Correction of the Colour Variations under Uncontrolled Lighting Conditions

Esta tesis trata sobre métodos de corrección que compensan la variación de las condiciones de iluminación en aplicaciones de imagen y video a color. Estas variaciones hacen que a menudo fallen aquellos algoritmos de visión artificial que utilizan características de color para describir los objetos. Se formulan tres preguntas de investigación que definen el marco de trabajo de esta tesis. La primera cuestión aborda las similitudes que se dan entre las imágenes de superficies adyacentes en relación a su comportamiento fotométrico. En base al análisis del modelo de formación de imágenes en situaciones dinámicas, esta tesis propone un modelo capaz de predecir las variaciones de color de la región de una determinada imagen a partir de las variaciones de las regiones colindantes. Dicho modelo se denomina Quotient Relational Model of Regions. Este modelo es válido cuando: las fuentes de luz iluminan todas las superficies incluídas en él; estas superficies están próximas entre sí y tienen orientaciones similares; y cuando son en su mayoría lambertianas. Bajo ciertas circunstancias, la respuesta fotométrica de una región se puede relacionar con el resto mediante una combinación lineal. No se ha podido encontrar en la literatura científica ningún trabajo previo que proponga este tipo de modelo relacional. La segunda cuestión va un paso más allá y se pregunta si estas similitudes se pueden utilizar para corregir variaciones fotométricas desconocidas en una región también desconocida, a partir de regiones conocidas adyacentes. Para ello, se propone un método llamado Linear Correction Mapping capaz de dar una respuesta afirmativa a esta cuestión bajo las circunstancias caracterizadas previamente. Para calcular los parámetros del modelo se requiere una etapa de entrenamiento previo. El método, que inicialmente funciona para una sola cámara, se amplía para funcionar en arquitecturas con varias cámaras sin solape entre sus campos visuales. Para ello, tan solo se necesitan varias muestras de imágenes del mismo objeto capturadas por todas las cámaras. Además, este método tiene en cuenta tanto las variaciones de iluminación, como los cambios en los parámetros de exposición de las cámaras. Todos los métodos de corrección de imagen fallan cuando la imagen del objeto que tiene que ser corregido está sobreexpuesta o cuando su relación señal a ruido es muy baja. Así, la tercera cuestión se refiere a si se puede establecer un proceso de control de la adquisición que permita obtener una exposición óptima cuando las condiciones de iluminación no están controladas. De este modo, se propone un método denominado Camera Exposure Control capaz de mantener una exposición adecuada siempre y cuando las variaciones de iluminación puedan recogerse dentro del margen dinámico de la cámara. Los métodos propuestos se evaluaron individualmente. La metodología llevada a cabo en los experimentos consistió en, primero, seleccionar algunos escenarios que cubrieran situaciones representativas donde los métodos fueran válidos teóricamente. El Linear Correction Mapping fue validado en tres aplicaciones de re-identificación de objetos (vehículos, caras y personas) que utilizaban como caracterísiticas la distribución de color de éstos. Por otra parte, el Camera Exposure Control se probó en un parking al aire libre. Además de esto, se definieron varios indicadores que permitieron comparar objetivamente los resultados de los métodos propuestos con otros métodos relevantes de corrección y auto exposición referidos en el estado del arte. Los resultados de la evaluación demostraron que los métodos propuestos mejoran los métodos comparados en la mayoría de las situaciones. Basándose en los resultados obtenidos, se puede decir que las respuestas a las preguntas de investigación planteadas son afirmativas, aunque en circunstancias limitadas. Esto quiere decir que, las hipótesis planteadas respecto a la predicción, la corrección basada en ésta y la auto exposición, son factibles en aquellas situaciones identificadas a lo largo de la tesis pero que, sin embargo, no se puede garantizar que se cumplan de manera general. Por otra parte, se señalan como trabajo de investigación futuro algunas cuestiones nuevas y retos científicos que aparecen a partir del trabajo presentado en esta tesis. ABSTRACT This thesis discusses the correction methods used to compensate the variation of lighting conditions in colour image and video applications. These variations are such that Computer Vision algorithms that use colour features to describe objects mostly fail. Three research questions are formulated that define the framework of the thesis. The first question addresses the similarities of the photometric behaviour between images of dissimilar adjacent surfaces. Based on the analysis of the image formation model in dynamic situations, this thesis proposes a model that predicts the colour variations of the region of an image from the variations of the surrounded regions. This proposed model is called the Quotient Relational Model of Regions. This model is valid when the light sources illuminate all of the surfaces included in the model; these surfaces are placed close each other, have similar orientations, and are primarily Lambertian. Under certain circumstances, a linear combination is established between the photometric responses of the regions. Previous work that proposed such a relational model was not found in the scientific literature. The second question examines whether those similarities could be used to correct the unknown photometric variations in an unknown region from the known adjacent regions. A method is proposed, called Linear Correction Mapping, which is capable of providing an affirmative answer under the circumstances previously characterised. A training stage is required to determine the parameters of the model. The method for single camera scenarios is extended to cover non-overlapping multi-camera architectures. To this extent, only several image samples of the same object acquired by all of the cameras are required. Furthermore, both the light variations and the changes in the camera exposure settings are covered by correction mapping. Every image correction method is unsuccessful when the image of the object to be corrected is overexposed or the signal-to-noise ratio is very low. Thus, the third question refers to the control of the acquisition process to obtain an optimal exposure in uncontrolled light conditions. A Camera Exposure Control method is proposed that is capable of holding a suitable exposure provided that the light variations can be collected within the dynamic range of the camera. Each one of the proposed methods was evaluated individually. The methodology of the experiments consisted of first selecting some scenarios that cover the representative situations for which the methods are theoretically valid. Linear Correction Mapping was validated using three object re-identification applications (vehicles, faces and persons) based on the object colour distributions. Camera Exposure Control was proved in an outdoor parking scenario. In addition, several performance indicators were defined to objectively compare the results with other relevant state of the art correction and auto-exposure methods. The results of the evaluation demonstrated that the proposed methods outperform the compared ones in the most situations. Based on the obtained results, the answers to the above-described research questions are affirmative in limited circumstances, that is, the hypothesis of the forecasting, the correction based on it, and the auto exposure are feasible in the situations identified in the thesis, although they cannot be guaranteed in general. Furthermore, the presented work raises new questions and scientific challenges, which are highlighted as future research work.

