Amplificador commutat per a senyals d’àudio controlat per un processador digital

L’objectiu d’aquest treball és el de dissenyar i construir un amplificador d’àudio que compleixi una sèrie de requisits. Les principals característiques que volem que tingui el nostre dispositiu son: que no consumeixi molta energia, que tingui una mida reduïda i que ens doni una bona resposta. A partir d’aquestes pautes hem decidit utilitzar un amplificador de classe D, ja que s’adapta prou bé a les nostres necessitats i podem trobar tecnologia en el mercat amb aquestes condicions. A partir del Datasheet del fabricant de l’integrat escollit hem iniciat el procés de disseny. Per al disseny del circuit, i per tant, per a poder fabricar la placa de circuit imprès, hem fet servir el programa de disseny de circuits OrCAD 10.5. Un cop hem tingut la placa hem soldat els components corresponents. L’últim pas ha sigut fer les proves pertinents per observar el funcionament de l’amplificador muntat. El projecte l’hem estructurat en sis apartats. Començarem amb una introducció del que es vol fer en aquest projecte. En el següent capítol veurem les característiques principals dels amplificadors de classe D donat que el nostre dispositiu utilitza aquesta tecnologia i no és gaire comú. El següent apartat serà per explicar el tipus de modulació que utilitza el nostre sistema ja que és una modulació diferent a les conegudes a la carrera. Seguirem fent una comparativa dels amplificadors de classe D respecte altres tipus d’amplificadors d’àudio que podem trobar al mercat, com poden ser els de classe A o AB. També, dedicarem un capítol a esmentar les principals característiques del TPA2000D2 que Continuarem amb la part més important del projecte on s’explicarà amb detall tot el procés de fabricació del dispositiu. Començarem explicant el procés previ al disseny, seguirem amb una explicació del disseny fins al muntatge de la placa, i finalment veurem el seu comportament. Per últim veurem les conclusions tretes al finalitzar el treball

LES POLÍTIQUES D’ADAPTACIÓ AL CANVI CLIMÀTIC A CATALUNYA

A les portes de què el Panell Intergovernamental del Canvi Climàtic (IPCC) comenci a publicar el setembre d'enguany els resultats del cinquè informe sobre el canvi climàtic, aquesta nota fa un repàs a les polítiques d'adaptació que s'han dut a terme tant a nivell internacional com, particularment, a Catalunya. La finalitat és fixar l'estat de la qüestió en quest àmbit

Spin-induced angular momentum switching

When light is transmitted through optically inhomogeneous and anisotropic media the spatial distribution of light can be modified according to its input polarization state. A complete analysis of this process, based on the paraxial approximation, is presented, and we show how it can be exploited to produce a spin-controlled-change in the orbital angular momentum of light beams propagating in patterned space-variant-optical-axis phase plates. We also unveil a new effect. The development of a strong modulation in the angular momentum change upon variation of the optical path through the phase plates.Comment: The original paper of the published version in Opt. Let

Manipulation of single-photon states encoded in transverse spatial modes: possible and impossible tasks

Controlled generation and manipulation of photon states encoded in their spatial degrees of freedom is a crucial ingredient in many quantum information tasks exploiting higher-than-two dimensional encoding. Here, we prove the impossibility to arbitrarily modify $d$-level state superpositions (qu$d$its) for $d>2$, encoded in the transverse modes of light, with optical components associated to the group of symplectic transforms (Gaussian operations). Surprisingly, we also provide an explicit construction of how non-Gaussian operations acting on mode subspaces do enable to overcome the limit $d=2$. In addition, this set of operations realizes the full SU(3) algebra.Comment: Published in PR

Spin and Orbital angular momentum propagation in anisotropic media: theory

This paper is devoted to study the propagation of light beams carrying orbital angular momentum in optically anisotropic media. We first review some properties of homogeneous anisotropic media, and describe how the paraxial formalism is modified in order to proceed with a new approach dealing with a general setting of paraxial propagation along uniaxial inhomogeneous media. This approach is suitable for describing the space-variant-optical-axis phase plates

