Encontrado(s) 90654 resultado(s)
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Stochasticity enhances the gaining of bet-hedging strategies in contact-process-like dynamics

  • Hidalgo, Juan J.
  • Pigolotti, Simone
  • Muñoz Martínez, Miguel Ángel
Peer Reviewed

Caracterisation thermique et electrique d'un hacheur abaisseur

  • Alonso Llovet, Francisco Javier
Le sujet de ce stage concerne à la caractérisation d’un convertisseur buck de forte puissance, utilisé dans des convertisseurs statiques destinés aux tramways CITADIS (Alstom). Le rôle de ce convertisseur est d’adapter la tension de ligne de la caténaire (750V) pour réaliser un bus continu intermédiaire régulé à Ubus = 680V. Ce bus de tension continu alimentera trois convertisseurs destinés à la climatisation du tram et à un chargeur de batterie. Le principal objectif du stage consiste à vérifier si le hacheur abaisseur est capable de travailler avec des contraintes plus sévères. On devra déterminer les limites de fonctionnement du convertisseur buck, et plus concrètement déterminer la limite de puissance dont le hacheur est capable de travailler. On devra, donc, établir, rédiger et puis appliquer une procédure d’essais permettant de caractériser au mieux le module de puissance.

Control de velocitat pel motor de reclutància lineal del tren Telmag

  • Prats Ràfales, Marc
En aquest projecte es realitza la programació d’un llaç de control a les corrents de les bobines del motor de reluctància lineal del tren Telmag. Amb aquesta implementació es pretén millorar la velocitat de resposta i el comportament del motor de reluctància lineal quan el tren està en règim dinàmic. Primer s’estudia tota l’electrònica implementada al tren, per després realitzar un mòdul de lectura de corrents i, finalment, un mòdul de control. Es validen els resultats amb instrumentació de laboratori, simulant escrupolosament les senyals provinents de l’electrònica del tren segons documentació tècnica facilitada.

Verifying action semantics specifications in UML behavioral models (Extended version)

  • Planas, Elena
  • Cabot, Jordi
  • Gómez Seoane, Cristina
MDD and MDA approaches require capturing the behavior of UML models in sufficient detail so that the models can be automatically implemented/executed in the production environment. With this purpose, Action Semantics (AS) were added to the UML specification as the fundamental unit of behavior specification. Actions are the basis for defining the fine-grained behavior of operations, activity diagrams, interaction diagrams and state machines. Unfortunately, current proposals devoted to the verification of behavioral schemas tend to skip the analysis of the actions they may include. The main goal of this paper is to cover this gap by presenting several techniques aimed at verifying AS specifications. Our techniques are based on the static analysis of the dependencies between the different actions included in the behavioral schema. For incorrect specifications, our method returns a meaningful feedback that helps repairing the inconsistency.

Efficient bit-level design of an on-board digital TV demultiplexer

  • Sala Álvarez, José
  • Pagès Zamora, Alba Maria
  • Vázquez Grau, Gregorio
A bit-level description of the signal processing stage of an on-board integrated VLSI multi-carrier demodulator is presented in this paper, along with a description of the optimization procedure that has been developed for the signal processing functions1. The demultiplexer is capable of handling a varying number of carriers in a 36 MHz bandwidth on the satellite up-link. Its architecture has been optimized at bit-level in a way dependent on the known input signal statistics and carrier distributions allowed by the frequency plan., Peer Reviewed

Car-free cities: urban utopia or real perspective?

