High Power Wideband Class-E Power Amplifier

This letter shows a high-power, high-efficiency, wideband Class-E RF power amplifier designed upon the load admittance synthesis concept and built using an uncomplicated low-loss load network with a low loss wideband admittance transformer as the main component. It uses a power Silicon LDMOS transistor to provide up to 145 W at 28 V peak power, up to 86% drain efficiency over 35% fractional bandwidth (from 85 to 120 MHz) and 15.6 dB gain at peak power without any adjustments. These are clear performance advantages over previous published works and commercially available amplifiers at a similar frequency band and power level. The amplifier applications include FM broadcast, aeronautical communications, nuclear, MRI, heating or RF power stage for Envelope Elimination and Restoration transmitters

Estudio de la utilización de etiquetas en aplicaciones para buscar y compartir información

En los últimos años, estamos asistiendo a un gran cambio en el modo en que Internet se relaciona con el mundo. Cada vez más popular, Internet ha dejado de limitarse a mostrar contenidos fijos para convertirse en un medio para la comunicación de los individuos. Una enorme cantidad de contenido web ha comenzado a ser generado a través de tecnologías sociales como weblogs, wikis o foros, tecnologías que permiten acceder a la comunicación y publicación de contenidos en web muy fácilmente, limitando cada vez más los conocimientos necesarios para su uso. Estos nuevos patrones en el modo en que la información se genera y multiplica hacen necesarios métodos de clasificación de información, capaces de manejar y organizar estas cantidades. Los métodos de clasificación tradicionales usados hasta ahora (p.e. sistemas jerárquicos) muestran limitaciones al enfrentarse a este conjunto creciente de contenidos, debido entre otros motivos a estar controlados por una autoridad central. Frente a ellos, un nuevo sistema de clasificación ha surgido al amparo precisamente de Internet, a raíz de su introducción en sitios web como del.icio.us o Flickr: las folksonomías. En ellas, es una comunidad de usuarios la encargada de aumentar los contenidos del sistema, añadiendo cada usuario recursos, y describiéndolos con una serie de etiquetas, esto es, palabras sueltas elegidas libremente, sin limitaciones de vocabularios controlados o de otro tipo. Este proyecto dará una panorámica pormenorizada sobre variados aspectos relacionados con esta nueva tecnología, y de entre ellos, se hará especial énfasis en el estudio de las ideas de mejora aplicadas hasta el momento; después de todo, las folksonomías son aún en este momento una idea en desarrollo, alimentada y por muy diversos estudios académicos y sistemas web reales. En este proyecto, hemos querido estudiar estas posibilidades de mejora, centrándonos en una: la recomendación automática de etiquetas. Se ha buscado comprobar hasta qué punto estos sistemas resultan de utilidad a los usuarios, si son utilizados, y qué provecho obtienen de ellos. Para ello, se ha desarrollado una aplicación web publicada para su libre uso, en que diversas herramientas de recomendación son ofrecidas a los usuarios, encargados de ejecutar diversas tareas relacionadas con el etiquetado y búsqueda de imágenes. Los datos de su interacción son recogidos y estudiados, obteniendo diversas conclusiones acerca de su comportamiento general en el manejo de estos sistemas con ayuda de herramientas de recomendación. ____________________________________In the last years, a great change has occurred in the way in which Internet is used. More and more popular, Internet has stopped limiting itself to show fixed contents, to truly become a mean for human communication. An enormous amount of Web content has begun being generated through social technologies like weblogs, wikis or forums, technologies that allow an easy communication and publication of contents in Web, limiting more and more the knowledge needed for its use. These new patrons in the way in which the information is generated make necessary new methods for the classification of information, able to handle and to organize these large amounts. The traditional methods of classification used until now (v.g. hierarchic systems) show limitations when facing this increasing set of contents, for the reason (among others) of being controlled by a central authority. In front of them, a new classification system has arisen, as a result of its introduction in Web sites like del.icio.us or Flickr: the folksonomies. In them, a community of users is in charge of increasing the contents of the system, each user adding resources, and describing them with a series of tags, a set of words chosen freely, without limitations of controlled vocabularies. This project will give a general view on varied aspects related to this new technology, and among them, special emphasis on the different ideas for folksonomy improvement applied until the moment; after all, the folksonomies are still a developing idea, fed by very diverse academic studies and real Web systems. In this project, we have tried to study these possibilities of improvement, focusing on one: the automatic recommendation of tags. We have tried to check to what extent these systems are useful to the users, whether they are used, and what benefit do they obtain from them. For this reason, it has been developed a web application, which is published for its public use, in which diverse tools of recommendation are offered to the users, who are asked to execute diverse tasks related to the labelling and search of images. The data of their interaction are picked up and studied, obtaining diverse conclusions about the general behavior of users in the interaction with these systems with the help of recommendation tools.Ingeniería en Informátic

Enfermedades mentales. El objetivismo biológico frente a una fenomenología de la salud mental

Universidad de Sevilla. Grado en Filosofí

El rescate de prisioneros y cautivos durante la Edad Media Hispánica. Aproximación a su estudio

A lo largo de la Historia fue desarrollándose el rescate de prisioneros, al que los juristas romanos y los pensadores cristianos dedicaron mucha atención. Este fenómeno de alcance europeo, sin embargo, presenta algunas características especiales para el ámbito hispánico, donde el derecho cristiano, mediante los fueros municipales, la legislación real y las Cortes y el derecho musulmán, trataron de la condición jurídica del prisionero - cautivo en poder de los enemigos y de su liberación mediante la práctica de rescates

Design of a Two-Phase buck converter with fourth-order output filter for envelope amplifiers of limited bandwidth

