Educational Systems and Gender Segregation in Education: A Three-Country Comparison of Germany, Norway and Canada

How do institutional settings and their embedded policy principles affect gender-typed enrolment in educational programmes? Based on gender-sensitive theories on career choice, we hypothesised that gender segregation in education is higher with a wider range of offers of vocational programmes. By analysing youth survey and panel data, we tested this assumption for Germany, Norway and Canada, three countries whose educational systems represent a different mix of academic, vocational and universalistic education principles. We found that vocational programmes are considerably more gender-segregated than are academic (e.g. university) programmes. Men, more so than women, can avoid gender-typed programmes by passing on to a university education. This in turn means that as long as their secondary school achievement does not allow for a higher education career, they have a higher likelihood of being allocated to male-typed programmes in the vocational education and training (VET) system. In addition, social background and the age at which students have to choose educational offers impact on the transition to gendered educational programmes. Overall, gender segregation in education is highest in Germany and the lowest in Canada. We interpret the differences between these countries with respect to the constellations of educational principles and policies in the respective countries.

A numerical discrete element study on the influence of an embedded viscoelastic-plastic layer at different viscosity values

The major aim of this study was to examine the influence of an embedded viscoelastic-plastic layer at different viscosity values on accretionary wedges at subduction zones. To quantify the effects of the layer viscosity, we analysed the wedge geometry, accretion mode, thrust systems and mass transport pattern. Therefore, we developed a numerical 2D 'sandbox' model utilising the Discrete Element Method. Starting with a simple pure Mohr Coulomb sequence, we added an embedded viscoelastic-plastic layer within the brittle, undeformed 'sediment' package. This layer followed Burger's rheology, which simulates the creep behaviour of natural rocks, such as evaporites. This layer got thrusted and folded during the subduction process. The testing of different bulk viscosity values, from 1 �� 10**13 to 1 �� 10**14 (Pa s), revealed a certain range where an active detachment evolved within the viscoelastic-plastic layer that decoupled the over- and the underlying brittle strata. This mid-level detachment caused the evolution of a frontally accreted wedge above it and a long underthrusted and subsequently basally accreted sequence beneath it. Both sequences were characterised by specific mass transport patterns depending on the used viscosity value. With decreasing bulk viscosities, thrust systems above this weak mid-level detachment became increasingly symmetrical and the particle uplift was reduced, as would be expected for a salt controlled forearc in nature. Simultaneously, antiformal stacking was favoured over hinterland dipping in the lower brittle layer and overturning of the uplifted material increased. Hence, we validated that the viscosity of an embedded detachment strongly influences the whole wedge mechanics, both the respective lower slope and the upper slope duplex, shown by e.g. the mass transport pattern.

Incentives Embedded in Institutions: The Case of Share Contracts in Ghanaian Cocoa Production

Providing price incentives to farmers is usually considered essential for agricultural development. Although such incentives are important, regarding price as the sole explanatory factor is far from satisfactory in understanding the complex realities of agricultural production in Africa. By analyzing the share contracts widely practiced in Ghana, this article argues that local institutions such as land tenure systems and agrarian contracts provide strong incentives and disincentives for agricultural production. Based on data derived from fieldwork in the 1990s, the study analyzes two types of share contracts and the incentive structures embedded in them. The analysis reveals that farmers' investment behavior needs to be understood in terms of both short-term incentive to increase yield and long-term incentive to strengthen land rights. The study concludes that the role of price incentives in agricultural production needs to be reconsidered by placing it in wider incentive structures embedded in local institutions.

Modulation-mode Assignment for SVD-assisted Multiuser MIMO Systems with Correlation.

Multiuser multiple-input multiple-output (MIMO) downlink (DL) transmission schemes experience both multiuser interference as well as inter-antenna interference. The singular value decomposition provides an appropriate mean to process channel information and allows us to take the individual user���s channel characteristics into account rather than treating all users channels jointly as in zero-forcing (ZF) multiuser transmission techniques. However, uncorrelated MIMO channels has attracted a lot of attention and reached a state of maturity. By contrast, the performance analysis in the presence of antenna fading correlation, which decreases the channel capacity, requires substantial further research. The joint optimization of the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power shows that not necessarily all user-speci���c MIMO layers has to be activated in order to minimize the overall BER under the constraint of a given ���xed data throughput.

Fault Tolerance Analysis and Self-Healing Strategy of Autonomous, Evolvable Hardware Systems

This paper presents an analysis of the fault tolerance achieved by an autonomous, fully embedded evolvable hardware system, which uses a combination of partial dynamic reconfiguration and an evolutionary algorithm (EA). It demonstrates that the system may self-recover from both transient and cumulative permanent faults. This self-adaptive system, based on a 2D array of 16 (4��4) Processing Elements (PEs), is tested with an image filtering application. Results show that it may properly recover from faults in up to 3 PEs, that is, more than 18% cumulative permanent faults. Two fault models are used for testing purposes, at PE and CLB levels. Two self-healing strategies are also introduced, depending on whether fault diagnosis is available or not. They are based on scrubbing, fitness evaluation, dynamic partial reconfiguration and in-system evolutionary adaptation. Since most of these adaptability features are already available on the system for its normal operation, resource cost for self-healing is very low (only some code additions in the internal microprocessor core)

