ORBi Open Repository and Bibliography
In may 2007, the ULg's Administrative Board (joined in June 2007 by the FUSAGx) decided to create an institutional repository and defined a strong institutional self-archiving policy to increase the visibility, accessibility and impact of the University's publications (Board's decision).
This decision led to the official launch, in November 2008, of the ORBi platform including both the Academic Bibliography and the Institutional Repository of the Wallonia-Europe University Academy.
Business & economic sciences => Quantitative methods in economics & management
Early detection of university students in potential difficulty : a case study - Hoffait, Anne-Sophie; Schyns, Michael
Rate of success in the first year at University in Belgium is very low regarding other foreign universities. The University of Liege, as other Universities, has already taken different initiatives.
But by early identifying students who have a high probability to face difficulties if nothing is done, the Universities might develop adapted methods to attack the problem with more emphasis where it is more needed and when it is still possible.
Thus we want to develop a decision tool able to identify these students to help them. For that, we consider three standard datamining methods: logistic regression, artificial neural networks and decision...
Revealed preference tests of collectively rational consumption behavior - Crama, Yves
To verify the empirical adequacy of a particular household consumption model, it is important to develop efficient tests that can be applied to real-world data. These tests check whether the observed household behavior is "rational", in the sense that it is consistent with the predictions of the model.
In this talk, we present different approaches based on revealed preferences to test collective models of household consumption. Testing collective rationality is computationally difficult (NP-hard). In order to overcome this negative result, we introduce mixed-integer programming formulations which can be used for medium-sized data sets. Next, we propose simulated annealing heuristics, which allow...
Vers un transport aérien plus écologique et plus économique - Lurkin, Virginie
de l’avion en vol.
Mieux, on peut montrer que la position du centre de gravité (qui dépend du chargement de l’avion) affecte la consommation de carburant. Ce résultat revêt une importance majeure dans un contexte d’augmentation des prix du pétrole et où il s’agit de réduire les émissions polluantes.
Pour un transport aérien plus économique, il s’agit aussi, en cas de livraisons à différents endroits, de réduire au maximum les temps de chargements et de déchargements afin de limiter les coûts liés aux paiements des salariés et à l’utilisation de chaque aéroport intermédiaire.
Au cours de mon exposé, je présente un modèle...
Integrating axle weight restrictions in a two-dimensional vehicle routing problem with sequence based loading - Pollaris, Hanne; Braekers, Kris; Caris, An; Janssens, Gerrit; Limbourg, Sabine
A mixed integer linear programming model for a two-dimensional capacitated vehicle routing problem (2L-CVRP) with sequence based loading and axle weight restrictions is provided. To the authors’ knowledge, it is the first time that axle weight restrictions are incorporated in a VRP. Axle weight limits impose a great challenge for transportation companies. Trucks with overloaded axles represent a significant threat for traffic safety and may cause serious damage to the road surface. Transporters face high fines when violating these limits. The problem is based on a real-world problem from a Belgian logistics service provider. The demand of the customers consists...
Inventory-routing problem with pickups and deliveries of RTI in closed-loop supply chain - Limbourg, Sabine
Reducing environmental impact, related regulations and potential for operational benefits are the main reasons why companies share their Returnable Transport Items (RTIs) among different partners of a closed-loop supply chain. This research deals with an inventory-routing problem with pickups and deliveries of RTIs. A mixed-integer linear program is developed and tested on small instances. To handle realistic large size problems, a clustering algorithm is coupled with a simulation model. This hybrid heuristic allows assessing the benefits of information and RTIs sharing among partners.
A constructive heuristic for the three dimensional Bin Packing Problem with transportation constraints - Paquay, Célia; Schyns, Michael; Limbourg, Sabine
The aim of this work is to propose a Relax-And-Fix heuristic to build a good initial solution to the 3D BPP. First, a mathematical formulation has been developed taking into account several types of constraints such as the stability and fragility of the boxes to pack, their possibility to rotate, the weight distribution inside the bins and their special shapes. Since this model contains a lot of integer variables, we have decided to apply the Relax-and-Fix method. We have selected several sets of variables to be the branching variables and carried out some tests.
Short Prime Quadratizations of Cubic Negative Monomials - Crama, Yves; Rodriguez Heck, Elisabeth
Pseudo-Boolean functions naturally model problems in a number of different areas such as computer science, statistics, economics, operations research or computer vision, among others. Pseudo-Boolean optimization (PBO) is NP-hard, even for quadratic polynomial objective functions. However, much progress has been done in finding exact and heuristic algorithms for the quadratic case. Quadratizations are techniques aimed at reducing a general PBO problem to a quadratic polynomial one. Quadratizing single monomials is particularly interesting because it allows quadratizing any pseudo-Boolean function by termwise quadratization. A characterization of short quadratizations for negative monomials has been provided. In this report we present a proof...