Implementation of membrane processes for improvement of the detection of food contaminants

The EM3E Master is an Education Programme supported by the European Commission, the European Membrane Society (EMS), the European Membrane House (EMH), and a large international network of industrial companies, research centres and universities (http://www.em3e.eu)

Negative rebound and disinvestment effects in response to an improvement in energy efficiency in the UK economy

This paper uses a computable general equilibrium (CGE) framework to investigate the conditions under which rebound effects may occur in response to increases in energy efficiency in the UK national economy. Previous work for the UK has suggested that rebound effects will occur even where key elasticities of substitution in production are set close to zero. The research reported in this paper involves carrying out a systematic sensitivity analysis, where relative price sensitivity is gradually introduced into the system, focusing specifically on elasticities of substitution in production and trade parameters, in order to determine conditions under which rebound effects become a likely outcome. The main result is that, while there is positive pressure for rebound effects even where (direct and indirect) demands for energy are very price inelastic, this may be partially or wholly offset by negative income, competitiveness and disinvestment effects, which also occur in response to falling energy prices. The occurrence of disinvestment effects is of particular interest. These occur where falling energy prices reduce profitability in domestic energy supply sectors, leading to a contraction in capital stock in these sectors, which may in turn lead to rebound effects that are smaller in the long run than in the short run, a result that runs contrary to the predictions of previous theoretical work in this area.

The added value from a general equilibrium analyses of increased efficiency in household energy use

The aim of the paper is to identify the added value from using general equilibrium techniques to consider the economy-wide impacts of increased efficiency in household energy use. We take as an illustrative case study the effect of a 5% improvement in household energy efficiency on the UK economy. This impact is measured through simulations that use models that have increasing degrees of endogeneity but are calibrated on a common data set. That is to say, we calculate rebound effects for models that progress from the most basic partial equilibrium approach to a fully specified general equilibrium treatment. The size of the rebound effect on total energy use depends upon: the elasticity of substitution of energy in household consumption; the energy intensity of the different elements of household consumption demand; and the impact of changes in income, economic activity and relative prices. A general equilibrium model is required to capture these final three impacts.

Multiplex blood PCR in combination with blood cultures for improvement of microbiological documentation of infection in febrile neutropenia.

The frequent lack of microbiological documentation of infection by blood cultures (BC) has a major impact on clinical management of febrile neutropenic patients, especially in cases of unexplained persistent fever. We assessed the diagnostic utility of the LightCycler SeptiFast test (SF), a multiplex blood PCR, in febrile neutropenia. Blood for BC and SF was drawn at the onset of fever and every 3 days of persistent fever. SF results were compared with those of BC, clinical documentation of infection, and standard clinical, radiological, and microbiological criteria for invasive fungal infections (IFI). A total of 141 febrile neutropenic episodes in 86 hematological patients were studied: 44 (31%) microbiologically and 49 (35%) clinically documented infections and 48 (34%) unexplained fevers. At the onset of fever, BC detected 44 microorganisms in 35/141 (25%) episodes. Together, BC and SF identified 78 microorganisms in 61/141 (43%) episodes (P = 0.002 versus BC or SF alone): 12 were detected by BC and SF, 32 by BC only, and 34 by SF only. In 19/52 (37%) episodes of persistent fever, SF detected 28 new microorganisms (7 Gram-positive bacterial species, 15 Gram-negative bacterial species, and 6 fungal species [89% with a clinically documented site of infection]) whereas BC detected only 4 pathogens (8%) (P = 0.001). While BC did not detect fungi, SF identified 5 Candida spp. and 1 Aspergillus sp. in 5/7 probable or possible cases of IFI. Using SeptiFast PCR combined with blood cultures improves microbiological documentation in febrile neutropenia, especially when fever persists and invasive fungal infection is suspected. Technical adjustments may enhance the efficiency of this new molecular tool in this specific setting.

Improvement of the antibacterial activity of daptomycin-loaded polymeric microparticles by Eudragit RL 100: An assessment by isothermal microcalorimetry.

