Once the woman is on the cross-court side, she must lower her center of gravity and get her racket head up in front of her.

一旦女选手斜线后退到一个半场，她一定要降低自己的重心和把拍子举过她的头顶。

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When a curved beam is bending in the plane of the curvature, the neutral axis of cross section is not identical with the axis of gravity due to the influence of the initial curvature.

由于曲率的影响，曲线梁在其曲率平面内弯曲时的中性轴不通过横截面的形心。因此弯矩在形心处要引起正应力，从而引出所谓“等效轴力”的概念。

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