Molecular dynamics of free and graphite-supported Pt-Pd nanoparticles

The thermal characteristics of bimetallic Pt-Pd nanoparticles, both free and graphite-supported, were investigated through molecular dynamics simulations using quantum Sutton-Chen many-body potentials for the metal-metal interac- tions. The graphite substrate was represented as layers of fixed carbons sites and modeled with the Lennard-Jones po- tential model. The melting temperatures for bimetallic nanoparticles were estimated based on variations in thermody- namic properties such as potential energy and heat capacity. Melting temperatures of the nanoparticles were found to be considerably lower than those of bulk Pt and Pd. The Pt-Pd clusters exhibited a two-stage melting, where surface melt- ing of the external atoms is followed by homogeneous melting of the internal atoms. The melting transition temperature was found to increase when the particle is on the graphite support, with an increase at least 180 K higher than that of the same-sized free nanoparticle. The results of the density distributions perpendicular to the surface indicate that the Pd atoms have a tendency to remain at the surface, and the Pd atoms wet the graphite surface more than the Pt atoms, while root mean squares suggest that surface melting starts from the cluster surface, and surface melting was seen in both free and graphite-supported nanoparticles. Structural changes accompanying the thermal evolution were studied by the bond-orientational order parameter method

A machine learning approach to pedestrian detection for autonomous vehicles using High-Definition 3D Range Data

This article describes an automated sensor-based system to detect pedestrians in an autonomous vehicle application. Although the vehicle is equipped with a broad set of sensors, the article focuses on the processing of the information generated by a Velodyne HDL-64E LIDAR sensor. The cloud of points generated by the sensor (more than 1 million points per revolution) is processed to detect pedestrians, by selecting cubic shapes and applying machine vision and machine learning algorithms to the XY, XZ, and YZ projections of the points contained in the cube. The work relates an exhaustive analysis of the performance of three different machine learning algorithms: k-Nearest Neighbours (kNN), Naïve Bayes classifier (NBC), and Support Vector Machine (SVM). These algorithms have been trained with 1931 samples. The final performance of the method, measured a real traffic scenery, which contained 16 pedestrians and 469 samples of non-pedestrians, shows sensitivity (81.2%), accuracy (96.2%) and specificity (96.8%).This work was partially supported by ViSelTR (ref. TIN2012-39279) and cDrone (ref. TIN2013-45920-R) projects of the Spanish Government, and the “Research Programme for Groups of Scientific Excellence at Region of Murcia” of the Seneca Foundation (Agency for Science and Technology of the Region of Murcia—19895/GERM/15). 3D LIDAR has been funded by UPCA13-3E-1929 infrastructure projects of the Spanish Government. Diego Alonso wishes to thank the Spanish Ministerio de Educación, Cultura y Deporte, Subprograma Estatal de Movilidad, Plan Estatal de Investigación Científica y Técnica y de Innovación 2013–2016 for grant CAS14/00238

Estilo, características e influencia de Informe Robinson en el periodismo deportivo español

Informe Robinson es un programa de reportajes y documentales televisivos que muestran realidades e historias relacionadas con el deporte. Comandado por el periodista Michael Robinson (ya fallecido) y producido merced a un equipo de trabajo formado por redactores, productores, realizadores y editor, ha sido capaz de convivir en la televisión española durante más de una década de programas gracias a un estilo propio, una serie de características que podrían ser, para muchos estudiantes y profesionales, un faro y referencia a la hora de realizar un reportaje o documental televisivo. Su libro de estilo y su manera de contar historias han influenciado a toda una generación de periodistas que buscan reproducir sus principales características en nuevos trabajos que ven ahora la luz. A lo largo de este trabajo profundizaremos en los principales rasgos característicos por los cuales Informe Robinson ha gozado del amplio reconocimiento del público general y por los que ha sido capaz de crear obras emocionantes, que consiguen traspasar la pantalla y causar sensaciones en el espectador. ¿Cuál es el verdadero libro de estilo de Informe Robinson? ¿De qué forma se combina el relato y guion con elementos como la música de fondo, la pausa narrativa, las localizaciones, los silencios o los vídeos e imágenes de archivo? ¿Cómo se ve reflejado el estilo del programa en otras producciones dentro del periodismo deportivo en televisión en la actualidad?Universidad de Sevilla. Grado en Periodism

