Ecological assessment data of the marine flora and fauna of Point Lookout in 2014 (PLEA)

In 2014, UniDive (The University of Queensland Underwater Club) conducted an ecological assessment of the Point Lookout Dive sites for comparison with similar surveys conducted in 2001. Involvement in the project was voluntary. Members of UniDive who were marine experts conducted training for other club members who had no, or limited, experience in identifying marine organisms and mapping habitats. Since the 2001 detailed baseline study, no similar seasonal survey has been conducted. The 2014 data is particularly important given that numerous changes have taken place in relation to the management of, and potential impacts on, these reef sites. In 2009, Moreton Bay Marine Park was re-zoned, and Flat Rock was converted to a marine national park zone (Green zone) with no fishing or anchoring. In 2012, four permanent moorings were installed at Flat Rock. Additionally, the entire area was exposed to the potential effects of the 2011 and 2013 Queensland floods, including flood plumes which carried large quantities of sediment into Moreton Bay and surrounding waters. The population of South East Queensland has increased from 2.49 million in 2001 to 3.18 million in 2011 (BITRE, 2013). This rapidly expanding coastal population has increased the frequency and intensity of both commercial and recreational activities around Point Lookout dive sites (EPA 2008). Methodology used for the PLEA project was based on the 2001 survey protocols, Reef Check Australia protocols and Coral Watch methods. This hybrid methodology was used to monitor substrate and benthos, invertebrates, fish, and reef health impacts. Additional analyses were conducted with georeferenced photo transects. The PLEA marine surveys were conducted over six weekends in 2014 totaling 535 dives and 376 hours underwater. Two training weekends (February and March) were attended by 44 divers, whilst biological surveys were conducted on seasonal weekends (February, May, July and October). Three reefs were surveyed, with two semi-permanent transects at Flat Rock, two at Shag Rock, and one at Manta Ray Bommie. Each transect was sampled once every survey weekend, with the transect tapes deployed at a depth of 10 m below chart datum. Fish populations were assessed using a visual census along 3 x 20 m transects. Each transect was 5 m wide (2.5 m either side of the transect tape), 5 m high and 20 m in length. Fish families and species were chosen that are commonly targeted by recreational or commercial fishers, or targeted by aquarium collectors, and that were easily identified by their body shape. Rare or otherwise unusual species were also recorded. Target invertebrate populations were assessed using visual census along 3 x 20 m transects. Each transect was 5 m wide (2.5 m either side of the transect tape) and 20 m in length. The diver surveying invertebrates conducted a 'U-shaped' search pattern, covering 2.5 m on either side of the transect tape. Target impacts were assessed using a visual census along the 3 x 20 m transects. Each transect was 5 m wide (2.5 m either side of the transect tape) and 20 m in length. The transect was surveyed via a 'U-shaped' search pattern, covering 2.5 m on either side of the transect tape. Substrate surveys were conducted using the point sampling method, enabling percentage cover of substrate types and benthic organisms to be calculated. The substrate or benthos under the transect line was identified at 0.5m intervals, with a 5m gap between each of the three 20m segments. Categories recorded included various growth forms of hard and soft coral, key species/growth forms of algae, other living organisms (i.e. sponges), recently killed coral, and, non-living substrate types (i.e. bare rock, sand, rubble, silt/clay).

The responses of eight coral reef calcifiers to increasing partial pressure of CO2 do not exhibit a tipping point

The objective of this study was to investigate whether a tipping point exists in the calcification responses of coral reef calcifiers to CO2. We compared the effects of six partial pressures of CO2 (PCO2) from 28 Pa to 210 Pa on the net calcification of four corals (Acropora pulchra, Porites rus, Pocillopora damicornis, and Pavona cactus), and four calcified algae (Hydrolithon onkodes, Lithophyllum flavescens, Halimeda macroloba, and Halimeda minima). After 2 weeks of acclimation in a common environment, organisms were incubated in 12 aquaria for 2 weeks at the targeted PCO2 levels and net calcification was quantified. All eight species calcified at the highest PCO2 in which the calcium carbonate aragonite saturation state was ~1. Calcification decreased linearly as a function of increasing partial PCO2 in three corals and three algae. Overall, the decrease in net calcification as a function of decreasing pH was ~10% when ambient PCO2 (39 Pa) was doubled. The calcification responses of P. damicornis and H. macroloba were unaffected by increasing PCO2. These results are inconsistent with the notion that coral reefs will be affected by rising PCO2 in a response characterized by a tipping point. Instead, our findings combined among taxa suggest a gradual decline in calcification will occur, but this general response includes specific cases of complete resistance to rising PCO2. Together our results suggest that the overall response of coral reef communities to ocean acidification will be monotonic and inversely proportional to PCO2, with reef-wide responses dependent on the species composition of calcifying taxa.

