Papers by Pedro J. Zufiria
Simulation of TCP-100 Facility System Level Model for Operation Training Purposes
The TCP-100 parabolic trough collectors research facility at Plataforma Solar de Almería (CIEMAT)... more The TCP-100 parabolic trough collectors research facility at Plataforma Solar de Almería (CIEMAT) has replaced the 32 years old ACUREX research plant, widely used in Automatic Control research. The new TCP-100 structure poses new challenges in the design of more sophisticated operation modes. This paper presents a hybrid first principles system level model of the TCP-100 facility, which is based on two connected parts: a previously published non-linear continuous dynamic model, and a discrete part modelling the behaviour of an operator. This model is able to cover the different operation modes of the plant and proves its applicability for operation training activities. The discrete part of the model characterizes the operation procedure using both the StateGraph formalism in the Modelica object oriented modelling language, and the Dymola tool. We illustrate the validity of our hybrid model by simulating two different operation procedures applied to the TCP-100 plant model in a typical operation day in which the system passes through several operating modes.
Port-Based Modeling of Transport Phenomena in Thermofluid Systems and Object-Oriented Implementation with the Modelica Language
Bus Headways Analysis for Anomaly Detection
IEEE Transactions on Intelligent Transportation Systems, Oct 1, 2022
Application of Neural Networks in the Solar Irradiation Field: Obtainment of Solar Irradiation Maps
Strong singularities and the continuous Newton method
IFAC Proceedings Volumes, 2003
III t.his pap(~r, t.he design of a fault. detection and isolation scheme is addressed, \Ve work o... more III t.his pap(~r, t.he design of a fault. detection and isolation scheme is addressed, \Ve work on plant.s modelled via contilluous-t.ime nonlinear uncertain systems, where the 1ll1certaillty cUld the fault. funct.ioll a.re assullIed t.o be random processes. A model-based allalytical redundancy approach, which checks on-line the statist.ical characteristics of a. residual t.hrough hypotheses tests, is proposed, Also Cl simulation example is discussed, wit.
Dynamical Systems and Differential Equations, AIMS Proceedings 2015 Proceedings of the 10th AIMS International Conference (Madrid, Spain), 2015
We characterize the chaos in a fractional Duffing's equation computing the Lyapunov exponents and... more We characterize the chaos in a fractional Duffing's equation computing the Lyapunov exponents and the dimension of the strange attractor in the effective phase space of the system. We develop a specific analytical method to estimate all Lyapunov exponents and check the results with the fiduciary orbit technique and a time series estimation method.
IFAC Proceedings Volumes, Mar 1, 1998
Mobile robots can use sensor information to create a geometrical model of their environment. Alte... more Mobile robots can use sensor information to create a geometrical model of their environment. Alternatively, they can use sensor information directly without a geometrical interpretation, This paper presents two architectures, each implementing one of these approaches, The first part of the paper presents a sensor space representation architecture using a Self-Organizing Map as a perceptual leveL The second part of this article describes a system for autonomous navigation based on geometrical environment models.
Image compression via optimal vector quantization: a comparison between SOM, LBG and k-means algorithms
Grupo de Redes Neuronales Dpto. de Matemitica Aplicada a las Tecnologias de la Informaci6n ETS In... more Grupo de Redes Neuronales Dpto. de Matemitica Aplicada a las Tecnologias de la Informaci6n ETS Ingenieros de Telecomunicaci6n Universidad Polit6cnica de Madrid E-28040 Madrid ... An application of optimal vector quatization on image compression is studied. A neural ...
Time-Scaling in Recurrent Neural Learning
Lecture Notes in Computer Science, 2002
Recurrent Backpropagation schemes for fixed point learning in continuous-time dynamic neural netw... more Recurrent Backpropagation schemes for fixed point learning in continuous-time dynamic neural networks can be formalized through a differential-algebraic model, which in turn leads to singularly perturbed training techniques. Such models clarify the relative time-scaling between the network evolution and the adaptation dynamics, and allow for rigorous local convergence proofs. The present contribution addresses some related issues in a discrete-time context: fixed point problems can be analyzed in terms of iterations with different evolution rates, whereas periodic trajectory learning can be reduced to a multiple fixed point learning problem via Poincaré maps.