The aim of the present study was to develop novel daptomycin-loaded acrylic microparticles with improved release profiles and antibacterial activity against two clinically relevant methicillin-susceptible and methicillin-resistant Staphylococcus aureus strains (MSSA and MRSA, respectively). Daptomycin was encapsulated into poly(methyl methacrylate) (PMMA) and PMMA-Eudragit RL 100 (EUD) microparticles by a double emulsion-solvent evaporation method. For comparison purposes similar formulations were prepared with vancomycin. Particle morphology, size distribution, encapsulation efficiency, surface charge, physicochemical properties, in vitro release and biocompatibility were assessed. Particles exhibited a micrometer size and a spherical morphology. The addition of EUD to the formulation caused a shift in the surface charge of the particles from negative zeta potential values (100% PMMA formulations) to strongly positive. It also improved daptomycin encapsulation efficiency and release, whereas vancomycin encapsulation and release were strongly hindered. Plain and antibiotic-loaded particles presented comparable biocompatibility profiles. The antibacterial activity of the particles was assessed by isothermal microcalorimetry against both MSSA and MRSA. Daptomycin-loaded PMMA-EUD particles presented the highest antibacterial activity against both strains. The addition of 30% EUD to the daptomycin-loaded PMMA particles caused a 40- and 20-fold decrease in the minimum inhibitory (MIC) and bactericidal concentration (MBC) values, respectively, when compared to the 100% PMMA formulations. On the other hand, vancomycin-loaded microparticles presented the highest antibacterial activity in PMMA particles. Unlike conventional methods, isothermal microcalorimetry proved to be a real-time, sensitive and accurate method for assessment of antibacterial activity of antibiotic-loaded polymeric microparticles. Finally, the addition of EUD to formulations proved to be a powerful strategy to improve daptomycin encapsulation efficiency and release, and consequently improving the microparticles activity against two relevant S. aureus strains.

Performance Improvement of Centrifugal Compressor Stage with Pinched Geometry or Vaned Diffuser

Centrifugal compressors are widely used for example in refrigeration processes, the oil and gas industry, superchargers, and waste water treatment. In this work, five different vaneless diffusers and six different vaned diffusers are investigated numerically. The vaneless diffusers vary only by their diffuser width, so that four of the geometries have pinch implemented to them. Pinch means a decrease in the diffuser width. Four of the vaned diffusers have the same vane turning angle and a different number of vanes, and two have different vane turning angles. The flow solver used to solve the flow fields is Finflo, which is a Navier-Stokes solver. All the cases are modeled with the Chien's k – έ- turbulence model, and selected cases are modeled also with the k – ώ-SST turbulence model. All five vaneless diffusers and three vaned diffusers are investigated also experimentally. For each construction, the compressor operating map is measured according to relevant standards. In addition to this, the flow fields before and after the diffuser are measured with static and total pressure, flow angle and total temperature measurements. When comparing the computational results to the measured results, it is evident that the k – ώ-SST turbulence model predicts the flow fields better. The simulation results indicate that it is possible to improve the efficiency with the pinch, and according to the numerical results, the two best geometries are the ones with most pinch at the shroud. These geometries have approximately 4 percentage points higher efficiency than the unpinched vaneless diffusers. The hub pinch does not seem to have any major benefits. In general, the pinches make the flow fields before and after the diffuser more uniform. The pinch also seems to improve the impeller efficiency. This is down to two reasons. The major reason is that the pinch decreases the size of slow flow and possible backflow region located near the shroud after the impeller. Secondly, the pinches decrease the flow velocity in the tip clearance, leading to a smaller tip leakage flow and therefore slightly better impeller efficiency. Also some of the vaned diffusers improve the efficiency, the increment being 1...3 percentage points, when compared to the vaneless unpinched geometry. The measurement results confirm that the pinch is beneficial to the performance of the compressor. The flow fields are more uniform with the pinched cases, and the slow flow regions are smaller. The peak efficiency is approximately 2 percentage points and the design point efficiency approximately 4 percentage points higher with the pinched geometries than with the un- pinched geometry. According to the measurements, the two best geometries are the ones with the most pinch at the shroud, the case with the pinch only at the shroud being slightly better of the two. The vaned diffusers also have better efficiency than the vaneless unpinched geometries. However, the pinched cases have even better efficiencies. The vaned diffusers narrow the operating range considerably, whilst the pinch has no significant effect on the operating range.

Improvement of Surface Strength of Paper

Offset printing is a popular printing method that is especially suitable for large and fast print jobs. Newspapers, magazines and books are typical examples of products printed with offset method. In high volume printing production high efficiency is essential. Offset printing uses tacky inks that cause serious stress to the paper surface. Dusting and linting are terms that describe how loose and weakly bonded particles are removed from the paper surface in the printing process. The removed particles accumulate in the process causing deteriorating print quality. This forces the printing operators to stop production for washing and cleaning. Time and money are lost. Dusting and linting tendency of paper can be decreased by improving the surface strength of paper. In the present work a method to increase the surface strength of paper was studied. In the literature part offset printing method and challenges related to offset printing are presented. A review of new methods for surface sizing of paper is also presented. The experimental part presents trials where an apparatus for improving paper surface strength was tested and developed in mill scale. Laboratory work supporting the actual mill scale operations is also presented. The acquired results provide a solid base of information to make decisions on how to proceed with research in the present field of study.

