Singular and Plural Functions for Functional Logic Programming

Functional logic programming (FLP) languages use non-terminating and non-confluent constructor systems (CS's) as programs in order to define non-strict non-determi-nistic functions. Two semantic alternatives have been usually considered for parameter passing with this kind of functions: call-time choice and run-time choice. While the former is the standard choice of modern FLP languages, the latter lacks some properties---mainly compositionality---that have prevented its use in practical FLP systems. Traditionally it has been considered that call-time choice induces a singular denotational semantics, while run-time choice induces a plural semantics. We have discovered that this latter identification is wrong when pattern matching is involved, and thus we propose two novel compositional plural semantics for CS's that are different from run-time choice. We study the basic properties of our plural semantics---compositionality, polarity, monotonicity for substitutions, and a restricted form of the bubbling property for constructor systems---and the relation between them and to previous proposals, concluding that these semantics form a hierarchy in the sense of set inclusion of the set of computed values. We have also identified a class of programs characterized by a syntactic criterion for which the proposed plural semantics behave the same, and a program transformation that can be used to simulate one of them by term rewriting. At the practical level, we study how to use the expressive capabilities of these semantics for improving the declarative flavour of programs. We also propose a language which combines call-time choice and our plural semantics, that we have implemented in Maude. The resulting interpreter is employed to test several significant examples showing the capabilities of the combined semantics. To appear in Theory and Practice of Logic Programming (TPLP)Comment: 53 pages, 5 figure

Contribution to characterization of last-generation photodetectors and improvement of their efficiency using micro and nanostructures

