For small displacement u, the oscillator is a Duffing-type cubic non-linear oscillator, while for large displacement u, the oscillator approximates to a linear harmonic oscillator.

• 所谓达芬－谐波振子是指当位移远小于1时，系统可化为三次非线性振子，而当位移远大于1时，该系统则化为线性谐波振子。