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We consider an open shop scheduling problem. At first, a bi-objective possibilistic mixed-integer programming formulation is developed. The inherent uncertainty in processing times and due dates as fuzzy parameters, machine-dependent setup times and removal times are the special features of this model. The considered bi-objectives are to minimize the weighted mean tardiness and weighted mean completion times. After converting the original formulation into a single-objective crisp one by using an interactive approach and obtaining the Pareto-optimal solutions for small-sized instances, an efficient multi-objective particle swarm optimization (MOPSO) is proposed in order to achieve a good approximate Pareto-optimal set for medium and large-sized examples. This algorithm exploits new selection regimes of the literature for the global best and personal best. Furthermore, a modified decoding scheme is designed to reduce the search area in the solution space, and a local search algorithm is proposed to generate initial particle positions. Finally, the efficiency of the proposed MOPSO (PMOPSO) is shown by comparing with the common MOPSO (CMOPSO) by the use of the design of experiments (DOE) based on three comparison metrics.

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 We present a new mathematical model for a permutation flowshop scheduling problem with sequence-dependent setup times considering minimization of two objectives, namely makespan and weighted mean total earliness/tardiness. Only small-sized problems with up to 20 jobs can be solved by the proposed integer programming approach. Thus, an effective multi-objective immune system (MOIS) is specially proposed to solve the given problem. Finally, the computational results are reported showing that the proposed MOIS is effective in finding solutions of large-sized problems. 

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  We relax some assumptions of the traditional scheduling problem and suggest an adapted meta-heuristic algorithm to optimize efficient utilization of resources and quick response to demands simultaneously. We intend to bridge the existing gap between theory and real industrial scheduling assumptions (e.g., hot metal rolling industry, chemical and pharmaceutical industries). We adapt and evaluate a well-known algorithm based on electromagnetic science. The motivation behind our proposed meta-heuristic approach has arisen from the attraction-repulsion mechanism of electromagnetic theories in physics. In this basic idea, we desire to bring our search closer to a region with a superior objective function while going away from the region with the inferior objective function in order to move the solution gradually towards optimality. The algorithm is carefully evaluated for its performance against two existing algorithms using multi-objective performance measures and statistical tools. The results show that our proposed solution method outperforms the others.

  

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  We consider criticality in project networks having imprecise activity duration times. It is well known that finding all possibly critical paths of an imprecise project network is an NP-hard problem. Here, based on a method for finding critical paths of crisp networks by using only the forward recursion of critical path method, for the first time an algorithm is proposed which can find all possibly critical paths of interval-valued project networks. The proposed algorithm considers interactivity among paths which has not been yet considered in the fuzzy project scheduling literature. The extension of the proposed algorithm to the fuzzy network calculates criticality degrees of activities and paths of projects without any need to enumerate all project paths. Although algorithms for calculating criticality degrees in fuzzy networks have been previously proposed, despite the fact that they mostly consider a specific type of fuzzy numbers as activity duration times, the exiting algorithms do not discriminate possibly critical paths before calculating the criticality degrees. The computational experience on a series of well-known project samples confirms the algorithm to be remarkably more efficient than similar algorithms for fuzzy networks.

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Air defense is a crucial area for all naval combat systems. In this study, we consider a warship equipped with an air-defense weapon that targets incoming threats using surface-to-air missiles. We define the weapon scheduling problem as the optimal scheduling of a set of surface-to-air missiles of a warship to a set of attacking air threats. The optimal scheduling of the weapon results in an increase in the probability of successful targeting of all incoming threats. We develop a heuristic method to obtain a very fast and acceptable solution for the problem. In addition, a branch and bound algorithm is developed to find the optimal solution. In order to increase the efficiency of this algorithm, a lower bound, an upper bound and a set of dominance rules have been developed. Using randomly generated test problems, the performance of the proposed solution approaches is analyzed. The results indicate that in all practical situations, the branch-and-bound algorithm is able to solve the problem optimally in less than a second.

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We present a bi-objective model for a green truck scheduling and routing problem at a cross-docking system. This model determines three key decisions at the cross dock: (1) defining a sequence and schedule of inbound trucks at the receiving door, (2) specifying a sequence and a schedule of outbound trucks at the shipping door, and (3) determining the routes of the outbound truck while serving customers. The first objective function is related to responsiveness of the network that minimizes time window violations and the second objective function minimizes total fuel consumption of trucks in order to consider the environmental factor of the network. Also, a learning effect is considered in loading and unloading process times. To solve the bi-objective model, an archived multi-objective simulated annealing (AMOSA) is used and modified. Finally, a number of test problems are solved and the efficiency of the proposed AMOSA is compared with the e-constraint method.

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In this paper bus scheduling problem under the constraints that the total number of buses needed to perform all trips is known in advance and the energy level of buses is limited, is considered. Each depot has a different time processing cost. The goal of this problem is to find a minimum cost feasible schedule for buses. A mathematical formulation of the problem is developed. When there are two depots, a polynomial time algorithm is developed for the problem and theoretical results about the complexity and correctness of the algorithm is presented. Also, several examples are introduced for illustrating validity of the algorithm.

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Batch scheduling is among the important problems in industrial engineering and has been widely attendant in practical applications. Clustering is the set of observation assignment into some subsets so that the observations in the same cluster are similar in some sense and the similarity of generated clusters is very low. Clustering is considered as one of the approaches in unsupervised learning and a common technique for statistical data analysis which has been applied in many fields, including machine learning, data mining and etc. This paper studies a case study in Iran Puya company (as a home appliance maker company in Iran). In the production line of refrigerator of the current company, a cutting machine is identified as a bottleneck that can process several iron plates simultaneously. In this regard a good scheduling on this cutting machine improves the effectiveness of production line in terms of cost and time. The objective is to minimize the total tardiness and maximizing the job values when the deteriorated jobs are delivered to each customer in various size batches. Based on these assumptions a mathematical model is proposed and two hybrid algorithms based on simulation annealing and clustering methods are offered for solving it and the results are compared with the global optimum values generated by Lingo 10 software. Based on the effective factors of the problem, a number of sensitivity analyses are also implemented including number of jobs and rate of deterioration. Accordingly, the running time grows exponentially when the number of jobs increases. However the rate of deterioration could not affect the running time. Computational study demonstrates that using clustering methods leads an specified improvements in total costs of company between 15 to 41 percent.

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Here, we first associate a graph to a university course timetabling problem (UCTP) and use the components of this graph and some customary and organizational rules to transform the original large scale problem into some smaller problems. Then, we apply the branch and cut method to obtain the optimal solution of each smaller problem. Our presented approach enables us to apply exact methods to obtain high quality solutions for large scale UCTPs. Finally, we examine the numerical efficiency of the resulting algorithm.