An improved method for discovering link criticality in transport networks

Quantitatively assessing the importance or criticality of each link in a network is of practical value to operators, as that can help them to increase the network's resilience, provide more efficient services, or improve some other aspect of the service. Betweenness is a graph-theoretical measure of centrality that can be applied to communication networks to evaluate link importance. However, as we illustrate in this paper, the basic definition of betweenness centrality produces inaccurate estimations as it does not take into account some aspects relevant to networking, such as the heterogeneity in link capacity or the difference between node-pairs in their contribution to the total traffic. A new algorithm for discovering link centrality in transport networks is proposed in this paper. It requires only static or semi-static network and topology attributes, and yet produces estimations of good accuracy, as verified through extensive simulations. Its potential value is demonstrated by an example application. In the example, the simple shortest-path routing algorithm is improved in such a way that it outperforms other more advanced algorithms in terms of blocking ratio

Estudi de la mobilitat en diferents xarxes de transport públic

Aquest projecte es centra en la realització d’un estudi de la mobilitat en diferents xarxes de transport públic. En particular, aquest estudi pretén ser una anàlisi comparativa de conceptes relacionats amb la topologia i navegabilitat de xarxes de metro de diferents països des d’un punt de vista innovador, tot realitzant una aproximació interdisciplinària a l’anàlisi de les xarxes.Es tracta d’un estudi centrat sobretot en conceptes i mètodes desenvolupats últimament en el camps de les Xarxes Complexes i de la Teoria de la Informació. Això ens ha permès focalitzar les nostres conclusions en les mesures de navegabilitat de les diferents xarxes així com en els paràmetres topològics que ens les defineixen, sense basar-nos en dades geogràfiques ni operatives. Els sistemes de metro estudiats en el present treball són els de Barcelona, Moscou, París i Nova York. Són sistemes que s’han desenvolupat en ambients històrics i culturals molt diversos fet que pot donar lloc a veure si aquesta circumstància és causant de diferències estructurals i de funcionament entre ells o bési pel contrari segueixen uns patrons de comportament semblants

Desenvolupament d’una metodologia de simulació mitjançant programari CFD per a la optimització d’agitadors

La dinàmica de fluids computacional (CFD) és una eina que serveix per analitzar mitjançantcomputadors diferents problemes que involucren fluxos de fluids. Els programes de CFD usen expressions matemàtiques no lineals que defineixen les equacions fonamentals de fluxos i transport de calor en fluids. Aquestes es resolen amb complexos algoritmes iteratius. Actualment aquesta eina és una part fonamental en els procés de disseny en moltes empreses relacionades amb la dinàmica de fluids. Les simulacions que es realitzen ambaquests programes s’ha demostrat que són fiables i que estalvien temps i diners, ja que eviten haver de realitzar els costosos processos d’assaig-error. En el projecte s’utilitza el programa de CFD Ansys CFX 11.0 per simular una agitació bifàsica composta per aigua i aire a temperatura ambient. Els objectius són determinar els paràmetres òptims de simulació que permetin recrear aquesta agitació, per posteriorment dissenyar un nou impulsor

Entorn de simulació per a xarxes òptiques de transport

Aquest projecte final de carrera pretén investigar i experimentar una nova línia de desenvolupament d’algorismes dinàmics. A partir de l’algorisme AntNet-QoS [2] s’ incorporen noves mesures a l’algorisme (mesura de l’amplada de banda disponible i jitter), les quals combinant amb la mesura de retard ja feta servir, permet adaptar-se millor a les condicions actuals del trànsit en la xarxa i als requeriments específics de qualitat (QoS) per part del trànsit

Integració d’un sistema de visió per computador a una cèl·lula flexible de transport

L’objectiu d’aquest projecte final de carrera és millorar les prestacions de la cel·la de fabricació actual duent a terme les següents fites: integració d’un sistema de visió artificial a la plataforma. Aquest sistema hade permetre la detecció i anàlisi dels objectes transportats, augmentant les seves possibilitats de manipulació i classificació. Es pretén eliminar la restricció actual que obliga a col•locar les peces en una posició fixa de la safata de transport; control centralitzat del procés a través d’un ordinador. El procés serà operat a través d’un computador industrial, el qual controlarà els diferents sistemes quecomponen la cel·la per tal que duguin a terme les seves funcions de forma coordinada; disseny i implementació d’una API del sistema. Es desenvoluparà la llibreria de control del sistema per tal de facilitar la programació del procés

