Klein paradox between transmitted and reflected Dirac waves on Bour surfaces

It is supposed the existence of a curved graphene sheet with the geometry of a Bour surface $B_{n}$, such as the catenoid (or helicoid), $B_{0}$, and the classical Enneper surface, $B_{2}$, among others. In particular, in this work, the propagation of the electronic degrees of freedom on these surfaces is studied based on the Dirac equation. As a consequence of the polar geometry of $B_{n}$, it is found that the geometry of the surface causes the Dirac fermions to move as if they would be subjected to an external potential coupled to a spin-orbit term. The geometry-induced potential is interpreted as a barrier potential, which is asymptotically zero. Furthermore, the behaviour of asymptotic Dirac states and scattering states are studied through the Lippmann-Schwinger formalism. It is found that for surfaces $B_{0}$ and $B_{1}$, the total transmission phenomenon is found for sufficiently large values of energy, while for surfaces $B_{n}$, with $n\geq 2$, it is shown that there is an energy point $E_{K}$ where Klein's paradox is realized, while for energy values $E\gg E_{K}$ it is found that the conductance of the hypothetical material is completely suppressed, $\mathcal{G}(E)\to 0$.Comment: 31 pages, 9 figure

Tecnologías para el manejo de metadatos en artículos científicos

(Eng) The use of Semantic Web technologies has been increasing, so it is common using them in different ways. This article evaluates how these technologies can contribute to improve the indexing in articles in scientific journals. Initially, there is a conceptual review about metadata. Later, studying the most important technologies for the use of metadata in Web and, this way, choosing one of them to apply it in the case of study of scientific articles indexing, in order to determine the metadata based in those used in impact research journals, and building a model for indexing scientific articles using Semantic Web technologies.(Spa) El uso de tecnologías de la Web Semántica ha venido acrecentándose, por lo que es común usarlo en diferentes aspectos. Este trabajo evalúa como estas tecnologías pueden contribuir a mejorar la indexación de artículos en revistas científicas. Inicialmente, se hace una revisión conceptual de los metadatos, para posteriormente estudiar las tecnologías más importantes para el uso de metadatos en la Web y, de esta manera, escoger una para aplicarla en el caso de estudio de indexación de artículos científicos, determinando los metadatos con bases en los usados por las revistas de investigación de impacto y construir un modelo para la indexación de artículos científicos usando una tecnología de Web Semántica

Exploiting graphic processing units parallelism to improve intelligent data acquisition system performance in JET's correlation reflectometer

The performance of intelligent data acquisition systems relies heavily on their processing capabilities and local bus bandwidth, especially in applications with high sample rates or high number of channels. This is the case of the self adaptive sampling rate data acquisition system installed as a pilot experiment in KG8B correlation reflectometer at JET. The system, which is based on the ITMS platform, continuously adapts the sample rate during the acquisition depending on the signal bandwidth. In order to do so it must transfer acquired data to a memory buffer in the host processor and run heavy computational algorithms for each data block. The processing capabilities of the host CPU and the bandwidth of the PXI bus limit the maximum sample rate that can be achieved, therefore limiting the maximum bandwidth of the phenomena that can be studied. Graphic processing units (GPU) are becoming an alternative for speeding up compute intensive kernels of scientific, imaging and simulation applications. However, integrating this technology into data acquisition systems is not a straight forward step, not to mention exploiting their parallelism efficiently. This paper discusses the use of GPUs with new high speed data bus interfaces to improve the performance of the self adaptive sampling rate data acquisition system installed on JET. Integration issues are discussed and performance evaluations are presente

LED street lighting: A power quality comparison among street light technologies

High-pressure sodium lamps are currently the main lamps used in public lighting. However, the possibility of using high-power light emitting diode (LEDs) for street lighting is growing continuously due to their greater energy efficiency, robustness, long life and light control. The aim of this paper is to study the power quality of high-power lighting networks based on LED and high-pressure sodium lamps. Both electromagnetic and dimmable electronic ballasts, which can dim the lamp output smoothly and uniformly, have been used connected to high-pressure sodium lamps. High-pressure sodium lamps connected to electronic equipment have been tested with different arc power levels using dimming on a 230V power supply. The study presented in this paper is completely based on measurements, including harmonic currents in the frequency range up to 150 kHz for all the technologies. The main results show a broadband spectrum in LED lamps which confirms other research in Fuorescent lamps powered by high-frequency ballasts. Results also indicate a decrease in the harmonic value with increasing harmonic order, and a decrease in the harmonic value at half load (60%) compared with full load (100%). Although total harmonic distortion of the current is lower with highpressure sodium lamps connected to electronic rather than electromagnetic ballasts, LED lamps achieved the lowest total harmonic distortion of curren

Los espectadores ante la violencia televisiva: funciones, efectos e interpretaciones situadas

La investigación sobre violencia en televisión se ha orientado a una labor cuantificadora de lo emitido o a la práctica experimental para determinar sus posibles efectos. El presente trabajo se centra en cómo interpretan los espectadores las imágenes de violencia. Basado en el análisis de 16 grupos de discusión, muestra las dimensiones que mediatizan los posibles efectos de la violencia televisiva; en concreto, las condiciones en que se reconocen y clasifican escenas de violencia, las funciones de la imagen violenta, las emociones y sentimientos despertados por ella y los procesos de identificación que se pueden producir con los personajes de las escenas

