Each contributed talk will be allocated 25 minutes: 20 minutes for presenting and 5 minutes for discussion and questions. Please find all submitted abstracts below.

1.Dries Goossens - Ghent University
Coauthors: David Van Bulck, Jörn Schönberger, Mario Guajardo
RobinX: an XML-driven three-field notation for round-robin sports timetabling
Abstract 5: Over the years, various algorithms have been proposed to construct timetables for sports competitions. These algorithms, however, have rarely been benchmarked due to the lack of a generally accepted data format. We propose an XML-driven three-field notation to classify and describe sports timetabling instances, complemented with a C++-library to read, write, and evaluate these XML files. Furthermore, an interactive website keeps track of these instances and their validated solutions.
2.David Van Bulck - UGent
Coauthors: Dries Goossens
Using a memetic algorithm to handle fairness issues in time-relaxed sports timetabling
Abstract 6: Sports timetables determine who plays against whom, where, and on which time slot. Time-relaxed timetables utilize (many) more time slots than there are games per team, enabling them to consider venue and team availability. To construct fair and organizationally practical time-relaxed timetables, we propose a memetic algorithm that employs a local search operator to reschedule all home games of a team. For numerous instances, this heuristic generates high-quality timetables compared to Gurobi.
3.Xiajie YI - University Gent
Coauthors: Dries Goossens
A stochastic programming approach for scheduling round-robin sport leagues
Abstract 7: This paper aims at designing a schedule for round-robin sport leagues that is stable to uncer- tainty via a two-stage scenario-based stochastic programming approach, considering ranking difference as a quality measure. Scenarios are generated based on the data of 10 major European soccer leagues. Our results show how to position extra, so-called fictive rounds, to accommo- date postponed games
4.Ayse Aslan - University of Groningen
Coauthors: I. Vis, I. Bakir
A Dynamic Thompson Sampling Hyper-Heuristic Framework for Learning Activity Planning in Personalized Learning
Abstract 12: We introduce a weekly flexible learning activity planning problem of own-pace personalized learning models in schools. Our proposed dynamic Thompson sampling based hyper-heuristic framework is benchmarked against 3 other base hyper-heuristics on generated 18 problem instances which comply with characteristics of Dutch secondary schools. Results indicate that our framework performs better than the benchmarked methods mostly due to our tailor-made low-level heuristics in our framework.
5.Jérôme De Boeck - Université libre de Bruxelles
Coauthors: Luce Brotcorne, Fabio D'Andreagiovanni, Bernard Fortz
Strategic bidding in price coupled regions
Abstract 14: We present a price-maker model for strategic bidding in Price Coupled Regions integrating a Unit Commitment formulation. The aim for the bidder is to establish a production planning and set its bids taking into consideration the market's reaction. We are faced to a bilevel optimization problem where the first level is a UC MIP and the second level is linear representing market equilibrium conditions. A reformulation into a single-level program is presented as well as some efficient heuristics.
6.Landelin Delcoucq - University of Mons
Coauthors: Fabian Lecron, Philippe Fortemps
Process Mining : resources and tasks clusteringbased on Cell Formation algorithm
Abstract 15: The Process Mining is the science aiming to distill a structured representation of processes using a set of their real executions. Those processes consist of activities, that can be grouped in tasks, performed by resources. This paper discuss about the extraction of sets of common features resources and tasks based on the use of a hierarchical adaptation of a Cell Formation algorithm.
7.Thomas HACARDIAUX - Université catholique de Louvain
Coauthors: Tancrez Jean-Sébastien
Reducing CO2 emissions using Horizontal Cooperation
Abstract 16: We assess the CO2 emissions reductions that can be reached by horizontal cooperation using a location-inventory model, which minimizes facility opening, transportation, cycle inventory, ordering and safety stock costs. We conduct a large set of numerical experiments, varying several key parameters (vehicles capacity, opening, inventory and ordering costs and demand variability). Finally, we discuss our experimental results and managerial insights.
