Superionicity and Polymorphism in Calcium Fluoride at High Pressure

We present a combined experimental and computational first-principles study of the superionic and structural properties of CaF2 at high P-T conditions. We observe an anomalous superionic behavior in the low-P fluorite phase that consists in a decrease of the normal-> superionic critical temperature with compression. This unexpected effect can be explained in terms of a P-induced softening of a zone-boundary $X$ phonon which involves exclusively fluorine displacements. Also we find that superionic conductivity is absent in the high-P cotunnite phase. Instead, superionicity develops in a new low-symmetry high-T phase that we identify as monoclinic (space group P2_1/c). We discuss the possibility of observing these intriguing phenomena in related isomorphic materials.Comment: 5 pages, 5 figure

Estudio de ponderación multicriterio de los requisitos en viviendas para personas con necesidades especiales.

En este trabajo se estudian los distinto tipos de discapacidades que existen actualmente en el mundo, se investiga qué requisitos necesitan estas personas para poder desarrollar su vida con autonomía dentro de su vivienda, y se propone un sistema de ponderación de las viviendas para saber cómo de accesibles son. Con este sistema de ponderación se pretende proponer criterios de viviendas adecuadas para las necesidades especiales de las personas que padecen de una discapacidad. El trabajo se ha llevado a cabo en las siguientes fases: El estudio del contexto normativo tanto a nivel nacional como a nivel internacional, con el que se busca crear un marco desde el cual partir para entender la situación en la que se encuentran las personas con necesidades especiales. Indagar en los problemas que estas personas encuentran en su día a día, en sus viviendas y en el entorno, pudiendo así identificar los puntos más importantes a tener en cuenta en la accesibilidad de las viviendas. Identificar los indicadores que fomentan la accesibilidad de las viviendas a partir de los problemas encontrados. Priorizar los indicadores más relevantes para asegurar la accesibilidad en viviendas de personas con necesidades especiales

Few layers graphene-based electrocatalysts for ORR synthesized by electrochemical exfoliation methods

Graphene-based materials were synthesized by electrochemical exfoliation method (cathodic method) starting from a graphite sheet. In the established methodology, an initial immersion in H2SO4 was applied, followed by cathodic expansion in potassium sulphate, where the effect of the applied voltage was studied. Finally, by ultrasound treatment, the exfoliation was achieved to produce a dispersion of few layer graphene material. Once the optimum procedure was established, Pt nanoparticles were incorporated using H2PtCl6.6H2O. This incorporation was studied at each stage of the graphene-based material synthesis to determine which was the most adequate to obtain the highest Pt dispersion and the best distribution of the Pt nanoparticles. In this sense, the incorporation of Pt in the graphene-based material colloidal dispersion by stirring for 3 h and sonication for 1 h, results in Pt nanoparticles with an average size of around 1 nm with an excellent distribution in the carbon material. The performance of this catalyst was compared with the commercial Pt/C electrocatalyst, showing a great oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) activity, exceeding it by far when comparing the mass-specific activity (A gPt−1) In addition, it presents excellent stability and selectivity toward the 4-electron pathway in ORR, which is the most energy-efficient, and using half of the platinum loading compared to the commercial material.The authors would like to thank PID2019-105923RB-I00 and PID2021-123079OB-I00 projects funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, and the Generalitat Valenciana (GRISOLIA/2020/114) for the financial support

Mejora de los procesos de gestión para la sostenibilidad de la calidad de las relaciones comunitarias en una empresa minera

