Thick-microstructures for MPGDs: simulations and experimental studies

Cherenkov Imaging counters require large photosensitive areas, capable of single photon detection, operating at stable high gains under radioactive backgrounds while standing high rates, providing a fast response and a good time resolution, and being insensitive to magnetic fields. The development of photon detectors based in Micro Pattern Gaseous detectors (MPGDs), represent a new generation of gaseous photon detectors. In particular, gaseous detectors based on stacked Thick-Gaseous Electron Multipliers (THGEMs), or THGEM based structures, coupled to a CsI photoconverter coating, seem to fulfil the requirements imposed by Cherenkov imaging counters. This work focus on the study of the THGEM-based detectors response as function of its geometrical parameters and applied voltages and electric fields, aiming a future upgrade of the Cherenkov Imaging counter RICH-1 of the COMPASS experiment at CERN SPS. Further studies to decrease the fraction of ions that reach the photocathode (Ion Back Flow – IBF) to minimize the ageing and maximize the photoelectron extraction are performed. Experimental studies are complemented with simulation results, also perfomed in this work.

Wind energy resource modelling in Portugal and its future large-scale alteration due to anthropogenic induced climate changes

The high dependence of Portugal from foreign energy sources (mainly fossil fuels), together with the international commitments assumed by Portugal and the national strategy in terms of energy policy, as well as resources sustainability and climate change issues, inevitably force Portugal to invest in its energetic self-sufficiency. The 20/20/20 Strategy defined by the European Union defines that in 2020 60% of the total electricity consumption must come from renewable energy sources. Wind energy is currently a major source of electricity generation in Portugal, producing about 23% of the national total electricity consumption in 2013. The National Energy Strategy 2020 (ENE2020), which aims to ensure the national compliance of the European Strategy 20/20/20, states that about half of this 60% target will be provided by wind energy. This work aims to implement and optimise a numerical weather prediction model in the simulation and modelling of the wind energy resource in Portugal, both in offshore and onshore areas. The numerical model optimisation consisted in the determination of which initial and boundary conditions and planetary boundary layer physical parameterizations options provide wind power flux (or energy density), wind speed and direction simulations closest to in situ measured wind data. Specifically for offshore areas, it is also intended to evaluate if the numerical model, once optimised, is able to produce power flux, wind speed and direction simulations more consistent with in situ measured data than wind measurements collected by satellites. This work also aims to study and analyse possible impacts that anthropogenic climate changes may have on the future wind energetic resource in Europe. The results show that the ECMWF reanalysis ERA-Interim are those that, among all the forcing databases currently available to drive numerical weather prediction models, allow wind power flux, wind speed and direction simulations more consistent with in situ wind measurements. It was also found that the Pleim-Xiu and ACM2 planetary boundary layer parameterizations are the ones that showed the best performance in terms of wind power flux, wind speed and direction simulations. This model optimisation allowed a significant reduction of the wind power flux, wind speed and direction simulations errors and, specifically for offshore areas, wind power flux, wind speed and direction simulations more consistent with in situ wind measurements than data obtained from satellites, which is a very valuable and interesting achievement. This work also revealed that future anthropogenic climate changes can negatively impact future European wind energy resource, due to tendencies towards a reduction in future wind speeds especially by the end of the current century and under stronger radiative forcing conditions.