Common depth points and associated geographic coordinates

Fluids in subduction zones can influence seismogenic behaviour and prism morphology. The Eastern Makran subduction zone, offshore Pakistan, has a very thick incoming sediment section of up to 7.5 km, providing a large potential fluid source to the accretionary prism. A hydrate-related bottom simulating reflector (BSR), zones of high amplitude reflectivity, seafloor seep sites and reflective thrust faults are present across the accretionary prism, indicating the presence of fluids and suggesting active fluid migration. High amplitude free gas zones and seep sites are primarily associated with anticlinal hinge traps, and fluids here appear to be sourced from shallow biogenic sources and migrate to the seafloor along minor normal faults. There are no observed seep sites associated with the surface expression of the wedge thrust faults, potentially due to burial of the surface trace by failure of the steep thrust ridge slopes. Thrust fault reflectivity is restricted to the upper 3 km of sediment and the deeper décollement is non-reflective. We interpret that fluids and overpressure are not common in the deeper stratigraphic section. Thermal modelling of sediments at the deformation front suggests that the deeper sediment section is relatively dewatered and not currently contributing to fluid expulsion in the Makran accretionary prism.

(Supplementary Table 1) Mercury isotope values for common and thick-billed murre (Uria aalge, Uria lomvia) eggs from Alaska

Atmospheric deposition of mercury to remote areas has increased threefold since pre-industrial times. Mercury deposition is particularly pronounced in the Arctic. Following deposition to surface oceans and sea ice, mercury can be converted into methylmercury, a biologically accessible form of the toxin, which biomagnifies along the marine food chain. Mass-independent fractionation of mercury isotopes accompanies the photochemical breakdown of methylmercury to less bioavailable forms in surface waters. Here we examine the isotopic composition of mercury in seabird eggs collected from colonies in the North Pacific Ocean, the Bering Sea and the western Arctic Ocean, to determine geographical variations in methylmercury breakdown at northern latitudes. We find evidence for mass-independent fractionation of mercury isotopes. The degree of mass-independent fractionation declines with latitude. Foraging behaviour and geographic variations in mercury sources and solar radiation fluxes were unable to explain the latitudinal gradient. However, mass-independent fractionation was negatively correlated with sea-ice cover. We conclude that sea-ice cover impedes the photochemical breakdown of methylmercury in surface waters, and suggest that further loss of Arctic sea ice this century will accelerate sunlight-induced breakdown of methylmercury in northern surface waters.

Evaluación de la profundidad de la fisuración superficial descendente en pavimentos asfálticos mediante técnicas de ultrasonidos. Validación teórico-práctica y modelos

