References of "Schyns, Michael"
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See detailEarly detection of university students in potential difficulty
Hoffait, Anne-Sophie ULg; Schyns, Michael ULg

Conference (2014, January)

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 ... [more ▼]

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 trees and focus on early detection, i.e. before starting at the University. Then, we suggest to adapt these three methods as well as the classification framework in order to increase the probability of correct identification of the students. In our approach, we do not restrict the classification to two extreme classes, e.g. failure or success, but we create subcategories for different levels of confidence: high risk of failure, risk of failure, expected success or high probability of success. The algorithms are modified accordingly and to give more weight to the class that really matters. Note that this approach remains valid for any other classification problems for which the focus is on some extreme classes; e.g. fraud detection, credit default... We check if the factors of success/failure we can identify are similar to those reported in the literature. We also make a ``what-if sensitivity analysis''. The goal is to measure in more depth the impact of some factors and the impact of some solutions, e.g., a complementary training or a reorientation. [less ▲]

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See detailA constructive heuristic for the three dimensional Bin Packing Problem with transportation constraints
Paquay, Célia ULg; Schyns, Michael ULg; Limbourg, Sabine ULg

Conference (2014)

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 ... [more ▼]

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. [less ▲]

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See detailThe Airline Container Loading Problem with Pickup & Delivery and Multi Doors
Schyns, Michael ULg; Lurkin, Virginie ULg

in 53rd AGIFORS Annual Proceedings 2013: Annual Symposium and Study Group Meeting (2013, August)

We address the problem of allocating containers into predefined positions of a carrier, in this case aircraft, under several realistic structural and safety constraints, including the management of ... [more ▼]

We address the problem of allocating containers into predefined positions of a carrier, in this case aircraft, under several realistic structural and safety constraints, including the management of several doors. The originality of our approach is to allow multi-trips with pickup and delivery at some intermediate locations. The objective is to minimize the economic and environmental costs including the impact of the intermediate operations. We resort to an integer linear model. Numerical experiments have been performed using a standard B&C library. The cost impact is measured. The Airline Group of the International Federation of Operational Research Societies, composed of professionals and academics, has awarded us the price of the "Best technical presentation" for this work. [less ▲]

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See detailThe Airline Container Loading Problem with Pickup and Delivery
Lurkin, Virginie ULg; Schyns, Michael ULg

Conference (2013, July 02)

We address the problem of allocating containers into predefined positions of a carrier, in this case aircraft, under several realistic structural and safety constraints. The originality of our approach is ... [more ▼]

We address the problem of allocating containers into predefined positions of a carrier, in this case aircraft, under several realistic structural and safety constraints. The originality of our approach is to allow multi-trips with pickup and delivery at some intermediate locations. The objective is to minimize the economic and environmental costs including the impact of the intermediate operations. We resort to an integer linear model. Numerical experiments have been performed using a standard B\&C library. Heuristics are developed to speed up the process. [less ▲]

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See detailA branch and price approach for an airport vehicle routing problem
Schyns, Michael ULg

Conference (2013, July)

This project has been initiated by a main European freight airport. The goal is to optimize the aircraft refueling process which relies on a given set of trucks. The underlying process can be defined as a ... [more ▼]

This project has been initiated by a main European freight airport. The goal is to optimize the aircraft refueling process which relies on a given set of trucks. The underlying process can be defined as a vehicle routing problem with capacity and time windows. We resort to a branch and price approach for which we first analyze the impact of different parameters on the performance of the algorithm. Due to the stochastic nature of the demand and time windows in this context, we are also working on a priori (split delivery) and a posteriori (efficient re-optimization) measures. [less ▲]

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See detailAutomatic Aircraft Cargo Load Planning with Pick-up and Delivery
Lurkin, Virginie ULg; Schyns, Michael ULg

Conference (2013, March 15)

This research aims to develop a new mixed integer linear program to solve the containers assignment problem when pickup and deliveries are considered. Given a pool of ULDs and an aircraft with multiple ... [more ▼]

This research aims to develop a new mixed integer linear program to solve the containers assignment problem when pickup and deliveries are considered. Given a pool of ULDs and an aircraft with multiple destinations, we want to obtain a loading plan determining at which positions the ULDs must be assigned in order to minimize simultaneous the quantity of fuel consumed and the number of re-handles. The loading plan should also ensure a number of structural, safety and manoeuvrability constraints. The model has been tested on real instances and provides encouraging results. [less ▲]

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See detailAutomatic Aircraft Cargo Load Planning with Pick-up and Delivery
Lurkin, Virginie ULg; Schyns, Michael ULg

Conference (2013, February 07)

This research aims to develop a new mixed integer linear program to solve the containers assignment problem when pickup and deliveries are considered. Given a pool of ULDs and an aircraft with multiple ... [more ▼]

This research aims to develop a new mixed integer linear program to solve the containers assignment problem when pickup and deliveries are considered. Given a pool of ULDs and an aircraft with multiple destinations, we want to obtain a loading plan determining at which positions the ULDs must be assigned in order to minimize simultaneous the quantity of fuel consumed and the number of re-handles. The loading plan should also ensure a number of structural, safety and manoeuvrability constraints. The model has been tested on real instances and provides encouraging results. [less ▲]

