Circular polarisation frequency selective surface operating in Ku and Ka band

A double layer circular polarization (CP) frequency selective surface (FSS) for use as a dual-band quasi-optical diplexer suitable for deployment in reflector antenna systems is described. The FSS was designed to reflect Ku band signals (11.7–12.75 GHz) while transmitting Ka band signals (17.3–20.2 GHz) and conserving CP in each of these bands. The simulated/measured reflection loss over the Ku band was less than 0.05/0.1 dB for both TE and TM polarizations, while the simulated/measured axial ratio was less than 0.2/0.75 dB. Over the Ka band, the simulated/measured transmission loss for both polarizations was below 0.25/0.4 dB and the simulated/measured axial ratio was less than 0.25/0.75 dB. To the best of our knowledge, this is the first report of a metallo-dielectric FSS that simultaneously operates in CP for an oblique angle of incidence in both Ku and Ka bands.

Secagem convectiva de produtos alimentares: otimização e controlo

O presente trabalho tem como objetivo analisar a cinética de secagem do bacalhau salgado verde (Gadus morhua) em secador convectivo. É apresentada a análise da composição físico-química dos bacalhaus utilizados nos ensaios experimentais, bem como o estudo das isotermas de sorção do produto, através de experiências e modelação matemática. Dos modelos usados para o ajuste das isotermas de sorção do bacalhau salgado verde, o que melhor se adaptou aos resultados experimentais foi o modelo de GAB Modificado, com coeficientes de correlação variando entre 0,992 e 0,998. Para o controlo do processo de secagem (nomeadamente os parâmetros temperatura, humidade relativa e velocidade do ar) foi utilizada lógica difusa, através do desenvolvimento de controladores difusos para o humidificador, desumidificador, resistências de aquecimento e ventilador. A modelação do processo de secagem foi realizada através de redes neuronais artificiais (RNA), modelo semi-empírico de Page e modelo difusivo de Fick. A comparação entre dados experimentais e simulados, para cada modelo, apresentou os seguintes erros: entre 1,43 e 11,58 para o modelo de Page, 0,34 e 4,59 para o modelo de Fick e entre 1,13 e 6,99 para a RNA, com médias de 4,38, 1,67 e 2,93 respectivamente. O modelo obtido pelas redes neuronais artificiais foi submetido a um algoritmo de otimização, a fim de buscar os parâmetros ideais de secagem, de forma a minimizar o tempo do processo e maximizar a perda de água do bacalhau. Os parâmetros ótimos obtidos para o processo de secagem, após otimização realizada, para obter-se uma humidade adimensional final de 0,65 foram: tempo de 68,6h, temperatura de 21,45°C, humidade relativa de 51,6% e velocidade de 1,5m/s. Foram também determinados os custos de secagem para as diferentes condições operacionais na instalação experimental. Os consumos por hora de secagem variaram entre 1,15 kWh e 2,87kWh, com uma média de 1,94kWh.

Interactions of cetaceans with Spanish and Portuguese fisheries in Atlantic waters : costs, benefits and implications for management

