杯水的上部应该是凹面的。

The water surface in the cup is slightly vaulted upward.

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目的：确定正常个体中上下眼睑周围泪河凹面的昼夜变化。

PURPOSE: To determine diurnal variation of tear menisci around upper and lower eyelids in normal subjects.

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用圆柱和放大的叶片做模型，模拟叶片前缘和叶盆凹面的流动。

Cylinder and enlarged blades are used as test models for simulating the leading edge and concave surface of the blade.

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