Evaluation of a Fall Alerting System based on a Convolutional Deep Neural Network

Artículo sobre detección de caídas con redes neuronales profundasOwing to the effects of falls on quality of life of the elderly, automatic fall detection systems (FDS) have become a key research topic in the ambit of telecare. This works assesses the performance of convolutional neural networks when they are applied to identify fall accidents in a wearable FDS provided with a tri-axial accelerometer. The evaluation of the detection algorithm is carried out by employing a benchmarking repository with a wide set of traces captured from a wide group of volunteers that executed a programmed series of Activities of the Daily Living (ADLs) and emulated falls. Results show that the CNN can properly distinguish both types of movements with a success rate (specificity and sensitivity) around 99%.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Contribution of reversible processes to the non-linear dielectric response in hard lead zirconate titanate ceramics

Se estudia la dependencia entre la constante dieléctrica y las pérdidas con el campo eléctrico aplicado, así como entre la constante dieléctrica y las pérdidas dieléctricas. Los resultados muestran que las cerámicas PZT duras no pueden ser decritas por el modelo de Rayleigh, pues la respuesta histerética de estos materiales no puede ser atribuida exclusivamente a la contribución de procesos irreversibles. Las medidas experimentales muestran la existencia de procesos reversibles, relacionados con movimientos de arqueo de dominios que contribuyen a la constante dieléctrica sin producir pérdidas. Esta contribución reversible es independiente del envejecimiento de la cerámica.Peer Reviewe

Evolución de la dentición en la transición Mesolítico-Neolítico de la Península Ibérica: un modelo de sustitución poblacional

Se han medido las variables métricas de la dentición del yacimiento de época mesolítica (7500-6500 a.C.), procedentes del yacimiento de La Oliva (Valencia) y se han comparado con las de otras poblaciones prehistóricas. Estas variables permiten situar esta población en el contexto europeo y extrapolar, mediante el análisis de árboles filogenéticos, los movimientos y relaciones poblacionales del Neolítico en Europa. De esta forma se observa que La Oliva forma parte de un antiguo grupo poblacional ancestral, bastante distanciado de las poblaciones mesolíticas contemporáneas del resto de Europa y de las poblaciones neolíticas posteriores. Parece, a su vez, que estas poblaciones neolíticas las substituirían casi completamente sin mestizaje aparente. Estos resultados se han contrastado y contrastado mediante análisis de variables métricas craneales

Nonlinear behavior in a piezoelectric resonator: a method of analysis

Theories used for understanding nonlinear behavior of piezoelectric resonators are usually only valid for a given range of amplitudes. Thus, important discrepancies can sometimes be observed between theory and experiment. In this work, a simplified model of the resonator is assumed in order to extend the analysis of nonlinear behavior to any kind of nonlinear function, without a significant increase of mathematical complexity. Nevertheless, nonlinearities are considered to be weak enough to be taken as perturbations. An asymptotic method is used to obtain the first and second order perturbations of the response to an harmonic excitation applied to the system, and each one is separated into Fourier series. Nonlinearity is described by two functions-/spl Phi/, (S,D,S/spl dot/,D/spl dot/) and /spl Psi/ (S,D,S/spl dot/,D/spl dot/)-that must be added to the constitutive equations that give T and E as functions of S and D. These functions can be split into their symmetrical and antisymmetrical parts, which have different incidence over the perturbation terms. In order to simplify the problem, no mechanical excitation is considered, the electrical one is taken as strictly harmonic, and the current rather than the e.m.f. is taken as initial data. As an application example, this method is applied in order to find the second harmonic generation for a particular kind of nonlinearity.Peer ReviewedPostprint (published version

Extrinsic behaviour of PZT ceramics near the morphotropic phase transition

The aim of this work is to study the dependence of the linear and non-linear dielectric, piezoelectric and mechanical coefficients on the Ti fraction in PZT ceramic compositions near the morphotropic phase boundary. The dependence of these coefficients with the defect concentration is also analysed. Special attention is given to the extrinsic piezoelectric measurements related to the domain wall movement. Since the non-linear behaviour is produced by the extrinsic phenomenon, the non-linear measurements provide a good extrinsic characterization of materials. In all cases the physical explanation of the behaviour is sought.Peer Reviewe

Influence of extrinsic contribution on the macroscopic properties of hard and soft lead zirconate titanate ceramics

In this work, the contribution of the extrinsic effect to the macroscopic properties in soft and hard lead zirconate titanate ceramics is directly evaluated. Close to the room temperature, poled hard ceramics show an anomalous behavior, which is notably different from that of soft ceramics, not only in dielectric but also in piezoelectric and elastic responses. Hence, at room temperature their properties are thermally stable and the losses are unusually low. It is suggested that two mechanisms are present, with one mechanism inhibiting the other.Peer ReviewedPostprint (published version

