The solution of non-linear Schrodiuger (NLS) equation including twophoton absorption in optical fibers, is given by using travelling wave method, and the solution for the propagation characterstics of dark soliton is also discussed in detail.

Some information is got about stress effect through the study and try to explore its mechanism.

This paper attempts to propose a conceptual framework,the parity-intensification effect model,to explain the relationship between fertility policy and the sex ratio at birth,and uses macro data to test this framework.