Magnetic dynamic properties of Fe nanorings with small defects were simulated with Monte Carlo method. It is found that hysteresis loops of small defect Fe nanoring have "bistable" characteristics, which is consistent with experimental results. Energy research shows that vortex states appear in the region of local energy minimum. Remanence of defect system changes with defect location: The remanence increases first and then decreases with the increase of Y, and remains relatively stable in the middle region. Spin configuration of the system explains the above phenomenon well.

With Monte Carlo simulation,we study magnetic properties and controllable vortex circulation of asymmetric Co nanorings.Simulated results indicate that magnetic field direction has great effect on magnetic states and magnetization process of asymmetric Co nanorings.It is found that direction of the magnetic-moment circulation in asymmetric nanorings can be controlled by gradient of the domain-wall energy along the circumference in cooperation with an external magnetic field.It is found that size effect is obvious on stability of vortex-type state and magnetization process of asymmetric nanorings.

A mathematical model for multiple scattering of light conducted in polymers is presented.Based on the Mie scattering theory,Monte Carlo method is employed and a program is developed.By simulating scattering of a photon,we simulate problem with light source as laser or CCFL.Distribution of light out of source in polymers is obtained by statistic calculation.The results show that a plane light in polymer can be obtained with body scattering principle and intensity distribution of light escaping from polymer can be well controlled.