ghosts