用pdetool解得:
http://wenku.baidu.com/link?url=kJhaHFqANbCZKUpJlSUUxMW4T6fziUjWjRMQopZ519oGXVBM57JnWZeDBi9XGWbWEPAsfa9At75RcW0mxitkuNF3UgnnCOHwOu04zygWmYS