A simulation-based algorithm for solving the resource-assignment problem in satellite telecommunication networks

This paper proposes an heuristic for the scheduling of capacity requests and the periodic assignment of radio resources in geostationary (GEO) satellite networks with star topology, using the Demand Assigned Multiple Access (DAMA) protocol in the link layer, and Multi-Frequency Time Division Multiple Access (MF-TDMA) and Adaptive Coding and Modulation (ACM) in the physical layer.

Speed of reaction-transport processes

We present an approach to determining the speed of wave-front solutions to reaction-transport processes. This method is more accurate than previous ones. This is explicitly shown for several cases of practical interest: (i) the anomalous diffusion reaction, (ii) reaction diffusion in an advective field, and (iii) time-delayed reaction diffusion. There is good agreement with the results of numerical simulations

Characterization and simulation of a CdTe detector for use in PET

The Voxel Imaging PET (VIP) Path nder project got the 4 year European Research Council FP7 grant in 2010 to prove the feasibility of using CdTe detectors in a novel conceptual design of PET scanner. The work presented in this thesis is a part of the VIP project and consists of, on the one hand, the characterization of a CdTe detector in terms of energy resolution and coincidence time resolution and, on the other hand, the simulation of the setup with the single detector in order to extend the results to the full PET scanner. An energy resolution of 0.98% at 511 keV with a bias voltage of 1000 V/mm has been measured at low temperature T=-8 ºC. The coincidence time distribution of two twin detectors has been found to be as low as 6 ns FWHM for events with energies above 500 keV under the same temperature and bias conditions. The measured energy and time resolution values are compatible with similar ndings available in the literature and prove the excellent potential of CdTe for PET applications. This results have been presented in form of a poster contribution at the IEEE NSS/MIC & RTSD 2011 conference in October 2011 in Valencia and at the iWoRID 2012 conference in July 2012 in Coimbra, Portugal. They have been also submitted for publication to "Journal of Instrumentation (JINST)" in September 2012.

Calculation of Franck-Condon factors including anharmonicity: simulation of the C2 H4+ X̃2B 3u←C2 H4X̃1 Ag band in the photoelectron spectrum of ethylene

Our new simple method for calculating accurate Franck-Condon factors including nondiagonal (i.e., mode-mode) anharmonic coupling is used to simulate the C2H4+X2B 3u←C2H4X̃1 Ag band in the photoelectron spectrum. An improved vibrational basis set truncation algorithm, which permits very efficient computations, is employed. Because the torsional mode is highly anharmonic it is separated from the other modes and treated exactly. All other modes are treated through the second-order perturbation theory. The perturbation-theory corrections are significant and lead to a good agreement with experiment, although the separability assumption for torsion causes the C2 D4 results to be not as good as those for C2 H4. A variational formulation to overcome this circumstance, and deal with large anharmonicities in general, is suggested

Improved earthquake response via simulation and integrated space- and ground-based technologies: the TREMOR proposal

Earthquakes occurring around the world each year cause thousands ofdeaths, millions of dollars in damage to infrastructure, and incalculablehuman suffering. In recent years, satellite technology has been asignificant boon to response efforts following an earthquake and itsafter-effects by providing mobile communications between response teamsand remote sensing of damaged areas to disaster management organizations.In 2007, an international team of students and professionals assembledduring theInternational Space University’s Summer Session Program in Beijing, Chinato examine how satellite and ground-based technology could be betterintegrated to provide an optimised response in the event of an earthquake.The resulting Technology Resources for Earthquake MOnitoring and Response(TREMOR) proposal describes an integrative prototype response system thatwill implement mobile satellite communication hubs providing telephone anddata links between response teams, onsite telemedicine consultation foremergency first-responders, and satellite navigation systems that willlocate and track emergency vehicles and guide search-and-rescue crews. Aprototype earthquake simulation system is also proposed, integratinghistorical data, earthquake precursor data, and local geomatics andinfrastructure information to predict the damage that could occur in theevent of an earthquake. The backbone of these proposals is a comprehensiveeducation and training program to help individuals, communities andgovernments prepare in advance. The TREMOR team recommends thecoordination of these efforts through a centralised, non-governmentalorganization.