Industrial-like vehicle platforms for postgraduate laboratory courses on robotics

The interdisciplinary nature of robotics allows mobile robots to be used successfully in a broad range of courses at the postgraduate level and in Ph.D. research. Practical industrial-like mobile robotic demonstrations encourage students and increase their motivation by providing them with learning benefits not achieved with traditional educational robotic platforms. This paper presents VEGO, an industrial-like modular vehicle platform for robotic education with an appropriate infrastructure that has been demonstrated to be very useful at the postgraduate level. Besides learning engineering concepts, in performing industrial-like exercises, students develop valuable skills such as teamwork and the capacity to solve problems similar to those they may encounter in a real industrial environment. The developed infrastructure represents a valuable platform for robotic education that can be used in many different disciplines as a way to demonstrate how to cope with the difficulties and challenges related to the development of industrial infrastructure systems. The platform evaluation proved its ability to inculcate the expected engineering skills. A novel approach is adopted through the use of multidisciplinary and close-to-industrial-reality platforms developed under an incremental approach and using an open and customizable structure.This work was supported in part by the Fundación Séneca of the Murcia Region under Grant 15374/PI/10, the CICYT EXPLORE under Grant TIN2009-08572, and the INNPLANTA SiveLab, Ministry of Science and Innovation, Spain, under Grant INP-2011-0022-PCT-430000-ACT9

Hardware/software codesign methodology for fuzzy controller implementation

This paper describes a HW/SW codesign methodology for the implementation of fuzzy controllers on a platform composed by a general-purpose microcontroller and specific processing elements implemented on FPGAs or ASICs. The different phases of the methodology, as well as the CAD tools used in each design stage, are presented, with emphasis on the fuzzy system development environment Xfuzzy. Also included is a practical application of the described methodology for the development of a fuzzy controller for a dosage system

Statistical distribution of the estimator of Weibull modulus

3 pages, 3 figures.The Weibull statistic has been widely used to study the inherent scatter existing in the strength properties of many advanced materials, as well as in the fracture toughness of steels in the ductile-brittle transition region.The authors are indebted to the Fundación Ramón Areces (Área de Materiales, IX Concurso Nacional) for its financial support of this research.Publicad

Statistical analysis of the mechanical properties of composite materials

7 pages, 6 figures.The Weibull statistic is currently used in designing mechanical components made of composite materials. This work presents useful formulae to describe the behaviour of the Weibull modulus estimator, which in turn may be described by means of a three-parameter Weibull distribution. Expressions for the parameters of this latter distribution, dependent on the sample size, are also given in the paper, so, the percentage points, published until now in tabular form, may be directly calculated. Empirical expressions are derived for determining the A-basis and the B-basis material properties as a function of the sample size.The authors are indebted to the Fundación Ramón Areces (Área de Materiales, IX Concurso Nacional) for the financial support of this research.Publicad

On the estimation of percentiles of the Weibull distribution

3 pages, no figures.Advanced ceramics exhibit brittle behavior. The lack of ductility and the presence of flaws and defects of different sizes and orientations lead to scatter in failure strength. This variability depends also on the specimen size, stress distribution and stress state. The Weibull theory explains correctly this dependence, so the fracture strength of ceramic materials has been studied using the Weibull statistic as recommended by ASTM Standards for reporting uniaxial strength data of these materials.The authors are indebted to the Fundación Ramón Areces (Área de Materiales, IX Concurso Nacional) for its financial support of this research.Publicad

