Desenvolvimento e estudo de modelos de FACTS para o trânsito de energia: aplicação ao estudo das condições técnicas de ligação de linhas MAT

Dissertação para obtenção do grau de Mestre em Engenharia Electrotécnica Ramo de Energia

Caracterização da remoção de metais pesados na ETAR da Charneca (Óbidos), Águas do Oeste

Este trabalho teve como objectivos a quantificação analítica de quatro metais pesados (chumbo, níquel, crómio e cádmio) nas diferentes etapas da ETAR da Charneca (Óbidos) identificando, através dos coeficientes de partição, os principais mecanismos de remoção dos metais em cada etapa de tratamento. Foram também determinados os parâmetros mais importantes na caracterização de águas residuais (pH, CQO, ST, STV, SS e SSV). Foram realizadas duas campanhas de amostragem, uma primeira com o objectivo de aperfeiçoamento dos planos de amostragem e selecção dos métodos analíticos a adoptar e uma segunda para o cumprimento dos objectivos do trabalho. A determinação de metais pesados foi efectuada por Espectrometria de Absorção Atómica de Chama (FAAS) e Espectrometria de Absorção Atómica de Câmara de Grafite (GFAAS). Os restantes parâmetros analíticos foram determinados pelos métodos de referência (APHA, 1998). No período de amostragem, o afluente à ETAR apresentou concentrações reduzidas dos metais em estudo com valores médios de 11,78 µg/L. De entre os metais destacavam-se, no entanto, o crómio e de níquel, com concentrações respectivamente 27,83 µg/L e 17,50 µg/L. As amostras de areias, extraídas na obra de entrada, apresentaram concentrações mais significativas de chumbo e crómio, enquanto as amostras de gorduras, recolhidas no mesmo ponto, apresentaram concentrações mais elevadas de níquel e crómio. As amostras do efluente final revelaram concentrações muito reduzidas dos quatro metais estudados com a concentração média a situar-se nos 7,34 µg/L. Verificou-se uma remoção na fase líquida do efluente de cerca de 85% para o chumbo, 39% para o níquel e 34% para o crómio. No cádmio não se verificou remoção na fase líquida. Concluiu-se que a remoção dos metais é determinada por uma transferência destes para a fase sólida e que ocorre fundamentalmente no reactor biológico onde uma parte significativa dos metais pesados é absorvida pela biomassa presente. Nas lamas desidratadas, os metais encontrados em maior concentração foram o chumbo e o crómio com concentrações de respectivamente 130,64 mg/Kgmat.seca e 87,99 mg/Kg mat.seca, embora todos os metais pesados estudados apresentem uma situação de conformidade com os requisitos de lamas para valorização agrícola, estabelecidos na legislação nacional.

Caracterização de regiões encefálicas no cérebro normal por tensor de difusão e aplicação à epilepsia pós-traumática

Mestrado em Radiações Aplicadas às Tecnologias da Saúde.

Perspectives on the electrically induced properties of electrospun cellulose/liquid crystal devices

A mat of electrospun cellulose fibers are deposed on transparent conductive oxide covered glass, and two such plates enclose a nematic liquid crystal. Thus two new types of Cellulose based Polymer Dispersed Liquid Crystal devices, based on hydroxypropylcellulose and Cellulose Acetate and the nematic liquid crystal E7 have been obtained. The current-voltage characteristics indicates ionic type conduction. Heating-cooling cycles have been applied on the samples and the activation energies have been determined. Simultaneously with the thermo-stimulated currents, the optical transmission dependence on the d.c. electric field and temperature was registered. ON-OFF switching times have been determined for different control voltages. (C) 2011 Elsevier B.V. All rights reserved.

Surgical proven location of the facial nerve in the vicinity of cerebellopontine angle tumours depicted pre-operatively by tractography

Purpose/Introduction: To determine the clinical utility of pre-operative diffusion tensor (DT) tractography of the facial nerve in the vicinity of cerebellopontine angle (CPA) tumours. The location of the facial nerve was established pre-operatively by tractography and compared with in-vivo electrode stimulation during microsurgery of vestibular schwannomas and rare CPA masses (meningiomas and arachnoid cysts).

Dynamical analysis in growth models: Blumberg’s equation

We present a new dynamical approach to the Blumberg's equation, a family of unimodal maps. These maps are proportional to Beta(p, q) probability densities functions. Using the symmetry of the Beta(p, q) distribution and symbolic dynamics techniques, a new concept of mirror symmetry is defined for this family of maps. The kneading theory is used to analyze the effect of such symmetry in the presented models. The main result proves that two mirror symmetric unimodal maps have the same topological entropy. Different population dynamics regimes are identified, when the intrinsic growth rate is modified: extinctions, stabilities, bifurcations, chaos and Allee effect. To illustrate our results, we present a numerical analysis, where are demonstrated: monotonicity of the topological entropy with the variation of the intrinsic growth rate, existence of isentropic sets in the parameters space and mirror symmetry.