Acoustic transport of charge and spins in GaAs-based heterostructures

Report for the scientific sojourn carried out at the Paul Drude Institut für Festkörperelektronik of the Stanford University, USA, from 2010 to 2012. The objective of this project is the transport and control of electronic charge and spin along GaAs-based semiconductor heterostructures. The electronic transport has been achieved by taking advantage of the piezolectric field induced by surface acoustic waves in non-centrosymmetric materials like GaAs. This piezolectric field separates photogenerated electrons and holes at different positions along the acoustic wave, where they acummulate and are transported at the same velocity as the wave. Two different kinds of structures have been studied: quantum wells grown along the (110) direction, both intrinsic and n-doped, as well as GaAs nanowires. The analysis of the charge acoustic transport was performed by micro-photoluminescence, whereas the detection of the spin transport was done either by analyzing the polarization state of the emitted photoluminescence or by Kerr reflectometry. Our results in GaAs quantum wells show that charge and spin transport is clearly observed at the non-doped structures,obtaining spin lifetimes of the order of several nanoseconds, whereas no acoutically induced spin transport was detected for the n-doped quantum wells. In the GaAs nanowires, we were able of transporting successfully both electrons and holes along the nanowire axis, but no conservation of the spin polarization has been observed until now. The photoluminescence emitted by these structures after acoustic transport, however, shows anti-bunching characteristics, making this system a very good candidate for its use as single photon emitters.

Vehículos-robot de guiado automático para almacenes y plantas de manufacturación

En este proyecto de final de carrera se realiza la gestión del tráfico de AGV y la simulación de su comportamiento al circular por una planta de estudio. Con la simulación se puede ver como varía el comportamiento de la planta al modificar el número de AGV y la velocidad a la que circulan. La planta objeto de estudio es un laboratorio de análisis clínico en el que se ha sustituido el sistema de transporte interno basado en cintas por uno con AGV, con lo que se ha podido comprobar que dicha sustitución es factible.

Simulation methods with extended stability for stiff biochemical kinetics

Background: With increasing computer power, simulating the dynamics of complex systems in chemistry and biology is becoming increasingly routine. The modelling of individual reactions in (bio)chemical systems involves a large number of random events that can be simulated by the stochastic simulation algorithm (SSA). The key quantity is the step size, or waiting time, τ, whose value inversely depends on the size of the propensities of the different channel reactions and which needs to be re-evaluated after every firing event. Such a discrete event simulation may be extremely expensive, in particular for stiff systems where τ can be very short due to the fast kinetics of some of the channel reactions. Several alternative methods have been put forward to increase the integration step size. The so-called τ-leap approach takes a larger step size by allowing all the reactions to fire, from a Poisson or Binomial distribution, within that step. Although the expected value for the different species in the reactive system is maintained with respect to more precise methods, the variance at steady state can suffer from large errors as τ grows. Results: In this paper we extend Poisson τ-leap methods to a general class of Runge-Kutta (RK) τ-leap methods. We show that with the proper selection of the coefficients, the variance of the extended τ-leap can be well-behaved, leading to significantly larger step sizes.Conclusions: The benefit of adapting the extended method to the use of RK frameworks is clear in terms of speed of calculation, as the number of evaluations of the Poisson distribution is still one set per time step, as in the original τ-leap method. The approach paves the way to explore new multiscale methods to simulate (bio)chemical systems.

Spacial debris collector robot : An AI-based and autonomous debris collector satellite simulation

In this paper the core functions of an artificial intelligence (AI) for controlling a debris collector robot are designed and implemented. Using the robot operating system (ROS) as the base of this work a multi-agent system is built with abilities for task planning.