Improvement of the indirect hemagglutination test for the detection of antibodies to Streptococcus pyogenes

An indirect hemagglutination test for a seroepidemiological survey of Streptococcus pyogenes infection was standardized. This is an improved modification of the indirect hemagglutination test which utilizes an unstable reagent prepared with fresh blood cells. Two types of bacterial antigens represented by extracellular products and purified streptolysin O were assayed, but only the former antigen gave good results. Pretreatment of the bacterial antigen with 0.15 M NaOH and neutralization to pH 5.5, as well as postfixation of sensitized red cells with 0.1% glutaraldehyde at 56oC for 30 min were found to be essential to give long stability to the reagent in liquid suspension, at least 9 months at 4oC. A total of 564 serum samples with high, moderate and low anti-streptolysin O antibodies as determined by the neutralization assay were studied by the indirect hemagglutination test using the new reagent. The sensitivity, specificity, efficiency, positive predictive value and negative predictive value of the test in relation to the neutralization assay were 0.950, 0.975, 0.963, 0.973, and 0.955, respectively. The kappa agreement index between the two techniques was high (0.926) and ranked as "almost perfect". Antibody levels detected by both techniques also presented a high positive correlation (rs = 0.726). Five reagent batches successively produced proved to be reproducible. Thus, the improved indirect hemagglutination test seems to be useful for public health laboratories.

Improvement of grapevine iron nutrition by a bovine blood-derived compound

Iron (Fe) is essential for chlorophyll formation and plant growth. Irondeficiency chlorosis is a major nutritional disorder in several fruit trees cultivated in calcareous and alkaline soils, reducing fruit yield and quality and causing heavy economic losses. Since chelated Fe, the most widespread fertilizers used for preventing or curing Fe deficiency, pose risks of environmental pollution, the development of sustainable agronomic alternatives represents a priority for the fruit industry. In this work, we investigated the effectiveness of a bovine blood-derived product (BB; 0,125% Fe) for preventing Fe-deficiency in grapevine plants. During the vegetative season 2011 potted plants of five graft combinations: Sangiovese/S4O, Cabernet Sauvignon/S4O and Cabernet Sauvignon/140 Ruggeri, 140 Ruggeri/Cabernet Sauvignon, Vitis riparia/Cabernet Sauvignon were grown on calcareous soil. Soil treatments included: 1) Control; 2) Fe-EDDHA (Fe 6%); 3) Bovine-Blood (5 g/L); 4) Bovine-Blood (20 g/L). With the exception of Cabernet Sauvignon/S4O plants, Fe-EDDHA increased SPAD units (leaf chlorophyll content). Bovine-blood at low concentrations had similar or higher SPAD units than Fe-EDDHA. Increasing concentration resulted in further increases in SPAD units only in some graft combinations. Data highlight the efficiency of Fe blood-compound in the prevention of grapevine Fe-deficiency over one growing season.

Mejora del comportamiento térmico de los morteros de cal aditivados y su empleo en la rehabilitación de inmuebles = Improvement of thermal behaviour of additived lime mortars and their use in rehabilitation of buildings

