Ji Jinnan1,Zhang Zhiqiang1,Fourcaud Thierry2,Lao Erping3
1.College of Soil and Water Conservation,Beijing Forestry University, Key Lab.of Soil & Water Conservation and Desertification Combating,Ministry of Education,100083;2.Sino-French Laboratory for Computer Sciences Automation and Applied Mathematics,100080;3.Beijing Jiaotong University,100044: Beijing,China