Utilizando ARMSim y QtARMSim para la docencia de Arquitectura de Computadores

Muchos de los objetivos formativos de las asignaturas de introducción a la Arquitectura de Computadores se centran en aquellos aspectos que conforman la visión que un programador en lenguaje ensamblador tiene de un computador. Por regla general, para definir dichos objetivos se suele utilizar una arquitectura de computador concreta, que normalmente se selecciona con el doble criterio de que sea lo más sencilla posible y, a la vez, motive al estudiantado. La arquitectura ARM es una candidata idónea como vehículo conductor en la docencia de Arquitectura de Computadores. Por un lado, al estar basada en la arquitectura RISC (Reduced Instruction Set Computer), es relativamente sencilla. Por otro, se trata de una arquitectura actual y ampliamente difundida (especialmente en dispositivos móviles, smartphones y tabletas), lo que motiva al estudiantado. Para poder realizar prácticas sobre ARM es conveniente disponer de un simulador o de una herramienta de desarrollo sobre una máquina ARM. Puesto que dicha materia se explica en los primeros cursos, conviene que la aplicación seleccionada sea sencilla de utilizar y lo suficientemente flexible. Por otro lado, conviene que sea software libre, para poder adaptarla en caso necesario, y también multiplataforma y gratuita, para facilitar que el estudiante que lo desee pueda instalarla en su propio equipo. Tras evaluar distintas opciones, finalmente se optó por desarrollar y liberar un simulador propio de ARM, ARMSim, y una interfaz gráfica para dicho simulador, QtARMSim. El motor de simulación, ARMSim, y su interfaz, QtARMSim, han sido utilizados durante el curso 2014–15. Las críticas recibidas, tanto por los estudiantes como por los profesores de laboratorio, han sido muy positivas.Many of the training objectives of the Introduction to Computer Architecture modules focus on those aspects that conform the vision that an assembly language programmer has about a computer. As a rule, in order to define those objectives a concrete computer architecture is used following the following criteria: simplicity and ability to motivate students. ARM architecture is an ideal candidate for the didactics of Computer Architecture. On the one hand, being based on RISC architecture (Reduced Instruction Set Computer) it is rather simple. On the other, it is widely spread contemporary architecture (especially in mobile phones, smartphones and tablets), something that motivates students. In order to carry out ARM practice it would be convenient to have a simulator or a development tool on an ARM machine. Given the fact that this module is taught during the first academic years, it would also be convenient that the application selected was easy to use and flexible enough. Besides, it would be a good idea that it used freeware in order to be adapted if necessary, besides being free of charge and cross-platform-based so the students may install it in their own computers. After assessing several options, an ARM simulator (ARMSim) as well as a graphic interface for the latter (QtARMSim) were finally developed. The simulation engine, ARMSim, as well as its interface, QtARMSim, were used during the 2014/2015 academic year. The feedback received from both the students and lab lecturers have been remarkably positive

Simulación numérica tridimensional de ensayos de fractura dinámica en dispositivos de barra Hopkinson modificada

6 pages, 10 figures.-- Contributed to: "XXI Encuentro del Grupo Español de Fractura" (Punta Umbría, Huelva, Spain, Mar 24-26, 2004).[EN] This work presents a three-dimensional Finite Element analysis of Dynamic three point bending fracture tests performed in a modified Split Hopkinson Pressure Bar, including the projectile, the incident bar, the specimen and the supporting device. The influence of different parameters, such as the specimen thickness, crack length and impact velocity of the projectile on the critical stress intensity factor is analyzed. To obtain the instant at which the crack starts to grow, a local fracture criteria is applied, considering that crack begins its propagation when a critical stress at a characteristic distance of the crack tip is reached. Numerical results show that critical stress intensity factor decreases with specimen thickness, projectile impact velocity and initial crack length.[ES] En este trabajo se presenta un análisis numérico tridimensional, por el método de los Elementos Finitos, de los ensayos de flexión dinámica que se pueden realizar en dispositivos experimentales basados en modificaciones de la barra Hopkinson, incluyendo la modelización del proyectil, la barra incidente, la probeta y su sistema de apoyo. Se analiza la influencia de diferentes parámetros como son el espesor de la probeta, la longitud de la fisura con relación al canto de la probeta y la velocidad de impacto en el valor crítico del factor de intensidad de tensiones. Para obtener dicho valor crítico, se ha utilizado un criterio local de fractura que considera que la fisura progresa de manera inestable cuando se alcanza una tensión crítica a una distancia característica del extremo de la fisura. Los resultados numéricos ponen de manifiesto que el citado valor crítico disminuye a medida que aumenta el espesor de la probeta, la velocidad de impacto del proyectil, y el tamaño de la fisura inicial.Publicad