Valorization of solid wastes from cellulose and paper industry

This thesis reports in detail studies of industrial solid wastes valorization as alternative raw materials. All tested wastes are classified as non-hazardous and are generated in the pulp and paper process, including primary sludge, dregs, grits, lime mud and bottom ash (this generated in a process that occurs in parallel to the production of cellulose, whose aim is the production of energy to supply the plant through the combustion of forest biomass in fluidized bed). A detailed general characterization was performed at each waste and according to their characteristics, they were selected some applications in materials with potential use, specifically in Fibercement, Bituminous Mixture for regularization layer and industrial mortars (rendering mortars and cementitious-adhesive). After decided to application each waste was specifically tested to proceed the setting up of formulations containing different content of waste in replacement of the raw conventional material. As an isolated case, the bottom ash was tested not only as an alternative raw material for construction materials, but also it was tested for its use in fluidized bed in which the waste is generated as raw material. Both dregs and bottom ash had undergone special treatment to make possible to obtain a better quality of waste in order do not compromise the final product characteristics and process. The dregs were tested in bituminous mixtures as received and also washed (on the laboratory scale to remove soluble salts) and bottom ash were washed and screened in industrial scale (for removal of soluble salts, especially chlorides and coarse fraction particles elimination - particles larger than 1 mm size). The remaining residues form used in such as received avoiding additional costs. The results indicated potential and some limitations for each application to the use of these wastes as alternative raw material, but in some cases, the benefits in relation to valorization overlap with its limitations in both aspects, environmental and economic.

Materials and concepts for CO2 lean ironmaking by pyroelectrolysis

The main purpose of this PhD thesis was to provide convincing demonstration for a breakthrough concept of pyroelectrolysis at laboratory scale. One attempted to identify fundamental objections and/or the most critical constraints, to propose workable concepts for the overall process and for feasible electrodes, and to establish the main requirements on a clearer basis. The main effort was dedicated to studying suitable anode materials to be developed for large scale industrial units with molten silicate electrolyte. This concept relies on consumable anodes based on iron oxides, and a liquid Fe cathode, separated from the refractory materials by a freeze lining (solid) layer. In addition, one assessed an alternative concept of pyroelectrolysis with electron blocking membranes, and developed a prototype at small laboratory scale. The main composition of the molten electrolyte was based on a magnesium aluminosilicate composition, with minimum liquidus temperature, and with different additions of iron oxide. One studied the dynamics of devitrification of these melts, crystallization of iron oxides or other phases, and Fe2+/Fe3+ redox changes under laser zone melting, at different pulling rates. These studies were intended to provide guidelines for dissolution of raw materials (iron oxides) in the molten electrolyte, to assess compatibility with magnetite based consumable anodes, and to account for thermal gradients or insufficient thermal management in large scale cells. Several laboratory scale prototype cells were used to demonstrate the concept of pyroelectrolysis with electron blocking, and to identify the most critical issues and challenges. Operation with and without electron blocking provided useful information on transport properties of the molten electrolyte (i.e., ionic and electronic conductivities), their expected dependence on anodic and cathodic overpotentials, limitations in faradaic efficiency, and onset of side electrochemical reactions. The concept of consumable anodes was based on magnetite and derived spinel compositions, for their expected redox stability at high temperatures, even under oxidising conditions. Spinel compositions were designed for prospective gains in refractoriness and redox stability in wider ranges of conditions (T, pO2 and anodic overpotentials), without excessive penalty for electrical conductivity, thermomechanical stability or other requirements. Composition changes were also mainly based on components of the molten aluminosilicate melt, to avoid undue contamination and to minimize the dissolution rate of consumable anodes. Additional changes in composition were intended for prospective pyroelectrolysis of Fe alloys, with additions of different elements (Cr, Mn, Ni, Ti).

