311 research outputs found
Embedded Sensor System for Early Pathology Detection in Building Construction
Structure pathology detection is an important security task in building construction, which is performed by an operator by looking manually for damages on the materials. This activity could be dangerous if the structure is hidden or difficult to reach. On the other hand, embedded devices and wireless sensor networks (WSN) are becoming popular and cheap, enabling the design of an alternative pathology detection system to monitor structures based on these technologies. This article introduces a ZigBee WSN system, intending to be autonomous, easy to use and with low power consumption. Its functional parts are fully discussed with diagrams, as well as the protocol used to collect samples from sensor nodes. Finally, several tests focused on range and power consumption of our prototype are shown, analysing whether the results obtained were as expected or not
Chemical Oscillations out of Chemical Noise
The dynamics of one species chemical kinetics is studied. Chemical reactions
are modelled by means of continuous time Markov processes whose probability
distribution obeys a suitable master equation. A large deviation theory is
formally introduced, which allows developing a Hamiltonian dynamical system
able to describe the system dynamics. Using this technique we are able to show
that the intrinsic fluctuations, originated in the discrete character of the
reagents, may sustain oscillations and chaotic trajectories which are
impossible when these fluctuations are disregarded. An important point is that
oscillations and chaos appear in systems whose mean-field dynamics has too low
a dimensionality for showing such a behavior. In this sense these phenomena are
purely induced by noise, which does not limit itself to shifting a bifurcation
threshold. On the other hand, they are large deviations of a short transient
nature which typically only appear after long waiting times. We also discuss
the implications of our results in understanding extinction events in
population dynamics models expressed by means of stoichiometric relations
Geometrical approach to tumor growth
Tumor growth has a number of features in common with a physical process known
as molecular beam epitaxy. Both growth processes are characterized by the
constraint of growth development to the body border, and surface diffusion of
cells/particles at the growing edge. However, tumor growth implies an
approximate spherical symmetry that makes necessary a geometrical treatment of
the growth equations. The basic model was introduced in a former article [C.
Escudero, Phys. Rev. E 73, 020902(R) (2006)], and in the present work we extend
our analysis and try to shed light on the possible geometrical principles that
drive tumor growth. We present two-dimensional models that reproduce the
experimental observations, and analyse the unexplored three-dimensional case,
for which new conclusions on tumor growth are derived
Existence results for a fourth order partial differential equation arising in condensed matter physics
We study a higher order parabolic partial differential equation that arises
in the context of condensed matter physics. It is a fourth order semilinear
equation whose nonlinearity is the determinant of the Hessian matrix of the
solution. We consider this model in a bounded domain of the real plane and
study its stationary solutions both when the geometry of this domain is
arbitrary and when it is the unit ball and the solution is radially symmetric.
We also consider the initial-boundary value problem for the full parabolic
equation. We summarize our results on existence of solutions in these cases and
propose an open problem related to the existence of self-similar solutions.Comment: To appear in Mathematica Bohemic
Two species coagulation approach to consensus by group level interactions
We explore the self-organization dynamics of a set of entities by considering
the interactions that affect the different subgroups conforming the whole. To
this end, we employ the widespread example of coagulation kinetics, and
characterize which interaction types lead to consensus formation and which do
not, as well as the corresponding different macroscopic patterns. The crucial
technical point is extending the usual one species coagulation dynamics to the
two species one. This is achieved by means of introducing explicitly solvable
kernels which have a clear physical meaning. The corresponding solutions are
calculated in the long time limit, in which consensus may or may not be
reached. The lack of consensus is characterized by means of scaling limits of
the solutions. The possible applications of our results to some topics in which
consensus reaching is fundamental, like collective animal motion and opinion
spreading dynamics, are also outlined
Architecture for Multi-Technology Real-Time Location Systems
[Abstract]The rising popularity of location-based services has prompted considerable research in the field of indoor location systems. Since there is no single technology to support these systems, it is necessary to consider the fusion of the information coming from heterogeneous sensors. This paper presents a software architecture designed for a hybrid location system where we can merge information from multiple sensor technologies. The architecture was designed to be used by different kinds of actors independently and with mutual transparency: hardware administrators, algorithm developers and user applications. The paper presents the architecture design, work-flow, case study examples and some results to show how different technologies can be exploited to obtain a good estimation of a target position.[Resumen]El aumento de la popularidad de servicios localización-basados ha llevado a una investigación considerable en el campo de los sistemas de localización en interiores. Ya no hay solo tecnología para soportar estos sistemas, es necesario considerar la fusión de la información proveniente de sensores heterogéneos. Este papel presenta una arquitectura de software diseñada para un sistema de localización de híbridos donde nosotros podemos combinar información de múltiples tecnologías de sensor. La arquitectura fue diseñada para ser utilizada por diferentes tipos de actores independientemente y con transparencia mutua: los administradores de hardware, los desarrolladores de algoritmo y aplicaciones de usuario. El documento presenta el diseño de arquitectura, flujo de trabajo, ejemplos de estudios de caso y algunos resultados para mostrar cómo las diferentes tecnologías pueden explotarse para obtener una buena estimación de la posición de destinoMinisterio de Industria, Turismo y Comercio; IPT-020000-2010-35Ministerio de Educación y Ciencia; TEC2010-19545-C04-01Ministerio de Educación y Ciencia; CSD2008-0001
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