A mined integerprogramming model of the problem of schedulingntree type jobs onmmachines is presented. The model is illustrated with a manufacturing application.
A mined integerprogramming model of the problem of schedulingntree type jobs onmmachines is presented. The model is illustrated with a manufacturing application.
We propose a new mixed integer programming based heuristic for computing new benchmark primal solutions for instances of the PESPlib. The PESPlib is a collection of instances for the Periodic Event Scheduling Problem ...
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We propose a new mixed integer programming based heuristic for computing new benchmark primal solutions for instances of the PESPlib. The PESPlib is a collection of instances for the Periodic Event Scheduling Problem (PESP), comprising periodic timetabling problems inspired by real-world railway timetabling settings, and attracting several international research teams during the last years. We describe two strategies to merge a set of good periodic timetables. These make use of the instance structure and minimum weight cycle bases, finally leading to restricted mixed integer programming formulations with tighter variable bounds. Implementing this timetable merging approach in a concurrent solver, we improve the objective values of the best known solutions for the smallest and largest PESPlib instances by 1.7 and 4.3 percent, respectively.
In this paper, the unrelated parallel machine scheduling problem with the objective of minimizing the total tardiness is addressed. For such a problem, a mixed-integer linear programming (MILP) formulation, that consi...
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In this paper, the unrelated parallel machine scheduling problem with the objective of minimizing the total tardiness is addressed. For such a problem, a mixed-integer linear programming (MILP) formulation, that considers assignment and positional variables, is presented. In addition, an iterated local search (ILS) algorithm that produces high-quality solutions in reasonable times is proposed for large size instances. The ILS robustness was determined by comparing its performance with the results provided by the MILP. The instances used in this paper were constructed under a new approach which results in tighter due dates than the previous generation method for this problem. The proposed MILP formulation was able to solve instances of up to 150 jobs and 20 machines. Regarding the ILS, it yielded high-quality solutions in a reasonable time, solving instances of a size up to 400 jobs and 20 machines. Experimental results confirm that both approaches are efficient and promising.(c) 2022 The Author(s). Published by Elsevier Ltd on behalf of Association of European Operational Research Societies (EURO). This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).
This study investigates the progress made in LP and MILP solver performance during the last two decades by comparing the solver software from the beginning of the millennium with the codes available today. On average,...
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This study investigates the progress made in LP and MILP solver performance during the last two decades by comparing the solver software from the beginning of the millennium with the codes available today. On average, we found out that for solving LP/MILP, computer hardware got about 20 times faster, and the algorithms improved by a factor of about nine for LP and around 50 for MILP, which gives a total speed-up of about 180 and 1,000 times, respectively. However, these numbers have a very high variance and they considerably underestimate the progress made on the algorithmic side: many problem instances can nowadays be solved within seconds, which the old codes are not able to solve within any reasonable time.(c) 2022 The Authors. Published by Elsevier Ltd on behalf of Association of European Operational Research Societies (EURO). This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).
One of the main problems that manufacturers are now facing is how to adapt to the market requirements with regard to customization and delivery date. One answer to this problem is to find and utilize flexibility withi...
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One of the main problems that manufacturers are now facing is how to adapt to the market requirements with regard to customization and delivery date. One answer to this problem is to find and utilize flexibility within the work organization. The aim of this work is to find a mathematical representation of these methods and to find the optimal result, or the best possible result in a reasonable time, using an economy based function of evaluation
The "optimal" control of a stationary energy storage system in a DC electric railway network is achieved by minimizing the total energy supplied from all the related traction substations. Given a timetable a...
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The "optimal" control of a stationary energy storage system in a DC electric railway network is achieved by minimizing the total energy supplied from all the related traction substations. Given a timetable and the speed profiles of all the trains in the network, this paper addresses the problem of finding an optimal charging and discharging power control of the storage system. In this paper, we model the problem as a mixed integer programming problem and show the solutions for several parameter values. We then discuss the validity of our model and estimate the advantages of the energy storage system in terms of energy saving. These processes are useful for designing and installing an energy storage system in a DC electric railway network.
In the last decade, emergency department (ED) overcrowding has become a national crisis for the US healthcare system. Increasing mortality rates, decreasing quality of care, financial losses due to walkouts, and ambul...