Seamless integration of heterogeneous networks in multicast environments

Nowadays, communication environments are already characterized by a myriad of competing and complementary technologies that aim to provide an ubiquitous connectivity service. Next Generation Networks need to hide this heterogeneity by providing a new abstraction level, while simultaneously be aware of the underlying technologies to deliver richer service experiences to the end-user. Moreover, the increasing interest for group-based multimedia services followed by their ever growing resource demands and network dynamics, has been boosting the research towards more scalable and exible network control approaches. The work developed in this Thesis enables such abstraction and exploits the prevailing heterogeneity in favor of a context-aware network management and adaptation. In this scope, we introduce a novel hierarchical control framework with self-management capabilities that enables the concept of Abstract Multiparty Trees (AMTs) to ease the control of multiparty content distribution throughout heterogeneous networks. A thorough evaluation of the proposed multiparty transport control framework was performed in the scope of this Thesis, assessing its bene ts in terms of network selection, delivery tree recon guration and resource savings. Moreover, we developed an analytical study to highlight the scalability of the AMT concept as well as its exibility in large scale networks and group sizes. To prove the feasibility and easy deployment characteristic of the proposed control framework, we implemented a proof-of-concept demonstrator that comprehends the main control procedures conceptually introduced. Its outcomes highlight a good performance of the multiparty content distribution tree control, including its local and global recon guration. In order to endow the AMT concept with the ability to guarantee the best service experience by the end-user, we integrate in the control framework two additional QoE enhancement approaches. The rst employs the concept of Network Coding to improve the robustness of the multiparty content delivery, aiming at mitigating the impact of possible packet losses in the end-user service perception. The second approach relies on a machine learning scheme to autonomously determine at each node the expected QoE towards a certain destination. This knowledge is then used by di erent QoE-aware network management schemes that, jointly, maximize the overall users' QoE. The performance and scalability of the control procedures developed, aided by the context and QoE-aware mechanisms, show the advantages of the AMT concept and the proposed hierarchical control strategy for the multiparty content distribution with enhanced service experience. Moreover we also prove the feasibility of the solution in a practical environment, and provide future research directions that bene t the evolved control framework and make it commercially feasible.

Surface reactivity enhancement of silica-based glass-ceramic scaffolds

A paradigm shift is taking place from using transplanting tissue and synthetic implants to a tissue engineering approach that aims to regenerate damaged tissues by combining cells from the body with highly porous scaffold biomaterials, which act as templates, guiding the growth of new tissue. The central focus of this thesis was to produce porous glass and glass-ceramic scaffolds that exhibits a bioactive and biocompatible behaviour with specific surface reactivity in synthetic physiological fluids and cell-scaffold interactions, enhanced by composition and thermal treatments applied. Understanding the sintering behaviour and the interaction between the densification and crystallization processes of glass powders was essential for assessing the ideal sintering conditions for obtaining a glass scaffolds for tissue engineering applications. Our main goal was to carry out a comprehensive study of the bioactive glass sintering, identifying the powder size and sintering variables effect, for future design of sintered glass scaffolds with competent microstructures. The developed scaffolds prepared by the salt sintering method using a 3CaO.P2O5 - SiO2 - MgO glass system, with additions of Na2O with a salt, NaCl, exhibit high porosity, interconnectivity, pore size distribution and mechanical strength suitable for bone repair applications. The replacement of 6 % MgO by Na2O in the glass network allowed to tailor the dissolution rate and bioactivity of the glass scaffolds. Regarding the biological assessment, the incorporation of sodium to the composition resulted in an inibition cell response for small periods. Nevertheless it was demonstrated that for 21 days the cells response recovered and are similar for both glass compositions. The in vitro behaviour of the glass scaffolds was tested by introducing scaffolds to simulated body fluid for 21 days. Energy-dispersive Xray spectroscopy and SEM analyses proved the existence of CaP crystals for both compositions. Crystallization forming whitlockite was observed to affect the dissolution behaviour in simulated body fluid. By performing different heat treatments, it was possible to control the bioactivity and biocompatability of the glass scaffolds by means of a controlled crystallization. To recover and tune the bioactivity of the glass-ceramic with 82 % crystalline phase, different methods have been applied including functionalization using 3- aminopropyl-triethoxysilane (APTES). The glass ceramic modified surface exhibited an accelerated crystalline hydroxyapatite layer formation upon immersion in SBF after 21 days while the as prepared glass-ceramic had no detected formation of calcium phosphate up to 5 months. A sufficient mechanical support for bone tissue regeneration that biodegrade later at a tailorable rate was achievable with the glass–ceramic scaffold. Considering the biological assessment, scaffolds demonstrated an inductive effect on the proliferation of cells. The cells showed a normal morphology and high growth rate when compared to standard culture plates. This study opens up new possibilities for using 3CaO.P2O5–SiO2–MgO glass to manufacture various structures, while tailoring their bioactivity by controlling the content of the crystalline phase. Additionally, the in vitro behaviour of these structures suggests the high potential of these materials to be used in the field of tissue regeneration.