Fast approach for unsteady flow routing in complex river networks based on performance graphs

We present a new model for unsteady flow routing through dendritic and looped river networks based on performance graphs. The model builds upon the application of Hydraulic Performance Graph (HPG) to unsteady flow routing introduced by Gonzalez-Castro (2000) and adopts the Volume Performance Graph (VPG) introduced by Hoy and Schmidt (2006). The HPG of a channel reach graphically summarizes the dynamic relation between the flow through and the stages at the ends of the reach under gradually varied flow (GVF) conditions, while the VPG summarizes the corresponding storage. Both, the HPG and VPG are unique to a channel reach with a given geometry and roughness, and can be computed decoupled from unsteady boundary conditions by solving the GVF equation for all feasible conditions in the reach. Hence, in the proposed approach, the performance graphs can be used for different boundary conditions without the need to recompute them. Previous models based on the performance graph concept were formulated for routing through single channels or channels in series. The new approach expands on the use of HPG/VPGs and adds the use of rating performance graphs for unsteady flow routing in dentritic and looped networks. We exemplify the applicability of the proposed model to subcritical unsteady flow routing through a looped network and contrast its simulation results with those from the well-known unsteady HEC-RAS model. Our results show that the present extension of application of the HPG/VPGs appears to inherit the robustness of the HPG routing approach in Gonzalez-Castro (2000). The unsteady flow model based on performance graphs presented here can be extended to include supercritical flows.Keywords: Looped network, Hydraulic routing, Modeling, Simulation, Unsteady flow, Dendritic network, River hydraulics, Flooding, Flow routingKeywords: Looped network, Hydraulic routing, Modeling, Simulation, Unsteady flow, Dendritic network, River hydraulics, Flooding, Flow routin

A Study on Physical Exercise and General Mobility in People with Cerebral Palsy: Health through Costless Routines

[Abstract] Sedentary behavior (SB) is a common problem that may produce health issues in people with cerebral palsy (CP). When added to a progressive reduction in motor functions over time, SB can lead to higher percentages of body fat, muscle stiffness and associated health issues in this population. Regular physical activity (RPA) may prevent the loss of motor skills and reduce health risks. In this work, we analyzed data collected from 40 people (20 children and teenagers, and 20 adults) who attend two specialist centers in Seville to obtain an up-to-date picture regarding the practice of RPA in people with CP. Roughly 60% of the participants showed mostly mid/severe mobility difficulties, while 38% also had communicative issues. Most of the participants performed light-intensity physical activity (PA) at least once or twice a week and, in the majority of cases, had a neutral or positive attitude to exercising. In the Asociación Sevillana de Parálisis Cerebral (ASPACE) sample test, the higher the International Classification of Functioning, Disability and Health (ICF), the higher the percentage of negative responses to doing exercise. Conversely, in the Centro Específico de Educación Especial Mercedes Sanromá (CEEEMS), people likes PA but slightly higher ratios of positive responses were found at Gross Motor Function Classification System (GMFCS) levels V and II, agreeing with the higher personal engagement of people at those levels. We have also performed a literature review regarding RPA in CP and the use of low-cost equipment. As a conclusion, we found that RPA produces enormous benefits for health and motor functions, whatever its intensity and duration. Costless activities such as walking, running or playing sports; exercises requiring low-cost equipment such as elastic bands, certain smartwatches or video-games; or therapies with animals, among many others, have all demonstrated their suitability for such a purpose.This research was funded by the Spanish Ministry of Science and Innovation, State Plan 2017–2020: Challenges—R&D&I Projects with grant codes PID2019-104323RB-C32 and PID2019-104323RB-C33

Air temperature measurements using autonomous self-recording dataloggers in mountainous and snow covered areas

High mountain areas are poorly represented by official weather observatories. It implies that new instruments must be evaluated over snow-covered and strongly insolated environments (i.e. mid-latitude mountain areas). We analyzed uncertainty sources over snow covered areas including: 1) temperature logger accuracy and bias of two widely used temperature sensors (Tinytag and iButton); 2) radiation shield performance under various radiation, snow, and wind conditions; 3) appropriate measurement height over snow covered ground; and 4) differences in air temperature measured among nearby devices over a horizontal band. The major results showed the following. 1) Tinytag performance device (mean absolute error: MAE≈ 0.1–0.2°C in relation to the reference thermistor) was superior to the iButton (MAE≈ 0.7°C), which was subject to operating errors. 2) Multi-plate radiation shield showed the best performance under all conditions (> 90% samples has bias between ±0.5°C). The tube shield required wind (> 2.5ms⁠−1) for adequate performance, while the funnel shield required limited radiation (< 400Wm⁠−2). Snow cover causes certain overheating. 3) Air temperatures were found to stabilize at 75–100cm above the snow surface. Air temperature profile was more constant at night, showing a considerable cooling on near surface at midday. 4) Horizontal air temperature differences were larger at midday (0.5°C). These findings indicate that to minimize errors air temperature measurements over snow surfaces should be carried out using multi-plate radiation shields with high-end thermistors such as Tinytags, and be made at a minimum height above the snow covered ground.This study was funded by the research projects “El papel de la nieve en la hidrología de la peninsula ibérica y su respuesta a procesos de cambio global-HIDROIBERNIEVE-CGL2017-82216-R” and CLIMPY “Characterization of the evolution of climate and provision of information for adaptation in the Pyrenees” (FEDER-POCTEFA)