Energy/power consumption model for an embedded processor board

This dissertation, whose research has been conducted at the Group of Electronic and Microelectronic Design (GDEM) within the framework of the project Power Consumption Control in Multimedia Terminals (PCCMUTE), focuses on the development of an energy estimation model for the battery-powered embedded processor board. The main objectives and contributions of the work are summarized as follows: A model is proposed to obtain the accurate energy estimation results based on the linear correlation between the performance monitoring counters (PMCs) and energy consumption. the uniqueness of the appropriate PMCs for each different system, the modeling methodology is improved to obtain stable accuracies with slight variations among multiple scenarios and to be repeatable in other systems. It includes two steps: the former, the PMC-filter, to identify the most proper set among the available PMCs of a system and the latter, the k-fold cross validation method, to avoid the bias during the model training stage. The methodology is implemented on a commercial embedded board running the 2.6.34 Linux kernel and the PAPI, a cross-platform interface to configure and access PMCs. The results show that the methodology is able to keep a good stability in different scenarios and provide robust estimation results with the average relative error being less than 5%. Este trabajo fin de m��ster, cuya investigaci��n se ha desarrollado en el Grupo de Dise��o Electr��nico y Microelectr��nico (GDEM) en el marco del proyecto PccMuTe, se centra en el desarrollo de un modelo de estimaci��n de energ��a para un sistema empotrado alimentado por bater��a. Los objetivos principales y las contribuciones de esta tesis se resumen como sigue: Se propone un modelo para obtener estimaciones precisas del consumo de energ��a de un sistema empotrado. El modelo se basa en la correlaci��n lineal entre los valores de los contadores de prestaciones y el consumo de energ��a. Considerando la particularidad de los contadores de prestaciones en cada sistema, la metodolog��a de modelado se ha mejorado para obtener precisiones estables, con ligeras variaciones entre escenarios m��ltiples y para replicar los resultados en diferentes sistemas. La metodolog��a incluye dos etapas: la primera, filtrado-PMC, que consiste en identificar el conjunto m��s apropiado de contadores de prestaciones de entre los disponibles en un sistema y la segunda, el m��todo de validaci��n cruzada de K iteraciones, cuyo fin es evitar los sesgos durante la fase de entrenamiento. La metodolog��a se implementa en un sistema empotrado que ejecuta el kernel 2.6.34 de Linux y PAPI, un interfaz multiplataforma para configurar y acceder a los contadores. Los resultados muestran que esta metodolog��a consigue una buena estabilidad en diferentes escenarios y proporciona unos resultados robustos de estimaci��n con un error medio relativo inferior al 5%.

Development of Embedded Linux Applications Using ZedBoard

The purpose of this document is to create a modest integration guide for embedding a Linux Operating System on ZedBoard development platform, based on Xilinx���s Zynq-7000 All Programmable System on Chip which contains a dual core ARM Cortex-A9 and a 7 Series FPGA Artix-7. The integration process has been structured in four chapters according to the logic generation of the different parts that compose the embedded system. With the intention of automating the generation process of a complete Linux distribution specific for ZedBoard platform, BuildRoot development platform it is used. Once the embedding process finished, it was decided to add to the system the required functionalities for adding support for IEEE1588 Standard for Precision Clock Synchronization Protocol for Networked Measurement and Control Systems, through a user space Linux program which implements the protocol. That PTP user space implementation program has been cross-compiled, executed on target and tested for evaluating the functionalities added. RESUMEN El prop��sito de este documento es crear una modesta gu��a de integraci��n de un sistema operativo Linux para la plataforma de desarrollo ZedBoard, basada en un System on Chip del fabricante Xilinx llamado Zynq-7000. Este System on Chip est�� compuesto por un procesador de doble n��cleo ARM Cortex-A9 y una FPGA de la Serie 7 equiparable a una Artix-7. El proceso de integraci��n se ha estructurado en cuatro grandes cap��tulos que se rigen seg��n el orden l��gico de generaci��n de las distintas partes por las que el sistema empotrado est�� compuesto. Con el ��nimo de automatizar el proceso de creaci��n de una distribuci��n de Linux espec��fica para la plataforma ZedBoard, se ha utilizado la plataforma de desarrollo BuildRoot. Una vez terminado el proceso de integraci��n del sistema empotrado, se procedi�� a dar dotar al sistema de las funcionalidades necesarias para dar soporte al est��ndar de sincronizaci��n de relojes en redes de ��rea local, PTP IEEE1588, a trav��s de una implementaci��n del mismo en un programa de lado de usuario el cual ha sido compilado, ejecutado y testeado para evaluar el correcto funcionamiento de las funcionalidades a��adidas.

Free-form optical systems for nonimaging applications : Sistemas ��pticos anam��rficos para aplicaciones anid��licas