An Extension of Gompertzian Growth Dynamics Weibull and Frechet Models

In this work a new probabilistic and dynamical approach to an extension of the Gompertz law is proposed. A generalized family of probability density functions, designated by Beta* (p, q), which is proportional to the right hand side of the Tsoularis-Wallace model, is studied. In particular, for p = 2, the investigation is extended to the extreme value models of Weibull and Frechet type. These models, described by differential equations, are proportional to the hyper-Gompertz growth model. It is proved that the Beta* (2, q) densities are a power of betas mixture, and that its dynamics are determined by a non-linear coupling of probabilities. The dynamical analysis is performed using techniques of symbolic dynamics and the system complexity is measured using topological entropy. Generally, the natural history of a malignant tumour is reflected through bifurcation diagrams, in which are identified regions of regression, stability, bifurcation, chaos and terminus.

Development of an injectable grout for concrete repair and strengthening

This paper deals with the coupled effect of temperature and silica fume addition on rheological, mechanical behaviour and porosity of grouts based on CEMI 42.5R, proportioned with a polycarboxylate-based high range water reducer. Preliminary tests were conducted to focus on the grout best able to fill a fibrous network since the goal of this study was to develop an optimized grout able to be injected in a mat of steel fibers for concrete strengthening. The grout composition was developed based on criteria for fresh state and hardened state properties. For a CEMI 42.5R based grout different high range water reducer dosages (0%, 0.2%, 0.4%, 0.5%, 0.7%) and silica fume (SF) dosages (0%, 2%, 4%) were tested (as replacement of cement by mass). Rheological measurements were used to investigate the effect of polycarboxylates (PCEs) and SF dosage on grout properties, particularly its workability loss, as the mix was to be injected in a matrix of steel fibers for concrete jacketing. The workability behaviour was characterized by the rheological parameters yield stress and plastic viscosity (for different grout temperatures and resting times), as well as the procedures of mini slump cone and funnel flow time. Then, further development focused only on the best grout compositions. The cement substitution by 2% of SF exhibited the best overall behaviour and was considered as the most promising compared to the others compositions tested. Concerning the fresh state analysis, a significant workability loss was detected if grout temperature increased above 35 degrees C. Below this temperature the grout presented a self-levelling behaviour and a life time equal to 45 min. In the hardened state, silica fumes increased not only the grout's porosity but also the grout's compressive strength at later ages, since the pozzolanic contribution to the compressive strength does not occur until 28 d and beyond. (C) 2012 Elsevier Ltd. All rights reserved.

Strong and weak Allee effects and chaotic dynamics in Richards' growths

In this paper we define and investigate generalized Richards' growth models with strong and weak Allee effects and no Allee effect. We prove the transition from strong Allee effect to no Allee effect, passing through the weak Allee effect, depending on the implicit conditions, which involve the several parameters considered in the models. New classes of functions describing the existence or not of Allee effect are introduced, a new dynamical approach to Richards' populational growth equation is established. These families of generalized Richards' functions are proportional to the right hand side of the generalized Richards' growth models proposed. Subclasses of strong and weak Allee functions and functions with no Allee effect are characterized. The study of their bifurcation structure is presented in detail, this analysis is done based on the configurations of bifurcation curves and symbolic dynamics techniques. Generically, the dynamics of these functions are classified in the following types: extinction, semi-stability, stability, period doubling, chaos, chaotic semistability and essential extinction. We obtain conditions on the parameter plane for the existence of a weak Allee effect region related to the appearance of cusp points. To support our results, we present fold and flip bifurcations curves and numerical simulations of several bifurcation diagrams.

Colloidal interactions in two-dimensional nematics

The interaction between two disks immersed in a 2D nernatic is investigated i) analytically using the tenser order parameter formalism for the nematic configuration around isolated disks and ii) numerically using finite-element methods with adaptive meshing to minimize the corresponding Landau-de Gennes free energy. For strong homeotropic anchoring, each disk generates a pair of defects with one-half topological charge responsible for the 2D quadrupolar interaction between the disks at large distances. At short distance, the position of the defects may change, leading to unexpected complex interactions with the quadrupolar repulsive interactions becoming attractive. This short-range attraction in all directions is still anisotropic. As the distance between the disks decreases, their preferred relative orientation with respect to the far-field nernatic director changes from oblique to perpendicular.

