双曲表面，即通常所称的负曲率，因为它的表面曲线同时有的向上和有的向下，像一个马鞍，也许这样就可以代表宇宙的形状。

The hyperbolic surface, which has so-called negative curvature because its surface curves up and down at the same time, like a saddle, just might represent the shape of the universe.

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吸气时曲左膝，同时双臂向前高举过头，交叉十指，掌心向上，上背部微微拱起。

On the inhale bend your left knee as you bring your arms forward and raise them overhead, fingers interlocked, palms facing up, and upper back arched slightly.

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这两种函数特征都是一曲率凹向上的图象，它表明随着降雨量的增大，单位降雨量所引起的土壤侵蚀量在逐步增大。

Both of the two function are convex curvature images, which shows that with rainfall increasing, the amounts of soil erosion resulting from per unit rainfall increases step by step.

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