La fisuración iniciada en la superficie de los pavimentos asfálticos constituye uno de los más frecuentes e importantes modos de deterioro que tienen lugar en los firmes bituminosos, como han demostrado los estudios teóricos y experimentales llevados a cabo en la última década. Sin embargo, este mecanismo de fallo no ha sido considerado por los métodos tradicionales de diseño de estos firmes. El concepto de firmes de larga duración se fundamenta en un adecuado seguimiento del proceso de avance en profundidad de estos deterioros y la intervención en el momento más apropiado para conseguir mantenerlos confinados como fisuras de profundidad parcial en la capa superficial más fácilmente accesible y reparable, de manera que pueda prolongarse la durabilidad y funcionalidad del firme y reducir los costes generalizados de su ciclo de vida. Por lo tanto, para la selección de la estrategia óptima de conservación de los firmes resulta esencial disponer de metodologías que posibiliten la identificación precisa in situ de la fisuración descendente, su seguimiento y control, y que además permitan una determinación fiable y con alto rendimiento de su profundidad y extensión. En esta Tesis Doctoral se presentan los resultados obtenidos mediante la investigación sistemática de laboratorio e in situ llevada a cabo para la obtención de datos sobre fisuración descendente en firmes asfálticos y para el estudio de procedimientos de evaluación de la profundidad de este tipo de fisuras empleando técnicas de ultrasonidos. Dichos resultados han permitido comprobar que la metodología no destructiva propuesta, de rápida ejecución, bajo coste y sencilla implementación (principalmente empleada hasta el momento en estructuras metálicas y de hormigón, debido a las dificultades que introduce la naturaleza viscoelástica de los materiales bituminosos) puede ser aplicada con suficiente fiabilidad y repetibilidad sobre firmes asfálticos. Las medidas resultan asimismo independientes del espesor total del firme. Además, permite resolver algunos de los inconvenientes frecuentes que presentan otros métodos de diagnóstico de las fisuras de pavimentos, tales como la extracción de testigos (sistema destructivo, de alto coste y prolongados tiempos de interrupción del tráfico) o algunas otras técnicas no destructivas como las basadas en medidas de deflexiones o el georradar, las cuales no resultan suficientemente precisas para la investigación de fisuras superficiales. Para ello se han realizado varias campañas de ensayos sobre probetas de laboratorio en las que se han estudiado diferentes condiciones empíricas como, por ejemplo, distintos tipos de mezclas bituminosas en caliente (AC, SMA y PA), espesores de firme y adherencias entre capas, temperaturas, texturas superficiales, materiales de relleno y agua en el interior de las grietas, posición de los sensores y un amplio rango de posibles profundidades de fisura. Los métodos empleados se basan en la realización de varias medidas de velocidad o de tiempo de transmisión del pulso ultrasónico sobre una única cara o superficie accesible del material, de manera que resulte posible obtener un coeficiente de transmisión de la señal (mediciones relativas o autocompensadas). Las mediciones se han realizado a bajas frecuencias de excitación mediante dos equipos de ultrasonidos diferentes dotados, en un caso, de transductores de contacto puntual seco (DPC) y siendo en el otro instrumento de contacto plano a través de un material especialmente seleccionado para el acoplamiento (CPC). Ello ha permitido superar algunos de los tradicionales inconvenientes que presenta el uso de los transductores convencionales y no precisar preparación previa de las superficies. La técnica de autocalibración empleada elimina los errores sistemáticos y la necesidad de una calibración local previa, demostrando el potencial de esta tecnología. Los resultados experimentales han sido comparados con modelos teóricos simplificados que simulan la propagación de las ondas ultrasónicas en estos materiales bituminosos fisurados, los cuales han sido deducidos previamente mediante un planteamiento analítico y han permitido la correcta interpretación de dichos datos empíricos. Posteriormente, estos modelos se han calibrado mediante los resultados de laboratorio, proporcionándose sus expresiones matemáticas generalizadas y gráficas para su uso rutinario en las aplicaciones prácticas. Mediante los ensayos con ultrasonidos efectuados en campañas llevadas a cabo in situ, acompañados de la extracción de testigos del firme, se han podido evaluar los modelos propuestos. El máximo error relativo promedio en la estimación de la profundidad de las fisuras al aplicar dichos modelos no ha superado el 13%, con un nivel de confianza del 95%, en el conjunto de todos los ensayos