Optimization and evaluation in space conditions of multi-GHz optical modulators

Among the different optical modulator technologies available such as polymer, III-V semiconductors, Silicon, the well-known Lithium Niobate (LN) offers the best trade-off in terms of performances, ease of use, and power handling capability [1-9]. The LN technology is still widely deployed within the current high data rate fibre optic communications networks. This technology is also the most mature and guarantees the reliability which is required for space applications [9].In or der to fulfil the target specifications of opto-microwave payloads, an optimization of the design of a Mach-Zehnder (MZ) modulator working at the 1500nm telecom wavelength was performed in the frame of the ESA-ARTES "Multi GigaHertz Optical Modulator" (MGOM) project in order to reach ultra-low optical insertion loss and low effective driving voltage in the Ka band. The selected modulator configuration was the X-cut crystal orientation, associated to high stability Titanium in-diffusion process for the optical waveguide. Starting from an initial modulator configuration exhibiting 9 V drive voltage @ 30 GHz, a complete redesign of the coplanar microwave electrodes was carried out in order to reach a 6 V drive voltage @ 30GHz version. This redesign was associated to an optimization of the interaction between the optical waveguide and the electrodes. Following the optimisation steps, an evaluation program was applied on a lot of 8 identical modulators. A full characterisation was carried out to compare performances, showing small variations between the initial and final functional characteristics. In parallel, two similar modulators were submitted to both gamma (10-100 krad) and proton irradiation (10.109 p/cm²) with minor performance degradation.

