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

Conference (2014, November 09)

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

Conference (2014, October 19)

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at ... [more ▼]

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at intermediate airports, this problem is simultaneously a weight and balance problem and a sequencing problem. Our objective is to minimize fuel and handling operations costs. This problem is shown to be NP-hard. We resort to a mixed integer linear program. On the basis of a professional partner's real-world data, TNT Airways, we perform numerical experiments using a standard B&C library. This approach yields better solutions than traditional manual planning, which results in substantial cost savings. [less ▲]

Detailed reference viewed: 11 (5 ULg)
See detailA 'price balance statistic' for optimizing pricing strategies: a better estimation of elasticities and cross-elasticities
Lurkin, Virginie ULg; Schyns, Michael ULg; Garrow, Laurie A. et al

Conference (2014, May 16)

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has ... [more ▼]

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has typically been studied separately from the others. Yet, better understanding their relationship gives an airline the opportunity to increase its profitability. In prior work, Tim Jacobs and colleagues introduced a macro-level metric known as the ‘Price Balance Statistic (PBS)’ for evaluating the quality of a given pricing strategy and guiding a search algorithm to identify an optimal alignment between pricing structure, scheduled capacity and RM controls using marginal revenue principles. The aim of our work is to incorporate additional modeling improvements to the PBS. The current model formulation uses price elasticity as input parameters and assumes perfect independency between the different fare classes. However, in reality, a passenger demand fluctuates between classes based on differences in prices. We propose to use instrumented variable linear regression methods to obtain parameter estimates for price elasticities and cross-elasticities. This modification incorporates accurate price elasticities but also the impact of a change in one fare class on another through the cross-elasticities. [less ▲]

Detailed reference viewed: 28 (11 ULg)
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See detailA 'price balance statistic' for optimizing pricing strategies: a better estimation of elasticities and cross-elasticities
Lurkin, Virginie ULg; Schyns, Michael ULg; Garrow, Laurie A. et al

Conference (2014, May 15)

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has ... [more ▼]

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has typically been studied separately from the others. Yet, better understanding their relationship gives an airline the opportunity to increase its profitability. In prior work, Tim Jacobs and colleagues introduced a macro-level metric known as the ‘Price Balance Statistic (PBS)’ for evaluating the quality of a given pricing strategy and guiding a search algorithm to identify an optimal alignment between pricing structure, scheduled capacity and RM controls using marginal revenue principles. The aim of our work is to incorporate additional modeling improvements to the PBS. The current model formulation uses price elasticity as input parameters and assumes perfect independency between the different fare classes. However, in reality, a passenger demand fluctuates between classes based on differences in prices. We propose to use instrumented variable linear regression methods to obtain parameter estimates for price elasticities and cross-elasticities. This modification incorporates accurate price elasticities but also the impact of a change in one fare class on another through the cross-elasticities. [less ▲]

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See detailAn Ant Colony System for Responsive Dynamic Vehicle Routing
Schyns, Michael ULg

E-print/Working paper (2014)

We present an algorithm based on an Ant Colony System to deal with a broad range of Dynamic Capacitated Vehicle Routing Problems with Time Windows, (partial) Split Delivery and Heterogeneous fleets ... [more ▼]

We present an algorithm based on an Ant Colony System to deal with a broad range of Dynamic Capacitated Vehicle Routing Problems with Time Windows, (partial) Split Delivery and Heterogeneous fleets (DVRPTWSD). Besides the traditional distance criterion, we address the important case of responsiveness. Responsiveness is defined here as completing a delivery as soon as possible, within the time window, such that the client or the truck may restart its activities. This is crucial for many production or service activities in different fields: express parcel deliveries, taxi services, Just in Time production, express repair services, medical care, petrol station replenishment, etc. We develop an interactive web-based solution to allow dispatchers to take new information into account in real-time. The algorithm and its parametrization were tested on real and artificial instances. We first illustrate our approach with a problem submitted by Liege Airport, the 8th biggest cargo airport in Europe. The goal is to develop a decision system to optimize the journey of the refueling trucks. We then consider some classical VRP benchmarks with extensions for more complex problems. [less ▲]

Detailed reference viewed: 33 (13 ULg)
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 ▲]

Detailed reference viewed: 14 (2 ULg)
Peer Reviewed
See detailA Mixed Integer Programming formulation for the three dimensional bin packing problem deriving from an air cargo application
Paquay, Célia ULg; Schyns, Michael ULg; Limbourg, Sabine ULg

in International Transactions in Operational Research (2014)

The present paper looks into the problem of optimising the loading of boxes into containers. The goal is to minimise the unused volume. This type of problem belongs to the family of Multiple Bin Size Bin ... [more ▼]

The present paper looks into the problem of optimising the loading of boxes into containers. The goal is to minimise the unused volume. This type of problem belongs to the family of Multiple Bin Size Bin Packing Problems. The approach includes an extensive set of constraints encountered in real-world applications in the three-dimensional case: the stability, the fragility of the items, the weight distribution and the possibility to rotate the boxes. It also includes the specific situation in which containers are truncated parallelepipeds. This is typical in the field of air transportation. While most papers on cutting and packing problems describe ad-hoc procedures, this paper proposes a mixed integer linear program. The validity of this model is tested on small instances. [less ▲]

Detailed reference viewed: 53 (19 ULg)
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See detailThe Airline Container Loading Problem with Pickup and Delivery
Lurkin, Virginie ULg; Schyns, Michael ULg

E-print/Working paper (2013)

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at ... [more ▼]

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at intermediate airports, this problem is simultaneously a weight and balance problem and a sequencing problem. Our objective is to minimize fuel and handling operations costs. This problem is shown to be NP-hard. We resort to a mixed integer linear program. On the basis of a professional partner's real-world data, TNT Airways, we perform numerical experiments using a standard B&C library. This approach yields better solutions than traditional manual planning, which results in substantial cost savings. [less ▲]

Detailed reference viewed: 60 (23 ULg)
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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 ▲]

Detailed reference viewed: 92 (36 ULg)
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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 ▲]

Detailed reference viewed: 95 (15 ULg)
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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 ▲]

Detailed reference viewed: 72 (24 ULg)
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 ▲]

Detailed reference viewed: 84 (19 ULg)
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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 ▲]

Detailed reference viewed: 164 (10 ULg)