8.Fränk Plein - Université Libre de Bruxelles
Coauthors: Martine Labbé, Martin Schmidt
Bookings in the European Gas Market: Characterisation of Feasibility and Computational Complexity Results
Abstract 18: Imposing a steady-state potential-based flow model on networks without controllable elements, we give a characterisation of feasible bookings in the European entry-exit gas market. It is used to study the computational complexity of verifying the feasibility of bookings in certain special cases. The difficulty of this problem strongly depends on the network structure and the chosen physics model. We conclude on an overview of known complexity results for different settings.
9.Hossein Moradi - Ghent University
Coauthors: Sara Sasaninejad, Sabine Wittevrongel, Joris Walraevens
Intelligently managing of traffic Flows at Intersections
Abstract 19: Aimed at enhancing the efficiency of intersections to the increasing number of vehicles and by considering the opportunities that wireless communications provide for intelligent intersections, this paper proposes to use an algorithm in telecommunication networks based on the platooning mechanism and according to probability theories to manage current and future intersections intelligently.
10.Hilde Heggen - Hasselt University
Coauthors: Yves Molenbruch, An Caris, Kris Braekers
A large neighborhood search heuristic for the integrated intermodal routing problem
Abstract 20: In this paper, decisions on local drayage in large-volume freight regions with multiple terminals on the one hand and intermodal long-haul routing on the other hand are merged into an integrated intermodal routing problem. This integrated planning approach with capacity restrictions for trucking and rail planning provides decision support for routing customer orders throughout the intermodal network with the aim of minimizing total transport costs.
11.Moritz Yannik Buchem - Maastricht University
Coauthors: Kirsten A.A. Raaimakers, Tjark Vredeveld
The Equitable Travelling Salesman Problem under a Vertex-Based Cost Structure
Abstract 21: We consider the Equitable Travelling Salesman Problem under a vertex-based cost structure. We show that the problem is NP-hard to solve and approximate within any multiplicative factor. We derive a structural property distinguishing it from the general edge cost setting. Based on this structural property we introduce a dynamic program and an additive approximation scheme. Hence, showing that the problem is fixed parameter tractable and can be approximated within an additive bound.
12.Pieter Leyman - KU Leuven Kulak
Coauthors: Patrick De Causmaecker
How can we do worthwhile metaheuristic research?
Abstract 22: We present a metaheuristic development framework, to deal with problems typical of the design of new metaheuristic implementations. We discuss the framework with a component-based view in mind, meaning that we believe added value can be created by doing research on operators instead of some ``novel'' metaheuristic framework. With our framework, we hope to make it easier for researchers to determine where the added value of a specific metaheuristic implementation comes from.
13.Lien Vanbrabant - Hasselt University
Coauthors: Kris Braekers, Katrien Ramaekers
Case managers as a solution for the emergency department crowding problem
Abstract 23: Emergency departments are continuously looking for opportunities to improve their efficiency. The case manager approach entails the use of dedicated physicians and putting a limit on the number of patients simultaneously assigned to a single physician. The potential of applying a case manager approach in an ED is tested by use of a realistic simulation model. By reducing physician multitasking, the case manager approach has potential to improve ED performance.
14.Sarah Vanheusden - Hasselt University, research group logistics
Coauthors: Teun van Gils, Kris Braekers, An Caris, Katrien Ramaekers
Operational workload balancing in a spare parts warehouse
Abstract 24: The objective of this study is to test multiple objective functions (e.g., range, variance, and Gini-coefficient) with the aim of balancing the workload during the day in a spare parts warehouse. Additionally, an iterated local search algorithm is provided to solve the operational workload balancing problem. The performance and practical applicability of the algorithm are shown by analysing and explaining a wide range of warehouse parameters.
15.Bart Vangerven - University of Wuppertal
Coauthors: Dirk Briskorn, Dries R. Goossens, Frits C.R. Spieksma
Contiguous Graph Partitioning: who sits where?
Abstract 25: We research contiguous graph partitioning. Specifically, we address the problem of partitioning the nodes of a graph into contiguous partitions of specific sizes, while maximizing the total number of edges connecting nodes assigned to the same partition.