La ��ptica anid��lica es una rama de la ��ptica cuyo desarrollo comenz�� a mediados de la d��cada de 1960. Este relativamente nuevo campo de la ��ptica se centra en la transferencia eficiente de la luz, algo necesario en muchas aplicaciones, entre las que destacamos los concentradores solares y los sistemas de iluminaci��n. Las soluciones de la ��ptica cl��sica a los problemas de la transferencia de energ��a de la luz s��lo son adecuadas cuando los rayos de luz son paraxiales. La condici��n paraxial no se cumple en la mayor��a de las aplicaciones para concentraci��n e iluminaci��n. Esta tesis contiene varios dise��os free-form (aquellos que no presentan ninguna simetr��a, ni de rotaci��n ni lineal) cuyas aplicaciones van destinadas a estos dos campos. El t��rmino nonimaging viene del hecho de que estos sistemas ��pticos no necesitan formar una imagen del objeto, aunque no formar la imagen no es una condici��n necesaria. Otra palabra que se utiliza a veces en lugar de nonimaging es la palabra anid��lico, viene del griego "an+eidolon" y tiene el mismo significado. La mayor��a de los sistemas ��pticos dise��ados para aplicaciones anid��licas no presentan ninguna simetr��a, es decir, son free-form (anam��rficos). Los sistemas ��pticos free-form est��n siendo especialmente relevantes durante los ��ltimos a��os gracias al desarrollo de las herramientas para su fabricaci��n como m��quinas de moldeo por inyecci��n y el mecanizado multieje. Sin embargo, solo recientemente se han desarrollado t��cnicas de dise��o anid��licas capaces de cumplir con estos grados de libertad. En aplicaciones de iluminaci��n el m��todo SMS3D permite dise��ar dos superficies free-form para controlar las fuentes de luz extensas. En los casos en que se requiere una elevada asimetr��a de la fuente, el objeto o las restricciones volum��tricos, las superficies free-form permiten obtener soluciones de mayor eficiencia, o disponer de menos elementos en comparaci��n con las soluciones de simetr��a de rotaci��n, dado que las superficies free-form tienen m��s grados de libertad y pueden realizar m��ltiples funciones debido a su naturaleza anam��rfica. Los concentradores anid��licos son muy adecuados para la captaci��n de energ��a solar, ya que el objetivo no es la reproducci��n de una imagen exacta del sol, sino sencillamente la captura de su energ��a. En este momento, el campo de la concentraci��n fotovoltaica (CPV) tiende hacia sistemas de alta concentraci��n con el fin de compensar el gasto de las c��lulas solares multi-uni��n (MJ) utilizadas como receptores, reduciendo su ��rea. El inter��s en el uso de c��lulas MJ radica en su alta eficiencia de conversi��n. Para obtener sistemas competitivos en aplicaciones terrestres se recurre a sistemas fotovoltaicos de alta concentraci��n (HCPV), con factores de concentraci��n geom��trica por encima de 500x. Estos sistemas se componen de dos (o m��s) elementos ��pticos (espejos y/o lentes). En los sistemas presentados a lo largo de este trabajo se presentan ejemplos de concentradores HCPV con elementos reflexivos como etapa primaria, as�� como concentradores con elementos refractivos (lente de Fresnel). Con la necesidad de aumentar la eficiencia de los sistemas HCPV reales y con el fin de proporcionar la divisi��n m��s eficiente del espectro solar, c��lulas conteniendo cuatro o m��s uniones (con un potencial de alcanzar eficiencias de m��s del 45% a una concentraci��n de cientos de soles) se exploran hoy en d��a. En esta tesis se presenta una de las posibles arquitecturas de divisi��n del espectro (spectrum-splitting en la literatura anglosajona) que utilizan c��lulas de concentraci��n comercial. Otro campo de aplicaci��n de la ��ptica nonimaging es la iluminaci��n, donde es necesario proporcionar un patr��n de distribuci��n de la iluminaci��n espec��fico. La iluminaci��n de estado s��lido (SSL), basada en la electroluminiscencia de materiales semiconductores, est�� proporcionando fuentes de luz para aplicaciones de iluminaci��n general. En la ��ltima d��cada, los diodos emisores de luz (LED) de alto brillo han comenzado a reemplazar a las fuentes de luz convencionales debido a la superioridad en la calidad de la luz emitida, elevado tiempo de vida, compacidad y ahorro de energ��a. Los colimadores utilizados con LEDs deben cumplir con requisitos tales como tener una alta eficiencia, un alto control del haz de luz, una mezcla de color espacial y una gran compacidad. Presentamos un colimador de luz free-form con microestructuras capaz de conseguir buena colimaci��n y buena mezcla de colores con una fuente de LED RGGB. Una buena mezcla de luz es importante no s��lo para simplificar el dise��o ��ptico de la luminaria sino tambi��n para evitar hacer binning de los chips. La mezcla de luz ��ptica puede reducir los costes al evitar la modulaci��n por ancho de pulso y otras soluciones electr��nicas patentadas para regulaci��n y ajuste de color. Esta tesis consta de cuatro cap��tulos. Los cap��tulos que contienen la obra original de esta tesis son precedidos por un cap��tulo introductorio donde se presentan los conceptos y definiciones b��sicas de la ��ptica geom��trica y en el cual se engloba la ��ptica nonimaging. Contiene principios de la ��ptica no formadora de imagen junto con la descripci��n de sus problemas y m��todos de dise��o. Asimismo se describe el m��todo de Superficies M��ltiples Simult��neas (SMS), que destaca por su versatilidad y capacidad de controlar varios haces de rayos. Adicionalmente tambi��n se describe la integraci��n K��hler y sus aplicaciones en el campo de la energ��a fotovoltaica. La concentraci��n fotovoltaica y la iluminaci��n de estado s��lido son introducidas junto con la revisi��n de su estado actual. El Segundo y Tercer Cap��tulo contienen dise��os ��pticos avanzados con aplicaci��n en la concentraci��n solar principalmente, mientras que el Cuarto Cap��tulo describe el colimador free-form con surcos que presenta buena mezcla de colores para aplicaciones de iluminaci��n. El Segundo Cap��tulo describe dos concentradores ��pticos HCPV dise��ados con el m��todo SMS en tres dimensiones (SMS3D) que llevan a cabo integraci��n K��hler en dos direcciones con el fin de proporcionar una distribuci��n de irradiancia uniforme libre de aberraciones crom��ticas sobre la c��lula solar. Uno de los dise��os es el concentrador XXR free-form dise��ado con el m��todo SMS3D, donde el espejo primario (X) y la lente secundaria (R) se dividen en cuatro sectores sim��tricos y llevan a cabo la integraci��n K��hler (proporcionando cuatro unidades del array K��hler), mientras que el espejo intermedio (X) presenta simetr��a rotacional. Otro concentrador HCPV presentado es el Fresnel-RXI (FRXI) con una lente de Fresnel funcionando como elemento primario (POE) y una lente RXI como elemento ��ptico secundario (SOE), que presenta configuraci��n 4-fold con el fin de realizar la integraci��n K��hler. Las lentes RXI son dispositivos nonimaging conocidos, pero su aplicaci��n como elemento secundario es novedosa. Los concentradores XXR y FRXI K��hler son ejemplos acad��micos de muy alta