Improved Rough Set-cloud Model Coupling Method And Its Application In Water Quality Evaluation

Water quality evaluation is to classify and assess the water quality by selecting proper evaluation methods in accordance with the water samples.It is crucial to the water resources management,and further stable production and social sustainable development.Cloud model an uncertain transformation model based on the theory of probability and fuzzy mathematics,which can deal with qualitative conceptions and quantitative descriptions.The rough set is a mathematical tool that portrays incompleteness and uncertainty.By constructing the decision table,the knowledge reduction is carried out on the basis of the equivalence relation,and the weights of the attribute are obtained.Improved rough set is to obtain weights through improved rough set conditional information entropy.The method can avoid the weight being 0 thus ensure the significance of each index in decision making.The improved rough set condition information entropy is combined with the cloud model,and establishes an improved rough set-cloud model coupling method.This method can effectively utilize the advantages of improved rough set condition information entropy and cloud model.In order to verify the validity of the improved rough set-cloud model coupling method,this method is applied to the evaluation of the eutrophication degree of the representative lakes and reservoirs in China and the water quality evaluation of drinking water sources in Southwest China.Results are compared with the single index method and the T-S fuzzy neural network method.The results show that the single index method are too strict.The improved rough set-cloud model coupling method and the T-S fuzzy neural network method have the same evaluation results,which verifies the validity of the method.The improved rough set-cloud model coupling method has a intuitive evaluation process.It takes full account of the influence of each index weight on the final evaluation results,and it is moreconvincing.At the same time,the method can get the degree of determination of the water quality indexes under the water quality index,thus determining the degree of pollution of water quality index.And the method is more able to comprehensively evaluate water quality.