Estudio de las capas de acoplamiento y alternativas al reflector de Bragg en estructuras BAW-CRF

Las capas de acoplamiento son un elemento clave en los dispositivos BAW CRF. El factor de acoplamiento K de estas capas permite el diseño de una determinada respuesta. Debido al limitado número de materiales con las que implementarlas, las soluciones que utilizan capas de λ/4 ofrecen un rango discreto de K. Por otra parte, el reflector de Bragg es un mecanismo de aislamiento mecánico entre el sustrato y la estructura BAW que está formado por capas alternas de alta y baja impedancia acústica de λ/4. El problema que presenta es la reducción del factor de calidad asociado a las pérdidas producida por las ondas shear. Este proyecto presenta un método para la obtención de un rango continuo de factores de acoplamiento y estudia la mejora del factor de calidad de las estructuras BAW con reflector de Bragg partiendo de dos materiales con alta y baja impedancia acústica.

Anàlisi i disseny d'un reflector per banda W

Les ones passives mil·limètriques (30 a 300GHz) tenen la peculiaritat de propagar-se en medis com la boira o la roba, a diferència del rang visible o l’infraroig. D’aquesta peculiaritat, surt l’interès de reproduir imatges per diverses aplicacions (seguretat, vigilància, etc...). És per aquest motiu que es treballa en el disseny d’un reflector per aquest tipus d’aplicació, treballant a una de les finestres de propagació d’aquest rang, la de la banda W. Es dissenyen i analitzen tres tipus de reflector: parabòlic simètric, offset i Cassegrain. D’aquests, s’estudien les seves figures de mèrit i directivitats buscant que aquestes siguin el més elevades possibles per obtenir una bona resolució, així com l’escaneig de l’escena de la qual es vol obtenir una imatge, veient aquí els efectes de les aberracions més comunes.

Chain conditions for Leavitt path algebras

In this paper, results known about the artinian and noetherian conditions for the Leavitt path algebras of graphs with finitely many vertices are extended to all row-finite graphs. In our first main result, necessary and sufficient conditions on a row-finite graph E are given so that the corresponding (not necessarily unital) Leavitt path K-algebra L(E) is semisimple. These are precisely the algebras L(E)for which every corner is left (equivalently, right)artinian. They are also precisely the algebras L(E) for which every finitely generated left (equivalently, right) L(E)-module is artinian. In our second main result, we give necessary and sufficient conditions for every corner of L(E) to be left (equivalently, right) noetherian. They also turn out to be precisely those algebras L(E) for which every finitely generated left(equivalently, right) L(E)-module is noetherian. In both situations, isomorphisms between these algebras and appropriate direct sums of matrix rings over K or K[x, x−1] are provided. Likewise, in both situations, equivalent graph theoretic conditions on E are presented.

Emissions distribution in post-Kyoto international negotiations: a policy

An abundant scientific literature about climate change economics points out that the future participation of developing countries in international environmental policies will depend on their amount of pay offs inside and outside specific agreements. These studies are aimed at analyzing coalitions stability typically through a game theoretical approach. Though these contributions represent a corner stone in the research field investigating future plausible international coalitions and the reasons behind the difficulties incurred over time to implement emissions stabilizing actions, they cannot disentangle satisfactorily the role that equality play in inducing poor regions to tackle global warming. If we focus on the Stern Review findings stressing that climate change will generate heavy damages and policy actions will be costly in a finite time horizon, we understand why there is a great incentive to free ride in order to exploit benefits from emissions reduction efforts of others. The reluctance of poor countries in joining international agreements is mainly supported by historical responsibility of rich regions in generating atmospheric carbon concentration, whereas rich countries claim that emissions stabilizing policies will be effective only when developing countries will join them.Scholars recently outline that a perceived fairness in the distribution of emissions would facilitate a wide spread participation in international agreements. In this paper we overview the literature about distributional aspects of emissions by focusing on those contributions investigating past trends of emissions distribution through empirical data and future trajectories through simulations obtained by integrated assessment models. We will explain methodologies used to elaborate data and the link between real data and those coming from simulations. Results from this strand of research will be interpreted in order to discuss future negotiations for post Kyoto agreements that will be the focus of the next. Conference of the Parties in Copenhagen at the end of 2009. A particular attention will be devoted to the role that technological change will play in affecting the distribution of emissions over time and to how spillovers and experience diffusion could influence equality issues and future outcomes of policy negotiations.

