3.1. Fuzzy Sets and Fuzzy Numbers
Definition 1: A Fuzzy set a in a universe of discourse X is characterized by a
membership function a ( x ) which associates with each element x in X , a real number in
the interval [0, 1]. The function of ( ) a x is termed the grade of membership of x in a .
The present study uses triangular Fuzzy numbers. a can be defined by a triplet
1 2 3 ( a , a , a ) . Its conceptual schema and mathematical form are shown as below: