Delay effects on the limit cycling behavior in an H-bridge resonant inverter with zero current switching control strategy

Celebrado en Tarragona del 2-6 de septiembre de 2018.In this paper, bifurcations of limit cycles in a H-bridge LC resonant inverter under a zero current switching control strategy with delay in the switching action are analyzed. Mathematical analysis and numerical simulations show that the delay can degrade the quality of the oscillations and even inhibit them.Agencia Estatal de Investigación DPI2017- 84572-C2-1-RFondo Europeo de Desarrollo Regional DPI2017- 84572-C2-1-RMinisterio de Ciencia e Innovación MTM2015-65608-PJunta de Andalucía Consejería de Economía y Conocimiento P12-FQM-165

Una "piedra del rayo" recuperada en el "oppidum" de Monte Bernorio (Villarén, Palencia): sobre la "ceraunia" en la Cantabria prerromana

En las diferentes intervenciones arqueológicas llevadas a cabo en Monte Bernorio se han recuperado dos hachas y una azuela pulidas. El estudio de conjunto y el contexto del hallazgo permiten identificar una de las hachas como ceraunia, más comúnmente conocidas como piedras del rayo. Y es que la necesidad de protegerse contra la caída del rayo mediante filacterias está muy extendida en la antigüedad, y como podemos ver, también se encuentra presente en la Cantabria prerromana.In different archaeological interventions on Monte Bernorio there have been discovered two axes and a polished adz. According to a global analysis of the discovery and its context, one of the axes may be identified as ceraunia, commonly known as thunderbolts. The need for protection against lightning by phylacteries was widespread in the Antiquity and, as we can see, it was also present in the Pre-Roman Cantabria

A neural blockchain for a tokenizable e-Participation model

Currently, Distributed Ledger Technologies (DLTs) and, especially, Blockchain technology represent a great opportunity for public institutions to improve citizen participation and foster democratic innovation. These technologies facilitate the simplification of processes and provide secure management of recorded data, guaranteeing the transmission and public transparency of information. Based on the combination of a Blockchain as a Service (BaaS) platform and G-Cloud solutions, our proposal consists of the design of an e-Participation model that uses a tokenizable system of the actions and processes undertaken by citizens in participatory processes providing incentives to promote greater participation in public affairs. In order to develop a sustainable, scalable and resilient e-Participation system, a new blockchain concept, which organizes the blocks as a neural system, is combined with the implementation of a virtual token to reward participants. Furthermore, this virtual token is deployed through a smart contract that the block itself produces, containing information about the transaction and all the documents involved in the process. Finally, our Neural Distributed Ledger (NDL) framework facilitates the interconnection of blockchain networks in a transparent, certified, secure, auditable, scalable and traceable way

Non-uniform sinusoidally modulated half-mode leaky-wave lines for near-field focusing pattern synthesis

A novel non-uniform sinusoidally modulated half-mode microstrip structure with application to near-field focused leaky-wave radiation in the backward Fresnel zone is proposed. First, it is presented a dispersion analysis of the constituent backward leaky wave in the sinusoidally modulated unit cell in half-width microstrip technology. This information is then used to design a finite non-uniform line that focuses the radiated fields at the desired point. Finally, eight similar line sources are arranged in a radial array to generate a three-dimensional focused spot located at the desired focal length over the simple central coaxial feeding. Simulated and experimental results are presented to validate the proposed simple approach.Ministerio de Educación y Ciencia TEC2013-47037-C5-5-R, TEC2010-21520-C04-04, TEC2013-41913-PFundación Séneca 08833/PI/0

Suppression of undesired attractors in a self-oscillating H-bridge parallel resonant converters under zero current switching control

Resonant converters under zero current switching control strategy can exhibit coexistence of attractors, making it difficult the startup of the system from zero initial conditions. In this paper, the problem of multiple coexisting attractors in parallel resonant converters is addressed. Appropriate modifications of the switching decision with the aim of converting undesired attractors into virtual ones are proposed. A suitable control signal is generated from the state variables of the system and used to adjust the switching decision. Numerical simulations corroborate the proposed solutions and the simplest one was finally verified by measurements from a laboratory prototype.Postprint (author's final draft

Nonlinear dynamic modeling and analysis of self-oscillating H-bridge parallel resonant converter under zero current switching control: unveiling coexistence of attractors

