Progressive hedging applied as a metaheuristic to schedule production in open-pit mines accounting for reserve uncertainty

AbstractScheduling production in open-pit mines is characterized by uncertainty about the metal content of the orebody (the reserve) and leads to a complex large-scale mixed-integer stochastic optimization problem. In this paper, a two-phase solution approach based on Rockafellar and Wets’ progressive hedging algorithm (PH) is proposed. PH is used in phase I where the problem is first decomposed by partitioning the set of scenarios modeling metal uncertainty into groups, and then the sub-problems associated with each group are solved iteratively to drive their solutions to a common solution. In phase II, a strategy exploiting information obtained during the PH iterations and the structure of the problem under study is used to reduce the size of the original problem, and the resulting smaller problem is solved using a sliding time window heuristic based on a fix-and-optimize scheme. Numerical results show that this approach is efficient in finding near-optimal solutions and that it outperforms existing heuristics for the problem under study

Méthodes et outils pour une affectation optimale des juges lors des compétitions : une application au concours John Molson

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Assigning judges to competitions of several rounds using Tabu search

a b s t r a c t The judge assignment problem consists in finding an assignment satisfying the competition rules (hard constraints) and meeting, as much as possible, the competition organizers objectives (soft constraints). In this paper, various specific real-world constraints found in organizing academic competitions are handled. We tackle the corresponding problem with a metaheuristic approach based on Tabu search. The numerical results indicate that very good solutions can be generated in reasonable computational times

Circular Economy in Winter Road Maintenance: A Simulation Study

This study analyzes the sustainability of the circular economy model on winter road maintenance. Winter road maintenance involves plowing snow, spreading abrasives, and then sweeping and collecting the remaining abrasives at the end of the winter season. Traditionally, in the linear approach, the collected sweepings are landfilled, which incurs landfilling costs for resources that could be reused. To address this issue, we consider the option of recycling sweepings for use in the following winter seasons. We develop a discrete-event simulation model that estimates the economic and environmental benefits of this option. Using data from a case study of a highway in Quebec, Canada, the model shows that introducing circular economy practices in winter road maintenance results in less material going to landfills, lower costs, less use of aggregates from virgin materials, and lower CO2 emissions compared to the linear approach. A subsequent sensitivity analysis reveals that the quantity of sweepings collected greatly influences the outcomes

Circular Economy in Winter Road Maintenance: A Simulation Study

This study analyzes the sustainability of the circular economy model on winter road maintenance. Winter road maintenance involves plowing snow, spreading abrasives, and then sweeping and collecting the remaining abrasives at the end of the winter season. Traditionally, in the linear approach, the collected sweepings are landfilled, which incurs landfilling costs for resources that could be reused. To address this issue, we consider the option of recycling sweepings for use in the following winter seasons. We develop a discrete-event simulation model that estimates the economic and environmental benefits of this option. Using data from a case study of a highway in Quebec, Canada, the model shows that introducing circular economy practices in winter road maintenance results in less material going to landfills, lower costs, less use of aggregates from virgin materials, and lower CO2 emissions compared to the linear approach. A subsequent sensitivity analysis reveals that the quantity of sweepings collected greatly influences the outcomes

Entretien avec Elisabeth Leuvrey

International audienc

Toward a Simulation Model for Capacity Analysis of a New Port Terminal

Part 11: Regular Session: Simulation and Optimization of Systems PerformancesInternational audienceWith the current growth of the maritime industry, which is a key element for many supply chains worldwide, ports seek to increase their capacity and performance in order to tackle challenges and opportunities created by the increased demand in the industry. Port expansion is an efficient way to meet this objective, but requires important resources and careful planning. Before undertaking such a major project, it is important for a port to have a firm grasp and understanding of its current capacity as well as the expansion’s requirements and limitations in light of its traffic forecasts. This article presents the data analysis realized as part of an expansion project of a Canadian port case. The data analysis is executed in order to feed the first simulation model of its kind in this sector that will jointly consider the logistics operations taking place in the current port and its new terminal. This article addresses the first steps of the model’s conception through data analysis as well as solutions to problems encountered. As the study is underway, the preliminary results of the work are presented