16.Dirk Briskorn - University of Wuppertal
Coauthors: Konrad Stephan, Nils Boysen
Minimizing makespan on a single machine subject to modular setups
Abstract 26: Single machine scheduling with sequence-dependent setup times is one of the classics of production planning with widespread applications in many industries. Solving this problem under the min-makespan objective is well known to be strongly NP-hard. Nowadays, however, many products have a modular design. This means that product characteristics, (mass-)customizable by customers, are realized by separate components that are loosely coupled and can, thus, facultatively be recombined. We study two pr
17.Stef Lemmens - INSEAD
Coauthors: Andre P. Calmon, Stephen C. Graves
Warranty Matching in a Consumer Electronics Closed-Loop Supply Chain
Abstract 27: We analyze the warranty matching problem that occurs in a real-world closed-loop supply chain. In our setting, there are two warranties in place, i.e. the customer warranty and Original Equipment Manufacturer (OEM) warranty. The matching of these warranties becomes misaligned when there is a warranty claim. To reduce mismatch costs, we evaluate and describe the worst-case performance of three simple to implement matching strategies and we compare them with the currently applied matching policy.
18.Babiche Aerts - Universiteit Antwerpen
Coauthors: Trijntje Cornelissens, Kenneth Sörensen
Solving order batching and picker routing, as a clustered vehicle routing problem
Abstract 30: We approach the integrated order batching and picker routing problem as a clustered vehicle routing problem solved by a two-level Variable Neighborhood Search algorithm. Due to the contextual difference of both environments, we compare different batching criteria and routing heuristics. It appears that warehouse criteria such as the number of aisles, outperform typical proximity criteria for vehicle routing, such as the Hausdorff distance.
19.Lissa Melis - University of Antwerp
Coauthors: Kenneth Sörensen
The on-demand bus routing problem: the importance of bus stop assignment
Abstract 31: In this talk we present the on-demand bus routing problem, which combines the dial-a-ride problem with bus stop assignment, introduced in the school bus routing problem. We propose a straightforward large neighborhood search heuristic to solve the problem. Further, we investigate the impact of bus stop assignment on the solution quality and determine the parameters (number of stations, number of requests, fleet size, etc.) most influencing this impact.
20.Evert Vermeir - KU Leuven
Coauthors: Pieter Vansteenwegen
Local evaluation in bus line planning: A grid based approach
Abstract 32: In line planning, every change to a public transport network can have a large impact on the passenger route choice. Hence, this has to be recalculated every time you want to evaluate an improvement to a line plan. In this paper, we developed a method that only recalculates those parts of the routes that already travel close to a change. This proximity is determined by using a grid structure. The global change in route choice is then evaluated by calculations made in the same cell as the change.
21.Bart SMEULDERS - University of Liege
Testing Random Utility Models: Column Generation
Abstract 33: In this talk, we look at a computationally challenging test for Random Utility Models. This test requires the computation of the Euclidean distance between a point and a complex cone in a high-dimensional space. We propose a column generation approach, discuss key details for an efficient implementation, and give results.
22.Charles Thomas - UCLouvain, Institute of Information and Communication Technologies, Electronics and Applied Mathematics
Coauthors: Quentin Cappart, Pierre Schaus, Louis-Martin Rousseau
A Constraint Programming Approach for Solving Patient Transportation Problems
Abstract 34: The Patient Transportation Problem (PTP) consists in transporting patients to medical appointments. In this paper, we propose a Constraint Programming approach to solve this problem which is flexible enough to accommodate new constraints. Furthermore, we introduce a generic search strategy to maximize efficiently the number of selected requests. Our results show that the model can solve real life instances and outperforms greedy strategies typically used by human schedulers.
23.Ben Hermans - KULeuven
Coauthors: Roel Leus
Expanding search in general graphs: Exact algorithms
Abstract 35: A searcher wants to find a certain object that is hidden at one of the vertices of a connected graph. Each vertex has a given probability to contain the object and an edge's length reflects the distance to move between two vertices. In this talk, we discuss and compare exact algorithms to identify in which sequence the searcher should probe the graph's vertices in order to minimize the expected distance travelled before finding the object.
