A general lot-sizing problem in a closed-loop supply chain with returns

Conference (2013, February 08)

We consider a stochastic version of the multi-product multi-level capacitated lotsizing and scheduling problem with sequence-dependent setups. A bottler needs to determine its production schedule over a ... [more ▼]

We consider a stochastic version of the multi-product multi-level capacitated lotsizing and scheduling problem with sequence-dependent setups. A bottler needs to determine its production schedule over a finite horizon in order to satisfy a deterministic demand. The raw materials are supplied through two different sources: uncapacitated reserves of new bottles and the uncertain returns of used bottles. We present results for the single-item case. [less ▲]

Multi-period vehicle loading with stochastic release dates

E-print/Working paper (2012)

This paper investigates a multi-period vehicle loading problem with stochastic information regarding the release dates of items to be transported. The deterministic version of the problem can be ... [more ▼]

This paper investigates a multi-period vehicle loading problem with stochastic information regarding the release dates of items to be transported. The deterministic version of the problem can be formulated as a large-scale set covering problem. Several heuristic algorithms are proposed to generate decision policies for the stochastic optimization model over a long rolling horizon. The resulting policies have been extensively tested on instances which display the main characteristics of the industrial case-study that motivated the research. The tests demonstrate the benefits of the multi-period stochastic model over simple myopic strategies. A simple and efficient heuristic is shown to deliver good policies and to be robust against errors in the estimation of the probability distribution of the release dates. [less ▲]

A Rich Vehicle Routing Problem with Multiple Trips and Driver Shifts

Conference (2012)

This study is concerned with a rich vehicle routing problem (RVRP) encountered at a Belgian transportation company in charge of servicing supermarkets and hypermarkets belonging to a franchise. The ... [more ▼]

This study is concerned with a rich vehicle routing problem (RVRP) encountered at a Belgian transportation company in charge of servicing supermarkets and hypermarkets belonging to a franchise. The studied problem can be classified as a one-to-many-to-one pick-up and delivery problem, where there is a single depot from which all delivery customers are served and to which every pick-up demand must be carried back (Gutiérrez-Jarpa et al., 2010). The delivery and backhaul customers are considered to be two disjoint sets, where on a given route backhaul customers can be visited only after all delivery customers are served. Split deliveries and pick-ups are not allowed. The service at a customer must start within the given time window of the customer. However, it is not possible to serve a customer with every available vehicle, since the vehicles at the company’s disposal are of different types according to which the capacity changes. Therefore, our problem can be classified also as a heterogeneous fleet vehicle routing problem with customer-vehicle incompatibilities (Ceselli et al., 2009). The problem at hand requires that the same vehicle may be assigned to several routes, which leads to a multiple-trip RVRP. Furthermore, driver shifts are taken into account so that each vehicle of the fleet starts servicing the customers when the shift of the assigned driver starts. The shift duration is the same for all drivers. If the service of the vehicle exceeds SH, an overtime cost incurs to the transportation company. In such a case, a vehicle can be used during at most a fixed length of time. In addition to the vehicles of the company’s own fleet (i.e. internal vehicles), there is a possibility to request external vehicles for servicing some customers. External vehicles can be used for a fixed maximum amount of time and can start servicing customers at any desired time. A fixed reservation cost and distance and time based variable costs are incurred in the case of an external vehicle, while only distance based variable costs are incurred in the case of an internal vehicle. We employ a binary integer linear programming formulation in order to model our problem. The first constraint set ensures that each customer is visited at least once by either an internal or external vehicle. With the second constraint set, it is guaranteed that each internal vehicle is assigned to at most one tour. The last two constraint sets are the binary restrictions on the assignment variables. In order to solve the problem, we first relax the binary restrictions on the assignment variables and develop a column generation procedure, where we obtain two pricing problems, one for internal vehicles and the other one for external vehicles. The pricing problem of each internal vehicle can be formulated as an elementary shortest path problem with resource constraints, which can be solved using a dynamic programming algorithm based on a bounded bi-directional search (Righini and Salani, 2008). However, since an external vehicle can start the service at any point in time and is paid based on its total travel time, the second pricing algorithm has to take into account an infinite number of Pareto-optimal states (Liberatore et al., 2011). We discuss the efficient solution of the pricing subproblems and present preliminary computational results. [less ▲]

A capacity game in transportation management

Conference (2011, July 10)

This study analyzes the contractual relation between a retailer and a carrier with the aim of determining possible deviations from the optimal system performance. In order to face a random demand, the ... [more ▼]