realizados. La comprobación in situ de los modelos ha permitido establecer los criterios y las necesarias recomendaciones para su utilización sobre firmes en servicio. La experiencia obtenida posibilita la integración de esta metodología entre las técnicas de auscultación para la gestión de su conservación. Abstract Surface-initiated cracking of asphalt pavements constitutes one of the most frequent and important types of distress that occur in flexible bituminous pavements, as clearly has been demonstrated in the technical and experimental studies done over the past decade. However, this failure mechanism has not been taken into consideration for traditional methods of flexible pavement design. The concept of long-lasting pavements is based on adequate monitoring of the depth and extent of these deteriorations and on intervention at the most appropriate moment so as to contain them in the surface layer in the form of easily-accessible and repairable partial-depth topdown cracks, thereby prolonging the durability and serviceability of the pavement and reducing the overall cost of its life cycle. Therefore, to select the optimal maintenance strategy for perpetual pavements, it becomes essential to have access to methodologies that enable precise on-site identification, monitoring and control of top-down propagated cracks and that also permit a reliable, high-performance determination of the extent and depth of cracking. This PhD Thesis presents the results of systematic laboratory and in situ research carried out to obtain information about top-down cracking in asphalt pavements and to study methods of depth evaluation of this type of cracking using ultrasonic techniques. These results have demonstrated that the proposed non-destructive methodology –cost-effective, fast and easy-to-implement– (mainly used to date for concrete and metal structures, due to the difficulties caused by the viscoelastic nature of bituminous materials) can be applied with sufficient reliability and repeatability to asphalt pavements. Measurements are also independent of the asphalt thickness. Furthermore, it resolves some of the common inconveniences presented by other methods used to evaluate pavement cracking, such as core extraction (a destructive and expensive procedure that requires prolonged traffic interruptions) and other non-destructive techniques, such as those based on deflection measurements or ground-penetrating radar, which are not sufficiently precise to measure surface cracks. To obtain these results, extensive tests were performed on laboratory specimens. Different empirical conditions were studied, such as various types of hot bituminous mixtures (AC, SMA and PA), differing thicknesses of asphalt and adhesions between layers, varied temperatures, surface textures, filling materials and water within the crack, different sensor positions, as well as an ample range of possible crack depths. The methods employed in the study are based on a series of measurements of ultrasonic pulse velocities or transmission times over a single accessible side or surface of the material that make it possible to obtain a signal transmission coefficient (relative or auto-calibrated readings). Measurements were taken at low frequencies by two short-pulse ultrasonic devices: one equipped with dry point contact transducers (DPC) and the other with flat contact transducers that require a specially-selected coupling material (CPC). In this way, some of the traditional inconveniences presented by the use of conventional transducers were overcome and a prior preparation of the surfaces was not required. The auto-compensating technique eliminated systematic errors and the need for previous local calibration, demonstrating the potential for this technology. The experimental results have been compared with simplified theoretical models that simulate ultrasonic wave propagation in cracked bituminous materials, which had been previously deduced using an analytical approach and have permitted the correct interpretation of the aforementioned empirical results. These models were subsequently calibrated using the laboratory results, providing generalized mathematical expressions and graphics for routine use in practical applications. Through a series of on-site ultrasound test campaigns, accompanied by asphalt core extraction, it was possible to evaluate the proposed models, with differences between predicted crack depths and those measured in situ lower than 13% (with a confidence level of 95%). Thereby, the criteria and the necessary recommendations for their implementation on in-service asphalt pavements have been established. The experience obtained through this study makes it possible to integrate this methodology into the evaluation techniques for pavement management systems.