Conditions for perfect focusing multiple point sources with the SMS design method

In this work, we demonstrate how it is possible to sharply image multiple object points. The Simultaneous Multiple Surface (SMS) design method has usually been presented as a method to couple N wave-front pairs with N surfaces, but recent findings show that when using N surfaces, we can obtain M image points when Nconditions. We present the evolution of SMS method, from its basics, to imaging two object points through one surface, the transition from two to three objet points obtained by increasing the parallelism, and getting to the designs of six surfaces imaging up to eight object points. These designs are limited with the condition that the surfaces cannot be placed at the aperture stop. In the process of maximizing the object points to sharp image, we try to exhaust the degrees of freedom of aspherics and free-forms. We conjecture that maximal SMS designs are very close to a good solution, hence using them as a starting point for the optimization will lead us faster to a final optical system. We suggest here different optimization strategies which combined with the SMS method are proven to give the best solution. Through the example of imaging with the high aspect ratio, we compare the results obtained optimizing the rotational lens and using a combination of SMS method and optimization, showing that the second approach is giving significantly smaller value of overall RMS spot diameter.

Selection, training and validation process of a sensory panel for bread analysis: Influence of cultivar on the quality of breads made from common wheat and spelta wheat

A protocol of selection, training and validation of the members of the panel for bread sensory analysis is proposed to assess the influence of wheat cultivar on the sensory quality of bread. Three cultivars of bread wheat and two cultivars of spelt wheat organically-grown under the same edaphoclimatic conditions were milled and baked using the same milling and baking procedure. Through the use of triangle tests, differences were identified between the five breads. Significant differences were found between the spelt breads and those made with bread wheat for the attributes ?crumb cell homogeneity? and ?crumb elasticity?. Significant differences were also found for the odor and flavor attributes, with the bread made with ?Espelta Navarra? being the most complex, from a sensory point of view. Based on the results of this study, we propose that sensory properties should be considered as breeding criteria for future work on genetic improvement.

Método experimental para la caracterización de las diferentes tecnologías de integración arquitectónica de la energía fotovoltaica en condiciones de funcionamiento real = Experimental method for characterization of several building integrated photovoltaic technologies under real working conditions