Mención Internacional en el título de doctorThe world is going through constant technological changes, and what it seems to be a great improvement to the life in Earth at one moment, can lead to disastrous effects in the future. This has happened several times during the human being history, and one clear example is the climate change, global warming, and greenhouse effect. Since the industrial revolution, the humanity went through several technological changes: some of them allowed us to progress as a civilization, but others will lead us to self-destruction. A recent example is the release of chlorofluorocarbon (CFC) gases that destroyed a huge part of the ozone layer at the Earth’s poles. Nowadays, one of the big problems that we are facing is the massive amount of carbon dioxide that we are throwing into atmosphere, mainly due to the energy generation activities. That is why this thesis is focused on increase the efficiency of devices that produce energy in a cleaner way, using solar energy. Doing so, in a near future we will be able to replace the actual contaminating energy sources for cleaner, non-emitting, renewable energy sources. Of course, this topic is too general, so this work is split in three big sections, intending to give full coverage to the topic. The first section is based onto the building blocks of solar harvesting, i.e., the solar cells. The more mature technology, commercially available is the silicon-based solar cell, but in the last years, a lot of technologies were also developed such as organic photovoltaics or perovskites. Each of these technologies have their own fabrication procedure, being the silicon very expensive and high energy demanding, while in the case of organic or perovskite the fabrication procedures are usually solvent-based and cheaper in terms of energy and material costs. After a brief explanation of the most used thin-film deposition techniques (used on organics and perovskites) the building process of a methylammonium lead iodide perovskite is explained step by step. This fabrication gave a resulting solar cell with a power conversion efficiency of 16.9%. Due to the environmental issues that this novel material can cause (mainly because it has lead in its composition), a lead-free perovskite was also studied (cesium tin iodide). The conclusion extracted from this study is that this lead-free perovskite could have very interesting applications, for example in smart windows, but their electrical conductivity problems should be solved first. Ending with this section, a proof of concept including organic and perovskite photodetectors into a visible light communication system was carried out, resulting in both technologies being able to perform good enough to be part of an audio link (with a bandwith higher than 40 kHz). Once we have a device to work with, in order to stablish their properties, it should be characterized. That is what the second section is about. This characterization must be done in a standardized way, under certain conditions and circumstances. One of these conditions is to have a stable, well-defined illumination source, that can recreate the standard AM1.5G spectrum (which is the spectrum of light that arrives at the Earth’s surface, coming from the Sun). All this restrictions and parameters that dictates whether a light source is valid for this process or not are defined by the International Electrotechnical Commission under the standard IEC 60904-9. During this thesis, due to the necessity of this light to characterize devices, we decided to create one. This gave birth to SUNBOX, our proprietary solar simulator. SUNBOX belongs to a AAA-Class according to the IEC standard, which represents the highest quality possible in solar simulators. It is fully based on light emitting diodes and also customizable, with a tunable spectrum that can go from 0.2 to 1.2 suns and has 14 different wavelengths that can be intensity-tuned freely. It is also clearly distinguishable from the commercial ones because its structure is 3D-printed, so it is lightweight and has a low cost. Due to the intellectual property protection as a utility model, only a brief part regarding the electronic design is explained in this document, together with the calibration procedure that was carried out in terms of spectral match, homogeneity, and temporal instability that qualifies SUNBOX as an AAA-Class solar simulator. At the end of this section, some characterizations made with SUNBOX are shown, using different functionalities, to obtain key parameters in different types of solar cells. The characterization methods that were used, such as I-V curves or spectroscopy impedance are also explained along the document. Finally, in the third section, other approaches to improve the efficiency of the devices were studied, based on the optical treatment of light (light management). This management lies on the ability that some materials have to interact with the incident light, mainly in the form of nanoparticles, nanorods, or small gratings. Using a Finite Element Method simulation software (COMSOL® and JCMSuite®), several results were obtained remarking the importance of the inclusion of a nanostructure inside a device, increasing the amount of photogenerated current by 40% in a hydrogenated amorphous silicon-based device and by 20.5% in a perovskite/silicon tandem solar cell. Furthermore, preliminary results were obtained applying a nanostructure into a deep ultraviolet light emitting diode, that went from a light extraction efficiency value of 4.57% to around 15%, thus, multiplying by three the amount of extracted light with the same electrical power consumption. In summary, the main conclusion of this work is that it is possible to increase the efficiency of actual devices by and important factor and that there is a lot of room for future improvements. A boost in efficiency can be applied not only using novel materials with better electrical and optical properties, but also optimizing the devices that exist nowadays using light management techniques through the inclusion of nanostructures inside these devices. This has been demonstrated during this work using both approaches: the material science, creating a novel material with a cutting-edge fabrication method, unraveling the properties and applications for this material; and the photonics science, simulating the response of the device with the inclusion of a nanostructure in it, showing an outstanding improvement in all three study cases.El mundo actual está constantemente sometido a cambios tecnológicos, y lo que en un momento pudo ser un gran avance para la vida en la Tierra, puede ocasionar efectos desastrosos en el futuro. Esto ha ocurrido en varias ocasiones en la historia de la humanidad y claros ejemplos de ello son el cambio climático, el calentamiento global y el incremento del efecto invernadero. Desde la Revolución Industrial se han producido diversos cambios y avances tecnológicos muy importantes para la sociedad: algunos de ellos nos permitieron avanzar como civilización, pero otros nos dirigen hacia nuestra propia autodestrucción. Un ejemplo reciente podría ser la emisión de los llamados clorofluorocarbonos a la atmósfera, unos gases que destruyeron la mayor parte de la capa de ozono en los polos de la Tierra, ocasionando que una gran parte de radiación solar incidiera en los glaciares polares, incrementando la fusión de ellos y con ello contribuyendo al peligroso deshielo polar. Hoy en día, uno de los grandes problemas a los que nos enfrentamos es la gran cantidad de dióxido de carbono que estamos vertiendo a la atmósfera, principalmente debido a las actividades de generación de energía. Por ello, el objetivo de esta tesis está centrado en incrementar la eficiencia de los dispositivos capaces de producir energía de una forma más limpia, usando la energía solar. De esta forma, en el futuro cercano seremos capaces de sustituir las fuentes de energía contaminantes que usamos actualmente por otras fuentes de energía mas limpia, renovables y que no emitan gases. Cierto es que