La envolvente de la edificación es la responsable de equilibrar el intercambio energético entre el interior y el exterior, por lo tanto cualquier actuación encaminada a la reducción del consumo energético ha de establecer, como uno de sus objetivos prioritarios, la mejora del comportamiento de la misma. Las edificaciones anteriores a 1940 constituyen la mayor parte de las existentes en áreas rurales y centros urbanos. En ellas, la repercusión de la fachada sobre las transmitancias globales pone de manifiesto la necesidad de intervención. Sin embargo, su elevada inercia térmica y los importantes saltos térmicos característicos de gran parte de España plantean la importancia de que aquélla se efectúe por el exterior. A tal respecto, la falta de disponibilidad de espesor suficiente para implantar sistemas tipo SATE deriva en que, frecuentemente, la única solución viable sea la de aislar por el interior perdiendo con ello la capacidad de acumulación térmica del muro y con el asociado riesgo de condensaciones. La amplia tradición en el empleo de revestimientos, especialmente en base de cal, permiten que éstos sean utilizados no sólo como elemento estético o de protección de la obra de fábrica antigua sino también para la mejora del comportamiento térmico del soporte, si se aprovecha el mecanismo de transmisión térmica por radiación. Éste es el objetivo de la presente Tesis Doctoral en la que se estudia la modificación de las propiedades radiantes de los morteros de revestimiento para la mejora de la eficiencia energética de las construcciones históricas, principalmente las constituidas por muros monolíticos, aunque podría ser de aplicación a otro tipo de construcciones compuestas por diversas capas. Como punto de partida, se estudió y revisó la documentación disponible sobre las investigaciones de las tres áreas científico-tecnológicas que convergen en la Tesis Doctoral: rehabilitación, material y comportamiento térmico, a partir de lo cual se comprobó la inexistencia de estudios similares al objeto de la presente Tesis Doctoral. Complementariamente, se analizaron los revestimientos en lo concerniente a los materiales que los constituyen, la composición de las mezclas y características de cada una de las capas así como al enfoque que, desde el punto de vista térmico, se estimaba más adecuado para la obtención de los objetivos propuestos. Basándonos en dichos análisis, se preseleccionaron ochenta materiales que fueron ensayados en términos de reflectancia y emisividad para elegir cuatro con los que se continuó la investigación. Éstos, junto con la cal elegida para la investigación y el árido marmóreo característico de la última capa de revestimiento, fueron caracterizados térmicamente, de forma pormenorizada, así como química y físicamente. Los fundamentos teóricos y los estudios preliminares desarrollados con distintos materiales, en estado fresco y endurecido, fueron empleados en la dosificación de componentes de las mezclas, en dos proporciones distintas, para el estudio del efecto del agregado. Éstas se ensayaron en estado fresco, para comprobar su adecuación de puesta en obra y prever su VI adherencia al soporte, así como en estado endurecido a 28 y 90 días de curado, para conocer las propiedades que permitieran prever su compatibilidad con aquél y estimar el alcance de la reducción de transferencias térmicas lograda. Además, se estudiaron las características generales de las mezclas que sirvieron para establecer correlaciones entre distintas propiedades y entender los resultados mecánicos, físicos (comportamiento frente al agua) y energéticos. Del estudio conjunto de las distintas propiedades analizadas se propusieron dos mezclas, una blanca y otra coloreada, cuyas características permiten garantizar la compatibilidad con la obra de fábrica antigua, desde el punto de vista físico y mecánico, y preservar la autenticidad de los revestimientos, en cuanto a la técnica de aplicación tradicional en sistemas multicapa. El comportamiento térmico de las mismas, sobre una obra de fábrica de 40 cm de espesor, se estimó, en estado estacionario y pseudo-transitorio, demostrándose reducciones del flujo térmico entre 16-48%, en condiciones de verano, y entre el 6-11%, en invierno, en función de la coloración y de la rugosidad de la superficie, en comparación con el empleo de la mezcla tradicional. Por lo que, se constata la viabilidad de los materiales compuestos propuestos y su adecuación al objetivo de la investigación. VII ABSTRACT The envelope is responsible for balancing the energy exchange between the inside and outside in buildings. For this reason, any action aimed at reducing energy consumption must establish, as one of its key priorities, its improvement. In rural areas and urban centers, most of the constructions were built before 1940. In them, the impact of the façade on the global transmittance highlights the need for intervention. However, its high thermal inertia and fluctuation of temperatures in the majority of Spain bring up that it should be placed outside the insulation. In this regard, the lack of availability of enough thickness to implement systems such as ETICS results in that often the only viable solution is to isolate the interior, losing thereby the wall’s heat storage capacity with the associated risk of condensation. The tradition in the use of renders, especially lime-based, allows us to use them not only as an aesthetic element or to protect the ancient masonry, but also for improved thermal performance of the support by taking advantage of the heat transfer mechanism by radiation. This is the aim of this Doctoral Thesis in which the modification of the radiative properties of lime mortars for renders to improve the energy efficiency of historic buildings, mainly composed of monolithic walls, is studied, although it could be applied to other structures composed of several layers. As a starting point, the available literature in the three scientific-technological areas that converge at the Doctoral Thesis: rehabilitation, material and thermal behaviour, was reviewed, and confirmed the absence of researches similar to this Doctoral Thesis. Additionally, the renders were studied with regard to the materials that constitute them, the composition of the mixtures and the characteristics of each layer, as well as to the approach which, from a thermal point of view, was deemed the most suitable for achieving the objectives sets. Based on thre aforementioned analysis, eighty materials tested in terms of reflectance and emissivity were pre-selected, to choose four with which the research was continued. Common marble sand, used in the last layer of the renders, together with the appointed materials and hydrated lime were characterized thermally, in detail, as well as chemically and physically. The theoretical bases and preliminary studies with different materials, in fresh and hardened state, were used in the dosage of the composition of the mixtures. In order to study their effect they were used in two different proportions, that is, ten mixtures in total. These were tested in their fresh state to evaluate their setting-up suitability and foresee their adhesion to the support, as well as in their hardened state, at 28 and 90 days of curing, to establish the properties which enabled us to anticipate their compatibility with the old masonry walls and estimate the scope of the reduction of heat transfers achieved. In addition, the general characteristics of the mixtures used to establish correlations and to understand the mechanical, physical and energy results were studied. Two mixtures, one white and one colored, were proposed as the result of the different properties analysed, whose characteristics allow the guarantee of mechanical and physical compatibility VIII with the old masonry and preserve the authenticity of the renders. The thermal behavior of both, applied on a masonry wall 40 cm thick, was estimated at a steady and pseudo-transient state, with heat flow reductions between 16-48% during summertime and 6-11% during wintertime, depending on the color and surface roughness, compared to the use of the traditional mixture. So, the viability of the proposed composite materials and their fitness to the aim of the research are established.