concentraci��n (m��s de 2,000x, mientras que los sistemas convencionales hoy en d��a no suelen llegar a 1,000x) preparados para las c��lulas solares N-uni��n (con N>3), que probablemente requerir��n una mayor concentraci��n y alta uniformidad espectral de irradiancia con el fin de obtener sistemas CPV terrestres eficientes y rentables. Ambos concentradores est��n dise��ados maximizando funciones de m��rito como la eficiencia ��ptica, el producto concentraci��n-aceptancia (CAP) y la uniformidad de irradiancia sobre la c��lula libre de la aberraci��n crom��tica (integraci��n K��hler). El Tercer Cap��tulo presenta una arquitectura para la divisi��n del espectro solar basada en un m��dulo HCPV con alta concentraci��n (500x) y ��ngulo de aceptancia alto (���>���1��) que tiene por objeto reducir ambas fuentes de p��rdidas de las c��lulas triple uni��n (3J) comerciales: el uso eficiente del espectro solar y la luz reflejada de los contactos met��licos y de la superficie de semiconductor. El m��dulo para la divisi��n del espectro utiliza el espectro solar m��s eficiente debido a la combinaci��n de una alta eficiencia de una c��lula de concentraci��n 3J (GaInP/GaInAs/Ge) y una de contacto posterior (BPC) de concentraci��n de silicio (Si), as�� como la t��cnica de confinamiento externo para la recuperaci��n de la luz reflejada por la c��lula 3J con el fin de ser reabsorbida por la c��lula. En la arquitectura propuesta, la c��lula 3J opera con su ganancia de corriente optimizada (concentraci��n geom��trica de 500x), mientras que la c��lula de silicio trabaja cerca de su ��ptimo tambi��n (135x). El m��dulo de spectrum-splitting consta de una lente de Fresnel plana como POE y un concentrador RXI free-form como SOE con un filtro paso-banda integrado en ��l. Tanto POE como SOE realizan la integraci��n K��hler para producir homogeneizaci��n de luz sobre la c��lula. El filtro paso banda env��a los fotones IR en la banda 900-1,150nm a la c��lula de silicio. Hay varios aspectos pr��cticos de la arquitectura del m��dulo presentado que ayudan a reducir la complejidad de los sistemas spectrum-splitting (el filtro y el secundario forman una sola pieza s��lida, ambas c��lulas son coplanarias simplific��ndose el cableado y la disipaci��n de calor, etc.). Prototipos prueba-de-concepto han sido ensamblados y probados a fin de demostrar la fabricabilidad del filtro y su rendimiento cuando se combina con la t��cnica de reciclaje de luz externa. Los resultados obtenidos se ajustan bastante bien a los modelos y a las simulaciones e invitan al desarrollo de una versi��n m��s compleja de este prototipo en el futuro. Dos colimadores s��lidos con surcos free-form se presentan en el Cuarto Cap��tulo. Ambos dise��os ��pticos est��n dise��ados originalmente usando el m��todo SMS3D. La segunda superficie ��pticamente activa est�� dise��ada a posteriori como una superficie con surcos. El dise��o inicial de dos espejos (XX) est�� dise��ado como prueba de concepto. En segundo lugar, el dise��o RXI free-form es comparable con los colimadores RXI existentes. Se trata de un dise��o muy compacto y eficiente que proporciona una muy buena mezcla de colores cuando funciona con LEDs RGB fuera del eje ��ptico como en los RGB LEDs convencionales. Estos dos dise��os son dispositivos free-form dise��ados con la intenci��n de mejorar las propiedades de mezcla de colores de los dispositivos no aplan��ticos RXI con simetr��a de revoluci��n y la eficiencia de los aplan��ticos, logrando una buena colimaci��n y una buena mezcla de colores. La capacidad de mezcla de colores del dispositivo no-aplan��tico mejora a��adiendo caracter��sticas de un aplan��tico a su hom��logo sim��trico sin p��rdida de eficiencia. En el caso del dise��o basado en RXI, su gran ventaja consiste en su menor coste de fabricaci��n ya que el proceso de metalizaci��n puede evitarse. Aunque algunos de los componentes presentan formas muy complejas, los costes de fabricaci��n son relativamente insensibles a la complejidad del molde, especialmente en el caso de la producci��n en masa (tales como inyecci��n de pl��stico), ya que el coste del molde se reparte entre todas las piezas fabricadas. Por ��ltimo, las ��ltimas dos secciones son las conclusiones y futuras l��neas de investigaci��n. ABSTRACT Nonimaging optics is a branch of optics whose development began in the mid-1960s. This rather new field of optics focuses on the efficient light transfer necessary in many applications, among which we highlight solar concentrators and illumination systems. The classical optics solutions to the problems of light energy transfer are only appropriate when the light rays are paraxial. The paraxial condition is not met in most applications for the concentration and illumination. This thesis explores several free-form designs (with neither rotational nor linear symmetry) whose applications are intended to cover the above mentioned areas and more. The term nonimaging comes from the fact that these optical systems do not need to form an image of the object, although it is not a necessary condition not to form an image. Another word sometimes used instead of nonimaging is anidolic, and it comes from the Greek ���an+eidolon��� and has the same meaning. Most of the optical systems designed for nonimaging applications are without any symmetry, i.e. free-form. Free-form optical systems become especially relevant lately with the evolution of free-form tooling (injection molding machines, multi-axis machining techniques, etc.). Nevertheless, only recently there are nonimaging design techniques that are able to meet these degrees of freedom. In illumination applications, the SMS3D method allows designing two free-form surfaces to control very well extended sources. In cases when source, target or volumetric constrains have very asymmetric requirements free-form surfaces are offering solutions with higher efficiency or with fewer elements in comparison with rotationally symmetric solutions, as free-forms have more degrees of freedom and they can perform multiple functions due to their free-form nature. Anidolic concentrators are well suited for the collection of solar energy, because the goal is not the reproduction of an exact image of the sun, but instead the collection of its energy. At this time, Concentration Photovoltaics (CPV) field is turning to high concentration systems in order to compensate the expense of multi-junction (MJ) solar cells used as receivers by reducing its area. Interest in the use of MJ cells lies in their very high conversion efficiency. High Concentration Photovoltaic systems (HCPV) with geometric concentration of more than 500x are required in order to have competitive systems in terrestrial applications. These systems comprise two (or more) optical elements, mirrors and/or lenses. Systems presented in this thesis encompass both main types of HCPV architectures: concentrators with primary reflective element and concentrators with primary refractive element (Fresnel lens). Demand for the efficiency increase of the actual HCPV systems as well as feasible more