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The Technical University of Madrid or sometimes called Polytechnic University of Madrid is a Spanish University, located in Madrid. It was founded in 1971 as the result of merging different Technical Schools of Engineering and Architecture, originated mainly in the 18th century. Over 35,000 students attend classes during the year.According to the annual university ranking conducted by El Mundo, the Technical University of Madrid ranks as the top technical university in Spain, and second overall. The majority of its Engineering Schools are consistently ranked as leading academic institutions in Spain in their fields, and among the very best in Europe.The UPM is part of the TIME network, which groups fifty engineering schools throughout Europe. Wikipedia.

Alonso-Sanz R.,Technical University of Madrid
Quantum Information Processing | Year: 2015

The dynamics of a spatial quantum formulation of the iterated battle of the sexes game with imperfect information is studied in this work. The game is played with variable entangling in a cellular automata manner, i.e. with local and synchronous interaction. The effect of spatial structure is assessed in fair and unfair scenarios. © 2015, Springer Science+Business Media New York.

Aja-Fernandez S.,University of Valladolid | Aja-Fernandez S.,Technical University of Madrid | Tristan-Vega A.,University of Valladolid | Hoge W.S.,Harvard University
Magnetic Resonance in Medicine | Year: 2011

The characterization of the distribution of noise in the magnitude MR image is a very important problem within image processing algorithms. The Rician noise assumed in single-coil acquisitions has been the keystone for signal-to-noise ratio estimation, image filtering, or diffusion tensor estimation for years. With the advent of parallel protocols such as sensitivity encoding or Generalized Autocalibrated Partially Parallel Acquisitions that allow accelerated acquisitions, this noise model no longer holds. Since Generalized Autocalibrated Partially Parallel Acquisitions reconstructions yield the combination of the squared signals recovered at each receiving coil, noncentral Chi statistics have been previously proposed to model the distribution of noise. However, we prove in this article that this is a weak model due to several artifacts in the acquisition scheme, mainly the correlation existing between the signals obtained at each coil. Alternatively, we propose to model such correlations with a reduction in the number of degrees of freedom of the signal, which translates in an equivalent nonaccelerated system with a minor number of independent receiving coils and, consequently, a lower signal-to-noise ratio. With this model, a noncentral Chi distribution can be assumed for all pixels in the image, whose effective number of coils and effective variance of noise can be explicitly computed in a closed form from the Generalized Autocalibrated Partially Parallel Acquisitions interpolation coefficients. Extensive experiments over both synthetic and in vivo data sets have been performed to show the goodness of fit of out model. Copyright © 2010 Wiley-Liss, Inc.

del Monte J.P.,Technical University of Madrid | Dorado J.,CSIC - Institute of Agricultural Sciences
Weed Research | Year: 2011

Bromus diandrus is an emerging problem in barley crops in temperate climates, owing to its ability to adapt to certain farming techniques, as well as the absence of an efficient means of control. The aim of this study was to evaluate the germination of B. diandrus as a function of light conditions, time after ripening, temperature and water potential. Our results indicate that light conditions were the principal factor affecting germination and that seeds had negative photoblastism. Darkness modified the hydrotime parameters of the seeds somewhat, for example, by decreasing the values of Ψb and by favouring dormancy loss. The after-ripening time significantly modified the hydrotime parameters of the seeds, causing Ψb to drift towards more negative values (greater dormancy loss) as the after-ripening time increased. The combination of both variables explains the dormancy dynamics of this species in Mediterranean climates that are characterised by two distinct germination flushes, coinciding with two periods when soil humidity and temperature are not limiting. The first and main cohort of seedlings would emerge in autumn, originating from young buried seeds. A second cohort would emerge in the spring, from mature seeds on the surface of the soil. © 2011 The Authors. Weed Research © 2011 European Weed Research Society.

Callejo M.J.,Technical University of Madrid
Journal of Sensory Studies | Year: 2011

Bread, in its many varieties, has been a staple in the diets in many parts of the world throughout thousands of years. Although a general consensus has been reached regarding the classification of breads according to the degree of hydration of their dough, the presence or absence of fats or their volume, there is as yet no standard method with which to carry out a sensorial evaluation of bread. The objective of this work is to review the present state of the study of descriptive sensorial analysis of bread. Sensorial attributes are first classified according to the following four characteristics: appearance, odor, texture and flavor. Furthermore, some of the most important attributes are described as is their relation with the processes or characteristics of the ingredients used. Finally, a list is included with the terms and definitions of the attributes that should be taken into account for a descriptive sensory analysis of bread. © 2011 Wiley Periodicals, Inc..

Lario L.D.,National University of Rosario | Ramirez-Parra E.,Technical University of Madrid | Gutierrez C.,Autonomous University of Madrid | Spampinato C.P.,National University of Rosario | Casati P.,National University of Rosario
Plant Physiology | Year: 2013

ANTI-SILENCING FUNCTION1 (ASF1) is a key histone H3/H4 chaperone that participates in a variety of DNA- and chromatin-related processes, including DNA repair, where chromatin assembly and disassembly are of primary relevance. Information concerning the role of ASF1 proteins in the post-ultraviolet (UV) response in higher plants is currently limited. In Arabidopsis (Arabidopsis thaliana), an initial analysis of in vivo localization of ASF1A and ASF1B indicates that both proteins are mainly expressed in proliferative tissues. In silico promoter analysis identified ASF1A and ASF1B as potential targets of Elongation Factor2 (E2F) transcription factors. These observations were experimentally validated, both in vitro, by electrophoretic mobility shift assays, and in vivo, by chromatin immunoprecipitation assays and expression analysis using transgenic plants with altered levels of different E2F transcription factors. These data suggest that ASF1A and ASF1B are regulated during cell cycle progression through E2F transcription factors. In addition, we found that ASF1A and ASF1B are associated with the UV-B-induced DNA damage response in Arabidopsis. Transcript levels of ASF1A and ASF1B were increased following UV-B treatment. Consistent with a potential role in UV-B response, RNA interference-silenced plants of both genes showed increased sensitivity to UV-B compared with wild-type plants. Finally, by coimmunoprecipitation analysis, we found that ASF1 physically interacts with amino-terminal acetylated histones H3 and H4 and with acetyltransferases of the Histone Acetyl Transferase subfamily, which are known to be involved in cell cycle control and DNA repair, among other functions. Together, we provide evidence that ASF1A and ASF1B are regulated by cell cycle progression and are involved in DNA repair after UV-B irradiation. © 2013 American Society of Plant Biologists. All Rights Reserved.

Tordesillas L.,Technical University of Madrid
Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology | Year: 2013

Since intestinal absorption of food protein can trigger an allergic reaction, the effect of plant food allergen on intestinal epithelial cell permeability and its ability to cross the epithelial monolayer was evaluated. To study the interaction of Pru p 3 with intestinal epithelium, its natural entrance, analyzing transport kinetics and cellular responses that trigger. This was achieved using Pru p 3, the peach LTP, as a model. Enterocytic monolayers were established by culturing Caco 2 cells, as a model of enterocytes, on permeable supports that separate the apical and basal compartments. Pru p 3 was added to the apical compartment, the transepithelial resistance (TEER) was measured, and the transport was quantified. The peach allergen that crossed the cell monolayer was detected in the cell fraction and in the basal medium by immunodetection with specific antibodies and the quantity was measured by ELISA assay. Pru p 3 was able to cross the monolayer without disturbing the integrity of the tight junctions. This transport was significantly higher than that of a non-allergenic peach LTP, LTP1, and occurred via lipid raft pathway. The incubation of Caco 2 cells with Pru p 3 and LTP1 produced the expression of epithelial-specific cytokines TSLP, IL33 and IL25. These results suggest that Pru p 3 was able to cross the cell monolayer by the transcellular route and then induce the production of Th2 cytokines. The results of the present study represent a step towards clarifying the importance of Pru p 3 as a sensitizer. The capacity of food allergens to cross the intestinal monolayer could explain their high allergenic capacity and its fast diffusion through the body associating to severe symptoms. © 2013 John Wiley & Sons Ltd.

Villen-Altamirano J.,Technical University of Madrid
Reliability Engineering and System Safety | Year: 2010

The reliability of consecutive-k-out-of-n: F repairable systems and (k-1)-step Markov dependence is studied. The model analyzed in this paper is more general than those of previous studies given that repair time and component lifetimes are random variables that follow a general distribution. The system has one repair service which adopts a priority repair rule based on system failure risk. Since crude simulation has proved to be inefficient for highly dependable systems, the RESTART method was used for the estimation of steady-state unavailability, MTBF and unreliability. Probabilities up to the order of 10-16 have been accurately estimated with little computational effort. In this method, a number of simulation retrials are performed when the process enters regions of the state space where the chance of occurrence of a rare event (e.g., a system failure) is higher. The main difficulty for the application of this method is to find a suitable function, called the importance function, to define the regions. Given the simplicity involved in changing some model assumptions with RESTART, the importance function used in this paper could be useful for dependability estimation of many systems. © 2009 Elsevier Ltd. All rights reserved.

Ahedo E.,Technical University of Madrid
Plasma Physics and Controlled Fusion | Year: 2011

Plasma thrusters are challenging the monopoly of chemical thrusters in space propulsion. The specific energy that can be deposited into a plasma beam is orders of magnitude larger than the specific chemical energy of known fuels. Plasma thrusters constitute a vast family of devices ranging from already commercial thrusters to incipient laboratory prototypes. Figures of merit in plasma propulsion are discussed. Plasma processes and conditions differ widely from one thruster to another, with the pre-eminence of magnetized, weakly collisional plasmas. Energy is imparted to the plasma via either energetic electron injection, biased electrodes or electromagnetic irradiation. Plasma acceleration can be electrothermal, electrostatic or electromagnetic. Plasma-wall interaction affects energy deposition and erosion of thruster elements, and thus is central for thruster efficiency and lifetime. Magnetic confinement and magnetic nozzles are present in several devices. Oscillations and turbulent transport are intrinsic to the performances of some thrusters. Several thrusters are selected in order to discuss these relevant plasma phenomena. © 2011 IOP Publishing Ltd.

Orden J.C.G.,Technical University of Madrid
Nonlinear Dynamics | Year: 2010

There are many difficulties involved in the numerical integration of index-3 Differential Algebraic Equations (DAEs), mainly related to stability, in the context of mechanical systems. An integrator that exactly enforces the constraint at position level may produce a discrete solution that departs from the velocity and/or acceleration constraint manifolds (invariants). This behavior affects the stability of the numerical scheme, resulting in the use of stabilization techniques based on enforcing the invariants. A coordinate projection is a post-stabilization technique where the solution obtained by a suitable DAE integrator is forced back to the invariant manifolds. This paper analyzes the energy balance of a velocity projection, providing an alternative interpretation of its effect on the stability and a practical criterion for the projection matrix selection. © Springer Science+Business Media B.V. 2009.

Montes M.J.,Spanish University for Distance Education (UNED) | Rovira A.,Spanish University for Distance Education (UNED) | Munoz M.,Spanish University for Distance Education (UNED) | Martinez-Val J.M.,Technical University of Madrid
Applied Energy | Year: 2011

The contribution of solar thermal power to improve the performance of gas-fired combined cycles in very hot and dry environmental conditions is analyzed in this work, in order to assess the potential of this technique, and to feature Direct Steam Generation (DSG) as a well suited candidate for achieving very good results in this quest. The particular Integrated Solar Combined Cycle (ISCC) power plant proposed consists of a DSG parabolic trough field coupled to the bottoming steam cycle of a Combined Cycle Gas Turbine (CCGT) power plant. For this analysis, the solar thermal power plant performs in a solar dispatching mode: the gas turbine always operates at full load, only depending on ambient conditions, whereas the steam turbine is somewhat boosted to accommodate the thermal hybridization from the solar field.Although the analysis is aimed to studying such complementary effects in the widest perspective, two relevant examples are given, corresponding to two well-known sites: Almería (Spain), with a mediterranean climate, and Las Vegas (USA), with a hot and dry climate. The annual simulations show that, although the conventional CCGT power plant works worse in Las Vegas, owing to the higher temperatures, the ISCC system operates better in Las Vegas than in Almería, because of solar hybridization is especially well coupled to the CCGT power plant in the frequent days with great solar radiation and high temperatures in Las Vegas. The complementary effect will be clearly seen in these cases, because the thermal power provided by the solar field compensates the gas turbine part load performance due to the high temperatures. The economical analysis points out that this hybrid scheme is a cheaper way to exploit concentrated solar energy, although it is limited to a small fraction of the combined cycle power. The analysis also shows that the marginal cost of solar electricity is strongly influenced by the goodness of coupling, so this cost is lower in Las Vegas than in Almería. © 2011 Elsevier Ltd.

Fernandez S.,CIEMAT | De Abril O.,Technical University of Madrid | Naranjo F.B.,University of Alcala | Gandia J.J.,CIEMAT
Solar Energy Materials and Solar Cells | Year: 2011

ZnO:Al films deposited at 250 °C on Corning glass by radio frequency magnetron sputtering were studied for their use as front contact for thin film silicon solar cells. For this purpose, a two-step etching method combining different concentrations of diluted hydrochloric acid (from 0.1% to 3%) with different etching times was developed. Its influence on morphological, electrical and optical properties of the etched films was evaluated. This new etching method led to more uniform textured surfaces, where the electrical properties remained unchangeable after the etching process, and with adapted light scattering properties similar to those exhibited by commercial substrates. © 2011 Elsevier B.V.

Alonso Zotes F.,Technical University of Madrid | Santos Penas M.,Complutense University of Madrid
Information Sciences | Year: 2010

The aim of this paper is to study the use of a genetic algorithm (GA) to optimise the ascent trajectory of a conventional two-stage launcher. The equations of motion of this system lack analytical solutions, and the number of adjustable parameters is large enough that the use of some non-traditional optimisation method becomes necessary. Two different missions are considered: first, to reach the highest possible stable, circular Low Earth Orbit (LEO); and second, to maximise the speed of a tangential escape trajectory. In this study, three variables are tuned and optimised by the GA in order to satisfy mission constraints while maximising the target function. The technical characteristics and limitations of the launcher are taken into account in the mission model, and a fixed payload weight is assumed. A variable mutation rate helps expand the search area whenever the population of solutions becomes uniform, and is shown to accelerate convergence of the GA in both cases. The obtained results are in agreement with technical specifications and solutions obtained in the past. © 2009 Elsevier Inc. All rights reserved.

Munoz-Ferreras J.M.,University of Alcala | Perez-Martinez F.,Technical University of Madrid
IEEE Geoscience and Remote Sensing Letters | Year: 2010

Inverse synthetic aperture radar (ISAR) is an all-weather radar technique which may generate high-resolution images of noncooperative targets. The standard range-Doppler algorithm (RDA) is usually employed for image generation. However, the images obtained with RDA are usually blurred because of the relative motion between radar and target. As a consequence, motion compensation techniques should be used to improve the imagery quality. The range-instantaneous-Doppler (RID) technique based on timefrequency transforms has been proposed for obtaining a sequence of focused ISAR images without the need of using motion compensation techniques. However, in this letter, it is clearly shown that the migration of the target scatterers in slant range indirectly induces Doppler spreading of the scatterers' point spread function in each of the ISAR images obtained by the RID technique. This Doppler spreading means blurring. It is important to highlight that the migration in slant range may be caused not only by the radial component of the translational motion but also by the rotational motion. The application of motion compensation techniques prior to the use of the RID technique allows us to mitigate the Doppler spreading, as shown here both for simulated and live data acquired by a high-resolution coherent radar. © 2009 IEEE.

The aim of this work is to show the effects in a PV cell of the combined profiles of non-uniform temperature and radiation. Particular attention is paid to the modelling of cell operation at open circuit voltage with those profiles, as long as they serve as a general model in different circumstances: combined direct Gaussian temperature and radiation profiles, with several temperature amplitudes and movement of these profiles across the cell; analysis under Gaussian concentrated illumination and inverse Gaussian temperature profile simulating a general cell cooling device. In addition, we will study the cell behaviour under truncated radiation and temperature profiles. Irregular radiation and temperature distributions will also be studied. © 2010 Elsevier Ltd.

Marcos J.,Public University of Navarra | Marroyo L.,Public University of Navarra | Lorenzo E.,Technical University of Madrid | Alvira D.,Red Electrica de Espana | Izco E.,Acciona
Progress in Photovoltaics: Research and Applications | Year: 2011

The variable nature of the irradiance can produce significant fluctuations in the power generated by large grid-connected photovoltaic (PV) plants. Experimental 1 s data were collected throughout a year from six PV plants, 18 MWp in total. Then, the dependence of short (below 10 min) power fluctuation on PV plant size has been investigated. The analysis focuses on the study of fluctuation frequency as well as the maximum fluctuation value registered. An analytic model able to describe the frequency of a given fluctuation for a certain day is proposed. © 2010 John Wiley & Sons, Ltd.

Fumero-Reveron A.,Technical University of Madrid
Profesional de la Informacion | Year: 2011

The rapid pace at which trends, news, tools, technologies, devices, services, etc. come and go in our information society requires of every citizen a certain capacity to internalize the perceived complexity behind the metaphors we are used to hearing from IT professionals, as well as to assess the impact of these changes on everyday life. The article briefly introduces and develops a simplified model that helps in presenting three key phenomena that are relevant enough for understanding the current developmental stage of the Web as most visible part of the Network itself. It is based on three elements (infotechnologies, people and content) and it is developed along three axes (information, relations and communication). The model also wants to serve the reader as an intellectual and conceptual tool to delve into any of its dimensions.

Lafuente A.,Technical University of Madrid | Piera M.,Spanish University for Distance Education (UNED)
Annals of Nuclear Energy | Year: 2011

Although nuclear breeder reactors are a promising way to enhance the potential energy currently retrievable from the Uranium reserves, they still have disadvantages because of their safety features (i.e. poor stabilizing mechanisms) and the security of their fuel cycle (diversion of Pu for non-civilian purposes). Loading natural nuclear fuels to a reactor and completely burning them without reprocessing would be ideal, however, this is not possible in critical reactors due to the limitations imposed by the maximum achievable burn-up. An alternative option to attain very high percentages of nuclear natural materials exploitation, while meeting other objectives of Nuclear Sustainability, could consist of using externally-driven subcritical reactors to reach the desired high burn-ups (of the order of 30% and more) without reprocessing. Such scheme would lead to an efficient exploitation of the available raw material, without any risk of proliferation. Exploring this type of reactor concept, this paper analyzes the different ways to accomplish this goal while identifying potential setbacks. © 2010 Elsevier Ltd. All rights reserved.

Garcia M.,Public University of Navarra | Marroyo L.,Public University of Navarra | Lorenzo E.,Technical University of Madrid | Perez M.,Acciona
Progress in Photovoltaics: Research and Applications | Year: 2011

Field data of soiling energy losses on PV plants are scarce. Furthermore, since dirt type and accumulation vary with the location characteristics (climate, surroundings, etc.), the available data on optical losses are, necessarily, site dependent. This paper presents field measurements of dirt energy losses (dust) and irradiance incidence angle losses along 2005 on a solar-tracking PV plant located south of Navarre (Spain). The paper proposes a method to calculate these losses based on the difference between irradiance measured by calibrated cells on several trackers of the PV plant and irradiance calculated from measurements by two pyranometers (one of them incorporating a shadow ring) regularly cleaned. The equivalent optical energy losses of an installation incorporating fixed horizontal modules at the same location have been calculated as well. The effect of dirt on both types of installations will accordingly be compared. © 2010 John Wiley & Sons, Ltd.

Inarrea M.,University of La Rioja | Pelaez J.,Technical University of Madrid
Journal of Guidance, Control, and Dynamics | Year: 2010

Electrodynamic tethers working in inclined orbit are affected by dynamic instability due to continuous pumping of energy from electromagnetic forces into the tether attitude motion. This paper proposes a new control scheme to remove this instability. The procedure is based on an extended delay feedback control method that has been used successfully in problems with one degree of freedom. When simple dynamic models are used, unstable periodic orbits appear in the attitude dynamics. By adding appropriate forces to the system, the unstable periodic orbits become asymptotically stable. Such a stabilized periodic orbit can be taken as the starting point for the operation of the electrodynamic tether. This analysis assumes a rigid tether, with two end masses orbiting along a circular inclined orbit, and a constant tether current, which does not depend on the attitude and orbital position of the tether. The Earth's magnetic field is modeled as a dipole aligned with the Earth's rotation axis. Copyright © 2009.

Tablero C.,Technical University of Madrid
Applied Physics Letters | Year: 2010

The Inx Ga1-x N alloys present levels as a result of the intentional (doped) or unintentional (contamination) introduction of C atoms into the host semiconductor. The III-V nitride semiconductors and their alloys usually crystallize in the wurtzite structure although the zinc blende structure has also been grown. We obtained the Inx Ga1-x N:C ionization energies from first-principles calculations of the two ordered wurtzite and zinc blende structures using different exchange and correlation terms. In accordance with the experimental results, the ionization levels could give rise, on some occasions, to a metallic impurity band. © 2010 American Institute of Physics.

Diez-Pascual A.M.,CSIC - Institute of Polymer Science and Technology | Naffakh M.,CSIC - Institute of Polymer Science and Technology | Naffakh M.,Technical University of Madrid
Polymer | Year: 2012

Novel carbon fiber (CF)-reinforced poly(phenylene sulphide) (PPS) laminates incorporating inorganic fullerene-like tungsten disulfide (IF-WS 2) nanoparticles were prepared via melt-blending and hot-press processing. The influence of the IF-WS 2 on the morphology, thermal, mechanical and tribological properties of PPS/CF composites was investigated. Efficient nanoparticle dispersion within the matrix was attained without using surfactants. A progressive rise in thermal stability was found with increasing IF-WS 2 loading, as revealed by thermogravimetric analysis. The addition of low nanoparticle contents retarded the crystallization of the matrix, whereas concentrations equal or higher than 1.0 wt% increased both the crystallization temperature and degree of crystallinity compared to those of PPS/CF. Mechanical tests indicated that with only 1.0 wt% IF-WS 2 the flexural modulus and strength of PPS/CF improved by 17 and 14%, respectively, without loss in toughness, ascribed to a synergistic effect between the two fillers. A significant enhancement in the storage modulus and glass transition temperature was also observed. Moreover, the wear rate and coefficient of friction strongly decreased, attributed to the lubricant role of the IF-WS 2 combined with their reinforcing effect. These inorganic nanoparticles show great potential to improve the mechanical and tribological properties of conventional thermoplastic/CF composites for structural applications. © 2012 Elsevier Ltd. All rights reserved.

The physical and mechanical properties of metal matrix composites were improved by the addition of reinforcements. The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys (6061 and 7015) at high temperatures were studied. Titanium diboride (TiB2) particles were used as the reinforcement. All the composites were produced by hot extrusion. The tensile properties and fracture characteristics of these materials were investigated at room temperature and at high temperatures to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy. TiB2 particles provide high stability of the aluminium alloys (6061 and 7015) in the fabrication process. An improvement in the mechanical behaviour was achieved by adding TiB2 particles as reinforcement in both the aluminium alloys. Adding TiB2 particles reduces the ductility of the aluminium alloys but does not change the microscopic mode of failure, and the fracture surface exhibits a ductile appearance with dimples formed by coalescence. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2011.

Paz-Ferreiro J.,Technical University of Madrid | Paz-Ferreiro J.,CAS South China Botanical Garden | Fu S.,CAS South China Botanical Garden
Land Degradation and Development | Year: 2016

Soil quality is threatened by the increase in human population and by the fact that most of the cultivable land is intensively used. The initial interest in this topic focused on defining soil quality but shifted into how to measure soil quality in the late 1990s. There is a general agreement that soil biochemical, microbiological and biological properties are more suitable than physical and/or chemical properties for the purpose of estimating alterations in soil quality and hence soil degradation. To date, most studies have used microbial biomass, soil respiration and enzymatic activities to obtain soil quality indices, whereas less focus has been given to soil fauna (microarthropods and nematodes). This article aims to do a critical review of soil quality indices based on soil biological and biochemical activities, mainly microbial biomass, soil respiration and the activity of several enzymes. Limitations within the database of articles that are focussed on broad scale application of soil quality indices include the difficulty of selecting the highest quality soils for comparison purposes, lack of standardisation of analytical methods, and inclusion of an insufficient number of soil types and ecosystems. There is a need to validate soil quality indices, both, spatially and temporally and to explore the use of indices that integrate faunal and microbial measurements. © 2016 John Wiley & Sons, Ltd.

Rodriguez-Navarro A.,Technical University of Madrid
PLoS ONE | Year: 2012

A Kuhnian approach to research assessment requires us to consider that the important scientific breakthroughs that drive scientific progress are infrequent and that the progress of science does not depend on normal research. Consequently, indicators of research performance based on the total number of papers do not accurately measure scientific progress. Similarly, those universities with the best reputations in terms of scientific progress differ widely from other universities in terms of the scale of investments made in research and in the higher concentrations of outstanding scientists present, but less so in terms of the total number of papers or citations. This study argues that indicators for the 1% high-citation tail of the citation distribution reveal the contribution of universities to the progress of science and provide quantifiable justification for the large investments in research made by elite research universities. In this tail, which follows a power low, the number of the less frequent and highly cited important breakthroughs can be predicted from the frequencies of papers in the upper part of the tail. This study quantifies the false impression of excellence produced by multinational papers, and by other types of papers that do not contribute to the progress of science. Many of these papers are concentrated in and dominate lists of highly cited papers, especially in lower-ranked universities. The h-index obscures the differences between higher- and lower-ranked universities because the proportion of h-core papers in the 1% high-citation tail is not proportional to the value of the h-index. © 2012 Alonso Rodríguez-Navarro.

Filippini R.,Independent Research Consultant | Silva A.,Technical University of Madrid
Reliability Engineering and System Safety | Year: 2014

Critical infrastructures provide services that are essential for the support of everyday activities in modern societies. Being the result of a continuous process of integration of diverse technologies and organizations, they require a multi-disciplinary, systemic approach in order to be understood. In this respect, one of the most challenging issues is the analysis of infrastructures under disturbance or malfunctioning, and their ability to resist, react and recover, in a word the resilience. This paper presents a methodology of resilience analysis of systems of systems, with infrastructures as a special instance. A conceptual representation of the infrastructure, based on the functional relationships among its components, is given and then analyzed with respect to its structural and dynamic properties. Most critical and vulnerable components are identified. The response of the system to failure propagation is simulated in order to check if it is able to cope with them and recover in a resilient fashion. The analysis outcomes are used for a resilience-informed review of the infrastructure. © 2013 Published by Elsevier Ltd. All rights reserved.

Sanchez-Sanz M.,Technical University of Madrid
Combustion and Flame | Year: 2012

The conditions that lead to the extinction of a premixed flame propagating along a channel of height 2h 1~δ T are studied using the thermo-diffusive approximation, with δ T=D T/S L, D T and S L representing, respectively, the thermal flame thickness, the thermal conductivity and the planar flame speed.It is found that flame propagation is greatly affected by conductive heat losses to the wall ∂T/∂n=b̃(T-T0), where n denotes the transverse distance to the wall, T and T 0 are, respectively, the fluid's and wall's temperature and b̃ is the heat transfer parameter. The sensitivity of the flame to heat losses grows as the channel narrows, leading to complete flame extinction at extremely small values of b̃=b̃c.As a way to overcome flame quenching at the walls, Lloyd and Weinberg [1] proposed the recirculation of part of the heat stored in the exhaust gases to preheat the cold combustible mixture. In order to understand the flame dynamics in the presence of heat recirculation, we analyze the problem of two parallel channels with a combustible mixture and an inert fluid moving in opposite directions, with maximum velocities m 1 and m 2 respectively, and where heat exchange is permitted through the common wall separating both channels. It is shown that flame extinction occurs if the velocity ratio m 2/m 1 is outside the range m 2/m 1∈[m 21,min m 21.max], where the limiting values m 21,min and m 21.max are obtained numerically for a given set of parameters. The amplitude of this range depends, mainly, on the Damkhöler number d=[h 1/(D T/S L)] 2, quantity that represents the ratio between the channel's height h 1 and the thermal flame thickness D T/S L. It is shown that heat recirculation is capable of extending combustion to very small h 1, but there is still a minimum value of the Damkhöler number d min below which combustion is not possible. The evolution of d min is computed numerically to give values as small as d=0.0025 for a given combination of the geometric parameters of the problem. The maximum flame temperature computed in the parallel channel configuration rises above the adiabatic flame temperature T e due to the effect of the heat recirculation. This effect becomes more significant as d is reduced, leading to maximum temperatures close to T≃1.4T e in very narrow channels. © 2012 The Combustion Institute.