Hoy en día, el proceso de un proyecto sostenible persigue realizar edificios de elevadas prestaciones que son, energéticamente eficientes, saludables y económicamente viables utilizando sabiamente recursos renovables para minimizar el impacto sobre el medio ambiente reduciendo, en lo posible, la demanda de energía, lo que se ha convertido, en la última década, en una prioridad. La Directiva 2002/91/CE "Eficiencia Energética de los Edificios" (y actualizaciones posteriores) ha establecido el marco regulatorio general para el cálculo de los requerimientos energéticos mínimos. Desde esa fecha, el objetivo de cumplir con las nuevas directivas y protocolos ha conducido las políticas energéticas de los distintos países en la misma dirección, centrándose en la necesidad de aumentar la eficiencia energética en los edificios, la adopción de medidas para reducir el consumo, y el fomento de la generación de energía a través de fuentes renovables. Los edificios de energía nula o casi nula (ZEB, Zero Energy Buildings ó NZEB, Net Zero Energy Buildings) deberán convertirse en un estándar de la construcción en Europa y con el fin de equilibrar el consumo de energía, además de reducirlo al mínimo, los edificios necesariamente deberán ser autoproductores de energía. Por esta razón, la envolvente del edifico y en particular las fachadas son importantes para el logro de estos objetivos y la tecnología fotovoltaica puede tener un papel preponderante en este reto. Para promover el uso de la tecnología fotovoltaica, diferentes programas de investigación internacionales fomentan y apoyan soluciones para favorecer la integración completa de éstos sistemas como elementos arquitectónicos y constructivos, los sistemas BIPV (Building Integrated Photovoltaic), sobre todo considerando el próximo futuro hacia edificios NZEB. Se ha constatado en este estudio que todavía hay una falta de información útil disponible sobre los sistemas BIPV, a pesar de que el mercado ofrece una interesante gama de soluciones, en algunos aspectos comparables a los sistemas tradicionales de construcción. Pero por el momento, la falta estandarización y de una regulación armonizada, además de la falta de información en las hojas de datos técnicos (todavía no comparables con las mismas que están disponibles para los materiales de construcción), hacen difícil evaluar adecuadamente la conveniencia y factibilidad de utilizar los componentes BIPV como parte integrante de la envolvente del edificio. Organizaciones internacionales están trabajando para establecer las normas adecuadas y procedimientos de prueba y ensayo para comprobar la seguridad, viabilidad y fiabilidad estos sistemas. Sin embargo, hoy en día, no hay reglas específicas para la evaluación y caracterización completa de un componente fotovoltaico de integración arquitectónica de acuerdo con el Reglamento Europeo de Productos de la Construcción, CPR 305/2011. Los productos BIPV, como elementos de construcción, deben cumplir con diferentes aspectos prácticos como resistencia mecánica y la estabilidad; integridad estructural; seguridad de utilización; protección contra el clima (lluvia, nieve, viento, granizo), el fuego y el ruido, aspectos que se han convertido en requisitos esenciales, en la perspectiva de obtener productos ambientalmente sostenibles, saludables, eficientes energéticamente y económicamente asequibles. Por lo tanto, el módulo / sistema BIPV se convierte en una parte multifuncional del edificio no sólo para ser física y técnicamente "integrado", además de ser una oportunidad innovadora del diseño. Las normas IEC, de uso común en Europa para certificar módulos fotovoltaicos -IEC 61215 e IEC 61646 cualificación de diseño y homologación del tipo para módulos fotovoltaicos de uso terrestre, respectivamente para módulos fotovoltaicos de silicio cristalino y de lámina delgada- atestan únicamente la potencia del módulo fotovoltaico y dan fe de su fiabilidad por un período de tiempo definido, certificando una disminución de potencia dentro de unos límites. Existe también un estándar, en parte en desarrollo, el IEC 61853 (“Ensayos de rendimiento de módulos fotovoltaicos y evaluación energética") cuyo objetivo es la búsqueda de procedimientos y metodologías de prueba apropiados para calcular el rendimiento energético de los módulos fotovoltaicos en diferentes condiciones climáticas. Sin embargo, no existen ensayos normalizados en las condiciones específicas de la instalación (p. ej. sistemas BIPV de fachada). Eso significa que es imposible conocer las efectivas prestaciones de estos sistemas y las condiciones ambientales que se generan en el interior del edificio. La potencia nominal de pico Wp, de un módulo fotovoltaico identifica la máxima potencia eléctrica que éste puede generar bajo condiciones estándares de medida (STC: irradición 1000 W/m2, 25 °C de temperatura del módulo y distribución espectral, AM 1,5) caracterizando eléctricamente el módulo PV en condiciones específicas con el fin de poder comparar los diferentes módulos y tecnologías. El vatio pico (Wp por su abreviatura en inglés) es la medida de la potencia nominal del módulo PV y no es suficiente para evaluar el comportamiento y producción del panel en términos de vatios hora en las diferentes condiciones de operación, y tampoco permite predecir con convicción la eficiencia y el comportamiento energético de un determinado módulo en condiciones ambientales y de instalación reales. Un adecuado elemento de integración arquitectónica de fachada, por