Amir Ebrahimzadeh Pilerood; Mehdi Heydari; Mohammad Mahdavi Mazdeh
Abstract
In this paper, the problem of two-machine flow shop scheduling to minimize total energy costs under time-of-use tariffs is investigated. As the objective function of this study is not a regular measure, allowing intentional idle-time can be advantageous. So this study considers two approaches, one for ...
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In this paper, the problem of two-machine flow shop scheduling to minimize total energy costs under time-of-use tariffs is investigated. As the objective function of this study is not a regular measure, allowing intentional idle-time can be advantageous. So this study considers two approaches, one for non-delay version of the problem and the other one for a situation when inserting intentional idle time is permitted. A mixed integer linear programming is formulated to determine the timing of jobs in order to minimize total energy costs while idle time insertion is allowed. For the non-delay version of the problem, a branch-and-bound algorithm is presented. A lower bound and several dominance properties are used to increase the speed of the branch-and-bound algorithm. Computational experiments are also given to evaluate the performance of the algorithm. Based on results, the proposed algorithms can optimally schedule jobs in small size samples but by increasing the number of jobs from 15 and cost periods from 3, the performance of branch-and-bound has been decreased.
Mansoureh Maadi; Mohammad Javidnia
Abstract
Precedence constrained sequencing problem (PCSP) is related to locate the optimal sequence with the shortest traveling time among all feasible sequences. In PCSP, precedence relations determine sequence of traveling between any two nodes. Various methods and algorithms for effectively solving the PCSP ...
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Precedence constrained sequencing problem (PCSP) is related to locate the optimal sequence with the shortest traveling time among all feasible sequences. In PCSP, precedence relations determine sequence of traveling between any two nodes. Various methods and algorithms for effectively solving the PCSP have been suggested. In this paper we propose a cuckoo search algorithm (CSA) for effectively solving PCSP. CSA is inspired by the life of a bird named cuckoo. As basic CSA at first was introduced to solve continuous optimization problem, in this paper to find the optimal sequence of the PCSP, some schemes are proposed with modifications in operators of the basic CSA to solve discrete precedence constrained sequencing problem. To evaluate the performance of proposed algorithm, several instances with different sizes from the literature are tested in this paper. Computational results show the good performance of the proposed algorithm in comparison with the best results of the literature.