Canaud B.,CEA DAM Ile-de-France | Laffite S.,CEA DAM Ile-de-France | Temporal M.,Technical University of Madrid
Nuclear Fusion | Year: 2011

Shock ignition is investigated for non-cryogenic direct-drive double-shell targets. The fuel assembly is obtained by direct laser light absorbed in the external shell. The latter implodes and impacts the inner shell. The ignition is produced by a spherically convergent shock launched by a laser spike added at the end of the main laser drive. Analyses are carried out with and without a correction for the fuel assembly laser pulse. The correction is made by lowering the assembling laser pulse in order to maintain the implosion velocity constant when the ignitor spike is added. The results indicate that a moderate thermonuclear gain (∼2 for spike power in the range 100-250 TW) can be achieved while the ignition threshold is displaced towards lower laser energies. The thermonuclear yield is tuned by the power in the spike which is a free parameter. A better gain is obtained when the main drive laser pulse is not corrected due to the dual effect of the increases in implosion velocity and in the DT ion temperature when the ignitor shock collapses. © 2011 IAEA, Vienna.

Riaza R.,Technical University of Madrid
IEEE Transactions on Circuits and Systems II: Express Briefs | Year: 2010

This brief presents a characterization of nondegenerate circuits with active memristors, i.e., memristors with a negative memductance at certain operating ranges. The analysis proceeds by characterizing index-one configurations in several differentialalgebraic models of active memristive circuits. We apply tree-based techniques to the analysis of nodal analysis models and then extend this approach to branch-oriented systems. Some examples illustrate the scope of our results. © 2010 IEEE.

Zanuy C.,Technical University of Madrid
Structural Engineering and Mechanics | Year: 2010

The behaviour of a reinforced concrete tension member is governed by the contribution of concrete between cracks, tension stiffening effect. Under highly repeated loading, this contribution is progressively reduced and the member response approximates that given by the fully cracked member. When focusing on the unloaded state, experiments show deformations larger than those of the naked reinforcement. This has been referred to as negative tension stiffening and is due to the fact that concrete carries compressive stresses along the crack spacing, even thought the tie is subjected to an external tensile force. In this paper a cycle-dependent approach is presented to reproduce the behaviour of the axially loaded tension member, paying attention to the negative tension stiffening contribution. The interaction of cyclic bond degradation and time-dependent effects of concrete is investigated. Finally, some practical diagrams are given to account for the negative tension stiffening effect in reinforced concrete elements. Copyright © 2010 Techno Press.

Jimenez-Fernandez J.,Technical University of Madrid
Ultrasonics | Year: 2012

The acoustic backscatter of encapsulated gas-filled microbubbles immersed in a weak compressible liquid and irradiated by ultrasound fields of moderate to high pressure amplitudes is investigated theoretically. The problem is formulated by considering, for the viscoelastic shell of finite thickness, an isotropic hyperelastic neo-Hookean model for the elastic contribution in addition to a Newtonian viscous component. First and second harmonic scattering cross-sections have been evaluated and the quantitative influence of the driving pressure amplitude on the harmonic resonance frequencies for different initial equilibrium bubble sizes and for different encapsulating physical properties has been determined. Conditions for optimal second harmonic imaging have been also investigated and some regions in the parameters space where the second harmonic intensity is dominant over the fundamental have been identified. Results have been obtained for albumin, lipid and polymer encapsulating shells, respectively. © 2012 Elsevier B.V. All rights reserved.

Higuera F.J.,Technical University of Madrid
Combustion and Flame | Year: 2011

Upward propagation of a premixed flame in a vertical tube filled with a very lean mixture is simulated numerically using a single irreversible Arrhenius reaction model with infinitely high activation energy. In the absence of heat losses and preferential diffusion effects, a curved flame with stationary shape and velocity close to those of an open bubble ascending in the same tube is found for values of the fuel mass fraction above a certain minimum that increases with the radius of the tube, while the numerical computations cease to converge to a stationary solution below this minimum mass fraction. The vortical flow of the gas behind the flame and in its transport region is described for tubes of different radii. It is argued that this flow may become unstable when the fuel mass fraction is decreased, and that this instability, together with the flame stretch due to the strong curvature of the flame tip in narrow tubes, may be responsible for the minimum fuel mass fraction. Radiation losses and a Lewis number of the fuel slightly above unity decrease the final combustion temperature at the flame tip and increase the minimum fuel mass fraction, while a Lewis number slightly below unity has the opposite effect. © 2011 The Combustion Institute.

Riaza R.,Technical University of Madrid
International Journal of Circuit Theory and Applications | Year: 2015

This paper presents a comprehensive taxonomy of so-called second-order memory devices, which include charge-controlled memcapacitors and flux-controlled meminductors, among other novel circuit elements. These devices, which are classified according to their differential and state orders, are necessary to get a complete extension of the family of classical nonlinear circuit elements (resistors, capacitors, and inductors) for all possible controlling variables. Using a fully nonlinear formalism, we obtain nondegeneracy conditions for a broad class of second-order mem-circuits. This class of circuits is expected to yield a rich dynamic behavior; in this regard, we explore certain bifurcation phenomena exhibited by a family of circuits including a charge-controlled memcapacitor and a flux-controlled meminductor, providing some directions for future research. Copyright © 2014 John Wiley & Sons, Ltd.

Masa-Campos J.L.,Autonomous University of Madrid | Sierra-Perez M.,Technical University of Madrid
IEEE Transactions on Antennas and Propagation | Year: 2011

A linearly polarized radial line patch antenna with internal coupling patches is presented. A non-resonant antenna structure has been designed, with a 0.68 lambda;0 radial spacing between element rings. A uniform amplitude and phase feed scheme has been implemented. Therefore, a phase compensation microstrip structure (external to the radial waveguide) has been included for a broadside radiation beam. Likewise, a compensation method has been used to avoid internal reflection problems in the waveguide. An antenna prototype has been built. 28.2 dBi gain and 70% efficiency peak values have been measured at DBS band, with reasonable agreement between simulations and measurements. © 2011 IEEE.

Perez-Martinez P.J.,Technical University of Madrid
Transportation Research Record | Year: 2010

This study analyzes trends in freight transport, energy use, and greenhouse gas emissions in Spain from 1990 to 2007. Freight transport contributes 8.5% of Spain's greenhouse gas emissions. The emissions have experienced a 68% increase from 1990, which is 53% above the level that Spain committed to under the Kyoto Protocol; road freight made up most of the increase. Energy use will continue to grow unless there are important reductions in the energy intensities of road freight and a change in the modal share. On the basis of the most likely development of these factors, emissions will rise an additional 53% by 2025 and thereby push the sector 167% above the 1990 base year values. Emissions could be reduced 3.3% by 2025 compared with the 2007 level if the average performance of road diesel vehicles in 2025 shows a 55% increase in efficiency.

Curatti L.,CONICET | Rubio L.M.,Technical University of Madrid
Plant Science | Year: 2014

Some regions of the developing world suffer low cereal production yields due to low fertilizer inputs, among other factors. Biological N2 fixation, catalyzed by the prokaryotic enzyme nitrogenase, is an alternative to the use of synthetic N fertilizers. The molybdenum nitrogenase is an O2-labile metalloenzyme composed of the NifDK and NifH proteins, which biosyntheses require a number of nif gene products. A challenging strategy to increase cereal crop productivity in a scenario of low N fertilization is the direct transfer of nif genes into cereals. The sensitivity of nitrogenase to O2 and the apparent complexity of nitrogenase biosynthesis are the main barriers identified so far. Expression of active NifH requires the products of nifM, nifH, and possibly nifU and nifS, whereas active NifDK requires the products of nifH, nifD, nifK, nifB, nifE, nifN, and possibly nifU, nifS, nifQ, nifV, nafY, nifW and nifZ. Plastids and mitochondria are potential subcellular locations for nitrogenase. Both could provide the ATP and electrons required for nitrogenase to function but they differ in their internal O2 levels and their ability to incorporate ammonium into amino acids. © 2014 Elsevier Ireland Ltd.

Temporal M.,Technical University of Madrid | Canaud B.,CEA DAM Ile-de-France
European Physical Journal D | Year: 2011

Illumination uniformity of a spherical capsule directly driven by laser beams has been assessed numerically. Laser facilities characterized by N D = 12, 20, 24, 32, 48 and 60 directions of irradiation with associated a single laser beam or a bundle of N B laser beams have been considered. The laser beam intensity profile is assumed super-Gaussian and the calculations take into account beam imperfections as power imbalance and pointing errors. The optimum laser intensity profile, which minimizes the root-mean-square deviation of the capsule illumination, depends on the values of the beam imperfections. Assuming that the N B beams are statistically independents is found that they provide a stochastic homogenization of the laser intensity associated to the whole bundle, reducing the errors associated to the whole bundle by the factor 1/N B 1/2, which in turn improves the illumination uniformity of the capsule. Moreover, it is found that the uniformity of the irradiation is almost the same for all facilities and only depends on the total number of laser beams N tot = N D × N B. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Alfonso-Faus A.,Technical University of Madrid
Astrophysics and Space Science | Year: 2012

Using the relation proposed by Weinberg in 1972, combining quantum and cosmological parameters, we prove that the self gravitational potential energy of any fundamental particle is a quantum, with physical properties independent of the mass of the particle. It is a universal quantum of gravitational energy, and its physical properties depend only on the cosmological scale factor R and the physical constants h and c. We propose a modification of the Weinberg's relation, keeping the same numerical value, but substituting the cosmological parameter H/c by 1/R. © 2011 Springer Science+Business Media B.V.

Bermudez A.,University of Santiago de Compostela | Ferrin J.L.,University of Santiago de Compostela | Linan A.,Technical University of Madrid | Saavedra L.,University of Santiago de Compostela
Combustion and Flame | Year: 2011

A mathematical model for the group combustion of pulverized coal particles was developed in a previous work. It includes the Lagrangian description of the dehumidification, devolatilization and char gasification reactions of the coal particles in the homogenized gaseous environment resulting from the three fuels, CO, H 2 and volatiles, supplied by the gasification of the particles and their simultaneous group combustion by the gas phase oxidation reactions, which are considered to be very fast. This model is complemented here with an analysis of the particle dynamics, determined principally by the effects of aerodynamic drag and gravity, and its dispersion based on a stochastic model. It is also extended to include two other simpler models for the gasification of the particles: the first one for particles small enough to extinguish the surrounding diffusion flames, and a second one for particles with small ash content when the porous shell of ashes remaining after gasification of the char, non structurally stable, is disrupted.As an example of the applicability of the models, they are used in the numerical simulation of an experiment of a non-swirling pulverized coal jet with a nearly stagnant air at ambient temperature, with an initial region of interaction with a small annular methane flame. Computational algorithms for solving the different stages undergone by a coal particle during its combustion are proposed. For the partial differential equations modeling the gas phase, a second order finite element method combined with a semi-Lagrangian characteristics method are used. The results obtained with the three versions of the model are compared among them and show how the first of the simpler models fits better the experimental results. © 2011 The Combustion Institute.

Pirulli M.,Polytechnic University of Turin | Pastor M.,Technical University of Madrid
Geotechnique | Year: 2012

The entrainment of channel-path material plays an important role during runout of many rapid landslides. Such a mechanism is able to change the mobility of a flow significantly, through rapid changes of the flow volume and rheology. The purpose of this paper is to use mathematical, rheological and constitutive models to analyse the entrainment effect on runout analysis results. After a brief review and classification of some well-established erosion laws, a simple, yet effective, empirical formula for the entrainment rate has been selected, and is implemented in a continuum mechanics-based numerical model. First, some hypothetical examples are used to test the effectiveness of the implemented entrainment process, and to evidence the respective role of entrainment and topography on a flow propagation. Then a back-analysis is presented of the 2000 Tsing Shan event (Hong Kong), where a small volume of 150 m3 of material grew to 1620 m3 because of the strong erosion along the slope. From the results obtained, it emerges that the new model with erosion implemented can provide a useful contribution in describing the consequences of mass movements in which the entrainment process can play a key role.

Warren C.R.,University of Sydney | Aranda I.,Instituto Nacional Of Investigacion Y Tecnologia Agraria Y Alimentaria Inia | Cano F.J.,Instituto Nacional Of Investigacion Y Tecnologia Agraria Y Alimentaria Inia | Cano F.J.,Technical University of Madrid
Metabolomics | Year: 2012

Past studies of water stress in Eucalyptus spp. generally highlighted the role of fewer than five "important" metabolites, whereas recent metabolomic studies on other genera have shown tens of compounds are affected. There are currently no metabolite profiling data for responses of stress-tolerant species to water stress. We used GC-MS metabolite profiling to examine the response of leaf metabolites to a long (2 month) and severe (Ψ predawn < -2 MPa) water stress in two species of the perennial tree genus Eucalyptus (the mesic Eucalyptus pauciflora and the semi-arid Eucalyptus dumosa). Polar metabolites in leaves were analysed by GC-MS and inorganic ions by capillary electrophoresis. Pressure-volume curves and metabolite measurements showed that water stress led to more negative osmotic potential and increased total osmotically active solutes in leaves of both species. Water stress affected around 30-40% of measured metabolites in E. dumosa and 10-15% in E. pauciflora. There were many metabolites that were affected in E. dumosa but not E. pauciflora, and some that had opposite responses in the two species. For example, in E. dumosa there were increases in five acyclic sugar alcohols and four lowabundance carbohydrates that were unaffected by water stress in E. pauciflora. Re-watering increased osmotic potential and decreased total osmotically active solutes in E. pauciflora, whereas in E. dumosa re-watering led to further decreases in osmotic potential and increases in total osmotically active solutes. This experiment has added several extra dimensions to previous targeted analyses of water stress responses in Eucalyptus, and highlights that even species that are closely related (e. g. congeners) may respond differently to water stress and re-watering. © 2011 Springer Science+Business Media, LLC.

Wisniacki D.A.,FCEyN | Ares N.,FCEyN | Vergini E.G.,Comision Nacional de la Energia Atomica | Vergini E.G.,Technical University of Madrid
Physical Review Letters | Year: 2010

The prediction of the response of a closed system to external perturbations is one of the central problems in quantum mechanics, and in this respect, the local density of states (LDOS) provides an in-depth description of such a response. The LDOS is the distribution of the overlaps squared connecting the set of eigenfunctions with the perturbed one. Here, we show that in the case of closed systems with classically chaotic dynamics, the LDOS is a Breit-Wigner distribution under very general perturbations of arbitrary high intensity. Consequently, we derive a semiclassical expression for the width of the LDOS which is shown to be very accurate for paradigmatic systems of quantum chaos. This Letter demonstrates the universal response of quantum systems with classically chaotic dynamics. © 2010 The American Physical Society.

Iriarte G.F.,Technical University of Madrid
Current Applied Physics | Year: 2011

Growth of single crystal nickel-silicide (NiSix) nanowires has been achieved on inert amorphous SiO2 and Si3N4 substrates covered with nanometer-size Ni particles. The CVD method was used to grow the nanowires by decomposition of silane at temperatures fully compatible with standard IC processing. Nanometer-size Ni particles were obtained by dissociation of a continuous 10 nm Ni film thin by an RTP (Rapid Thermal Process) step. Scanning Electron Microscopy (SEM) as well as Energy Backscattering Electron Diffraction (EBSD) techniques were used to characterize the as-synthesized nanowires. High-resolution transmission electron microscopy (HR-TEM) results show that the wires are monocrystalline with a separation of the lattice planes corresponding to Si or NiSix (the lattice mismatch between this two materials is only 0.4%). Finally, Energy Filtered Transmission Electron Microscopy (EF-TEM) analysis was used to determine that the composition of the grown nanowires was indeed NiSix. Our HR-TEM analysis also revealed that the silicide nanowires do not all grow in a specific growth direction but that several growth directions such as 111 or 110 are possible. © 2010 Elsevier B.V. All rights reserved.

Prieto J.L.,Technical University of Madrid | Munoz M.,CSIC - Institute of Applied Physics | Martinez E.,University of Salamanca
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The process of injection of a magnetic domain wall (DW) by means of a 25-100 ns current pulse flowing through an adjacent conductive track has been studied in detail. We find that the probability of creating a DW through this method is 100% for a wide range of amplitudes of the current pulse and of the external magnetic field, including zero external magnetic field. Micromagnetic simulations show that the DW is created in the first nanosecond of the pulse, and its movement is strongly influenced by the induced Oersted field, which can reach considerable values, especially in the perpendicular-to-plane direction. The edge roughness and temperature play also a crucial role in determining the type of DW that travels through the wire. Experimentally we show that a map of the probability of injection of a DW by a current pulse can be a very powerful method to check the structural quality of the nanostripe, which has very important practical consequences for research in this area. © 2011 American Physical Society.

Baudrit M.,French National Solar Energy Institute | Algora C.,Technical University of Madrid
IEEE Transactions on Electron Devices | Year: 2010

Multijunction solar cells (MJCs) based on IIIV semiconductors constitute the state-of-the-art approach for high-efficiency solar energy conversion. These devices, consisting of a stack of various solar cells, are interconnected by tunnel diodes. Reliable simulations of the tunnel diode behavior are still a challenge for solar cell applications. In this paper, a complete description of the model implemented in Silvaco ATLAS is shown, demonstrating the importance of local and nonlocal trap-assisted tunneling. We also explain how the measured doping profile and the metalization-induced series resistance influence the behavior of the tunnel diodes. Finally, we detail the different components of the series resistance and show that this can help extract the experimental voltage drop experienced by an MJC due to the tunnel junction. The value of this intrinsic voltage is important for achieving high efficiencies at concentrations near 1000 suns. © 2006 IEEE.

Higuera F.J.,Technical University of Madrid
Journal of Fluid Mechanics | Year: 2011

This paper presents an analysis of the transport of electric current in a jet of an electrically conducting liquid discharging from a metallic tube into a gas or a vacuum, and subject to an electric field due to a high voltage applied between the tube and a far electrode. The flow, the surface charge and the electric field are computed in the current transfer region of the jet, where conduction current in the liquid becomes surface current due to the convection of electric charge accumulated at its surface. The electric current computed as a function of the flow rate of the liquid injected through the tube increases first as the square root of this flow rate, levels to a nearly constant value when the flow rate is increased and finally sets to a linear increase when the flow rate is further increased. The current increases linearly with the applied voltage at small and moderate values of this variable, and faster than linearly at high voltages. The characteristic length and structure of the current transfer region are determined. Order-of-magnitude estimates for jets which are only weakly stretched by the electric stresses are worked out that qualitatively account for some of the numerical results. © 2011 Cambridge University Press.

Castro M.,Technical University of Madrid
Computer Applications in Engineering Education | Year: 2012

Traditionally, practical training of students in highway design has been based on solving geometric problems without using professional highway design software. In a degree of the Technical University of Madrid (UPM), teaching of this subject has been redesigned using a project-based learning approach. Along the course, the students make a complete project of a highway using professional software and procedures. The highway design software chosen includes a simulator that makes a virtual journey along the highway from the point of view of a driver traveling on it. A detailed description of the course program and the software used is provided. © 2010 Wiley Periodicals, Inc.

Toro M.A.,Technical University of Madrid | Garcia-Cortes L.A.,Instituto Nacional Of Investigacian Agraria | Legarra A.,French National Institute for Agricultural Research
Genetics Selection Evolution | Year: 2011

Background: Genetic relatedness or similarity between individuals is a key concept in population, quantitative and conservation genetics. When the pedigree of a population is available and assuming a founder population from which the genealogical records start, genetic relatedness between individuals can be estimated by the coancestry coefficient. If pedigree data is lacking or incomplete, estimation of the genetic similarity between individuals relies on molecular markers, using either molecular coancestry or molecular covariance. Some relationships between genealogical and molecular coancestries and covariances have already been described in the literature. Methods. We show how the expected values of the empirical measures of similarity based on molecular marker data are functions of the genealogical coancestry. From these formulas, it is easy to derive estimators of genealogical coancestry from molecular data. We include variation of allelic frequencies in the estimators. Results: The estimators are illustrated with simulated examples and with a real dataset from dairy cattle. In general, estimators are accurate and only slightly biased. From the real data set, estimators based on covariances are more compatible with genealogical coancestries than those based on molecular coancestries. A frequently used estimator based on the average of estimated coancestries produced inflated coancestries and numerical instability. The consequences of unknown gene frequencies in the founder population are briefly discussed, along with alternatives to overcome this limitation. Conclusions: Estimators of genealogical coancestry based on molecular data are easy to derive. Estimators based on molecular covariance are more accurate than those based on identity by state. A correction considering the random distribution of allelic frequencies improves accuracy of these estimators, especially for populations with very strong drift. © 2011 Toro et al; licensee BioMed Central Ltd.

Benavides E.M.,Technical University of Madrid
International Journal of Turbo and Jet Engines | Year: 2011

Recently, an analytical model to calculate the stability of an axial-flow compressor rotor has been presented in the scientific literature. The range of validity of that theoretical characterization was supported by several lemmas and theorems. One of the main results was the definition of a dimensionless coefficient for determining the location of the stability line in the rotor map. In this work the mathematical structure of that solution is studied. As a result of this detailed study, a new stability theorem and a new stability coefficient are obtained. This stability coefficient is an improvement of the previous one since it is physically and mathematically well defined in all the operational points of the compressor map. As a consequence, the new model is able to capture the stall inception for rotors and stators as well as the full characteristic curve (pressure rise versus mass flow rate) including rotating stall and possibly reverse flow. It is proved, as a consequence of the restriction imposed by the Stability Theorem, that each local component (rotor or stator) has its own instability point and its own post-stall characteristic curve. This theoretical criterion for predicting the averaged characteristic curve is in good accord with the experimental data. The stability coefficient is also verified for a compressor stage. Finally, the model is shown to provide an adequate quantitative and qualitative description of the averaged stall line giving a physical explanation of the mechanism involved in the instable region of the compressor map. Copyright © 2011 De Gruyter.

Tablero C.,Technical University of Madrid
Journal of Physical Chemistry C | Year: 2015

Ternary Cu(Sb,Bi)S2 semiconductors are a group of materials with a wide variety of applications, especially photovoltaic. An analysis of the structural, electronic, and optical properties obtained from first-principles is presented. The microscopic justification of the high absorption coefficients is carried out by splitting the optical properties on chemical species contributions according to the symmetry. Focusing on photovoltaic applications, and from first-principles results, the efficiencies for several solar spectra are obtained as a function of the device thickness. This study indicates the great potential of these materials for photovoltaic and other optical devices. © 2015 American Chemical Society.

De Sande J.C.G.,Technical University of Madrid
International Journal of Engineering Education | Year: 2011

A computer-based training tool has been developed for the Signals and Systems undergraduate course for students. It consists of an automatic problem generator and an automatic self-assessment system that can be used by the students as many times as they want. The students use the tool to generate a numerical variation of a problem, solve it, and use the tool again to answer a series of questions that are automatically assessed. The proposed problem comprises the continuoustime- domain characterization of a linear and time invariant system and its Fourier and Laplace domain analysis. The tool was used during the academic year 2009/2010 by a group of 19 students, and their grades in a final exam were compared with those of a similar group of 17 students who did not use the tool. On a 0-10 scale, the mean and standard deviation of the grades of students who used the tool were 6.5 and 1.8, respectively, whereas the mean and standard deviation of the grades of the student who did not use this tool were 5.1 and 2.6, respectively. The analysis of variance of both sets of marks yields to a p = 0.05 value. The tool can also be used by the teacher as a computer-based assessment system. © 2011 TEMPUS Publications.

Badea-Romero A.,Technical University of Madrid | Lenard J.,Loughborough University
Accident Analysis and Prevention | Year: 2013

The potential effectiveness of vehicle-based secondary safety systems for the protection of pedestrians and pedal cyclists is related to the proportion of cases where injury arises by contact with the road or ground rather than with the striking vehicle. A detailed case review of 205 accidents from the UK On-the-Spot study involving vulnerable road users with head injuries or impacts indicated that contact with the road was responsible in 110 cases. The vehicle however was associated with a majority of more serious casualties: 31 (vehicle) compared with 26 (road) at AIS 2+ head injury level and 20 (vehicle) compared with 13 (road) at AIS 3+ level. Further analysis using a multivariate classification model identified several factors that correlated with the source of injury, namely the type of interaction between the striking vehicle and vulnerable road user, the age of the vulnerable road user and the nature of injury. © 2012 Elsevier Ltd.

San Segundo P.,Technical University of Madrid
Journal of Global Optimization | Year: 2011

This paper presents a set of new decision rules for exact search in N-Queens. Apart from new tiebreaking strategies for value and variable ordering, we introduce the notion of 'free diagonal' for decision taking at each step of the search. With the proposed new decision heuristic the number of subproblems needed to enumerate the first K solutions (typically K = 1, 10 and 100) is greatly reduced w.r.t. other algorithms and constitutes empirical evidence that the average solution density (or its inverse, the number of subproblems per solution) remains constant independent of N. Specifically finding a valid configuration was backtrack free in 994 cases out of 1,000, an almost perfect decision ratio. This research is part of a bigger project which aims at deriving new decision rules for CSP domains by evaluating, at each step, a constraint value graph G c . N-Queens has adapted well to this strategy: domain independent rules are inferred directly from G c whereas domain dependent knowledge is represented by an induced hypergraph over G c and computed by similar domain independent techniques. Prior work on the Number Place problem also yielded similar encouraging results. © 2011 Springer Science+Business Media, LLC.

Sanchez-Torr A.,Technical University of Madrid
IEEE Transactions on Plasma Science | Year: 2015

An electrostatic tether could be a recent technology application for removing energetic particles in the earth's radiation belts. Both hollow cathode and high-voltage source will keep the conductive tether at high positive/negative bias. An effective Coulomb deflection of the particles into the loss cone will produce a high rate of atmospheric penetration, decreasing the amount of high-energy particles in the radiation belts. This paper focuses on the high positive-bias case with a sheath that is correctly modeled. For small radius and extremely high bias, the tether does collect the relativistic orbital motion limited current. Relativistic effects modify both potential and density profiles, decreasing the range of the sheath and, in turn, increasing tether current collection. The remediation time will increase if relativistic effects are considered. A remediation time of about six years is determined for 100 1-MV tethers moving in a circular equatorial orbit at an altitude of about 2000 km. In addition, the presence of both Coulomb and Lorentz forces may induce thrust or drag on the tether. Both forces are briefly studied with plasma condition characteristic of the inner radiation belt. © 2015 IEEE.

Sanchez-Torres A.,Technical University of Madrid
IEEE Transactions on Plasma Science | Year: 2015

An electric solar sail (E-sail) is a recent propellantless propulsion concept for a direct exploration of the solar system. An E-sail consists of an array of bare, conductive tethers at very high positive/negative bias, prone to extract solar-wind momentum by Coulomb deflection of protons. This paper focuses on the positive-bias case with a thick sheath that must be correctly modeled. Ion scattering within the sheath and the resulting thrust are determined. Use of E-sail for outer planet missions would reduce the time of flight; a 2-ton spacecraft might reach Jupiter in less than two years. © 2015 IEEE.

Iriarte G.F.,Technical University of Madrid
Journal of Nanoparticle Research | Year: 2011

Artificial nanostructures (Samuelson et al., Physica E 21:560-567, 2004; Xia et al., Adv Mater 15:353-389, 2003) show promise for the organization of functional materials (Huck and Samuelson, Nanotechnology 14:NIL-5-NIL-8, 2003) to create nanoelectronic (Mizuta and Oda, Science 279:208-211, 2008) or nano-optical devices (Mazur et al.; Tanemura et al., Synthesis, Optical Properties and Functional Applications of ZnO Nano-materials: A Review, 1-3:58-63, 2008). However, in most manufacturing recipes described so far, nanostructures are synthesized in solution and/or uncontrolled deposition results in random arrangements; this makes it difficult to measure the properties of attached nanodevices or to integrate them with conventionally fabricated microcircuitry. Here, we describe a fully CMOS compatible process technology for mass manufacture of polysilicon nanowires by the CVD (chemical vapor deposition) method. The large scale production of nanowires could successfully be synthesized on silicon (100) substrates. However, the method presented here can successfully be employed with all technologically useful substrates with good adhesion for silicon such as SiO2, diamond-like carbon or III-V semiconductors. This opens up the possibility for the fabrication of strain-sensitive and defect-sensitive optoelectronic devices on the optimum III-V substrate (Fonstad et al.). Finally, scanning electron microscopy (SEM) was used to characterize the as-synthesized nanowires and energy-filtered transmission electron microscopy (EFTEM) and scanning transmission electron microscopy (STEM) analysis were used to determine the nanowire composition. © 2010 Springer Science+Business Media B.V.