24.Aurélien CRUCIFIX - N-SIDE
Trend in the industry: more SME’s are turning to Operations Research.
Abstract 36: Several industrial applications of Operations Research (OR) faced by small and medium- sized enterprises (SME’s) will be presented. At N-SIDE, we have observed that more and more SME’s are facing challenges that require OR to be solved efficiently. A few years ago, N-SIDE was contacted mainly by big industrial players. Nowadays, N-SIDE has more and more demands from SME’s. We will further analyse this trend. Keywords: Application, SME, Electric Vehicles, Smart-grid, Planning, Transport
25.Pedro Jesus Copado Mendez - University College London
Coauthors: Lazaros Papageorgiou
Maths2Opt: A Latex-based tool for Mathematical Programming Modelling
Abstract 39: The purpose of this work is enhancing a web-based platform, called Maths2Opt, for translating mathematical programming programs written in Latex to algebraic modelling language or programming language. This tool is aimed at minimising the knowledge of programming, simplifying and speeding up the model implementation and also assisting in the comparison and reproduction of the scientific work.
26.Lienert Cosemans - Hasselt University
Coauthors: Inneke Van Nieuwenhuyse, An Caris
Option contracts in supply chains: a literature review
Abstract 40: During the last decade, there has been a growing interest in option contracts. Option contracts provide more flexibility to the buyer than wholesale contracts, with regard to the quantity of products/amount of capacity that is effectively bought from the supplier. Such flexibility is useful in today's uncertain business environments. This paper summarizes briefly the main characteristics observed in the scientific literature.
27.Anaïs Lemaire - HEC Liège - Management School of the University of Liège
Coauthors: S. Limbourg
How can Food Loss and Waste management achieve the Sustainable Development Goals?
Abstract 41: Food Loss and Waste occur at all stages of the Supply Chain. We reviewed the literature to identify the causes and classify the proposed solutions in order to reach the number 12.3 Sustainable Development Goal: ''2030, halve per capita global food waste at the retail and consumer levels and reduce food losses along production and supply chains, including post-harvest losses''. In our ongoing research, we focus on food waste and related single use packaging waste in the healthcare sector.
28.Célia PAQUAY - University of Liège
Coauthors: Yves Crama, Thierry Pironet
A reactive algorithm for a dial-a-ride problem with real-time disruptions
Abstract 43: The problem considered in this presentation stems from a non-profit organization in charge of transporting patients from their home to medical appointment locations. The aim of this work is to propose a reactive algorithm for this dial-a-ride problem so as to adapt the transportation plans in order to manage real-time disruptions, such as patient delays or appointment cancellations. The plans should be modified quickly, while trying to minimize the changes to avoid confusion for the users.
29.Farzaneh Karami - KU Leuven
Coauthors: Wim Vancroonenburg, Tony Wauters and Greet Vanden Berghe
Conveyor operation modeling and optimization in distribution centers
Abstract 44: This study considers the modeling and optimization of conveyor operations in large distribution centers given the quantity of items that must be transferred between specific loading and unloading conveyor locations. A model is proposed based on the multicommodity quickest path problem which minimizes the makespan while taking into account arc inflow limits.
30.Steven Verwerft - University of Antwerp
Coauthors: Kenneth Sörensen
Analysis of Heuristic Methods
Abstract 45: The computational experiment should be considered the most important tool for gaining insights on the workings of an optimization method, or to prove superiority above yet established methods. This work demonstrates the use of linear mixed effect models, as an alternative to both intuitive approaches such as visualizations, and descriptive statistics; and conventional analysis of variance methods, which often violate the assumption of independence.
31.Reshma Chirayil Chandrasekharan - KU Leuven
Coauthors: Pieter Smet, Tony Wauters
A time-based constructive matheuristic for the shift minimization personnel task scheduling problem
Abstract 46: The shift minimization personnel task scheduling problem concerns assigning tasks to a multi-skilled workforce such that total number of staff utilized is minimized. This work employs a constructive matheuristic. Two different decompositions are tested within the constructive matheuristic and their impact on solution quality is compared. An automatic constructive matheuristic developed based on this study successfully generates optimal solutions for 98% of the benchmark instances.
