Origin and evolution of ferroelectricity in the layered rare-earth-titanate, R2R_2Ti2_2O7_{7}, Lichtenberg phases

We report a systematic first-principles study based on density functional theory (DFT) of the structural and ferroelectric properties of the $R_2$Ti$_2$O$_{7}$ perovskite-related oxides with $R=$ La, Ce, Pr, and Nd. We show that, in all cases, the ferroelectric distortion to the ground-state polar $P2_1$ structure from its parent centrosymmetric $P2_1/m$ phase is driven by a single polar soft mode consisting of rotations and tilts of the TiO$_6$ octahedra combined with displacements of the $R$ ions. A secondary centrosymmetric distortion, which is stable in the parent structure, contributes substantially to the energy lowering of the ground state. We evaluate the trends in structure and polarization across the series as a function of $R$ and reconcile discrepancies in reported values of polarization in the literature. Our results confirm that the family of $R_2$Ti$_2$O$_{7}$ materials belong to the class of proper geometric ferroelectrics.Comment: 15 pages, 12 figures, 7 table

Thermoelastic Properties of Ringwoodite [Fe_x,Mg_(1-x)]_2SiO_4: Its Relationship to the 520 km Seismic Discontinuity

We combine density functional theory (DFT) within the local density approximation (LDA), the quasiharmonic approximation (QHA), and a model vibrational density of states (VDoS) to calculate elastic moduli and sound velocities of gamma-[Fe_x,Mg_(1-x)]_2SiO_4 (ringwoodite), the most abundant mineral of the lower Earth's transition zone (TZ). Comparison with experimental values at room-temperature and high pressure or ambient-pressure and high temperature shows good agreement with our first-principles findings. Then, we investigate the contrasts associated with the beta-to-gamma-[Fe_x,Mg_(1-x)]_2SiO_4 transformation at pressures and temperatures relevant to the TZ. This information offers clearly defined reference values to advance the understanding of the nature of the 520 km seismic discontinuity.Comment: 29 pages, 6 figures, 2 tables. Under Revie

Incremental Hierarchical Clustering driven Automatic Annotations for Unifying IoT Streaming Data

In the Internet of Things (IoT), Cyber-Physical Systems (CPS), and sensor technologies huge and variety of streaming sensor data is generated. The unification of streaming sensor data is a challenging problem. Moreover, the huge amount of raw data has implied the insufficiency of manual and semi-automatic annotation and leads to an increase of the research of automatic semantic annotation. However, many of the existing semantic annotation mechanisms require many joint conditions that could generate redundant processing of transitional results for annotating the sensor data using SPARQL queries. In this paper, we present an Incremental Clustering Driven Automatic Annotation for IoT Streaming Data (IHC-AA-IoTSD) using SPARQL to improve the annotation efficiency. The processes and corresponding algorithms of the incremental hierarchical clustering driven automatic annotation mechanism are presented in detail, including data classification, incremental hierarchical clustering, querying the extracted data, semantic data annotation, and semantic data integration. The IHCAA-IoTSD has been implemented and experimented on three healthcare datasets and compared with leading approaches namely- Agent-based Text Labelling and Automatic Selection (ATLAS), Fuzzy-based Automatic Semantic Annotation Method (FBASAM), and an Ontology-based Semantic Annotation Approach (OBSAA), yielding encouraging results with Accuracy of 86.67%, Precision of 87.36%, Recall of 85.48%, and F-score of 85.92% at 100k triple data

Elasticity of Diamond at High Pressures and Temperatures

We combine density functional theory within the local density approximation, the quasiharmonic approximation, and vibrational density of states to calculate single crystal elastic constants, and bulk and shear moduli of diamond at simultaneous high pressures and temperatures in the ranges of 0-500 GPa and 0-4800 K. Comparison with experimental values at ambient pressure and high temperature shows an excellent agreement for the first time with our first-principles results validating our method. We show that the anisotropy factor of diamond increases to 40% at high pressures and becomes temperature independent.Comment: 10 pages, 3 figures, 1 tabl

Security Guidelines for the Development of Accessible Web Applications through the implementation of intelligent systems