Fang S.-E.,Fuzhou University | Perera R.,Technical University of Madrid
Mechanical Systems and Signal Processing | Year: 2011

Statistical tools, as well as mathematical ones, have been widely adopted and their performance has been shown in different engineering problems where randomicity usually exists. In the realm of engineering, merging statistical analysis into structural evaluation and assessment will be a tendency in the future. As a combination of mathematical and statistical techniques, response surface methodology has been successfully applied to design optimization, response prediction and model validation. This methodology provides explicit functions to represent the relationships between the inputs and outputs of a physical system, which is also a desirable advantage in damage identification. However, so far little research has been carried out in applying the response surface methodology to structural damage identification. This paper presents a damage identification method achieved by response surface based model updating using D-optimal designs. Compared with some common designs constructing response surfaces, D-optimal designs generally require a minimum number of numerical samples and this merit is quite desirable when analysts cannot obtain enough samples. In this study, firstly D-optimal designs are used to establish response surface models for screening out non-significant updating parameters and then first-order response surface models are constructed to substitute for finite element models in predicting the dynamic responses of an intact or damaged physical system. Three case studies of a numerical beam, a tested reinforced concrete frame and a tested full-scale bridge have been used to verify the proposed method. Physical properties such as Young's modulus and section inertias were chosen as the input features and modal frequency was the only response feature. It has been observed that the proposed method gives enough accuracy in damage prediction of not only the numerical but also the real-world structures with single and multiple damage scenarios, and the first-order response surface models based on the D-optimal criterion are adequate for such damage identification purposes. © 2010 Elsevier Ltd.All rights reserved.

Haemmerle R.,Technical University of Madrid
Theory and Practice of Logic Programming | Year: 2011

In this paper, we address the problem of defining a fixpoint semantics for Constraint Handling Rules (CHR) that captures the behavior of both simplification and propagation rules in a sound and complete way with respect to their declarative semantics. Firstly, we show that the logical reading of states with respect to a set of simplification rules can be characterized by a least fixpoint over the transition system generated by the abstract operational semantics of CHR. Similarly, we demonstrate that the logical reading of states with respect to a set of propagation rules can be characterized by the greatest fixpoint. Then, in order to take advantage of both types of rules without losing fixpoint characterization, we present a new operational semantics with persistent constraints. We finally establish that this semantics can be characterized by two nested fixpoints, and we show that the resulting language is an elegant framework to program using coinductive reasoning. © 2011 Cambridge University Press.

Vazquez Espi M.,Technical University of Madrid
Structural and Multidisciplinary Optimization | Year: 2013

A recent study by Rozvany and Sokół (Struct Multidisc Optim, 2012) discussed an important topic in structural design: the allowance for support costs in layout optimization. Herein a frequently used kind of support will be examined, that of simple foundation with horizontal reaction by friction. This support does not seem to be covered by Authors' approach. To illustrate this case some solutions obtained by standard design rules are included. © 2012 Springer-Verlag Berlin Heidelberg.

Alvarez M.A.,Technological University of Pereira | Luengo D.,Technical University of Madrid | Lawrence N.D.,University of Sheffield | Lawrence N.D.,Sheffield Institute for Translational Neuroscience
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2013

Purely data-driven approaches for machine learning present difficulties when data are scarce relative to the complexity of the model or when the model is forced to extrapolate. On the other hand, purely mechanistic approaches need to identify and specify all the interactions in the problem at hand (which may not be feasible) and still leave the issue of how to parameterize the system. In this paper, we present a hybrid approach using Gaussian processes and differential equations to combine data-driven modeling with a physical model of the system. We show how different, physically inspired, kernel functions can be developed through sensible, simple, mechanistic assumptions about the underlying system. The versatility of our approach is illustrated with three case studies from motion capture, computational biology, and geostatistics. © 1979-2012 IEEE.

Tablero C.,Technical University of Madrid
Journal of Applied Physics | Year: 2012

The cadmium thioindate spinel CdIn2S4 semiconductor has potential applications for optoelectronic devices. We present a theoretical study of the structural and optoelectronic properties of the host and of the Cr-doped ternary spinel. For the host spinel, we analyze the direct or indirect character of the energy bandgap, the change of the energy bandgap with the anion displacement parameter and with the site cation distribution, and the optical properties. The main effect of the Cr doping is the creation of an intermediate band within the energy bandgap. The character and the occupation of this band are analyzed for two substitutions: Cr by In and Cr by Cd. This band permits more channels for the photon absorption. The optical properties are obtained and analyzed. The absorption coefficients are decomposed into contributions from the different absorption channels and from the inter- and intra-atomic components. © 2012 American Institute of Physics.

Escobar D.,Technical University of Madrid | Ahedo E.,Charles III University of Madrid
IEEE Transactions on Plasma Science | Year: 2015

A linearized time-dependent 2-D (axial and azimuthal) fluid model of the Hall thruster discharge is presented. This model is used to carry out a global stability analysis of the plasma response, as opposed to the more common local stability analyses. Experimental results indicate the existence of low-frequency long-wave-length azimuthal oscillations in the direction of the E $\times $ B drift, usually referred to as spokes. The present model predicts the presence of such oscillations for typical Hall thruster conditions with a frequency and a growth rate similar to those found in experiments. Moreover, the comparison between the simulated spoke and the simulated breathing mode, a purely axial low-frequency oscillation typical in Hall thrusters, shows similar features in them. Additionally, the contribution of this azimuthal oscillation to electron conductivity is evaluated tentatively by computing the equivalent anomalous diffusion coefficient from the linear oscillations. The results show a possible contribution to anomalous diffusion in the rear part of the thruster. © 1973-2012 IEEE.

Villagra J.,Technical University of Madrid | d'Andrea-Novel B.,MINES ParisTech | Fliess M.,French Institute for Research in Computer Science and Automation | Mounier H.,University Paris - Sud
Control Engineering Practice | Year: 2011

A new approach to estimate vehicle tire forces and road maximum adherence is presented. Contrarily to most of the previous works on this subject, it is not an asymptotic observer-based estimation, but a combination of elementary diagnosis tools and new algebraic techniques for filtering and estimating derivatives of noisy signals. In a first step, instantaneous friction and lateral forces will be computed within this framework. Then, extended braking stiffness concept is exploited to detect which braking efforts allow to distinguish a road type from another. A weighted Dugoff model is used during these 'distinguishable' intervals to estimate the maximum friction coefficient. Very promising results have been obtained in noisy simulations and real experimentations for most of the driving situations. © 2010 Elsevier Ltd.

Caro E.,Technical University of Madrid
Electric Power Systems Research | Year: 2016

The state estimation (SE) in an electric power system is subject to uncertainty, due to random measurement errors, inaccurate line parameters, etc. Specifically, the location of the reference bus may influence over the accuracy of some estimated states. This paper analyzes this effect and proposes an algorithm to select the reference bus, pursuing maximum overall accuracy. Two realistic case studies are analyzed and conclusions duly drawn. © 2016 Elsevier B.V. All rights reserved.

Baeza A.,CIBER ISCIII | Guisasola E.,Complutense University of Madrid | Guisasola E.,Technical University of Madrid | Ruiz-Hernandez E.,CIBER ISCIII | And 2 more authors.
Chemistry of Materials | Year: 2012

The treatment of complex diseases such as cancer pathologies requires the simultaneously administration of several drugs in order to improve the effectiveness of the therapy and overwhelm the defensive mechanisms of tumor cells, responsible of the apparition of multidrug resistance (MDR). In this manuscript, a novel nanodevice able to perform remotely controlled release of small molecules and proteins in response to an alternating magnetic field has been presented. This device is based on mesoporous silica nanoparticles with iron oxide nanocrystals encapsulated inside the silica matrix and decorated on the surface with a thermoresponsive copolymer of poly(ethyleneimine)-b-poly(N- isopropylacrylamide) (PEI/NIPAM). The polymer structure has been designed with a double purpose, to act as temperature-responsive gatekeeper for the drugs trapped inside the silica matrix and, on the other hand, to retain proteins into the polymer shell by electrostatic or hydrogen bonds interactions. The nanocarrier traps the different cargos at low temperatures (20 °C) and releases the retained molecules when the temperature exceeds 35-40 °C following different kinetics. The ability to remotely trigger the release of different therapeutic agents in a controlled manner in response to a nontoxic and highly penetrating external stimulus as alternating magnetic field, along with the synergic effect associated to hyperthermia and chemotherapy, and the possibility to use this nanocarrier as contrast agent in magnetic resonance imagining (MRI) convert this nanodevice in an excellent promising candidate for further studies for oncology therapy. © 2012 American Chemical Society.

Romero I.,Technical University of Madrid
Computational Mechanics | Year: 2012

The energy-momentum method, a space-time discretization strategy for elastic problems in nonlinear solid, structural, and multibody mechanics relies critically on a discrete derivative operation that defines an approximation of the internal forces that guarantees the discrete conservation of energy and momenta. In the case of nonlinear elastodynamics, the formulation for general hyperelastic materials is due to Simo and Gonzalez, dating back to the mid-nineties. In this work we show that there are actually infinite second order energy-momentum methods for elastodynamics, all of them deriving from a modified midpoint integrator by an appropriate redefinition of the stress tensor at equilibrium. Such stress tensors can be interpreted as the solutions to local convex projections, whose precise definitions lead to different methods. The mathematical requirements of such projections are identified. Based on this geometrical interpretation several conserving methods are examined.

Connor D.J.,University of Melbourne | Minguez M.I.,Technical University of Madrid
Global Food Security | Year: 2012

The challenge to properly feed a world population of 9.2 billion by 2050, that must be achieved on essentially currently cropped area, requires that food production be increased by 70%. This large increase can only be achieved by combinations of greater crop yields and more intensive cropping adapted to local conditions and availability of inputs. Farming systems are dynamic and continuously adapt to changing ecological, environmental and social conditions, while achieving greater production and resource-use efficiency by application of science and technology. This article argues that the solution to feed and green the world in 2050 is to support this evolution more strongly by providing farmers with necessary information, inputs, and recognition. There is no revolutionary alternative. Proposals to transform agriculture to low-input and organic systems would, because of low productivity, exacerbate the challenge if applied in small part, and ensure failure if applied more widely. The challenge is, however, great. Irrigation, necessary to increase cropping intensity in many areas cannot be extended much more widely than at present, and it is uncertain if the current rate of crop yield increase can be maintained. Society needs greater recognition of the food-supply problem and must increase funding and support for agricultural research while it attends to issues of food waste and overconsumption that can make valuable reductions to food demand from agriculture. © 2012 Elsevier B.V.

A numerical model of a dilute spray of electrically charged liquid droplets vaporizing in a hot gas is formulated based on a Eulerian description of the gas and Lagrangian tracking of the droplets. The model is used to simulate the dispersion and vaporization of a spray in a cylindrical chamber where the droplets are axially injected with a coflow of hot gas. The effects of the initial size of the droplets and of the gas-to-liquid mass flux and inlet temperature ratios are analyzed, and the conditions under which the droplets fully vaporize in the chamber without impacting on its walls are determined. The ranges of operation where these requirements are met widen when the flow rate of liquid is split into a number of sources and injected through different orifices, which also improves the uniformity of the temperature and vapor mass fraction distributions at the outlet of the chamber. The effects of satellite droplets and of an applied electric field that pushes the charged droplets in the direction in which they are injected are considered. © 2015 Elsevier Ltd.

DeFelipe J.,Technical University of Madrid
Science | Year: 2010

A major challenge in neuroscience is to decipher the structural layout of the brain. The term "connectome" has recently been proposed to refer to the highly organized connection matrix of the human brain. However, defining how information flows through such a complex system represents so difficult a task that it seems unlikely it could be achieved in the near future or, for the most pessimistic, perhaps ever. Circuit diagrams of the nervous system can be considered at different levels, although they are surely impossible to complete at the synaptic level. Nevertheless, advances in our capacity to marry macro- and microscopic data may help establish a realistic statistical model that could describe connectivity at the ultrastructural level, the "synaptome," giving us cause for optimism.

Barrero-Gil A.,Technical University of Madrid
Computers and Fluids | Year: 2012

In this communication we present a simple modification of the method of fundamental solutions applied to Stokes problems, which allows to make coincident the source and collocation points. It is based on a special treatment of the singular kernel evaluations, where spatially averaged quantities are considered by using auxiliary (or fictitious) Stokeslets. The method is still truly meshless and easy to implement. © 2012 Elsevier Ltd.

Cuadrado F.,Queen Mary, University of London | Duenas J.,Technical University of Madrid
IEEE Communications Magazine | Year: 2012

The mobile user experience has been significantly altered with the arrival of mobile broadband widespread deployments, massive improvements in available smartphones, and a shift in user habits toward a more participative, communicative role. In this context, mobile application stores have revolutionized software and content delivery. These stores focus on the applications, building around them an ecosystem of developers and consumers. The store greatly lessens the barrier between these agents, providing significant benefits to both developers and consumers. In this article we analyze this phenomenon, describing its originating factors and fundamental characteristics. We also perform a more detailed study on the two most successful application stores, identifying different approaches to implementing the model. © 2012 IEEE.

Fang S.-E.,Fuzhou University | Ren W.-X.,Hefei University of Technology | Perera R.,Technical University of Madrid
Mechanical Systems and Signal Processing | Year: 2012

Stochastic model updating must be considered for quantifying uncertainties inherently existing in real-world engineering structures. By this means the statistical properties, instead of deterministic values, of structural parameters can be sought indicating the parameter variability. However, the implementation of stochastic model updating is much more complicated than that of deterministic methods particularly in the aspects of theoretical complexity and low computational efficiency. This study attempts to propose a simple and cost-efficient method by decomposing a stochastic updating process into a series of deterministic ones with the aid of response surface models and Monte Carlo simulation. The response surface models are used as surrogates for original FE models in the interest of programming simplification, fast response computation and easy inverse optimization. Monte Carlo simulation is adopted for generating samples from the assumed or measured probability distributions of responses. Each sample corresponds to an individual deterministic inverse process predicting the deterministic values of parameters. Then the parameter means and variances can be statistically estimated based on all the parameter predictions by running all the samples. Meanwhile, the analysis of variance approach is employed for the evaluation of parameter variability significance. The proposed method has been demonstrated firstly on a numerical beam and then a set of nominally identical steel plates tested in the laboratory. It is found that compared with the existing stochastic model updating methods, the proposed method presents similar accuracy while its primary merits consist in its simple implementation and cost efficiency in response computation and inverse optimization. © 2012 Elsevier Ltd.

Benavides E.M.,Technical University of Madrid
IEEE Transactions on Reliability | Year: 2011

We propose a reliability model for describing the lifetime of devices and materials working under variable stress (i.e., stresses which are a function of time). The model is based on a two-parameter Weibull distribution obtained by retaining the leading term from a series expansion of a general cumulative hazard function. The scale parameter is related to the real-stress time evolution by means of a differential equation which can be integrated. The paper shows that the solution of this differential equation approaches a well defined asymptotic behavior when the time approaches infinity. The proposed model may include the physics involved in the failure criterion, and hence it can be consistent with accelerated life, step-stress, and variable-stress tests. This important property is illustrated by using the proposed reliability model to build statistical distributions for the lifetime of aluminum-alloy electrical wire connections, and thin film cracking in plastic integrated circuits which are stressed by temperature cycling, and thermal shock testing. A final discussion studies how the model allows extending the applicability, for example, by including time and stress thresholds in the failure criterion. © 2010 IEEE.

Perez P.,Alcatel - Lucent | Garcia N.,Technical University of Madrid
IEEE Transactions on Consumer Electronics | Year: 2011

In this paper, we analyze the effect of packet losses in multimedia sequences and propose a priority model for the packets, where the highest priorities are given to the packets whose loss has stronger effect in the perceived Quality of Experience (QoE). The proposed model assigns priorities to each of the media packets based on the audiovisual coding structure: type of frame, position of the packet within the frame and position of the frame within the GOP. This model can be used as a basis for Unequal Error Protection (UEP) strategies where, from a window of consecutive packets, only a fraction of them are protected and the others may potentially get lost. The experiments conducted show that this strategy strongly reduces the Mean Square Error (MSE) of the received sequence compared to the situation where the same ratio of packet losses is produced randomly. The strategy provides a good MSE gain even when the bit budget assigned to encode the priority of each packet is small. The prioritization model and the priority label signalization are fully compatible with current standards for multimedia distribution, and therefore they can be immediately applied to existing multimedia delivery services, such as IPTV platforms. © 2006 IEEE.

Bailador G.,Technical University of Madrid | Trivino G.,European Center for Soft Computing
Fuzzy Sets and Systems | Year: 2010

In this paper, we propose a syntactic pattern recognition approach based on fuzzy automata, which can cope with the variability of patterns by defining imprecise models. This approach is called temporal fuzzy automata as it allows the inclusion of time restrictions to model the duration of the different states. The concept of fuzzy state makes it possible to handle ambiguity as the automaton can be in several states at the same time. Another advantage of our approach is the capability to synchronize with the signal, which allows us to avoid the segmentation stage before the recognition process. Furthermore, a learning method based on dynamic time warping is provided that makes it possible to automatically generate models. Finally, to demonstrate the performance and robustness of this approach, we have applied it to the recognition of hand gestures without any kind of signal preprocessing. © 2009 Elsevier B.V. All rights reserved.

Burgos M.A.,Technical University of Cartagena | Contreras J.,ITP Group | Corra R.,Technical University of Madrid
AIAA Journal | Year: 2011

A method to address the rotor/stator interaction problem on an edge-based Reynolds-averaged Navier-Stokes solver is presented. The implementation of the phase-lagged boundary conditions and a new original conservative discretization of the sliding plane in an unstructured solver is discussed in detail. The numerical method is implicit in time, and convergence is accelerated using a multigrid technique where the coarser grids are obtained by agglomeration. Results of the present method are compared with the experimental results obtained at the National Aerospace Laboratory (The Netherlands) for a subsonic fan.

Besada-Portas E.,Complutense University of Madrid | Lopez-Orozco J.A.,Complutense University of Madrid | Besada J.,Technical University of Madrid | De La Cruz J.M.,Complutense University of Madrid
Automatica | Year: 2011

This paper presents a set of new centralized algorithms for estimating the state of linear dynamic Multiple-Input Multiple-Output (MIMO) control systems with asynchronous, non-systematically delayed and corrupted measurements provided by a set of sensors. The delays, which make the data available Out-Of-Sequence (OOS), appear when using physically distributed sensors, communication networks and pre-processing algorithms. The potentially corrupted measurements can be generated by malfunctioning sensors or communication errors. Our algorithms, designed to work with real-time control systems, handle these problems with a streamlined memory and computational efficient reorganization of the basic operations of the Kalman and Information Filters (KF & IF). The two versions designed to deal only with valid measurements are optimal solutions of the OOS problem, while the other two remaining are suboptimal algorithms able to handle corrupted data. © 2011 Elsevier Ltd. All rights reserved.

Seco-Granados G.,Polytechnic University of Catalonia | Lopez-Salcedo J.A.,Polytechnic University of Catalonia | Jimenez-Banos D.,Polytechnic University of Catalonia | Lopez-Risueno G.,Technical University of Madrid
IEEE Signal Processing Magazine | Year: 2012

Accurately determining ones position has been a recurrent problem in history [1]. It even precedes the first deep-sea navigation attempts of ancient civilizations and reaches the present time with the issue of legal mandates for the location identification of emergency calls in cellular networks and the emergence of location-based services. The science and technology for positioning and navigation has experienced a dramatic evolution [2]. The observation of celestial bodies for navigation purposes has been replaced today by the use of electromagnetic waveforms emitted from reference sources [3] © 2012 IEEE.

Escobar D.,Technical University of Madrid | Ahedo E.,Charles III University of Madrid
Physics of Plasmas | Year: 2014

Results based on a local linear stability analysis of the Hall thruster discharge are presented. A one-dimensional azimuthal framework is used including three species: neutrals, singly charged ions, and electrons. A simplified linear model is developed with the aim of deriving analytical expressions to characterize the stability of the ionization region. The results from the local analysis presented here indicate the existence of an instability that gives rise to an azimuthal oscillation in the +E × B direction with a long wavelength. According to the model, the instability seems to appear only in regions where the ionization and the electric field make it possible to have positive gradients of plasma density and ion velocity at the same time. A more complex model is also solved numerically to validate the analytical results. Additionally, parametric variations are carried out with respect to the main parameters of the model to identify the trends of the instability. As the temperature increases and the neutral-to-plasma density ratio decreases, the growth rate of the instability decreases down to a limit where azimuthal perturbations are no longer unstable. © 2014 AIP Publishing LLC.

Jimenez J.,Technical University of Madrid
Physics of Fluids | Year: 2015

The relevance of linear transitional mechanisms in fully turbulent shear flows, and in particular of the Orr-like inviscid transient amplification of disturbances, is explored in the context of the prediction of bursting behavior. Although the logarithmic layer of wall-bounded turbulence is used as the primary example, most conclusions should apply to other flows with linearly stable mean profiles that are dominated by largescale streamwise-velocity streaks and intermittent bursts of the cross-shear velocity. When the linearised problem is solved in the limit of small viscosity, it has previously been shown that statistical properties, such as the bursting time- and length-scales, the energy fluxes between components, and the mean inclination angles, are consistent in linear and nonlinear systems. The question addressed here is whether the individual structures predicted by the linearised solution can be detected in fully nonlinear simulations, and whether the linearized approximation can be used to predict their evolution. It is found that strong bursting of the largest scales is well described linearly, comprising about 65%-70% of the total time, but that weaker fluctuations are not. It is also found that adding an eddy viscosity does not substantially improve predictions. © 2015 AIP Publishing LLC.

Diez O.,European Medicines Agency EMA | Silva A.,Technical University of Madrid
Quality and Reliability Engineering International | Year: 2014

With the increasing utilisation of Internet services and cloud computing by many organisations (both private and public), it is clear that computing is becoming the fifth utility (along with water, electricity, telephony and gas). These technologies are used for almost all types of systems, and critical systems are now no exception. Even if critical systems appear not to rely directly on cloud services, there may be hidden interdependencies that could affect their resilience. This paper investigates the uses of cloud computing in relation to critical systems and how this affects their resilience, initially comparing it with existing models and frameworks. Some examples are presented together with the associated risks. A framework is introduced for analysing the dependability and resilience of a system that relies on cloud services and how to improve them. As part of the framework, the concepts of micro and macro dependability are introduced to explain the internal and external dependability on services supplied by an external cloud. A pharmacovigilance model system has been used for framework validation. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Walther A.,Aalto University | Walther A.,RWTH Aachen | Timonen J.V.I.,Aalto University | Diez I.,Aalto University | And 3 more authors.
Advanced Materials | Year: 2011

Renewable high-performance macroscopic functional fibers are prepared by a simple wet-extrusion and coagulation process of hydrogels of native cellulose nanofibrils. The fibers are functionalized to be transparent, conducting, or magnetic and they can host and release guests as payloads. These biobased macrofibers provide a sustainable approach for high-performance and functional fiber technology in 21st century technologies. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dumbser M.,University of Trento | Zanotti O.,University of Trento | Hidalgo A.,Technical University of Madrid | Balsara D.S.,University of Notre Dame
Journal of Computational Physics | Year: 2013

We present the first high order one-step ADER-WENO finite volume scheme with adaptive mesh refinement (AMR) in multiple space dimensions. High order spatial accuracy is obtained through a WENO reconstruction, while a high order one-step time discretization is achieved using a local space-time discontinuous Galerkin predictor method. Due to the one-step nature of the underlying scheme, the resulting algorithm is particularly well suited for an AMR strategy on space-time adaptive meshes, i.e. with time-accurate local time stepping. The AMR property has been implemented 'cell-by-cell', with a standard tree-type algorithm, while the scheme has been parallelized via the message passing interface (MPI) paradigm. The new scheme has been tested over a wide range of examples for nonlinear systems of hyperbolic conservation laws, including the classical Euler equations of compressible gas dynamics and the equations of magnetohydrodynamics (MHD). High order in space and time have been confirmed via a numerical convergence study and a detailed analysis of the computational speed-up with respect to highly refined uniform meshes is also presented. We also show test problems where the presented high order AMR scheme behaves clearly better than traditional second order AMR methods. The proposed scheme that combines for the first time high order ADER methods with space-time adaptive grids in two and three space dimensions is likely to become a useful tool in several fields of computational physics, applied mathematics and mechanics. © 2013 Elsevier Inc.

Diaz Lantada A.,Technical University of Madrid
Expert review of medical devices | Year: 2013

Tissue engineering is a rapidly evolving field in which the complexity of biomaterials and biostructures, with typically non-Euclidean or fractal-like geometries, has to be adequately taken into account for the promotion of enhanced and even personalized diagnostic and therapeutic solutions. This study covers the main applications of fractals in the field of tissue engineering, including their advantages for modeling biological processes and cell-culture procedures, but specially focusing on their benefits for describing the complex geometries and structures of biomaterials (both natural and synthetic), many of which have potential uses for the development of cell culture microsystems, scaffolds for tissue repair and implants for tissue repair in general. We also explore the main supporting design, simulation and manufacturing technologies, as well as the most remarkable difficulties and limitations linked to the generalized use of fractals in engineering design, and also detail some current solution proposals and future directions.

Muslija A.,Karlsruhe Institute of Technology | Diaz Lantada A.,Technical University of Madrid
Smart Materials and Structures | Year: 2014

Auxetic materials (or metamaterials) have negative Poisson ratios (NPR) and display the unexpected properties of lateral expansion when stretched, and equal and opposing densification when compressed. Such auxetic materials are being used more frequently in the development of novel products, especially in the fields of intelligent expandable actuators, shape-morphing structures and minimally invasive implantable devices. Although several micromanufacturing technologies have already been applied to the development of auxetic materials and devices, additional precision is needed to take full advantage of their special mechanical properties. In this study, we present a very promising approach for the development of auxetic materials and devices based on the use of deep reactive ion etching (DRIE). The process stands out for its precision and its potential applications to mass production. To our knowledge, it represents the first time this technology has been applied to the manufacture of auxetic materials with nanometric details. We take into account the present capabilities and challenges linked to the use of DRIE in the development of auxetic materials and auxetic-based devices. © 2014 IOP Publishing Ltd.

Hengsbach S.,Karlsruhe Institute of Technology | Lantada A.D.,Technical University of Madrid
Smart Materials and Structures | Year: 2014

Auxetic materials (or metamaterials) are those with a negative Poisson ratio (NPR) and that display the unexpected property of lateral expansion when stretched, as well as an equal and opposing densification when compressed. Such geometries are being progressively employed in the development of novel products, especially in the fields of intelligent expandable actuators, shape morphing structures and minimally invasive implantable devices. Although several micromanufacturing technologies have already been applied to the development of auxetic geometries and devices, additional precision is needed to take full advantage of their special mechanical properties. In this study we present a very promising approach for the development of auxetic metamaterials and devices based on the use of direct laser writing. The process stands out for its precision and complex three-dimensional (3D) geometries attainable without the need of supporting structures. To our knowledge it represents one of the first examples of the application of this technology to the manufacture of auxetic geometries and mechanical metamaterials, with details even more remarkable than those shown in very recent studies, almost reaching the current limit of this additive manufacturing technology. We have used some special 3D auxetic designs whose remarkable NPR has been previously highlighted. © 2014 IOP Publishing Ltd.

Lacasa L.,Technical University of Madrid | Gomez-Gardenes J.,University of Zaragoza
Physical Review Letters | Year: 2013

We propose a new measure to characterize the dimension of complex networks based on the ergodic theory of dynamical systems. This measure is derived from the correlation sum of a trajectory generated by a random walker navigating the network, and extends the classical Grassberger-Procaccia algorithm to the context of complex networks. The method is validated with reliable results for both synthetic networks and real-world networks such as the world air-transportation network or urban networks, and provides a computationally fast way for estimating the dimensionality of networks which only relies on the local information provided by the walkers. © 2013 American Physical Society.

Normand L.M.,Technical University of Madrid
Interactions | Year: 2012

Spain was one of the first countries in the world to publish official standards containing accessibility requirements in computing, including both hardware and software. The first national legislation related to ICT accessibility in Spain was published in 2002, when Act 34/2002 on Information Society Services and Electronic Commerce was passed. Act 34/2002 transposed several European directives and made the accessibility of public administration websites. A year later in 2003, the Spanish government published Act 51/2003 on Equality of Opportunities, Non-Discrimination and Universal Accessibility for Persons with Disabilities. The most recent Spanish accessibility-related legislation was the adoption of the United Nations Convention on the Rights of Persons with Disabilities in 2008. The European undertaking related to the public procurement of accessible ICT is a major accessibility-related activity in which Spain is currently engaged.

