Hybrid mathematical set models for uncertainty problems and decision-making approaches for the Covid-19 pandemic

The thesis consists of five main sections. In the first section, the subject of the thesis is explained and general concepts related to uncertainty problems are reminded. In the second section, the literature information of the concepts used in the thesis is given in detail. In the third section, the basic definitions and theorems used in the thesis are given. The fourth section is the original part of the thesis and is divided into seven subsections. In the first and second subsections, some inadequacies for fuzzy parameterized soft sets and bipolar soft sets have been identified and new hybrid approaches have been proposed instead of these mathematical models. In the third subsection, bipolar soft topological structures are studied and the concept of bipolar soft ordered topological structures is defined. In the fourth subsection, a better approach to uncertainty problems is proposed by generalizing the Q-neutrosophic soft relations. In the fifth and sixth subsections, some determinations were made on the Covid-19 pandemic disease. In addition, some decision-making approaches have been built to prevent the spread of the epidemic. Finally, in the seventh subsection, new mathematical approaches focusing on the factors affecting the parameters are proposed. In the fifth section, the results and recommendations are presented.