Eina per al desenvolupament de reflectors de conjunts òptics

Avui en dia, una bona il·luminació vial és molt important, tant per als conductors com per als vianants. Els fanals o conjunts òptics estan compostos per una font de llum que és la làmpada, el reflector i la carcassa que els protegeix. Trobar la forma exacta d’un reflector amb unes propietats òptiques en particular és de gran importància en el sector luminotècnic. En aquest projecte es vol dissenyar i desenvolupar una sistema capaç d’ajudar a obtenir el reflector adequat, un programari que permeti dissenyar un reflector a partir d’una boca qualsevol, i mitjançant una làmpada, capturar la intensitat de llum que el reflector projecta sobre al terra o una superfície del carrer. L’aplicació desenvolupada vol facilitar el procés de selecció d’un bon reflector als enginyers luminotècnics

Testing the response of macroinvertebrate functional structure and biodiversity to flooding and confinement

The aim of the present study was to investigate the relative importance of flooding- and confinement-related environmentalfeatures in explaining macroinvertebrate trait structure and diversity in a pool of wetlands located in a Mediterranean riverfloodplain. To test hypothesized trait-environment relationships, we employed a recently implemented statistical procedure, thefourth-corner method. We found that flooding-related variables, mainly pH and turbidity, were related to traits that confer an abilityof the organism to resist flooding (e.g., small body-shape, protection of eggs) or recuperate faster after flooding (e.g., short life-span, asexual reproduction). In contrast, confinement-related variables, mainly temperature and organic matter, enhanced traits that allow organisms to interact and compete with other organisms (e.g., large size, sexual reproduction) and to efficiently use habitat and resources (e.g., diverse locomotion and feeding strategies). These results are in agreement with predictions made under the River Habitat Templet for lotic ecosystems, and demonstrate the ability of the fourth-corner method to test hypothesis that posit traitenvironment relationships. Trait diversity was slightly higher in flooded than in confined sites, whereas trait richness was not significantly different. This suggests that although trait structure may change in response to the main environmental factors, as evidenced by the fourth-corner method, the number of life-history strategies needed to persist in the face of such constraints remains more or less constant; only their relative dominance differs

A note on the coincidence between Stackelberg and Nash equilibria in a differential game between government and firms

[cat] A Navas i Marín Solano es va demostrar la coincidència entre els equilibris de Nash i de Stackelberg per a una versi´o modificada del joc diferencial proposat por Lancaster (1973). Amb l’objectiu d’obtenir una solució interior, es van imposar restriccions importants sobre el valors dels paràmetres del model. En aquest treball estenem aquest resultat, en el límit en que la taxa de descompte és igual a zero, eliminant les restriccions i considerant totes les solucions possibles.

Slow Dynamics of Ising Models with Energy Barriers

Using Monte Carlo simulations we study the dynamics of three-dimensional Ising models with nearest-, next-nearest-, and four-spin (plaquette) interactions. During coarsening, such models develop growing energy barriers, which leads to very slow dynamics at low temperature. As already reported, the model with only the plaquette interaction exhibits some of the features characteristic of ordinary glasses: strong metastability of the supercooled liquid, a weak increase of the characteristic length under cooling, stretched-exponential relaxation, and aging. The addition of two-spin interactions, in general, destroys such behavior: the liquid phase loses metastability and the slow-dynamics regime terminates well below the melting transition, which is presumably related with a certain corner-rounding transition. However, for a particular choice of interaction constants, when the ground state is strongly degenerate, our simulations suggest that the slow-dynamics regime extends up to the melting transition. The analysis of these models leads us to the conjecture that in the four-spin Ising model domain walls lose their tension at the glassy transition and that they are basically tensionless in the glassy phase.

A note on the coincidence between Stackelberg and Nash equilibria in a differential game between government and firms

[cat] A Navas i Marín Solano es va demostrar la coincidència entre els equilibris de Nash i de Stackelberg per a una versi´o modificada del joc diferencial proposat por Lancaster (1973). Amb l’objectiu d’obtenir una solució interior, es van imposar restriccions importants sobre el valors dels paràmetres del model. En aquest treball estenem aquest resultat, en el límit en que la taxa de descompte és igual a zero, eliminant les restriccions i considerant totes les solucions possibles.

New magnetotelluric data trough the boundary between the Ossa Morena and Centroiberian Zones

The south-western part of the Iberian Peninsula, including the southern branch of the Iberian Massif, has recently been the subject of several magnetotelluric (MT) studies. This area is made up of three different tectonic terranes: the South Portuguese Zone (SPZ), the Ossa Morena Zone (OMZ) and the Central Iberian Zone (CIZ). The boundaries between these zones are considered to be sutures, which appear as high electrical conductivity anomalies in the MT surveys. The OMZ is characterised by a conductive layer at middle-lower crustal levels. To investigate the continuity of this conductive layer into the CIZ, a new MT profile was carried out. This 75-km long ENE profile goes through the boundary between the OMZ and the CIZ. The results of a two-dimensional magnetotelluric inversion revealed a high-conductivity anomaly in the transition OMZ/CIZ (the so-called Central Unit), which is interpreted as due to interconnected graphite along shear planes. High-conductivity anomalies appeared in the middle crust of the CIZ, whose geometry and location are consistent with the conductive layer previously found in the OMZ, thus confirming the prolongation of the conductive layer into the CIZ. The top of this layer correlated spatially with a broad reflector detected by a seismic profile previously acquired in the same area. This, together with other geological and petrological evidence, points to a common origin for both features.

