A numerical approach is presented for simulating the quality of natural ventilation in an apartment unit with three bedrooms and one hall by using algorithm of Simpler and Artificial compressing method based on blocked interior spaces,which obtained the main data on the distribution of laminar-flow field in a housing unit. The application software created accordingly applies universally,which provides an effective means for an alyzing,optimizing and evaluating the quality of natural ventilation in housing design.

As a continuation of our previous research this paper puts the stress on numerical simulation of tigher overvoltage induced by nonsynchronous closing. Main result as follow: Because of ordinary differential equation which is the mathematical model of preceding closing phases has two large harmonic solutions, so it implys possibility transformed from little harmonic solution to large one. Lagging currents i₁(t-τ₁), i₂(t-τ₁) play an important role to help intensify the billows and Waves in this transformation process.

In this paper, some unkown physical processes in power systems are dissclosed by using the methods of Runge-Kutta and Galerkin. Such as the connection between the low-frequency resonances and the abnormity of magnetic hysteresis loop, the polarization of subharmonic bifurcations, the frequency region where the subharmonic resonances together with harmonic resonances exist and so on.

The approximate analysis of differential systems by applying the theory of regional analysis, is described. It supplies a formularization and calculating programme for algebraic limit cycle of second degree in a type of differential systems of third degree, and also for critical value of damping resistance in power systems. This new method simplifies the traditional method, hence it is acceptable and applicable for engineers. Finally, a few of examples are given based on this method.