Dong, Ke2014-10-012014-10-011994-07-01http://hdl.handle.net/20.500.14446/12975application/pdfCopyright is held by the author who has granted the Oklahoma State University Library the non-exclusive right to share this material in its institutional repository. Contact Digital Library Services at lib-dls@okstate.edu or 405-744-9161 for the permission policy on the use, reproduction or distribution of this material.text