En el mundo globalizado el uso de las tecnologías de la información y comunicación se está volviendo casi una obligación para todos los negocios para poder lograr obtener un mejor rendimiento en sus procesos, gestionar sus recursos e inteligencia competitiva. Sin embargo, siendo el sector minero uno de los que mueven y generan mayor cantidad de dinero son las empresas que menos usan las tecnologías de la información y no generan innovación. Las empresas mineras si bien las operaciones y venta de los minerales son procesos que ellos tienen el control uno de los factores que les genera mayores pérdidas son los conflictos sociales que se generan alrededor de las operaciones de la mina. Las empresas mineras conociendo sobre todos esos problemas establecen un área de gestión de relaciones comunitarias, sin embargo, sus acciones son ineficientes porque los conflictos siguen surgiendo en las comunidades alrededor de las operaciones de la mina. Aunque uno podría pensar que se realiza actividades equivocadas para gestionar las relaciones comunitarias, de acuerdo al análisis que se realizó para la presente tesis se develo que el principal problema es que no pueden gestionar toda la información de las comunidades ni de sus propias actividades porque no usan ninguna herramienta tecnológica para sus actividades, todo lo contrario el personal utiliza medios muy tradicionales (cuadernos, hojas, entre otras) o muchas veces no utilizan ningún medio físico y solo su memoria para recordar. La presente tesis buscara mejorar la calidad de las relaciones entre la población y las mineras por medio de una plataforma que integra una parte web y una aplicación TIC. La primera captura y administra los datos/información con el fin de monitorear y controlar el desarrollo de dicha relación. El segundo gestiona el conocimiento y los proyectos eficientemente; a su vez, se mostrarán alertas georreferenciadas para observar el estado de las zonas, el grado de desarrollo que se está generando el cual ayudará a tomar mejores decisiones para la prevención de conflictos.Tesi

Using a RGB-D camera for 6DoF SLAM

This paper presents a method for fast calculation of the egomotion done by a robot using visual features. The method is part of a complete system for automatic map building and Simultaneous Localization and Mapping (SLAM). The method uses optical flow in order to determine if the robot has done a movement. If so, some visual features which do not accomplish several criteria (like intersection, unicity, etc,) are deleted, and then the egomotion is calculated. We use a state-of-the-art algorithm (TORO) in order to rectify the map and solve the SLAM problem. The proposed method provides better efficiency that other current methods.These authors want to express their gratitude to Spanish Ministry of Science and Technology (MYCIT) and the Research and Innovation Vice-president Office of the University of Alicante for their financial support through the projects DPI2009-07144 and GRE10-16, respectively

Evolution of structural and electronic properties of TiSe2 under high pressure

A pressure-induced structural phase transition and its intimate link with the superconducting transition was studied for the first time in TiSe2 up to 40 GPa at room temperature using X-ray diffraction, transport measurement, and first-principles calculations. We demonstrate the occurrence of a first-order structural phase transition at 4 GPa from the standard trigonal structure (S.G.P3¯m1) to another trigonal structure (S-G-P3¯c1). Additionally, at 16 GPa, the P3¯c1 phase spontaneously transforms into a monoclinic C2/m phase, and above 24 GPa, the C2/m phase returns to the initial P3¯m1 phase. Electrical transport results show that metallization occurs above 6 GPa. The charge density wave observed at ambient pressure is suppressed upon compression up to 2 GPa with the emergence of superconductivity at 2.5 GPa, with a critical temperature (Tc) of 2 K. A structural transition accompanies the emergence of superconductivity that persists up to 4 GPa. The results demonstrate that the pressure-induced phase transitions explored by the experiments along with the theoretical predictions may open the door to a new path for searching and controlling the phase diagrams of transition metal dichalcogenides.C.C. acknowledges support from the Spanish Ministry of Science, Innovation, and Universities under the “Ramon y Cajal” fellowship RYC2018-024947-I.Peer ReviewedPostprint (author's final draft

Computational design of locally resonant acoustic metamaterials

The so-called Locally Resonant Acoustic Metamaterials (LRAM) are considered for the design of specifically engineered devices capable of stopping waves from propagating in certain frequency regions (bandgaps), this making them applicable for acoustic insulation purposes. This fact has inspired the design of a new kind of lightweight acoustic insulation panels with the ability to attenuate noise sources in the low frequency range (below 5000 Hz) without requiring thick pieces of very dense materials. A design procedure based on different computational mechanics tools, namely, (1) a multiscale homogenization framework, (2) model order reduction strategies and (3) topological optimization procedures, is proposed. It aims at attenuating sound waves through the panel for a target set of resonance frequencies as well as maximizing the associated bandgaps. The resulting design’s performance is later studied by introducing viscoelastic properties in the coating phase, in order to both analyse their effects on the overall design and account for more realistic behaviour. The study displays the emerging field of Computational Material Design (CMD) as a computational mechanics area with enormous potential for the design of metamaterial-based industrial acoustic parts.Peer ReviewedPostprint (author's final draft