Applications – OR and Management Sciences
Beyond Isolated Operating Rooms: Risk-Aware Surgical Episode Scheduling in Single-Entry Networks
Long wait times for elective surgery are a persistent challenge in publicly funded health systems, where hospitals must coordinate limited capacity before, during, and after the operation under considerable uncertainty. We study how a network of collaborating hospitals, such as the University Health Network in the City of Toronto, can centralize intake and jointly schedule … Read more
Optimal Route Planning for Orienteering: Branch-and-Cut with Terrain Cost Surfaces and Fatigue
We address the problem of optimal route planning for competitive orien- teering on real terrain. A Geographic Information System (GIS) pipeline transforms orienteering map data and digital terrain models into a fully asymmetric cost matrix that captures directional slope costs (via the Minetti metabolic model) and cumulative athlete fatigue. The resulting problem, the Asymmetric Orienteering … Read more
Exact Branch-and-Price Algorithm for Live Operating Room Reoptimization
Live reoptimization of operating room schedules is required to cope with disruptions such as emergency arrivals and deviations in surgery durations under strict time limits. The resulting problem can be formulated as a large-scale Resource Constrained Project Scheduling Problem (RCPSP). While exact optimization methods are attractive in this context due to their ability to provide … Read more
Optimal Batching and In-Building Delivery Routing with Capacitated Residential Parcel Lockers
Residential parcel lockers (RPLs), unlike their public counterparts, facilitate secure parcel delivery to occupants of private apartment and condominium buildings in urban areas. In this work, we consider the perspective of a last-mile parcel carrier that has access to an RPL in the lobby of a high-rise residential building. Motivated by growing e-commerce demand, we … Read more
Computing diverse solutions to optimization problems
Classical optimization methods determine a single optimal or near-optimal solution for a decision problem. In many applications, however, the decision maker is interested in evaluating a pool of high-quality solutions, to encode fairness-oriented criteria or to obtain a portfolio of alternatives to use in case of unexpected scenarios. In this paper, we consider the problem … Read more
A Lifting-and-Splitting Framework for Risk-Averse Distributionally Robust Multi-Item Newsvendor Problems
Risk-averse distributionally robust multi-item newsvendor problems provide a fundamental model for inventory decisions under demand uncertainty, limited distributional information, and downside-risk concerns. We study this problem under mean-covariance demand ambiguity, where the decision maker maximizes the worst-case conditional value-at-risk of profit. While cross-item demand correlations are important for portfolio-level inventory decisions, they are difficult to … Read more
A Numerically-safe Branch-Price-and-Cut Algorithm for the Length-Constrained Cycle Partition Problem
The length-constrained cycle partition problem (LCCP) is a graph optimization problem in which a set of nodes must be partitioned into a minimum number of cycles. Every node is associated with a critical time and the length of every cycle must not exceed the critical time of any node in the cycle. We formulate LCCP … Read more
Integrating Power Profile Optimization with Timetabling for Underground Train Networks
We study energy-efficient operation of underground train networks by integrating power profile optimization with timetable design in a single mixed-integer optimization framework. The model minimizes traction energy by synchronizing braking and acceleration across trains sharing a power subnetwork to exploit regenerative energy and flexibly allocating running times to promote coasting. Unlike timetable-only approaches with fixed … Read more
Random-Key Optimization for 2D Irregular Packing with Reusable Area Evaluation
The diverse constraints of industrial applications lead to variants of 2D irregular packing problems that require tailored solution methods. This paper addresses a real-world industrial challenge by proposing a new problem definition, the Maximum Reusable Contiguous Area Problem (MRCAP), and a novel metric, the Maximum Contiguous Area, developed to measure and maximize the contiguous unused … Read more