Contribution to the quality improvement of the antenna measurement using post-processing techniques = Contribución a la mejora de la calidad de medida de antena usando técnicas de post-procesado

One important task in the design of an antenna is to carry out an analysis to find out the characteristics of the antenna that best fulfills the specifications fixed by the application. After that, a prototype is manufactured and the next stage in design process is to check if the radiation pattern differs from the designed one. Besides the radiation pattern, other radiation parameters like directivity, gain, impedance, beamwidth, efficiency, polarization, etc. must be also evaluated. For this purpose, accurate antenna measurement techniques are needed in order to know exactly the actual electromagnetic behavior of the antenna under test. Due to this fact, most of the measurements are performed in anechoic chambers, which are closed areas, normally shielded, covered by electromagnetic absorbing material, that simulate free space propagation conditions, due to the absorption of the radiation absorbing material. Moreover, these facilities can be employed independently of the weather conditions and allow measurements free from interferences. Despite all the advantages of the anechoic chambers, the results obtained both from far-field measurements and near-field measurements are inevitably affected by errors. Thus, the main objective of this Thesis is to propose algorithms to improve the quality of the results obtained in antenna measurements by using post-processing techniques and without requiring additional measurements. First, a deep revision work of the state of the art has been made in order to give a general vision of the possibilities to characterize or to reduce the effects of errors in antenna measurements. Later, new methods to reduce the unwanted effects of four of the most commons errors in antenna measurements are described and theoretical and numerically validated. The basis of all them is the same, to perform a transformation from the measurement surface to another domain where there is enough information to easily remove the contribution of the errors. The four errors analyzed are noise, reflections, truncation errors and leakage and the tools used to suppress them are mainly source reconstruction techniques, spatial and modal filtering and iterative algorithms to extrapolate functions. Therefore, the main idea of all the methods is to modify the classical near-field-to-far-field transformations by including additional steps with which errors can be greatly suppressed. Moreover, the proposed methods are not computationally complex and, because they are applied in post-processing, additional measurements are not required. The noise is the most widely studied error in this Thesis, proposing a total of three alternatives to filter out an important noise contribution before obtaining the far-field pattern. The first one is based on a modal filtering. The second alternative uses a source reconstruction technique to obtain the extreme near-field where it is possible to apply a spatial filtering. The last one is to back-propagate the measured field to a surface with the same geometry than the measurement surface but closer to the AUT and then to apply also a spatial filtering. All the alternatives are analyzed in the three most common near-field systems, including comprehensive noise statistical analyses in order to deduce the signal-to-noise ratio improvement achieved in each case. The method to suppress reflections in antenna measurements is also based on a source reconstruction technique and the main idea is to reconstruct the field over a surface larger than the antenna aperture in order to be able to identify and later suppress the virtual sources related to the reflective waves. The truncation error presents in the results obtained from planar, cylindrical and partial spherical near-field measurements is the third error analyzed in this Thesis. The method to reduce this error is based on an iterative algorithm to extrapolate the reliable region of the far-field pattern from the knowledge of the field distribution on the AUT plane. The proper termination point of this iterative algorithm as well as other critical aspects of the method are also studied. The last part of this work is dedicated to the detection and suppression of the two most common leakage sources in antenna measurements. A first method tries to estimate the leakage bias constant added by the receiver’s quadrature detector to every near-field data and then suppress its effect on the far-field pattern. The second method can be divided into two parts; the first one to find the position of the faulty component that radiates or receives unwanted radiation, making easier its identification within the measurement environment and its later substitution; and the second part of this method is able to computationally remove the leakage effect without requiring the substitution of the faulty component. Resumen Una tarea importante en el diseño de una antena es llevar a cabo un análisis para averiguar las características de la antena que mejor cumple las especificaciones fijadas por la aplicación. Después de esto, se fabrica un prototipo de la antena y el siguiente paso en el proceso de diseño es comprobar si el patrón de radiación difiere del diseñado. Además del patrón de radiación, otros parámetros de radiación como la directividad, la ganancia, impedancia, ancho de haz, eficiencia, polarización, etc. deben ser también evaluados. Para lograr este propósito, se necesitan técnicas de medida de antenas muy precisas con el fin de saber exactamente el comportamiento electromagnético real de la antena bajo prueba. Debido a esto, la mayoría de las medidas se realizan en cámaras anecoicas, que son áreas cerradas, normalmente revestidas, cubiertas con material absorbente electromagnético. Además, estas instalaciones se pueden emplear independientemente de las condiciones climatológicas y permiten realizar medidas libres de interferencias. A pesar de todas las ventajas de las cámaras anecoicas, los resultados obtenidos tanto en medidas en campo lejano como en medidas en campo próximo están inevitablemente afectados por errores. Así, el principal objetivo de esta Tesis es proponer algoritmos para mejorar la calidad de los resultados obtenidos en medida de antenas mediante el uso de técnicas de post-procesado. Primeramente, se ha realizado un profundo trabajo de revisión del estado del arte con el fin de dar una visión general de las posibilidades para caracterizar o reducir los efectos de errores en medida de antenas. Después, se han descrito y validado tanto teórica como numéricamente nuevos métodos para reducir el efecto indeseado de cuatro de los errores más comunes en medida de antenas. La base de todos ellos es la misma, realizar una transformación de la superficie de medida a otro dominio donde hay suficiente información para eliminar fácilmente la contribución de los errores. Los cuatro errores analizados son ruido, reflexiones, errores de truncamiento y leakage y las herramientas usadas para suprimirlos son principalmente técnicas de reconstrucción de fuentes, filtrado espacial y modal y algoritmos iterativos para extrapolar funciones. Por lo tanto, la principal idea de todos los métodos es modificar las transformaciones clásicas de campo cercano a campo lejano incluyendo pasos adicionales con los que los errores pueden ser enormemente suprimidos. Además, los métodos propuestos no son computacionalmente complejos y dado que se aplican en post-procesado, no se necesitan medidas adicionales. El ruido es el error más ampliamente estudiado en esta Tesis, proponiéndose un total de tres alternativas para filtrar una importante contribución de ruido antes de obtener el patrón de campo lejano. La primera está basada en un filtrado modal. La segunda alternativa usa una técnica de reconstrucción de fuentes para obtener el campo sobre el plano de la antena donde es posible aplicar un filtrado espacial. La última es propagar el campo medido a una superficie con la misma geometría que la superficie de medida pero más próxima a la antena y luego aplicar también un filtrado espacial. Todas las alternativas han sido analizadas en los sistemas de campo próximos más comunes, incluyendo detallados análisis estadísticos del ruido con el fin de deducir la mejora de la relación señal a ruido lograda en cada caso. El método para suprimir reflexiones en medida de antenas está también basado en una técnica de reconstrucción de fuentes y la principal idea es reconstruir el campo sobre una superficie mayor que la apertura de la antena con el fin de ser capaces de identificar y después suprimir fuentes virtuales relacionadas con las ondas reflejadas. El error de truncamiento que aparece en los resultados obtenidos a partir de medidas en un plano, cilindro o en la porción de una esfera es el tercer error analizado en esta Tesis. El método para reducir este error está basado en un algoritmo iterativo para extrapolar la región fiable del patrón de campo lejano a partir de información de la distribución del campo sobre el plano de la antena. Además, se ha estudiado el punto apropiado de terminación de este algoritmo iterativo así como otros aspectos críticos del método. La última parte de este trabajo está dedicado a la detección y supresión de dos de las fuentes de leakage más comunes en medida de antenas. El primer método intenta realizar una estimación de la constante de fuga del leakage añadido por el detector en cuadratura del receptor a todos los datos en campo próximo y después suprimir su efecto en el patrón de campo lejano. El segundo método se puede dividir en dos partes; la primera de ellas para encontrar la posición de elementos defectuosos que radian o reciben radiación indeseada, haciendo más fácil su identificación dentro del entorno de medida y su posterior substitución. La segunda parte del método es capaz de eliminar computacionalmente el efector del leakage sin necesidad de la substitución del elemento defectuoso.

