1. Computer Science DepartmentXi'an Innovation College of Yan'an University Xi'an China
2. School of Computer Science and TechnologyXi'an Jiaotong University Xi'an China
3. School of Computer Science and EngineeringXi'an University of Technology Xi'an China
4. School of Software TechnologyDalian University of Technology Dalian China
5. School of Mathematics and Computer ScienceYan'an University Yan'an China