Abstract

International audience; The resolution of Air Traffic Control (ATC) conflicts is a constrained optimization problem : the goal is to propose, for a certain number, n, of aircraft, which might be in conflict in a near future, trajectories that satisfy the separation constraints between aircraft, and minimizes the delays due to the conflict's resolution. The type of conflict resolution trajectories we use allows to split the problem in two steps: first we choose, and freeze, what we call a configuration of the problem, i.e. for each aircraft, the direction in which the aircraft is diverted, and for each pair of aircraft, which of the two aircraft passes first at the crossing point of the two aircraft trajectories. We can then compute the optimal trajectories corresponding to this configuration, by solving a simple linear optimization problem. Thus we can use an Genetic Algorithm, along with a linear optimization algorithm, such as the simplex algorithm: the elements of the population, on which the GA operates, code configurations of the problem, and are evaluated using a linear optimization program.The advantage of this approach is that we get, as well as the fitness of an element of the population, the local optima corresponding to the configuration coded by this element. The GA actually searches for the global optimum among these local optima. We applied this methods to conflicts in which up to 6 aircraft are involved, and obtained really promising results. Document type: Part of book or chapter of book

Abstract

The conventional forwarding rule used by IP networks is to always choose the path with the shortest length – in terms of administrative link weights assigned to the links – to forward traffic. Lately, it has been proposed to use shortest-path-first routing to implement Traffic Engineering in IP networks, promising with a big boost in the profitability of the legacy network infrastructure. The idea is to set the link weights so that the shortest paths, and the traffic thereof, follow the paths designated by the operator. Unfortunately, traditional methods to calculate the link weights usually produce a bunch of superfluous shortest paths, often leading to congestion along the unconsidered paths. In this paper, we introduce and develop novel methods to increase the accuracy of this process and, by means of extensive simulations, we show that our proposed solution produces remarkably high quality link weights. Document type: Part of book or chapter of book

Abstract

[EN] Growing awareness in cutting transport costs and minimizing the environmental impact means that companies are increasingly interested in using the full truck load strategy in their supply tasks. This strategy consists of filling trucks completely with one product type or a mixture of products from the same supplier. This paper aims to propose a mixed-integer linear programming model and procedure to fill trucks which considers limitations of stocks, stock levels and unbalanced demand and minimization of the total number of trucks used in the full truck load strategy. The results obtained from a case study are presented and are exported in a conventional spreadsheet available for a company in the automotive industry. Maheut ., JP.; García Sabater, JP. (2013). A Mixed-Integer Linear Programming Model for Transportation Planning in the Full Truck Load Strategy to Supply Products with Unbalanced Demand in the Just in Time Context: A Case Study. IFIP Advances in Information and Communication Technology. 397:576-583. doi:10.1007/978-3-642-40361-3_73 S 576 583 397 Document type: Part of book or chapter of book

Abstract

During the last few years’ electric vehicles started to catch more attention. According to environmental policies of major states and unions of states, the number of electric vehicles will be increasing in the next years. In this thesis is studied the problem of unit commitment with high penetration of renewable sources, by presenting different methods for forecasting the renewable production. Furthermore, a model of a flexible load from electric vehicles is integrated into the unit commitment models. The aim of this research is to study the impact of the excessive load on the production side and compare different unit commitment models. It is demonstrated that optimized charging is cheaper than random charging for all the models and allows higher numbers of electric vehicles to be integrated into the electric system. Simulations showed that the cost of energy increased slightly by 1% for the optimized charging profile when using 100% electric vehicles penetration, whereas in the random charging profile the increase was around 15% for the same percentage of electric vehicles penetration.

Abstract

Las redes de tráfico urbano en las grandes ciudades están siendo ocupadas por una alta demanda de vehículos. Como resultado de este fenómeno, la contaminación, el tiempo total de viaje y el estrés se incrementan considerablemente. Actualmente, los problemas de congestión se investigan a partir de diferentes enfoques, uno de ellos es el modelado dinámico del tráfico vehicular, el cual es un elemento de diseño no para el monitoreo y control de tráfico a través de la gestión de la red semafórica. El modo de operación de los semáforos incide directamente en los índices de desempeñe no de movilidad. Por lo tanto, en la tesis se propusieron tres arquitecturas de control actuado de semáforos, es decir que ajustan sus variables según los volúmenes de tráfico de las vías. Una de estas estrategias es una combinación de sistemas de control cl ́asico con sistemas de control ́optimo organizados en una arquitectura jerárquica, que permitió escalar la coordinación de corredores a escenarios de una escala mayor, teniendo en cuenta las interacciones entre los subsistemas definidos. La metodología para la implementación y posterior validación de los m ́métodos propuestos consistió o en la integración del microfilmador de tráfico SUMO y el entorno de simulación Matlab a través de la interfaz Traci4Matlab, lo que permitió implementar las estrategias en un corredor de 5 intersecciones de la ciudad de Medellín. Los resultados obtenidos reflejaron una mejora entre el 36 % y 63 % de los modos de operación actuados respeto al tiempo fijo. Abstract; Urban traffic networks in big cities are being increasingly occupied by vehicles. As a result of this phenomenon, pollution, time spent by drivers and stress are increased considerably. Currently, congestion problems are investigated from different approaches. One of them is the dynamic modeling of vehicular traffic, which is a major factor in the monitoring and control through traffic light management. The mode of operation of traffic lights directly affects mobility performance index. Therefore in the thesis three traffic control architectures were proposed, they adjust their variables according to the traffic volumes. One of the strategies is a combination of classical control systems with optimal control systems, organized in a hierarchical architecture, which allowed to scale the coordination of corridors a ladder of a larger scale. The methodology for the implementation and validation of the proposed methods consisted of the integration of the SUMO traffic and Matlab through Traci4Matlab interface, which allowed the implementation of the strategies in a corridor of the city Of Medell ́ın. The results obtained describe an improvement between 36 % and 63 % of the modes of operation acted in relation to the fixed time. Real time implem entation is the most viii remarkable advantage, which motivates the use of the linear control