Coupling time-stepping numerical methods and standard aerodynamics codes for instability analysis of flows in complex geometries

The development of a global instability analysis code coupling a time-stepping approach, as applied to the solution of BiGlobal and TriGlobal instability analysis 1, 2 and finite-volume-based spatial discretization, as used in standard aerodynamics codes is presented. The key advantage of the time-stepping method over matrix-formulation approaches is that the former provides a solution to the computer-storage issues associated with the latter methodology. To-date both approaches are successfully in use to analyze instability in complex geometries, although their relative advantages have never been quantified. The ultimate goal of the present work is to address this issue in the context of spatial discretization schemes typically used in industry. The time-stepping approach of Chiba 3 has been implemented in conjunction with two direct numerical simulation algorithms, one based on the typically-used in this context high-order method and another based on low-order methods representative of those in common use in industry. The two codes have been validated with solutions of the BiGlobal EVP and it has been showed that small errors in the base flow do not have affect significantly the results. As a result, a three-dimensional compressible unsteady second-order code for global linear stability has been successfully developed based on finite-volume spatial discretization and time-stepping method with the ability to study complex geometries by means of unstructured and hybrid meshes

Biosensors based on vertically interrogated optofluidic sensing cells

El objetivo de la presente tesis doctoral es el desarrollo de un nuevo concepto de biosensor óptico sin marcado, basado en una combinación de técnicas de caracterización óptica de interrogación vertical y estructuras sub-micrométricas fabricadas sobre chips de silicio. Las características más importantes de dicho dispositivo son su simplicidad, tanto desde el punto de vista de medida óptica como de introducción de las muestras a medir en el área sensible, aspectos que suelen ser críticos en la mayoría de sensores encontrados en la literatura. Cada uno de los aspectos relacionados con el diseño de un biosensor, que son fundamentalmente cuatro (diseño fotónico, caracterización óptica, fabricación y fluídica/inmovilización química) son desarrollados en detalle en los capítulos correspondientes. En la primera parte de la tesis se hace una introducción al concepto de biosensor, en qué consiste, qué tipos hay y cuáles son los parámetros más comunes usados para cuantificar su comportamiento. Posteriormente se realiza un análisis del estado del arte en la materia, enfocado en particular en el área de biosensores ópticos sin marcado. Se introducen también cuáles son las reacciones bioquímicas a estudiar (inmunoensayos). En la segunda parte se describe en primer lugar cuáles son las técnicas ópticas empleadas en la caracterización: Reflectometría, Elipsometría y Espectrometría; además de los motivos que han llevado a su empleo. Posteriormente se introducen diversos diseños de las denominadas "celdas optofluídicas", que son los dispositivos en los que se va a producir la interacción bioquímica. Se presentan cuatro dispositivos diferentes, y junto con ellos, se proponen diversos métodos de cálculo teórico de la respuesta óptica esperada. Posteriormente se procede al cálculo de la sensibilidad esperada para cada una de las celdas, así como al análisis de los procesos de fabricación de cada una de ellas y su comportamiento fluídico. Una vez analizados todos los aspectos críticos del comportamiento del biosensor, se puede realizar un proceso de optimización de su diseño. Esto se realiza usando un modelo de cálculo simplificado (modelo 1.5-D) que permite la obtención de parámetros como la sensibilidad y el límite de detección de un gran número de dispositivos en un tiempo relativamente reducido. Para este proceso se escogen dos de las celdas optofluídicas propuestas. En la parte final de la tesis se muestran los resultados experimentales obtenidos. En primer lugar, se caracteriza una celda basada en agujeros sub-micrométricos como sensor de índice de refracción, usando para ello diferentes líquidos orgánicos; dichos resultados experimentales presentan una buena correlación con los cálculos teóricos previos, lo que permite validar el modelo conceptual presentado. Finalmente, se realiza un inmunoensayo químico sobre otra de las celdas propuestas (pilares nanométricos de polímero SU-8). Para ello se utiliza el inmunoensayo de albumina de suero bovino (BSA) y su anticuerpo (antiBSA). Se detalla el proceso de obtención de la celda, la funcionalización de