Extension of electrochemically active sites in SOFCs and SOECs

Solid oxide fuel (SOFCs) and electrolyzer (SOECs) cells have been promoted as promising technologies for the stabilization of fuel supply and usage in future green energy systems. SOFCs are devices that produce electricity by the oxidation of hydrogen or hydrocarbon fuels with high efficiency. Conversely, SOECs can offer the reverse reaction, where synthetic fuels can be generated by the input of renewable electricity. Due to this similar but inverse nature of SOFCs and SOECs, these devices have traditionally been constructed from comparable materials. Nonetheless, several limitations have hindered the entry of SOFCs and SOECs into the marketplace. One of the most debilitating is associated with chemical interreactions between cell components that can lead to poor longevities at high working temperatures and/or depleted electrochemcial performance. Normally such interreactions are countered by the introduction of thin, purely ionic conducting, buffer layers between the electrode and electrolyte interface. The objective of this thesis is to assess if possible improvements in electrode kinetics can also be obtained by modifying the transport properties of these buffer layers by the introduction of multivalent cations. The introduction of minor electronic conductivity in the surface of the electrolyte material has previously been shown to radically enhance the electrochemically active area for oxygen exchange, reducing polarization resistance losses. Hence, the current thesis aims to extend this knowledge to tailor a bi-functional buffer layer that can prevent chemical interreaction while also enhancing electrode kinetics.The thesis selects a typical scenario of an yttria stabilized zirconia electrolyte combined with a lanthanide containing oxygen electrode. Gadolinium, terbium and praseodymium doped cerium oxide materials have been investigated as potential buffer layers. The mixed ionic electronic conducting (MIEC) properties of the doped-cerium materials have been analyzed and collated. A detailed analysis is further presented of the impact of the buffer layers on the kinetics of the oxygen electrode in SOFC and SOEC devices. Special focus is made to assess for potential links between the transport properties of the buffer layer and subsequent electrode performance. The work also evaluates the electrochemical performance of different K2NiF4 structure cathodes deposited onto a peak performing Pr doped-cerium buffer layer, the influence of buffer layer thickness and the Pr content of the ceria buffer layer. It is shown that dramatic increases in electrode performance can be obtained by the introduction of MIEC buffer layers, where the best performances are shown to be offered by buffer layers of highest ambipolar conductivity. These buffer layers are also shown to continue to offer the bifunctional role to protect from unwanted chemical interactions at the electrode/electrolyte interface.

Oxidation and glycoxidation of phosphatidylserine and their effect in immune response : a lipidomic approach