Unexpected dielectric response in lead zirconate titanate ceramics: The role of ferroelectric domain wall pinning effects

Temperature dependent dielectric response has been measured in Pb(Zr1-xTix)O-3 ceramics. Samples of different compositions (x=0.40, 0.47, and 0.60), pure and doped with Nb-or Fe, were studied at temperatures between 15 and 700 K and in the frequency range from 100 Hz to 1 MHz. Unexpected dielectric behavior has been found around room temperature. Anomalous temperature dependent permittivity is observed in pure and Fe-doped samples but not in Nb-doped samples. The anomaly appears related to the presence of oxygen vacancies but not on the sample crystallographic phase. The authors suggest that the anomaly may be a manifestation of the domain wall pinning effect. (C) 2007 American Institute of Physics.Peer ReviewedPostprint (published version

Frontiers and political agregations in Celtiberia: data for a debate

Proyecto de investigación “Entre la paz y la guerra: alianzas, confederaciones y diplomacia en el Occidente mediterráneo (siglos III-I a.C.)” (Ref. HAR2011-27782), Plan Nacional I+D+I, Ministerio de Economía y Competitividad, Gobierno de España. Grupo de Investigación Occidens UIB-UAM (www.occidens.es).En el contexto de la II Guerra Púnica (218-206 a.C. para la península Ibérica) y el proceso de expansión romana en Celtiberia (ca. 195-133 a.C.), nuestro objetivo se centra en poner en valor la dimensión espacial, territorial, de las dinámicas históricas, delimitando su papel en la generación de identidades en el mundo celtibérico. Planteamos, en primer lugar, un análisis diacrónico y una contextualización geopolítica de las referencias a coaliciones militares en el interior peninsular, destacando las alianzas defensivas formadas en la década de los años 90 del siglo II a.C. para tratar de contener el avance romano en la línea del Tajo, así como otros ejemplos de coaliciones conocidas para las guerras celtibéricas de mediados de siglo. Estudiamos también, seguidamente, la estructura interna de las póleis celtibéricas, subrayando su composición mixta (oppidum-ager), y reconstruyendo algunos datos sobre la gestión local de los recintos defensivos y de los límites de los territorios. Finalmente, analizamos los tres niveles político-militares identificables en el mundo celtibérico y su correlato territorial. Partiendo del concepto básico de civitas (en terminología latina), se discute la naturaleza suprapolítica y/o étnica de los populi, para analizar finalmente los mecanismos de generación de grandes alianzas y coaliciones, cuya perpetuación en el tiempo habría propiciado también la aparición de elementos identitarios regionales.In the context of the Second Punic War (218-206 BC for the Iberian Peninsula) and the process of Roman expansion in Celtiberia (ca. 195-133 BC), we underline the importance of the territorial, spatial dimension of the historical dynamics, defining its role in the generation of identities in the Celtiberian world. We propose, firstly, a diachronic analysis and a geopolitical contextualization of references to military coalitions in the inner Iberian Peninsula, paying special attention to the defensive alliances formed in the early 90s of the 2nd century BC trying to contain the Roman advance on the line of the river Tagus. We consider also other examples of coalitions during the central decades of the 2nd century. Later on, we deal with the internal structure of the Celtiberian póleis, stressing its mixed composition (oppidum-ager), and reconstructing some data on the local management of the defensive structures and the limits of the territories. Finally, we analyze the three political-military layers that can be identified in the Celtiberian world and its territorial correlate. Starting from the basic concept of civitas (in Latin terminology), the suprapolitical and / or ethnic nature of the populi is discussed, to analyze, finally, the mechanisms of generation of large alliances and coalitions, whose perpetuation in time have also led to the emergence of elements of regional identity

Cross-dataset evaluation of wearable fall detection systems using data from real falls and long-term monitoring of daily life

The evaluation of fall detection systems based on wearables is controversial as most studies in the literature benchmark their proposals against falls that are simulated by experimental subjects under unrealistic laboratory conditions. In order to systematically investigate the suitability of this procedure, this paper evaluates a wide set of artificial intelligence algorithms used for fall detection, when trained with a large number of datasets containing acceleration samples captured during the emulation of falls and ordinary movements and then tested with the signals of both actual falls and long-term traces collected from the constant monitoring of users during their daily routines. The results, based on a large number of repositories, show a remarkable degradation in all performance metrics (sensitivity, specificity and false alarm hourly rate) with respect to the typical case in which the detectors are tested with the same types of laboratory movements for which they were trained.Funding for open access charge: Universidad de Málaga / CBU