Hypoxic Cell Waves around Necrotic Cores in Glioblastoma: A Biomathematical Model and its Therapeutic Implications

Glioblastoma is a rapidly evolving high-grade astrocytoma that is distinguished pathologically from lower grade gliomas by the presence of necrosis and microvascular hiperplasia. Necrotic areas are typically surrounded by hypercellular regions known as "pseudopalisades" originated by local tumor vessel occlusions that induce collective cellular migration events. This leads to the formation of waves of tumor cells actively migrating away from central hypoxia. We present a mathematical model that incorporates the interplay among two tumor cell phenotypes, a necrotic core and the oxygen distribution. Our simulations reveal the formation of a traveling wave of tumor cells that reproduces the observed histologic patterns of pseudopalisades. Additional simulations of the model equations show that preventing the collapse of tumor microvessels leads to slower glioma invasion, a fact that might be exploited for therapeutic purposes.Comment: 29 pages, 9 figure

Molding with nanoparticle-based one-dimensional photonic crystals: A route to flexible and transferable Bragg mirrors of high dielectric contrast

Self-standing, flexible Bragg mirror films of high refractive index contrast and showing intense and wide Bragg peaks are herein presented. Nanoparticle-based one-dimensional photonic crystals are used as templates to infiltrate a polymer, which provides the multilayer with mechanical stability while preserving the dielectric contrast existing in the mold. Such films can be lifted off the substrate and used to coat another surface of arbitrary shapeMinisterio de Ciencia y Educación MAT2008-02166Junta de Andalucía FQM-357

Localized surface plasmon effects on the photophysics of perovskite thin films embedding metal nanoparticles

Herein we provide direct experimental evidence that proves that the photophysical properties of thin methylammonium lead iodide perovskite films are significantly enhanced by localized surface plasmon resonances (SPRs). Observations are well supported by rigorous calculations that prove that improved light harvesting can be unequivocally attributed to plasmonic scattering and near field reinforcement effects around silver nanoparticles embedded within the semiconductor layer. Adequate design of the localized SPR allows raising the absorptance of a 300 nm thick film at well-defined spectral regions while minimizing the parasitic absorption from the metallic inclusions. Measured enhancements can be as large as 80% at specific wavelengths and 20% when integrated over the whole range at which SPR occurs, in agreement with theoretical estimations. Simultaneously, the characteristic quenching effect that the vicinity of metals has on the photoluminescence of semiconductors is largely compensated for by the combined effect of the enhanced photoexcitation and the higher local density of photon states occurring at SPR frequencies, with a two fold increase of the perovskite photoemission efficiency being measuredThe research leading to these results has received funding from the Spanish Ministry of Economy and Competitiveness under grant MAT2017-88584-R (AEI/FEDER,UE). A. B. was supported by the U. S. Department of State through the Fulbright Program. S. C. P. is grateful for the support of the AEI under the Juan de la Cierva Incorporación programme (IJCI-2016-28549

A Bayesian hidden Markov model for assessing the hot hand phenomenon in basketball shooting performance

Sports data analytics is a relevant topic in applied statistics that has been growing in importance in recent years. In basketball, a player or team has a hot hand when their performance during a match is better than expected or they are on a streak of making consecutive shots. This phenomenon has generated a great deal of controversy with detractors claiming its non-existence while other authors indicate its evidence. In this work, we present a Bayesian longitudinal hidden Markov model that analyses the hot hand phenomenon in consecutive basketball shots, each of which can be either missed or made. Two possible states (cold or hot) are assumed in the hidden Markov chains of events, and the probability of success for each throw is modelled by considering both the corresponding hidden state and the distance to the basket. This model is applied to a real data set, the Miami Heat team in the season 2005-2006 of the USA National Basketball Association. We show that this model is a powerful tool for assessing the overall performance of a team during a match or a season, and, in particular, for quantifying the magnitude of the team streaks in probabilistic terms