Dumbser M.,University of Trento | Hidalgo A.,Technical University of Madrid | Zanotti O.,University of Trento
Computer Methods in Applied Mechanics and Engineering | Year: 2014

We present a class of high order finite volume schemes for the solution of non-conservative hyperbolic systems that combines the one-step ADER-WENO finite volume approach with space-time adaptive mesh refinement (AMR). The resulting algorithm, which is particularly well suited for the treatment of material interfaces in compressible multi-phase flows, is based on: (i) high order of accuracy in space obtained through WENO reconstruction, (ii) a high order one-step time discretization via a local space-time discontinuous Galerkin predictor method, and (iii) the use of a path conservative scheme for handling the non-conservative terms of the equations. The AMR property with time accurate local time stepping, which has been treated according to a cell-by-cell strategy, strongly relies on the high order one-step time discretization, which naturally allows a high order accurate and consistent computation of the jump terms at interfaces between elements using different time steps. The new scheme has been successfully validated on some test problems for the Baer-Nunziato model of compressible multiphase flows. © 2013 Elsevier B.V.

Simon-Loriere E.,Institute Pasteur Paris | Simon-Loriere E.,French National Center for Scientific Research | Holmes E.C.,University of Sydney | Holmes E.C.,U.S. National Institutes of Health | Pagan I.,Technical University of Madrid
Molecular Biology and Evolution | Year: 2013

Gene overlapping is widely employed by RNA viruses to generate genetic novelty while retaining a small genome size. However, gene overlapping also increases the deleterious effect of mutations as they affect more than one gene, thereby reducing the evolutionary rate of RNA viruses and hence their adaptive capacity. Although there is general agreement on the benefits of gene overlapping as a mechanism of genomic compression for rapidly evolving organisms, its effect on the pace of RNA virus evolution remains a source of debate. To address this issue, we collected sequence data from 117 instances of gene overlapping across 19 families, 30 genera, and 55 species of RNA viruses. On these data, we analyzed how genetic distances, selective pressures, and the distribution of RNA secondary structures and conserved protein functional domains vary between overlapping (OV) and nonoverlapping (NOV) regions. We show that gene overlapping generally results in a decrease in the rate of RNA virus evolution through a reduction in the frequency of synonymous mutations. However, this effect is less pronounced in genes with a terminal rather than an internal gene overlap, which might result from a greater proportion of protein functional conserved domains in NOV than in OV regions, in turn reducing the number of nonsynonymous mutations in the former. Overall, our analyses clarify the role of gene overlapping as a modulator of the evolutionary rates exhibited by RNA viruses and shed light on the factors that shape the genetic diversity of this important group of pathogens. © The Author 2013.

Alonso-Sanz R.,Technical University of Madrid
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

The effect of memory of delay type in the dynamics of elementary cellular automata is presented in this study. © 2013 Springer-Verlag.

Pagan I.,Technical University of Madrid | Holguin A.,CIBER ISCIII
PLoS ONE | Year: 2013

The Caribbean and Central America are among the regions with highest HIV-1B prevalence worldwide. Despite of this high virus burden, little is known about the timing and the migration patterns of HIV-1B in these regions. Migration is one of the major processes shaping the genetic structure of virus populations. Thus, reconstruction of epidemiological network may contribute to understand HIV-1B evolution and reduce virus prevalence. We have investigated the spatio-temporal dynamics of the HIV-1B epidemic in The Caribbean and Central America using 1,610 HIV-1B partial pol sequences from 13 Caribbean and 5 Central American countries. Timing of HIV-1B introduction and virus evolutionary rates, as well as the spatial genetic structure of the HIV-1B populations and the virus migration patterns were inferred. Results revealed that in The Caribbean and Central America most of the HIV-1B variability was generated since the 80 s. At odds with previous data suggesting that Haiti was the origin of the epidemic in The Caribbean, our reconstruction indicated that the virus could have been disseminated from Puerto Rico and Antigua. These two countries connected two distinguishable migration areas corresponding to the (mainly Spanish-colonized) Easter and (mainly British-colonized) Western islands, which indicates that virus migration patterns are determined by geographical barriers and by the movement of human populations among culturally related countries. Similar factors shaped the migration of HIV-1B in Central America. The HIV-1B population was significantly structured according to the country of origin, and the genetic diversity in each country was associated with the virus prevalence in both regions, which suggests that virus populations evolve mainly through genetic drift. Thus, our work contributes to the understanding of HIV-1B evolution and dispersion pattern in the Americas, and its relationship with the geography of the area and the movements of human populations. © 2013 Pagán, Holguín.

Nanos N.,Technical University of Madrid | Rodriguez Martin J.A.,Inia Research Center Forestal Cifor
Geoderma | Year: 2012

Source identification of heavy metals in soil is not straightforward since several inputs of either an anthropogenic or natural origin contribute to their total content. Here we explore the spatial variation and covariation of seven heavy metals (Cd, Cr, Ni, Pb, Zn, Cu and Hg) in the agricultural soils of the Duero river basin (one of the largest in Spain) where both anthropogenic activities (mainly agriculture and industry) and natural factors may be responsible for their total concentration. Factorial kriging and principal components analysis were used on a data set that comprised 721 soil samples. We found that the concentrations of heavy metals in the analysed samples do not exceed the limits set by Spanish legislation excepting mercury that presents high values in a limited number of samples (maximum 1041. μg/kg). The linear model of coregionalization-the basic model for factorial kriging analysis-was composed of two structures (representing two scales of variation) with ranges of 20. km (local scale) and 130. km (regional scale). Six of seven elements (Cd, Cr, Ni, Pb, Zn and Cu) were found to be strongly correlated regardless of the spatial scale considered. In contrast, correlations of Hg with other elements were small at the local spatial scale but augmented substantially at the regional scale. We conclude that agricultural practices in the Duero basin have not altered yet the natural content for Cd, Cr, Ni, Pb, Zn and Cu. On the other hand, Hg inputs from human origin, most probably related to airborne emission and deposition from industrial plants, are observable at the local spatial scale. Finally, no human-induced correlations among heavy metals were detected at the regional spatial scale. Based on the results of this study and in accordance with the results obtained in the nearby Ebro river basin (Rodríguez et al., 2008) we conclude that anthropogenic heavy metals in soil are visible only at local spatial scales. In contrast, natural factors maximize their influence on the distribution of heavy metals when considering larger spatial scales. © 2012 Elsevier B.V.

Caro E.,Technical University of Madrid | Valverde G.,University of Costa Rica
IEEE Transactions on Power Systems | Year: 2014

This paper addresses the power system state estimation problem considering the correlations among instrument transformer signals. The correlations among processed measurements are estimated using the Unscented Transformation given the correlation and basic statistical information of internal measurements. In addition, the paper analyzes the impact of these correlations on the estimated states using the IEEE 118-bus test system under various operating conditions and measurement configurations. © 1969-2012 IEEE.

Gomez Del Campo M.,Technical University of Madrid | Garcia J.M.,CSIC - Instituto de la Grasa
Journal of Agricultural and Food Chemistry | Year: 2013

Different irrigation treatments were applied to a superintensive orchard of 'Arbequina' olives (Olea europaea L.) during three seasons (2007-2009) to examine the effect of the amount of water and the moment of irrigation in summer on the virgin olive oil (VOO) quality. A control was made (CON) with irrigation to maintain the root zone close to field capacity; two water deficit treatments were employed with irrigation at 30% of CON, either from the end of fruit drop to the end of July (DI-J) or from the end of July until the beginning of oil synthesis (DI-A); and other treatment was tested by irrigating 50% of CON in July and August (DI-JA). DI-J oils exhibited significantly higher oxidative stability, which coincided with significantly higher contents in phenol derivatives. Consequently, the selection of the moment and intensity of summer irrigation played an important role in the nutritional and sensory quality of the VOO. © 2013 American Chemical Society.

Tablero C.,Technical University of Madrid
Journal of Physical Chemistry C | Year: 2014

Tetrahedrite is among the most common sulfosalts of copper. Its widely accepted formula is Cu12Sb4S13. Studies of pure synthetic, unsubstituted copper tetrahedrite are plagued with difficulties of nonstoichiometry and electron deficiency in its structure. Some tetrahedrite sulfosalts act as semiconductors, while others are metallic compounds, depending on the number of valence electrons and the stoichiometry. We present a first-principles study of the structural, electronic, and optoelectronic properties. In addition to the electron-deficient Cu12Sb 4S13 metallic phase, we have analyzed the electronic and optical properties of three Cu-, Sb-, and S-rich compositions with semiconducting properties. The absorption coefficients show that all tetrahedrites have high absorption coefficients because the S, Cu, and Sb states make a larger contribution to the VB- and CB-edge states. © 2014 American Chemical Society.

Prieto J.L.,Technical University of Madrid
Journal of Non-Newtonian Fluid Mechanics | Year: 2015

The aim of this paper is to present stochastic, micro-macro simulations of droplets rising in non-Newtonian fluids by means of a particle level set method implemented using the Finite Element Method (FEM) and semi-Lagrangian schemes. A set of dumbbells scattered throughout the domain conveys the molecular information from the microscopic scale to the macroscopic scale, first by integrating the stochastic-equivalent of the Fokker-Planck equations, then by taking second moments from the internal configurations to produce the polymer stress tensor to be incorporated into the macroscopic momentum equation. The kinetic models considered in this work are the simpler Hooke (Oldroyd-B constitutive) model, and the more realistic 'Finitely Extensible Nonlinear Elastic' (FENE) model. First, we carry out microscopic and macroscopic convergence analyses to validate the numerical calculations of 2D rising droplets, obtaining satisfactory results for grids of size 1/h={40, 80, 160}, and a number of particles ranging from Nd=105 up to 1.75 · 108, making use of both kinetic models along with mildly viscoelastic effects in solutions with relatively low polymeric concentrations and relaxation times (De=1, c=1). We then perform a series of increasingly elastic simulations that ends up with the arrival of two purely non-Newtonian features: the onset of a cusp-like tail and the appearance of downward velocities at a certain distance of the droplet (negative wake). © 2015 Elsevier B.V.

Fraile A.,Technical University of Madrid
Advances in virus research | Year: 2010

Virus infection may damage the plant, and plant defenses are effective against viruses; thus, it is currently assumed that plants and viruses coevolve. However, and despite huge advances in understanding the mechanisms of pathogenicity and virulence in viruses and the mechanisms of virus resistance in plants, evidence in support of this hypothesis is surprisingly scant, and refers almost only to the virus partner. Most evidence for coevolution derives from the study of highly virulent viruses in agricultural systems, in which humans manipulate host genetic structure, what determines genetic changes in the virus population. Studies have focused on virus responses to qualitative resistance, either dominant or recessive but, even within this restricted scenario, population genetic analyses of pathogenicity and resistance factors are still scarce. Analyses of quantitative resistance or tolerance, which could be relevant for plant-virus coevolution, lag far behind. A major limitation is the lack of information on systems in which the host might evolve in response to virus infection, that is, wild hosts in natural ecosystems. It is presently unknown if, or under which circumstances, viruses do exert a selection pressure on wild plants, if qualitative resistance is a major defense strategy to viruses in nature, or even if characterized genes determining qualitative resistance to viruses did indeed evolve in response to virus infection. Here, we review evidence supporting plant-virus coevolution and point to areas in need of attention to understand the role of viruses in plant ecosystem dynamics, and the factors that determine virus emergence in crops. Copyright © 2010 Elsevier Inc. All rights reserved.

Pena R.,University of Alcala | Algora C.,Technical University of Madrid
Progress in Photovoltaics: Research and Applications | Year: 2012

In this work, a fiber-based optical powering (or power-by-light) system capable of providing more than 1 W is developed. The prototype was used in order to power a shunt regulator for controlling the activation and deactivation of solar panels in satellites. The work involves the manufacture of a light receiver (a GaAs multiple photovoltaic converter (MPC)), a power conditioning block, and a regulator and the implementation and characterization of the whole system. The MPC, with an active area of just 3.1 mm 2, was able to supply 1 W at 5 V with an efficiency of 30%. The maximum measured device efficiency was over 40% at an input power (P in) of 0.5 W. Open circuit voltage over 7 V was measured for P in over 0.5 W. A system optoelectronic efficiency (including the optical fiber, connectors, and MPC) of 27% was measured at an output power (P out) of 1 W. At P out = 0.2 W, the efficiency was as high as 36%. The power conditioning block and the regulator were successfully powered with the system. The maximum supplied power in steady state was 0.2 W, whereas in transient state, it reached 0.44 W. The paper also describes the characterization of the system within the temperature range going from -70 to +100 °C. Copyright © 2011 John Wiley & Sons, Ltd. In this work, a fiber-based optical powering system capable of providing more than 1 W is developed. The prototype was used in order to power a shunt regulator for controlling the activation and deactivation of solar panels in satellites. The work involves the manufacture of a light receiver (a GaAs multiple photovoltaic converter), a power conditioning block, and a regulator and the implementation and characterization of the whole system. Copyright © 2011 John Wiley & Sons, Ltd.

Ortega-Gonzalez F.J.,Technical University of Madrid
IEEE Microwave and Wireless Components Letters | Year: 2010

This letter shows a high-power, high-efficiency, wideband Class-E RF power amplifier designed upon the load admittance synthesis concept and built using an uncomplicated low-loss load network with a low loss wideband admittance transformer as the main component. It uses a power Silicon LDMOS transistor to provide up to 145 W at 28 V peak power, up to 86% drain efficiency over 35% fractional bandwidth (from 85 to 120 MHz) and 15.6 dB gain at peak power without any adjustments. These are clear performance advantages over previous published works and commercially available amplifiers at a similar frequency band and power level. The amplifier applications include FM broadcast, aeronautical communications, nuclear, MRI, heating or RF power stage for Envelope Elimination and Restoration transmitters. © 2010 IEEE.

Sanchez-Torres A.,Technical University of Madrid
Contributions to Plasma Physics | Year: 2014

An electric solar sail (e-sail) is a promising propellantless propulsion concept for the exploration of the Solar System. An e-sail consists of an array of bare conductive tethers at very high positive/negative bias, capable of extracting solar-wind momentum by Coulomb deflection of protons. The present work focuses on the positivebias case with a potential profile that must be correctly modeled. Ion scattering does occur at some point of the profile and the resulting thrust is determined; that thrust scales slower with distance to the Sun, than it was previously suggested in the literature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Algora C.,Technical University of Madrid
Microelectronics Reliability | Year: 2010

III-V concentrator solar cells are starting to be commercialized. However, no complete studies about their reliability have been carried out. A review about both the accelerated ageing tests and real time tests developed till now is presented. A proposal about the required tests is also done. In this stage, the tests show that III-V concentrator cells are robust devices with MTTFs well over the expected ones (30 years). © 2010 Elsevier Ltd. All rights reserved.

Fioravanti A.,Technical University of Madrid
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011

Exploiting the full potential of telemedical systems means using platform based solutions: data are recovered from biomedical sensors, hospital information systems, care-givers, as well as patients themselves, and are processed and redistributed in an either centralized or, more probably, decentralized way. The integration of all these different devices, and interfaces, as well as the automated analysis and representation of all the pieces of information are current key challenges in telemedicine. Mobile phone technology has just begun to offer great opportunities of using this diverse information for guiding, warning, and educating patients, thus increasing their autonomy and adherence to their prescriptions. However, most of these existing mobile solutions are not based on platform systems and therefore represent limited, isolated applications. This article depicts how telemedical systems, based on integrated health data platforms, can maximize prescription adherence in chronic patients through mobile feedback. The application described here has been developed in an EU-funded R&D project called METABO, dedicated to patients with type 1 or type 2 Diabetes Mellitus.

Sausedo-Solorio J.M.,Autonomous University of the State of Hidalgo | Pisarchik A.N.,Technical University of Madrid
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2014

Synchronization of two synaptically coupled neurons with memory and synaptic delay is studied using the Rulkov map, one of the simplest neuron models which displays specific features inherent to bursting dynamics. We demonstrate a transition from lag to anticipated synchronization as the relationship between the memory duration and the synaptic delay time changes. The neuron maps synchronize either with anticipation, if the memory is longer than the synaptic delay time, or with lag otherwise. The mean anticipation time is equal to the difference between the memory and synaptic delay independently of the coupling strength. Frequency entrainment and phase-locking phenomena as well as a transition from regular spikes to chaos are demonstrated with respect to the coupling strength. © 2014 Elsevier B.V.

Pastorino M.,Technical University of Madrid
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011

The aim of this paper is to describe and present the results of the automatic detection and assessment of bradykinesia in motor disease patients using wireless, wearable accelerometers. The current work is related to a module of the PERFORM system, a FP7 project from the European Commission, that aims at providing an innovative and reliable tool, able to evaluate, monitor and manage patients suffering from Parkinson's disease. The assessment procedure was carried out through a developed C# library that detects the activities of the patient using an activity recognition algorithm and classifies the data using a Support Vector Machine trained with data coming from previous test phases. The accuracy between the output of the automatic detection and the evaluation of the clinician both expressed with the Unified Parkinson's disease Rating Scale, presents an average value of [68.3 ± 8.9]%. A meta-analysis algorithm is used in order to improve the accuracy to an average value of [74.4 ± 14.9]%. Future work will include a personalized training of the classifiers in order to achieve a higher level of accuracy.

Network-based methods are being actively developed to respond to the needs for operational assessments of the degree of landscape connectivity and of the impact of landscape changes in ecological flows and related ecological processes. Among these, a recent paper by Matisziw and Murray (2009) presented the C index as an adequate and advantageous way of ranking habitat patches by their importance for the maintenance of landscape connectivity. We show that this index is equivalent and conveys the same information in undirected graphs as a previously described index, the landscape coincidence probability (LCP), which can be readily computed in any landscape network through the Conefor Sensinode software package. We slightly generalize the LCP definition for cases involving asymmetric dispersal, which makes LCP compatible with C and maintains the equivalency between both indices in directed graphs. We place LCP and C in a broader context of other existing indices and ongoing developments and describe how some of these may be better suited for the analysis of the connectivity in landscape networks and their changes. We conclude by highlighting the need (1) to go beyond the identification of unobstructed movement paths or habitat components (sets of interconnected patches) when pursuing the most appropriate landscape connectivity indices and (2) for increased efforts in assessing and reporting the potential overlaps, coincidences and synergies between the available approaches in order to guide the final user and facilitate index selection in a densely populated metric space.

Sesma A.,Technical University of Madrid
Seminars in Cell and Developmental Biology | Year: 2016

The development of RNA imaging techniques and the establishment of systems biology approaches, together with the improvement of large-scale RNA-protein crosslinking immunoprecipitation protocols have enormously expanded our knowledge of RNA networks and the function of RNA-binding proteins in metazoans and model yeasts. In pathogenic fungi, the biological role of the vast majority of RNA-binding proteins and non-coding RNAs is still largely unknown. However, many RNA-dependent mechanisms which shape fungal pathogenicity have been defined. Here, advances made in this field are reviewed and further theories of biological significance are discussed in the light of latest findings. © 2016.

Porras M.A.,Technical University of Madrid
Optics Express | Year: 2010

Spatiotemporal self-focusing in nonlinear lossy media pushes ultrashort pulses towards a universal, non-solitary and non-conical lightbullet wave state defined by the medium solely, and characterized by maximum energy losses. Its stationary propagation relies on a balance between nonlinear losses and the refuelling effect of self-focusing. No balancing gain is required for stationarity. These purely lossy dissipative light-bullets can explain many aspects of the filamentary dynamics in nonlinear media with anomalous dispersion. © 2010 Optical Society of America.

Plaza G.R.,Technical University of Madrid
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

Disordered networks are found in many natural and artificial materials, from gels or cytoskeletal structures to metallic foams or bones. Here, the energy distribution in this type of networks is modeled, taking into account the orientation of the struts. A correlation between the orientation and the energy per unit volume is found and described as a function of the connectivity in the network and the relative bending stiffness of the struts. If one or both parameters have relatively large values, the struts aligned in the loading direction present the highest values of energy. On the contrary, if these have relatively small values, the highest values of energy can be reached in the struts oriented transversally. This result allows explaining in a simple way remodeling processes in biological materials, for example, the remodeling of trabecular bone and the reorganization in the cytoskeleton. Additionally, the correlation between the orientation, the affinity, and the bending-stretching ratio in the network is discussed. © 2010 The American Physical Society.

Morelande M.R.,University of Melbourne | Garcia-Fernandez A.F.,Technical University of Madrid
IEEE Transactions on Signal Processing | Year: 2013

A theoretical analysis is presented of the correction step of the Kalman filter (KF) and its various approximations for the case of a nonlinear measurement equation with additive Gaussian noise. The KF is based on a Gaussian approximation to the joint density of the state and the measurement. The analysis metric is the Kullback-Leibler divergence of this approximation from the true joint density. The purpose of the analysis is to provide a quantitative tool for understanding and assessing the performance of the KF and its variants in nonlinear scenarios. This is illustrated using a numerical example. © 2013 IEEE.

Higuera F.J.,Technical University of Madrid
Physics of Fluids | Year: 2010

Order-of-magnitude estimates and numerical computations are used to analyze an electrospray operating in the cone-jet mode in a bath of an immiscible dielectric liquid. In agreement with experimental results in the literature, the analysis predicts that the electric current carried by the jet increases as the square root of the flow rate of dispersed liquid in a wide range of conditions of the flow. The characteristics of the current transfer region determining the electric current are estimated taking into account the viscous drag of the dielectric liquid that surrounds the jet. The electric current is predicted to depart from the square root law for small flow rates, when charge relaxation effects become important in the current transfer region, and also when the flow rate increases to values of the order of QM=ε{lunate}0γ2a/μ2 2K, where ε{lunate}0 and μ2 are the permittivity and viscosity of the dielectric liquid, K is the electrical conductivity of the dispersed liquid, a is the radius of the capillary needle through which this liquid is injected, and γ is the interfacial tension of the liquid pair. When the flow rate becomes of order QM, the meniscus at the tip of the capillary ceases to resemble a Taylor cone, the current transfer region ceases to be short compared to the size of the meniscus, the electric current levels to a constant value, and the stationary jet cannot extend very far downstream of the meniscus. © 2010 American Institute of Physics.

Berto F.,University of Padua | Campagnolo A.,University of Padua | Elices M.,Technical University of Madrid | Lazzarin P.,University of Padua
Materials and Design | Year: 2013

In this paper a volume criterion based on a simple scalar quantity, the mean value of the strain energy (SED), has been used to assess the static strength of notched components made of Polymethylmethacrylate (PMMA).The control volume is thought of as dependent on the linear elastic ultimate tensile strength and the fracture toughness in the case of brittle or quasi-brittle materials subjected to static loadings.The local-strain-energy based approach has been applied to two well-documented set of experimental data recently reported in the literature. Data refer to blunt U-notched specimens of commercial PMMA subjected to static loads and characterised by a large variability of notch tip radius (from 0.25. mm to 2.5. mm).Critical loads obtained experimentally have been compared with the theoretical ones, estimated by keeping constant the mean value of the strain energy in a well-defined small size volume.In addition, some new tests dealing with V-notched specimens with end holes have been carried out to investigate the effect of the notch opening angle and thirty new data have been summarised in terms of the SED. The new data have permitted to strengthen the validation aspects of the modelling. © 2013 Elsevier Ltd.

Coudert L.H.,University Paris Est Creteil | Pacios L.F.,Technical University of Madrid | Ortigoso J.,CSIC - Institute for the Structure of Matter
Physical Review Letters | Year: 2011

Control of the torsional angles of nonrigid molecules is key for the development of emerging areas like molecular electronics and nanotechnology. Based on a rigorous calculation of the rotation-torsion-Stark energy levels of nonrigid biphenyl-like molecules, we show that, unlike previously believed, instantaneous rotation-torsion-Stark eigenstates of such molecules, interacting with a strong laser field, present a large degree of delocalization in the torsional coordinate even for the lowest energy states. This is due to a strong coupling between overall rotation and torsion leading to a breakdown of the torsional alignment. Thus, adiabatic control of changes on the planarity of this kind of molecule is essentially impossible unless the temperature is on the order of a few Kelvin. © 2011 American Physical Society.

Gaite J.,Technical University of Madrid
Journal of Cosmology and Astroparticle Physics | Year: 2010

We develop a method of multifractal analysis of N-body cosmological simulations that improves on the customary counts-in-cells method by taking special care of the effects of discreteness and large scale homogeneity. The analysis of the Mare-Nostrum simulation with our method provides strong evidence of self-similar multifractal distributions of dark matter and gas, with a halo mass function that is of Press-Schechter type but has a power-law exponent -2, as corresponds to a multifractal. Furthermore, our analysis shows that the dark matter and gas distributions are indistinguishable as multifractals. To determine if there is any gas biasing, we calculate the cross-correlation coefficient, with negative but inconclusive results. Hence, we develop an effective Bayesian analysis connected with information theory, which clearly demonstrates that the gas is biased in a long range of scales, up to the scale of homogeneity. However, entropic measures related to the Bayesian analysis show that this gas bias is small (in a precise sense) and is such that the fractal singularities of both distributions coincide and are identical. We conclude that this common multifractal cosmic web structure is determined by the dynamics and is independent of the initial conditions. © 2010 IOP Publishing Ltd and SISSA.

Higuera F.J.,Technical University of Madrid
Journal of Fluid Mechanics | Year: 2010

A numerical study is carried out of the injection of a very viscous liquid of small electrical conductivity at a constant flow rate through an orifice in a metallic plate under the action of an electric field. The conditions under which the injected liquid can form an elongated meniscus with a thin jet emanating from its tip are investigated by computing the flow, the electric field and the transport of electric charge in the meniscus and a leading region of the jet. A stationary solution is found only for values of the flow rate above a certain minimum. At moderate values of the applied field, this minimum flow rate decreases when the applied field or the conductivity of the liquid increase. The electric shear stress acting on the surface of the liquid is not able to drive the liquid into the jet at flow rates smaller than the minimum while, for any flow rate higher than the minimum, the transfer of electric current to the surface may occur in a slender region of the jet where charge relaxation effects are small and the field induced by the electric charge of the jet is important. At high values of the applied field, the flow rate must be higher than another minimum, which increases with the applied field, in order for the viscous stress to balance the strong electric stress acting on the meniscus. The two conditions taken together determine lower and upper bounds for the applied field at a given flow rate, but the value of the applied field at which a stationary jet is first established when this parameter is gradually increased is higher than the lower bound, leading to hysteresis. When the liquid is electrosprayed in a surrounding dielectric fluid, the viscous shear stress that this fluid exerts on the surface of the jet eventually balances the electric shear stress and stops the continuous stretching of the jet. A fraction of the conduction current is left in the jet when the effect of the outer liquid comes into play in the region where this current is transferred to the surface, and no stationary solution is found above a maximum flow rate that decreases when the viscosity of the outer liquid increases or the applied field decreases. Order of magnitude estimates of the electric current and the conditions in the current transfer region are worked out. © 2010 Cambridge University Press.

Diez-Pascual A.M.,CSIC - Institute of Polymer Science and Technology | Naffakh M.,Technical University of Madrid
Composites Part A: Applied Science and Manufacturing | Year: 2013

The thermal and thermomechanical properties of poly(phenylene sulphide) (PPS) based nanocomposites incorporating a polymer derivative covalently anchored onto single-walled carbon nanotubes (SWCNTs) were investigated. The grafted fillers acted as nucleating agents, increasing the crystallization temperature and degree of crystallinity of the matrix. They also enhanced its thermal stability, flame retardancy, glass transition (Tg) and heat deflection temperatures while reduced the coefficient of thermal expansion at temperatures below Tg. A strong rise in the thermal conductivity, Young's modulus and tensile strength was found with increasing filler loading both in the glassy and rubbery states. All these outstanding improvements are ascribed to strong matrix-filler interfacial interactions combined with a compatibilization effect that results in very homogeneous SWCNT dispersion. The results herein offer useful insights towards the development of engineering thermoplastic/CNT nanocomposites for high-temperature applications. © 2013 Elsevier Ltd. All rights reserved.

Ruiz-Garcia L.,Technical University of Madrid | Rothmund M.,OSB AG
Food Control | Year: 2010

There is an increasing demand of traceability in the food chain, statutory requirements are growing stricter and there is increasing pressure to develop standardized traceability systems. Each event in the chain, like production of transportation, packing, distribution or processing results in a different product which can have its own information associated within the tracing system. From the raw material to the sale of goods, more and more information needs to be gathered and made available. Supplementary information may also be collected at any step, in order to provide data for analysis and optimization of production practices. Using web-based systems for data processing, storage and transfer makes possible a flexible way of information access, networking and usability. In this paper an architectural proposal is presented and the proposed solution is tested by the implementation of a prototype. The software architecture presented makes use of a series of standards than offer new possibilities in traceability control and management. For testing the prototype, information from precision farming together with the information recorded during the transport and delivery was used. The system enables full traceability and it complies with all existing traceability standards. © 2008 Elsevier Ltd. All rights reserved.