ejemplo, debería tener en cuenta propiedades térmicas y de aislamiento, factores como la transparencia para permitir ganancias solares o un buen control solar si es necesario, aspectos vinculados y dependientes en gran medida de las condiciones climáticas y del nivel de confort requerido en el edificio, lo que implica una necesidad de adaptación a cada contexto específico para obtener el mejor resultado. Sin embargo, la influencia en condiciones reales de operación de las diferentes soluciones fotovoltaicas de integración, en el consumo de energía del edificio no es fácil de evaluar. Los aspectos térmicos del interior del ambiente o de iluminación, al utilizar módulos BIPV semitransparentes por ejemplo, son aún desconocidos. Como se dijo antes, la utilización de componentes de integración arquitectónica fotovoltaicos y el uso de energía renovable ya es un hecho para producir energía limpia, pero también sería importante conocer su posible contribución para mejorar el confort y la salud de los ocupantes del edificio. Aspectos como el confort, la protección o transmisión de luz natural, el aislamiento térmico, el consumo energético o la generación de energía son aspectos que suelen considerarse independientemente, mientras que todos juntos contribuyen, sin embargo, al balance energético global del edificio. Además, la necesidad de dar prioridad a una orientación determinada del edificio, para alcanzar el mayor beneficio de la producción de energía eléctrica o térmica, en el caso de sistemas activos y pasivos, respectivamente, podría hacer estos últimos incompatibles, pero no necesariamente. Se necesita un enfoque holístico que permita arquitectos e ingenieros implementar sistemas tecnológicos que trabajen en sinergia. Se ha planteado por ello un nuevo concepto: "C-BIPV, elemento fotovoltaico consciente integrado", esto significa necesariamente conocer los efectos positivos o negativos (en términos de confort y de energía) en condiciones reales de funcionamiento e instalación. Propósito de la tesis, método y resultados Los sistemas fotovoltaicos integrados en fachada son a menudo soluciones de vidrio fácilmente integrables, ya que por lo general están hechos a medida. Estos componentes BIPV semitransparentes, integrados en el cerramiento proporcionan iluminación natural y también sombra, lo que evita el sobrecalentamiento en los momentos de excesivo calor, aunque como componente estático, asimismo evitan las posibles contribuciones pasivas de ganancias solares en los meses fríos. Además, la temperatura del módulo varía considerablemente en ciertas circunstancias influenciada por la tecnología fotovoltaica instalada, la radiación solar, el sistema de montaje, la tipología de instalación, falta de ventilación, etc. Este factor, puede suponer un aumento adicional de la carga térmica en el edificio, altamente variable y difícil de cuantificar. Se necesitan, en relación con esto, más conocimientos sobre el confort ambiental interior en los edificios que utilizan tecnologías fotovoltaicas integradas, para abrir de ese modo, una nueva perspectiva de la investigación. Con este fin, se ha diseñado, proyectado y construido una instalación de pruebas al aire libre, el BIPV Env-lab "BIPV Test Laboratory", para la caracterización integral de los diferentes módulos semitransparentes BIPV. Se han definido también el método y el protocolo de ensayos de caracterización en el contexto de un edificio y en condiciones climáticas y de funcionamiento reales. Esto ha sido posible una vez evaluado el estado de la técnica y la investigación, los aspectos que influyen en la integración arquitectónica y los diferentes tipos de integración, después de haber examinado los métodos de ensayo para los componentes de construcción y fotovoltaicos, en condiciones de operación utilizadas hasta ahora. El laboratorio de pruebas experimentales, que consiste en dos habitaciones idénticas a escala real, 1:1, ha sido equipado con sensores y todos los sistemas de monitorización gracias a los cuales es posible obtener datos fiables para evaluar las prestaciones térmicas, de iluminación y el rendimiento eléctrico de los módulos fotovoltaicos. Este laboratorio permite el estudio de tres diferentes aspectos que influencian el confort y consumo de energía del edificio: el confort térmico, lumínico, y el rendimiento energético global (demanda/producción de energía) de los módulos BIPV. Conociendo el balance de energía para cada tecnología solar fotovoltaica experimentada, es posible determinar cuál funciona mejor en cada caso específico. Se ha propuesto una metodología teórica para la evaluación de estos parámetros, definidos en esta tesis como índices o indicadores que consideran cuestiones relacionados con el bienestar, la energía y el rendimiento energético global de los componentes BIPV. Esta metodología considera y tiene en cuenta las normas reglamentarias y estándares existentes para cada aspecto, relacionándolos entre sí. Diferentes módulos BIPV de doble vidrio aislante, semitransparentes, representativos de diferentes tecnologías fotovoltaicas (tecnología de silicio monocristalino, m-Si; de capa fina en silicio amorfo unión simple, a-Si y de capa fina en diseleniuro de cobre e indio, CIS) fueron seleccionados para llevar a cabo una serie de pruebas experimentales al objeto de demostrar la validez del método de caracterización propuesto. Como resultado final, se ha desarrollado y generado el Diagrama Caracterización Integral DCI, un sistema gráfico y visual