Month: September 2024

An optimization framework to provide volunteers with task selection autonomy and group opportunities

  • Milan Preet Kaur
  • Jennifer Pazour
    • Categories Applications - OR and Management Sciences Tags , , , , , , , ,

    Abstract Nonprofit Organizations (NPOs) rely on volunteers to support community needs but struggle with making strategic volunteer-to-task assignments to enable volunteer satisfaction, and completion of complex tasks. Creation of volunteer groups and their assignment to NPO tasks can help achieve these goals by providing volunteers with opportunity for networking, collaboration, and peer learning. However, strategically … Read more

    Simple and Effective: A Deterministic Auction with Support Information

  • Rishikesh Parma
  • Çağıl Koçyiğit
    • Categories Applications - OR and Management Sciences, Finance and Economics, Yield Management Tags , , ,

    We study an auction design problem where a seller aims to sell a single item to multiple bidders with independent private values. The seller knows only an upper bound on these values and does not know their distribution. The objective is to devise a deterministic auction mechanism effective across a broad set of distributions. We … Read more

    Integrated Optimization of Timetabling and Electric Vehicle Scheduling: A Case Study of Aachen, Germany

  • Vladimir Stadnichuk
  • Jenny Segschneider
  • Arie M.C.A. Koster
  • Grit Walther
    • Categories Applications - OR and Management Sciences, Approximation Algorithms, Transportation Tags , , , ,

    We tackle the integrated planning problem of periodic timetabling and electric vehicle scheduling, crucial for cities transitioning to electric bus fleets. Given existing timetables, we allow only minor modifications and propose an iterative solution approach that addresses the Electric Vehicle Scheduling Problem (EVSP) in each iteration. Due to the NP-hard nature of EVSP, we employ … Read more

    A graphical framework for global optimization of mixed-integer nonlinear programs

  • Danial Davarnia
    • Categories (Mixed) Integer Nonlinear Programming, Global Optimization Applications, Global Optimization Theory Tags , , , , ,

    While mixed-integer linear programming and convex programming solvers have advanced significantly over the past several decades, solution technologies for general mixed-integer nonlinear programs (MINLPs) have yet to reach the same level of maturity. Various problem structures across different application domains remain challenging to model and solve using modern global solvers, primarily due to the lack … Read more

    How Many Policies Do We Need in K-Adaptability for Two-stage Robust Integer Optimization?

  • Jannis Kurtz
    • Categories Robust Optimization Tags ,

    In the realm of robust optimization the k-adaptability approach is one promising method to derive approximate solutions for two-stage robust optimization problems. Instead of allowing all possible second-stage decisions, the k-adaptability approach aims at calculating a limited set of k such decisions already in the first-stage before the uncertainty reveals. The parameter k can be … Read more

    Robust Appointment Scheduling for General Convex Uncertainty Sets

  • Judith Brugman
  • Dick den Hertog
  • Johan Van Leeuwaarden
    • Categories Robust Optimization, Scheduling Tags , , , , ,

    The Appointment Scheduling Problem (ASP) involves scheduling a finite number of customers with uncertain service times, served consecutively by a single server, aiming to minimize the weighted costs of waiting time, idle time, and overtime. Previous studies using stochastic programming were limited to small instances. We introduce a Robust Optimization (RO) approach that considers service … Read more

    Energy-efficient Timetables for Railway Traffic: Incorporating DC Power Models

  • Tobias Kuen
  • Robert Burlacu
  • Patrick Gemander
  • Jorge Weston
    • Categories (Mixed) Integer Nonlinear Programming, Cutting Plane Approaches, Transportation Tags , , ,

    Efficient operation of underground railway systems is critical not only for maintaining punctual service but also for minimizing energy consumption, a key factor in reducing operational costs and environmental impact. To evaluate the energy consumption of the timetables, this paper delves into the development of mathematical models to accurately represent energy dynamics within the underground … Read more

    Advances in Polyhedral Relaxations of the Quadratic Linear Ordering Problem

  • Sven Mallach
    • Categories Combinatorial Optimization, Integer Programming

    We report on results concerning the polyhedral structure of the quadratic linear ordering problem and its associated integer linear programming formulations. Specifically, we provide a deeper analysis of the characteristic equation system that partly describes the corresponding polytope, i.e., the convex hull of the feasible solutions to the quadratic linear ordering problem, and determine an … Read more

    Facets from solitary items for the 0/1 knapsack polytope

  • Shreyas Bhowmik
  • Sachin Jayaswal
    • Categories 0-1 Programming Tags , , , ,

    We introduce a new class of valid inequalities for any 0/1 knapsack polytope, called Solitary item inequality, which are facet-defining. We prove that any facet-defining inequality of a 0/1 knapsack polytope with nonnegative integral coefficients and right hand side 1 belongs to this class, and hence, the set of facet-defining inequalities corresponding to strong covers … Read more

    Hybrid iterated local search algorithm for the vehicle routing problem with lockers

  • Bruno Oliveira
  • Artur Alves Pessoa
  • Marcos Roboredo
    • Categories Combinatorial Optimization, Integer Programming, Meta Heuristics Tags , , ,

    In the Vehicle Routing Problem (VRP) with Lockers, the vertices in a graph are divided into two key subsets: a customer set and a locker set, with lockers serving as alternative delivery points for the customer’s parcel. This paper presents a generic VRP with lockers, where a customer’s parcel can be delivered either to its … Read more