The fitted line in the figure is a 3rd-degree polynomial, but any sort of smoothing would tell you that there is a massive upward trend.
拟和线是一个三次多项式的形式，但是任何形式的平滑都会告诉你有一个大的上升趋势。
2
Trend term displacement is determined by the potential energy and constraint condition of the slope and is predicted by displacement polynomial function.
趋势项位移由边坡的势能和约束条件所决定，利用多项式位移函数进行拟合预测。
3
Orthogonal polynomial approximation is proposed to estimate the nonlinear deterministic trend and then the residual is used to test the unit root.