One of the standard approaches for solving time-dependent discrete optimization problems, such as the traveling salesman problem with time-windows or the shortest path problem with time-windows, is to derive a so-called time-indexed formulation. If the problem has an underlying structure that can be described by a graph, the time-indexed formulation is usually based on a … Read more
We propose a new universal framework for multi-stage decision making under limited information availability. It is developed as part of a larger research project which aims at providing analytical methods to compare and evaluate different models and algorithms for multi-stage decision making. In our setting, we have an open time horizon and limited information about … Read more
We consider a single machine scheduling problem to minimize the completion time variance. This roblem is known to be NP-hard. We prove that if $p_{n-1} = p_{n-2$, then there is an optimal solution of the form $(n,n-2,n-3,…,n-4,n-1)$. A new lower bound are proposed for solving the problem. The test on more than 4000 instances shows … Read more
The field of Statistical Disclosure Control aims at reducing the risk of re-identification of an individual when disseminating data, and it is one of the main concerns of national statistical agencies. Operations Research (OR) techniques were widely used in the past for the protection of tabular data, but not for microdata (i.e., files of individuals … Read more
We consider a general multi-period repositioning problem in vehicle-sharing networks such as bicycle-sharing systems, free-float car-sharing systems, and autonomous mobility-on-demand systems. This problem is subject to uncertainties along multiple dimensions – including demand, travel time, and repositioning duration – and faces several operational constraints such as the service level and cost budget. We propose a … Read more
We study Kusuoka representations of law invariant coherent risk measures on the space of bounded random variables. We refine this representation by giving that any law invariant coherent risk measure can be written as an integral of the Average Value-at-Risk measures on $[0,1]$, which gives a numerically constructive way to approximate any law invariant coherent … Read more
By rerouting and retiming trains in real-time, the propagation of reactionary delay in complex station areas can be reduced. In this study, we propose a new optimisation model and solution algorithm that can be used to determine the best combination of route and schedule changes to make. Whilst several models have been proposed to tackle … Read more
Mathematical optimization problems including a time dimension abound. For example, logistics, process optimization and production planning tasks must often be optimized for a range of time periods. Usually, these problems incorporating time structure are very large and cannot be solved to global optimality by modern solvers within a reasonable period of time. Therefore, the so-called … Read more
We show that deciding the feasibility of a booking (FB) in the European entry-exit gas market is coNP-hard if a nonlinear potential-based flow model is used. The feasibility of a booking can be characterized by polynomially many load flow scenarios with maximum potential-difference, which are computed by solving nonlinear potential-based flow models. We use this … Read more
Price formation is critical to efficient wholesale electricity markets that support reliable operation and efficient investment. The Midcontinent Independent System Operator (MISO) developed the Extended Locational Marginal Pricing (ELMP) with the goal of more completely reflecting resource costs and generally improving price formation to better incent market participation. MISO developed ELMP based on the mathematical … Read more