Abstract

Optimizing the way traffic is routed over networks has been of interest since we first started using computer networks to communicate and exchange information. Network technologies are constantly evolving and so do the underlying problems that need to be solved. This thesis focus on studying the recently proposed segment routing technology. In a traditional IP network, packets are routed using shorted paths according to weights that are configured on the network links. Segment routing offers a new way of routing traffic by allowing packets to do some detours on their way. Between these detours, traditional shortest path routing is used, making this technology have almost no usage overhead. We aim at providing a mathematical formalization of segment routing and showcase several of its use cases. We believe that such a formalization is going to help advance the research of the algorithmic aspects of segment routing by providing a solid mathematical foundation and notations which can serve as a starting point for others to research this topic. We leverage segment routing to solve traffic engineering problems, perform network monitoring and provide traffic duplication services that are robust to link failures. (FSA - Sciences de l'ingénieur) -- UCL, 2020

Abstract

Determination of bus stop locations and bus stop frequencies are important issues in public transportation planning. This study analyzes the relationships among demand, travel time, bus stop locations, frequency, fleet size and passenger capacity parameters and develops models for bus stop locations and bus service frequency using fuzzy linear programming and linear goal programming approaches. The models are microscopic and applied to determine the bus stop locations and bus service frequency in the city of Izmir, Turkey, where 26 bus routes pass through two stops in the center city. The fuzzy optimization model minimizes the passenger access time and in-vehicle travel time. The reduction of the values of the bus service frequency and time parameters derived by the two proposed models are validated by a cost function. Encouraging results are obtained. © Springer International Publishing Switzerland 2014.

Abstract

International audience; ECOFRAME ring is a novel network technology for the metropolitan transport that exploits optical packet switching and optical transparency. Each station in this ring is equipped with a tunable transmitter and a number of fixed receivers, able to extract traffic from a predefined set of wavelengths (number of wvl. ≥ 1). Receivers can be shared by different destinations, of- fering to this technology an ability to achieve significant CAPEX savings by using the optimum number of network resources, if properly dimensioned. In this paper we present a wide set of conclusions obtained when applying different network planning and traffic engineering tools in investigating an optimal design and evaluating performances of an ECOFRAME ring. More precisely, regarding network planning issues, we have estimated equipment costs, identified different network configurations and studied their impact on ring performances. Finally, we have found the potential savings when ring is properly designed. On the other hand, based on the previous results, we have identified the optimal ring configuration from price, capacity and scheduling point of view, suggested a cheap and fair scheduling policy for a general case and evaluated the positive impact of statistical multiplexing due to the WDM dimension, on the ring capacity. We have shown that an OPS ring that is properly dimensioned can achieve a solid QoS performance without slot reservation mechanisms.

Abstract

Nowadays, the aircraft is the most used transport to travel between two very distanced places since it is the fastest way. For these last years, the demand of flights has been increasing immensely, so the airports have been also suffering the same increase in workload. Congestion is the word for the imbalance between demand and capacity. After applying a Ground Holding Program (GHP) optimization process before departure to solve this problem in a previous work [1], in this project the Air Holding Program (AHP) is presented in order to minimize the economic costs once in the landing phase. The main goal of this final degree project is to implement a basic model of AHP to minimize the delay costs near the single destination airport, Barcelona-El Prat in this case. The model of AHP is based on a dynamic stochastic GHP. The problem is solved using Gurobi libraries. Firstly, a pre-tactical phase in [1] of GHP is applied to make flights wait on ground according to capacity constraints in the Barcelona Airport. Then, once the flights are already flying towards the destination and entering the analysed area (500 km from destination airport), these flights will perform a Free Route Airspace (FRA) route in order to make them fly a straight route trajectory to possibly shorten the flight duration, which will cause that the arrival queue be again disordered making the capacity constraint again violated. In order to minimize the air delay costs, a second optimization to assign air delay is applied called AHP. Once the flights are leaving this airspace, they will be communicated their final assigned holding. Finally when they are entering the landing phase, they should first pass through the holding procedure to hold the time needed according to the delay assigned. Some of the conclusions after this research is that if capacity is reduced in destination airport, firstly a GHP can be applied before departure [1]. Then, an AHP can be applied for a second optimization purpose. If traffic is directly taken to be applied an AHP, the capacity flexibility is very reduced, while using pre-tactical regulation the capacity could be as small as desired. This outlines the advantage of using GHP and AHP together. Furthermore, although the main objective is to minimize the delay costs, if the flights are arriving earlier than scheduled in the most optimal case, the delays could be negative values, which means that costs are saved.