This paper addresses a new version of the biomedical sample transportation problem, as a vehicle ... more This paper addresses a new version of the biomedical sample transportation problem, as a vehicle routing problem with precedence constraints arising in the context of healthcare logistics, and proposes an iterated local search algorithm to solve it. This new version is more realistic and complex since it considers the collection centers' opening hours and the moment at which they are visited as decision variables, granting additional flexibility to elaborate more efficient routes. Indeed, this problem is harder to model and to solve than its previous version because the constraint on the short samples' lifetime leads to interdependency between successive pickups at each collection center. A metaheuristic is thus proposed to solve real-life instances. Numerical experiments confirm (1) the value of simultaneously planning routes, opening hours, and visits' hours (which is new in the literature) and (2) the efficiency of the proposed algorithm to solve this problem.
Order picking is one of the most challenging operations in distribution center management and one... more Order picking is one of the most challenging operations in distribution center management and one of the most important sources of costs. One way to reduce the lead time and associated costs is to minimize the total amount of work for collecting all orders. This paper is motivated by a collaboration with an industrial partner who delivers furniture and electronic equipment. We have modeled their narrow aisles order picking problem as a vehicle routing problem through a series of distance transformations between all pairs of locations. Security issues arising when working on narrow aisles impose an extra layer of difficulty when determining the routes. We show that these security measures and the operator equipment allow us to decompose the problem per aisle. In other words, if one has to pick orders from three aisles in the warehouse, it is possible to decompose the problem and create three different instances of the picking problem. Our approach yields an exact representation of all possible picking sequences. We also show that neglecting 2D aspects and solving the problem over a 1D warehouse yields significant difference in the solutions, which are then suboptimal for the real 2D case. We have solved a large set of instances reproducing realistic configurations using a combination of heuristics and an exact algorithm, minimizing the total
Transportation Research Part E: Logistics and Transportation Review, 2018
Less than truckload is an important type of road-based transportation. Based on real data and on ... more Less than truckload is an important type of road-based transportation. Based on real data and on a collaboration with industry, we show that a collaborative approach between companies offers important benefits. We propose to develop partnerships between shipping companies and to synchronize their shipments. Four operational collaborative schemes with different objectives are developed. The first one focuses on minimizing shipping costs for shippers. The second and third ones minimize the carrier's costs and the environmental cost, respectively. The fourth one is a combination of all three. The results of our computational experiments demonstrate that collaboration lead to significant cost reductions.
Cet article relate et analyse l'implantation de progiciels de gestion intégrée des ressources au ... more Cet article relate et analyse l'implantation de progiciels de gestion intégrée des ressources au sein de cinq entreprises manufacturières québécoises de grande envergure. Par le biais d'entrevues en profondeur, les motivations logistiques ayant mené à l'implantation du système sont décrites. Les diverses phases d'implantation qui ont été suivies par chaque entreprise sont analysées en détail et les impacts de cette implantation sur le climat organisationnel sont soulevés. Les résultats démontrent que la ligne est parfois mince entre le succès ou l'échec d'une implantation et que les plans de communication et de formation auprès des employés jouent un rôle déterminant. Seules les entreprises ayant apporté un soin minutieux à chacune des étapes de l'implantation peuvent se vanter d'avoir effectué une implantation réussie.
