Natashia Boland

Multi-criteria Course Mode Selection and Classroom Assignment Under Sudden Space Scarcity

  • Mehran Navabi-Shirazi
  • Mohamed El Tonbari
  • Natashia Boland
  • Dima Nazzal
  • Lauren Steimle
    • Categories Applications - OR and Management Sciences, Multi-Criteria Optimization, Scheduling Tags , , , ,

    Problem Definition: While physical (or ‘social’) distancing is an important public health intervention during airborne pandemics, physical distancing dramatically reduces the effective capacity of classrooms. During the COVID-19 pandemic, this presented a unique problem to campus planners who hoped to deliver a meaningful amount of in-person instruction in a way that respected physical distancing. This … Read more

    A Fast and Robust Algorithm for Solving Biobjective Mixed Integer Programs

  • Natashia Boland
  • Ian Herszterg
  • Diego Pecin
  • Martin Savelsbergh
  • Tyler Perini
    • Categories Multi-Criteria Optimization Tags , ,

    We present a fast and robust algorithm for solving biobjective mixed integer programs. The algorithm extends and merges ideas from two existing methods: the Boxed Line Method and the epsilon-Tabu Method. We demonstrate its efficacy in an extensive computational study. We also demonstrate that it is capable of producing a high-quality approximation of the nondominated … Read more

    The Dynamic Freight Routing Problem for Less-than-Truckload Carriers

  • Ahmad Baubaid
  • Natashia Boland
  • Martin Savelsbergh
    • Categories Transportation

    Less-than-Truckload (LTL) carriers transport freight shipments from origins to destinations by consolidating freight using a network of terminals. As daily freight quantities are uncertain, carriers dynamically adjust planned freight routes on the day of operations. We introduce the Dynamic Freight Routing Problem (DFRP) and model this problem as a Markov Decision Process (MDP). To overcome … Read more

    Dynamic Discretization Discovery for Solving the Continuous Time Inventory Routing Problem with Out-and-Back Routes

  • Natashia Boland
  • Felipe Lagos
  • Martin Savelsbergh
    • Categories Transportation Tags , ,

    In time dependent models, the objective is to find the optimal times (continuous) at which activities occur and resources are utilized. These models arise whenever a schedule of activities needs to be constructed. A common approach consists of discretizing the planning time and then restricting the decisions to those time points. However, this approach leads … Read more

    Short-Term Inventory-Aware Equipment Management in Service Networks

  • Natashia Boland
  • Alan L. Erera
  • Martin Savelsbergh
  • Yassine Ridouane
    • Categories (Mixed) Integer Linear Programming, Production and Logistics, Transportation

    Logistics companies often operate a heterogeneous fleet of equipment to support their service network operations. This introduces a layer of planning complexity as facilities need to maintain appropriate levels of equipment types to support operations throughout the planning horizon. We formulate an optimization model that minimizes the cost of executing a load plan, assuming knowledge … Read more

    Learning Generalized Strong Branching for Set Covering, Set Packing, and 0-1 Knapsack Problems

  • Yu Yang
  • Natashia Boland
  • Bistra Dilkina
  • Martin Savelsbergh
    • Categories (Mixed) Integer Linear Programming, Integer Programming Tags , ,

    Branching on a set of variables, rather than on a single variable, can give tighter bounds at the child nodes and can result in smaller search trees. However, selecting a good set of variables to branch on is even more challenging than selecting a good single variable to branch on. Generalized strong branching extends the … Read more

    Substitution-based Equipment Balancing in Service Networks with Multiple Equipment Types

  • Natashia Boland
  • Alan L. Erera
  • Martin Savelsbergh
  • Yassine Ridouane
  • Yu Yang
    • Categories Applications - OR and Management Sciences, Transportation

    We investigate substitution-based equipment balancing for a package express carrier operating multiple equipment types in its service network. The weekly schedule of movements used to transport packages through the service network leads to changes in equipment inventory at the facilities in the network. We seek to reduce this change, i.e., the equipment imbalance associated with … Read more

    Multivariable branching: A 0-1 knapsack problem case study

  • Natashia Boland
  • Martin Savelsbergh
  • Yu Yang
    • Categories Applications - OR and Management Sciences Tags ,

    We explore the benefits of multi-variable branching strategies for linear programming based branch and bound algorithms for the 0-1 knapsack problem, i.e., of branching on sets of variables rather than on a single variable (the current default in integer programming solvers). We present examples where multi-variable branching shows advantage over single-variable branching, and partially characterize … Read more

    The Value of Limited Flexibility in Service Network Designs

  • Ahmad Baubaid
  • Natashia Boland
  • Martin Savelsbergh
    • Categories Stochastic Programming, Transportation

    Less-than-truckload carriers rely on the consolidation of freight from multiple shippers to achieve economies of scale. Collected freight is routed through a number of transfer terminals at each of which shipments are grouped together for the next leg of their journeys. We study the service network design problem confronted by these carriers. This problem includes … Read more

    Dynamic Discretization Discovery Algorithms for Time-Dependent Shortest Path Problems

  • Natashia Boland
  • George L. Nemhauser
  • Martin Savelsbergh
  • Edward He
    • Categories Network Optimization, Transportation Tags , , , , ,

    Finding a shortest path in a network is an iconic optimization problem. We focus on settings in which the travel time on an arc in the network depends on the time at which traversal of the arc begins. In such settings, reaching the sink as early as possible is not the only objective of interest. … Read more