Efectivitat dels diferents tipus de colpeig a pilota aturada en el futbol platja

El propòsit d’aquest estudi és analitzar quin és l’índex d’efectivitat en diferents situacions a pilota aturada (penals, faltes sense barrera i córners) en el futbol platja dins el context d’equips amateurs que participen en els tornejos de Blanes i Tossa de Mar. A l’hora de realitzar-lo he tingut en compte una sèrie de variables, com ara la precisió del colpeig, el tipus de colpeig, la superfície de contacte o la situació inicial de la pilota, és a dir, des d’on provenia la trajectòria inicial d’ aquesta, tot comprovant també com canvien els resultats en funció de la zona i del costat que es realitza el remat. Respecte els resultats, aquests demostren que l’índex d’efectivitat en aquest tipus d’accions és més baix en relació amb altres esports semblants com el futbol i el futbol sala.

La importància de les accions a pilota aturada en el futbol professional

L’objectiu del present estudi va consistir en estudiar el percentatge de gols a pilota aturada de la Lliga BBVA i la Premier League, establint el percentatge d’efectivitat de cadascuna d’elles. A més, es volia analitzar la freqüència de les diferents tipus d’accions a pilota aturada i substituir el terme estratègia per accions a pilota aturada. Amb aquest objectiu es van analitzar 80 partits disputats per equips de futbol professional en la temporada 2012-13 de la Lliga BBVA i la Premier League mitjançant l’anàlisi de vídeos. Les variable dependent era la consecució o no del gol, tenint com a variables independents 4 tipus d’accions a pilota aturada: tirs lliures directes, tirs lliures indirectes, córners i penals. Els resultats indiquen un major número de gols provinents d’accions a pilota aturada en la Lliga BBVA que en la Premier League, 29,8% per un 23,4% respectivament. Tot i això, s’ha comprovat com els percentatges d’efectivitat són pràcticament idèntics: 4,54% a la Lliga BBVA i 4,58% a la Premier League. Finalment, s’ha identificat el córner com l’acció que més es produeix en el joc, seguit de les faltes directes, els penals i les faltes indirectes.

Les lletres de confegir: l’atenció a la diversitat en el procés d’aprenentatge de la lectoescriptura

L’aprenentatge de la lectoescriptura és complex. Aprendre a llegir i escriure implica dominar moltes habilitats. A l’escola habitualment es treballa de forma mecànica i poc significativa. L’objectiu d’aquest projecte és conèixer si les lletres de confegir de Maria Montessori encara tenen vigència en l’actualitat. En aquest sentit, s’ha valorat el racó on hi ha aquest material, ja existent a l’escola, per posteriorment fer una proposta de millora i desenvolupar-la dins el marc d’una aula de P5. A través d’algunes situacions reals d’aula volem il·lustrar les possibilitats de la nostra proposta. L’experiència realitzada amb infants de l’últim curs d’Educació Infantil indica que treballar el procés de lectoescriptura amb aquest material és una bona eina per atendre a la diversitat existent a les aules actuals.

Análisis de la eficacia de los saques de esquina en la copa del mundo de fútbol 2010. Un intento de identificación de variables explicativas

In soccer, dead-ball moves are those in which the ball is returned to play from a stationary position following an interruption of play. The aim of this study was to analyse the effectiveness of one such dead-ball move, namely corner kicks, and to identify the key variables that determine the success of a shot or header following a corner, thereby enabling a model of successful corner kicks to be proposed. We recorded 554 corner kicks performed during the 2010 World Cup in South Africa and carried out a univariate, bivariate and multivariate analysis of the data. The results indicated that corners were of limited effectiveness in terms of the success of subsequent shots or headers. The analysis also revealed a series of variables that were significantly related to one another, and this enabled us to propose an explanatory model. Although this model had limited explanatory power, it nonetheless helps to understand the execution of corner kicks in practical terms.

Spectral analysis of the angular distribution function of back reflectors for thin film silicon solar cells

Nowadays, one of the most important challenges to enhance the efficiency of thin film silicon solar cells is to increase the short circuit intensity by means of optical confinement methods, such as textured back-reflector structures. In this work, two possible textured structures to be used as back reflectors for n-i-p solar cells have been optically analyzed and compared to a smooth one by using a system which is able to measure the angular distribution function (ADF) of the scattered light in a wide spectral range (350-1000 nm). The accurate analysis of the ADF data corresponding to the reflector structures and to the μc-Si:H films deposited onto them allows the optical losses due to the reflector absorption and its effectiveness in increasing light absorption in the μc-Si:H layer, mainly at long wavelengths, to be quantified.