Perceções de doença como determinantes de comportamentos de saúde na asma

Objetivos: Identificar e caracterizar perceções de doença e sua associação com níveis de adesão à terapêutica e controlo da doença na asma. Métodos: Estudo observacional-descritivo transversal cuja amostra é constituída por 33 estudantes asmáticos, de ambos os sexos e idade 18-29 anos (M=20,33; DP=2,04), que completaram o Illness Perception Questionnaire (IPQ-R), a Medida de Adesão aos Tratamentos (MAT) e o Asthma Control Test (ACT). Resultados: A maioria dos indivíduos percepciona a asma como doença crónica, cíclica, que pode ser controlada pela sua acção e/ou tratamento. A maioria apresenta um bom nível de controlo da asma, evidenciando 84,8% uma perceção adequada do controlo da sua doença. Embora apresentem um bom nível de adesão, apenas 28% toma medicação preventiva diariamente, referindo 45,2% já ter interrompido a medicação por se sentir melhor. Foram encontradas correlações significativas entre nível de adesão e perceção de duração cíclica da doença (rs (30)= -0,38; p<0,05), entre perceção de controlo através do tratamento e nível de controlo da doença (rs (33) = 0,386; p<0,05) e entre sintomas e perceção de controlo da doença (rs (33) = 0,737; p<0,01). Conclusões: Os resultados evidenciam o papel das perceções de doença na adoção de comportamentos de saúde na asma, nomeadamente a adesão à terapêutica, que vão traduzir-se no nível de controlo alcançado pelos doentes. Desenvolver intervenções individualizadas, centradas no doente, que contribuam para corrigir crenças inadequadas poderá, pois, potenciar um envolvimento ativo do doente no controlo da sua doença, contribuindo para uma melhoria da sua Qualidade de Vida.

The effects of clinical support surfaces on pressure as a risk factor in the development of pressure ulcers, from a radiographical perspective: a narrative literature review

Purpose: Pressure ulcers are a high cost, high volume issue for health and medical care providers, having a detrimental effect on patients and relatives. Pressure ulcer prevention is widely covered in the literature, but little has been published regarding the risk to patients in the radiographical setting. This review of the current literature is to identify findings relevant to radiographical context. Methods: Literature searching was performed using Science Direct and Medline databases. The search was limited to articles published in the last ten years to remain current and excluded studies containing participants less than 17 years of age. In total 14 studies were acquired; three were excluded as they were not relevant. The remaining 11 studies were compared and reviewed. Discussion: Eight of the studies used ‘healthy’ participants and three used symptomatic participants. Nine studies explored interface pressure with a range of pressure mat technologies, two studies measured shear (MRI finite element modelling, and a non-invasive instrument), and one looked at blood flow and haemoglobin oxygenation. A range of surfaces were considered from trauma, nursing and surgical backgrounds for their ability to reduce pressure including standard mattresses, high specification mattresses, rigid and soft layer spine boards, various overlays (gel, air filled, foam). Conclusion: The current literature is not appropriate for the radiographic patient and cannot be extrapolated to a radiologic context. Sufficient evidence is presented in this review to support the need for further work specific to radiography in order to minimise the development of PU in at risk patients.

Fabrication of the three-dimensional dendritic Ni-Co films by electrodeposition on stainless steel substrates

Co-deposition of nickel and cobalt was carried out on austenitic stainless steel (AISI 304) substrates by imposing a square waveform current in the cathodic region. The innovative procedure applied in this work allows creating a stable, fully developed, and open porous three-dimensional (3D) dendritic structure, which can be used as electrode for redox supercapacitors. This study investigates in detail the influence of the applied current density on the morphology, mass, and chemical composition of the deposited Ni-Co films and the resulting 3D porous network dendritic structure. The morphology and the physicochemical composition were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (W). The electrochemical behavior of the materials was evaluated by cyclic voltammetry (CV). The results highlight the mechanism involved in the coelectrodeposition process and how the lower limit current density tailors the film composition and morphology, as well as its electrochemical activity.

Crossing balanced and stair nested desings

Balanced nesting is the most usual form of nesting and originates, when used singly or with crossing of such sub-models, orthogonal models. In balanced nesting we are forced to divide repeatedly the plots and we have few degrees of freedom for the first levels. If we apply stair nesting we will have plots all of the same size rendering the designs easier to apply. The stair nested designs are a valid alternative for the balanced nested designs because we can work with fewer observations, the amount of information for the different factors is more evenly distributed and we obtain good results. The inference for models with balanced nesting is already well studied. For models with stair nesting it is easy to carry out inference because it is very similar to that for balanced nesting. Furthermore stair nested designs being unbalanced have an orthogonal structure. Other alternative to the balanced nesting is the staggered nesting that is the most popular unbalanced nested design which also has the advantage of requiring fewer observations. However staggered nested designs are not orthogonal, unlike the stair nested designs. In this work we start with the algebraic structure of the balanced, the stair and the staggered nested designs and we finish with the structure of the cross between balanced and stair nested designs.

Generalized models from Beta(p,2) densities with strong allee effect: dynamical approach

A dynamical approach to study the behaviour of generalized populational growth models from Bets(p, 2) densities, with strong Allee effect, is presented. The dynamical analysis of the respective unimodal maps is performed using symbolic dynamics techniques. The complexity of the correspondent discrete dynamical systems is measured in terms of topological entropy. Different populational dynamics regimes are obtained when the intrinsic growth rates are modified: extinction, bistability, chaotic semistability and essential extinction.