The Research Of Evidence Theory And Its Application In Water Quality Assessment

Evidence theory has been widely applied to different fields for its advantages of expression and combination of uncertain problems. However, due to its limitations, such as invalidation of complete conflict, independence assumption on evidences and exponential increase of the combination rules' operation with the increase of attribute space dimension, scholars have brought forward lots of improving methods of evidence theory, which aim at some special fields. Conflict assignment of those methods is comparatively fixed and most methods aren't generally applicable. The thesis puts out improvements of combination rules of conflict assignment on total evidences(CATE) and its proximate combination rules with the key point of conflict management. The improved combination rule helps to increase the rationality of conflict management through the change of support levels on each evidence with the change of evidences space. The improved rules have better result when conflict exit, and are generally applicable.The main research items of the thesis are listed as follows. First of all, the interpretation of the basic concepts of evidence theory and their geometrical significances, the model explanation of evidence theory and the expectation of combination rules. Then, a general overview of the existing improving methods of combination rules, and the presentation of a dynamic improvement of conflict management with the check of its rationality in respect of the expectation of combination rules and example analyses. And the paper also provides a frame of an evidence theoretical water quality assessment with premier fuzzy evaluation on the basis of researches on the existing the ways of water quality assessment through the application of the new method into water quality assessment. Last but not the least, the paper program the process of evidence theoretical water quality assessment based on the XML.