

Articles
by
M.B. Fakhrzad 
Total Records (
2 ) for
M.B. Fakhrzad 





M.B. Fakhrzad
,
Mehdi Heydari
and
H. Khademi Zare


In this study, we consider the tardiness and earlinessminimizing inexact
flexible flow line problem with n jobs and m stages and uncertain processing
times, setup times and duedates. For each operation, an uncertainty interval
is given and it is assumed that the processing time of each operation
can take on any value from the corresponding uncertainty interval, regardless
of the values taken by processing times of other operations. For most
of scheduling problems, processing times, setup times and duedates are
treated as certain values, but that is not proper to all actual situations.
Processing times and setup times are not constant because of measurement
errors in the data sets for deciding them and/or human actions in the
manufacturing process. In some cases, a decision maker may prefer using
interval numbers as coefficients of an inexact relationship. As a coefficient
an interval assumes an extent of tolerance or a region that the parameter
can possibly take. A model mixed integer design of the problem is formulated
in inexact environment. On the basis of a comparative study on ordering
interval numbers, inequality constraints involving interval coefficients
are reduced in their satisfactory crisp equivalent forms and a satisfactory
solution of the problem is defined. 




M.B. Fakhrzad
and
Mehdi Heydari


In this study, the triangular membership functions are used for flexible flowlines with m machine centers to examine processingtime uncertainties and to make scheduling more suitable for real applications. A methodology is developed for modeling flexible flow line scheduling with fuzzy processing times, fuzzy due dates, fuzzy setup times, fuzzy holding costs and fuzzy shortage costs. A fuzzy scheduling model is presented and a hybrid algorithm is also designed for its solution. Finally, some numerical examples are developed and solved to demonstrate the computational efficiency of the proposed algorithm. 





