The inflexion is the second differential of the speed curve and the physical meaning is the same to the jerk, so the jerk is introduced into the control model of anti-skid system.

拐点是制动曲线的三阶导数，它的物理意义和冲动不谋而合，这也是本文在防滑器控制模型中引入冲动物理量的原因之一。

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The report argues that knee-jerk responses to past tragedies have led to a defensive child protection system that tries to prevent mistakes by setting performance indicators and procedures for what needs to happen.

BBC: Analysis: Less heat, more light on child protection