Sanmartin J.R.,Technical University of Madrid
Plasma Sources Science and Technology | Year: 2010

A bare electrodynamic tether (EDT) is a conductive thin wire or tape tens of kilometres long, which is kept taut in space by gravity gradient or spinning, and is left bare of insulation to collect (and carry) current as a cylindrical Langmuir probe in an ambient magnetized plasma. An EDT is a probe in mesothermal flow at highly positive (or negative) bias, with a large or extremely large 2D sheath, which may show effects from the magnetic self-field of its current and have electrons adiabatically trapped in its ram front. Beyond technical applications ranging from propellantless propulsion to power generation in orbit, EDTs allow broad scientific uses such as generating electron beams and artificial auroras, exciting Alfven waves and whistlers, modifying the radiation belts and exploring interplanetary space and the Jovian magnetosphere. Asymptotic analysis, numerical simulations, ground and space tests and past and planned missions on EDTs are briefly reviewed. © 2010 IOP Publishing Ltd.

Sanchez-Arriaga G.,Technical University of Madrid
Physics of Plasmas | Year: 2010

The evolution of weakly dispersive nonlinear Alfven waves propagating either parallel or oblique to the ambient magnetic field is investigated through the derivative nonlinear Schrödinger equation (DNLS) perturbed by nonlinear Landau damping. The dynamics is analyzed with the aid of a numeric algorithm based on the inverse scattering transform (IST) and an adiabatic model that takes advantages of the perturbed DNLS invariants. Both techniques are applied to five types of DNLS soliton and multisoliton solutions: (i) the parallel Alfven soliton, (ii) the bright and dark one-parameter oblique, (iii) the breather two-parameter oblique, (iv) two parallel Alfven solitons, and (v) the combination of a dark and a bright oblique solitons. For the parallel solitons, the adiabatic model describes correctly the dynamics and it also recovers the well-known result given by the perturbed IST. Due to the radiation emission and the formation of dark solitons, the behavior of oblique solitons is more complicated and multisoliton solutions are required in the adiabatic model. The analysis shows that parallel solitons develop into the normal regime, whereas the oblique waves leads to the formation of dark solitons and breathers with a wavepacket form. © 2010 American Institute of Physics.

Corres-Peiretti H.,Technical University of Madrid
Structural Concrete | Year: 2013

Conceptual design is the approach that creates an idea in order to find a solution to a new proposal for a structure or solve a detail in a specific structure. It is a personal approach that is learned over time and with experience. It is not normally dealt with at university, but is vitally important for producing sound structures. The fib Model Code for Concrete Structures 2010 introduced this concept in the first section of chapter 7 "Design". The content of that section explains the general approach to developing conceptual design. This paper will show different examples of conceptual design following the general guidelines stated in the Model Code. © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Tablero C.,Technical University of Madrid
Journal of Physical Chemistry C | Year: 2012

The Cu 2ZnSnS 4 (CZTS) semiconductor is a potential photovoltaic material due to its optoelectronic properties. These optoelectronic properties can be potentially improved by the insertion of intermediate states into the energy bandgap. We explore this possibility using Cr as an impurity. We carried out first-principles calculations within the density functional theory analyzing three substitutions: Cu, Sn, or Zn by Cr. In all cases, the Cr introduces a deeper band into the host energy bandgap. Depending on the substitution, this band is full, empty, or partially full. The absorption coefficients in the independent-particle approximation have also been obtained. Comparison between the pure and doped host's absorption coefficients shows that this deeper band opens more photon absorption channels and could therefore increase the solar-light absorption with respect to the host. © 2012 American Chemical Society.

Santarsiero M.,Third University of Rome | Piquero G.,Complutense University of Madrid | De Sande J.C.G.,Technical University of Madrid | Gori F.,Third University of Rome
Optics Letters | Year: 2014

Generally speaking, the difference between two cross-spectral densities (CSDs) does not represent a correlation function. We will furnish a sufficient condition so that such difference be a valid CSD. Using such a condition, we will show through some exampleshownew classes of CSDs can be generated. ©2014 Optical Society of America.

Romero G.,Technical University of Madrid
Advances in Experimental Medicine and Biology | Year: 2010

Thrombectomy devices have been developed as an alternative means for clot removal. A number of devices using a variety of methods to remove the clot are now available. This chapter covers the analysis and research into a device recently developed in the UK, called a "GP" thrombus aspiration device (TAD). Presented in this work is the development of a model of this device, as well as its simulation and interpretation of the results obtained with the potential for helping in optimizing its operation for future use. The simulation model that is presented can be used in showing the potential performance of the "GP" TAD device under different conditions of blood flow and size of blood clot, obtaining the minimum pressure necessary to extract the clot and to check that both this pressure and the time required to complete the operation are reasonable for potential use in clinical situations patients, and are in line with experimentally obtained data. © 2010 Springer Science+Business Media, LLC.

Transmitting messages in the most efficient way as possible has always been one of politicians' main concerns during electoral processes. Due to the rapidly growing number of users, online social networks have become ideal platforms for politicians to interact with their potential voters. Exploiting the available potential of these tools to maximize their influence over voters is one of politicians' actual challenges. To step in this direction, we have analyzed the user activity in the online social network Twitter, during the 2011 Spanish Presidential electoral process, and found that such activity is correlated with the election results. We introduce a new measure to study political sentiment in Twitter, which we call the relative support. We have also characterized user behavior by analyzing the structural and dynamical patterns of the complex networks emergent from the mention and retweet networks. Our results suggest that the collective attention is driven by a very small fraction of users. Furthermore, we have analyzed the interactions taking place among politicians, observing a lack of debate. Finally, we develop a network growth model to reproduce the interactions taking place among politicians.

Prieto J.L.,Technical University of Madrid
Computer Methods in Applied Mechanics and Engineering | Year: 2016

We present in this paper a multiscale, micro-macro, particle level set method for Newtonian and non-Newtonian interface flows. The technique, termed SLEIPNNIR ('Semi-Lagrangian Ensemble Implementation of Particle level set for Newtonian and non-Newtonian Interfacial Rheology'), uses the finite element method in a semi-Lagrangian framework for the discretization of the governing equations, capturing the free surface by means of a particle level set strategy where all involved magnitudes are computed sharply. Surface tension effects are considered via the Laplace-Beltrami operator using a fully-explicit or semi-implicit technique, with a second-order accurate reinitialization procedure to ensure the signed distance property. Non-Newtonian fluids are tackled by means of a stochastic, variance-reduced, kinetic modeling approach in which the polymer stress tensor is retrieved making use of Compactly-Supported Radial Basis Functions for randomly scattered data interpolation.We carry out numerical tests to highlight the versatility, robustness and accuracy of the proposed scheme through a series of bubble dynamics experiments in a 2D setup, for large density and viscosity ratios, and featuring strong, purely elastic effects relevant to Engineering applications. © 2016 Elsevier B.V.

Gomez-Del-Campo M.,Technical University of Madrid | Garcia J.M.,CSIC - Instituto de la Grasa
JAOCS, Journal of the American Oil Chemists' Society | Year: 2012

The effect of location of fruit in canopies of hedgerow olive trees (Olea europaea L., cv. 'Arbequina') on quality of virgin oil was tested by analyzing oils extracted from different height layers and faces of nine olive hedgerows (6 North-South oriented and 3 East-West). Although sensory attributes were not different, other oil quality parameters may be significantly modified by fruit position. Oils extracted from fruits harvested from higher layers exhibited significantly higher stability against oxidation, along with higher palmitic acid, linoleic acid and phenol contents, but lower oleic acid content. Oils extracted from fruits harvested from East and North facing hedgerows oriented North-South and East-West, respectively, exhibited higher oleic contents and lower saturated and polyunsaturated fatty acid contents. The mean phenol content of oils extracted from fruits from a North-South oriented hedgerow was significantly greater from one of the East-West oriented hedgerows. These findings may be relevant for the design of future olive hedgerows destined for olive oil production. © 2011 AOCS.

Encinar J.A.,Technical University of Madrid | Arrebola M.,University of Oviedo | De La Fuente L.F.,Airbus | Toso G.,European Space Agency
IEEE Transactions on Antennas and Propagation | Year: 2011

A 1.2-meter reflectarray antenna has been designed to accomplish the requirements of a Direct Broadcast Satellite (DBS) mission, which provides a South America transmit-receive coverage in Ku band. The antenna has been designed by applying first of all a pattern synthesis technique to obtain the required phase distribution on the reflectarray at several frequencies in transmit and receive bands. Then, the patch dimensions have been optimized in a configuration made of three stacked layers of varying-sized patches in order to provide the required phase distribution at transmit and receive frequencies. An antenna demonstrator has been manufactured and tested. The measured patterns are in good agreement with the simulations and they are close to fulfill the coverage requirements in both transmit and receive bands. © 2006 IEEE.

Bombardelli C.,Technical University of Madrid | Bau G.,University of Padua
Celestial Mechanics and Dynamical Astronomy | Year: 2012

We present analytical formulas to estimate the variation of achieved deflection for an Earth-impacting asteroid following a continuous tangential low-thrust deflection strategy. Relatively simple analytical expressions are obtained with the aid of asymptotic theory and the use of Peláez orbital elements set, an approach that is particularly suitable to the asteroid deflection problem and is not limited to small eccentricities. The accuracy of the proposed formulas is evaluated numerically showing negligible error for both early and late deflection campaigns. The results will be of aid in planning future low-thrust asteroid deflection missions. © 2012 Springer Science+Business Media B.V.

Barrero-Gil A.,Technical University of Madrid
Journal of Vibration and Acoustics, Transactions of the ASME | Year: 2011

An attempt to measure indirectly the hydrodynamic drag (cD) and inertia (cM) coefficients on oscillating bluff cylinders (circular and square) in quiescent fluid at low Reynolds numbers (low Stokes number) is presented. The Keulegan-Carpenter number was below 15. The experimental approach is based on performing free-decay tests of a spring-mounted cylinder submerged in a water tank. The identification of the instantaneous modal parameters (damping and frequency), via Hilbert transform, of the decaying oscillations allows the determination of (cD) and (cM) by direct comparison with the damping and natural frequency of the system in still air (tank without water). Advantages and shortcomings of this novel experimental approach are presented along the paper. © 2011 American Society of Mechanical Engineers.

Pisarchik A.N.,Technical University of Madrid | Feudel U.,Carl von Ossietzky University
Physics Reports | Year: 2014

Multistability or coexistence of different attractors for a given set of parameters is one of the most exciting phenomena in dynamical systems. It can be found in different areas of science, such as physics, chemistry, biology, economy, and in nature. The final state of a multistable system depends crucially on the initial conditions. From the viewpoint of applications, there are two major issues related to the emergence of multistability. On one hand, this phenomenon often can create inconvenience, as for instance, in the design of a commercial device with specific characteristics, where multistability needs to be avoided or the desired state has to be stabilized against a noisy environment, and on the other hand, the coexistence of different stable states offers a great flexibility in the system performance without major parameter changes, that can be used with the right control strategies to induce a definite switching between different coexisting states. These two examples alone illustrate the importance of multistability control in applied nonlinear science. For the last decade a lot of research has been devoted to the development of control techniques of multistable systems. These methods cover several strategies, going from feedback control methods to nonfeedback, such as periodic or stochastic perturbations capable of changing the coexisting states stability and driving the system from multistability to monostability. We review the most representative control strategies, discuss their theoretical background and experimental realization. © 2014 Elsevier B.V.

Khayet M.,Complutense University of Madrid | Fernandez V.,Technical University of Madrid
Theoretical Biology and Medical Modelling | Year: 2012

Background: Most aerial plant parts are covered with a hydrophobic lipid-rich cuticle, which is the interface between the plant organs and the surrounding environment. Plant surfaces may have a high degree of hydrophobicity because of the combined effects of surface chemistry and roughness. The physical and chemical complexity of the plant cuticle limits the development of models that explain its internal structure and interactions with surface-applied agrochemicals. In this article we introduce a thermodynamic method for estimating the solubilities of model plant surface constituents and relating them to the effects of agrochemicals. Results: Following the van Krevelen and Hoftyzer method, we calculated the solubility parameters of three model plant species and eight compounds that differ in hydrophobicity and polarity. In addition, intact tissues were examined by scanning electron microscopy and the surface free energy, polarity, solubility parameter and work of adhesion of each were calculated from contact angle measurements of three liquids with different polarities. By comparing the affinities between plant surface constituents and agrochemicals derived from (a) theoretical calculations and (b) contact angle measurements we were able to distinguish the physical effect of surface roughness from the effect of the chemical nature of the epicuticular waxes. A solubility parameter model for plant surfaces is proposed on the basis of an increasing gradient from the cuticular surface towards the underlying cell wall. Conclusions: The procedure enabled us to predict the interactions among agrochemicals, plant surfaces, and cuticular and cell wall components, and promises to be a useful tool for improving our understanding of biological surface interactions. © 2012 Khayet and Fernández; licensee BioMed Central Ltd.

Fernandez-Jambrina L.,Technical University of Madrid
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

In Haro, Amorós, and Pan [Phys. Rev. D 93, 084018 (2016)] a new cosmological model is proposed with no big bang singularity in the past, though past geodesically incomplete. This model starts with an inflationary era, follows with a stiff matter dominated period and evolves to accelerated expansion in an asymptotically de Sitter regime in a realistic fashion. The big bang singularity is replaced by a directional singularity. This singularity cannot be reached by comoving observers, since it would take them an infinite proper time lapse to go back to it. On the contrary, observers with nonzero linear momentum have the singularity at finite proper time in their past, though arbitrarily large. Hence, the time lapse from the initial singularity can be as long as desired, even infinity, depending on the linear momentum of the observer. This conclusion applies to similar inflationary models. Due to the interest of these models, we address here the properties of such singularities. © 2016 American Physical Society.

Notzel R.,Technical University of Madrid | Urbanczyk A.,TU Eindhoven
Current Opinion in Solid State and Materials Science | Year: 2012

Concepts of lateral ordering of epitaxial semiconductor quantum dots (QDs) are for the first time transferred to hybrid nanostructures for active plasmonics. We review our recent research on the self-alignment of epitaxial nanocrystals of In and Ag on ordered one-dimensional In(Ga)As QD arrays and isolated QDs by molecular beam epitaxy. By changing the growth conditions the size and density of the metal nanocrystals are easily controlled and the surface plasmon resonance wavelength is tuned over a wide range in order to match the emission wavelength of the QDs. Photoluminescence measurements reveal large enhancement of the emitted light intensity due to plasmon enhanced emission and absorption down to the single QD level. © 2012 Elsevier Ltd. All rights reserved.

Gomez-Ramirez J.,Technical University of Madrid | Gomez-Ramirez J.,Okayama University | Wu J.,Okayama University
Frontiers in Aging Neuroscience | Year: 2014

By 2050 it is estimated that the number of worldwide Alzheimer's disease (AD) patients will quadruple from the current number of 36 million people. To date, no single test, prior to postmortem examination, can confirm that a person suffers from AD. Therefore, there is a strong need for accurate and sensitive tools for the early diagnoses of AD. The complex etiology and multiple pathogenesis of AD call for a system-level understanding of the currently available biomarkers and the study of new biomarkers via network-based modeling of heterogeneous data types. In this review, we summarize recent research on the study of AD as a connectivity syndrome. We argue that a network-based approach in biomarker discovery will provide key insights to fully understand the network degeneration hypothesis (disease starts in specific network areas and progressively spreads to connected areas of the initial loci-networks) with a potential impact for early diagnosis and disease-modifying treatments. We introduce a new framework for the quantitative study of biomarkers that can help shorten the transition between academic research and clinical diagnosis in AD. © 2014 Gomez-Ramirez and Wu.

Cara J.,Technical University of Madrid
Journal of Sound and Vibration | Year: 2016

Modal parameters comprise natural frequencies, damping ratios, modal vectors and modal masses. In a theoretic framework, these parameters are the basis for the solution of vibration problems using the theory of modal superposition. In practice, they can be computed from input-output vibration data: the usual procedure is to estimate a mathematical model from the data and then to compute the modal parameters from the estimated model. The most popular models for input-output data are based on the frequency response function, but in recent years the state space model in the time domain has become popular among researchers and practitioners of modal analysis with experimental data. In this work, the equations to compute the modal parameters from the state space model when input and output data are available (like in combined experimental-operational modal analysis) are derived in detail using invariants of the state space model: the equations needed to compute natural frequencies, damping ratios and modal vectors are well known in the operational modal analysis framework, but the equation needed to compute the modal masses has not generated much interest in technical literature. These equations are applied to both a numerical simulation and an experimental study in the last part of the work. © 2016 Elsevier Ltd.

Alonso-Medina A.,Technical University of Madrid
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2011

The Stark full widths at half of the maximal line intensity (FWHM, ω) have been measured for 25 spectral lines of Pb III (15 measured for the first time) arising from the 5d106s8s, 5d106s7p, 5d 106s5f and 5d106s5g electronic configurations, in a lead plasma produced by ablation with a Nd:YAG laser. The optical emission spectroscopy from a laser-induced plasma generated by a 10 640 Å radiation, with an irradiance of 2 × 1010 W cm- 2 on a lead target (99.99% purity) in an atmosphere of argon was analysed in the wavelength interval between 2000 and 7000 Å. The broadening parameters were obtained with the target placed in argon atmosphere at 6 Torr and 400 ns after each laser light pulse, which provides appropriate measurement conditions. A Boltzmann plot was used to obtain the plasma temperature (21,400 K) and published values of the Stark widths in Pb I, Pb II and Pb III to obtain the electron number density (7 × 1016 cm- 3); with these values, the plasma composition was determined by means of the Saha equation. Local Thermodynamic Equilibrium (LTE) conditions and plasma homogeneity has been checked. Special attention was dedicated to the possible self-absorption of the different transitions. Comparison of the new results with recent available data is also presented. © 2011 Elsevier B.V. All rights reserved.

Background: Conventional scientometric predictors of research performance such as the number of papers, citations, and papers in the top 1% of highly cited papers cannot be validated in terms of the number of Nobel Prize achievements across countries and institutions. The purpose of this paper is to find a bibliometric indicator that correlates with the number of Nobel Prize achievements. Methodology/Principal Findings: This study assumes that the high-citation tail of citation distribution holds most of the information about high scientific performance. Here I propose the x-index, which is calculated from the number of national articles in the top 1% and 0.1% of highly cited papers and has a subtractive term to discount highly cited papers that are not scientific breakthroughs. The x-index, the number of Nobel Prize achievements, and the number of national articles in Nature or Science are highly correlated. The high correlations among these independent parameters demonstrate that they are good measures of high scientific performance because scientific excellence is their only common characteristic. However, the x-index has superior features as compared to the other two parameters. Nobel Prize achievements are low frequency events and their number is an imprecise indicator, which in addition is zero in most institutions; the evaluation of research making use of the number of publications in prestigious journals is not advised. Conclusion: The x-index is a simple and precise indicator for high research performance. © 2011 Alonso Rodriguez-Navarro.

Saura S.,Technical University of Madrid | Estreguil C.,European Commission - Joint Research Center Ispra | Mouton C.,European Commission - Joint Research Center Ispra | Rodriguez-Freire M.,European Commission - Joint Research Center Ispra
Ecological Indicators | Year: 2011

Landscape networks and ecosystems worldwide are undergoing changes that may impact in different ways relevant ecological processes such as gene flow, pollination, or wildlife dispersal. Amyriad of indices have been developed to characterize landscape patterns, but not all of them are equally suited to evaluate temporal changes in landscape connectivity as is increasingly needed for biodiversity monitoring and operational indicator delivery. Relevant advancements in this direction have been recently proposed based on graph theoretical methods to analyze landscape network connectivity and on the measurement of habitat availability at the landscape scale. Building from these developments, wemodify arecent index and present the equivalent connected area (ECA) index, defined as the size of a single patch (maximally connected) that would provide the same probability of connectivity than the actual habitat pattern in the landscape. The temporal changes in ECA can be directly compared with the changes in total habitat area. This allows for additional and straightforward insights on the degree to which the gains or losses in habitat amount can be beneficial or deleterious by affecting landscape elements that uphold connectivity in a wider landscape context. We provide a demonstrative example of application and interpretation of this index and approach to monitor changes in functional landscape connectivity. We focus on the trends in European forests at the province level in the period 1990-2000 from Corine land cover data, considering both changes in the forest spatial pattern and in the average permeability of the landscape matrix. The degree of connectivity was rather stable over most of the study area, with a slight overall increase in forest connectivity in Europe. However, a few countries and regions concentrated remarkably high changes in the analyzed period, particularly those with a low forest cover. The species traits also affected the responses to landscape pattern changes, which were more prominent for those species with limited dispersal abilities. We conclude discussing the potential of this approach for consistent indicator delivery, as well as the limitations and possibilities of application to a variety of situations, for which the required quantitative tools are freely available as open source projects. © 2010 Elsevier Ltd. All rights reserved.

De Sande J.C.G.,Technical University of Madrid | Piquero G.,Complutense University of Madrid | Teijeiro C.,Complutense University of Madrid
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2012

Lyot depolarizers are optical devices made of birefringent materials used for producing unpolarized beams from totally polarized incident light. The depolarization is produced for polychromatic input beams due to the different phase introduced by the Lyot depolarizer for each wavelength. The effect of this device on other types of incident fields is investigated. In particular two cases are analyzed: (i) monochromatic and nonuniformly polarized incident beams and (ii) incident light synthesized by superposition of two monochromatic orthogonally polarized beams with different wavelengths. In the last case, it is theoretically and experimentally shown that the Lyot depolarizer increases the degree of polarization instead of depolarizes. © 2012 Optical Society of America.

Ferrin J.L.,University of Santiago de Compostela | Saavedra L.,Technical University of Madrid
Fuel Processing Technology | Year: 2013

The efficiency of a Power Plant is affected by the distribution of the pulverized coal within the furnace. The coal, which is pulverized in the mills, is transported and distributed by the primary gas through the mill-ducts to the interior of the furnace. This is done with a double function: dry and enter the coal by different levels for optimizing the combustion in the sense that a complete combustion occurs with homogeneous heat fluxes to the walls. The mill-duct systems of a real Power Plant are very complex and they are not yet well understood. In particular, experimental data concerning the mass flows of coal to the different levels are very difficult to measure. CFD modeling can help to determine them. An Eulerian/Lagrangian approach is used due to the low solid-gas volume ratio. © 2012 Elsevier B.V.

Datas A.,Technical University of Madrid
Applied Physics Letters | Year: 2016

A conceptual device for the direct conversion of heat into electricity is presented. This concept hybridizes thermionic (TI) and thermophotovoltaic (TPV) energy conversion in a single thermionic-photovoltaic (TIPV) solid-state device. This device transforms into electricity both the electron and photon fluxes emitted by an incandescent surface. This letter presents an idealized analysis of this device in order to determine its theoretical potential. According to this analysis, the key advantage of this converter, with respect to either TPV or TI, is the higher power density in an extended temperature range. For low temperatures, TIPV performs like TPV due to the negligible electron flux. On the contrary, for high temperatures, TIPV performs like TI due to the great enhancement of the electron flux, which overshadows the photon flux contribution. At the intermediate temperatures, ∼1650 K in the case of this particular study, I show that the power density potential of TIPV converter is twice as great as that of TPV and TI. The greatest impact concerns applications in which the temperature varies in a relatively wide range, for which averaged power density enhancement above 500% is attainable. © 2016 AIP Publishing LLC.

Tablero C.,Technical University of Madrid
Journal of Physical Chemistry C | Year: 2013

The silicon carbide semiconductor forms stable and long-range ordered structures with interest in technology because of their optoelectronic properties, hardness, large thermal conductivity, and chemical stability. The optoelectronic properties can be potentiality improved by the insertion of intermediate states into the energy band gap. We explore this possibility using VIII-group transition metal impurities carrying out first-principles calculations. In some cases, the impurity introduces a deeper band into the host energy band gap for ferromagnetic and antiferromagnetic spin alignments. These intermediate bands could split into two sub-bands through a site deformation around the impurities or a Mott-Hubbard metal-insulator transition. We have extended the study in order to analyze these possibilities. From our results, these effects or a combination of them do not split the bands in the energy band gap. Therefore, these deeper bands open up more photon absorption channels and could therefore increase the solar-light absorption with respect to the host in solar-cell devices. © 2013 American Chemical Society.

Almorox J.,Technical University of Madrid | Bocco M.,National University of Cordoba | Willington E.,National University of Cordoba
Renewable Energy | Year: 2013

Solar radiation is the most important source of renewable energy in the planet; it's important to solar engineers, designers and architects, and it's also fundamental for efficiently determining irrigation water needs and potential yield of crops, among others. Complete and accurate solar radiation data at a specific region are indispensable. For locations where measured values are not available, several models have been developed to estimate solar radiation. The objective of this paper was to calibrate, validate and compare five representative models to predict global solar radiation, adjusting the empirical coefficients to increase the local applicability and to develop a linear model. All models were based on easily available meteorological variables, without sunshine hours as input, and were used to estimate the daily solar radiation at Cañada de Luque (Córdoba, Argentina).As validation, measured and estimated solar radiation data were analyzed using several statistic coefficients. The results showed that all the analyzed models were robust and accurate (R2 and RMSE values between 0.87 to 0.89 and 2.05 to 2.14, respectively), so global radiation can be estimated properly with easily available meteorological variables when only temperature data are available.Hargreaves-Samani, Allen and Bristow-Campbell models could be used with typical values to estimate solar radiation while Samani and Almorox models should be applied with calibrated coefficients. Although a new linear model presented the smallest R2 value (R2=0.87), it could be considered useful for its easy application. The daily global solar radiation values produced for these models can be used to estimate missing daily values, when only temperature data are available, and in hydrologic or agricultural applications. © 2013 Elsevier Ltd.

Bekios-Calfa J.,Catolica del Norte University | Buenaposada J.M.,Rey Juan Carlos University | Baumela L.,Technical University of Madrid
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2011

Emerging applications of computer vision and pattern recognition in mobile devices and networked computing require the development of resource-limited algorithms. Linear classification techniques have an important role to play in this context, given their simplicity and low computational requirements. The paper reviews the state-of-the-art in gender classification, giving special attention to linear techniques and their relations. It discusses why linear techniques are not achieving competitive results and shows how to obtain state-of-the-art performances. Our work confirms previous results reporting very close classification accuracies for Support Vector Machines (SVMs) and boosting algorithms on single-database experiments. We have proven that Linear Discriminant Analysis on a linearly selected set of features also achieves similar accuracies. We perform cross-database experiments and prove that single database experiments were optimistically biased. If enough training data and computational resources are available, SVM's gender classifiers are superior to the rest. When computational resources are scarce but there is enough data, boosting or linear approaches are adequate. Finally, if training data and computational resources are very scarce, then the linear approach is the best choice. © 2011 IEEE.

Mata-Alvarez-Santullano F.,Maritime Accident and Incident Investigation Standing Commission | Souto-Iglesias A.,Technical University of Madrid
Marine Policy | Year: 2013

A number of similar Spanish fishing vessels designed and built after the entry into force of the 1998 fishing effort control regulations -Royal Decree 2287/1998-capsized in a relatively short period of time (2004-2007). The accidents are described and identified herein as a statistical anomaly within the Spanish fleet. The main dimensions and initial stability characteristics of the capsized vessels are compared with those of the vessels decommissioned in order to build the capsized ones, unveiling a reduction in marginal stability. This reduction is linked to the fishing effort control policies and subsequent regulatory framework. The influence of fishing effort control policies on ship safety is discussed. Conclusions and some recommendations are finally presented. © 2012 Elsevier Ltd.

Fernandez V.,Technical University of Madrid | Brown P.H.,University of California at Davis
Frontiers in Plant Science | Year: 2013

The application of agrochemical sprays to the aerial parts of crop plants is an important agricultural practice world-wide. While variable effectiveness is often seen in response to foliar treatments, there is abundant evidence showing the beneficial effect of foliar fertilizers in terms of improving the metabolism, quality, and yields of crops. This mini-review is focused on the major bottlenecks associated with the uptake and translocation of foliar-applied nutrient solutions. A better understanding of the complex scenario surrounding the ultimate delivery of foliar-applied nutrients to sink cells and organs is essential for improving the effectiveness and performance of foliar fertilizers. © 2013 Fernández and Brown.

Negreanu M.,Complutense University of Madrid | Tello J.I.,Technical University of Madrid
Nonlinearity | Year: 2013

In this paper, we study a system of partial differential equations describing the evolution of a population under chemotactic effects with non-local reaction terms. We consider an external application of chemoattractant in the system and study the cases of one and two populations in competition. By introducing global competitive/cooperative factors in terms of the total mass of the populations, we obtain, for a range of parameters, that any solution with positive and bounded initial data converges to a spatially homogeneous state with positive components. The proofs rely on the maximum principle for spatially homogeneous sub- and super-solutions. © 2013 IOP Publishing Ltd & London Mathematical Society.