This paper deals with the global dynamical analysis of an H-bridge parallel resonant converter under a zero current switching control. Due to the discontinuity of the vector field in this system, sliding dynamics may take place. Here, the sliding set is found to be an escaping region. Different tools are combined for studying the stability of oscillations of the system. The desired crossing limit cycles are computed by solving their initial value problem and their stability analysis is performed using Floquet theory. The resulting monodromy matrix reveals that these cycles are created according to a smooth cyclic-fold bifurcation. Under parameter variation, an unstable symmetric crossing limit cycle undergoes a crossing-sliding bifurcation leading to the creation of a symmetric unstable sliding limit cycle. Finally, this limit cycle undergoes a double homoclinic connection giving rise to two different unstable asymmetric sliding limit cycles. The analysis is performed using a piecewise-smooth dynamical model of a Filippov type. Sliding limit cycles divide the state plane in three basins of attraction, and hence, different steady-state solutions may coexist which may lead the system to start-up problems. Numerical simulations corroborate the theoretical predictions, which have been experimentally validated.Postprint (author's final draft

Delay effects on the limit cycling behavior in an H-bridge resonant inverter with zero current switching control strategy

In this paper, bifurcations of limit cycles in a H-bridge LC resonant inverter under a zero current switching control strategy with delay in the switching action are analyzed. Mathematical analysis and numerical simulations show that the delay can degrade the quality of the oscillations and even inhibit them.Postprint (author's final draft

Influence of temperature on the biaxial strength of cemented carbides with different microstructures

The effect of the temperature on the mechanical strength of WC-Co cemented carbides with different microstructures (grain size and binder content) was evaluated. Biaxial flexural tests were performed on three cemented carbide grades at 600 °C using the ball-on-three-balls (B3B) method. Results were interpreted by Weibull statistics and compared to biaxial strength results at room temperature. A detailed fractographic analysis, supported by Linear Elastic Fracture Mechanics, was performed to differentiate the nature and size of critical defects and the mechanism responsible for the fracture. A significant decrease in the mechanical strength (around 30%) was observed at 600 °C for all grades of cemented carbides. This fact was ascribed to the change in the critical flaw population from sub-surface (at room temperature) to surface defects, associated with the selective oxidation of Co. Additionally, an estimation of the fracture toughness at 600 °C was attempted for the three cemented carbides, based upon the B3B strength results, the corresponding number of the tested specimens fragments and the macroscopic area of the B3B fracture surfaces. The fracture toughness was not affected by the temperature, at least up to 600 °C. In addition, the good agreement with the Single Edge Notch Beam toughness data suggests the possibility of employing this approach for fracture toughness evaluation of brittle materials under different testing conditions.Peer ReviewedPostprin

Análisis de la adaptación de administración y dirección a la enseñanza en lengua inglesa desde el punto de vista del alumno

Ante los retos que supone la enseñanza en una lengua extranjera y el necesario proceso de adaptación al Espacio Europeo de Educación Superior, la metodología docente de la asignatura Administración y Dirección en idioma inglés ha nacido adaptada desde el primer momento a este nuevo marco normativo a nivel europeo. Para comprobar la aceptación de la metodología por parte del alumnado y llevar a cabo las medidas correctivas pertinentes previas a la extensión futura de este sistema u otro similar a la enseñanza en español de la asignatura, se ha analizado la opinión al respecto de los alumnos mediante un cuestionario cuyos resultados se comentan en el presente trabajo

Dispositivo de plataforma móvil para la medición automática de parámetros climáticos en diferentes puntos del interior de un invernadero

Número de publicación:ES2683920 A2 (28.09.2018) También publicado como: ES2683920 R1 (08.10.2018) ES2683920 B1 (16.07.2019) Número de Solicitud: Consulta de Expedientes OEPM (C.E.O.) P201700552 (28.03.2017)Dispositivo móvil que se desplaza bajo invernadero a lo largo de un raíl fijo y que contiene una plataforma auto-nivelable diseñada para la colocación de sensores de medida de parámetros climáticos en una plataforma autoportante que se desplaza de forma controlada por el interior de un invernadero gracias a un raíl sobre el que se desplaza mediante un sistema piñón-cremallera. Para obtener dicho movimiento el elemento móvil de la plataforma autoportante, incorpora un motor eléctrico. A este elemento móvil se acopla un husillo vertical que permite colocar una bandeja a la altura deseada y que se nivela automáticamente mediante la actuación de dos servomotores con realimentación por acelerómetros y giróscopo. El elemento fijo o rail está formado por un perfil de sección cuadrada al que se suelda una cremallera.Universidad de Almerí