We present a new method for studying the subthreshold characteristics of nano-scaled MOSFETs,which we call the “regular perturbation method”.

By using normal perturbation method with reasonable boundary conditions, the paper resolves a partial differential equation of the two-dimensional potential of four-terminal silicon pressure transducers, and the analytical expression of the two-dimensional potential is derived accordingly.

The directional solidification in binary system by the small Reynolds number far field flow is studied by the normal perturbation,and the influence of impurity concentration to the temperature field and solid-liquid interface is considered.

perturbation solution of the flow in curved annular pipe with small curvature;

The computation for both creatinine and urea show that the perturbation solution is not only simple but also accurate enough and is a good substitute for the more exact analytical solution.

The first order perturbation solution of the characteristic value and the characteristic function in the bending vibration problems of bridge structures has been deduced by means of the perturbation methods.