la superficie con los bioreceptores (en este caso, BSA) y el proceso de biorreconocimiento. Este proceso permite dar una primera estimación de cuál es el límite de detección esperable para este tipo de sensores en un inmunoensayo estándar. En este caso, se alcanza un valor de 2.3 ng/mL, que es competitivo comparado con otros ensayos similares encontrados en la literatura. La principal conclusión de la tesis es que esta tipología de dispositivos puede ser usada como inmunosensor, y presenta ciertas ventajas respecto a los actualmente existentes. Estas ventajas vienen asociadas, de nuevo, a su simplicidad, tanto a la hora de medir ópticamente, como dentro del proceso de introducción de los bioanalitos en el área sensora (depositando simplemente una gota sobre la micro-nano-estructura). Los cálculos teorícos realizados en los procesos de optimización sugieren a su vez que el comportamiento del sensor, medido en magnitudes como límite de detección biológico puede ser ampliamente mejorado con una mayor compactación de pilares, alcanzandose un valor mínimo de 0.59 ng/mL). The objective of this thesis is to develop a new concept of optical label-free biosensor, based on a combination of vertical interrogation optical techniques and submicron structures fabricated over silicon chips. The most important features of this device are its simplicity, both from the point of view of optical measurement and regarding to the introduction of samples to be measured in the sensing area, which are often critical aspects in the majority of sensors found in the literature. Each of the aspects related to the design of biosensors, which are basically four (photonic design, optical characterization, fabrication and fluid / chemical immobilization) are developed in detail in the relevant chapters. The first part of the thesis consists of an introduction to the concept of biosensor: which elements consists of, existing types and the most common parameters used to quantify its behavior. Subsequently, an analysis of the state of the art in this area is presented, focusing in particular in the area of label free optical biosensors. What are also introduced to study biochemical reactions (immunoassays). The second part describes firstly the optical techniques used in the characterization: reflectometry, ellipsometry and spectrometry; in addition to the reasons that have led to their use. Subsequently several examples of the so-called "optofluidic cells" are introduced, which are the devices where the biochemical interactions take place. Four different devices are presented, and their optical response is calculated by using various methods. Then is exposed the calculation of the expected sensitivity for each of the cells, and the analysis of their fabrication processes and fluidic behavior at the sub-micrometric range. After analyzing all the critical aspects of the biosensor, it can be performed a process of optimization of a particular design. This is done using a simplified calculation model (1.5-D model calculation) that allows obtaining parameters such as sensitivity and the detection limit of a large number of devices in a relatively reduced time. For this process are chosen two different optofluidic cells, from the four previously proposed. The final part of the thesis is the exposition of the obtained experimental results. Firstly, a cell based sub-micrometric holes is characterized as refractive index sensor using different organic fluids, and such experimental results show a good correlation with previous theoretical calculations, allowing to validate the conceptual model presented. Finally, an immunoassay is performed on another typology of cell (SU-8 polymer pillars). This immunoassay uses bovine serum albumin (BSA) and its antibody (antiBSA). The processes for obtaining the cell surface functionalization with the bioreceptors (in this case, BSA) and the biorecognition (antiBSA) are detailed. This immunoassay can give a first estimation of which are the expected limit of detection values for this typology of sensors in a standard immunoassay. In this case, it reaches a value of 2.3 ng/mL, which is competitive with other similar assays found in the literature. The main conclusion of the thesis is that this type of device can be used as immunosensor, and has certain advantages over the existing ones. These advantages are associated again with its simplicity, by the simpler coupling of light and in the process of introduction of bioanalytes into the sensing areas (by depositing a droplet over the micro-nano-structure). Theoretical calculations made in optimizing processes suggest that the sensor Limit of detection can be greatly improved with higher compacting of the lattice of pillars, reaching a minimum value of 0.59 ng/mL).

