Based on the theory of jet diffusion the formula for predicting the position of dune in equilibrium scour pit are deduced theoretically.

并在此基础上，利用射流扩散理论导出平衡冲刷坑堆丘位置的预报公式。

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And then, according to the condition of limit equilibrium of forces, a formula about non uniform sediment incipient was deduced.

并以该流速公式为基础，按照颗粒极限平衡的受力得出了非均匀沙的起动公式。

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Here, force and deformation of a conical helical spring are discussed based on equilibrium configuration after deformation, and a nonlinear analytic formula is derived.

文中以圆锥螺旋弹簧变形后的平衡位形分析计算其受力和变形，导出了非线性公式。

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