By introducing proper stretchy variable and constructing boundary layer function, it concludes N-order approximate solution, and using theory of differential inequality, uniformly validity of asymptotic expansion is proved.

• 通过引进适当的伸长变量，构造边界层函数，得到了解的N阶近似值，并利用微分不等式理论证明了解的渐近展开式的一致有效性。