二 . , the effection of back - propagation artificial neural network the ann model fitted very well in the study of typhoid fever and paratyphoid fever , viral hepatitis and epidemic cerebrospinal meningi - tis , yet , it did n ' t fit so well in the study of endemic typhus and en - demic encephalitis b . piscuss 1 在bp人工神经网络的预测效果方面，呼吸道传染病百日咳和猩红热、消化道传染病伤寒副伤寒和细菌性痢疾模型的预测效果较好。虫媒传染病的预测效果最差。在干早地区的传染病预测方面， bp神经网络模型在回代和预测效果方面均优于传统的多元逐步回归模型。
2.
The writer has been told not merely once by prot . dai nanhai t hat the study of chinese photoxylographical printing is a very hard n ut to crack in the study of the edition of anciant chinese books . wh en was it invented ? as opinions always vary on foreign and chinese aca demic circles ， no unanimous conclusion can be drawn . judged by material ， technological ， and written languags conditions essential to its invention ， it was probably invonted in late sui or northern and southern dynas ties ， but to say it invented in eastern han is absolately impossible 戴南海教授不止一次的给我说:中国雕版印刷术是研究中国古籍版本学的一道大难题。究竟发明于何时，中外学界历来众说纷云，莫衷一是。从印刷术发明的必须具备的物质条件、技术条件和文字条件来衡量，也许在隋或南北朝晚期。
