http://reply.papertrans.cn/3/218/21749/21749-31.png
http://reply.papertrans.cn/3/218/21749/21749-32.png
http://reply.papertrans.cn/3/218/21749/21749-33.png
Submitted on: 09 May 1998.
Revised on: 17 May 1998.
Accepted on: 11 June 1998.
Membranes
http://reply.papertrans.cn/3/218/21749/21749-35.png
http://reply.papertrans.cn/3/218/21749/21749-36.png