6Crank J. The Mathematics of Diffusion [ M ]. 2nd ed. Clarendon : Oxford, 1975.
7Chung T S, Shieh J - J, Lau W W Y, et al. Fabrication of multi -layer composite hollow fiber membranes for gas separation [ J ]. Journal of Membrane Science, 1999,152 (2) :211 - 225.