Bombardelli C.,Technical University of Madrid
Celestial Mechanics and Dynamical Astronomy | Year: 2013

The paper deals with the problem of impulsive collision avoidance between two colliding objects in three dimensions and assuming elliptical Keplerian orbits. Closed-form analytical expressions are provided that accurately predict the relative dynamics of the two bodies in the encounter b-plane following an impulsive delta-V manoeuvre performed by one object at a given orbit location prior to the impact and with a generic three-dimensional orientation. After verifying the accuracy of the analytical expressions for different orbital eccentricities and encounter geometries the manoeuvre direction that maximises the miss distance is obtained numerically as a function of the arc length separation between the manoeuvre point and the predicted collision point. The provided formulas can be used for high-accuracy instantaneous estimation of the outcome of a generic impulsive collision avoidance manoeuvre and its optimisation. © 2013 Springer Science+Business Media Dordrecht.

Tablero C.,Technical University of Madrid
Progress in Photovoltaics: Research and Applications | Year: 2013

The electronic properties and the low environmental impact of Cu 3 BiS 3 make this compound a promising material for low-cost thin film solar cell technology. From the first principles, the electronic properties of the isoelectronic substitution of S by O in Cu 3 BiS 3 have been obtained using two different exchange-correlation potentials. This compound has an acceptor level below the conduction band, which modifies the opto-electronic properties with respect to the host semiconductor. In order to analyze a possible efficiency increment with respect to the host semiconductor, we have calculated the maximum efficiency of this photovoltaic absorber material. Copyright © 2012 John Wiley & Sons, Ltd. From first principles, the electronic properties of the isoelectronic substitution of S by O in Cu3BiS3 have been obtained. The acceptor energy levels in the gap form a band in the alloying limit. Using the first-principles results, we have estimated the maximum efficiency of this photovoltaic absorber material. Copyright © 2012 John Wiley & Sons, Ltd.

Castro C.,Technical University of Madrid
ESAIM - Control, Optimisation and Calculus of Variations | Year: 2013

We consider the linear wave equation with Dirichlet boundary conditions in a bounded interval, and with a control acting on a moving point. We give sufficient conditions on the trajectory of the control in order to have the exact controllability property. © 2012 EDP Sciences, SMAI.

Barrero-Gil A.,Technical University of Madrid
Engineering Analysis with Boundary Elements | Year: 2013

In this paper we present a simple modification of the Method of Fundamental Solutions applied to axisymmetric Stokes problems, in which the source and collocation points are made coincident. It is based on a special treatment of the singular kernel evaluations, where spatially averaged quantities are considered by using auxiliary (or fictitious) Stokeslets. The method is still truly meshless and very easy to implement. The developed method is tested on several numerical experiments. Satisfactory results are obtained. © 2012 Elsevier Ltd.

Bejar Haro B.,Ecole Polytechnique Federale de Lausanne | Zazo S.,Technical University of Madrid | Palomar D.P.,Hong Kong University of Science and Technology
IEEE Transactions on Signal Processing | Year: 2014

Energy efficiency is a major design issue in the context of Wireless Sensor Networks (WSN). If the acquired data is to be sent to a far-away base station, collaborative beamforming performed by the sensors may help to distribute the communication load among the nodes and to reduce fast battery depletion. However, collaborative beamforming techniques are far from optimality and in many cases we might be wasting more power than required. We consider the issue of energy efficiency in beamforming applications. Using a convex optimization framework, we propose the design of a virtual beamformer that maximizes the network lifetime while satisfying a pre-specified Quality of Service (QoS) requirement. We derive both centralized and distributed algorithms for the solution of the problem using convex optimization and consensus algorithms. In order to account for other sources of battery depletion different from that of communications beamforming, we consider an additional random energy term in the consumption model. The formulation then switches to a probabilistic design that generalizes the deterministic case. Conditions under which the general problem is convex are also provided. © 2013 IEEE.

Cabellos O.,Technical University of Madrid
Science and Technology of Nuclear Installations | Year: 2013

The aim of this work is to present the Exercise I-1b "pin-cell burn-up benchmark" proposed in the framework of OECD LWR UAM. Its objective is to address the uncertainty due to the basic nuclear data as well as the impact of processing the nuclear and covariance data in a pin-cell depletion calculation. Four different sensitivity/uncertainty propagation methodologies participate in this benchmark (GRS, NRG, UPM, and SNU&KAERI). The paper describes the main features of the UPM model (hybrid method) compared with other methodologies. The requested output provided by UPM is presented, and it is discussed regarding the results of other methodologies. © 2013 O. Cabellos.

Diez-Pascual A.M.,CSIC - Institute of Polymer Science and Technology | Naffakh M.,Technical University of Madrid
Materials | Year: 2013

Carbon fiber (CF)-reinforced high-temperature thermoplastics such as poly(phenylene sulphide) (PPS) are widely used in structural composites for aerospace and automotive applications. The porosity of CF-reinforced polymers is a very important topic for practicalapplications since there is a direct correlation between void content and mechanical properties. In this study, inorganic fullerene-like tungsten disulphide (IF-WS2) lubricant nanoparticles were used to manufacture PPS/IF-WS2/CF laminates via melt-blending and hot-press processing, and the effect of IF-WS2 loading on the quality, thermal and mechanical behaviour of the hybrid composites was investigated. The addition of IF-WS2 improved fiber impregnation, resulting in lower degree of porosity and increased delamination resistance, compression and flexural properties; their reinforcement effect was greater at temperatures above the glass transition (Tg). IF-WS2 contents higher than 0.5 wt % increased Tg and the heat deflection temperature while reduced the coefficient of thermal expansion. The multiscale laminates exhibited higher ignition point and notably reduced peak heat release rate compared to PPS/CF. The coexistence of micro- and nano-scale fillers resulted in synergistic effects that enhanced the stiffness, strength, thermal conductivity and flame retardancy of the matrix. The results presented herein demonstrate that the IF-WS2 arevery promising nanofillers to improve the thermomechanical properties of conventional thermoplastic/CF composites. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Iriarte G.F.,Technical University of Madrid
Microsystem Technologies | Year: 2010

This work describes the micro-fabrication process developed to manufacture nano-interdigital transducers (nano-IDTs) to be used in surface acoustic wave applications. The combination of electron-beam (e-beam) lithography and lift-off process is shown to be effective in fabricating IDT finger patterns with a line width below 100 nm and good yield. It is also shown how a very thin organic anti-static layer can be used to avoid charge accumulation on the resist layer during e-beam lithography, which is easy to occur on insulating piezoelectric substrates and results in e-beam deflection. However, it is also shown how the use of this anti-static layer is not required with the insulating piezoelectric layer resting on a semiconducting substrate such as highly doped silicon. The effect of the e-beam dose on insulating and semiconducting layers is also discussed. © 2010 Springer-Verlag.

Gomez-del-Campo M.,Technical University of Madrid
Irrigation Science | Year: 2013

Maximum production in hedgerow olive orchards is likely not achieved with maximum evapotranspiration over the long term. Thus, regulated deficit irrigation (RDI) should be considered as a management option. Four irrigation treatments were evaluated during the summer, when olive is most drought resistant. Control (CON) was irrigated to maintain the root zone close to field capacity. Severe water deficit was applied by irrigating 30% CON from the end of fruit drop to end July (DI-J) and from end July until beginning of oil synthesis (DI-A). Less severe water deficit was applied during July and August (DI-JA) by irrigating 50% CON. Flowering, fruiting, abscission, fruit development, fresh and dry weight of fruits, and oil production were evaluated. There were not significant differences in number of buds initiated, number of fruits per inflorescence and fruit drop. Oil production was significantly different between irrigation treatments in all experimental years. CON produced more oil and fruit with higher oil % than DI-A and DI-JA. Oil production of DI-J was not significantly reduced compared with CON and oil% was greater. DI-J was the most effective RDI strategy; with 16% less applied water relative to CON. Average loss in oil production of 8% was not significantly different to CON. While DI-JA saved most water (27%), oil production was reduced by 15%. Greatest loss in oil production (21%) was observed in DI-A with water saving of 22%. © 2011 Springer-Verlag.

Riaza R.,Technical University of Madrid
International Journal of Bifurcation and Chaos | Year: 2011

The recent discovery of a physical device behaving as a memristor has driven a lot of attention to memristive systems, which are likely to play a relevant role in electronics in the near future, especially at the nanometer scale. The derivation of explicit ODE models for these systems is important because it opens a way for the study of the dynamics of general memristive circuits, including e.g. stability aspects, oscillations, bifurcations or chaotic phenomena. We tackle this problem as a reduction of implicit ODE (differential-algebraic) models, and show how tree-based approaches can be adapted in order to accommodate memristors. Specifically, we prove that the derivation of a tree-based explicit ODE model is feasible for strictly passive memristive systems under broad coupling effects and without a priori current/voltage control assumptions on tree/cotree elements. Our framework applies in particular to topologically degenerate circuits and accommodates a wide class of controlled sources. We also discuss a quasilinear reduction of nonpassive problems, which do not admit an explicit ODE description in the presence of singularities; some related bifurcations are addressed in this context. © 2011 World Scientific Publishing Company.

Lopez Mozo A.,Technical University of Madrid
Nexus Network Journal | Year: 2011

Oval forms have been used in architecture since antiquity as arch elevations, cross and horizontal sections of vaults, profiles of arches and building plan layouts. The present paper aims to approach the knowledge and application of oval layouts for any given proportion, that is, those which fit a particular place, either as the span and height of an arch or vault, or as the length and width of a plan, by comparing written sources and built heritage. This is, on one hand, research on architectural treatises since the sixteenth century in order to find where the geometrical construction for this kind of layouts appears for the first time; and on the other, a study of the application of ovals in the vaults of the Escorial (1563-1584). Although 1712 could be considered the date of the first published geometrical construction for an oval to fit a given place, this work hypothesizes the possible application of a layout of this type in the construction of the Escorial. © 2011 Kim Williams Books, Turin.

Alonso-Sanz R.,Technical University of Madrid
International Journal of Bifurcation and Chaos | Year: 2011

When memory is endowed in the dynamics of the logistic map, its parameter may reach, without diverging, values than are greater than its upper limit in the ahistoric, conventional formulation. A numerical study is made in this study on the dynamics of the logistic map with memory mT: xT+1 = λmT(1-mT), when λ > 4.0 or λ < -2.0. © 2011 World Scientific Publishing Company.

Riaza R.,Technical University of Madrid | Tischendorf C.,University of Cologne
International Journal of Circuit Theory and Applications | Year: 2011

In this paper we present several semistate or differential-algebraic models arising in nodal analysis of nonlinear circuits including memristors. The goal is to characterize the tractability index of these models under strict passivity assumptions, a key issue for the numerical simulation of circuit dynamics. We show that the main model, which combines memristors' fluxes and charges, is index two. From a technical point of view, this result is based on the use of a projector along the image of the leading matrix, in contrast to previous index analyses. For charge-controlled memristors, the elimination of fluxes yields an index one system in topologically nondegenerate circuits, and an index two model otherwise. Analogous results are also proved to hold for flux-controlled memristors. Our framework accommodates coupling effects among resistors, memristors, capacitors and inductors. Copyright © 2010 John Wiley & Sons, Ltd.

Torres M.A.,Technical University of Madrid | Torres M.A.,University of North Carolina at Chapel Hill
Physiologia Plantarum | Year: 2010

Production of reactive oxygen species (ROS) is a hallmark of successful recognition of infection and activation of plant defenses. ROS play multifaceted signaling functions mediating the establishment of multiple responses and can act as local toxins. Controversy surrounds the origin of these ROS. Several enzymatic mechanisms, among them a plasma membrane NADPH oxidase and cell wall peroxidases, can be responsible for the ROS detected in the apoplast. However, high levels of ROS from metabolic origins and/or from downregulation of ROS-scavenging systems can also accumulate in different compartments of the plant cell. This compartmentalization could contribute to the specific functions attributed to ROS. Additionally, ROS interact with other signals and phytohormones, which could explain the variety of different scenarios where ROS signaling plays an important part. Interestingly, pathogens have developed ways to alter ROS accumulation or signaling to modify plant defenses. Although ROS have been mainly associated with pathogen attack, ROS are also detected in other biotic interactions including beneficial symbiotic interactions with bacteria or mycorrhiza, suggesting that ROS production is a common feature of different biotic interactions. Here, we present a comprehensive review describing the newer views in ROS signaling and function during biotic stress. Copyright © Physiologia Plantarum 2009.

Pearce D.,Technical University of Madrid | Valverde A.,University of Malaga
Journal of Computer and System Sciences | Year: 2012

Even within a single knowledge representation system there are often many different ways to model a given domain and formalise a reasoning problem specified over the domain. In particular, two knowledge descriptions can be semantically equivalent even if they are expressed in quite different languages or vocabularies. This paper proposes and studies a concept of synonymy that applies to equivalent theories formulated in distinct vocabularies. We suggest a set of general desiderata or criteria of adequacy that any reasonable synonymy concept should satisfy. We then analyse a specific concept of synonymy within answer set programming (ASP), a framework that is currently being applied with success in many areas of knowledge technology. We characterise this concept in different ways, show that it satisfies the prescribed criteria of adequacy, and illustrate how it can be applied to a sample problem arising in knowledge representation and reasoning. As a logical framework we use quantified equilibrium logic based on a first-order version of the logic of here-and-there. This serves as an adequate formal foundation for ASP and allows us to obtain a logical account of the synonymy relation. © 2011 Elsevier Inc. All rights reserved.

Prieto J.L.,Technical University of Madrid
Journal of Non-Newtonian Fluid Mechanics | Year: 2016

This paper presents a Compactly-Supported, Radial Basis Functions (CSRBFs) method for building the polymer, extra-stress tensor arising in micro-macro simulations of particle-based, viscoelastic, free-surface flows. The extra-stress tensor is reconstructed on the domain and evaluated at the mesh-nodes by CSRBFs using the known values of the tensor at each of the ensembles of dumbbells which carry the molecular information of the non-Newtonian fluid, circumventing the need for ad-hoc methodologies entailing repositioning/creation/destruction of polymer particles. The macroscopic equations and free-surface representation are then discretized using available finite element techniques. The versatility, computational performance and potential of the CSRBF technique is illustrated with simulations of 2 d Newtonian bubbles rising in a viscoelastic fluid using the Hooke and FENE kinetic models with highly refined meshes under strong density and viscosity ratios. The results show the ability of the method to accurately build the polymer stress tensor in flows featuring intense viscoelastic effects, while opening the way for adaptive, isotropic or anisotropic, mesh refinement procedures. © 2015 Elsevier B.V.

Tablero C.,Technical University of Madrid
Computational Materials Science | Year: 2010

The O-doped ZnTe (ZnTe1-xOx) alloys present induce levels through O doping into the host semiconductor gap. ZnTe usually crystallizes in the zinc-blend structure and ZnO in the wurtzite structure under normal conditions. Therefore two possible ZnTe1- xOx phases may coexist, although in different proportions, depending on experimental growth conditions. We present total energy calculations and analyze some of their electronic properties with respect to: the two ordered wurtzite and zinc-blende structures, the concentration (x from 0.0078 to 0.5), the localized basis set (from single-zeta to quadruple-zeta with polarization basis sets), and the variation of the ionization levels with x and with the distance O-Zn. © 2010 Elsevier B.V. All rights reserved.

Canavarro D.,University of Evora | Chaves J.,Technical University of Madrid | Collares-Pereira M.,University of Evora
Solar Energy | Year: 2013

Parabolic Trough concentrators are the predominant Concentrated Solar Power (CSP) technology today. However this technology is facing substantial challenge from the need to reduce costs and/or increase performance. This paper address this challenge by exploring the room left from the fact this type of optic falls short from the theoretical limits of concentration, proposing a new solution enabling the design of larger troughs with higher concentration or larger acceptance angles, through the use of second stage concentration of a novel type. This new optic is designed with the Simultaneous Multiple Surface (SMS) method for two reflective (X) surfaces (XX SMS) Winston et al. (2005) - of which the primary is approximately parabolic - using a different assignation of the edge rays in order to significantly reduce the Fresnel losses around the glass cover of the evacuated tubes commonly used in CSP applications. To analyze the merits of this new optic, two different comparisons are made. The first one with the SMS Helmet concentrator through the calculation of CAP (Concentration-Acceptance Product) and the second one with a commercial Parabolic Trough concentrator, using an estimate of the total amount of collected energy (kW h) for one particular location, Faro (Portugal). The paper ends with a discussion of the results obtained, their impact and possible applications in the future. © 2013 Elsevier Ltd.

Moratiel R.,Technical University of Madrid | Martinez-Cob A.,CSIC - Aula Dei Experimental Station
Irrigation Science | Year: 2012

The evapotranspiration (ET c) of a table grape vineyard (Vitis vinifera, cv. Red Globe) trained to a gable trellis under netting and black plastic mulching was determined under semiarid conditions in the central Ebro River Valley during 2007 and 2008. The netting was made of high-density polyethylene (pores of 12 mm 2) and was placed just above the ground canopy about 2.2 m above soil surface. Black plastic mulching was used to minimize soil evaporation. The surface renewal method was used to obtain values of sensible heat flux (H) from high-frequency temperature readings. Later, latent heat flux (LE) values were obtained by solving the energy balance equation. For the May-October period, seasonal ET c was about 843 mm in 2007 and 787 mm in 2008. The experimental weekly crop coefficients (K cexp) fluctuated between 0.64 and 1.2. These values represent crop coefficients adjusted to take into account the reduction in ET c caused by the netting and the black plastic mulching. Average K cexp values during mid- and end-season stages were 0.79 and 0.98, respectively. End-season K cexp was higher due to combination of factors related to the precipitation and low ET o conditions that are typical in this region during fall. Estimated crop coefficients using the Allen et al. (1998) approach adjusting for the effects of the netting and black plastic mulching (K cFAO) showed a good agreement with the experimental K cexp values. © 2011 Springer-Verlag.

Medina-Roldan E.,Lancaster University | Paz-Ferreiro J.,Lancaster University | Paz-Ferreiro J.,Technical University of Madrid | Bardgett R.D.,Lancaster University
Agriculture, Ecosystems and Environment | Year: 2012

We evaluated the impact of 7 years of grazing exclusion on vegetation and belowground properties related to soil carbon (C) and nitrogen (N) cycling in grazed, upland grassland in northern England. For this, we compared a landscape-level, moorland restoration project (grazing exclusion) with adjacent continuously grazed acidic grasslands to test whether changes in vegetation composition after restoration impacted on soil properties including soil C storage. Grazing exclusion significantly increased the proportion of dwarf-shrubs at the expense of graminoids. Despite high seasonal variability, this change in vegetation was associated with increased plant litter mass, soil moisture content and the ratio of dissolved organic to inorganic N, and reductions in rates of ammonium mineralisation, soil microbial activity, and microbial biomass N. Our observations suggest that grazing-exclusion as a restoration tool for upland habitats results in a slowing down of rates of C and N cycling. However, as yet, this has had no detectable impact on total C and N stocks in surface soil. Whereas increases in soil C and N stocks might be expected in the longer term, our results suggest that a certain level of grazing is compatible with the provision of ecosystem services such as soil C storage under traditional upland farming practices. © 2012 Elsevier B.V.

Riaza R.,Technical University of Madrid
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2013

This paper presents a theoretical framework intended to accommodate circuit devices described by characteristics involving more than two fundamental variables. This framework is motivated by the recent appearance of a variety of so-called mem-devices in circuit theory, and makes it possible to model the coexistence of memory effects of different nature in a single device. With a compact formalism, this setting accounts for classical devices and also for circuit elements which do not admit a two-variable description. Fully nonlinear characteristics are allowed for all devices, driving the analysis beyond the framework of Chua and Di Ventra We classify these fully nonlinear circuit elements in terms of the variables involved in their constitutive relations and the notions of the differential- and the state-order of a device. We extend the notion of a topologically degenerate configuration to this broader context, and characterize the differential-algebraic index of nodal models of such circuits. Additionally, we explore certain dynamical features of mem-circuits involving manifolds of non-isolated equilibria. Related bifurcation phenomena are explored for a family of nonlinear oscillators based on mem-devices. © 2004-2012 IEEE.

Haemmerle R.,Technical University of Madrid
Theory and Practice of Logic Programming | Year: 2012

Abstract Confluence is a fundamental property of Constraint Handling Rules (CHR) since, as in other rewriting formalisms, it guarantees that the computations are not dependent on rule application order, and also because it implies the logical consistency of the program declarative view. In this paper we are concerned with proving the confluence of non-terminating CHR programs. For this purpose, we derive from van Oostrom's decreasing diagrams method a novel criterion on CHR critical pairs that generalizes all preexisting criteria. We subsequently improve on a result on the modularity of CHR confluence, which permits modular combinations of possibly non-terminating confluent programs, without loss of confluence. © Cambridge University Press 2012.

Olmos J.M.,Prointer Ingenieria | Astiz M.A.,Technical University of Madrid
Engineering Structures | Year: 2013

With the development of high-speed railways in the last decade, the dynamic behaviour of trains and bridges has been studied more thoroughly. However, it is difficult to find papers in the scientific literature about the lateral response of high-speed trains travel over long viaducts with high piers. In order to evaluate the riding comfort or vehicle dynamic response of a train over this kind of bridges, an efficient nonlinear dynamic interaction model of the train-track-bridge system was developed and checked. In that model, a three-dimensional multi-body train and a finite element bridge and track system are considered. Ballast stiffness and rail flexibility are taken into account in the finite element model. For reproducing the interaction between wheel and rail, a simplified nonlinear creep contact model has been included. In this study, track irregularities and wheel-hunting movement are considered as the system lateral excitation. The influence of pier height on the response of train and bridge is also studied. Continuous bridges, straight and constant section deck viaducts with variable height and tapered piers are the structures which have been considered. The height of the tested viaduct ranges between 60 and 120. m. The results of this study show that train behaviour is in accordance with riding comfort standards. And, although some bridge response values obtained are not allowed in the currently recognized train traffic safety standards of bridges, they can be easily improved. © 2013 Elsevier Ltd.

Calle-Sanchez J.,Technical University of Madrid | Fernandez-Duran A.,Alcatel - Lucent
Bell Labs Technical Journal | Year: 2013

Long Term Evolution (LTE) is considered to be the natural evolution for the current Global System for Mobile Communications-Railways (GSM-R) in high speed railway environments, not only for its technical advantages and increased performance, but also due to the current evolution of public communication systems. In railway environments, mission critical services, operation assistance services, and passenger services must be supported by reliable mobile communication systems. Reliability and availability are key concerns for railway operators and as a consequence, railway operators are usually conservative adopters of information and communication technologies (ICT). This paper describes the feasibility of LTE as a successor to GSM-R for new railway mobile communication systems. We identify key features of LTE as a technology and analyze its ability to support both the migration of current railway services and the provisioning of potential future ones. We describe the key challenges to address specific requirements for railway communication services including the provisioning of voice service in LTE networks, handover performance, multicast multimedia transmission, and the provisioning of group communications service and railway emergency calls. © 2013 Alcatel-Lucent.

Tello J.I.,Technical University of Madrid | Winkler M.,University of Paderborn
Nonlinearity | Year: 2012

We study a system of three partial differential equations modelling the spatiotemporal behaviour of two competitive populations of biological species both of which are attracted chemotactically by the same signal substance. More precisely, we consider the initial-boundary value problem for under homogeneous Neumann boundary conditions in a bounded domain ω ⊂. Rn, n ≥ 1, with smooth boundary. When 0 ≤ a 1 < 1 and 0 ≤ a 2 < 1, this system possesses a uniquely determined spatially homogeneous positive equilibrium (u*, v*). We show that given any such a 1 and a 2 and any positive diffusivities d 1 and d 2 and crossdiffusivities χ 1 and χ 2, this steady state is globally asymptotically stable within a certain nonempty range of the logistic growth coefficients μ 1 and μ 2. © 2012 IOP Publishing Ltd & London Mathematical Society.

Munoz M.,CSIC - National Center of Microelectronics | Prieto J.L.,Technical University of Madrid
Nature Communications | Year: 2011

Nanofabrication has allowed the development of new concepts such as magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls on magnetic nanostripes. One of the issues that has to be solved before devices can meet the market demands is the stochastic behaviour of the domain wall movement in magnetic nanostripes. Here we show that the stochastic nature of the domain wall motion in permalloy nanostripes can be suppressed at very low fields (0.6-2.7 Oe). We also find different field regimes for this stochastic motion that match well with the domain wall propagation modes. The highest pinning probability is found around the precessional mode and, interestingly, it does not depend on the external field in this regime. These results constitute an experimental evidence of the intrinsic nature of the stochastic pinning of domain walls in soft magnetic nanostripes. © 2011 Macmillan Publishers Limited. All rights reserved.

Camara A.,Technical University of Madrid | Ruiz-Teran A.M.,Imperial College London | Stafford P.J.,Imperial College London
Earthquake Engineering and Structural Dynamics | Year: 2013

SUMMARY: Under-deck cable-stayed bridges are very effective structural systems for which the strong contribution of the stay cables under live loading allows for the design of very slender decks for persistent and transient loading scenarios. Their behaviour when subjected to seismic excitation is investigated herein and a set of design criteria are presented that relate to the type and arrangement of bearings, the number and configuration of struts, and the transverse distribution of stay cables. The nonlinear behaviour of these bridges when subject to both near-field and far-field accelerograms has been thoroughly investigated through the use of incremental dynamic analyses. An intensity measure that reflects the pertinent contributions to response when several vibration modes are activated was proposed and is shown to be effective for the analysis of this structural type. The under-deck cable-stay system contributes in a very positive manner to reducing the response when the bridges are subject to very strong seismic excitation. For such scenarios, the reduction in the stiffness of the deck because of crack formation, when prestressed concrete decks are used, mobilises the cable system and enhances the overall performance of the system. Sets of natural accelerograms that are compliant with the prescriptions of Eurocode 8 were also applied to propose a set of design criteria for this bridge type in areas prone to earthquakes. Particular attention is given to outlining the optimal strategies for the deployment of bearings. © 2012 John Wiley & Sons, Ltd.

Garcia-Pelayo R.,Technical University of Madrid
Journal of Mathematical Physics | Year: 2012

We give a method to solve the isotropic random flight in arbitrary dimension and show that, when the dimension is odd, it leads to a piecewise polynomial expression for the probability density. The method is based on the fact that the projection of an isotropic function has an inverse and on the fact that the convolution commutes with the projection and the inverse projection. In order to develop this method the Abel transform and its inverse are extended. By comparing with the expression for the isotropic random flight obtained using the convolution theorem, some integrals of Bessel functions can be expressed as piecewise polynomials. The expressions for the five-dimensional case for 2, 3, and 4 steps are found explicitly. Although the main result derived from this method concerns odd dimensions, it also yields an analytical result in the four-dimensional isotropic random flight, which is derived here. The results of this article can also be considered as results on the convolution with itself of an isotropic probability density whose support is the surface of a sphere. © 2012 American Institute of Physics.

Alonso-Sanz R.,Technical University of Madrid
Quantum Information Processing | Year: 2013

The dynamics of a spatial quantum formulation of the iterated battle of the sexes game is studied in this work. The game is played in the cellular automata manner, i.e., with local and synchronous interaction. The effect of spatial structure is assessed when allowing the players to adopt quantum strategies that are no restricted to any particular subset of the possible strategies. © 2012 Springer Science+Business Media New York.

Luque B.,Technical University of Madrid
Chaos (Woodbury, N.Y.) | Year: 2012

Time series are proficiently converted into graphs via the horizontal visibility (HV) algorithm, which prompts interest in its capability for capturing the nature of different classes of series in a network context. We have recently shown [B. Luque et al., PLoS ONE 6, 9 (2011)] that dynamical systems can be studied from a novel perspective via the use of this method. Specifically, the period-doubling and band-splitting attractor cascades that characterize unimodal maps transform into families of graphs that turn out to be independent of map nonlinearity or other particulars. Here, we provide an in depth description of the HV treatment of the Feigenbaum scenario, together with analytical derivations that relate to the degree distributions, mean distances, clustering coefficients, etc., associated to the bifurcation cascades and their accumulation points. We describe how the resultant families of graphs can be framed into a renormalization group scheme in which fixed-point graphs reveal their scaling properties. These fixed points are then re-derived from an entropy optimization process defined for the graph sets, confirming a suggested connection between renormalization group and entropy optimization. Finally, we provide analytical and numerical results for the graph entropy and show that it emulates the Lyapunov exponent of the map independently of its sign.

