Management of mobile resources in Physical Internet logistic models

International audienceThis paper deals with the concept of a "Physical Internet", the idea of building large logistics systems like the very successful Digital Internet network. The idea is to handle mobile resources, such as containers, just like Internet data packets. Thus, it is possible to use the principles of encapsulation and routing to optimize the freight. The problem is that mobile resources, such as containers, are not quite similar to data packets, because they are real and not dematerialized. Thus the handling and the storing of mobile resources, such as containers, will create imbalances in the logistics network, leading to starvation or overstocking of logistic network nodes. We propose in this paper a study addressing this problem leading to some solutions

A Proposal for an Open Logistics Interconnection Reference Model for a Physical Internet

International audienceThis paper presents a New Open Logistics Interconnection (NOLI) reference model for a Physical Internet, inspired by the Open Systems Interconnection (OSI) reference model for data networks. This NOLI model is compared to the OSI model, and to the Transmission Control Protocol/Internet Protocol (TCP/IP) model of Internet. It is also compared to the OLI model for a Physical Internet proposed by Montreuil. The main differences between the presented NOLI model and all the other models named above are in the appearance of definitions of physical objects in different layers and not just the lowest one. Also, the NOLI model we present locates the containerization and de-containerization operations in the topmost layer, and not in the layer below as does the OLI model. Finally, the NOLI model is closer to the TCP/IP and OSI models than the OLI model, keeping the integrity of the Link Layer that the OLI model divides in two layers, and keeping separate the Session and Transport OSI Layers that the OLI model unites in just one layer

Minimum Spanning Trees in Weakly Dynamic Graphs

International audienceIn this paper, we study weakly dynamic undirected graphs, that can be used to represent some logistic networks. The goal is to deliver all the delivery points in the network. The network exists in a mostly stable environment, except for a few edges known to be non-stable. The weight of each of these non-stable edges may change at any time (bascule or lift bridge, elevator, traffic congestion...). All other edges have stable weights that never change. This problem can be now considered as a Minimum Spanning Tree (MST) problem on a dynamic graph. We propose an efficient polynomial algorithm that computes in advance alternative MSTs for all possible configurations. No additional computation is then needed after any change in the problem because the MSTs are already known in all cases. We use these results to compute critical values for the non-stable weights and to pre-compute best paths. When the non-stable weights change, the appropriate MST may then directly and immediately be used without any recomputation

La gestion des ressources mobiles rares dans un Internet Physique sans ressources dédiées

International audienceInternet physique a pour objectif d'être un réseau logistique partageable et plus efficace. Le modèle de référence NOLI pour un Internet physique est un modèle de référence, inspiré du modèle de référence OSI pour les réseaux de données et Internet. Dans cette présentation, nous étudions certaines fonctionnalités de la couche 6, la couche qui gère les conteneurs, en particuliers les conteneurs à température dirigée (ou reefers), qui permettent par exemple le transports d'aliments, ou de médicaments. Nous proposons un algorithme efficace pour inciter au prix le plus bas les transporteurs à prendre puis à déposer des ressources rares, et même à dévier de leur chemin de retour qui sont souvent faits à vide ou presque pour le faire. Notre solution est basée sur le calcul de plus courts chemins (Warshall), puis sur la résolution d'un problème de transport (Methode de Stepping Stone) qui est une variante de la méthode du Simplex. Mots clés: Internet Physique, systèmes logistiques, mutualisation des ressources logistiques, problème de transport, routage

Author manuscript, published in "ICCES 09, Le Caire: Egypt (2009)" Paper ID=36 1 Area Failures and Reliable Distributed Applications

ABSTRACT — Because fault failures tend to affect whole areas, in some cases, and not only individual computers, we propose a new, efficient scheduling algorithm for problems in which tasks with precedence constraints and communication delays have to be scheduled on a virtual heterogeneous distributed multi areas system subject to the possibility of one complete area failure. Based on an extension of the Critical-Path Method CPM/PERT, our algorithm combines an optimal schedule when there is no failures, with some tasks duplication to provide fault-tolerance in the case of the failure of one area. Backup copies are not established for tasks that have already more than one original copy in different areas. The result is a schedule in polynomial time that is optimal when there is no area failure, and is a good reliable schedule in the case of any one area failure. We finally do some numerical experiments in which we use our algorithm on several semi-random DAGs and compare the optimal solutions with the reliable solutions found by this algorithm

Studying the Rerouting of Empty Carriers during their Return Trips to Manage Rare Mobile Resources in a Physical Internet

International audienceTo manage the unbalance between the needs in expensive containers (such as refrigerated containers or 'reefers') in some places, and the fact that the available empty containers of this kind are in another place, it is necessary to move these empty containers efficiently between places. In this paper, we use the empty carriers during their return trips after a delivery, to move the empty containers from the locations where they are, to the locations were they are needed. First, we use a method based on the Stepping Stone algorithm to compute a minimal cost list of moves in the associated transportation problem. Second, we use a heuristic to choose carriers during their return trips, and compute low cost possible path deviations that needed to accomplish these moves. A numerical example is presented at the end

AN ALGORITHM AND SOME NUMERICAL EXPERIMENTS FOR THE SCHEDULING OF TASKS WITH FAULT-TOLERANCY CONSTRAINTS ON HETEROGENEOUS SYSTEMS

In this paper, we propose an efficient scheduling algorithm for problems in which tasks with precedence constraints and communication delays have to be scheduled on an heterogeneous distributed system with an one fault hypothesis. Based on an extension of the Critical-Path Method CPM/PERT, our algorithm combines an optimal schedule with some additional tasks duplication, to provide fault-tolerance. Backup copies are not established for tasks that have already more than one original copy. The result is a schedule in polynomial time that is optimal when there is no failure, and is a good resilient schedule in the case of one server failure. We finally compare the optimal solutions with the resilient solutions found by this algorithm on several semi-random DAGs. I