Collins formula,which describes the diffraction of light wave passed through a near-axis optical system,and its inverse calculation expression are presented in this paper.

Based on the beam coherence-polarization matrix and Collins formula,the on-axis polarization property ofGaussian-Schell model beam diffracted through an aperture was studied numerically.

In order to validate the approximate algorithm of Collins formula,the diffraction images for a light wave that passes a thin lens from a quadrate aperture were evaluated numerically and compared with the experimental results.

Problem of public welfare forest's compensation;

Economic valuation and ecological compensation for the public welfare forest in Eastern-Liaoning;

Discussion on financing methods for establishing ecological public welfare forest in Jilin Province

Compensation policy assessment of non-commercial forest;

It is favorable for non-commercial forest protection to assign compensation funds fairly and reasonably.

The division,distribution and main problem of the development of the non-commercial forests in Beijing are analyzed in this article.

This paper aims to probe the strategies for sustainable management of ecological forests by modern forestry theories.

Analysis on 331 literatures on ecological forest demonstrated that more studies were carried out in the southeast China and the focus was on compensation system, classified management and macro_study.

Based on properties of forest community and species distribution of key ecological forest in Zhejiang province,854 typical sample plots were set up according to the climatic region,site conditions,stand type,community structure,age composition of stand and standard trees were surveyed for biomass in the 2 millions hectares key ecological forest.