International Journal of Production Research, 2016
Warehouse order picking activities are among the ones that impact the most the bottom lines of wa... more Warehouse order picking activities are among the ones that impact the most the bottom lines of warehouses. They are known to often account for more than half of the total warehousing costs. New practices and innovations generate new challenges for managers and open new research avenues. Many practical constraints arising in real-life have often been neglected in the scientific literature. We introduce, model, and solve a rich order picking problem under weight, fragility, and category constraints, motivated by our observation of a real-life application arising in the grocery retail industry. This difficult warehousing problem combines complex picking and routing decisions under the objective of minimizing the distance traveled. We first provide a full description of the warehouse design which enables us to algebraically compute the distances between all pairs of products. We then propose two distinct mathematical models to formulate the problem. We develop five heuristic methods, including extensions of the classical largest gap, mid point, S-shape, and combined heuristics. The fifth one is an implementation of the powerful adaptive large neighborhood search algorithm specifically designed for the problem at hand. We then implement a branch-and-cut algorithm and cutting planes to solve the two formulations. The performance of the proposed solution methods is assessed on a newly generated and realistic test bed containing up to 100 pickups and seven aisles. We compare the bounds provided by the two formulations. Our in-depth analysis shows which formulation tends to perform better. Extensive computational experiments confirm the efficiency of the ALNS matheuristic and derive some important insights for managing order picking in this kind of warehouses.
INFOR: Information Systems and Operational Research, 2006
Cet article étudie le problème du choix de sites d'entrepôts pour les autobus en transport urbain... more Cet article étudie le problème du choix de sites d'entrepôts pour les autobus en transport urbain. L'objectif visé est de minimiser la durée de récupération de l'investissement. Une analyse financière permet d'évaluer la profitabilité de différents scénarios d'ouverture d'entrepôts. Deux modèles de programmation linéaire sont proposés afin de minimiser le kilométrage à vide parcouru par les autobus pour un ensemble d'entrepôts donné. Les modèles ont été utilisés dans le cadre d'une étude pour le Réseau de Transport de la Capitale de la ville de Québec. Les résultats obtenus permettent d'identifier les localisations les plus intéressantes et démontrent que des réductions importantes du kilométrage à vide peuvent être réalisées si le RTC implante un nouvel entrepôt. Les économies découlant de la réduction du kilométrage à vide permettent de rentabiliser l'investissement relié à l'ouverture du nouvel entrepôt en 6 années. Finalement, l'impact de cet entrepôt additionnel sur la congestion des routes d'accès est également analysé.
Proceedings of 2013 International Conference on Industrial Engineering and Systems Management, Oct 1, 2013
The emergency logistics field is a new and particular challenge for logistics' managers. In t... more The emergency logistics field is a new and particular challenge for logistics' managers. In these networks, the satisfaction of the affected people's demand is much more important than the cost minimization. Moreover, crisis managers are looking for networks that ensure an equitable distribution of resources over affected people. We propose a new mathematical formulation that reflects this interest. First, we define a multi-period formulation for the network design problem, where the opening decisions are reconsidered at every period. In addition, this model includes different features of the realistic challenges of emergency logistics, like the possible shortage in capacity and the backorder of demand. Finally, three different formulations of a “fair” distribution problem are proposed. These formulations are tested on random generated instances and the analysis of the distribution plans obtained with each formulation is presented at the end of this paper.
International Journal of Production Research, 2015
ABSTRACT Biomedical sample management plays a central role in an efficient health care system and... more ABSTRACT Biomedical sample management plays a central role in an efficient health care system and requires important resources. Based on our collaboration with the Quebec’s Ministère de la Santé et des Services sociaux (Ministry of Health and Social Services), this article describes the challenging context of biomedical sample transportation in the Canadian province of Quebec. It is modelled on a variant of the multi-trip vehicle routing problem with time windows where routes need to be planned from a laboratory to satisfy the multiple pick-up requests of each sample collection centre under some practical constraints. We propose and evaluate two alternative mathematical formulations, as well as fast heuristics, to minimise total transportation distances. The performance of the proposed methods is assessed over a large case study based on the network of laboratories in the province of Quebec.
This paper addresses a vehicle routing problem in disaster area. The objective is to distribute h... more This paper addresses a vehicle routing problem in disaster area. The objective is to distribute humanitarian aid to affected zones from a set of opened humanitarian aid distribution centres using different types of vehicles. Given the particular context of emergency, distribution is planned to satisfy the demand of each affected zone for each type of humanitarian aid in the shortest possible time (this time includes both travelling and vehicles loading and unloading times). An exact and a heuristic solution method are presented, evaluated and compared through a large set of generated instances. We also investigate the impact of split delivery on delivery times.