32.Christian Clavijo Lopez - Université de Liège
Coauthors: Christian Clavijo López, Yves Crama, Thierry Pironet, Frédéric Semet
Multi-period distribution network design under purchase-commitment contracts
Abstract 47: Commercial companies incurring into e-commerce strategies rely on logistics service providers (LSP's) for transportation services. From the perspective of an LSP (forwarder), the study focus on arranging dynamically the most-suitable network of intermediate logistics facilities (belonging to external carriers) with the aim of reducing logistics costs in the long-term. Business agreements between the forwarder and external carriers are settled by a type of capacity reservation contracts.
33.Tomas AMBRA - Vrije Universiteit Brussel
Coauthors: An Caris, Cathy Macharis
Should I stay or should I go? Assessing intermodal and synchromodal resilience from a decentralized perspective
Abstract 48: The paper concerns routing of individual orders and their responsiveness to disruptions. Computational experiments are performed in a case study which concerns imports of retail goods by unimodal truck transport from France to Belgium. Our findings show that dynamic synchromodal solutions cope with disturbances better, but unnecessary deviations and pro-activeness can also lead to negative effects when compared to static intermodal solutions.
34.Yves Molenbruch - Hasselt University
Coauthors: Kris Braekers
Applicability and delay sensitivity of an integrated mobility system
Abstract 49: Innovative demand-driven mobility policies integrate private dial-a-ride services with public transport. The objectives of this work are to (1) determine which demand characteristics and operational conditions are most suitable for enabling a successful integration and (2) quantify the sensitivity of integrated routing solutions with respect to delays on the public transport network.
35.Renaud De Landtsheer - CETIC asbl
Coauthors: Fabian Germeau, Thomas Fayolle, Gustavo Ospina, Renaud De Landtsheer
A Time Window Constraint for Local Search
Abstract 51: This paper introduces a global time windows constraint for the vehicles routing problems in local search optimisation. It relies on pre-computed values and achieves O(1) -time complexity on traditional routing neighbourhoods (1-opt,2-opt,3-opt), and scales to more complex ones. The pre-computations have O(n²) -time complexity, making our approach practical on neighbourhoods with at least O(n²) neighbours to explore (2-opt,3-opt). This contribution is included in the LGPL OscaR.CBLS engine.
36.bart de clerck - Royal Military Academy
Coauthors: Filip Van Utterbeeck, Wim Mees
Social network data collection with automated trend detection for the Belgian elections
Abstract 52: We propose a method for data collection from social media with built-in trend detection to monitor the evolution of the belgian political landscape in times of elections. The collected data from this framework should allow in the long term to identify orchestrated (dis)information campaigns.
37.Christof Defryn - Maastricht University
A selective vehicle routing formulation for the order picking problem
Abstract 53: A new view on the order picking problem is presented in which pick tours are determined using a selective vehicle routing formulation. Only corner nodes of warehouse aisles with a current demand larger than zero are considered in the network. For each of these aisles, at least one corner node should be visited while the coverage of all requested warehouse locations should be ensured. The mathematical formulation can easily be extended to include also order batching decisions.
38.Emmanouil Thanos - KU Leuven
Coauthors: Thomas Van den Bossche, Wim Vancroonenburg, Greet Vanden Berghe
Minimizing container transfer distances in port terminals
Abstract 54: This study proposes a ruin & recreate heuristic for the integrated berth allocation and specific crane assignment problem of vessel arrivals with fixed time windows in a double-quay port terminal. Given the number of containers which must be transferred between vessels and other locations within the terminal's container yard, feasible allocations are evaluated in terms of the total container transfer distance.