efficient partitioning of the solar spectrum, leads to exploration of four or more junction solar cells or submodules. They have a potential of reaching over 45% efficiency at concentration of hundreds of suns. One possible architectures of spectrum splitting module using commercial concentration cells is presented in this thesis. Another field of application of nonimaging optics is illumination, where a specific illuminance distribution pattern is required. The Solid State Lighting (SSL) based on semiconductor electroluminescence provides light sources for general illumination applications. In the last decade high-brightness Light Emitting Diodes (LEDs) started replacing conventional light sources due to their superior output light quality, unsurpassed lifetime, compactness and energy savings. Collimators used with LEDs have to meet requirements like high efficiency, high beam control, color and position mixing, as well as a high compactness. We present a free-form collimator with microstructures that performs good collimation and good color mixing with RGGB LED source. Good light mixing is important not only for simplifying luminaire optical design but also for avoiding die binning. Optical light mixing may reduce costs by avoiding pulse-width modulation and other patented electronic solutions for dimming and color tuning. This thesis comprises four chapters. Chapters containing the original work of this thesis are preceded by the introductory chapter that addresses basic concepts and definitions of geometrical optics on which nonimaging is developed. It contains fundamentals of nonimaging optics together with the description of its design problems, principles and methods, and with the Simultaneous Multiple Surface (SMS) method standing out for its versatility and ability to control several bundles of rays. K��hler integration and its applications in the field of photovoltaics are described as well. CPV and SSL fields are introduced together with the review on their background and their current status. Chapter 2 and Chapter 3 contain advanced optical designs with primarily application in solar concentration; meanwhile Chapter 4 portrays the free-form V-groove collimator with good color mixing property for illumination application. Chapter 2 describes two HCPV optical concentrators designed with the SMS method in three dimensions (SMS3D). Both concentrators represent K��hler integrator arrays that provide uniform irradiance distribution free from chromatic aberrations on the solar cell. One of the systems is the XXR free-form concentrator designed with the SMS3D method. The primary mirror (X) of this concentrator and secondary lens (R) are divided in four symmetric sectors (folds) that perform K��hler integration; meanwhile the intermediate mirror (X) is rotationally symmetric. Second HCPV concentrator is the Fresnel-RXI (FRXI) with flat Fresnel lens as the Primary Optical Element (POE) and an RXI lens as the Secondary Optical Element (SOE). This architecture manifests 4-fold configuration for performing K��hler integration (4 array units), as well. The RXI lenses are well-known nonimaging devices, but their application as SOE is novel. Both XXR and FRXI K��hler HCPV concentrators are academic examples of very high concentration (more than 2,000x meanwhile conventional systems nowadays have up to 1,000x) prepared for the near future N-junction (N>3) solar cells. In order to have efficient and cost-effective terrestrial CPV systems, those cells will probably require higher concentrations and high spectral irradiance uniformity. Both concentrators are designed by maximizing merit functions: the optical efficiency, concentration-acceptance angle (CAP) and cell-irradiance uniformity free from chromatic aberrations (K��hler integration). Chapter 3 presents the spectrum splitting architecture based on a HCPV module with high concentration (500x) and high acceptance angle (���>���1��). This module aims to reduce both sources of losses of the actual commercial triple-junction (3J) solar cells with more efficient use of the solar spectrum and with recovering the light reflected from the 3J cells��� grid lines and semiconductor surface. The solar spectrum is used more efficiently due to the combination of a high efficiency 3J concentration cell (GaInP/GaInAs/Ge) and external Back-Point-Contact (BPC) concentration silicon (Si) cell. By employing external confinement techniques, the 3J cell���s reflections are recovered in order to be re-absorbed by the cell. In the proposed concentrator architecture, the 3J cell operates at its optimized current gain (at geometrical concentration of 500x), while the Si cell works near its optimum, as well (135x). The spectrum splitting module consists of a flat Fresnel lens (as the POE), and a free-form RXI-type concentrator with a band-pass filter embedded in it (as the SOE), both POE and SOE performing K��hler integration to produce light homogenization. The band-pass filter sends the IR photons in the 900-1,150nm band to the Si cell. There are several practical aspects of presented module architecture that help reducing the added complexity of the beam splitting systems: the filter and secondary are forming a single solid piece, both cells are coplanar so the heat management and wiring is simplified, etc. Two proof-of-concept prototypes are assembled and tested in order to prove filter manufacturability and performance, as well as the potential of external light recycling technique. Obtained measurement results agree quite well with models and simulations, and show an opened path to manufacturing of the Fresnel RXI-type secondary concentrator with spectrum splitting strategy. Two free-form solid V-groove collimators are presented in Chapter 4. Both free-form collimators are originally designed with the SMS3D method. The second mirrored optically active surface is converted in a grooved surface a posteriori. Initial two mirror (XX) design is presented as a proof-of-concept. Second, RXI free-form design is comparable with existing RXI collimators as it is a highly compact and a highly efficient design. It performs very good color mixing of the RGGB LED sources placed off-axis like in conventional RGB LEDs. Collimators described here improve color mixing property of the prior art rotationally symmetric no-aplanatic RXI devices, and the efficiency of the aplanatic ones, accomplishing both good collimation and good color mixing. Free-form V-groove collimators enhance the no-aplanatic device's blending capabilities by adding aplanatic features to its symmetric counterpart with no loss in efficiency. Big advantage of the RXI design is its potentially lower manufacturing cost, since the process of metallization may be avoided. Although some components are very complicated for shaping, the manufacturing costs are relatively insensitive to the complexity of the mold especially in the case of mass production (such as plastic injection), as the cost of the mold is spread in many parts. Finally, last two sections are conclusions and future lines of investigation.