Improvement of the Dynamic Performance of a Buck Converter using Controlled Current Source as an Additional Energy Path

This work is related to the improvement of the dynamic performance of the Buck converter by means of introducing an additional power path that virtually increase s the output capacitance during transients, thus improving the output impedance of the converter. It is well known that in VRM applications, with wide load steps, voltage overshoots and undershoots ma y lead to undesired performance of the load. To solve this problem, high-bandwidth high-switching frequency power converter s can be applied to reduce the transient time or a big output capacitor can be applied to reduce the output impedance. The first solution can degrade the efficiency by increasing switching losses of the MOSFETS, and the second solution is penalizing the cost and size of the output filter. The additional energy path, as presented here, is introduced with the Output Impedance Correction Circuit (OICC) based on the Controlled Current Source (CCS). The OICC is using CCS to inject or extract a current n - 1 times larger than the output capacitor current, thus virtually increasing n times the value of the output capacitance during the transients. This feature allows the usage of a low frequency Buck converter with smaller capacitor but satisfying the dynamic requirements.

Improvement of the Dynamic Performance of a Multiphase Current Controlled Buck Converter using an Auxiliary Synchronous Buck Converter as an Additional Energy Path

This work is related to the output impedance improvement of a Multiphase Buck converter with Peak Current Mode Control (PCMC) by means of introducing an additional power path that virtually increases the output capacitance during transients. Various solutions that can be employed to improve the dynamic behavior of the converter system exist, but nearly all solutions are developed for a Single Phase Buck converter with Voltage Mode Control (VMC), while in the VRM applications, due to the high currents, the system is usually implemented as a Multiphase Buck Converter with Current Mode Control. The additional energy path, as presented here, is introduced with the Output Impedance Correction Circuit (OICC) based on the Controlled Current Source (CCS). The OICC is used to inject or extract a current n-1 times larger than the output capacitor current, thus virtually increasing n times the value of the output capacitance during the transients. Furthermore, this work extends the OICC concept to a Multiphase Buck Converter system while comparing proposed solution with the system that has n times bigger output capacitor. In addition, the OICC is implemented as a Synchronous Buck Converter with PCMC, thus reducing its influence on the system efficiency.