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In the last decade, emergency department (ED) overcrowding has become a national crisis for the US healthcare system. Increasing mortality rates, decreasing quality of care, financial losses due to walkouts, and ambulance diversion are some of the consequences of ED overcrowding. Given the increasing demand in terms of ambulance utilization, being able to assign service requests to EDs efficiently, becomes a key function of the emergency medical services. This paper presents new ambulance allocation optimization models to reduce patients’ total time to treatment, waiting times; therefore, ED overcrowding. Disparities and fairness are considered in the development of the mixed integer programming models. Under a set of assumptions, we apply our strategies to allocate 75 ambulance emergencies to 11 EDs in a specific county in Florida. Heterogeneous types of patients, demand characteristics, and geographical/facility information are considered in the models. Based on numerical experiments and the situation in Florida, we show that the optimization techniques can be utilized for large problems and result in up to 31% improvement of the current decentralized model. Further analysis reveals the negative or positive impact that the strategies have on each patient, giving new insights for future policy modifications. Bi-objective, single objective, and game theory optimization models are implemented in this study.
Industrial water conservation is an important adaptation to preserve the environment. Eco-Industrial Parks (EIPs) have been designed to encourage the establishment of water exchange networks between enterprises in ord...
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Industrial water conservation is an important adaptation to preserve the environment. Eco-Industrial Parks (EIPs) have been designed to encourage the establishment of water exchange networks between enterprises in order to minimize freshwater consumption and wastewater discharge by maximizing wastewater reuse. In this paper, a mathematical programming model for designing and optimizing industrial water networks in EIPs is studied by formulating and solving Single-Leader-Multi-Follower (SLMF) game problems. Enterprises (followers) aim to minimize their operating costs by reusing wastewater from other enterprises, while the designer (leader) aims to minimize the consumption of natural resources within the ecopark. Moreover, when participating in the ecopark, enterprises can control all their input fluxes and the designer guarantees a minimal relative improvement in comparison with the stand-alone operation of each enterprise. The SLMF game is transformed into a single mixed-integer optimization problem. The obtained results are compared with the results of the blind-input model (Salas et al., 2020).
In multi-element deposits, different blocks are blended together to create a product with a predetermined quality. Generally, blending aims to obtain a special quality and quantity based on determining the processing ...
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In multi-element deposits, different blocks are blended together to create a product with a predetermined quality. Generally, blending aims to obtain a special quality and quantity based on determining the processing plant or customer needs. However, blending causes different products based on the deposit properties. Thus, a block is blended with others to create one of many possible products. The present study aims to develop a mixed integer programming model for the production scheduling of iron ore mines. The model can consider different destinations for mine blocks. Each destination has its own specifications for the main element (Fe) and other existing elements such as sulfur and phosphorous. For this purpose, ten different scenarios were evaluated to investigate the effect of multiple products on production scheduling and Net Present Value (NPV) of the related project. Among the four selected scenarios, the mine was scheduled based on single product while multiple products were considered in scheduling in other scenarios. Based on the results, the maximum NPV in scenarios with multiple products is approximately 15% higher than that of the single product scenarios.
In a stacking system abatement measures with simultaneous effects on climate and water targets, such as wetland construction and cultivation of energy crops, are credited for the abatement of multiple pollutants. In t...
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In a stacking system abatement measures with simultaneous effects on climate and water targets, such as wetland construction and cultivation of energy crops, are credited for the abatement of multiple pollutants. In this study we calculated and compared the abatement costs of achieving multiple environmental targets with and without stacking under different policy regimes (emissions trading, charge, standards). To this end, a static mixed integer programming model was constructed. Theoretical analysis showed that, irrespective of policy regime, the cost of achieving predetermined emission targets is always lower when stacking is allowed. Another result was the excess abatement of pollutant under a no stacking system. Application to the Baltic Sea region showed that cost savings from stacking of pollutant abatement vary between policy regimes, being smallest for price regulation and highest for emission standards. However, the gains from stacking were unevenly distributed among the nine countries surrounding the Baltic Sea under all policy regimes, with Poland making the largest gain and Estonia, Russia and Latvia facing losses. Excess abatement without stacking in relation to the target was highest for nitrogen under all policy regimes, comprising up to 52% of the target abatement.
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