This paper proposes a Decision Support System (DSS) for designing a distribution network for huma... more This paper proposes a Decision Support System (DSS) for designing a distribution network for humanitarian relief in disasters. Based on our observations and discussions with experts in crisis management, we identify and model the decision-making steps for designing this type of network. We identify the objectives and constraints for each of these decision steps, and then we propose the mathematical formulations appropriate for each step and implement them in a DSS prototype embedded with a 3step algorithm. Finally, we report the results of many numerical experiments that illustrate how the prototype should be used by crisis managers. These results allow us to assess the prototype's relevance to decision support in disasters.
Les résultats d'une étude comparative montrent que des économies substantielles peuvent être réal... more Les résultats d'une étude comparative montrent que des économies substantielles peuvent être réalisées en utilisant la quatrième heuristique, ce qui nous amène à remettre en question le bien-fondé de la politique habituelle limitant à une seule le nombre des stations à visiter au cours d'un même voyage.
L'étude traite du système logistique de l'approvisionnement des stations-service avec à l'appui d... more L'étude traite du système logistique de l'approvisionnement des stations-service avec à l'appui des données réelles de l'industrie de la distribution de produits pétroliers. À partir de ces données, quatre approches heuristiques sont élaborées et les résultats tendent à démontrer un accroissement de la qualité des plans d'approvisionnement.
This paper considers a generalized version of the trip packing problem that we encountered as a s... more This paper considers a generalized version of the trip packing problem that we encountered as a sub-problem of the petrol stations replenishment problem. In this version we have to assign a number of trips to a fleet composed of a limited number of non-identical tank-trucks. Each trip has a specific duration, working time of vehicles is limited and the net revenue of each trip depends on the truck used. The paper provides a mathematical formulation of the problem and proposes some construction, improvement and neighbourhood search solution heuristics. A set of benchmark problem instances is created in a way that reflects real-life situations and used to analyse the performance of the proposed heuristics. A reallife case is also used to further assess the proposed heuristics.
International Journal of Production Research, 2013
Automated Storage and Retrieval System (AS/RS) performance highly depends on the characteristics ... more Automated Storage and Retrieval System (AS/RS) performance highly depends on the characteristics of the mechanical equipment. However, once the system has been physically implemented, achieving its maximum efficiency depends on the way the system is operated. This paper it shows that request sequencing (i.e., planning the order in which storage and retrieval requests are performed) is of paramount importance in AS/RS performance. This paper reviews and adapts the most popular storage and sequencing policies to dynamic contexts, and then it proposes a "sequencing mathematical model" (SMM) to simultaneously solve the sequencing and storage location problems. Extensive computational results based on a thorough simulation experiment plan confirm that performing the requests in the right sequence can have a positive impact on AS/RS performance. Our results show that the proposed sequencing mathematical model regularly outperforms other methods. When used in a dynamic context, the proposed SMM may yield up to a 25% reduction in average travel-time compared to the situation where a no-sequencing method is applied.
This paper presents a new sweep based heuristic for the fleet size and mix vehicle routing proble... more This paper presents a new sweep based heuristic for the fleet size and mix vehicle routing problem. This problem involves two kinds of decisions: the selection of a mix of vehicles among the available vehicle types and the routing of the selected fleet. The proposed algorithm first generates a large number of routes which are serviced by one or two vehicles. The selection of routes and vehicles to be used is then made by solving to optimality, in polynomial time, a set-partitioning problem having a special structure. Results on a set of benchmark test problems show that the proposed heuristic produces excellent solutions in short computing times. Having a fast but good solution method is needed for transportation companies that rent a significant part of their fleet and consequently can take advantage of frequent changes in fleet composition. Finally, the proposed heuristic produced the best-known solution for some of the test problems. These new best-known solutions are reported.
