699 research outputs found
Admissibility condition for exceptional Laguerre polynomials
We prove a necessary and sufficient condition for the integrability of the
weight associated to the exceptional Laguerre polynomials. This condition is
very much related to the fact that the associated second order differential
operator has no singularities in .Comment: 12 page
Assessment of a Universal Reconfiguration-less Control Approach in Open-Phase Fault Operation for Multiphase Drives
Multiphase drives have been important in particular industry applications where reliability is
a desired goal. The main reason for this is their inherent fault tolerance. Di erent nonlinear controllers
that do not include modulation stages, like direct torque control (DTC) or model-based predictive
control (MPC), have been used in recent times to govern these complex systems, including mandatory
control reconfiguration to guarantee the fault tolerance characteristic. A new reconfiguration-less
approach based on virtual voltage vectors (VVs) was recently proposed for MPC, providing a natural
healthy and faulty closed-loop regulation of a particular asymmetrical six-phase drive. This work
validates the interest in the reconfiguration-less approach for direct controllers and multiphase drives
Integración de cuentos y TIC en unidades didácticas para el aprendizaje del inglés a través de contenidos.
The aim of this article is to show how it is possible to integrate stories and ICT in Content Language Integrated Learning (CLIL) for English as a foreign language (EFL) learning in bilingual schools. Two Units of Work are presented. One, for the second year of Primary, is based on a Science topic, ‘Materials’. The story used is ‘The three little pigs’ and the computer program ‘JClic’. The other one is based on a Science and Arts topic for the sixth year of Primary, the story used is ‘Charlotte’s Web’ and the computer program ‘Atenex’.El propósito de este artículo es mostrar cómo se puede alcanzar la integración de cuentos y TIC en el Aprendizaje Integrado de Conocimientos Curriculares y Lengua Extranjera (AICLE) para el aprendizaje del inglés como lengua extranjera (ILE) en colegios bilingües. Se presentan dos Unidades: Una basada en un tema de Conocimiento del Medio Natural: “Materiales”, para 2º Curso de Primaria, a partir del cuento: “Los tres cerditos”, y el programa informático “JClic” y otra Unidad basada en un tema de Ciencias y Arte para 6º Curso de Primaria, a partir del cuento: “Charlotte’s Web”, y el programa informático: “Atenex”
Theory of homogeneous vapour condensation and surface deposition from boundary layers
Homogeneous condensation of vapours mixed with a carrier gas in the stagnation point boundary layer flow near a cold wall is considered. There is a condensation region near the wall with supersaturated vapour. Assuming that the surface tension times the molecular area is much larger than the thermal energy far from the wall, droplets are nucleated exclusively in a narrow nucleation layer where the Zeldovich flux of clusters surpassing the critical nucleus size is at a maximum. The vapour condenses in the free molecular regime on the droplets, which are thermophoretically attracted to the wall. Unlike the narrow condensation region for heterogeneous condensation on solid particles, in the case of homogeneous condensation the condensation region is wide even when the rate of vapour scavenging by droplets is large. A singular perturbation theory of homogeneous vapour condensation in boundary layer flow approximates very well the vapour and droplet density profiles, the nucleation layer and the deposition rates at the wall for wide ranges of the wall temperature and the scavenging parameter B. A key point in the theory is to select a trial vapour number density profile among a one parameter family of profiles between an upper and a lower bound. The maximum of the Zeldovich flux for supercritical nuclei provides the approximate location of the nucleation layer and an approximate droplet density profile. Then the condensate number of molecules and the vapour density profile are calculated by matched asymptotic expansions that also yield the deposition rates. For sufficiently large wall temperatures, a more precise corrected asymptotic theory is given.This work was supported by the Spanish Ministerio de Economía y Competitividad grant FIS2011-28838-C02-01 and by the Autonomous Region of Madrid grant P2009/ENE-1597 (HYSYCOMB).Publicad
Resultados numéricos en un modelo de lavado de una resina macroporosa
En este artículo se proponen dos métodos numéricos para resolver un sistema de ecuaciones en derivadas parciales formado por una ecuación del tipo parabólica, y otra hiperbólica. Estos métodos están basados en dos aproximaciones teóricas de la solución de la ecuación parabólica del sistema, y en un uso adecuado de un esquema de diferencias finitas para aproximar la solución de la ecuación hiperbólica. El sistema de ecuaciones en estudio tiene su origen en un