With the aim to provide new insights into operational cetacean-fishery interactions in Atlantic waters, this thesis assesses interactions of cetaceans with Spanish and Portuguese fishing vessels operating in Iberian and South West Atlantic waters. Different opportunistic research methodologies were applied, including an interview survey with fishers (mainly skippers) and onboard observations by fisheries observers and skippers, to describe different types of interactions and to identify potential hotspots for cetacean-fishery interactions and the cetacean species most involved, and to quantify the extent and the consequences of these interactions in terms of benefits and costs for cetaceans and fisheries. In addition, the suitability of different mitigation strategies was evaluated and discussed. The results of this work indicate that cetaceans interact frequently with Spanish and Portuguese fishing vessels, sometimes in a beneficial way (e.g. cetaceans indicate fish schools in purse seine fisheries), but mostly with negative consequences (depredation on catch, gear damage and cetacean bycatch). Significant economic loss and high bycatch rates are, however, only reported for certain fisheries and associated with particular cetacean species. In Galician fisheries, substantial economic loss was reported as a result of bottlenose dolphins damaging artisanal coastal gillnets, while high catch loss may arise from common dolphins scattering fish in purse seine fisheries. High cetacean bycatch mortality arises in trawl fisheries, mainly of common dolphin and particularly during trawling in water depths below 350 m, and in coastal set gillnet fisheries (mainly common and bottlenose dolphins). In large-scale bottom-set longline fisheries in South West Atlantic waters, sperm whales may significantly reduce catch rates through depredation on catch. The high diversity of cetacean-fishery interactions observed in the study area indicates that case-specific management strategies are needed to reduce negative impacts on fisheries and cetaceans. Acoustic deterrent devices (pingers) may be used to prevent small cetaceans from approaching and getting entangled in purse seines and set gillnets, although possible problems include cetacean habituation to the pinger sounds, as well as negative side effects on non-target cetaceans (habitat exclusion) and fisheries target species (reduced catch rates). For sardine and horse mackerel, target species of Iberian Atlantic fisheries, no aversive reaction to pinger sounds was detected during tank experiments conducted in the scope of this thesis. Bycatch in trawls may be reduced by the implementation of time/area restrictions of fishing activity. In addition, the avoidance of fishing areas with high cetacean abundance combined with the minimization of fishery-specific sound cues that possibly attract cetaceans, may also help to decrease interactions. In large-scale bottom-set longline fisheries, cetacean depredation on catch may be reduced by covering hooked fish with net sleeves ("umbrellas") provided that catch rates are not negatively affected by this gear modification. Trap fishing, as an alternative fishing method to bottom-set gillnetting and longlining, also has the potential to reduce cetacean bycatch and depredation, given that fish catch rates are similar to the rates obtained by bottom-set gillnets and longlines, whereas cetacean by-catch is unlikely. Economic incentives, such as the eco-certification of dolphin-safe fishing methods, should be promoted in order to create an additional source of income for fishers negatively affected by interactions with cetaceans, which, in turn, may also increase fishers’ willingness to accept and adopt mitigation measures. Although the opportunistic sampling methods applied in this work have certain restrictions concerning their reliability and precision, the results are consistent with previous studies in the same area. Moreover, they allow for the active participation of fishers that can provide important complementary ecological and technical knowledge required for cetacean management and conservation.

Mercaptans extraction from jet-fuel streams using ionic liquids

Desulfurization is one of the most important processes in the refining industry. Due to a growing concern about the risks to human health and environment, associated with the emissions of sulfur compounds, legislation has become more stringent, requiring a drastic reduction in the sulfur content of fuel to levels close to zero (< 10 ppm S). However, conventional desulfurization processes are inefficient and have high operating costs. This scenario stimulates the improvement of existing processes and the development of new and more efficient technologies. Aiming at overcoming these shortcomings, this work investigates an alternative desulfurization process using ionic liquids for the removal of mercaptans from "jet fuel" streams. The screening and selection of the most suitable ionic liquid were performed based on experimental and COSMO-RS predicted liquid-liquid equilibrium data. A model feed of 1-hexanethiol and n-dodecane was selected to represent a jet-fuel stream. High selectivities were determined, as a result of the low mutual solubility between the ionic liquid and the hydrocarbon matrix, proving the potential use of the ionic liquid, which prevents the loss of fuel for the solvent. The distribution ratios of mercaptans towards the ionic liquids were not as favorable, making the traditional liquid-liquid extraction processes not suitable for the removal of aliphatic S-compounds due to the high volume of extractant required. This work explores alternative methods and proposes the use of ionic liquids in a separation process assisted by membranes. In the process proposed the ionic liquid is used as extracting solvent of the sulfur species, in a hollow fiber membrane contactor, without co-extracting the other jet-fuel compound. In a second contactor, the ionic liquid is regenerated applying a sweep gas stripping, which allows for its reuse in a closed loop between the two membrane contactors. This integrated extraction/regeneration process of desulfurization produced a jet-fuel model with sulfur content lower than 2 ppm of S, as envisaged by legislation for the use of ultra-low sulfur jet-fuel. This result confirms the high potential for development of ultra-deep desulfurization application.

Loss of Aggressiveness of Phytophthora cinnamomi (Beta-Cinnamomin Silenced Strain) in the Infection of Castanea sativa

Several forest species are severely affected by Phytophthora cinnamomi. The contribution of this oomycete to forest decline and dieback has been broadly reported. In particular, it is consensual that it is the causal agent of ink disease in Castanea sativa. It has been associated with the severe decline of Quercus species, namely the Q. suber and Q. ilex dieback in Portugal and Spain, and has been responsible for the infection of numerous native species and crops. This pathogen persists in the soil or on plant material in the form of chlamydospores allowing the infection of living root tissues when environmental conditions are favorable. © Microscopy Society of America 2012.

Loss of Par3 leads to aberrant divisions and faster mitotic progression in differentiating primary murine keratinocytes

Dissertação de Mestrado, Oncobiologia: Mecanismos Moleculares do Cancro, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

AB1258­HPR pilot study: does a mediterranean diet­based weight loss programme improve health outcomes in overweight older women with knee osteoarthritis?