este tema puede parecer prácticamente inabarcable, y por ello se ha dividido este trabajo en tres secciones principales que se estudian en detalle, para dar cobertura completa a todo el tema. La primera sección está basada en el estudio de las unidades básicas de la recolección de energía solar, las celdas solares. La tecnología más madura comercialmente disponible es la celda solar basada en silicio (tanto monocristalino como policristalino), pero durante los últimos años se han desarrollado otras tecnologías tales como las celdas orgánicas o de perovskita. Cada una de estas tecnologías tiene su propio procedimiento de fabricación, siendo las basadas en silicio las más caras de hacer debido a su procesamiento y a la gran cantidad de energía necesaria para su refinado. Sin embargo, en el caso de las celdas orgánicas y de perovskita los métodos de fabricación están basados en solventes y deposiciones de líquido en capas delgadas, lo que las hace mucho más económicas en términos de materiales y de consumo energético. Después de una breve explicación de las técnicas de deposición de lámina delgada más usadas (aplicables tanto en orgánicas como en perovskitas), se explica el proceso de fabricación paso a paso de una celda solar de yoduro de metilamonio plomo. Esta fabricación dio como resultado una celda solar con un valor de eficiencia del 16.9%. Debido a los problemas ambientales que puede causar este material (ya que contiene plomo, altamente tóxico), durante este trabajo se estudió también una perovskita libre de plomo (yoduro de estaño cesio). La conclusión principal extraída de este estudio es que esta perovskita libre de plomo puede tener aplicaciones muy interesantes, tales como ventanas inteligentes debido a su transparencia, pero sus problemas de conductividad eléctrica deben de ser resueltos en primer lugar, para conseguir un dispositivo eficiente. Para finalizar esta sección, se llevó a cabo una prueba de concepto que consistió en introducir fotodetectores orgánicos y de perovskita en un sistema de comunicación por luz visible (VLC), comprobando que ambas tecnologías respondían de forma correcta para formar parte de un sistema de transmisión de audio (su ancho de banda era superior a 40 kHz en ambos casos). Una vez se dispone de un dispositivo funcional, para poder determinar sus propiedades internas, se debe caracterizar. En esto consiste la segunda sección. Estas caracterizaciones deben hacerse siguiendo los estándares correspondientes, bajo ciertas condiciones y en unas circunstancias determinadas. Una de estas condiciones es tener una fuente de luz estable y bien definida, que pueda recrear el espectro AM1.5G (que es el espectro de luz que llega a la superficie de la Tierra emitido por el Sol) para excitar las muestras que se encuentren bajo análisis. Todas las restricciones y parámetros que determinan si una fuente de luz es adecuada o no para este proceso están definidos por la Comisión Electrotécnica Internacional bajo el estándar IEC 60904-9. Durante el desarrollo de esta tesis, debido a la necesidad de caracterizar dispositivos, se optó por crear una de estas fuentes de luz. Así nació SUNBOX, nuestro simulador solar. SUNBOX pertenece a la clase AAA según el estándar IEC, lo que significa que posee la mayor calidad posible como simulador solar. Está completamente basado en diodos emisores de luz y también es personalizable, con un espectro ajustable que puede cubrir desde 0.2 hasta 1.2 soles. Dispone de 14 longitudes de onda de emisión diferentes que también pueden ser ajustadas libremente, de forma que se pueden realizar análisis en longitudes de onda concretas, tales como azul, ultravioleta o infrarrojo. Es fácilmente distinguible de sus contrapartes comerciales disponibles en el mercado, ya que su chasis está realizado por impresión 3D, así que es muy ligero y de bajo coste. Debido a la protección de la propiedad intelectual bajo un modelo de utilidad y un registro software, solo una parte del diseño electrónico se explica en este documento, junto con todo el procedimiento de calibración que se llevó a cabo en términos de coincidencia espectral, homogeneidad y estabilidad temporal, que clasifican a SUNBOX como un simulador solar de clase AAA. Al final de esta sección, se muestran algunas de las caracterizaciones de dispositivos llevadas a cabo con SUNBOX, usando sus diferentes funcionalidades para obtener parámetros clave de distintos tipos de celdas solares. Los métodos de caracterización llevados a cabo, tales como el trazado de curvas tensión corriente o la espectroscopía de impedancias también se explican en el documento. Por último, en la tercera sección, se estudian otras técnicas para mejorar la eficiencia de los dispositivos, basadas en el tratamiento óptico de la luz (gestión de la luz o “light management”). Esta gestión de la luz se basa en la habilidad que tienen algunos materiales para interactuar con la luz que incide sobre ellos. Normalmente estos materiales necesitan estar en forma de nanopartículas, nanobarras o pequeñas redes de difracción. Usando varios softwares de simulación (COMSOL® y JCMSuite®) basados en el método de elementos finitos (FEM), se han obtenido varios resultados que remarcan la importancia de incluir nanoestructuras dentro de los dispositivos, incrementando la cantidad de corriente fotogenerada en un 40% en un dispositivo basado en silicio amorfo hidrogenado y en un 20.5% en un dispositivo basado en un tándem de perovskita y silicio monocristalino. Además, se han obtenido resultados preliminares que demuestran que estas nanoestructuras pueden ser también muy efectivas no solo en dispositivos receptores de luz, sino también en emisores. En este caso se aplicó una nanoestructura a un diodo emisor de luz ultravioleta profunda, que mejoró su eficiencia de extracción de luz de un 4.57% a alrededor de un 15%, triplicando la cantidad de luz emitida con el mismo consumo de potencia eléctrica. En resumen, la conclusión principal de este trabajo es que es posible incrementar la eficiencia de los dispositivos actuales de una forma sustancial, quedando aún mucho espacio para mejorar. Se ha demostrado que un incremento en la eficiencia puede obtenerse no solo usando materiales novedosos con mejores propiedades ópticas y eléctricas, sino también optimizando los dispositivos existentes actualmente usando técnicas de gestión de la luz a través de la inclusión de nanoestructuras en estos dispositivos. Respecto a la primera aproximación, relacionada con la ciencia de materiales, en este trabajo se ha fabricado un material novedoso usando una técnica de fabricación poco explorada en estas aplicaciones (co-evaporación), descubriendo las propiedades y posibles aplicaciones de este material. Respecto a la segunda aproximación, relacionada con la fotónica, se han creado diseños de nanoestructuras y se ha simulado su respuesta, descubriendo una mejora muy importante en la eficiencia de los tres dispositivos estudiados.The present work has been funded from the following projects: • Comunidad de Madrid through SINFOTON-CM Research Program (S2013/MIT-2790) and SINFOTON2-CM (S2018/NMT-4326) • Ministerio de Economia, Agencia Estatal de Investigación and European Union’s FEDER through TEC2016-77242-C3-(1-R, 2-R and 3-R) AEI/FEDER, UE Projects. • European Research Council (ERC) via Consolidator Grant (724424-No-LIMIT) • Generalitat Valenciana via Prometeo Grant Q-Devices (Prometeo/2018/098) • European Commission via FET Open grant (862656-DROP-IT) Also, this project could not be possible with the financial support of the Ministerio de Educación y Formación Profesional through the following grants that I have received: • Doctoral Grant FPU research fellowship (FPU17/00612). • Research Stay Grant (EST18/00399) supporting my research stay at Jaume I University (Castellón, Spain) • Research Stay Grant (EST19/00073) supporting my research stay at Helmholtz Zentrum Berlin and Zuse Institute Berlin (Berlin, Germany).Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: Javier Alda Serrano.- Secretario: Fernando B. Naranjo Vega.- Vocal: Sven Burge

