Variable fuzzy sets and their application to comprehensive risk evaluation for flood-control engineering system

From a global system view,a variable fuzzy set method was presented to develop a comprehensive evaluation model for flood-control engineering system.The method can scientifically and reasonably determine the relative membership functions of each evaluation index related to the flood-control system within different level intervals.The method can also determine the weight of each index by establishment of a two-factor quantitative comparison model for the significance of the indexes,and further obtain the characteristic value for comprehensive evaluation of risk degree for river basin flood control engineering system.Some examples were given to verify the scientificity and rationality of the present method.Moreover,the formulas for dependence functions based on the concepts of distance and displacement in extenics(matter-element analysis and matter-element model)were verified to be incorrect,and could not be used for comprehensive risk evaluation of floodcontrol engineering system.