Hesitant T-spherical fuzzy sets and their applications in decision-making

This thesis consists of eight sections. In Section 1, detailed literarature review and motivation of the paper are presented. In Section 2, generalizations of fuzzy sets. In Section 3, the concept of the hesitant T-spherical fuzzy (HTSF) set, the score and accuracy functions of the hesitant T-Spherical fuzzy elements, and the set operations between the hesitant T-Spherical fuzzy sets are defined and examples of them are given. In Section 4, Dombi operators among HTSF elements are introduced and based on Dombi operators, hesitant T-spherical Dombi fuzzy (HTSDF) weighted arithmetic averaging operator, HTSDF weighted geometric averaging operator, HTSDF ordered weighted arithmetic averaging operator and HTSDF ordered weighted geometric averaging operator are defined and some properties of them are investigated. In Section 5, a multi-criteria group decision making method has been developed in the HTSF environment and an algorithm for the proposed method is presented. In addition, an example of personal selection is given to demonstrate the operation of the proposed method. In Section 6, an analysis by the parameter in the aggregation operators presented is presented. In Section 7, a table and commentary showing comparisons between the generalizations of fuzzy sets are given. In Section 8, some explanations about the obtained results and works to be presented in the future.