Rewriting and narrowing for constructor systems with call-time choice semantics

Non-confluent and non-terminating constructor-based term rewrite systems are useful for the purpose of specification and programming. In particular, existing functional logic languages use such kind of rewrite systems to define possibly non-strict non-deterministic functions. The semantics adopted for non-determinism is call-time choice, whose combination with non-strictness is a non trivial issue, addressed years ago from a semantic point of view with the Constructor-based Rewriting Logic (CRWL), a well-known semantic framework commonly accepted as suitable semantic basis of modern functional logic languages. A drawback of CRWL is that it does not come with a proper notion of one-step reduction, which would be very useful to understand and reason about how computations proceed. In this paper we develop thoroughly the theory for the first order version of letrewriting, a simple reduction notion close to that of classical term rewriting, but extended with a let-binding construction to adequately express the combination of call-time choice with non-strict semantics. Let-rewriting can be seen as a particular textual presentation of term graph rewriting. We investigate the properties of let-rewriting, most remarkably their equivalence with respect to a conservative extension of the CRWL-semantics coping with let-bindings, and we show by some case studies that having two interchangeable formal views (reduction/semantics) of the same language is a powerful reasoning tool. After that, we provide a notion of let-narrowing which is adequate for call-time choice as proved by soundness and completeness results of let-narrowing with respect to letre writing. Moreover, we relate those let-rewriting and let-narrowing relations (and hence CRWL) with ordinary term rewriting and narrowing, providing in particular soundness and completeness of let-rewriting with respect to term rewriting for a class of programs which are deterministic in a semantic sense

Estudio de las reacciones [pión menos-protón yendo a dos kaones y un nucleón] en las interacciones [pión menos-protón] a 4.0 Gev/C

Tesis Univ. Complutense de Madrid, 1982.Depto. de Física TeóricaFac. de Ciencias FísicasTRUEProQuestpu

Optical characterization of lead-free Cs2SnI6 double Perovskite Fabricated from degraded and reconstructed CsSnI3 films

