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Valverde de Leganés, Spain

Zahr Vinuela J.,Charles III University of Madrid | Zahr Vinuela J.,Avda Of La University 30 | Perez Castellanos J.L.,Charles III University of Madrid
Composites Part A: Applied Science and Manufacturing | Year: 2011

The elastic behavior of Particulate Metal-Matrix Composites was studied by means of a multi-particle cell model, which includes a number of prismatic particles. An algorithm has been developed to produce spatial distributions of prismatic particles within a cell of periodic geometry. For an aluminium alloy reinforced with SiC particles, its elastic constants were obtained by FEM analysis of multi-particle cells representing various abstract micro-structural scenarios, defined as combinations of specific values of reinforcement volume fraction and particle aspect ratio, in different conditions of particle orientation. Results are classified according to isotropy characteristics of the different micro-structural scenarios under study. Using the well-known Halpin-Tsai equation, the results were extended to other intermediate fractions, providing new values for the Halpin-Tsai 's' parameter. It is also shown that results can be extended to other systems such as steel reinforced with SiC particles using the new 's' values. © 2011 Elsevier Ltd. All rights reserved. Source


Barbero G. J.F.,CSIC - Institute for the Structure of Matter | Barbero G. J.F.,Charles III University of Madrid | Prieto J.,Avda Of La University 30 | J S Villasenor E.,Charles III University of Madrid | J S Villasenor E.,Avda Of La University 30
European Journal of Physics | Year: 2015

This article discusses and explains the Hamiltonian formulation for a class of simple gauge invariant mechanical systems consisting of point masses and idealized rods. The study of these models may be helpful to advanced undergraduate or graduate students in theoretical physics to understand, in a familiar context, some concepts relevant to the study of classical and quantum field theories. We use a geometric approach to derive the Hamiltonian formulation for the model considered in the paper: four equal masses connected by six ideal rods. We obtain and discuss the meaning of several important elements, in particular, the constraints and the Hamiltonian vector fields that define the dynamics of the system, the constraint manifold, gauge symmetries, gauge orbits, gauge fixing, and the reduced phase space. © 2015 IOP Publishing Ltd. Source


Garcia-Reinoso J.,Avda Of La University 30 | Hernandez J.A.,Avda Of La University 30 | Seoane I.,Avda Of La University 30 | Vidal I.,Avda Of La University 30
Optical Switching and Networking | Year: 2014

The Interleaved Polling with Adapted Cycle Times (IPACT) algorithm for dynamic bandwidth allocation proposed for Ethernet Passive Optical Networks (EPONs) has been deeply analysed in the literature under Poisson traffic. However, the case when ONUs suddenly offer bursty traffic in the upstream channel of a PON has not been considered in such detail. This paper studies the performance behaviour of the upstream channel of EPONs employing IPACT with the gated-service disciple, under Poisson traffic together with sudden bursts. We show that one burst arrival produces a peak in the average transmission window of every ONU, lasting its effects for several cycle times, depending on the burst size and the average network load. Such a burst has a direct impact on the delay experienced by the packets of other ONUs. This is mathematically modelled using a modification of the formerly studied M/G/1 queue with vacations and validated with simulation. © 2014 Elsevier B.V. All rights reserved. Source


Gomez-Hernandez J.,Charles III University of Madrid | Gomez-Hernandez J.,Avda Of La University 30 | Soria-Verdugo A.,Charles III University of Madrid | Soria-Verdugo A.,Avda Of La University 30 | And 4 more authors.
Chemical Engineering Journal | Year: 2012

The fluidization conditions of a rotating distributor applied to a 3-D bubbling fluidized bed was studied to assess its potential use as a counteracting measure of defluidization phenomena. The performance of the fluidized bed operating under nominal conditions was characterized for the rotating and the static distributor configuration. Different methods of analysis in the time and frequency domain were applied to establish the performance of the fluidized bed. The frequency domain analysis suggests some kind of local structuring of fluidized bed dynamics imposed by the distributor motion. The punctual injection of water over the surface of the bed lead to a high cohesive wet region that tend to settle down on top of the distributor giving rise to defluidization. The water-induced defluidization tests reflect an improvement of the fluidization quality with the distributor rotation. © 2012 Elsevier B.V. Source


Soria-Verdugo A.,Charles III University of Madrid | Soria-Verdugo A.,Avda Of La University 30 | Garcia-Gutierrez L.M.,Charles III University of Madrid | Garcia-Gutierrez L.M.,Avda Of La University 30 | And 6 more authors.
Energy Conversion and Management | Year: 2014

The characteristic parameters of devolatilization, the activation energy and the frequency factor, can be obtained following different experimental approaches. In the Distributed Activation Energy Model (DAEM), these parameters are derived from several TGA curves that are typically obtained for constant, low heating rate experiments. Then, the results are used to model high heating rate processes typical of industrial combustors. In this work, a wide range of heating rates were employed to obtain different TGA curves of the biomass pyrolysis, in order to analyse the validity of DAEM when extrapolating the kinetic parameters obtained for low heating rate curves used in the laboratory to higher heating rates present in industrial applications. The TGA curves of the biomass pyrolysis employed in DAEM were varied from low heating rates (around 10 K/min, values typically found in the literature on DAEM), to high heating rates (up to 200 K/min). The differences in the activation energy and the frequency factor obtained for different heating rates, were evaluated and the validity of the model was discussed. The results show differences between the activation energy and the frequency factor obtained using low and high heating rates during the TGA tests. Therefore, if an accurate approximation is required when extrapolating the data to high heating rates, the tests should be carried out at high heating rates. © 2014 Elsevier Ltd. All rights reserved. Source

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