problema real proveniente de la físico-química, que se explica en detalle en el artículo. En este problema concreto, ambos métodos fueron implementados computacionalmente, presentándose aquí los resultados numéricos obtenidos.Peer Reviewe
Field Oriented Control of Multiphase Drives with Passive Fault-Tolerance
Multiphase machines provide continuous
operation of the drive with no additional hardware in the
event of one or more open-phase faults. This faulttolerant
capability is highly appreciated by industry for
security and economic reasons. However, the steadystate
post-fault operation has only been feasible in
previous works after the fault localization and control
reconfiguration. Even though this is done at the software
stage, the obligation to identify the faulty phases and
store the modifications for every fault scenario adds
further complexity. This work reveals that this software
reconfiguration can be avoided if the field-oriented
control (FOC) strategy is designed to satisfactorily
handle pre- and post-fault situations. Experimental
results confirm the capability to obtain suitable postfault
operation without fault localization and control
reconfiguration, thus achieving a passive/natural fault
tolerance.Ministerio de Ciencia, Innovación y Universidades RTI2018-096151-B-I0
Open-Phase Fault Operation on Multiphase Induction Motor Drives
Multiphase machines have been recognized in the last few years like an attractive alternative to conventional three-phase ones. This is due to their usefulness in a niche of applications where the reduction in the total power per phase and, mainly, the high overall system reliability and the ability of using the multiphase machine in faulty conditions are required. Electric vehicle and railway traction, all-electric ships, more-electric aircraft or wind power generation systems are examples of up-to-date real applications using multiphase machines, most of them taking advantage of the ability of continuing the operation in faulty conditions. Between the available multiphase machines, symmetrical five-phase induction machines are probably one of the most frequently considered multiphase machines in recent research. However, other multiphase machines have also been used in the last few years due to the development of more powerful microprocessors. This chapter analyzes the behavior of generic n-phase machines (being n any odd number higher than 3) in faulty operation (considering the most common faulty operation, i.e. the open-phase fault). The obtained results will be then particularized to the 5-phase case, where some simulation and experimental results will be presented to show the behavior of the entire system in healthy and faulty conditions. The chapter will be organized as follows: First, the different faults in a multiphase machine are analyzed. Fault conditions are detailed and explained, and the interest of a multiphase machine in the management of faults is stated. The effect of the open-phase fault operation in the machine model is then studied. A generic n-phase machine is considered, being n any odd number greater than three. The analysis is afterwards particularized to the 5-phase machine, where the open-phase fault condition is managed using different control methods and the obtained results are compared. Finally, the conclusions are presented in the last section of the chapter
Impact of post-fault flux adaptation on six-phase induction motor drives with parallel converters
The redundancy of multiphase drives
provides an inherent fault-tolerant capability that is
appreciated in applications with a complicated
corrective maintenance or safety-critical requirements.
Fault restrictions however force the system to be
reconfigured to operate in a smooth and efficient
manner. Previous works have been focused on the
optimization of current waveforms to generate an
undisturbed operation but still maintaining the pre-fault
rated flux settings. This work shows that efficient
controllers can improve the post-fault performance in
six-phase induction machines supplied by parallel-
connected converters if offline optimization is used to
obtain a variable reference flux. Theoretical and
experimental results confirm that the proposed flux
adaptation method provides higher torque/power
capability, lower degree of imbalance in the current
sharing between windings and efficiency improvementMinisterio de Ciencia e Innovación ENE2014-52536-C2-1-R DPI2013- 44278-RJunta de Andalucía P11-TEP-755
Un poeta de retaguardia
Los llantos. Gonzalo Mallarino. Edición del autor, 1988, 68 págs
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