Halide perovskites have experienced a huge development in the past years, but they still have two major challenges for their massive implantation: the long-term stability and the use of lead. One of the most obvious lead-free candidates to replace these perovskites is CsSnI3, but due to its poor environmental stability, it has been discarded for the fabrication of stable devices. Nevertheless, ambient degradation of CsSnI3 and ulterior reconstruction produce a relatively stable lead-free Cs2SnI6 double perovskite with interesting optical properties that have not been deeply characterized previously. In this work, the potential use for the optical properties of Cs2SnI6 is studied and compared with that of the most common halide perovskite, CH3NH3PbI3 (MAPbI3). The Cs2SnI6 films stayed in a standard atmosphere for a week without showing any signs of degradation. They also demonstrated better reflective behavior than MAPbI3 and higher absorption in the 650 and 730 nm spectral range, making this material interesting for the development of photodetectors in this region. This study demonstrates that Cs2SnI6 is a promising material for photodevices, as it highlights its main characteristics and optical parameters, giving an original view on the use of the double perovskite, but at the same time emphasizing the need to improve the electrical properties for the development of efficient optoelectronic devices.E.L.-F. wants to express his gratitude to the Ministerio de Educación y Formación Profesional for his doctoral grant (FPU research fellowship FPU17/00612) and his research stay grant (EST18/00399). This work was partially supported by the European Research Council (ERC) via Consolidator Grant (724424-No-LIMIT) and the European Commission via FET Open Grant (862656 - DROP-IT). We acknowledge SCIC from Jaume I University (UJI) for help with XRD and SEM-EDS characterization

A low-cost LED-Based solar simulator

Solar simulators are a fundamental instrument to characterize solar cells parameters, as they can reproduce the operating conditions under which the solar cells are going to work. However, these systems are frequently big, heavy, and expensive, and a small solar simulator could be a good contribution to test small prototyping devices manufactured in research labs, especially if it could manage the irradiation at any wavelength interval in a custom way. We have designed, developed, and calibrated a small solar simulator made entirely with LEDs, no optics inside, and electronically controlled through a PC using an Arduino microcontroller. The whole structure is 3-D printed in black PLA plastic. The electrical current through the LEDs, and thus the spectral irradiance of the simulator, is controlled with a very intuitive LabVIEW interface. As our calibration proves, we have built an easily reproducible and low-cost Class AAA solar simulator in a central illumination area of 1 cm 2 , according to the IEC60904-9 standard. This means that the homogeneity in that area is under a 2% deviation in spatial terms, below 0.5% in temporal terms, and is a factor of a 3% close to the AM1.5G sun reference spectrum. The system can be built and used in any research lab to get quick tests of new small solar cells of any material.This work was supported in part by the Spanish Ministerio de Economía y Competitividad through AEI/FEDER, UE Funds under Grant TEC2016-77242-C3-1-R and in part by the Comunidad de Madrid SINFOTON-CM Research Program under Grant S2013/MIT-2790. The work of E. López-Fraguas was supported by the Ministerio de Educación y Formación Profesional for his Doctoral Grant through FPU Research Fellowship under Grant FPU17/00612

Liberal Typing for Functional Logic Programs

We propose a new type system for functional logic programming which is more liberal than the classical Damas-Milner usually adopted, but it is also restrictive enough to ensure type soundness. Starting from Damas-Milner typing of expressions we propose a new notion of well-typed program that adds support for type-indexed functions, existential types, opaque higher-order patterns and generic functions-as shown by an extensive collection of examples that illustrate the possibilities of our proposal. In the negative side, the types of functions must be declared, and therefore types are checked but not inferred. Another consequence is that parametricity is lost, although the impact of this flaw is limited as "free theorems" were already compromised in functional logic programming because of non-determinism

Efficient light management in a monolithic tandem perovskite /silicon solar cell by using a hybrid metasurface

Solar energy is now dealing with the challenge of overcoming the Shockley&-Queisser limit of single bandgap solar cells. Multilayer solar cells are a promising solution as the so-called third generation of solar cells. The combination of materials with different bandgap energies in multijunction cells enables power conversion efficiencies up to 30% at reasonable costs. However, interfaces between different layers are critical due to optical losses. In this work, we propose a hybrid metasurface in a monolithic perovskite-silicon solar cell. The design takes advantage of light management to optimize the absorption in the perovskite, as well as an efficient light guiding towards the silicon subcell. Furthermore, we have also included the effect of a textured back contact. The optimum proposal provides an enhancement of the matched short-circuit current density of a 20.5% respect to the used planar reference.This research was funded by Ministerio de Economía y Competitividad, grant number TEC2016-77242-C3-1-R Grant (AEI/FEDER, UE funds), and Comunidad de Madrid and FEDER program through the SINFOTON-CM Research (grant number S2013/MIT-2790) and SINFOTON2-CM (granT number S2018/NMT-4326) programs