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See detailAutomatic Cargo Load Planning: Special shipments
Kleyntssens, Thomas ULg; Limbourg, Sabine ULg; Schyns, Michael ULg

in ILS 2012 Proceedings (2012, August 28)

The aircraft loading problem is a real-world combinatorial optimisation problem highly constrained. Indeed, loading the aircraft so the gross weight is less than the maximum allowable is not enough. This ... [more ▼]

The aircraft loading problem is a real-world combinatorial optimisation problem highly constrained. Indeed, loading the aircraft so the gross weight is less than the maximum allowable is not enough. This weight must be distributed to keep the centre of gravity within specified limits. Moreover, an aircraft has usually several cargo compartments with specific contours and structural limitations such as floor loading, combined load limits and cumulative load limitations. Finally, some shipments are particularly restrictive to transport, like dangerous goods, live animals and perishable goods. This paper is concerned with the incorporation of these latter constraints in a mixed integer linear program for the problem of loading a set of Unit Loading Devices and bulk into an aircraft. Experimental results show that our method achieves optimal solutions within only few seconds. [less ▲]

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See detailThree dimensional Bin Packing Problem applied to air cargo
Paquay, Célia ULg; Schyns, Michael ULg; Limbourg, Sabine ULg

in ILS 2012 Proceedings (2012, August 26)

Deciding whether a set of three dimensional boxes can be packed into a container is a NP-hard problem. Mathematical models have been developed, however, only few studies take into account constraints ... [more ▼]

Deciding whether a set of three dimensional boxes can be packed into a container is a NP-hard problem. Mathematical models have been developed, however, only few studies take into account constraints encountered in real-world applications such as the stability or the fragility of the cargo. Moreover, despite the importance of this issue in air transport, the literature is almost silent on constraints related to the distribution of the weight inside a container. This paper is concerned with the formulation of the three dimensional palletization which includes the main constraints met in the air cargo industry. [less ▲]

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See detailOptimisation 3D du chargement de conteneurs pour le transport aérien
Paquay, Célia ULg; Limbourg, Sabine ULg; Schyns, Michael ULg

in LigéRO (Ed.) Proceedings ROADEF 2013 (2012, April 11)

De nos jours, décider comment remplir des conteneurs avec des colis est une activité courante aussi bien dans le domaine du transport routier qu’aérien. Ce type de question est apparentée aux problèmes de ... [more ▼]

De nos jours, décider comment remplir des conteneurs avec des colis est une activité courante aussi bien dans le domaine du transport routier qu’aérien. Ce type de question est apparentée aux problèmes de Bin-Packing(BPP) en recherche opérationnelle. En termes économiques, ces opérations doivent mener à une solution qui satisfait de nombreuses contraintes physiques, être réalisées rapidement et de sorte à maximiser certains critères. Typiquement, on tentera de charger un maximum de colis dans un minimum de conteneurs pour réduire les coûts. [less ▲]

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See detailChargement de marchandises dans un avion cargo: le cas des marchandises nécessitant des précautions particulières
Schyns, Michael ULg; Limbourg, Sabine ULg; Kleyntssens, Thomas ULg

Conference (2012, April)

D'une part, les entreprises de transport aérien ont acheminé en 2010 plus d’un tiers de la valeur des exportations mondiales. D'autre part, le chargement des avions est une opération complexe soumise à de ... [more ▼]

D'une part, les entreprises de transport aérien ont acheminé en 2010 plus d’un tiers de la valeur des exportations mondiales. D'autre part, le chargement des avions est une opération complexe soumise à de nombreuses contraintes et peu d'outils sont disponibles pour aider les loadmasters à trouver la meilleure disposition des conteneurs dans les avions. Limbourg, Schyns et Laporte (2011) ont proposé un modèle à variables entières pour traiter les problèmes élémentaires. Notre travail est une extension de ces travaux. Nous considérons des chargements spéciaux qui impliquent des précautions particulières (produits dangereux, animaux, produits réfrigérés, aliments périssables, ...) ainsi que le transport de marchandises de plus grande taille. L’ajout de ces deux types de contraintes se justifie par la grande fréquence de ces situations dans des problèmes réels rencontrés par nos partenaires industriels. Le problème résultant est très complexe et nous proposons un outil pour le résoudre. [less ▲]

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See detailThree dimensional Bin Packing Problem applied to air transport
Paquay, Célia ULg; Schyns, Michael ULg; Limbourg, Sabine ULg

Conference (2012, February 02)

Packing boxes into containers is a daily process in many di erent elds and especially in transport. However, the particular case of air transport brings some new constraints such as the stability or the ... [more ▼]

Packing boxes into containers is a daily process in many di erent elds and especially in transport. However, the particular case of air transport brings some new constraints such as the stability or the fragility of the cargo. The distribution of the weight has also to be considered. Moreover, this special case also brings some data such as the dimensions of the possible containers, called Unit Load Devices. This paper is concerned with the formulation of the three dimensional palletization which includes the main constraints met in the air cargo industry. It proposes a integer linear program for this combinatorial optimization problem. [less ▲]