The use of techniques such as envelope tracking (ET) and envelope elimination and restoration (EER) can improve the efficiency of radio frequency power amplifiers (RFPA). In both cases, high-bandwidth DC/DC converters called envelope amplifiers (EA) are used to modulate the supply voltage of the RFPA. This paper addresses the analysis and design of a modified two-phase Buck converter optimized to operate as EA. The effects of multiphase operation on the tracking capabilities are analyzed. The use of a fourth-order output filter is proposed to increase the attenuation of the harmonics generated by the PWM operation, thus allowing a reduction of the ratio between the switching frequency and the converter bandwidth. The design of the output filter is addressed considering envelope tracking accuracy and distortion caused by the side bands arising from the nonlinear modulation process. Finally, the proposed analysis and design methods are supported by simulation results, as well as demonstrated by experiments obtained using two 100-W, 10-MHz, two-phase Buck EAs capable of accurately tracking a 1.5-MHz bandwidth OFDM signal

Aplicación de Juegos Serios en Moodle: Trivioodle

Los videojuegos son, sobre todo, muy populares entre las generaciones más jóvenes y ellos utilizan todas las tecnologías asociadas como algo que siempre ha formado parte de su vida. Diversas investigaciones indican que los juegos tienen efectos positivos sobre la concentración, toma de decisiones, habilidades de resolución de problemas, mejora del pensamiento lógico, creatividad y trabajo en equipo. El uso de juegos educativos en el desarrollo de las asignaturas es una práctica que proporciona beneficios muy positivos a las mismas. En este artículo se presentada la aplicación basada en juegos integrada en Moodle, Trivioodle, concurso de preguntas y respuestas, que comienza su uso para mejorar el proceso de aprendizaje en los grados de Ingeniería de Telecomunicación de la Universidad de Valladolid. El primer uso de esta aplicación en una asignatura ha sido muy positivo, provocando una activación temprana de contenidos y habilidades gracias a que el estudiante es capaz de jugar, probar, equivocarse y aprender

Ameva: An autonomous discretization algorithm

This paper describes a new discretization algorithm, called Ameva, which is designed to work with supervised learning algorithms. Ameva maximizes a contingency coefficient based on Chi-square statistics and generates a potentially minimal number of discrete intervals. Its most important advantage, in contrast with several existing discretization algorithms, is that it does not need the user to indicate the number of intervals. We have compared Ameva with one of the most relevant discretization algorithms, CAIM. Tests performed comparing these two algorithms show that discrete attributes generated by the Ameva algorithm always have the lowest number of intervals, and even if the number of classes is high, the same computational complexity is maintained. A comparison between the Ameva and the genetic algorithm approaches has been also realized and there are very small differences between these iterative and combinatorial approaches, except when considering the execution time.Ministerio de Educación y Ciencia TSI2006-13390-C02-02Junta de Andalucía P06-TIC-0214

An Adaptive Phase Alignment Algorithm for Cartesian Feedback Loops

An adaptive algorithm to correct phase misalignments in Cartesian feedback linearization loops for power amplifiers has been presented. It yields an error smaller than 0.035 rad between forward and feedback loop signals once convergence is reached. Because this algorithm enables a feedback system to process forward and feedback samples belonging to almost the same algorithm iteration, it is suitable to improve the performance not only of power amplifiers but also any other digital feedback system for communications systems and circuits such as all digital phase locked loops. Synchronizing forward and feedback paths of Cartesian feedback loops takes a small period of time after the system starts up. The phase alignment algorithm needs to converge before the feedback Cartesian loop can start its ideal behavior. However, once the steady state is reached, both paths can be considered synchronized, and the Cartesian feedback loop will only depend on the loop parameters (open-loop gain, loop bandwidth, etc.). It means that the linearization process will also depend only on these parameters since the misalignment effect disappears. Therefore, this algorithm relieves the power amplifier linearizer circuit design of any task required for solving phase misalignment effects inherent to Cartesian feedback systems. Furthermore, when a feedback Cartesian loop has to be designed, the designer can consider that forward and feedback paths are synchronized, since the phase alignment algorithm will do this task. This will reduce the simulation complexity. Then, all efforts are applied to determining the suitable loop parameters that will make the linearization process more efficient

Reconocimiento del locutor en telefonia: actividades del proyecto europeo COST 250

El objetivo de esta comunicación es presentar las actividades realizadas desde noviembre de 1994 dentro del proyecto “Speaker Recognition in Telephony”, financiado por la Comunidad Europea en el marco del programa “European Cooperation in the Field of Scientific and Technical Research” (COST), con referencia COST250. Los países participantes en el proyecto COST250 son Bélgica, Dinamarca, Eslovenia, España, Francia, Grecia, Inglaterra, Irlanda, Italia, Holanda, Portugal, Suecia, Suiza y Turquía.Peer ReviewedPostprint (published version

Bullfighting extreme scenarios in efficient hyper-scale cluster computing

Data centres are quickly evolving to support new demands for Cloud-Computing services. Extreme workload peaks represent a challenge for the maintenance of the performance and service level agreements, even more when operation costs need to be minimised. In this paper, we first present an extensive analysis of the impact of extreme workloads in large-scale realistic Cloud-Computing data centres, including a comparison between the most relevant centralised resource managing models. Moreover, we extend our previous works by proposing a new energy-efficiency policy called Bullfighter which is able to keep performance key performance indicators while reducing energy consumption in extreme scenarios. This policy employs queue-theory distributions to foresee workload demands and adapt automatically to workload fluc tuations even in extreme environments, while avoiding the fine-tuning required for other energy policies. Finally, it is shown through extensive simulation that Bullfighter can save more than 40% of energy in the aforementioned scenarios without exerting any noticeable impact on data-centre performance.Ministerio de Ciencia e Innovación RTI2018-098062-A-I0