Phosphatidylserine (PS) is a member of the class of phospholipids, and is distributed among all cells of mammalians, playing important roles in diverse biological processes, including blood clotting and apoptosis. When externalized, PS is a ligand that is recognized on apoptotic cells. It has been considered that before externalization PS is oxidized and oxPS enhance the recognition by macrophages receptors, however the knowledge about oxidation of PS is still limited. PS, like others phospholipids, has two fatty acyl chains and one polar head group, in this case is the amino acid serine. The modifications in PS structure can occur by oxidation of the unsaturated fatty acyl chains and by glycation of the polar head group, due to free amine group, thus increasing the susceptibility to oxidative events. The main goal of this work was to characterize and identify oxidized and glycoxidized PS, contributing to the knowledge of the biological role of oxidation products of PS, as well as of glycated PS, in immune and inflammatory processes. To achieve this goal, PS standards (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho- L-serine (POPS), 1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine (DPPS), 1- palmitoyl-2-linoleoyl-sn-glycero-3-phospho-L-serine (PLPS) and 1-palmitoyl-2- arachidonoyl-sn-glycero-3-phospho-L-serine (PAPS)) and glycated PS (PAPS and POPS) were induced to oxidize in model systems, using different oxidant reagents: HO• and 2,2'-azobis-2-methyl-propanimidamide dihydrochloride (AAPH) . The detailed structural characterization of the oxidative products was performed by ESI-MS and MS/MS coupled to separation techniques such as off line TLC-MS and on line LC-MS, in order to obtained better characterization of the larger number of PS and glycated PS oxidation products. The results obtained in this work allowed to identify several oxidation products of PS and glycated PS with modifications in unsaturated fatty acyl chain. Also, oxidation products formed due to structural changes in the serine polar head with formation of terminal acetamide, terminal hydroperoxyacetaldehyde.and terminal acetic acid (glycerophosphacetic acid, GPAA) were identified. The mass spectrometric specific fragmentation pathway of each type of oxidation product was determined using different mass spectrometry approaches. Based on the identified fragmentation pathways, targeted lipidomic analysis was performed to detect oxidation products modified in serine polar head in HaCaT cell line treated with AAPH. The GPAA was detected in HaCaT cells treated with AAPH to induce oxidative stress, thus confirming that modifications in PS polar head is possible to occur in biological systems. Furthermore, it was found that glycated PS species are more prone to oxidative modifications when compared with non glycated PS. During oxidation of glycated PS, besides the oxidation in acyl chains, new oxidation products due to oxidation of the glucose moiety were identified, including PS advanced glycation end products (PSAGES). To investigate if UVA oxidative stress exerted changes in the lipidome of melanoma cell lines, particularly in PS profile, a lipidomic analysis was performed. The lipid profile was obtained using HILIC-LC-MS and GC-MS analysis of the total lipid extracts obtained from human melanoma cell line (SKMEL- 28) after UVA irradiation at 0, 2 and 24 hours. The results did not showed significant differences in PS content. At molecular level, only PS (18:0:18:1) decreased at the moment of irradiation. The most significant changes in phospholipids content occurred in phosphatidylcholines (PC) and phosphatidylinositol (PI) classes, with an increase of mono-unsaturated fatty acid (MUFA), similarly as observed for the fatty acid analysis. Overall, these data indicate that the observed membrane lipid changes associated with lipogenesis after UVA exposure may be correlated with malignant transformations associated with cancer development and progression. Despite of UVA radiation is associated with oxidative damage, in this work was not possible observe oxidation phospholipids. The anti/pro-inflammatory properties of the oxidized PLPS (oxPLPS) versus non-oxidized PLPS were tested on LPS stimulated RAW 264.7 macrophages. The modulation of intracellular signaling pathways such as NF-kB and MAPK cascades by oxPLPS and PS was also examined in this study. The results obtained from evaluation of anti/pro-inflammatory properties showed that neither PLPS or oxPLPS species activated the macrophages. Moreover only oxidized PLS were found to significantly inhibit NO production and iNOS and il1β gene transcription induced by LPS. The analysis at molecular level showed that this was the result of the attenuation of LPS-induced c-Jun-N-terminal kinase (JNK) and p65 NF-kB nuclear translocation. Overall these data suggest that oxPLPS, but not native PLPS, mitigates pro-inflammatory signaling in macrophages, contributing to containment of inflammation during apoptotic cell engulfment. The results obtained in this work provides new information on the modifications of PS, facilitating the identification of oxidized species in complex samples, namely under physiopathologic conditions and also contributes to a better understanding of the role of oxPS and PS in the inflammatory response, in the apoptotic process and other biological functions.