Towards��model-driven engineering for mixed-criticality systems: multiPARTES approach

Mixed criticality systems emerges as a suitable solution for dealing with the complexity, performance and costs of future embedded and dependable systems. However, this paradigm adds additional complexity to their development. This paper proposes an approach for dealing with this scenario that relies on hardware virtualization and Model-Driven Engineering (MDE). Hardware virtualization ensures isolation between subsystems with different criticality levels. MDE is intended to bridge the gap between design issues and partitioning concerns. MDE tooling will enhance the functional models by annotating partitioning and extra-functional properties. System partitioning and subsystems allocation will be generated with a high degree of automation. System configuration will be validated for ensuring that the resources assigned to a partition are sufficient for executing the allocated software components and that time requirements are met.

Modelling and Control of Stepper Motors for High Accuracy Positioning Systems Used in Radioactive Environments

Hybrid Stepper Motors are widely used in open-loop position applications. They are the choice of actuation for the collimators in the Large Hadron Collider, the largest particle accelerator at CERN. In this case the positioning requirements and the highly radioactive operating environment are unique. The latter forces both the use of long cables to connect the motors to the drives which act as transmission lines and also prevents the use of standard position sensors. However, reliable and precise operation of the collimators is critical for the machine, requiring the prevention of step loss in the motors and maintenance to be foreseen in case of mechanical degradation. In order to make the above possible, an approach is proposed for the application of an Extended Kalman Filter to a sensorless stepper motor drive, when the motor is separated from its drive by long cables. When the long cables and high frequency pulse width modulated control voltage signals are used together, the electrical signals difer greatly between the motor and drive-side of the cable. Since in the considered case only drive-side data is available, it is therefore necessary to estimate the motor-side signals. Modelling the entire cable and motor system in an Extended Kalman Filter is too computationally intensive for standard embedded real-time platforms. It is, in consequence, proposed to divide the problem into an Extended Kalman Filter, based only on the motor model, and separated motor-side signal estimators, the combination of which is less demanding computationally. The efectiveness of this approach is shown in simulation. Then its validity is experimentally demonstrated via implementation in a DSP based drive. A testbench to test its performance when driving an axis of a Large Hadron Collider collimator is presented along with the results achieved. It is shown that the proposed method is capable of achieving position and load torque estimates which allow step loss to be detected and mechanical degradation to be evaluated without the need for physical sensors. These estimation algorithms often require a precise model of the motor, but the standard electrical model used for hybrid stepper motors is limited when currents, which are high enough to produce saturation of the magnetic circuit, are present. New model extensions are proposed in order to have a more precise model of the motor independently of the current level, whilst maintaining a low computational cost. It is shown that a significant improvement in the model It is achieved with these extensions, and their computational performance is compared to study the cost of model improvement versus computation cost. The applicability of the proposed model extensions is demonstrated via their use in an Extended Kalman Filter running in real-time for closed-loop current control and mechanical state estimation. An additional problem arises from the use of stepper motors. The mechanics of the collimators can wear due to the abrupt motion and torque profiles that are applied by them when used in the standard way, i.e. stepping in open-loop. Closed-loop position control, more specifically Field Oriented Control, would allow smoother profiles, more respectful to the mechanics, to be applied but requires position feedback. As mentioned already, the use of sensors in radioactive environments is very limited for reliability reasons. Sensorless control is a known option but when the speed is very low or zero, as is the case most of the time for the motors used in the LHC collimator, the loss of observability prevents its use. In order to allow the use of position sensors without reducing the long term reliability of the whole system, the possibility to switch from closed to open loop is proposed and validated, allowing the use of closed-loop control when the position sensors function correctly and open-loop when there is a sensor failure. A different approach to deal with the switched drive working with long cables is also presented. Switched mode stepper motor drives tend to have poor performance or even fail completely when the motor is fed through a long cable due to the high oscillations in the drive-side current. The design of a stepper motor output fillter which solves this problem is thus proposed. A two stage filter, one devoted to dealing with the diferential mode and the other with the common mode, is designed and validated experimentally. With this ?lter the drive performance is greatly improved, achieving a positioning repeatability even better than with the drive working without a long cable, the radiated emissions are reduced and the overvoltages at the motor terminals are eliminated.

Caracterizaci��n de Sistemas intensivos en Software desde un punto de vista de innovaci��n=Characterizing Software-intensive Systems from the innovation point of view