De Paz J.F.,University of Salamanca | Bajo J.,Technical University of Madrid | Lopez V.F.,University of Salamanca | Corchado J.M.,University of Salamanca
Information Sciences | Year: 2013

The application of information technology in the field of biomedicine has become increasingly important over the last several years. This study presents the Intelligent Biomedic Organizations (IBOs) model, an intelligent dynamic architecture for knowledge discovery in biomedical databases. It involves an organizational model specially designed to support medical personnel in their daily tasks and to establish an innovative intelligent system to make classifications and predictions with huge volumes of information. IBO is based on a multi-agent architecture with Web service integration capability. The core of the system is a type of agent that integrates a novel strategy based on a case-based planning mechanism for automatic reorganization. This agent proposes a new reasoning agent model, where the complex processes are modeled as external services. In this sense, the agents act as coordinators of Web services that implement the four stages of the case-based planning cycle. The multi-agent system has been implemented in a real scenario to classify leukemia patients, and the classification strategy includes services such as a novel ESOINN neural network and statistical methods to analyze patient data. The results obtained are presented within this paper and demonstrate the effectiveness of the proposed organizational model. © 2012 Elsevier Inc. All rights reserved.

Alonso-Sanz R.,Technical University of Madrid
Journal of Cellular Automata | Year: 2013

The effectiveness of memory of delay type in solving the density classification task in cellular automata is assessed in this study. © 2013 Old City Publishing, Inc.

Vazquez Espi M.,Technical University of Madrid
Structural and Multidisciplinary Optimization | Year: 2013

Sokół and Rozvany (Struct Multidisc Optim doi: 10.1007/s00158-012-0786-4, 2012) have published a very remarkable paper showing benchmarks solutions for the so named "two load problems". Although the Writer strongly believes that the Authors have reached the very best solutions, he thinks that some details of the paper are worth of a few comments and questions. As a matter of fact, the Writer is personally concerned as his own benchmarks for this problem - from his PhD. dissertation of 1994 - have been at last improved by those of the Authors. © 2012 Springer-Verlag.

Read J.,Charles III University of Madrid | Martino L.,Charles III University of Madrid | Luengo D.,Technical University of Madrid
Pattern Recognition | Year: 2014

Multi-dimensional classification (MDC) is the supervised learning problem where an instance is associated with multiple classes, rather than with a single class, as in traditional classification problems. Since these classes are often strongly correlated, modeling the dependencies between them allows MDC methods to improve their performance - at the expense of an increased computational cost. In this paper we focus on the classifier chains (CC) approach for modeling dependencies, one of the most popular and highest-performing methods for multi-label classification (MLC), a particular case of MDC which involves only binary classes (i.e., labels). The original CC algorithm makes a greedy approximation, and is fast but tends to propagate errors along the chain. Here we present novel Monte Carlo schemes, both for finding a good chain sequence and performing efficient inference. Our algorithms remain tractable for high-dimensional data sets and obtain the best predictive performance across several real data sets. © 2013 Elsevier Ltd. All rights reserved.

Bau G.,University of Pisa | Bombardelli C.,Technical University of Madrid
Astronomical Journal | Year: 2014

We propose two time elements for the orbit propagator named Dromo. One is linear and the other constant with respect to the independent variable, which coincides with the osculating true anomaly in the Keplerian motion. They are defined from a generalized Kepler's equation written for negative values of the total energy and, unlike the few existing time elements of this kind, are free of singularities. To our knowledge it is the first time that a constant time element is associated with a second-order Sundman time transformation. Numerical tests to assess the performance of the Dromo method equipped with a time element show the remarkable improvement in accuracy for the perturbed bounded motion around the Earth compared to the case in which the physical time is a state variable. Moreover, the method is competitive with and even better than other efficient sets of elements. Finally, we also derive a time element for a null and positive total energy. © 2014. The American Astronomical Society. All rights reserved..

Llaves A.,Technical University of Madrid | Kuhn W.,University of California at Santa Barbara
International Journal of Geographical Information Science | Year: 2014

Time series of observations reflect the status of environmental properties. Variations in these properties can be considered as events when they potentially affect the stability of the monitored environment. Organisations dedicated to analyse environmental change use institutionalised descriptions of events to define the observable conditions under which events happen. This also applies to the methods used to classify and model changes in environmental monitoring. The heterogeneity of representations often causes interoperability problems when such communities exchange geospatial information. To enhance interoperability among diverse communities, it is required to develop models that do not restrict the representation of events, but allow integrating different perspectives on changes in the environment. The goal of the Event Abstraction Layer is to facilitate the analysis and integration of geosensor data by inferring events from time series of observations. For the analysis of geosensor data, we use event processing to detect event patterns in time series of observations. Spatio-temporal properties of the event are inferred from the geosensor location and the observation timestamps. For the data integration, we represent event-related information extracted from multiples sources under a common event model. Additionally, domain knowledge is modelled in a multilevel ontology structure. © 2014 Taylor & Francis.

Ajisaka S.,University of Chile | Barra F.,University of Chile | Mejia-Monasterio C.,Technical University of Madrid | Prosen T.,University of Ljubljana
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We propose a model of nonequilibrium quantum transport of particles and energy in a system connected to mesoscopic Fermi reservoirs (mesoreservoir). The mesoreservoirs are in turn thermalized to prescribed temperatures and chemical potentials by a simple dissipative mechanism described by the Lindblad equation. As an example, we study transport in monoatomic and diatomic chains of noninteracting spinless fermions. We show numerically the breakdown of the Onsager reciprocity relation due to the dissipative terms of the model. © 2012 American Physical Society.

Barakat R.,Technical University of Madrid
British journal of sports medicine | Year: 2013

To examine the effect of regular moderate-intensity exercise (three training sessions/week) on the incidence of gestational diabetes mellitus (GDM, primary outcome). We also examined if the exercise intervention modifies the association between GDM and birth weight and risk of macrosomia, gestational age, risk of caesarean delivery and maternal weight gain (secondary outcomes). We randomly assigned 510 healthy gravida to either an exercise intervention or a usual care (control) group (n=255 each). The exercise programme focused on moderate-intensity resistance and aerobic exercises (three times/week, 50-55 min/session). GDM diabetes was diagnosed according to the WHO criteria and the International Association for Diabetes in Pregnancy Study Group (IADPSG). The intervention did not reduce the risk of developing GDM (OR 0.84, 95% CI 0.50 to 1.40) when using the WHO criteria. We observed that the intervention reduced by 58% the GDM-related risk (WHO criteria) of having a newborn with macrosomia (OR 1.76, 95% CI 0.04 to 78.90 vs 4.22, 95% CI 1.35 to 13.19) in exercise and control groups, respectively), and by 34% the GDM-related risk of having acute and elective caesarean delivery (OR 1.30, 95% CI 0.44 to 3.84 vs 1.99, 95% CI 0.98 to 4.06 in exercise and control groups, respectively). Gestational age was similar across the treatment groups (control, exercise) and GDM category (GDM or non-GDM), and maternal weight gain was ∼12% lower in the exercise group independent of whether women developed GDM. The results were similar when the IADPSG criteria were used instead. Regular moderate-intensity exercise performed over the second-third trimesters of pregnancy can be used to attenuate important GDM-related adverse outcomes.

Corcoles J.,Autonomous University of Madrid | Gonzalez M.A.,Technical University of Madrid
IEEE Transactions on Antennas and Propagation | Year: 2012

A novel procedure to thin an antenna array which synthesizes a desired pattern with the minimum number of active elements is introduced. The proposed method yields both the active elements and their corresponding excitations of a thinned array having the minimum number of active elements needed to meet several prescribed design specifications of the radiated farfield pattern. Specifications such as achieving a minimum gain, obtaining a pattern with a maximum allowable sidelobe level or synthesizing a shaped beam pattern confined into a mask are considered. Null field directions can also be added. In order to carry out the thinning, a genetic algorithm is used, while computing the excitations is carried out through linear or quadratic programming. The procedure incorporates the generalized scattering matrix analysis of an array made up of elements whose radiated field can be expressed as a spherical mode expansion, thus taking all electromagnetic effects inherently into account. Therefore, since the presence of an element can substantially alter the array features because of mutual coupling, two types of thinning are considered: removing elements or turning them off. Numerical results of arrays made up of isotropic sources, dielectric resonator antennas and microstrip patch antennas are presented. © 2012 IEEE.

Alonso-Sanz R.,Technical University of Madrid
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2012

The dynamics of a spatial quantum formulation of the iterated battle of the sexes game is studied in this work. The game is played in the cellular automata manner, i.e. with local and synchronous interaction. The effect of spatial structure is assessed in the quantum versus quantum players contest as well as in the unfair quantum versus classical players contest. The case of partial entangling is also scrutinized. © 2012 The Royal Society.

Tablero C.,Technical University of Madrid
Thin Solid Films | Year: 2012

The optoelectronic properties of Cu 2ZnSnS 4 and environmental considerations have attracted significant interest for photovoltaics. Using first-principles, we analyze the possible improvement of this material as a photovoltaic absorber via the isoelectronic substitution of S with O atoms. The evolution of the acceptor level is analyzed with respect to the atomic position of the nearest neighbors of the O atom. We estimate the maximum efficiency of this compound when used as a light absorber. The presence of the sub-band gap level below the conduction band could increases the solar-energy conversion with respect to the host. © 2012 Elsevier B.V. All rights reserved.

Iriarte G.F.,Technical University of Madrid
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films | Year: 2010

Aluminum nitride (AlN) thin films deposited on high-vacuum systems without substrate heating generally exhibit a poor degree of c -axis orientation. This is due to the nonequilibrium conditions existing between the energy of the sputtered particles and the energy at the substrate surface. The application of substrate bias or substrate temperature is known to improve the adatom mobility by delivering energy to the substrate; both are hence well-established crystal growth promoting factors. It is well known that low sputtering pressures can be used as a parameter improving the growth of highly c -axis oriented aluminum nitride films at room temperature even without applying bias voltage to the substrate. Generally, the use of high pressures implies thermalization of particles within the gas phase and is considered to increase the energy gap between these and the substrate surface. However, in later experiments we have learned that the use of high processing pressures does not necessarily implies a detriment of crystallographic orientation in the films. By measuring (for the first time to the author's knowledge) the full width at half maximum value of the rocking curve of the 0002-AlN peak at several positions along the 100 mm diameter (100)-silicon wafers on which aluminum nitride thin films were deposited by reactive sputtering, a new effect was observed. Under certain processing conditions, the growth of the AlN thin films is influenced by the target magnetron. More precisely, their degree of c -axis orientation varies at wafer areas locally coincident under the target magnetron. This effect should be considered, especially where large area substrates are employed such as in silicon wafer foundry manufacturing processes. © 2010 American Vacuum Society.

Sanchez-Arriaga G.,Technical University of Madrid
Physics of Plasmas | Year: 2013

The time-dependent current collection by a cylindrical Langmuir probe, whose bias is suddenly changed from zero to a positive or negative finite value, is studied with a novel direct Vlasov code. The numerical algorithm is based on finite-difference formulas to approximate spatial and velocity derivatives and the time integration is carried out with an explicit Runge-Kutta method, or in the case of probe radius small compared with the Debye length, by using the unconditionally stable backward Euler scheme. Both electrons and ions are treated kinetically by the code, which implements initial and boundary conditions that are consistent with the presence of the probe. Within the considered parameter range, the plasma sheath around the probe exhibited an overshoot and it later recovered a steady state. Phase space diagrams of the particle trajectories revealed the presence of a trapped population of particles. The dependence of this population as a function of the probe radius is presented as well as a comparison with the stationary theory. The performance of the code and a comparison with previously used particle-in-cell algorithms are discussed. © 2013 American Institute of Physics.

Porras M.A.,Technical University of Madrid
Journal of the Optical Society of America B: Optical Physics | Year: 2013

We describe the temporal evolution of the electric field of few-cycle optical pulses with arbitrary, time-varying polarization states by means of the instantaneous polarization ellipse and phase, whose physical meanings for few-cycle pulses are clarified. A physically meaningful definition of carrier-envelope phase (CEP) for arbitrarily polarized pulses is introduced. This description is used to study the changes in the temporal evolution of the electric field of a few-cycle pulsed beam. Propagation is found to result in significant changes in the polarization state, phase, and CEP. Approximate analytical formulas for these effects are provided. © 2013 Optical Society of America.

Bodin O.,University of Stockholm | Saura S.,Technical University of Madrid
Ecological Modelling | Year: 2010

Here we propose an integrated framework for modeling connectivity that can help ecologists, conservation planners and managers to identify patches that, more than others, contribute to uphold species dispersal and other ecological flows in a landscape context. We elaborate, extend and partly integrate recent network-based approaches for modeling and supporting the management of fragmented landscapes. In doing so, experimental patch removal techniques and network analytical approaches are merged into one integrated modeling framework for assessing the role of individual patches as connectivity providers. In particular, we focus the analyses on the habitat availability metrics PC and IIC and on the network metric Betweenness Centrality. The combination and extension of these metrics jointly assess both the immediate connectivity impacts of the loss of a particular patch and the resulting increased vulnerability of the network to subsequent disruptions. In using the framework to analyze the connectivity of two real landscapes in Madagascar and Catalonia (NE Spain), we suggest a procedure that can be used to rank individual habitat patches and show that the combined metrics reveal relevant and non-redundant information valuable to assert and quantify distinctive connectivity aspects of any given patch in the landscape. Hence, we argue that the proposed framework could facilitate more ecologically informed decision-making in managing fragmented landscapes. Finally, we discuss and highlight some of the advantages, limitations and key differences between the considered metrics. © 2010 Elsevier B.V.

Onoro J.,Technical University of Madrid
Materials and Corrosion | Year: 2010

The stress corrosion cracking behaviour of 7075 (Al-Zn-Mg-Cu) alloy have been studied in a salt spray fog chamber with two vapourised aqueous solutions (0 and 5% NaCl). The paper analyses the stress corrosion resistance of 7075 aluminium alloy with several precipitation-ageing heat treatments. The results are compared with that obtained in 3.5% NaCl aqueous solution at 20 8C. The salt spray fog testing has permitted a good evaluation of SCC susceptibility in 7075 alloy. All temper conditions studied were susceptible to SCC in the different environments tested. 7075-T6 temper was the most susceptible, while in all the cases studied 7075-T73 temper was the least susceptible. Compared to 7075-T6, 7075-RRA temper improved the resistance against the SCC process, but the mechanical properties obtained were lower. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

Pallero J.L.G.,Technical University of Madrid
Computers and Geosciences | Year: 2013

Line simplification is an important task in map generalization, in traditional paper series as well as in geographic information systems and web map server services. Using the adequate method an accurate representation of the original elements should be obtained by suppression of redundant information while maintaining the shape of the original elements according to the new scale. To that effect one of the most widely used algorithms is the so-called Douglas-Peucker algorithm. It can lead to inconsistent results such as self-intersections or intersections with other elements, so the operator's supervision is necessary following the automatic treatment. In this piece of work a robust and easy-to-implement variation of the Douglas-Peucker algorithm for individual line simplification in two dimensions is presented. The robustness of the new algorithm is based on the concept of intersection of segments and it can be easily implemented in parallel. The new algorithm brings about correct results regardless of tolerance and morphology of the original line or polygon.The algorithm is coded in standard C99 and it can be compiled for serial or parallel execution via OpenMP. Both the algorithm itself and a program that implements it are distributed as free software. The validity of the solution was tested using the GSHHG geography database that can be obtained free through the Web. Results about accuracy of the output, execution speed and scalability of the parallel implementation are presented. © 2013 Elsevier Ltd.

Iriarte G.F.,Technical University of Madrid
Journal of Non-Crystalline Solids | Year: 2010

A systematic study of the influence of the process parameters on the growth of nickel disilicide (NiSi2) nanowires by CVD (Chemical Vapor Deposition) has been carried out in the temperature range of 350 °C to 550 °C. Ni thin films thinner than 100 nm were dissociated using different RTP (Rapid Thermal Processing) steps in order to create Ni droplets which act as nucleation sites for the nanowire growth. Thereafter, silane (SiH4) was flown over these nucleation sites in an attempt to grown nickel silicide nanowires. The purpose of this report is to determine the optimal set of process parameters promoting the growth of nanowires. Moreover, we have studied the impact of the RTP step and the influence of the original (prior to annealing) thickness and status of the Ni layer that once dissociated acts as a catalyst. Also, the effect of the surface underneath the Ni droplets has been investigated. Scanning Electron Microscopy (SEM) as well as Energy Backscattering Electron Diffraction (EBSD) techniques were used to characterize the as-synthesized nanowires. High-resolution transmission electron microscopy (HR-TEM) results show that the nanowires are monocrystalline with a separation of the lattice planes corresponding NiSi2. HR-TEM also showed that the nickel disilicide nanowires do not all grow in a specific growth direction but that several growth directions such as < 111> or < 110> coexist within one and the same nanowire. © 2010 Elsevier B.V. All rights reserved.

Jimenez J.,Technical University of Madrid
Physics of Fluids | Year: 2013

The relevance of Orr's inviscid mechanism to the transient amplification of disturbances in shear flows is explored in the context of bursting in the logarithmic layer of wall-bounded turbulence. The linearized problem for the wall normal velocity is first solved in the limit of small viscosity for a uniform shear and for a channel with turbulent-like profile, and compared with the quasiperiodic bursting of fully turbulent simulations in boxes designed to be minimal for the logarithmic layer. Many properties, such as time and length scales, energy fluxes between components, and inclination angles, agree well between the two systems. However, once advection by the mean flow is subtracted, the directly computed linear component of the turbulent acceleration is found to be a small part of the total. The temporal correlations of the different quantities in turbulent bursts imply that the classical model, in which the wall-normal velocities are generated by the breakdown of the streamwise-velocity streaks, is a better explanation than the purely autonomous growth of linearized bursts. It is argued that the best way to reconcile both lines of evidence is that the disturbances produced by the streak breakdown are amplified by an Orr-like transient process drawing energy directly from the mean shear, rather than from the velocity gradients of the nonlinear streak. This, for example, obviates the problem of why the cross-stream velocities do not decay once the streak has broken down. © 2013 Author(s).

Romero I.,Technical University of Madrid
Entropy | Year: 2013

The well-known Noether theorem in Lagrangian and Hamiltonian mechanics associates symmetries in the evolution equations of a mechanical system with conserved quantities. In this work, we extend this classical idea to problems of non-equilibrium thermodynamics formulated within the GENERIC (General Equations for Non-Equilibrium Reversible-Irreversible Coupling) framework. The geometric meaning of symmetry is reviewed in this formal setting and then utilized to identify possible conserved quantities and the conditions that guarantee their strict conservation. Examples are provided that demonstrate the validity of the proposed definition in the context of finite and infinite dimensional thermoelastic problems. © 2013 by the author; licensee MDPI, Basel, Switzerland.

Jimenez J.,Technical University of Madrid
Physics of Fluids | Year: 2013

The current state of knowledge about the structure of wall-bounded turbulent flows is reviewed, with emphasis on the layers near the wall in which shear is dominant, and particularly on the logarithmic layer. It is shown that the shear interacts with scales whose size is larger than about one third of their distance to the wall, but that smaller ones, and in particular the vorticity, decouple from the shear and become roughly isotropic away from the wall. In the buffer and viscous layers, the dominant structures carrying turbulent energy are the streamwise velocity streaks, and the vortices organize both the dissipation and the momentum transfer. Farther from the wall, the velocity remains organized in streaks, although much larger ones than in the buffer layer, but the vortices lose their role regarding the Reynolds stresses. That function is taken over by wall-attached turbulent eddies with sizes and lifetimes proportional to their heights. Two kinds of eddies have been studied in some detail: vortex clusters, and ejections and sweeps. Both can be classified into a detached background, and a geometrically self-similar wall-attached family. The latter is responsible for most of the momentum transfer, and is organized into composite structures that can be used as models for the attached-eddy hierarchy hypothesized by Townsend ["Equilibrium layers and wall turbulence," J. Fluid Mech.11, 97-120 (1961)]. The detached component seems to be common to many turbulent flows, and is roughly isotropic. Using a variety of techniques, including direct tracking of the structures, it is shown that an important characteristic of wall-bounded turbulence is temporally intermittent bursting, which is present at all distances from the wall, and in other shear flows. Its properties and time scales are reviewed, and it is shown that bursting is an important part of the production of turbulent energy from the mean shear. It is also shown that a linearized model captures many of its characteristics. © 2013 AIP Publishing LLC.

Higuera F.J.,Technical University of Madrid
Journal of Fluid Mechanics | Year: 2013

An Eulerian multifluid model is used to describe the evolution of an electrospray plume and the flow induced in the surrounding gas by the drag of the electrically charged spray droplets in the space between an injection electrode containing the electrospray source and a collector electrode. The spray is driven by the voltage applied between the two electrodes. Numerical computations and order-of-magnitude estimates for a quiescent gas show that the droplets begin to fly back toward the injection electrode at a certain critical value of the flux of droplets in the spray, which depends very much on the electrical conditions at the injection electrode. As the flux is increased toward its critical value, the electric field induced by the charge of the droplets partially balances the field due to the applied voltage in the vicinity of the injection electrode, leading to a spray that rapidly broadens at a distance from its origin of the order of the stopping distance at which the droplets lose their initial momentum and the effect of their inertia becomes negligible. The axial component of the electric field first changes sign in this region, causing the fly back. The flow induced in the gas significantly changes this picture in the conditions of typical experiments. A gas plume is induced by the drag of the droplets whose entrainment makes the radius of the spray away from the injection electrode smaller than in a quiescent gas, and convects the droplets across the region of negative axial electric field that appears around the origin of the spray when the flux of droplets is increased. This suppresses fly back and allows much higher fluxes to be reached than are possible in a quiescent gas. The limit of large droplet-to-gas mass ratio is discussed. Migration of satellite droplets to the shroud of the spray is reproduced by the Eulerian model, but this process is also affected by the motion of the gas. The gas flow preferentially pushes satellite droplets from the shroud to the core of the spray when the effect of the inertia of the droplets becomes negligible, and thus opposes the well-established electrostatic/inertial mechanism of segregation and may end up concentrating satellite droplets in an intermediate radial region of the spray. © 2013 Cambridge University Press.

Ahedo E.,Technical University of Madrid | Ramos J.J.,Massachusetts Institute of Technology
Physics of Plasmas | Year: 2012

An earlier analysis of the Hall-magnetohydrodynamics (MHD) tearing instability [E. Ahedo and J. J. Ramos, Plasma Phys. Controlled Fusion 51, 055018 (2009)] is extended to cover the regime where the growth rate becomes comparable or exceeds the sound frequency. Like in the previous subsonic work, a resistive, two-fluid Hall-MHD model with massless electrons and zero-Larmor-radius ions is adopted and a linear stability analysis about a force-free equilibrium in slab geometry is carried out. A salient feature of this supersonic regime is that the mode eigenfunctions become intrinsically complex, but the growth rate remains purely real. Even more interestingly, the dispersion relation remains of the same form as in the subsonic regime for any value of the instability Mach number, provided only that the ion skin depth is sufficiently small for the mode ion inertial layer width to be smaller than the macroscopic lengths, a generous bound that scales like a positive power of the Lundquist number. © 2012 American Institute of Physics.

Izpura J.I.,Technical University of Madrid
Advances in Condensed Matter Physics | Year: 2013

Although everybody should know that measurements are never performed directly on materials but on devices, this is not generally true. Devices are physical systems able to exchange energy and thus subject to the laws of physics, which determine the information they provide. Hence, we should not overlook device effects in measurements as we do by assuming naively that photoluminescence (PL) is bulk emission free from surface effects. By replacing this unjustified assumption with a proper model for GaN surface devices, their yellow band PL becomes surface-assisted luminescence that allows for the prediction of the weak electroluminescence recently observed in n-GaN devices when holes are brought to their surfaces. © 2013 José Ignacio Izpura.

Guslienko K.Y.,University of the Basque Country | Heredero R.H.,Ikerbasque | Chubykalo-Fesenko O.,Technical University of Madrid | Chubykalo-Fesenko O.,CSIC - Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The quasistationary and transient (nanosecond) regimes of nonlinear vortex dynamics in a soft magnetic dot driven by an oscillating external field are studied. We derive a nonlinear dynamical system of equations for the vortex core position and phase, assuming that the main source of nonlinearity comes from the magnetostatic energy. In the stationary regime, we demonstrate the occurrence of a fold-over bifurcation and calculate analytically the resonant nonlinear vortex frequencies as a function of the amplitude and frequency of the applied driving field. In the transient regime, we show that the vortex core dynamics are described by an oscillating trajectory radius. The resulting dynamics contain multiple frequencies with amplitude decaying in time. Finally, we evaluate the ranges of the system parameters leading to a vortex core instability (core polarization reversal). © 2010 The American Physical Society.

Hengsbach S.,Karlsruhe Institute of Technology | Lantada A.D.,Technical University of Madrid
Biomedical Microdevices | Year: 2014

The possibility of designing and manufacturing biomedical microdevices with multiple length-scale geometries can help to promote special interactions both with their environment and with surrounding biological systems. These interactions aim to enhance biocompatibility and overall performance by using biomimetic approaches. In this paper, we present a design and manufacturing procedure for obtaining multi-scale biomedical microsystems based on the combination of two additive manufacturing processes: a conventional laser writer to manufacture the overall device structure, and a direct-laser writer based on two-photon polymerization to yield finer details. The process excels for its versatility, accuracy and manufacturing speed and allows for the manufacture of microsystems and implants with overall sizes up to several millimeters and with details down to sub-micrometric structures. As an application example we have focused on manufacturing a biomedical microsystem to analyze the impact of microtextured surfaces on cell motility. This process yielded a relevant increase in precision and manufacturing speed when compared with more conventional rapid prototyping procedures. © 2014 Springer Science+Business Media.

Connor D.J.,University of Melbourne | Gomez-del-Campo M.,Technical University of Madrid
Scientia Horticulturae | Year: 2013

Simulations of oil yield and quality are presented for N-S oriented, hedgerow olive orchards of a range of structures (viz canopy depth, canopy width, canopy slope and row spacing) using responses of yield and quality parameters to solar irradiance on canopy walls measured in a range of orchards, cv. Arbequina, in Spain. Results reveal that orchard yield of hedgerows of rectangular shape reaches a maximum when canopy depth equals alley width (row spacing-canopy width) and decreases at wider spacing, and/or with wider canopies, as the length of productive row decreases per unit area. Maximum yields for 4-m deep canopies were 2885kgha-1 at 1-m width and 5-m row spacing, 2400kgha-1 at 2-m width and 6-m spacing, and 2050kgha-1 at 3-m width and 7-m spacing. Illumination of canopies can be increased by applying slopes to form rhomboidal hedgerows. Substantial yield advantage can be achieved, especially for wide hedgerows, partly by closer row spacing that increases row length per unit area. By comparison, responses to latitude in the range 30-40° are small and do not warrant different row spacing. Oil quality parameters also respond to orchard structure. Responses are presented for oleic and palmitic acid, stability, and maturity index. Oleic acid content declines as alley spacing increases and is smaller, shallow than in wide, deep canopies. Palmitic acid content, stability, and maturity index increase with row alley spacing and are greater in narrow, shallow than in wide, deep canopies. © 2012 Elsevier B.V.

Albers U.,Technical University of Madrid
Nutrición hospitalaria : organo oficial de la Sociedad Española de Nutrición Parenteral y Enteral | Year: 2012

To determine drug consumption in institutionalized elderly living in the Region of Madrid (Spain) and to assess the relationship between drug intake and biochemical parameters for vitamin B12 (Cobalamin and Holotranscobalamin), serum folate (SF) and homocysteine (Hcy). 167 subjects (32% men), mean age 83 ± 7 years, were classified according to biochemical parameter levels (in or out of reference range) and drugs were classified according to ATC system. The relationship between drug intake and biochemical levels was studied by means of the Fisher exact test. The daily mean drug intake was 5. Psicoleptic and antiacid drugs were the most consumed (both 53%). Cobalamin (median 158.2 pg/mL; 10.7% of individuals), SF (5.3 ng/mL; 52.1%) and holotranscobalamin (11.76 pmoL/L; 7.8%) deficiencies were observed. Hyperhomocysteinaemia (19.4 μmoL/L) was present in 65% of population. Antiaenemic drug intake normalized cobalamin, urologic drug and corticosteroids SF and psicoanaleptics holotranscobalamin levels. Drugs against pulmonar obstruction increased Hcy concentration (all p < 0.05). There is a high prevalence of SF deficiency and hyperhomocysteinaemia in the studied population. The elevated number of drugs taken simultaneously by each subject makes it difficult to analyze which drugs are responsible for those alterations.