This paper addresses a new version of the biomedical sample transportation problem, as a vehicle ... more This paper addresses a new version of the biomedical sample transportation problem, as a vehicle routing problem with precedence constraints arising in the context of healthcare logistics, and proposes an iterated local search algorithm to solve it. This new version is more realistic and complex since it considers the collection centers' opening hours and the moment at which they are visited as decision variables, granting additional flexibility to elaborate more efficient routes. Indeed, this problem is harder to model and to solve than its previous version because the constraint on the short samples' lifetime leads to interdependency between successive pickups at each collection center. A metaheuristic is thus proposed to solve real-life instances. Numerical experiments confirm (1) the value of simultaneously planning routes, opening hours, and visits' hours (which is new in the literature) and (2) the efficiency of the proposed algorithm to solve this problem.
Order picking is one of the most challenging operations in distribution center management and one... more Order picking is one of the most challenging operations in distribution center management and one of the most important sources of costs. One way to reduce the lead time and associated costs is to minimize the total amount of work for collecting all orders. This paper is motivated by a collaboration with an industrial partner who delivers furniture and electronic equipment. We have modeled their narrow aisles order picking problem as a vehicle routing problem through a series of distance transformations between all pairs of locations. Security issues arising when working on narrow aisles impose an extra layer of difficulty when determining the routes. We show that these security measures and the operator equipment allow us to decompose the problem per aisle. In other words, if one has to pick orders from three aisles in the warehouse, it is possible to decompose the problem and create three different instances of the picking problem. Our approach yields an exact representation of all possible picking sequences. We also show that neglecting 2D aspects and solving the problem over a 1D warehouse yields significant difference in the solutions, which are then suboptimal for the real 2D case. We have solved a large set of instances reproducing realistic configurations using a combination of heuristics and an exact algorithm, minimizing the total
Transportation Research Part E: Logistics and Transportation Review, 2018
Less than truckload is an important type of road-based transportation. Based on real data and on ... more Less than truckload is an important type of road-based transportation. Based on real data and on a collaboration with industry, we show that a collaborative approach between companies offers important benefits. We propose to develop partnerships between shipping companies and to synchronize their shipments. Four operational collaborative schemes with different objectives are developed. The first one focuses on minimizing shipping costs for shippers. The second and third ones minimize the carrier's costs and the environmental cost, respectively. The fourth one is a combination of all three. The results of our computational experiments demonstrate that collaboration lead to significant cost reductions.
Cet article relate et analyse l'implantation de progiciels de gestion intégrée des ressources au ... more Cet article relate et analyse l'implantation de progiciels de gestion intégrée des ressources au sein de cinq entreprises manufacturières québécoises de grande envergure. Par le biais d'entrevues en profondeur, les motivations logistiques ayant mené à l'implantation du système sont décrites. Les diverses phases d'implantation qui ont été suivies par chaque entreprise sont analysées en détail et les impacts de cette implantation sur le climat organisationnel sont soulevés. Les résultats démontrent que la ligne est parfois mince entre le succès ou l'échec d'une implantation et que les plans de communication et de formation auprès des employés jouent un rôle déterminant. Seules les entreprises ayant apporté un soin minutieux à chacune des étapes de l'implantation peuvent se vanter d'avoir effectué une implantation réussie.