New concepts and techniques for the development of high-efficiency concentrating photovoltaic modules

El interés por los sistemas fotovoltaicos de concentración (CPV) ha resurgido en los últimos años amparado por el desarrollo de células multiunión de muy alta eficiencia basadas en semiconductores de los grupos III-V. Estas células han permitido obtener módulos de concentración con eficiencias que prácticamente duplican las del panel plano y que llegan al 35% en los módulos récord. Esta tesis está dedicada al diseño y la implementación experimental de nuevos conceptos que permitan obtener módulos CPV que no sólo alcancen una eficiencia alta en condiciones estándar sino que, además, sean lo suficientemente tolerantes a errores de montaje, seguimiento, temperatura y variaciones espectrales para que la energía que producen a lo largo del año sea máxima. Una de las primeras cuestiones que se abordan es el diseño de elementos ópticos secundarios para sistemas cuyo primario es una lente de Fresnel y que permiten, para una concentración fija, aumentar el ángulo de aceptancia y la tolerancia del sistema. Varios secundarios reflexivos y refractivos han sido diseñados y analizados mediante trazado de rayos. En particular, utilizando óptica anidólica y basándose en el diseño de una sola etapa conocido como ‘concentrador dieléctrico que funciona por reflexión total interna‘, se ha diseñado, fabricado y caracterizado un secundario con salida cuadrada que, usado junto con una lente de Fresnel, permite alcanzar simultáneamente una elevada eficiencia, concentración y aceptancia. Además, se ha propuesto y prototipado un método alternativo de fabricación para otro de los secundarios, denominado domo, consistente en el sobremoldeo de silicona sobre células solares. Una de las características que impregna todo el trabajo realizado en esta tesis es la aproximación holística en el diseño de módulos CPV, es decir, se ha prestado especial atención al diseño conjunto de la célula y la óptica para garantizar que el sistema total alcance la mayor eficiencia posible. En este sentido muchos sistemas ópticos desarrollados en esta tesis han sido diseñados, caracterizados y optimizados teniendo en cuenta que el ajuste de corriente entre las distintas subcélulas que comprenden la célula multiunión bajo el concentrador sea muy próximo a uno. La capa antirreflectante sobre la célula funciona, en cierto modo, como interfaz entre la óptica y la célula, por lo que se ha diseñado un método de optimización de capas antirreflectantes que considera no sólo el amplio rango de longitudes de onda para el que las células multiunión son sensibles sino también la distribución angular de intensidad sobre la célula creada por la óptica de concentración. Además, la cuestión de la falta de uniformidad también se ha abordado mediante la comparación de las distribuciones espectrales y espaciales de irradiancia que crean diferentes ópticas (simuladas mediante trazado de rayos y fotografiadas) y las pérdidas de eficiencia que experimentan las células iluminadas por dichas ópticas de concentración medidas experimentalmente. El efecto de la temperatura en la óptica de concentración también ha sido objeto de estudio de esta tesis. En particular, mediante simulaciones de elementos finitos se han dado los primeros pasos para el análisis de las deformaciones que sufren los dientes de las lentes de Fresnel híbridas (vidrio-silicona), así como el cambio de índice de refracción con la temperatura y la influencia de ambos efectos sobre el funcionamiento de los sistemas. Se ha implementado un modelo que tiene por objeto considerar las variaciones ambientales, principalmente temperatura y contenido espectral de la radiación directa, así como las sensibilidades térmica y espectral de los sistemas CPV, con el fin de maximizar la energía producida por un módulo de concentración a lo largo de un año en un emplazamiento determinado. Los capítulos 5 y 6 de este libro están dedicados al diseño, fabricación y caracterización de un nuevo concepto de módulo fotovoltaico denominado FluidReflex y basado en una única etapa reflexiva con dieléctrico fluido. En este nuevo concepto la presencia del fluido aporta algunas ventajas significativas como son: un aumento del producto concentración por aceptancia (CAP, en sus siglas en inglés) alcanzable al rodear la célula con un medio cuyo índice de refracción es mayor que uno, una mejora de la eficiencia óptica al disminuir las pérdidas por reflexión de Fresnel en varias interfaces, una mejora de la disipación térmica ya que el calor que se concentra junto a la célula se trasmite por convección natural y conducción en el fluido y un aislamiento eléctrico mejorado. Mediante la construcción y medida de varios prototipos de unidad elemental se ha demostrado que no existe ninguna razón fundamental que impida la implementación práctica del concepto teórico alcanzando una elevada eficiencia. Se ha realizado un análisis de fluidos candidatos probando la existencia de al menos dos de ellos que cumplen todos los requisitos (en particular el de estabilidad bajo condiciones de luz concentrada) para formar parte del sistema de concentración FluidReflex. Por ´ultimo, se han diseñado, fabricado y caracterizado varios prototipos preindustriales de módulos FluidReflex para lo cual ha sido necesario optimizar el proceso de fabricación de la óptica multicavidad a fin de mantener el buen comportamiento óptico obtenido en la fabricación de la unidad elemental. Los distintos prototipos han sido medidos, tanto en el laboratorio como bajo el sol real, analizando el ajuste de corriente de la célula iluminada por el concentrador FluidReflex bajo diferentes distribuciones espectrales de la radiación incidente así como el excelente comportamiento térmico del módulo. ABSTRACT A renewed interest in concentrating photovoltaic (CPV) systems has emerged in recent years encouraged by the development of high-efficiency