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A multicriteria intuitionistic fuzzy group decision-making method  363


                                                1
                                                                        (13.12)
                                  ραðÞ ¼
                                         0:51 + π α Þ 1 μð  α Þ
                                           ð
                                                1
                                                                        (13.13)
                                        0:51 + π β 1 μ  β
                                  ρβðÞ ¼
              (1) α¼(μ α ,υ α ,π α ) is superior to β¼(μ β ,υ β ,π β ) when ρ(α)>ρ(β).
              (2) α¼(μ α ,υ α ,π α ) is equivalent to β¼(μ β ,υ β ,π β ) when ρ(α)¼ρ(β).
              (3) α¼(μ α ,υ α ,π α ) is inferior to β¼(μ β ,υ β ,π β ) when ρ(α)<ρ(β).
              Definition 5 Distance between two intuitionistic fuzzy numbers (Xu and
              Yager, 2008)
              Suppose α¼(μ α ,υ α ,π α ) and β¼(μ β ,υ β ,π β ), the distance between α and β
              can be determined by Eq. (13.14).


                                   1


                                       μ  μ + υ α  υ β + π α  π β       (13.14)


                           ð
                          d α, βÞ ¼    α   β
                                   2
              Definition 6 Similarity between two intuitionistic fuzzy sets (Xu, 2007b)
              Assume that X¼{α 1 ,α 2 , …,α n } be a universe of discourse, the similarity
              between two intuitionistic fuzzy sets A¼{hα j ,μ A (α j ),υ A (α j )ijα j 2X} and
              B¼{hβ j ,μ A (β j ),υ A (β j )ijβ j 2X} can be determined by Eq. (13.15).
              SA, BÞ ¼ 1
               ð
                                                                              3 1
                  n                                                             2
               2
                 X                    2                  2                  2
                      μ α j  μ

                                                                         j
                                                      j
                                   j


                         A      B  β   + υ A α j  υ B β   + π A α j  π B β
               6                                                              7
                 j¼1
               6                                                              7
               6                                                              7
                  n
               6                      2                  2
                 X                                                          2 7
                      μ α j + μ

               4                                                              5
                                                      j
                                                                         j
                                   j


                         A      B  β   + υ A α j + υ B β   + π A α j + π B β
                 j¼1
                                                                        (13.15)
              2.2 Similarity measure-based multicriteria
              decision-making method
              The multicriteria intuitionistic fuzzy group decision-making (MCIFGDM)
              method for sustainability ranking of biofuel production pathways was devel-
              oped in this section, and the MCIFGDM method was based on the similarity
              measure. Let {A 1 ,A 2 , …,A m } be a discrete set of alternative biofuel produc-
              tion pathways, {C 1 ,C 2 , …,C n } be a set of criteria for sustainability assess-
              ment of biofuel production pathways, the developed MCIFGDM method
              was presented in the following steps:
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