para representar los resultados y gestionar la información, una herramienta operativa útil para la toma de decisiones con respecto a las instalaciones fotovoltaicas. Este diagrama muestra todos los conceptos y parámetros estudiados en relación con los demás y ofrece visualmente toda la información cualitativa y cuantitativa sobre la eficiencia energética de los componentes BIPV, por caracterizarlos de manera integral. ABSTRACT A sustainable design process today is intended to produce high-performance buildings that are energy-efficient, healthy and economically feasible, by wisely using renewable resources to minimize the impact on the environment and to reduce, as much as possible, the energy demand. In the last decade, the reduction of energy needs in buildings has become a top priority. The Directive 2002/91/EC “Energy Performance of Buildings” (and its subsequent updates) established a general regulatory framework’s methodology for calculation of minimum energy requirements. Since then, the aim of fulfilling new directives and protocols has led the energy policies in several countries in a similar direction that is, focusing on the need of increasing energy efficiency in buildings, taking measures to reduce energy consumption, and fostering the use of renewable sources. Zero Energy Buildings or Net Zero Energy Buildings will become a standard in the European building industry and in order to balance energy consumption, buildings, in addition to reduce the end-use consumption should necessarily become selfenergy producers. For this reason, the façade system plays an important role for achieving these energy and environmental goals and Photovoltaic can play a leading role in this challenge. To promote the use of photovoltaic technology in buildings, international research programs encourage and support solutions, which favors the complete integration of photovoltaic devices as an architectural element, the so-called BIPV (Building Integrated Photovoltaic), furthermore facing to next future towards net-zero energy buildings. Therefore, the BIPV module/system becomes a multifunctional building layer, not only physically and functionally “integrated” in the building, but also used as an innovative chance for the building envelope design. It has been found in this study that there is still a lack of useful information about BIPV for architects and designers even though the market is providing more and more interesting solutions, sometimes comparable to the existing traditional building systems. However at the moment, the lack of an harmonized regulation and standardization besides to the non-accuracy in the technical BIPV datasheets (not yet comparable with the same ones available for building materials), makes difficult for a designer to properly evaluate the fesibility of this BIPV components when used as a technological system of the building skin. International organizations are working to establish the most suitable standards and test procedures to check the safety, feasibility and reliability of BIPV systems. Anyway, nowadays, there are no specific rules for a complete characterization and evaluation of a BIPV component according to the European Construction Product Regulation, CPR 305/2011. BIPV products, as building components, must comply with different practical aspects such as mechanical resistance and stability; structural integrity; safety in use; protection against weather (rain, snow, wind, hail); fire and noise: aspects that have become essential requirements in the perspective of more and more environmentally sustainable, healthy, energy efficient and economically affordable products. IEC standards, commonly used in Europe to certify PV modules (IEC 61215 and IEC 61646 respectively crystalline and thin-film ‘Terrestrial PV Modules-Design Qualification and Type Approval’), attest the feasibility and reliability of PV modules for a defined period of time with a limited power decrease. There is also a standard (IEC 61853, ‘Performance Testing and Energy Rating of Terrestrial PV Modules’) still under preparation, whose aim is finding appropriate test procedures and methodologies to calculate the energy yield of PV modules under different climate conditions. Furthermore, the lack of tests in specific conditions of installation (e.g. façade BIPV devices) means that it is difficult knowing the exact effective performance of these systems and the environmental conditions in which the building will operate. The nominal PV power at Standard Test Conditions, STC (1.000 W/m2, 25 °C temperature and AM 1.5) is usually measured in indoor laboratories, and it characterizes the PV module at specific conditions in order to be able to compare different modules and technologies on a first step. The “Watt-peak” is not enough to evaluate the panel performance in terms of Watt-hours of various modules under different operating conditions, and it gives no assurance of being able to predict the energy performance of a certain module at given environmental conditions. A proper BIPV element for façade should take into account thermal and insulation properties, factors as transparency to allow solar gains if possible or a good solar control if necessary, aspects that are linked and high dependent on climate conditions and on the level of comfort to be reached. However, the influence of different façade integrated photovoltaic solutions on the building energy consumption is not easy to assess under real operating conditions. Thermal