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See detailAn Integer Programming model for air transport of hazardous and special shipments
Kleyntssens, Thomas ULg; Limbourg, Sabine ULg; Schyns, Michael ULg

Conference (2012, February 02)

The aircraft loading problem is a real-world combinatorial optimisation problem highly constrained. This weight must be distributed to keep the centre of gravity within speci ed limits. Moreover, an ... [more ▼]

The aircraft loading problem is a real-world combinatorial optimisation problem highly constrained. This weight must be distributed to keep the centre of gravity within speci ed limits. Moreover, an aircraft has usually several cargo compart- ments with speci c contours and structural limitations such as oor loading, com- bined load limits and cumulative load limitations. Finally, some shipments are par- ticularly restrictive to transport, like dangerous goods, live animals and perishable goods. This paper is concerned with the incorporation of these latter constraints in a mixed integer linear program for the problem of loading a set of Unit Load- ing Devices and bulk into an aircraft. Experimental results show that our method achieves optimal solutions within only few seconds. [less ▲]

Detailed reference viewed: 101 (32 ULg)
See detailHow to optimally load a set of containers into an aircraft
Schyns, Michael ULg; Limbourg, Sabine ULg; Laporte, Gilbert

E-print/Working paper (2012)

Detailed reference viewed: 65 (11 ULg)
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See detailAutomatic Aircraft Load Planning
Limbourg, Sabine ULg; Schyns, Michael ULg; Laporte, Gilbert

in Journal of the Operational Research Society (2012), 63

The goal of this paper is the development of a new mixed integer linear program designed for optimally loading a set of containers and pallets into a compartmentalised cargo aircraft. It is based on real ... [more ▼]

The goal of this paper is the development of a new mixed integer linear program designed for optimally loading a set of containers and pallets into a compartmentalised cargo aircraft. It is based on real-world problems submitted by a professional partner. This model takes into account strict technical and safety constraints. In addition to the standard goal of optimally positioning the centre of gravity, we also propose a new approach based on the moment of inertia. This double goal implies an increase in aircraft efficiency and a decrease in fuel consumption. Cargo loading generally remains a manual, or at best a computer assisted, and time consuming task. A fully automatic software was developed to quickly compute optimal solutions. Experimental results show that our approach achieves better solutions than manual planning, within only a few seconds. [less ▲]

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See detailChargement d’un avion cargo : le cas des marchandises nécessitant des précautions particulières
Kleyntssens, Thomas ULg; Limbourg, Sabine ULg; Schyns, Michael ULg

Conference (2011, December 15)

Le problème du chargement de marchandises dans un avion cargo est soumis à des contraintes strictes de sécurité. C’est un problème d’optimisation combinatoire d’une importance cruciale pour les compagnies ... [more ▼]

Le problème du chargement de marchandises dans un avion cargo est soumis à des contraintes strictes de sécurité. C’est un problème d’optimisation combinatoire d’une importance cruciale pour les compagnies aériennes. En effet, un mauvais chargement diminue l’efficacité d’un avion et impose des tensions importantes sur sa structure qui peuvent entraîner la destruction d’équipements de haute valeur, voire la perte de vies. De plus, certains colis spéciaux ont des contraintes très restrictives. C’est le cas notamment des produits dangereux, des animaux, des marchandises alimentaires et périssables. En plus des incompatibilités entre certains produits, il faut tenir compte des interactions possibles sur des équipements de l’avion. Par exemple, des produits émettant des émissions magnétiques doivent être placés de manière à ne pas avoir des effets néfastes avec les instruments de navigation. Dans cet article, nous proposons d’incorporer ces contraintes liées aux colis nécessitant des précautions particulières dans un programme d’optimisation linéaire mixte du problème de chargement d’un ensemble de Unit Loading Devices et de vrac dans un avion. Les résultats obtenus à partir de données réelles montrent que notre méthode permet d’obtenir des solutions optimales en seulement quelques secondes. [less ▲]

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See detailThree Dimensional Bin Packing Problem applied to air cargo
Paquay, Célia ULg; Schyns, Michael ULg; Limbourg, Sabine ULg

Scientific conference (2011, December 15)

Deciding whether a set of three dimensional boxes can be packed into a container is a NP-hard problem. Mathematical models have been developed, however, only few studies take into account constraints ... [more ▼]

Deciding whether a set of three dimensional boxes can be packed into a container is a NP-hard problem. Mathematical models have been developed, however, only few studies take into account constraints encountered in real-world applications such as the stability or the fragility of the cargo. Moreover, despite the importance of this issue in air transport, the literature is almost silent on constraints related to the distribution of the weight inside a container. This paper is concerned with the formulation of the three dimensional palletization which includes the main constraints met in the air cargo industry. [less ▲]

Detailed reference viewed: 142 (13 ULg)
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See detailLes défis du transport de fret
Limbourg, Sabine ULg; Schyns, Michael ULg

Article for general public (2011)

Detailed reference viewed: 104 (16 ULg)