Novel Inductor‐less Conversion Strategy Based on Multiphase Transformer‐Coupled Converters: Analysis, Design and Applications

There are many the requirements that modern power converters should fulfill. Most of the applications where these converters are used, demand smaller converters with high efficiency, improved power density and a fast dynamic response. For instance, loads like microprocessors demand aggressive current steps with very high slew rates (100A/mus and higher); besides, during these load steps, the supply voltage of the microprocessor should be kept within tight limits in order to ensure its correct performance. The accomplishment of these requirements is not an easy task; complex solutions like advanced topologies - such as multiphase converters- as well as advanced control strategies are often needed. Besides, it is also necessary to operate the converter at high switching frequencies and to use capacitors with high capacitance and low ESR. Improving the dynamic response of power converters does not rely only on the control strategy but also the power topology should be suited to enable a fast dynamic response. Moreover, in later years, a fast dynamic response does not only mean accomplishing fast load steps but output voltage steps are gaining importance as well. At least, two applications that require fast voltage changes can be named: Low power microprocessors. In these devices, the voltage supply is changed according to the workload and the operating frequency of the microprocessor is changed at the same time. An important reduction in voltage dependent losses can be achieved with such changes. This technique is known as Dynamic Voltage Scaling (DVS). Another application where important energy savings can be achieved by means of changing the supply voltage are Radio Frequency Power Amplifiers. For example, RF architectures based on ‘Envelope Tracking’ and ‘Envelope Elimination and Restoration’ techniques can take advantage of voltage supply modulation and accomplish important energy savings in the power amplifier. However, in order to achieve these efficiency improvements, a power converter with high efficiency and high enough bandwidth (hundreds of kHz or even tens of MHz) is necessary in order to ensure an adequate supply voltage. The main objective of this Thesis is to improve the dynamic response of DC-DC converters from the point of view of the power topology. And the term dynamic response refers both to the load steps and the voltage steps; it is also interesting to modulate the output voltage of the converter with a specific bandwidth. In order to accomplish this, the question of what is it that limits the dynamic response of power converters should be answered. Analyzing this question leads to the conclusion that the dynamic response is limited by the power topology and specifically, by the filter inductance of the converter which is found in series between the input and the output of the converter. The series inductance is the one that determines the gain of the converter and provides the regulation capability. Although the energy stored in the filter inductance enables the regulation and the capability of filtering the output voltage, it imposes a limitation which is the concern of this Thesis. The series inductance stores energy and prevents the current from changing in a fast way, limiting the slew rate of the current through this inductor. Different solutions are proposed in the literature in order to reduce the limit imposed by the filter inductor. Many publications proposing new topologies and improvements to known topologies can be found in the literature. Also, complex control strategies are proposed with the objective of improving the dynamic response in power converters. In the proposed topologies, the energy stored in the series inductor is reduced; examples of these topologies are Multiphase converters, Buck converter operating at very high frequency or adding a low impedance path in parallel with the series inductance. Control techniques proposed in the literature, focus on adjusting the output voltage as fast as allowed by the power stage; examples of these control techniques are: hysteresis control, V 2 control, and minimum time control. In some of the proposed topologies, a reduction in the value of the series inductance is achieved and with this, the energy stored in this magnetic element is reduced; less stored energy means a faster dynamic response. However, in some cases (as in the high frequency Buck converter), the dynamic response is improved at the cost of worsening the efficiency. In this Thesis, a drastic solution is proposed: to completely eliminate the series inductance of the converter. This is a more radical solution when compared to those proposed in the literature. If the series inductance is eliminated, the regulation capability of the converter is limited which can make it difficult to use the topology in one-converter solutions; however, this topology is suitable for power architectures where the energy conversion is done by more than one converter. When the series inductor is eliminated from the converter, the current slew rate is no longer limited and it can be said that the dynamic response of the converter is independent from the switching frequency. This is the main advantage of eliminating the series inductor. The main objective, is to propose an energy conversion strategy that is done without series inductance. Without series inductance, no energy is stored between the input and the output of the converter and the dynamic response would be instantaneous if all the devices were ideal. If the energy transfer from the input to the output of the converter is done instantaneously when a load step occurs, conceptually it would not be necessary to store energy at the output of the converter (no output capacitor COUT would be needed) and if the input source is ideal, the input capacitor CIN would not be necessary. This last feature (no CIN with ideal VIN) is common to all power converters. However, when the concept is actually implemented, parasitic inductances such as leakage inductance of the transformer and the parasitic inductance of the PCB, cannot be avoided because they are inherent to the implementation of the converter. These parasitic elements do not affect significantly to the proposed concept. In this Thesis, it is proposed to operate the converter without series inductance in order to improve the dynamic response of the converter; however, on the other side, the continuous regulation capability of the converter is lost. It is said continuous because, as it will be explained throughout the Thesis, it is indeed possible to achieve discrete regulation; a converter without filter inductance and without energy stored in the magnetic element, is capable to achieve a limited number of output voltages. The changes between these output voltage levels are achieved in a fast way. The proposed energy conversion strategy is implemented by means of a multiphase converter where the coupling of the phases is done by discrete two-winding transformers instead of coupledinductors since transformers are, ideally, no energy storing elements. This idea is the main contribution of this Thesis. The feasibility of this energy conversion strategy is first analyzed and then verified by simulation and by the implementation of experimental prototypes. Once the strategy is proved valid, different options to implement the magnetic structure are analyzed. Three different discrete transformer arrangements are studied and implemented. A converter based on this energy conversion strategy would be designed with a different approach than the one used to design classic converters since an additional design degree of freedom is available. The switching frequency can be chosen according to the design specifications without penalizing the dynamic response or the efficiency. Low operating frequencies can be chosen in order to favor the efficiency; on the other hand, high operating frequencies (MHz) can be chosen in order to favor the size of the converter. For this reason, a particular design procedure is proposed for the ‘inductorless’ conversion strategy. Finally, applications where the features of the proposed conversion strategy (high efficiency with fast dynamic response) are advantageus, are proposed. For example, in two-stage power architectures where a high efficiency converter is needed as the first stage and there is a second stage that provides the fine regulation. Another example are RF power amplifiers where the voltage is modulated following an envelope reference in order to save power; in this application, a high efficiency converter, capable of achieving fast voltage steps is required. The main contributions of this Thesis are the following: The proposal of a conversion strategy that is done, ideally, without storing energy in the magnetic element. The validation and the implementation of the proposed energy conversion strategy. The study of different magnetic structures based on discrete transformers for the implementation of the proposed energy conversion strategy. To elaborate and validate a design procedure. To identify and validate applications for the proposed energy conversion strategy. It is important to remark that this work is done in collaboration with Intel. The particular features of the proposed conversion strategy enable the possibility of solving the problems related to microprocessor powering in a different way. For example, the high efficiency achieved with the proposed conversion strategy enables it as a good candidate to be used for power conditioning, as a first stage in a two-stage power architecture for powering microprocessors.