Alkaline-earth aluminosilicate-based glass and glass-ceramic sealants for functional applications

The planar design of solid oxide fuel cell (SOFC) is the most promising one due to its easier fabrication, improved performance and relatively high power density. In planar SOFCs and other solid-electrolyte devices, gas-tight seals must be formed along the edges of each cell and between the stack and gas manifolds. Glass and glass-ceramic (GC), in particular alkaline-earth alumino silicate based glasses and GCs, are becoming the most promising materials for gas-tight sealing applications in SOFCs. Besides the development of new glass-based materials, new additional concepts are required to overcome the challenges being faced by the currently existing sealant technology. The present work deals with the development of glasses- and GCs-based materials to be used as a sealants for SOFCs and other electrochemical functional applications. In this pursuit, various glasses and GCs in the field of diopside crystalline materials have been synthesized and characterized by a wide array of techniques. All the glasses were prepared by melt-quenching technique while GCs were produced by sintering of glass powder compacts at the temperature ranges from 800−900 ºC for 1−1000 h. Furthermore, the influence of various ionic substitutions, especially SrO for CaO, and Ln2O3 (Ln=La, Nd, Gd, and Yb), for MgO + SiO2 in Al-containing diopside on the structure, sintering and crystallization behaviour of glasses and properties of resultant GCs has been investigated, in relevance with final application as sealants in SOFC. From the results obtained in the study of diopside-based glasses, a bilayered concept of GC sealant is proposed to overcome the challenges being faced by (SOFCs). The systems designated as Gd−0.3 (in mol%: 20.62MgO−18.05CaO−7.74SrO−46.40SiO2−1.29Al2O3 − 2.04 B2O3−3.87Gd2O3) and Sr−0.3 (in mol%: 24.54 MgO−14.73 CaO−7.36 SrO−0.55 BaO−47.73 SiO2−1.23 Al2O3−1.23 La2O3−1.79 B2O3−0.84 NiO) have been utilized to realize the bi-layer concept. Both GCs exhibit similar thermal properties, while differing in their amorphous fractions, revealed excellent thermal stability along a period of 1,000 h. They also bonded well to the metallic interconnect (Crofer22APU) and 8 mol% yttrium stabilized zirconium (8YSZ) ceramic electrolyte without forming undesirable interfacial layers at the joints of SOFC components and GC. Two separated layers composed of glasses (Gd−0.3 and Sr−0.3) were prepared and deposited onto interconnect materials using a tape casting approach. The bi-layered GC showed good wetting and bonding ability to Crofer22APU plate, suitable thermal expansion coefficient (9.7–11.1 × 10–6 K−1), mechanical reliability, high electrical resistivity, and strong adhesion to the SOFC componets. All these features confirm the good suitability of the investigated bi-layered sealant system for SOFC applications.

Controle activo de estruturas adaptativas com sensores e actuadores piezoeléctricos

Nos últimos anos o estudo de estruturas inteligentes tem atraído vários investigadores devido às suas potenciais vantagens numa larga gama de aplicações, tais como controle de forma, supressão de vibrações, atenuação de ruído e detecção de dano. O uso de materiais “inteligentes” tal como os materiais piezoeléctricos na forma de lâminas ou “patches”, embebidas ou coladas na superfície de estruturas construídas de materiais compósitos, permite assim obter estruturas que por um lado são adaptativas e por outro revelam excelentes propriedades mecânicas, aumentando assim bastante o desempenho e a fiabilidade de sistemas estruturais. Os materiais piezoeléctricos têm a propriedade de gerar uma carga eléctrica sob a acção duma carga mecânica e o reverso, isto é, aplicando um campo eléctrico nos elementos piezoeléctricos da estrutura, esta deforma-se. Neste trabalho, é apresentado um modelo de elementos finitos, baseado na teoria clássica de placas, desenvolvido para a análise do controle activo em estática e dinâmica lineares de estruturas integrando sensores e actuadores piezoeléctrico na forma de lâminas, os quais introduzem um grau de liberdade referente ao potencial eléctrico, por cada camada piezoeléctrica do elemento finito. É utilizado método de Newmark para a solução iterativa das equações de equilíbrio. Apresentam-se os resultados obtidos em três exemplos ilustrativos.