Due to the significant increase in threats, attacks and vulnerabilities that affect the Web in recent years has resulted the development and implementation of tools and methods to ensure security measures in the privacy, confidentiality and data integrity of users and businesses. Under certain circumstances, despite the implementation of these tools do not always get the flow of information which is passed in a secure manner. Many of these security tools and methods cannot be accessed by people who have disabilities or assistive technologies which enable people to access the Web efficiently. Among these security tools that are not accessible are the virtual keyboard, the CAPTCHA and other technologies that help to some extent to ensure safety on the Internet and are used in certain measures to combat malicious code and attacks that have been increased in recent times on the Web. Through the implementation of intelligent systems can detect, recover and receive information on the characteristics and properties of the different tools and hardware devices or software with which the user is accessing a web application and through analysis and interpretation of these intelligent systems can infer and automatically adjust the characteristics necessary to have these tools to be accessible by anyone regardless of disability or navigation context. This paper defines a set of guidelines and specific features that should have the security tools and methods to ensure the Web accessibility through the implementation of intelligent systems

A Review of Artificial Intelligence in the Internet of Things

Humankind has the ability of learning new things automatically due to the capacities with which we were born. We simply need to have experiences, read, study… live. For these processes, we are capable of acquiring new abilities or modifying those we already have. Another ability we possess is the faculty of thinking, imagine, create our own ideas, and dream. Nevertheless, what occurs when we extrapolate this to machines? Machines can learn. We can teach them. In the last years, considerable advances have been done and we have seen cars that can recognise pedestrians or other cars, systems that distinguish animals, and even, how some artificial intelligences have been able to dream, paint, and compose music by themselves. Despite this, the doubt is the following: Can machines think? Or, in other words, could a machine which is talking to a person and is situated in another room make them believe they are talking with another human? This is a doubt that has been present since Alan Mathison Turing contemplated it and it has not been resolved yet. In this article, we will show the beginnings of what is known as Artificial Intelligence and some branches of it such as Machine Learning, Computer Vision, Fuzzy Logic, and Natural Language Processing. We will talk about each of them, their concepts, how they work, and the related work on the Internet of Things fields

Subject Coordination Improvement through Automatic Generation of Meeting Minutes based on Email Communication

El proyecto consiste en la realización de una plataforma digital que permite la realización automática de actas de coordinación de asignaturas a partir de los hilos de las conversaciones establecidas en los envíos de correos electrónicos por parte de los diferentes equipos docentes participantes en dichas asignaturas. Las actas pueden generarse a partir de las conversaciones de los docentes, así como de la comunicación entre alumnos y docentes. Este trabajo se motiva en que las reuniones realizadas de forma virtual raramente van acompañadas de un acta donde se deja constancia de los participantes, de sus declaraciones, de las fechas en las que se realizaron las mismas y de las conclusiones a las que se llegaron. El principal objetivo es de dejar constancia de todos los trabajos de coordinación realizados de una forma sencilla, sin que para ello los intervinientes tengan que realizar ninguna tarea adicional, a partir de los correos enviados entre profesores alumnos de una asignatura. Estos correos se analizan y recopilan de forma automática. Después, se genera el acta en formato PDF, que puede ser leído por prácticamente cualquier dispositivo. La aplicación fue probada en dos asignaturas y se aportan capturas y la información relativa a su uso. La aplicación consiguió recopilar toda la información de los correos de forma automática y crear las actas.This project consists in the development of a digital platform to create meeting minutes for a subject in an automatic way. The data come from the email conversations of the professor of one subject, and the emails between professor and student. The motivation of this work is due to the fact that the virtual meetings normally has not a minute which leaves proof of the participants, participants’ statements, their dates, and conclusions. The main object is to leave proof of all the work of the professors in an easy and simple way. In this way, the participants will not have to make any additional task or work. These emails are analysed and gathered in a automate way. Then, the minutes are created in PDF, which can be read in almost any device. This application has been tested in two subjects and we provide information about its use. The application achieved gathering all the information of the emails in an automate way and created the meeting minutes