International Journal of Production Research, 2016
Warehouse order picking activities are among the ones that impact the most the bottom lines of wa... more Warehouse order picking activities are among the ones that impact the most the bottom lines of warehouses. They are known to often account for more than half of the total warehousing costs. New practices and innovations generate new challenges for managers and open new research avenues. Many practical constraints arising in real-life have often been neglected in the scientific literature. We introduce, model, and solve a rich order picking problem under weight, fragility, and category constraints, motivated by our observation of a real-life application arising in the grocery retail industry. This difficult warehousing problem combines complex picking and routing decisions under the objective of minimizing the distance traveled. We first provide a full description of the warehouse design which enables us to algebraically compute the distances between all pairs of products. We then propose two distinct mathematical models to formulate the problem. We develop five heuristic methods, including extensions of the classical largest gap, mid point, S-shape, and combined heuristics. The fifth one is an implementation of the powerful adaptive large neighborhood search algorithm specifically designed for the problem at hand. We then implement a branch-and-cut algorithm and cutting planes to solve the two formulations. The performance of the proposed solution methods is assessed on a newly generated and realistic test bed containing up to 100 pickups and seven aisles. We compare the bounds provided by the two formulations. Our in-depth analysis shows which formulation tends to perform better. Extensive computational experiments confirm the efficiency of the ALNS matheuristic and derive some important insights for managing order picking in this kind of warehouses.
INFOR: Information Systems and Operational Research, 2006
Cet article étudie le problème du choix de sites d'entrepôts pour les autobus en transport urbain... more Cet article étudie le problème du choix de sites d'entrepôts pour les autobus en transport urbain. L'objectif visé est de minimiser la durée de récupération de l'investissement. Une analyse financière permet d'évaluer la profitabilité de différents scénarios d'ouverture d'entrepôts. Deux modèles de programmation linéaire sont proposés afin de minimiser le kilométrage à vide parcouru par les autobus pour un ensemble d'entrepôts donné. Les modèles ont été utilisés dans le cadre d'une étude pour le Réseau de Transport de la Capitale de la ville de Québec. Les résultats obtenus permettent d'identifier les localisations les plus intéressantes et démontrent que des réductions importantes du kilométrage à vide peuvent être réalisées si le RTC implante un nouvel entrepôt. Les économies découlant de la réduction du kilométrage à vide permettent de rentabiliser l'investissement relié à l'ouverture du nouvel entrepôt en 6 années. Finalement, l'impact de cet entrepôt additionnel sur la congestion des routes d'accès est également analysé.
Proceedings of 2013 International Conference on Industrial Engineering and Systems Management, Oct 1, 2013
The emergency logistics field is a new and particular challenge for logistics' managers. In t... more The emergency logistics field is a new and particular challenge for logistics' managers. In these networks, the satisfaction of the affected people's demand is much more important than the cost minimization. Moreover, crisis managers are looking for networks that ensure an equitable distribution of resources over affected people. We propose a new mathematical formulation that reflects this interest. First, we define a multi-period formulation for the network design problem, where the opening decisions are reconsidered at every period. In addition, this model includes different features of the realistic challenges of emergency logistics, like the possible shortage in capacity and the backorder of demand. Finally, three different formulations of a “fair” distribution problem are proposed. These formulations are tested on random generated instances and the analysis of the distribution plans obtained with each formulation is presented at the end of this paper.
International Journal of Production Research, 2015
ABSTRACT Biomedical sample management plays a central role in an efficient health care system and... more ABSTRACT Biomedical sample management plays a central role in an efficient health care system and requires important resources. Based on our collaboration with the Quebec’s Ministère de la Santé et des Services sociaux (Ministry of Health and Social Services), this article describes the challenging context of biomedical sample transportation in the Canadian province of Quebec. It is modelled on a variant of the multi-trip vehicle routing problem with time windows where routes need to be planned from a laboratory to satisfy the multiple pick-up requests of each sample collection centre under some practical constraints. We propose and evaluate two alternative mathematical formulations, as well as fast heuristics, to minimise total transportation distances. The performance of the proposed methods is assessed over a large case study based on the network of laboratories in the province of Quebec.
This paper addresses a vehicle routing problem in disaster area. The objective is to distribute h... more This paper addresses a vehicle routing problem in disaster area. The objective is to distribute humanitarian aid to affected zones from a set of opened humanitarian aid distribution centres using different types of vehicles. Given the particular context of emergency, distribution is planned to satisfy the demand of each affected zone for each type of humanitarian aid in the shortest possible time (this time includes both travelling and vehicles loading and unloading times). An exact and a heuristic solution method are presented, evaluated and compared through a large set of generated instances. We also investigate the impact of split delivery on delivery times.