aspects, indoor temperatures or luminance level that can be expected using building integrated PV (BIPV) modules are not well known. As said before, integrated photovoltaic BIPV components and the use of renewable energy is already a standard for green energy production, but would also be important to know the possible contribution to improve the comfort and health of building occupants. Comfort, light transmission or protection, thermal insulation or thermal/electricity power production are aspects that are usually considered alone, while all together contribute to the building global energy balance. Besides, the need to prioritize a particular building envelope orientation to harvest the most benefit from the electrical or thermal energy production, in the case of active and passive systems respectively might be not compatible, but also not necessary. A holistic approach is needed to enable architects and engineers implementing technological systems working in synergy. A new concept have been suggested: “C-BIPV, conscious integrated BIPV”. BIPV systems have to be “consciously integrated” which means that it is essential to know the positive and negative effects in terms of comfort and energy under real operating conditions. Purpose of the work, method and results The façade-integrated photovoltaic systems are often glass solutions easily integrable, as they usually are custommade. These BIPV semi-transparent components integrated as a window element provides natural lighting and shade that prevents overheating at times of excessive heat, but as static component, likewise avoid the possible solar gains contributions in the cold months. In addition, the temperature of the module varies considerably in certain circumstances influenced by the PV technology installed, solar radiation, mounting system, lack of ventilation, etc. This factor may result in additional heat input in the building highly variable and difficult to quantify. In addition, further insights into the indoor environmental comfort in buildings using integrated photovoltaic technologies are needed to open up thereby, a new research perspective. This research aims to study their behaviour through a series of experiments in order to define the real influence on comfort aspects and on global energy building consumption, as well as, electrical and thermal characteristics of these devices. The final objective was to analyze a whole set of issues that influence the global energy consumption/production in a building using BIPV modules by quantifying the global energy balance and the BIPV system real performances. Other qualitative issues to be studied were comfort aspect (thermal and lighting aspects) and the electrical behaviour of different BIPV technologies for vertical integration, aspects that influence both energy consumption and electricity production. Thus, it will be possible to obtain a comprehensive global characterization of BIPV systems. A specific design of an outdoor test facility, the BIPV Env-lab “BIPV Test Laboratory”, for the integral characterization of different BIPV semi-transparent modules was developed and built. The method and test protocol for the BIPV characterization was also defined in a real building context and weather conditions. This has been possible once assessed the state of the art and research, the aspects that influence the architectural integration and the different possibilities and types of integration for PV and after having examined the test methods for building and photovoltaic components, under operation conditions heretofore used. The test laboratory that consists in two equivalent test rooms (1:1) has a monitoring system in which reliable data of thermal, daylighting and electrical performances can be obtained for the evaluation of PV modules. The experimental set-up facility (testing room) allows studying three different aspects that affect building energy consumption and comfort issues: the thermal indoor comfort, the lighting comfort and the energy performance of BIPV modules tested under real environmental conditions. Knowing the energy balance for each experimented solar technology, it is possible to determine which one performs best. A theoretical methodology has been proposed for evaluating these parameters, as defined in this thesis as indices or indicators, which regard comfort issues, energy and the overall performance of BIPV components. This methodology considers the existing regulatory standards for each aspect, relating them to one another. A set of insulated glass BIPV modules see-through and light-through, representative of different PV technologies (mono-crystalline silicon technology, mc-Si, amorphous silicon thin film single junction, a-Si and copper indium selenide thin film technology CIS) were selected for a series of experimental tests in order to demonstrate the validity of the proposed characterization method. As result, it has been developed and generated the ICD Integral Characterization Diagram, a graphic and visual system to represent the results and manage information, a useful operational tool for decision-making regarding to photovoltaic installations. This diagram shows all concepts and parameters studied in relation to each other and visually provides access to all the results obtained during the experimental phase to make available all the qualitative and quantitative information on the energy performance of the BIPV components by characterizing them in a comprehensive way.

