Green Supplier Selection Based On DEA Model Under Pythagorean Fuzzy Environment

With the rapid development of social economy and production technology,people's material standard of living has been greatly improved,and people's ability to utilize and develop nature has been developed unprecedentedly.As a result,serious shortage of resources and worsening of the environment have resulted in threats to the environment on which human beings rely for survival.Global appeal to enterprises and the public to carry out practices environmentally and friendly.Green supply chain management has always been a "green" concept throughout the supply chain,and has been able to flourish since its introduction.Suppliers are the “source” of the entire supply chain,so the evaluation and selection of green suppliers affects the overall performance of green supply chain.The evaluation and selection of green suppliers is a multi-criteria decision-making process.The evaluation indicators include quantitative indicators and qualitative indicators.Quantitative indicators are usually expressed with accurate data,while qualitative indicators are often subject to the subjective influence of decision makers,and it is more convenient to express with fuzzy language or fuzzy numbers.Compared with fuzzy sets and intuitionistic fuzzy sets,Pythagorean fuzzy sets have stronger ability to represent uncertainty and fuzziness,so they can be used more widely.In this thesis,Pythagorean fuzzy sets are used to describe qualitative indicators of fuzziness.In view of the unique advantages of DEA over other decision-making methods,the green supplier selection methods based on DEA model under Pythagorean fuzzy environment are proposed,which not only retain the subjectivity of decision makers but also guarantee the objectivity of decision results to a higher degree.In this thesis,four DEA models under Pythagorean fuzzy environment are constructed based on the actual decision-making problems,and the validity and practicability of the models are verified by the corresponding examples of green supplier selection.The four models are as follows:?1?The general DEA model under Pythagorean fuzzy environment,which is the basis of the other three models,and the data includes exact numbers and Pythagorean fuzzy numbers.?2?The DEA model with undesired outputs under Pythagorean fuzzy environment.There are two common ways to deal with undesired outputs: one is to transform undesired outputs into desired outputs by using the monotone decreasing transformation function,and the other is to treat undesired outputs as inputs.Based on the characteristics of the above two methods,DEA models with exact numbers,Pythagorean fuzzy numbers and undesired outputs are constructed.?3?The DEA model with dual-role factors under Pythagorean fuzzy environment.The model calculation consists of three steps: the first step is to consider the dual-role factors as non-discretionary inputs to solve the efficiency value ?₁;the second step is to consider the dual-role factors as outputs to solve the efficiency value ?₂;the third step is compare the size of ?₁ and ?₂ to determine the efficiency value of the decision making units and the role of the dual-role factors.?4?The DEA model under interval-valued Pythagorean fuzzy environment.The model not only extend the fuzzy environment to interval-valued Pythagorean fuzzy environment,but also some quantitative indicators are interval numbers.