Characterization of a Right Angle Transfer Point in a Fruit Packing Line

Characteristics of the impacts su!ered by the fruit on a transfer point of an experimental fruit packing line were analysed. The transfer is made up by two transporting belts at di!erent heights forming an angle of 903. These transfer points are very common in fruit packing lines, in which fruits receive two impacts: the "rst onto the belt base and the second into the lateral plate. Diferent tests were carried out to study the e!ect of transfer height, velocity, belt structure and padding on the acceleration values recorded by an instrumental sphere (IS 100). Results showed that transfer height and belt structure a!ect mainly impact values on the belt base, and padding a!ects mainly impact values registered for lateral contact. The elect of belt velocity in both impacts is less important when compared to the rest of the variables. Additionally, two powered transfer decelerators were tested at the same point with the aim of decreasing impacts su!ered by the fruit. Comparing impacts registered using these decelerators to those analysed in the first part of the study without decelerators, a high reduction of the impact values was observed.

Dynamic stabilization of L2 periodic orbits using attitude-orbit coupling effects

Numerical explorations show how the known periodic solutions of the Hill problem are modified in the case of the attitude-orbit coupling that may occur for large satellite structures. We focus on the case in which the elongation is the dominant satellite’s characteristic and find that a rotating structure may remain with its largest dimension in a plane parallel to the plane of the primaries. In this case, the effect produced by the non-negligible physical length is dynamically equivalent to the perturbation produced by an oblate central body on a mass-point satellite. Based on this, it is demonstrated that the attitude-orbital coupling of a long enough body may change the dynamical characteristics of a periodic orbit about the collinear Lagrangian points.

Characterization of a 90° Transfer Point in a Fruit Packing Line.

Characteristics of the impacts suffered by the fruit on a transfer point of an experimental fruit packing line were analysed. The transfer is made up by two transporting belts at different heights forming an angle of 90°. These transfer points are very common in fruit packing lines, in which fruits receive two impacts: the first onto the belt base and the second into the lateral plate. Different tests were earned out to study the effect of transfer height, velocity, belt structure and padding on tire acceleration values recorded by an instrumental sphere (IS 100). Results showed that transfer height and belt structure affect mainly impact values on the belt base, and padding affects mainly impact values registered in lateral impact. The effect of belt velocity in both impacts is less important when compared to the rest of the variables. Additionally, two powered transfer decelerators were tested at the same point with the aim of decreasing impacts suffered by the fruit. Comparing impacts registered using these decelerators to those analysed in the first part of the study without decelerators a high reduction of the impact values was observed.

Generalized synchronization in relay systems with instantaneous coupling

We demonstrate the existence of generalized synchronization in systems that act as mediators between two dynamical units that, in turn, show complete synchronization with each other. These are the so-called relay systems. Specifically, we analyze the Lyapunov spectrum of the full system to elucidate when complete and generalized synchronization appear. We show that once a critical coupling strength is achieved, complete synchronization emerges between the systems to be synchronized, and at the same point, generalized synchronization with the relay system also arises. Next, we use two nonlinear measures based on the distance between phase-space neighbors to quantify the generalized synchronization in discretized time series. Finally, we experimentally show the robustness of the phenomenon and of the theoretical tools here proposed to characterize it.