This paper proposes a Decision Support System (DSS) for designing a distribution network for huma... more This paper proposes a Decision Support System (DSS) for designing a distribution network for humanitarian relief in disasters. Based on our observations and discussions with experts in crisis management, we identify and model the decision-making steps for designing this type of network. We identify the objectives and constraints for each of these decision steps, and then we propose the mathematical formulations appropriate for each step and implement them in a DSS prototype embedded with a 3step algorithm. Finally, we report the results of many numerical experiments that illustrate how the prototype should be used by crisis managers. These results allow us to assess the prototype's relevance to decision support in disasters.
Les résultats d'une étude comparative montrent que des économies substantielles peuvent être réal... more Les résultats d'une étude comparative montrent que des économies substantielles peuvent être réalisées en utilisant la quatrième heuristique, ce qui nous amène à remettre en question le bien-fondé de la politique habituelle limitant à une seule le nombre des stations à visiter au cours d'un même voyage.
L'étude traite du système logistique de l'approvisionnement des stations-service avec à l'appui d... more L'étude traite du système logistique de l'approvisionnement des stations-service avec à l'appui des données réelles de l'industrie de la distribution de produits pétroliers. À partir de ces données, quatre approches heuristiques sont élaborées et les résultats tendent à démontrer un accroissement de la qualité des plans d'approvisionnement.
This paper considers a generalized version of the trip packing problem that we encountered as a s... more This paper considers a generalized version of the trip packing problem that we encountered as a sub-problem of the petrol stations replenishment problem. In this version we have to assign a number of trips to a fleet composed of a limited number of non-identical tank-trucks. Each trip has a specific duration, working time of vehicles is limited and the net revenue of each trip depends on the truck used. The paper provides a mathematical formulation of the problem and proposes some construction, improvement and neighbourhood search solution heuristics. A set of benchmark problem instances is created in a way that reflects real-life situations and used to analyse the performance of the proposed heuristics. A reallife case is also used to further assess the proposed heuristics.
International Journal of Production Research, 2013
Automated Storage and Retrieval System (AS/RS) performance highly depends on the characteristics ... more Automated Storage and Retrieval System (AS/RS) performance highly depends on the characteristics of the mechanical equipment. However, once the system has been physically implemented, achieving its maximum efficiency depends on the way the system is operated. This paper it shows that request sequencing (i.e., planning the order in which storage and retrieval requests are performed) is of paramount importance in AS/RS performance. This paper reviews and adapts the most popular storage and sequencing policies to dynamic contexts, and then it proposes a "sequencing mathematical model" (SMM) to simultaneously solve the sequencing and storage location problems. Extensive computational results based on a thorough simulation experiment plan confirm that performing the requests in the right sequence can have a positive impact on AS/RS performance. Our results show that the proposed sequencing mathematical model regularly outperforms other methods. When used in a dynamic context, the proposed SMM may yield up to a 25% reduction in average travel-time compared to the situation where a no-sequencing method is applied.
This paper presents a new sweep based heuristic for the fleet size and mix vehicle routing proble... more This paper presents a new sweep based heuristic for the fleet size and mix vehicle routing problem. This problem involves two kinds of decisions: the selection of a mix of vehicles among the available vehicle types and the routing of the selected fleet. The proposed algorithm first generates a large number of routes which are serviced by one or two vehicles. The selection of routes and vehicles to be used is then made by solving to optimality, in polynomial time, a set-partitioning problem having a special structure. Results on a set of benchmark test problems show that the proposed heuristic produces excellent solutions in short computing times. Having a fast but good solution method is needed for transportation companies that rent a significant part of their fleet and consequently can take advantage of frequent changes in fleet composition. Finally, the proposed heuristic produced the best-known solution for some of the test problems. These new best-known solutions are reported.
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Papers by Jacques Renaud