Improving the functional properties of (K0.5Na0.5)NbO3 piezoceramics by acceptor doping

ZrO2 and TiO2 modified lead-free (K0.5Na0.5)NbO3 (KNN) piezoelectric ceramics are prepared by a conventional solid-state reaction. The effect of acceptor doping on structural and functional properties is investigated. A decrease in the Curie temperature and an increase in the dielectric constant values are observed when doping. More interestingly, an increase in the coercive field E-c and remanent polarization P-r is observed. The piezoelectric properties are greatly increased when doping with small concentrations dopants. ZrO2 doped ceramic exhibits good piezoelectric properties with piezoelectric coefficient d(33) = 134 pC/N and electromechanical coupling factor k(p) = 35%. It is verified that nonlinearity is significantly reduced. Thus, the creation of complex defects capable of pinning the domain wall motion is enhanced with doping, probably due to the formation of oxygen vacancies. These results strongly suggest that compositional engineering using low concentrations of acceptor doping is a good means of improving the functional properties of KNN lead-free piezoceramic system. (C) 2014 Elsevier Ltd. All rights reserved.Postprint (published version

Language in social networks as a communication strategy: public administration, political parties and civil society

This paper studies the language of political actors on social networks from the concept of digital language with a communicative perspective. Attention is paid to tweets by political parties, public administrations and civil society related to Catalan politics over the last eight months. The main trends of digital language are confirmed for political language on Twitter, but are relativized by the majority use of a more formal register. In addition, the political language appears as hybrid, heterogeneous, multimodal, a continuation of the offline arena and with little narrative innovation. Within these general characteristics, the activation of innovative linguistic orthographic, lexical, syntactic or coherence elements draws specific strategies for each actor, without common features for the sectors but shows that they do converge at specific moments forming sociolects that seek to promote belonging to a community and protest against specific facts or the status quo.El artículo estudia el lenguaje de los actores políticos en redes sociales a partir del concepto de lenguaje digital desde una perspectiva comunicativa. Se examinan los tuits de los partidos políticos, las administraciones públicas y las organizaciones civiles relacionados con la política catalana durante los últimos ocho meses. Se confirman para el lenguaje político en Twitter la evolución general del lenguaje digital pero relativizado por el uso mayoritario de un registro formal. Además, el lenguaje político se perfila como híbrido, heterogéneo, multimodal, continuador de la temática off line y con escasa innovación narrativa. Los estilemas permiten detectar estrategias individualizadas e identidades lingüísticas con rasgos ortotipográficos, léxicos, uso de hashtag, iconos, enlaces o sintaxis propias de cada actor. No se detectan características comunes para cada uno de los tres sectores, únicamente algunos actores confluyen en momentos puntuales conformando sociolectos que buscan promover la pertenencia a una comunidad, la protesta contra hechos puntuales o contra el status quo

Macroscopic limit cycle via pure noise-induced phase transition

Bistability generated via a pure noise-induced phase transition is reexamined from the view of bifurcations in macroscopic cumulant dynamics. It allows an analytical study of the phase diagram in more general cases than previous methods. In addition using this approach we investigate patially-extended systems with two degrees of freedom per site. For this system, the analytic solution of the stationary Fokker-Planck equation is not available and a standard mean field approach cannot be used to find noise induced phase transitions. A new approach based on cumulant dynamics predicts a noise-induced phase transition through a Hopf bifurcation leading to a macroscopic limit cycle motion, which is confirmed by numerical simulation.Comment: 8 pages, 8 figure

Overview of the JET results in support to ITER

The 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L–H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H = 1 at βN ~ 1.8 and n/nGW ~ 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D–T campaign and 14 MeV neutron calibration strategy are reviewed.European Commission (EUROfusion 633053

S wave velocity structure below central Mexico using high-resolution surface wave tomography

Shear wave velocity of the crust below central Mexico is estimated using surface wave dispersion measurements from regional earthquakes recorded on a dense, 500 km long linear seismic network. Vertical components of regional records from 90 well-located earthquakes were used to compute Rayleigh-wave group-velocity dispersion curves. A tomographic inversion, with high resolution in a zone close to the array, obtained for periods between 5 and 50 s reveals significant differences relative to a reference model, especially at larger periods (>30 s). A 2-D S wave velocity model is obtained from the inversion of local dispersion curves that were reconstructed from the tomographic solutions. The results show large differences, especially in the lower crust, among back-arc, volcanic arc, and fore-arc regions; they also show a well-resolved low-velocity zone just below the active part of the Trans Mexican Volcanic Belt (TMVB) suggesting the presence of a mantle wedge. Low densities in the back arc, inferred from the low shear wave velocities, can provide isostatic support for the TMVB