La innovaci��n en Sistemas Intesivos en Software est�� alcanzando relevancia por m��ltiples razones: el software est�� presente en sectores como autom��vil, tel��fonos m��viles o salud. Las empresas necesitan conocer aquellos factores que afectan a la innovaci��n para incrementar las probabilidades de ��xito en el desarrollo de sus productos y, la evaluaci��n de productos sofware es un mecanismo potente para capturar este conocimiento. En consecuencia, las empresas necesitan evaluar sus productos desde la perpectiva de innovaci��n para reducir la distancia entre los productos desarrollados y el mercado. Esto es incluso m��s relevante en el caso de los productos intensivos en software, donde el tiempo real, la oportunidad, complejidad, interoperabilidad, capacidad de respuesta y compartci��n de recursos son caracter��sticas cr��ticas de los nuevos sistemas. La evaluaci��n de la innovaci��n de productos ya ha sido estudiada y se han definido algunos esquemas de evaluaci��n pero no son espec��ficos para Sistemas intensivos en Sofwtare; adem��s, no se ha alcanzado consenso en los factores ni el procedimiento de evaluaci��n. Por lo tanto, tiene sentido trabajar en la definici��n de un marco de evaluaci��n de innovaci��n enfocado a Sistemas intesivos en Software. Esta tesis identifica los elementos necesarios para construir in marco para la evaluaci��n de de Sistemas intensivos en Software desde el punto de vista de la innovaci��n. Se han identificado dos componentes como partes del marco de evaluaci��n: un modelo de referencia y una herramienta adaptativa y personalizable para la realizaci��n de la evaluaci��n y posicionamiento de la innovaci��n. El modelo de referencia est�� compuesto por cuatro elementos principales que caracterizan la evaluaci��n de innovaci��n de productos: los conceptos, modelos de innovaci��n, cuestionarios de evaluaci��n y la evaluaci��n de productos. El modelo de referencia aporta las bases para definir instancias de los modelos de evaluaci��n de innovaci��n de productos que pueden se evaluados y posicionados en la herramienta a trav��s de cuestionarios y que de forma automatizada aporta los resultados de la evaluaci��n y el posicionamiento respecto a la innovaci��n de producto. El modelo de referencia ha sido rigurosamente construido aplicando modelado conceptual e integraci��n de vistas junto con la aplicaci��n de m��todos cualitativos de investigaci��n. La herramienta ha sido utilizada para evaluar productos como Skype a trav��s de la instanciaci��n del modelo de referencia. ABSTRACT Innovation in Software intensive Systems is becoming relevant for several reasons: software is present embedded in many sectors like automotive, robotics, mobile phones or heath care. Firms need to have knowledge about factors affecting the innovation to increase the probability of success in their product development and the assessment of innovation in software products is a powerful mechanism to capture this knowledge. Therefore, companies need to assess products from an innovation perspective to reduce the gap between their developed products and the market. This is even more relevant in the case of SiSs, where real time, timeliness, complexity, interoperability, reactivity, and resource sharing are critical features of a new system. Many authors have analysed product innovation assessment and some schemas have been developed but they are not specific to SiSs; in addition, there is no consensus about the factors or the procedures for performing an assessment. Therefore, it has sense to work in the definition of a customized software product innovation evaluation framework. This thesis identifies the elements needed to build a framework to assess software products from the innovation perspective. Two components have been identified as part of the framework to assess Software intensive Systems from the innovation perspective: a reference-model and an adaptive and customizable tool to perform the assessment and to position product innovation. The reference-model is composed by four main elements characterizing product innovation assessment: concepts, innovation models, assessment questionnaires and product assessment. The reference model provides the umbrella to define instances of product innovation assessment models that can be assessed and positioned through questionnaires in the proposed tool that also provides automation in the assessment and positioning of innovation. The reference-model has been rigorously built by applying conceptual modelling and view integration integrated with qualitative research methods. The tool has been used to assess products like Skype through models instantiated from the reference-model.

Energy-based Fair Queuing: Energy-centric Processor Scheduling Algorithm for Battery-limited Mobile Systems

