The method of calculating the carrying capacity in a large-scale river network is put forward in this paper,and,in terms of the features of the river network,a virtual point source was designed for checking the results.

The flow of virtual resources hidden in grain trade is another important allocation form of water resources since 1990,besides the allocation form of supply and demand side and of basin redeployment.

This paper introduces the present situation of university library, expounds the contents of actual resources and virtual resources and the methods for acquiring actual resources and virtual resources, and elaborates the relation between actual resources and virtual resources.

This paper expounds three main integrating methods taken by network information resources in libraries, and probes into the countermeasures for strengthening construction of virtual resources of key subject in the university libraries from aspects of strengthening construction of database, establishing the navigation pool of key subject, providing individualized information services, etc.

DVMS can be seen as an integrated environment to support remote collaboration of the heterogeneous CAx and VR tools on the internet, a key issue is the virtual resource dynamic integration.

Based on instruments interchangeability, the concept and realization process of virtual resource based on IVI specification are expatiated in this paper.

Ray tracing method based on a virtual source tree;

A virtual source-based dynamic multicast protection algorithm in optical networks;

An idea of virtual information source and the formation of data compression,based on a virtual information source is put forward and a general virtual information source Y of long character bunch of 0 and 1 is set up.