Hydrostatic instabilities in floating zone cristal growth process

If only Fluid Mechanics aspects are considered, the configuration appearing in the floating zone technique for crystal growth can be modelled as a mass of liquid spanning between two solid rods. Besides, if now the influence of temperature gradients and heat flow are not considered, the simplest fluid model consists of an isothermal liquid mass of constant properties (density and surface tension) held by capillary forces between two solid disks placed a distance L apart: the so called liquid bridge. As it is well known, if both supporting disks were parallel, coaxial and of the same diameter, 2R, the volume of liquid, V, were equal to that of a cylinder of the same L and R (V=KR~L) and no body forces were acting on the liquid column, the fluid configuration (under these conditions of cylindrical shape) will become unstable when the distance between the disks equals the length of the circumference of the supporting disks (L=2KR, the so-called Rayleigh stability limit). One should be aware that the Rayleigh stability limit can be dramatically modified when the geometry differs from the above described cylinder (due to having non-coaxial disks, different diameter disks, liquid volume different from the cylindrical one, etc) or when other external effects like accelerations either axial or lateral are considered. In this paper the stability limits of liquid bridges considering different types of perturbations are reviewed.

Fluid-solid interaction in arteries incorporating the autoregulation concept in boundary conditions

In pre-surgery decisions in hospital emergency cases, fast and reliable results of the solid and fluid mechanics problems are of great interest to clinicians. In the current investigation, an iterative process based on a pressure-type boundary condition is proposed in order to reduce the computational costs of blood flow simulations in arteries, without losing control of the important clinical parameters. The incorporation of cardiovascular autoregulation, together with the well-known impedance boundary condition, forms the basis of the proposed methodology. With autoregulation, the instabilities associated with conventional pressure-type or impedance boundary conditions are avoided without an excessive increase in computational costs. The general behaviour of pulsatile blood flow in arteries, which is important from the clinical point of view, is well reproduced through this new methodology. In addition, the interaction between the blood and the arterial walls occurs via a modified weak coupling, which makes the simulation more stable and computationally efficient. Based on in vitro experiments, the hyperelastic behaviour of the wall is characterised and modelled. The applications and benefits of the proposed pressure-type boundary condition are shown in a model of an idealised aortic arch with and without an ascending aorta dissection, which is a common cardiovascular disorder.

Building intuition of iron evolution during solar cell processing through analysis of different process models

An important aspect of Process Simulators for photovoltaics is prediction of defect evolution during device fabrication. Over the last twenty years, these tools have accelerated process optimization, and several Process Simulators for iron, a ubiquitous and deleterious impurity in silicon, have been developed. The diversity of these tools can make it difficult to build intuition about the physics governing iron behavior during processing. Thus, in one unified software environment and using self-consistent terminology, we combine and describe three of these Simulators. We vary structural defect distribution and iron precipitation equations to create eight distinct Models, which we then use to simulate different stages of processing. We find that the structural defect distribution influences the final interstitial iron concentration ([Fe-i]) more strongly than the iron precipitation equations. We identify two regimes of iron behavior: (1) diffusivity-limited, in which iron evolution is kinetically limited and bulk [Fe-i] predictions can vary by an order of magnitude or more, and (2) solubility-limited, in which iron evolution is near thermodynamic equilibrium and the Models yield similar results. This rigorous analysis provides new intuition that can inform Process Simulation, material, and process development, and it enables scientists and engineers to choose an appropriate level of Model complexity based on wafer type and quality, processing conditions, and available computation time.

Evaluation of the PV cell operation temperature in the process of fast switching to open-circuit mode

A procedure for measuring the overheating temperature (ΔT ) of a p-n junction area in the structure of photovoltaic (PV) cells converting laser or solar radiations relative to the ambient temperature has been proposed for the conditions of connecting to an electric load. The basis of the procedure is the measurement of the open-circuit voltage (VO C ) during the initial time period after the fast disconnection of the external resistive load. The simultaneous temperature control on an external heated part of a PV module gives the means for determining the value of VO C at ambient temperature. Comparing it with that measured after switching OFF the load makes the calculation of ΔT possible. Calibration data on the VO C = f(T ) dependences for single-junction AlGaAs/GaAs and triple-junction InGaP/GaAs/Ge PV cells are presented. The temperature dynamics in the PV cells has been determined under flash illumination and during fast commutation of the load. Temperature measurements were taken in two cases: converting continuous laser power by single-junction cells and converting solar power by triple-junction cells operating in the concentrator modules.

Mechanical behaviour and formation process of silkworm silk gut

High performance silk fibers were produced directly from the silk glands of silkworms ("Bombyx mori") following an alternative route to natural spinning. This route is based on a traditional procedure that consists of soaking the silk glands in a vinegar solution and stretching them by hand leading to the so called silkworm guts. Here we present, to the authors’ best knowledge, the first comprehensive study on the formation, properties and microstructure of silkworm gut fibers. Comparison of the tensile properties and microstructural organization of the silkworm guts with those of naturally spun fibers allows gain of a deeper insight into the mechanisms that lead to the formation of the fiber, as well as the relationship between the microstructure and properties of these materials. In this regard, it is proved that an acidic environment and subsequent application of tensile stress in the range of 1000 kPa are sufficient conditions for the formation of a silk fiber.