39.Oxana Tsidulko - Sobolev Institute of Mathematics
Coauthors: Rene van Bevern
Data reduction for the Location Rural Postman Problem
Abstract 55: The Location Rural Postman Problem (LRPP) is to determine optimal depot locations and vehicle tours in an edge-weighted graph G=(V,E) in order to serve a set R of client edges. We present a polynomial-time approximate kernelization scheme (PSAKS) for the LRPP with respect to the parameter c+b, where c is the number of connected components formed by the edges in R and b is the number vertices incident to an odd number of edges in R.
40.Munise Kubra Sahin - KU Leuven
Coauthors: Ozlem Cavus, Hande Yaman
Multi-stage Stochastic Programming for Demand Response Optimization
Abstract 56: We propose a multi-stage stochastic programming model to schedule different kinds of electrical appliances under uncertain weather conditions and availability of renewable energy with the aim of minimizing the electricity cost and residents' dissatisfaction. We use a scenario groupwise decomposition approach to compute lower and upper bounds for instances with a large number of scenarios. We provide insights about the benefits of optimization and renewable energy combined with batteries.
41.Morteza Davari - KU Leuven
Coauthors: Jeroen Belien, Dries Goossens, Frits Spieksma
Polynomial algorithms for the multi-league sport scheduling problem
Abstract 57: In this work, we consider scheduling multiple leagues, with inter-dependencies arising from teams in different leagues belonging to the same club. This is a common setting for instance in youth competitions, where a club typically has a team for each age category. The teams from the same club share the same venue, which consists of a limited number of terrains. The objective is to minimize the total capacity violations over all clubs during the whole season.
42.Jannik Matuschke - KU Leuven
Coauthors: Antonia Demleitner
Approximation Algorithms for Location Routing with Depot Capacities
Abstract 58: Location Routing is a combination of Facility Location and Vehicle Routing. The goal is to decide on locations of depots and on tours originating from these depots so as to serve a given set of clients at minimum total cost. We devise a bifactor approximation algorithm for the variant of this problem where both vehicles and depots are capacitated. The algorithm computes a solution whose cost is within a constant factor of the optimum while slightly exceeding depot capacities.
43.Yi-Hang Zhu - KU Leuven
Coauthors: Wim Vancroonenburg, Greet Vanden Berghe
Managing nurse workload by planning patient-to-ward assignments
Abstract 59: In hospitals, it is common that some inpatient wards suffer from excessive nurse workload, while other wards find their nurses working far less intensively. This imbalance may arise due to the mismatch between nurses' working time and nursing care demand. This research focuses on balancing nurse workload when assigning patients to wards. The new approach is tested under several scenarios and the results confirm its efficiency.
44.Michiel Van Lancker - KU Leuven
Coauthors: G. Vanden Berghe, T. Wauters
Estimating Objective Values of High-Quality Solutions to a Crane Scheduling Problem
Abstract 60: To compute efficient operations of intermodal terminals, its operations are modeled as a set of disjoint subproblems that are optimized in sequence. However this approach has drawbacks, one of which is that the computed decision strategy can result in inefficient operation of the gantry cranes due to decisions made early in the decision making. We demonstrate a case study of a potential workaround for this issue using regression techniques. First results are presented.
45.Teun van Gils - Hasselt University
Coauthors: A. Caris, K. Ramaekers, K. Braekers
Integrating real-life features while planning order picking operations
Abstract 63: This study illustrates the relevance and importance of incorporating safety constraints, picker blocking, and vertical travel due to high-level storage locations when developing order picking systems (i.e., deciding on zoning, storage, batching, and routing). Results show that ignoring these real-life features causes substantial performance inefficiencies. Robust policies for organizing operations efficiently are provided, even if the system is subject to real-life features.
46.chao li - KU Leuven
Coauthors: Pieter Leyman, Patrick De Causmaecker
The order acceptance and scheduling with capacity constraints
Abstract 65: We consider a new order acceptance and scheduling (OAS) problem arisen in manufacturing. There is a single-machine handling orders with a maximum processing time limit which is called capacity constraints. The objective is to maximize the total profit of accepted and processed orders. Each order is characterized by its release time, processing time,sequence-dependent setup time, due time, and deadline. The impact of capacity constraints and efficient solution methods are investigated.

ORBEL - Conference chair: Prof. A. Caris