Osteoarthritis (OA) is one of the leading causes of pain and disability among older adults, particularly women. Pain and mobility disability are major consequences of knee OA which and can interfere with the functional autonomy of elderly and thus, making it difficult to perform activities of daily living. Evidence suggests that obesity is strongly linked to knee OA and that non­pharmacological therapy should be based on physical activity and weight loss in case of overweight and obesity. A positive relationship between adherence to the Mediterranean diet and health outcomes has been widely discussed in scientific literature, including its potential benefits in weight loss.

Evolution of the rbcS gene family in Solanaceae: concerted evolution and gain and loss of introns, with a description of new statistical guidelines for determining the number of unique gene copies.

Thesis (Ph.D.)--University of Washington, 2014

Deciphering the mechanisms underlying the loss of BDNF neuroprotection in an Alzheimer’s disease model

Tese de mestrado, Neurociências, Faculdade de Medicina, Universidade de Lisboa, 2016

LMP based bid formation for virtual power players operating in smart grids

Power system organization has gone through huge changes in the recent years. Significant increase in distributed generation (DG) and operation in the scope of liberalized markets are two relevant driving forces for these changes. More recently, the smart grid (SG) concept gained increased importance, and is being seen as a paradigm able to support power system requirements for the future. This paper proposes a computational architecture to support day-ahead Virtual Power Player (VPP) bid formation in the smart grid context. This architecture includes a forecasting module, a resource optimization and Locational Marginal Price (LMP) computation module, and a bid formation module. Due to the involved problems characteristics, the implementation of this architecture requires the use of Artificial Intelligence (AI) techniques. Artificial Neural Networks (ANN) are used for resource and load forecasting and Evolutionary Particle Swarm Optimization (EPSO) is used for energy resource scheduling. The paper presents a case study that considers a 33 bus distribution network that includes 67 distributed generators, 32 loads and 9 storage units.

Lubrificação de compressores que aspiram fluido frigorigéneo a temperaturas inferiores a -30° C

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

Detecção de sectores cruzados e optimização de cobertura em redes LTE

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia de Electrónica e Telecomunicações

A traffic differentiation add-on to the IEEE 802.15.4 protocol: implementation and experimental validation over a real-time operating system

The IEEE 802.15.4 is the most widespread used protocol for Wireless Sensor Networks (WSNs) and it is being used as a baseline for several higher layer protocols such as ZigBee, 6LoWPAN or WirelessHART. Its MAC (Medium Access Control) supports both contention-free (CFP, based on the reservation of guaranteed time-slots GTS) and contention based (CAP, ruled by CSMA/CA) access, when operating in beacon-enabled mode. Thus, it enables the differentiation between real-time and best-effort traffic. However, some WSN applications and higher layer protocols may strongly benefit from the possibility of supporting more traffic classes. This happens, for instance, for dense WSNs used in time-sensitive industrial applications. In this context, we propose to differentiate traffic classes within the CAP, enabling lower transmission delays and higher success probability to timecritical messages, such as for event detection, GTS reservation and network management. Building upon a previously proposed methodology (TRADIF), in this paper we outline its implementation and experimental validation over a real-time operating system. Importantly, TRADIF is fully backward compatible with the IEEE 802.15.4 standard, enabling to create different traffic classes just by tuning some MAC parameters.

Experimental measuring procedure for the friction torque in rolling bearings

The reduction of the power loss generated in mechanical transmissions and the use of low friction biodegradable lubricants has been attracting considerable attention in recent times. Therefore, it is necessary to develop methods to test and evaluate the performance of such lubricants and compare them with conventional ones. In this sense, a Four-Ball Machine was modified allowing the test of rolling bearings. A 51107 thrust ball bearing was used to test two different greases and the corresponding base oils. Friction torque and operating temperatures were continuously monitored to quantify the power loss and the heat evacuation for each lubricant tested. Copyright © 2010 John Wiley & Sons, Ltd.

Low-loss austempered ductile iron gears: experimental evaluation comparing materials and lubricants

An experimental study to evaluate the power dissipation of gears was performed. Three low-loss gear models were manufactured using standard 20° pressure angle tools. Austempered ductile iron (ADI) and 20MnCr5 carburized steel gears were tested in an FZG gear test machine using mineral, ester and polyalphaolephine (PAO)-based oils. The results compare power dissipation, the influence of different tooth flank geometries, materials and lubricants. This work concludes that conventional power-transmission gears can be replaced by these improved and more efficient low–loss models, which can be produced using common tools and that steel gears can be successfully replaced by austempered ductile iron gears.