Optimização de estruturas laminadas adaptativas com controlo activo

Neste trabalho apresenta-se um modelo de elementos finitos, baseados na teoria clássica das placas, desenvolvido para a análise de controlo activo em dinâmica de estruturas de tipo placa/casca integrando sensores e actuadores piezoeléctricos. O controlo é iniciado através de uma optimização prévia do núcleo laminado de modo a diminuir a amplitude da vibração. É usado um algoritmo de controlo baseado na ligação entre as lâminas piezoeléctricas sensoras e actuadoras para obter um mecanismo de controlo da resposta dinâmica da estrutura. A resolução por elementos finitos usa um elemento placa/casca triangular plano de 3 nós, e em cuja formulação se introduz um grau de liberdade referente ao potencial eléctrico, por cada camada piezoeléctrica do elemento finito. Apresentam-se os resultados obtidos em dois exemplos ilustrativos.

Optimização de painéis laminados com furos

Neste trabalho é feita a optimização de estruturas laminadas do tipo placa-casca, construídas por materiais compósitos, fazendo-se uso de um modelo discreto baseado na Teoria de Kirchhoff em conjugação com a Teoria da Camada Única Equivalente.As análises estrutural e de sensibilidades de estruturas em regime estático com comportamento geometricamente não linear, em vibrações livres, e em estabilidade linear, são desenvolvidas para um elemento finito triangular plano de 3 nós, com 18 graus de liberdade. A optimização é feita considerando diferentes funções objectivo, tais como a maximização da energia elástica de deformação, a maximização da frequência fundamental e a maximização da carga crítica, e é baseada no método das sensibilidades. As sensibilidades destas funções objectivo em ordem ás variáveis de projeto são calculadas analíticamente, sendo a orientação das fibras as variáveis de projecto consideradas.

Análise geometricamente não-linear de estruturas adaptativas piezolaminadas

Neste trabalho apresenta-se um modelo de elementos finitos, baseado na teoria clássica de placas, para a análise linear e não-linear de estruturas do tipo placa/casca integrando sensores e actuadores piezoeléctricos. É usado um simples e eficiente elemento placa/casca triangular plano de 3 nós, e em cuja formulação se introduz um grau de liberdade referente ao potencial eléctrico, por cada camada piezoeléctrica do elemento finito. É utilizada a formulação Lagrangeana actualizada associada à tecnica de Newton - Raphson para a solução iterativa das equações de equilibrio .O modelo pode ser aplicado a cascas piezolaminadas com geometria e carregamento arbitrários. Apresentam-se vários exemplos ilustrativos cujos resultados mostram a eficiencia do modelo proposto.

Placas elasto-electro-magnéticas

Neste trabalho apresenta-se um modelo de elementos finitos, baseado na teoria clássica de placas, para a análise linear e não-linear de estruturas do tipo placa/casca integrando sensores e actuadores piezoeléctricos. É usado um simples e eficiente elemento placa/casca triangular plano de 3 nós, e em cuja formulação se introduz um grau de liberdade referente ao potencial eléctrico, por cada camada piezoeléctrica do elemento finito. É utilizada a formulação Lagrangeana actualizada associada à tecnica de Newton - Raphson para a solução iterativa das equações de equilibrio .O modelo pode ser aplicado a cascas piezolaminadas com geometria e carregamento arbitrários. Apresentam-se vários exemplos ilustrativos cujos resultados mostram a eficiencia do modelo proposto.

Influência de marés na distribuição vertical de larvas de peixes de recifes costeiros e escolha de substratos de assentamento no Parque Marinho Luíz Saldanha

Dissertação mest., Biologia Marinha, Universidade do Algarve, 2009