multijunction solar cells based in IIIV semiconductors that have led to CPV module efficiencies which practically double that of flat panel PV and which reach 35% for record modules. This thesis is devoted to the design and experimental implementation of new concepts for obtaining CPV modules that not only achieve high efficiency under standard conditions but also have such a wide tolerance to assembly errors, tracking, temperature and spectral variations, that the energy generated by them throughout the year is maximized. One of the first addressed issues is the design of secondary optical elements whose primary optics is a Fresnel lens and which, for a fixed concentration, allow an increased acceptance angle and tolerance of the system. Several reflective and refractive secondaries have been designed and analyzed using ray tracing. In particular, using nonimaging optics and based on the single-stage design known as ‘dielectric totally internally reflecting concentrator’, a secondary with square output has been designed, fabricated and characterized. Used together with a Fresnel lens, the secondary can simultaneously achieve high efficiency, concentration and acceptance. Furthermore, an alternative method has been proposed and prototyped for the fabrication of the secondary named dome. The optics is manufactured by direct overmolding of silicone over the solar cells. One characteristic that permeates all the work done in this thesis is the holistic approach in the design of CPV modules, meaning that special attention has been paid to the joint design of the solar cell and the optics to ensure that the total system achieves the highest attainable efficiency. In this regard, many optical systems developed in the thesis have been designed, characterized and optimized considering that the current matching among the subcells within the multijunction solar cell beneath the optics must be close to one. Antireflective coating over the cell acts, somehow, as an interface between the optics and the cell. Consequently, a method has been designed to optimize antireflective coatings that takes into account not only the broad wavelength range that multijunction solar cells are sensitive to but also the angular intensity distribution created by the concentrating optics. In addition, the issue of non-uniformity has also been addressed by comparing the spectral and spatial distributions of irradiance created by different optics (simulated by ray tracing and photographed) and the efficiency losses experienced by cells illuminated by those concentrating optics experimentally determined. The effect of temperature on the concentrating optics has also been studied in this thesis. In particular, finite element simulations have been use to analyze the deformations experienced by the facets of hybrid (silicon-glass) Fresnel lenses, the change of refractive index with temperature and the influence of both effects on the system performance. A model has been implemented which take into consideration atmospheric variations, mainly temperature and spectral content of the direct normal irradiance, as well as thermal and spectral sensitivities of systems, with the aim of maximizing the energy harvested by a CPV module throughout the year in a particular location. Chapters 5 and 6 of this book are devoted to the design, fabrication, and characterization of a new concentrator concept named FluidReflex and based on a single-stage reflective optics with fluid dielectric. In this new concept, the presence of the fluid provides some significant advantages such as: an increased concentration acceptance angle product (CAP) achievable by surrounding the cell with a medium whose refractive index is greater than one, an improvement of the optical efficiency by reducing losses due to Fresnel reflection at several interfaces, an improvement in heat dissipation as the heat concentrated near the cell is transmitted by natural convection and conduction in the fluid, and an improved electrical insulation. By fabricating and characterizing several elementary-unit prototypes it was shown that there is no fundamental reason that prevents the practical implementation of this theoretical concept reaching high efficiency. Several fluid candidates were investigated proving the existence of at least to fluids that meet all the requirements (including the stability under concentrated light) to become part of the FluidReflex concentrator. Finally, several pre-industrial FluidReflex module prototypes have been designed and fabricated. An optimization process for the manufacturing of the multicavity optics was necessary to attain such an optics quality as the one achieved by the single unit. The module prototypes have been measured, both indoors and outdoors, analyzing the current matching of the solar cells beneath the concentrator for different spectral distribution of the incident irradiance. Additionally, the module showed an excellent thermal performance.

An improvement of a SLAM RGB-D method with movement prediction derived from a study of visual features

This paper presents a method for the fast calculation of a robot’s egomotion using visual features. The method is part of a complete system for automatic map building and Simultaneous Location and Mapping (SLAM). The method uses optical flow to determine whether the robot has undergone a movement. If so, some visual features that do not satisfy several criteria are deleted, and then egomotion is calculated. Thus, the proposed method improves the efficiency of the whole process because not all the data is processed. We use a state-of-the-art algorithm (TORO) to rectify the map and solve the SLAM problem. Additionally, a study of different visual detectors and descriptors has been conducted to identify which of them are more suitable for the SLAM problem. Finally, a navigation method is described using the map obtained from the SLAM solution.