This study analyzes the contractual relation between a retailer and a carrier with the aim of determining possible deviations from the optimal system performance. In order to face a random demand, the retailer submits a contract to the carrier based on the number of units transported and on the number of truck used. Then, before uncertainty is resolved, the carrier decides of the number of trucks that he reserves. Once the demand is known, the carrier may also request additional trucks at a higher cost. The result shows that the proposed contract does not coordinate the supply chain. [less ▲]

A capacity game in transportation management

Conference (2011, March 03)

Emerging concerns about competitiveness induce a growing number of firms to outsource their outbound transportation operations to third-party logistics providers. The resulting increase in the number of ... [more ▼]

Emerging concerns about competitiveness induce a growing number of firms to outsource their outbound transportation operations to third-party logistics providers. The resulting increase in the number of actors often leads to sub-optimal supply chain actions due to the antagonistic nature of the economic objectives of the partners. With the aim of determining possible deviations from the optimal system performance in such supply chains, this study analyzes the contractual relation between a retailer and a third-party logistics provider (carrier) using game theoretical approaches. The partners of the studied supply chain play a Stackelberg game in which the retailer is the leader and the carrier is the follower. The retailer faces an uncertain demand and needs to supply his store from his warehouse. he has the option of not meeting all the demand but must satisfy at least a minimum proportion of the fi nall demand. On the other hand, the carrier has to determine the number of trucks needed to satisfy this demand before uncertainty is resolved. Once demand is realized, if the reserved transportation capacity is insufficient, the carrier also has the possibility to requisition trucks at a higher price. We modelise the problem and propose a contract having two parameters : the quantity of transported items and the number of truck used. In our settings, the retailer is the one that submits the contract and the carrier decides if he accepts it or not. We compare this situation with a centralized model where a single decision maker takes all the decisions. [less ▲]

A capacity game in transportation planning

Conference (2010, January 28)

Emerging concerns about competitiveness induce a growing number of firms to outsource their outbound transportation operations to third-party logistics providers. The resulting increase in the number of ... [more ▼]

Emerging concerns about competitiveness induce a growing number of firms to outsource their outbound transportation operations to third-party logistics providers. The resulting increase in the number of actors often leads to sub-optimal supply chain actions due to the antagonistic nature of the economic objectives of the partners. With the aim of determining possible deviations from the optimal system performance in such supply chains, this study analyzes the contractual relation between a retailer and a third-party logistics provider (carrier) using game theoretical approaches. The partners of the studied supply chain play a Stackelberg game in which the retailer is the leader and the carrier is the follower. The retailer faces an uncertain demand and needs to supply his store from his warehouse. he has the option of not meeting all the demand but must satisfy at least a minimum proportion of the fi nall demand. On the other hand, the carrier has to determine the number of trucks needed to satisfy this demand before uncertainty is resolved. Once demand is realized, if the reserved transportation capacity is insufficient, the carrier also has the possibility to requisition trucks at a higher price. We modelise the problem and propose a contract having two parameters : the quantity of transported items and the number of truck used. In our settings, the retailer is the one that submits the contract and the carrier decides if he accepts it or not. We compare this situation with a centralized model where a single decision maker takes all the decisions. [less ▲]

RAPPORT DE RECHERCHE SUR UNE APPLICATION DE GESTION DE LA COLLABORATION DU SERVICE EXPÉDITION DU CHARGEUR AVEC LE TRANSPORTEUR

Report (2009)

Dans ce rapport, les échanges d'information d'un donneur d'ordre, d'un transporteur et d'un fournisseur au sein d'une chaîne de distribution sont analysés. Les possibilités de tracking et de tracing de ... [more ▼]

Dans ce rapport, les échanges d'information d'un donneur d'ordre, d'un transporteur et d'un fournisseur au sein d'une chaîne de distribution sont analysés. Les possibilités de tracking et de tracing de TransLogisTIC sont utilisés pour générer des KPI de performance et un modèle d'optimisation de quais de chargement est décrit dans une version Off-line et On-line. [less ▲]

Fret ferroviaire : vue prospective

Article for general public (2009)

Livre blanc de la Commission Européenne. Faiblesses du transport ferroviaire de fret : interopérabilité, ferroutage

RAPPORT DE RECHERCHE SUR L’OPTIMISATION DU ROUTAGE ET DU CHARGEMENT DE VEHICULES.

Report (2009)

Dans ce rapport confidentiel, un algorithme d'optimisation du chargement de véhicules a été mis au point dans le cadre d'une application avec un partenaire industriel.

Logistiques et energies

Article for general public (2008)