IEEE Transactions on Robotics, 2022
Collaborative multi-agent robotic systems where agents coordinate by modifying a shared environme... more Collaborative multi-agent robotic systems where agents coordinate by modifying a shared environment often result in undesired dynamical couplings that complicate the analysis and experiments when solving a specific problem or task. Simultaneously, biologicallyinspired robotics rely on simplifying agents and increasing their number to obtain more efficient solutions to such problems, drawing similarities with natural processes. In this work we focus on the problem of a biologically-inspired multi-agent system solving collaborative foraging. We show how mean field techniques can be used to re-formulate such a stochastic multi-agent problem into a deterministic autonomous system. This de-couples agent dynamics, enabling the computation of limit behaviours and the analysis of optimality guarantees. Furthermore, we analyse how having finite number of agents affects the performance when compared to the mean field limit and we discuss the implications of such limit approximations in this multi-agent system, which have impact on more general collaborative stochastic problems.
Data processing work-flow
<p>D4D Dataset is processed for computation of IT-Matrix, which is processed to select and ... more <p>D4D Dataset is processed for computation of IT-Matrix, which is processed to select and cluster mobility profiles. Finally, consistency assessment/fusion of profiles with other sources of data, <i>O</i>(<i>l</i>, <i>t</i>) (which depends of the <i>l</i> location and <i>t</i> time variables), such as livelihood calendars provided by WFP (World Food Program), NDVI (Normalized Difference Vegetation Index [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0195714#pone.0195714.ref024" target="_blank">24</a>]) and Rain variables. Dark green rectangle represents information sources which are hidden or unknown in this study: raw Call Detail Records (CDRs); <i>h</i>(<i>t</i>), user home location; <i>E</i>(<i>l</i>, <i>t</i>), other external directly measurable variables (such as evolution of crops); and <i>I</i>(<i>l</i>, <i>t</i>), other social indicators (such as market prices).</p
Seasonal mobility profiles in each livelihood zone
<p>They are clustered with <i>k</i> = 3: yellow, red and orange. Each curve rep... more <p>They are clustered with <i>k</i> = 3: yellow, red and orange. Each curve represents z-scored values of the population count Livelihood zones 1-13 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0195714#pone.0195714.s004" target="_blank">S1 Fig</a>) are ordered up-down, left-right. Cyan curves show the rainfall estimations averaged by livelihood zone, whereas black curves show the NDVI estimation averaged by livelihood zone. Both rain and NDVI curves have been rescaled to fit the scale of the population count signatures.</p
Global behavior of a nonlinear dynamical systems: Analytical, computational and control aspects
ArXiv, 2018
Natural disasters affect hundreds of millions of people worldwide every year. Early warning, huma... more Natural disasters affect hundreds of millions of people worldwide every year. Early warning, humanitarian response and recovery mechanisms can be improved by using big data sources. Measuring the different dimensions of the impact of natural disasters is critical for designing policies and building up resilience. Detailed quantification of the movement and behaviours of affected populations requires the use of high granularity data that entails privacy risks. Leveraging all this data is costly and has to be done ensuring privacy and security of large amounts of data. Proxies based on social media and data aggregates would streamline this process by providing evidences and narrowing requirements. We propose a framework that integrates environmental data, social media, remote sensing, digital topography and mobile phone data to understand different types of floods and how data can provide insights useful for managing humanitarian action and recovery plans. Thus, data is dynamically re...
1 Title : Understanding social structures behind the six degrees of separation
Empirical evidence has proved that social networks are searchable, meaning that a short path from... more Empirical evidence has proved that social networks are searchable, meaning that a short path from one person to any other person can be collectively found, despite that each individual has only local information of the entire network. The structure of empirical social networks that allows these phenomena has not yet been completely uncovered, and this knowledge is important for communication systems and models of information spreading. In this work we evaluate diverse decentralized search strategies in social networks of over 25 million phone users from three countries. While the city of the target person is reached within a few hops almost independently of the origin and the routing strategy, we show, for the first time, that within cities, the strategies based on geographic information completely fail to reach the target. This failure occurs because the relationship between the social networks and their geographical space does fundamentally change within cities: social groups are ...