Zanuy C.,Technical University of Madrid
Engineering Structures | Year: 2016

Serviceability requirements of concrete structures establish the limitation of deflections. Even though the exact prediction of deflections is a difficult task that is neither necessary nor possible, the assumptions of codes of practice to consider time- and cycle-dependent effects of reinforced concrete are conceptually questionable. A common rule is that both sustained and repeated loading result in a reduction of the tension stiffening contribution. Nevertheless, the cyclic behaviour of reinforced concrete is nonlinear and non-symmetrical during unloading and reloading, leading to deformations larger than those corresponding to the fully cracked member during unloading stages. In this paper, an approach is presented to distinguish between time- and cycle-dependent effects. A curvature component is added to the estimation of curvatures so that the cyclic effect can be understood as a different contribution to deflections with respect to creep and shrinkage. The comparison with experimental results indicates that the cyclic component of deformations cannot be neglected. © 2016 Elsevier Ltd

Pacios L.F.,Technical University of Madrid | Galvez O.,CSIC - Institute for the Structure of Matter
Journal of Chemical Theory and Computation | Year: 2010

A combined computational study using molecular surfaces and Poisson-Boltzmann electrostatic potentials for proteins and quantum calculations on complexes representing the vanadate cofactor throughout the catalytic cycle is employed to study the activity of vanadium iodoperoxidase (VIPO) from alga Laminaria digitata. A model structure of VIPO is compared with available crystal structures of chloroperoxidases (VClPOs) and bromoperoxidases (VBrPOs) focusing on properties of the active site that concern halogen specificity. It is found that VIPO displays distinctive features regarding electrostatic potentials at the site cavity and the local topography of the cavity entrance. Quantum calculations on cofactor stages throughout the catalytic cycle reveal that, while steps involving binding of hydrogen peroxide and halide oxidization agree with available data on VBrPO, final formation and subsequent release of hypohalous acid could follow a different pathway consisting of His476-assisted protonation of bonded hypoiodite and further displacement by a water molecule. Ab initio free energies of reaction computed to explore iodination of organic substrates predict strongly exoergonic reactions with HOI, whereas other possible iodination reagents give thermodynamically disfavored reactions. © 2010 American Chemical Society.

Rodriguez T.,Spanish University for Distance Education (UNED) | Garcia N.,Technical University of Madrid
Machine Vision and Applications | Year: 2010

In this paper we describe a computer vision-based traffic monitoring system able to detect individual vehicles in real-time. Our fully integrated system first obtains the main traffic variables: counting, speed and category; and then computes a complete set of statistical variables. The objective is to investigate some of the difficulties impeding existing traffic systems to achieve balanced accuracy in every condition; i.e. day and night transitions, shadows, heavy vehicles, occlusions, slow traffic and congestions. The system we present is autonomous, works for long periods of time without human intervention and adapts automatically to the changing environmental conditions. Several innovations, designed to deal with the above circumstances, are proposed in the paper: an integrated calibration and image rectification step, differentiated methods for day and night, an adaptive segmentation algorithm, a multistage shadow detection method and special considerations for heavy vehicle identification and treatment of slow traffic. A specific methodology has been developed to benchmark the accuracy of the different methods proposed. © Springer-Verlag 2009.

Montellano A.S.,Technical University of Madrid
Archnet-IJAR | Year: 2015

The indeterminacy of the domestic space is one of the main trends in flexible housing design. It involves the possibility of using the rooms in a dwelling in multiple ways that are not determined by the architect. The views of non-functionalist housing are more present lately, but still forbidden in the Spanish social housing market, where regulations stipulate a strict functionalist housing plan. However, there is a premodernist example of this strategy in Madrid: the Casa de las Flores (the House of Flowers), a rationalist building from 1931 with a neutral plan of indeterminate rooms. This study comprises a series of interviews with the users, photographs, diagrams and new drawings that show how people use their apartments. The aim of this research is to assess the validity of indeterminacy as an architectural response to social changes in Spain, with a view to its introduction in future housing developments. © 2015 Archnet-IJAR, International Journal of Architectural Research.

Crespo C.T.,Technical University of Madrid
Journal of Physical Chemistry C | Year: 2016

Cu-Sb-S semiconductors are a large group of materials promising for a variety of applications, especially as thin-film solar cell absorbers. We present first-principles calculations of the optical and electronic properties of Cu3SbS4 in the famatinite structure. The effect of the microscopic properties on macroscopic optical and photovoltaic parameters is analyzed. By splitting the optical properties, we identified microscopically the origin of the high absorption coefficients. It is because of an elevated contribution from S-S and Sb-Sb transitions. In addition, we estimate the macroscopic potential of these compounds for photovoltaic applications obtaining solar cell efficiencies using different spectra. The results indicate the great potential of these materials for photovoltaics. © 2016 American Chemical Society.

In the last few years we have seen the creation of an everyday larger and varied series of are creating large and varied series of environmental management tools used to analyze and classify environmentally each mineral and its physical, economic and environmental circumstances. Thus we now, count with the Material Flow Analysis (MFA) of a mining operation, the Life Cycle Analysis (LCA), Energy and Exergy Analysis, Cost Benefit Environmental Analysis, Carbon Footprints, the Best Available Technology (BTA) and many others able to analyze and classify ore deposit site types, availability of resources, environmental impact conditions, transparency in communication and almost all crucial aspects related with the environmental geometry of the mining production process. This paper focuses on the application of some management tools that best fit to the minerals used in the ceramic and glass industry.

Garcia-Diaz I.,CSIC - Eduardo Torroja Institute for Construction Science | Palomo J.G.,Technical University of Madrid | Puertas F.,CSIC - Eduardo Torroja Institute for Construction Science
Cement and Concrete Composites | Year: 2011

The cement industry is seeking alternative approaches to reduce the high energy and environmental costs of Portland cement manufacture. One such alternative is belite cement. In the present study clinkers with high (36-60%) belite contents were obtained at 1350 °C from raw mixes consisting of ceramic waste and the fluxing/mineralised pair CaF2/CaSO4. The factors found to affect the mineralogical composition and the clinker phase polymorphs obtained were the lime saturation factor (LSF), the presence of ceramic waste and the addition of CaF2 and CaSO4. The reactivity of these belite clinkers with water was analysed with isothermal conduction calorimetry. A statistical study was then conducted on the findings to determine the effect of each variable when the response signals were peak heat flow rate and the time needed to reach that peak. The statistical analysis identified the optimal experimental conditions to be a LSF of 90%, a CaSO 4 content of 2.60%, and the absence of both ceramic waste and CaF2. © 2011 Elsevier Ltd. All rights reserved.

Gaite J.,Technical University of Madrid
Nonlinear Dynamics | Year: 2011

We study the differential equations of lumped-parameter models of spacecraft thermal control. Firstly, we consider a satellite model consisting of two isothermal parts (nodes): an outer part that absorbs heat from the environment as radiation of various types and radiates heat as a black body, and an inner part that just dissipates heat at a constant rate. The resulting system of two nonlinear ordinary differential equations for the satellite's temperatures is analyzed with various methods, which prove that the temperatures approach a steady state if the heat input is constant, whereas they approach a limit cycle if it varies periodically. Secondly, we generalize those methods to study a many-node thermal model of a spacecraft: this model also has a stable steady state under constant heat inputs that becomes a limit cycle if the inputs vary periodically. Finally, we propose new numerical analyses of spacecraft thermal models based on our results, to complement the analyses normally carried out with commercial software packages. © 2010 Springer Science+Business Media B.V.

Villen-Altamirano J.,Technical University of Madrid
Reliability Engineering and System Safety | Year: 2014

We consider a wide class of models that includes the highly reliable Markovian systems (HRMS) often used to represent the evolution of multi-component systems in reliability settings. Repair times and component lifetimes are random variables that follow a general distribution, and the repair service adopts a priority repair rule based on system failure risk. Since crude simulation has proved to be inefficient for highly-dependable systems, the RESTART method is used for the estimation of steady-state unavailability and other reliability measures. In this method, a number of simulation retrials are performed when the process enters regions of the state space where the chance of occurrence of a rare event (e.g., a system failure) is higher. The main difficulty involved in applying this method is finding a suitable function, called the importance function, to define the regions. In this paper we introduce an importance function which, for unbalanced systems, represents a great improvement over the importance function used in previous papers. We also demonstrate the asymptotic optimality of RESTART estimators in these models. Several examples are presented to show the effectiveness of the new approach, and probabilities up to the order of 10-42 are accurately estimated with little computational effort. © 2014 Elsevier Ltd.

Huera-Huarte F.J.,Rovira i Virgili University | Bangash Z.A.,Rovira i Virgili University | Gonzalez L.M.,Technical University of Madrid
Journal of Fluids and Structures | Year: 2014

A series of experiments describing the dynamic response resulting from vortex shedding excitation, on isolated long flexible cylinders with two different low mass ratios (mass to displaced fluid mass), are presented. The cylinder models had aspect ratios (length to diameter) of 158 and 187 and mass ratios of 1.1 and 2.7 respectively, both with very low damping (<1% of critical). The models were towed to generate a stepped current in a 100. m long still water tank with a cross-section of 3.8×2.5. m, and curvatures were measured at 11 strain gauge stations distributed along the length of the models, resulting in an extensive data set. Reynolds numbers over 37. 000 were reached and responding modes up to the fifth were observed, showing maximum amplitudes of more than 3 diameters in the model with the lowest mass ratio. Drag coefficients with values well over 3 were also measured. © 2014 Elsevier Ltd.

Roossinck M.J.,Pennsylvania State University | Roossinck M.J.,Murdoch University | Garcia-Arenal F.,Technical University of Madrid
Current Opinion in Virology | Year: 2015

Plant viruses can emerge into crops from wild plant hosts, or conversely from domestic (crop) plants into wild hosts. Changes in ecosystems, including loss of biodiversity and increases in managed croplands, can impact the emergence of plant virus disease. Although data are limited, in general the loss of biodiversity is thought to contribute to disease emergence. More in-depth studies have been done for human viruses, but studies with plant viruses suggest similar patterns, and indicate that simplification of ecosystems through increased human management may increase the emergence of viral diseases in crops. © 2015 Elsevier B.V. All rights reserved.

Preciado M.A.,Aston University | Muriel M.A.,Technical University of Madrid
Journal of Lightwave Technology | Year: 2012

By spectral analysis, and using joint time-frequency representations, we present the theoretical basis to design invariant bandlimited Airy pulses with an arbitrary degree of robustness and an arbitrary range of single-mode fiber chromatic dispersion. The numerically simulated examples confirm the theoretically predicted pulse partial invariance in the propagation of the pulse in the fiber. © 2012 IEEE.

Perez-Martinez P.J.,Technical University of Madrid | Miranda R.M.,University of Sao Paulo
Transportation Research Part D: Transport and Environment | Year: 2014

We estimate the energy consumption of toll highway transport on a number of Spanish roads. Regression parameters are balanced according to coefficients from an empirical analysis based on survey data by vehicle type. The mean energy consumption and subsequent CO2 emissions on the toll highway sections are estimated as 1895MJ/h/lane-km and 0.15tCO2eq./h/lane-km, values that increase to 2644 and 0.22 when energy and carbon emissions of transport infrastructure are considered based on the life cycle energy consumption for toll highway construction and use. If the energy intensity of infrastructure construction is allocated to the users according to traffic, it is much higher for motorcycles than for cars, and is significantly lower for articulated trucks than for vans. © 2013 Elsevier Ltd.

Gurrutxaga M.,University of the Basque Country | Saura S.,Technical University of Madrid
Environmental Conservation | Year: 2014

Transport infrastructures are a major driver of global landscape change. In many areas, highways were built before environmental impact assessments required the implementation of wildlife crossing structures. A fundamental task in the development of ecological networks is identifying areas where dispersal pathways of vulnerable populations may be blocked or affected by high volume roads. Financial considerations may limit investment, thus it is vital to establish the relative contribution of each road defragmentation location to upholding habitat connectivity and availability. In this paper, recent methodological developments in habitat network analysis, derived from the probability of connectivity index, were refined and used to evaluate the role of each highway defragmentation location in restoring landscape connectivity. The forest protected area network in the Basque country (northern Spain) was selected as an illustrative case study. The proposed approach was able to quantify and effectively account for a combination of factors determining the contribution of each highway defragmentation location to upholding connectivity, which are rarely jointly considered in analyses oriented to support restoration decisions in landscapes affected by the barrier effect of transport infrastructures. The contribution to connectivity of each defragmentation location depended on its topological position in the landscape, on the relative decrease in the effective distance among habitat areas that results from the permeability restoration at that location, on the distance from the defragmentation location to other alternative wildlife crossing structures already existing in the landscape, on the amount of habitat in the areas connected by the linkages that run through the defragmentation location and on the dispersal abilities of the focal species. © Foundation for Environmental Conservation 2013.

Vera M.,Charles III University of Madrid | Linan A.,Technical University of Madrid
International Journal of Heat and Mass Transfer | Year: 2010

Multilayered, counterflow, parallel-plate heat exchangers are analyzed numerically and theoretically. The analysis, carried out for constant property fluids, considers a hydrodynamically developed laminar flow and neglects longitudinal conduction both in the fluid and in the plates. The solution for the temperature field involves eigenfunction expansions that can be solved in terms of Whittaker functions using standard symbolic algebra packages, leading to analytical expressions that provide the eigenvalues numerically. It is seen that the approximate solution obtained by retaining the first two modes in the eigenfunction expansion provides an accurate representation for the temperature away from the entrance regions, specially for long heat exchangers, thereby enabling simplified expressions for the wall and bulk temperatures, local heat-transfer rate, overall heat-transfer coefficient, and outlet bulk temperatures. The agreement between the numerical and theoretical results suggests the possibility of using the analytical solutions presented herein as benchmark problems for computational heat-transfer codes. © 2010 Elsevier Ltd.

Hoy R.S.,University of South Florida | Karayiannis N.C.,Technical University of Madrid
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

We study a simple bead-spring polymer model exhibiting competing crystallization and glass transitions. Constant-pressure molecular dynamics simulations are employed to study phase behavior and morphological order. For adequately slow quench rates, chain systems exhibit a first-order phase transition (crystallization) below a critical temperature T=Tcryst. We observe the formation of close-packed crystallites of FCC and/or HCP order, separated by domain walls, twin defects, and amorphous regions. Such crystal structures closely resemble the corresponding ordered morphologies of athermal polymer packings: fully flexible chains retain random-walk-like configurations in the crystalline state and do not form lamellae, while semiflexible chains do form lamellae. The model presented here is well suited to the modeling of granular and colloidal polymers, in particular for elucidating the factors that dictate the formation of specific ordered morphologies. © 2013 American Physical Society.

Zanin M.,Technical University of Madrid
Chaos (Woodbury, N.Y.) | Year: 2011

Congenital obstructive nephropathy (ON) is one of the most frequent nephropathy observed among newborns and children, and the first cause of end-stage renal diseases treated by dialysis or transplantation. This pathology is characterized by the presence of an obstacle in the urinary tract, e.g., stenosis or abnormal implantation of the urethra in the kidney. In spite of important advances, pathological mechanisms are not yet fully understood. In this contribution, the topology of complex networks created upon vectors of features for control and ON subjects is related with the severity of the pathology. Nodes in these networks represent genetic and metabolic profiles, while connections between them indicate an abnormal relation between their expressions. Resulting topologies allow discriminating ON subjects and detecting which genetic or metabolic elements are responsible for the malfunction.

DeFelipe J.,Technical University of Madrid
Frontiers in Neuroanatomy | Year: 2015

Over the years the field of neuroanatomy has evolved considerably but unraveling the extraordinary structural and functional complexity of the brain seems to be an unattainable goal, partly due to the fact that it is only possible to obtain an imprecise connection matrix of the brain. The reasons why reaching such a goal appears almost impossible to date is discussed here, together with suggestions of how we could overcome this anatomical problem by establishing new methodologies to study the brain and by promoting interdisciplinary collaboration. Generating a realistic computational model seems to be the solution rather than attempting to fully reconstruct the whole brain or a particular brain region. © 2015 DeFelipe.

Fernandez-Yuste J.A.,Technical University of Madrid
Geomorphology | Year: 2011

In the first decades of the twentieth century, the Ebro River was the Iberian channel with the most active fluvial dynamics and the most remarkable spatial-temporal evolution. Its meandering typology, the dimensions of its floodplain (with an average width > 3.0. km), and the singularities of its flow regime produced a especially interesting set of river functions from the perspective of the fluvial geomorphology of the largest Mediterranean channels.The largest dynamics of the Ebro River are concentrated along the meandering profile of the central sector. During the twentieth century, this sector experienced a large alteration of its geomorphological structure. We present here an analysis of this evolution through the cartographic study of a long segment of the river (~. 250. km) in 1927, 1956, and 2003. The study is focused on a wide set of geomorphic parameters and indicators that represent the forms of the meander belt, its lateral dynamics, and the overall mobility of the river corridor. The results of the analysis show a large transformation of the meander dynamics, as well as a massive loss of the river lateral activity, most of which occurred in the second half of the twentieth century.This intense geomorphological transformation becomes visible in (i) the large reduction of the bankfull width and the active channel area; (ii) the decrease in the rate of lateral channel migration; (iii) the loss of channel activity; and (iv) the large reduction of coincidence of the active channel areas. However, the most traditional form parameters (i.e., wavelength, amplitude, radius of curvature, and meander length) do not show significant differences throughout the time interval analysed. The study reinforces the necessity of integrating a wide range of dynamic indicators, which may complement the classical form parameters and represent the real functioning of the river corridor, in the geomorphological analyses of meander dynamics.This work also shows the most important procedures for the recuperation of the ecomorphological processes of the meander belt. It highlights the most urgent measurement for ecological recovery and illustrates the management scenarios that have led to the present-day situation of the river system. This work further highlights the management scenarios that could be most important for the continued good status of the meander dynamics in this changing river corridor. © 2011 Elsevier B.V.

Duro R.J.,University of La Coruna | Grana M.,University of the Basque Country | De Lope J.,Technical University of Madrid
Information Sciences | Year: 2010

The area of cognitive or intelligent robotics is moving from the single monolithic robot control and behavior problem to that of controlling robots with multiple components or multiple robots operating together, and even collaborating, in dynamic and unstructured environments. This paper introduces the topic and provides a general overview of the current state of the field of Multicomponent Robotic Systems focusing on providing some insights into where Hybrid Intelligent Systems could provide key contributions to its advancement. Thus, the aim is to identify prospective research areas and to try to delimit the field from the point of view of the following essential problem: how to coordinate multiple robotic elements in order to perform useful tasks. © 2010 Published by Elsevier Inc.

We propose discretizations for a general class of nonlinear, coupled, thermomechanical problems of evolution. The most salient feature of the new methods is that they rigorously preserve the two laws of thermodynamics as well as the symmetries of the systems they model. To formulate such methods we exploit the geometric structure afforded by the GENERIC formalism of non-equilibrium thermodynamics and we follow a systematic methodology that results in discrete evolution equations which mimic the GENERIC structure. As an illustration, a complete discretization of finite strain thermoelasticity is presented, using finite elements in space and a monolithic integrator in time. Simulations are provided which demonstrate the conservation features of the algorithm as well as its remarkable robustness. © 2010 Elsevier B.V.

Guadarrama S.,Fundamentals of Soft Computing Unit | Ruiz-Mayor A.,Technical University of Madrid
Information Sciences | Year: 2010

This work, inspired by the idea of "Computing with Words and Perceptions" proposed by Zadeh in [57,59], focuses on how to transform measurements into perceptions [22] for the problem of map building by Autonomous Mobile Robots. We propose to model the perceptions obtained from sonar-sensors as two grid maps: one for obstacles and another for empty-spaces. The rules used to build and integrate these maps are expressed by linguistic descriptions and modeled by fuzzy rules. The main difference of this approach from other studies reported in the literature is that the method presented here is based on the hypothesis that the concepts "occupied" and "empty" are antonyms rather than complementary (as it happens in probabilistic approaches), or independent (as it happens in the previous fuzzy models). Controlled experimentation with a real robot in three representative indoor environments has been performed and the results presented. We offer a qualitative and quantitative comparison of the estimated maps obtained by the probabilistic approach, the previous fuzzy method and the new antonyms-based fuzzy approach. It is shown that the maps obtained with the antonyms-based approach are better defined, capture better the shape of the walls and of the empty-spaces, and contain less errors due to rebounds and short-echoes. Furthermore, in spite of noise and low resolution inherent to the sonar-sensors used, the maps obtained are accurate and tolerant to imprecision. © 2010 Published by Elsevier Inc.

Zanuy C.,Technical University of Madrid
Magazine of Concrete Research | Year: 2010

It is widely accepted that tension stiffening of reinforced concrete reduces in the long term. In the codes of practice, this is accounted for by means of a modification in the empirical parameters to interpolate the average response of the reinforced member between the states I (uncracked) and II (bare steel). This average response is actually the result of the interaction of the different time-dependent mechanisms which develop in the element. In a tension member, the behaviour is mainly influenced by concrete creep and shrinkage and time-dependent bond deterioration. The role played by these processes is still unknown. An analytical approach is developed in this paper in order to understand the influence of such processes in the long-term decay of tension stiffening in tension members. The model is able to explain the experimental response of specimens tested in the literature and the results show the major influence of the time-dependent bond deterioration (bond creep and bond stiffness modification), rather than concrete creep and shrinkage. © 2010 Thomas Telford Ltd.

Gomez-Barroso J.L.,Spanish University for Distance Education (UNED) | Feijo C.,Technical University of Madrid
Telecommunications Policy | Year: 2010

Public activity in the telecommunications industry has experienced important transformations in the last decade: "reinvolvement" in infrastructure deployment, "innovative" boosting measures, and decentralisation of some decisions. Conceptually, even more important than the measures themselves is the fact that private agents often participate in their realisation and execution. This paper reviews how justifications for public action that would apply to any economic activity area have modelled the public-private relationship in the telecommunications sector. Subsequently, it focuses on the analysis of the new spaces for public-private collaboration that are currently opening up. © 2010 Elsevier Ltd. All rights reserved.

Senent M.L.,CSIC - Institute for the Structure of Matter | Dominguez-Gomez R.,Technical University of Madrid
Chemical Physics Letters | Year: 2010

Structural and anharmonic spectroscopic properties of SiC4 are investigated using the RCCSD(T)-F12 method and second order perturbation theory. Observable parameters are determined for various isotopomers, 28Si12C4, 28Si13CCCC, 28SiC13CCC, 28SiCC 13CC, 28SiCCC 13C and 29SiC4. Fermi interactions are considered in the model. Results are compared with the parameters of C5. For 28Si12C4, the ν1 fundamental has been found at 2094 cm-1 with RCCSD(T)-F12, close to the observed value 2095.46 cm-1. In addition, B0 has been determined to be 1536.29 MHz with RCCSD(T)/CBS, whereas the experimental value is 1533.8 MHz. The CASSCF/aug-cc-pVTZ equilibrium dipole moment was estimated to be 6.2112 Debyes. © 2010 Elsevier B.V. All rights reserved.

Alonso-Medina A.,Technical University of Madrid
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2010

Transition probabilities for 30 spectral lines, arising from the 5d10 6s{8s, 7p, 5f, 5g} electronic configurations of Pb III (20 measured for the first time), have been experimentally determined from measurements of emission line intensities in a plasma lead induced by ablation with a Nd:YAG laser. The line intensities were obtained with the target placed in molecular argon at 6Torr, recorded at a 400ns delay from the laser pulse, which provides appropriate measurement conditions, and analysed between 200 and 700nm. They are measured when the plasma reaches local thermodynamic equilibrium (LTE). The plasma under study had an electron temperature (T) of 21,400K and an electron number density (Ne) of 7×1016cm-3. The influence of self-absorption has been estimated for every line, and plasma homogeneity has been checked. The values obtained were compared with previous experimental values and theoretical estimates where possible. © 2010 Elsevier Ltd.

Perez I.,University of La Coruna | Gallego J.,Technical University of Madrid
Construction and Building Materials | Year: 2010

This paper analyses the permanent deformation performance of an unbound granular material for base layers of low-traffic roads. The material has been subjected to repeated triaxial loads. The shakedown theory was used to classify the structural response of the unbound granular material to the applications of load cycles. Three models were fitted to express the cumulative permanent strain as a function of the number of load cycles. In general, the predictions of two models previously studied by other researchers proved to be good but in the long-term, they tended to underestimate the measured values. In contrast, a third new model - the sum of two well known models - offered excellent predictions, which in the long-term did not tend to either underestimate or overestimate the measured values. © 2009 Elsevier Ltd. All rights reserved.

Alonso-Medina A.,Technical University of Madrid
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2010

In this paper, we present transition probabilities for 97 spectral lines of Sn I, corresponding to transitions n(n = 6,7,8)s → 5p2, n(n = 5,6,7)d → 5p2, 5p3 → 5p2, n(n = 7)p → 6s, determined by measuring the intensities of the emission lines of a Laser-induced breakdown (emission) spectrometry (LIBS). The optical emission spectroscopy from a laser-induced plasma generated by a 10 640 Å radiation, with an irradiance of 1.4 × 1010 Wcm- 2 on an Sn-Pb alloy (an Sn content of approximately 20%), in vacuum, was recorded at 0.8 μs, and analysed between 1900 and 7000 Å. The population-level distribution and corresponding temperature were obtained using Boltzmann plots. The electron density of the plasma was determined using well-known Stark broadening parameters of spectral lines. The plasma under study had an electron temperature of 13,200 K and an electron number density of 2 × 1016 cm- 3. The experimental relative transition probabilities were put on an absolute scale using the branching ratio method to calculate Sn I multiplet transition probabilities from available radiative lifetime data of their upper states and plotting the Sn I emission spectrum lines on a Boltzmann plot assuming local thermodynamic equilibrium (LTE) to be valid and following Boltzmann's law. The LTE conditions and plasma homogeneity have been checked. Special attention was paid to the possible self-absorption of the different transitions. The experimental results obtained have been compared with the experimental values given by other authors. © 2010 Elsevier B.V. All rights reserved.

Martin H. J.A.,Complutense University of Madrid | Santos M.,Complutense University of Madrid | de Lope J.,Technical University of Madrid
Information Sciences | Year: 2010

Moments are statistical measures used to obtain relevant information about a certain object under study (e.g., signals, images or waveforms), e.g., to describe the shape of an object to be recognized by a pattern recognition system. Invariant moments (e.g., the Hu invariant set) are a special kind of these statistical measures designed to remain constant after some transformations, such as object rotation, scaling, translation, or image illumination changes, in order to, e.g., improve the reliability of a pattern recognition system. The classical moment invariants methodology is based on the determination of a set of transformations (or perturbations) for which the system must remain unaltered. Although very well established, the classical moment invariants theory has been mainly used for processing single static images (i.e. snapshots) and the use of image moments to analyze images sequences or video, from a dynamic point of view, has not been sufficiently explored and is a subject of much interest nowadays. In this paper, we propose the use of variant moments as an alternative to the classical approach. This approach presents clear differences compared to the classical moment invariants approach, that in specific domains have important advantages. The difference between the classical invariant and the proposed variant approach is mainly (but not solely) conceptual: invariants are sensitive to any image change or perturbation for which they are not invariant, so any unexpected perturbation will affect the measurements (i.e. is subject to uncertainty); on the contrary, a variant moment is designed to be sensitive to a specific perturbation, i.e., to measure a transformation, not to be invariant to it, and thus if the specific perturbation occurs it will be measured; hence any unexpected disturbance will not affect the objective of the measurement confronting thus uncertainty. Furthermore, given the fact that the proposed variant moments are orthogonal (i.e. uncorrelated) it is possible to considerably reduce the total inherent uncertainty. The presented approach has been applied to interesting open problems in computer vision such as shape analysis, image segmentation, tracking object deformations and object motion tracking, obtaining encouraging results and proving the effectiveness of the proposed approach. © 2009 Elsevier Inc. All rights reserved.

Larranaga P.,Technical University of Madrid | Moral S.,University of Granada
Applied Soft Computing Journal | Year: 2011

In this paper, we review the role of probabilistic graphical models in artificial intelligence. We start by giving an account of the early years when there was important controversy about the suitability of probability for intelligent systems. We then discuss the main milestones for the foundations of graphical models starting with Pearl's pioneering work. Some of the main techniques for problem solving (abduction, classification, and decision-making) are briefly explained. Finally, we propose some important challenges for future research and highlight relevant applications (forensic reasoning, genomics and the use of graphical models as a general optimization tool). © 2008 Elsevier B.V. All rights reserved.

Tablero C.,Technical University of Madrid
Chemical Physics Letters | Year: 2010

The Fe-doped CuInS2 could have important applications for photovoltaic or spintronic applications. This material has been analyzed from first principles with the local density and the generalized gradient approximation, as well as with a Hubbard term. The effect on the electronic and magnetic structure has been carried out for both ferromagnetic and antiferromagnetic spin alignments. The results compare well with the experimental ones. © 2010 Elsevier B.V. All rights reserved.

Dominguez S.,Technical University of Madrid
Pattern Recognition Letters | Ye