Los dispositivos m��viles modernos disponen cada vez de m��s funcionalidad debido al r��pido avance de las tecnolog��as de las comunicaciones y computaciones m��viles. Sin embargo, la capacidad de la bater��a no ha experimentado un aumento equivalente. Por ello, la experiencia de usuario en los sistemas m��viles modernos se ve muy afectada por la vida de la bater��a, que es un factor inestable de dif��cil de control. Para abordar este problema, investigaciones anteriores han propuesto un esquema de gestion del consumo (PM) centrada en la energ��a y que proporciona una garant��a sobre la vida operativa de la bater��a mediante la gesti��n de la energ��a como un recurso de primera clase en el sistema. Como el planificador juega un papel fundamental en la administraci��n del consumo de energ��a y en la garant��a del rendimiento de las aplicaciones, esta tesis explora la optimizaci��n de la experiencia de usuario para sistemas m��viles con energ��a limitada desde la perspectiva de un planificador que tiene en cuenta el consumo de energ��a en un contexto en el que ��sta es un recurso de primera clase. En esta tesis se analiza en primer lugar los factores que contribuyen de forma general a la experiencia de usuario en un sistema m��vil. Despu��s se determinan los requisitos esenciales que afectan a la experiencia de usuario en la planificaci��n centrada en el consumo de energ��a, que son el reparto proporcional de la potencia, el cumplimiento de las restricciones temporales, y cuando sea necesario, el compromiso entre la cuota de potencia y las restricciones temporales. Para cumplir con los requisitos, el algoritmo cl��sico de fair queueing y su modelo de referencia se extienden desde los dominios de las comunicaciones y ancho de banda de CPU hacia el dominio de la energ��a, y en base a ��sto, se propone el algoritmo energy-based fair queueing (EFQ) para proporcionar una planificaci��n basada en la energ��a. El algoritmo EFQ est�� dise��ado para compartir la potencia consumida entre las tareas mediante su planificaci��n en funci��n de la energ��a consumida y de la cuota reservada. La cuota de consumo de cada tarea con restricciones temporales est�� protegida frente a diversos cambios que puedan ocurrir en el sistema. Adem��s, para dar mejor soporte a las tareas en tiempo real y multimedia, se propone un mecanismo para combinar con el algoritmo EFQ para dar preferencia en la planificaci��n durante breves intervalos de tiempo a las tareas m��s urgentes con restricciones temporales.Las propiedades del algoritmo EFQ se evaluan a trav��s del modelado de alto nivel y la simulaci��n. Los resultados de las simulaciones indican que los requisitos esenciales de la planificaci��n centrada en la energ��a pueden lograrse. El algoritmo EFQ se implementa m��s tarde en el kernel de Linux. Para evaluar las propiedades del planificador EFQ basado en Linux, se desarroll�� un banco de pruebas experimental basado en una sitema empotrado, un programa de banco de pruebas multihilo, y un conjunto de pruebas de c��digo abierto. A trav��s de experimentos espec��ficamente dise��ados, esta tesis verifica primero las propiedades de EFQ en la gesti��n de la cuota de consumo de potencia y la planificaci��n en tiempo real y, a continuaci��n, explora los beneficios potenciales de emplear la planificaci��n EFQ en la optimizaci��n de la experiencia de usuario para sistemas m��viles con energ��a limitada. Los resultados experimentales sobre la gesti��n de la cuota de energ��a muestran que EFQ es m��s eficaz que el planificador de Linux-CFS en la gesti��n de energ��a, logrando un reparto proporcional de la energ��a del sistema independientemente de en qu�� dispositivo se consume la energ��a. Los resultados experimentales en la planificaci��n en tiempo real demuestran que EFQ puede lograr de forma eficaz, flexible y robusta el cumplimiento de las restricciones temporales aunque se d�� el caso de aumento del el n��mero de tareas o del error en la estimaci��n de energ��a. Por ��ltimo, un an��lisis comparativo de los resultados experimentales sobre la optimizaci��n de la experiencia del usuario demuestra que, primero, EFQ es m��s eficaz y flexible que los algoritmos tradicionales de planificaci��n del procesador, como el que se encuentra por defecto en el planificador de Linux y, segundo, que proporciona la posibilidad de optimizar y preservar la experiencia de usuario para los sistemas m��viles con energ��a limitada. Abstract Modern mobiledevices have been becoming increasingly powerful in functionality and entertainment as the next-generation mobile computing and communication technologies are rapidly advanced. However, the battery capacity has not experienced anequivalent increase. The user experience of modern mobile systems is therefore greatly affected by the battery lifetime,which is an unstable factor that is hard to control. To address this problem, previous works proposed energy-centric power management (PM) schemes to provide strong guarantee on the battery lifetime by globally managing energy as the first-class resource in the system. As the processor scheduler plays a pivotal role in power management and application performance guarantee, this thesis explores the user experience optimization of energy-limited mobile systemsfrom the perspective of energy-centric processor scheduling in an energy-centric context. This thesis first analyzes the general contributing factors of the mobile system user experience.Then itdetermines the essential requirements on the energy-centric processor scheduling for user experience optimization, which are proportional power sharing, time-constraint compliance, and when necessary, a tradeoff between the power share and the time-constraint compliance. To meet the requirements, the classical fair queuing algorithm and its reference model are extended from the network and CPU bandwidth sharing domain to the energy sharing domain, and based on that, the energy-based fair queuing (EFQ) algorithm is proposed for performing energy-centric processor scheduling. The EFQ algorithm is designed to provide proportional power shares to tasks by scheduling the tasks based on their energy consumption and weights. The power share of each time-sensitive task is protected upon the change of the scheduling environment to guarantee a stable performance, and any instantaneous power share that is overly allocated to one time-sensitive task can be fairly re-allocated to the other tasks. In addition, to better support real-time and multimedia scheduling, certain real-time friendly mechanism is combined into the EFQ algorithm to give time-limited scheduling preference to the time-sensitive tasks. Through high-level modelling and simulation, the properties of the EFQ algorithm are evaluated. The simulation results indicate that the essential requirements of energy-centric processor scheduling can be achieved. The EFQ algorithm is later implemented in the Linux kernel. To assess the properties of the Linux-based EFQ scheduler, an experimental test-bench based on an embedded platform, a multithreading test-bench program, and an open-source benchmark suite is developed. Through specifically-designed experiments, this thesis first verifies the properties of EFQ in power share management and real-time scheduling, and then, explores the potential benefits of employing EFQ scheduling in the user experience optimization for energy-limited mobile systems. Experimental results on power share management show that EFQ is more effective than the Linux-CFS scheduler in managing power shares and it can achieve a proportional sharing of the system power regardless of on which device the energy is spent. Experimental results on real-time scheduling demonstrate that EFQ can achieve effective, flexible and robust time-constraint compliance upon the increase of energy estimation error and task number. Finally, a comparative analysis of the experimental results on user experience optimization demonstrates that EFQ is more effective and flexible than traditional processor scheduling algorithms, such as those of the default Linux scheduler, in optimizing and preserving the user experience of energy-limited mobile systems.

Iterative bit- and power allocation in correlated MIMO systems

In this contribution a novel iterative bit- and power allocation (IBPA) approach has been developed when transmitting a given bit/s/Hz data rate over a correlated frequency non-selective (4�� 4) Multiple-Input MultipleOutput (MIMO) channel. The iterative resources allocation algorithm developed in this investigation is aimed at the achievement of the minimum bit-error rate (BER) in a correlated MIMO communication system. In order to achieve this goal, the available bits are iteratively allocated in the MIMO active layers which present the minimum transmit power requirement per time slot.

Self-Learning Embedded System for Object Identification in Intelligent Infrastructure Sensors

The emergence of new horizons in the field of travel assistant management leads to the development of cutting-edge systems focused on improving the existing ones. Moreover, new opportunities are being also presented since systems trend to be more reliable and autonomous. In this paper, a self-learning embedded system for object identification based on adaptive-cooperative dynamic approaches is presented for intelligent sensor���s infrastructures. The proposed system is able to detect and identify moving objects using a dynamic decision tree. Consequently, it combines machine learning algorithms and cooperative strategies in order to make the system more adaptive to changing environments. Therefore, the proposed system may be very useful for many applications like shadow tolls since several types of vehicles may be distinguished, parking optimization systems, improved traffic conditions systems, etc.