  • Bieda, Krzysztof
The appalling conditions of many 19th century industrial cities, brought by the Industrial Revolution, triggered numerous ideas and concepts looking for a better form of urban environment. Although most of the ideas may be today categorized as utopian, they had nevertheless significantly influenced urban development and heralded, at that time, the emergence of the Modernist City. With time, the Modernist City grew increasingly car-dependent. The crisis of the contemporary “Automobile City” stimulates, yet again, efforts to develop visions for a new, better city, free from ill-effects of car traffic. These visions may also fall into category of urban utopia, but they hopefully will, like in the past, set new directions in urban development and contribute to emergence of a new city form. Numerous research, planning and design works up today allow to speculate on the emerging new urban design paradigm. The visions of a future “Post Automobile City” go generally in two directions: a radical Car-free City model entirely devoid of automobile and – less radical - a Sustainable Mobility City, offering diverse modes of movement and related diverse life styles. The latter concepts would comprise both city forms: entirely car-free zones and “ordinary” urban areas accessible for cars, but more habitable due to priorities for pedestrian, bike and transit movement. We already observe growing number of car-free neighborhoods, mostly in the cities of Western Europe. They usually do not differ physically from ordinary housing complexes, other than added car- free arrangements. However, like in the past, we can expect that new urban forms will start to evolve following ongoing changes in urban transport. The paper attempts to answer the question if, and how, future changes towards sustainable mobility, may influence urban form, and in particular, how car-free residential areas in future cities may look like.

Integrated approach to assignment, scheduling and routing problems

  • Hervert-Escobar, Laura
  • López-Ramos, Francisco
  • Esquivel-Flores, Oscar A.
This research considers a real life case study that determines the minimum number of sellers required to attend a set of customers located in a certain region taking into account the weekly schedule plan of the visits, as well as the optimal route. The problem is formulated as a combination of assignment, scheduling and routing problems. In the new formulation, case studies of small size subset of customers of the above type can be solved optimally. However, this subset of customers is not representative within the business plan of the company. To overcome this limitation, the problem is divided into three phases. A greedy algorithm is used in Phase I in order to identify a set of cost-effective feasible clusters of customers assigned to a seller. Phase II and III are then used to solve the problem of a weekly program for visiting the customers as well as to determine the route plan using MILP formulation. Several real life instances of different sizes have been solved demonstrating the efficiency of the proposed approach.

Performance analysis of qam modulations applied to the linc transmitter

  • Casadevall Palacio, Fernando José
  • Valdominos Bardají, Antonio
Future mobile radiocommunications systems will use linear modulations because they show a higher spectrum efficiency than classical FM modulations. Furthermore, in order to use these modulations in hand-portable equipment, power efficiency is also requested for the power amplifiers. To obtain both power and spectrum efficiency, a LINC transmitter can be considered. The authors present an analysis of the effect of different types of imbalances between the parallel signal paths in a LINC transmitter. The system degradations are described in terms of adjacent channel rejection, (U/sub R/). Classical raised cosine (Nyquist filtered) 4, 16, and 64 QAM modulation patterns are taken into account, and in all cases, upper bounds for adjacent channel rejection as function of the gain and phase imbalances as well as of the guard band between adjacent channels are presented. Moreover, the impact of these imbalances in the system performance, characterized by means of the signal-to-noise ratio (SNR) increment needed to maintain a fixed error rate, is also considered. The results show that gain and phase imbalance between both RF paths could be a serious limitation for the LINC transmitter performance., Peer Reviewed

Revisiting variable radius circles in constructive geometric constraint solving

  • Ching-Shoei, C
  • Joan Arinyo, Robert
Variable-radius circles are common constructs in planar constraint solving and are usually not handled fully by algebraic constraint solvers. We give a complete treatment of variable-radius circles when such a circle must be determined simultaneously with placing two groups of geometric entities. The problem arises for instance in solvers using triangle decomposition to reduce the complexity of the constraint problem.

Design of a wavelength control for coherent detection of high order modulation formats

  • Fàbrega Sánchez, Josep Maria
  • Prat Gomà, Josep Joan
  • Molle, Lutz
  • Freund, Ronald
An automatic frequency control design is proposed and demonstrated. It is based on a high-speed optical VCO. An overall design has been performed, based on simulation results. Also, loop delay and phase noise impacts have been evaluated. Frequency discriminator and VCO proposed have been experimentally characterized, showing an agreement with simulation results., Peer Reviewed

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