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The periodic supply vessel planning problem (PSVPP) consists in determining a periodic schedule and the respective fleet composition for servicing offshore units on a regular basis. One of the challenges for the PSVPP is determining reliable schedules with a good compromise between reliability and cost. This work extends the PSVPP by including stochastic demand and travel time. We also introduce a novel methodology based on a voyage‐based model to deal with the schedule robustness. Basically, key statistical parameters related to the routes' demand and execution time are generated. They are used together with a set of probability combinations to incorporate the schedule reliability into the optimization model. Therefore, schedule reliability is an input parameter in the optimization model. The instances used in the study are based on real data from Brazil. A comparison of the new methodology to conventional approaches is presented, and a Monte Carlo simulation is used to evaluate the quality of the solutions. The proposed methodology is able to generate robust schedules at a lower cost compared to the conventional approaches. The proposed methodology might be applied to other stochastic problems, where schedule reliability is a key parameter for the problem. [ABSTRACT FROM AUTHOR]

This research effort is dedicated to develop and test a mathematical approach to estimate the optimal aircraft age to make decisions about its withdrawn from service, market relocation, or starting its retirement and decommissioning processes. Our method consists of a cost-benefit financial analysis based on the expected revenue from the aircraft returning to operations and the aircraft recovery process to support end-of-life decisions. The core contribution of this research is the possibility of systematically analyse opportunities to return parked aircraft to active service, considering reasonable scenarios of operating revenue improvements or operating cost reductions, postponing the aircraft retirement and decommissioning decision. It is important to highlight that only financial concerns of the end-of-life aircraft problem were analysed. Considering this managerial context, the estimation of the aircraft parking and retirement costs, the recovery of the operating revenues from its market relocation and the recovered values from its disassembly and dismantling may influence these companies' aircraft fleet planning in a well-supported manner. This research intends to fulfill the gaps in the literature regarding commercial aircraft costs and revenues incurred during its end-of-life phase, aiming to estimate how much they affect its total cost of ownership, considering aircraft owners' and operators' decision-making contexts. [ABSTRACT FROM AUTHOR]

Mining is an important economic activity and a highly complex industry. As such, it demands a complex supply chain to connect mines to clients, often involving railways, ports and long-distance maritime shipping. State-of-the-art optimization tools are an invaluable asset to help manage such a complex environment, which makes mining industry a very fertile ground for operational research applications. This paper aims to present a bibliographical review of published works involving operational research applications in the mining industry. We start by mapping applications within each isolated link of the chain. Then, we make inroads into the researches involving and connecting multiple links of the mining chain. Finally, we present summaries of our finding and pinpoint some directions for research opportunities in the mining industry. [ABSTRACT FROM AUTHOR]

The classical nonlinear mixed integer formulation of the transmission network expansion problem cannot guarantee finding the optimal solution due to its nonconvex nature. We propose an alternative mixed integer linear disjunctive formulation, which has better conditioning properties than the standard disjunctive model. The mixed integer program is solved by a commercial Branch and Bound code, where an upper bound provided by a heuristic solution is used to reduce the tree search. The heuristic solution is obtained using a GRASP metaheuristic, capable of finding sub-optimal solutions with an affordable computing effort. Combining the upper bound given by the heuristic and the mixed integer disjunctive model, optimality can be proven for several hard problem instances. Index Terms--Combinatorial, heuristics, optimization, transmission planning.