Abstract

We present two heuristics based on constraint technology that solve the problem of generating air traffic management contingency plans, which are used in the case of a catastrophic infrastructure failure within EUROCONTROL, the European Organisation for the Safety of Air Navigation. Of the heuristics presented, one is based on constraint-based local search and tabu search, and the other one is a constraint programming and large neighbourhood search hybrid algorithm. The heuristics show that it is feasible to automate the development of contingency plans, which is currently done by human experts; this is desirable for several reasons, for example it would allow the contingency plans to be generated with an increased frequency. The generated plans were evaluated, by EUROCONTROL, to be at least as good as the human-made ones. Document type: Part of book or chapter of book

Abstract

We address the logical topology design problem (LTD) in WDM transport networks under static traffic assumptions. We start with one of the standard MILP formulations of the LTD problem that aims at optimizing the network congestion. We propose an improvement to this model that additionally optimizes the average hop count. We then derive a new MILP model that compels the traffic to be atomically routed. This last model enables fair comparisons of solutions obtained with MILP formulations and with metaheuristic algorithms. The latter allow us to deal with large size networks whereas the former are limited by their computational complexity. In this paper Tabu Search is used to tackle the LTD problem. We compare and discuss the logical topologies computed by the various methods described in the paper. Document type: Part of book or chapter of book

Abstract

Offline inter-domain outbound Traffic Engineering (TE) can be formulated as an optimization problem whose objective is to determine primary egress points for traffic exiting a domain. However, when egress point failures happen, congestion may occur if secondary egress points are not carefully determined. In this paper, we formulate a bi-level outbound TE problem in order to make outbound route selection robust to egress point failures. We propose a tabu search heuristic to solve the problem and compare the performance to three alternative approaches. Simulation results demonstrate that the tabu search heuristic achieves the best performance in terms of our optimization objectives and also keeps traffic disruption to a minimum. Document type: Part of book or chapter of book

Abstract

Part 5: Scheduling in Manufacturing and Other Applications; International audience; In this paper a new efficient tabu search algorithm for assigning freight to the intermodal transport connections was developed. There were also formulated properties of the problem that can be used to design robust heuristic algorithms based on the local search methods. The quality of solutions produced by the tabu search algorithm and by often recommended greedy approach were also compared. Document type: Conference object

Abstract

El objetivo de la tesis es diseñar un método metaheurístico basado en búsqueda tabú para resolver el problema del transporte BRT en el Distrito Federal con dos objetivos. Se propone aplicar técnicas metaheurísticas a problemas de optimización reales en el sector transporte. El problema de optimización en la operación del BRT es biobjetivo: reducción del tiempo total de viaje y del número de trasbordos, que no son comparables. Se diseñaron, implementaron y analizaron: algoritmo constructivo, procedimiento búsqueda local, procedimiento búsqueda tabú y procedimiento multiarranque (combina algoritmo constructivo con procedimiento de búsqueda tabú (MultiStartTabu)). Se creó un método específico para este problema, siguiendo la estrategia MOAMP para problemas multiobjetivo. Se compararon los resultados obtenidos por el algoritmo diseñado para resolver el problema con los obtenidos por una adaptación del NSGA II. MOAMP obtuvo curvas de eficiencia con mayor número de soluciones, que además dominan a las soluciones obtenidas con NSGA II.

Abstract

Multi-product pipelines are a significant and extensive mean of transporting petroleum based products from refineries to distribution centers. Previous contributions on tree-like pipeline scheduling problem have considered a simple structure with a single refinery connected to a mainline and some secondary lines only emerged from the mainline. In practice, however, a tree-like pipeline may also have several branches on a secondary line resulting in a complex structure, the so called multi-level tree-like pipeline. This paper addresses the short-term scheduling of multi-level tree-like pipelines with multiple refineries through a continuous time mixed-integer linear programming (MILP) model that considers multiple intermediate due dates for product demands. The objective is to satisfy product demands on time at the minimum operational costs, such as pumping, interface and backorder costs. The proposed model performance’s is shown by solving four examples. Document type: Article

Abstract

International audience; The constant increase in air traffic, since the beginning of the commercial aviation, has led to problems of saturation on airports, approaching areas,or higher airspace.Whereas the aircraft are largely optimized and automated, the air traffic control is still essentially relying on human experience.The present case study details two problems of air traffic management (ATM) for which a genetic algorithm based solution has been proposed. Thefirst application deals with the en route conflict resolution problem. The second application deals with the traffic management problem in an airport platform.