IEEE Access, 2021
In this paper, we present the physical foundations and the development of the thermodynamic part ... more In this paper, we present the physical foundations and the development of the thermodynamic part of a Modelica library with the fundamental components for modeling thermofluid systems. We have chosen Modelica because it is an object-oriented modeling language that allows an elegant design of the library, with a top-down conception that starts from very general components where we model the thermodynamic properties common to all simple substances and descend by inheritance to model the properties of each particular substance. To model the behavior of each component, we have used: classical thermodynamics to define the equilibrium states, the local equilibrium hypothesis of Classical Irreversible Thermodynamics to model the changes of state, and the port-Hamiltonian approach to obtain the equations of the system dynamics. With this formulation, we implement the thermodynamic behavior of ideal gases (including monatomic gases as a particular case), the 2073 substances defined for the CEA (Chemical Equilibrium with Applications) NASA Glenn computer program, the IAPWS Formulation 1995 for the Thermodynamic Properties of Water Substance for General and Scientific Use, and the Syltherm 800 HTF (Heat Transfer Fluid). We also define graphical symbols for each library component that facilitate modeling complex systems with simple drag-and-drop manipulations, component connection, and parameter selection. These symbols are a slightly modified version of those used in bond graphs to facilitate their reading and the representation of the structure of complex systems. We also show the modeling, simulation, and comparison for accuracy, performance, and scalability of some thermodynamic systems implemented with the Modelica Standard Library (MSL) and the proposed library. INDEX TERMS Bond graphs, Modelica language, object oriented modeling, port-Hamiltonian systems, thermodynamic systems, thermofluid systems.
IFAC Proceedings Volumes, 1998
Mobile robots can use sensor information to create a geometrical model of their environment. Alte... more Mobile robots can use sensor information to create a geometrical model of their environment. Alternatively, they can use sensor information directly without a geometrical interpretation, This paper presents two architectures, each implementing one of these approaches, The first part of the paper presents a sensor space representation architecture using a Self-Organizing Map as a perceptual leveL The second part of this article describes a system for autonomous navigation based on geometrical environment models.
ACM Transactions on Mathematical Software, 2016
VBF is a collection of C++ classes designed for analyzing vector Boolean functions (functions tha... more VBF is a collection of C++ classes designed for analyzing vector Boolean functions (functions that map a Boolean vector to another Boolean vector) from a cryptographic perspective. This implementation uses the NTL library from Victor Shoup, adding new modules that call NTL functions and complement the existing ones, making it better suited to cryptography. The class representing a vector Boolean function can be initialized by several alternative types of data structures such asTruth Table, Trace Representation, and Algebraic Normal Form (ANF), among others. The most relevant cryptographic criteria for both block and stream ciphers as well as for hash functions can be evaluated with VBF: it obtains the nonlinearity, linearity distance, algebraic degree, linear structures, and frequency distribution of the absolute values of the Walsh Spectrum or the Autocorrelation Spectrum, among others. In addition, operations such as equality testing, composition, inversion, sum, direct sum, brick...
Journal of Mathematical Analysis and Applications, 1990
A continuous-time dynamical system is constructed and analyzed in this paper to help locate all t... more A continuous-time dynamical system is constructed and analyzed in this paper to help locate all the zeros of nonlinear vector functions. Lyapunov stability technique is used to show that the zeros of the vector function become asymptotically stable equilibria for this dynamical system. A strict Lyapunov function is constructed to indicate local stability and to estimate the domains of attraction of all equilibria. Manifolds on which the Jacobian of the vector field is singular play a significant role in characterizing the global behavior of the system. Examples are provided to illustrate the extent of the theory. New computational techniques to determine all the zeros of a vector function can be developed based on the dynamical aspects of the theory given in this paper.
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Papers by Pedro J. Zufiria