Study of AC losses in medium-sized high temperature superconducting coils

The study of AC losses in superconducting pancake coils is of utmost importance for the development of superconducting devices. Due to different technical difficulties this study is usually performed considering one of two approaches: considering superconducting coils of few turns and studying AC losses in a large frequency range vs. superconducting coils with a large number of turns but measuring AC losses only in low frequencies. In this work, a study of AC losses in 128 turn superconducting coils is performed, considering frequencies ranging from 50 Hz till 1152 Hz and currents ranging from zero till the critical current of the coils. Moreover, the study of AC losses considering two different simultaneous harmonic components is also performed and results are compared to the behaviour presented by the coils when operating in a single frequency regime. Different electrical methods are used to verify the total amount of AC losses in the coil and a simple calorimetric method is presented, in order to measure AC losses in a multi-harmonic context. Different analytical and numerical methods are implemented and/or used, to design the superconducting coils and to compute the total amount of AC losses in the superconducting system and a comparison is performed to verify the advantages and drawbacks of each method.

Low-voltage low-power CMOS analogue circuits for Gaussian and uniform noise generation

IEEE International Symposium on Circuits and Systems, MAY 25-28, 2003, Bangkok, Thailand. (ISI Web of Science)

SENSITIVITY ANALYSIS OF TRACK VIBRATIONS DUE TO VERTICAL STIFFNESS VARIATION IN HIGH-SPEED RAILWAYS

High speed trains, when crossing regions with abrupt changes in vertical stiffness of the track and/or subsoil, may generate excessive ground and track vibrations. There is an urgent need for specific analyses of this problem so as to allow reliable esimates of vibration amplitude. Full understanding of these phenomena will lead to new construction solutions and mitigation of undesirable features. In this paper analytical transient solutions of dynamic response of one-dimensional systems with sudden change of foundation stiffness are derived. Results are expressed in terms of vertical displacement. Sensitivity analysis of the response amplitude is also performed. The analytical expressions presented herein, to the authors’ knowledge, have not been published yet. Although related to one-dimensional cases, they can give useful insight into the problem. Nevertheless, in order to obtain realistic response, vehicle- rail interaction cannot be omitted. Results and conclusions are confirmed using general purpose commercial software ANSYS. In conclusion, this work contributes to a better understanding of the additional vibration phenomenon due to vertical stiffness variation, permitting better control of the train velocity and optimization of the track design.

Stochastic modelling of the reservoir lithological and petrophysical attributes. A case study of the Middle East carbonate reservoir

Dissertação para obtenção do Grau de Mestre em Engenharia Geológica (Georrecursos)

Integrating wind generation in the distribution network

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Energias Renováveis – Conversão Eléctrica e Utilização Sustentáveis

Portugal as a country exporting talent: Image of young high-skilled Portuguese people working outside Portugal

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

Experimental high-throughput adsorption unit for multi-evaluation of adsorbents for gas capture, storage and separation applications

Dissertação para obtenção do grau de Mestre em Engenharia Química e Bioquímica

Development of a "green process" for the isolation of natural functional extracts with anti-cancer activity - Application of high-pressure technology

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Phage display as a tool for development of novel therapeutics for breast cancer

Phage display technology is a powerful platform for the generation of highly specific human monoclonal antibodies (Abs) with potential use in clinical applications. Moreover, this technique has also proven to be a reliable approach in identifying and validating new cancer-related targets. For scientific or medical applications, different types of Ab libraries can be constructed. The use of Fab Immune libraries allows the production of high quality and affinity antigen-specific Abs. In this work, two immune human phage display IgG Fab libraries were generated from the Ab repertoire of 16 breast cancer patients, in order to obtain a tool for the development of new therapeutic Abs for breast cancer, a condition that has great impact worldwide. The generated libraries are estimated to contain more than 108 independent clones and a diversity over 90%. Libraries validation was pursued by selection against BSA, a foreign and highly immunogenic protein, and HER2, a well established cancer target. Preliminary results suggested that phage pools with affinity for these antigens were selected and enriched. Individual clones were isolated, however, it was not possible to obtain enough data to further characterize them. Selection against the DLL1 protein was also performed, once it is a known ligand of the Notch pathway, whose deregulation is associated to breast cancer, making it an interesting target for the generation of function-blocking Abs. Selection resulted in the isolation of a clone with low affinity and Fab expression levels. The validation process was not completed and further effort will have to be put in this task in the future. Although immune libraries concept implies limited applicability, the library reported here has a wide range of use possibilities, since it was not restrained to a single antigen but instead thought to be used against any breast cancer associated target, thus being a valuable tool.

Estratégia de vacinação para eliminar o sarampo : um estudo sero-epidemiológico em diferentes populações vacinais

RESUMO - Introdução: As alterações epidemiológicas do sarampo em Portugal, assim como a existência de surtos de doença na Europa e noutras regiões do mundo, associadas ao facto de a informação sero epidemiológica atualizada ser escassa e pontual, e nem sempre estar relacionada com o estado vacinal, dificultam a tomada de decisões fundamentadas na área da vacinação, nomeadamente no que respeita às idades ótimas para a administração de VASPR I e VASPR II. Este estudo pretende avaliar a adequação da estratégia vacinal contra o sarampo vigente em Portugal, no que diz respeito às idades para realização da VASPR I e da VASPR II, no sentido de dar continuidade ao cumprimento do objetivo de eliminar a doença em território nacional. Material e métodos: Foi realizado um estudo com 206 recém-nascidos filhos de mães com diferentes estados vacinais contra o sarampo (0 doses, 1 dose e 2 doses). Também foram estudados 186 adolescentes/jovens que realizaram a VASPR II em diferentes idades. Os dados obtidos provêm de 3 fontes de informação: história vacinal documentada; questionários aplicados por entrevista e informação serológica. A informação serológica foi obtida através do doseamento do título de anticorpos específicos antissarampo (ATS IgG) em soros, recorrendo ao método imunoenzimático ELISA do kit Enzygnost® Anti-measles Virus/IgG, do fabricante Siemens. Resultados: A taxa de cobertura vacinal da vacina contra o sarampo aumentou de valores de pouco mais de 30% na geração nascida antes de 1977, com uma única dose de vacina, para valores superiores a 95 % na geração nascida depois de 1993, com duas doses de vacina. A concentração geométrica de ATS IgG no sangue do cordão umbilical aumentou com o aumento da idade da mãe (r2 = 0,092; p = 0,001). Os recém-nascidos filhos de mães vacinadas, apresentam menor quantidade de ATS IgG do que os filhos de mães não vacinadas (p < 0,0001), independentemente do número de doses que as suas mães tenham recebido (p = 0,222). A concentração geométrica média (CGM) de ATS IgG nos jovens e adolescentes diminui com o tempo decorrido desde a toma de VASPR II (r2 = 0,244; p = 0,001). Não foram encontradas diferenças estatisticamente significativas entre a média de ATS IgG dos indivíduos que se vacinaram com VASPR II aos 5-6 anos de idade e os que se vacinaram entre os 10-13 anos de idade (p = 0,301). Após 9 anos de VASPR II mais de 5 % dos indivíduos já não estão seropositivos contra o sarampo.Discussão: A CGM de ATS IgG aumentou com a idade da mãe, provavelmente porque as mães pertencentes às gerações mais novas contactaram menos com o vírus selvagem do sarampo, devido aos efeitos das elevadas taxas de cobertura vacinal. Os recém-nascidos filhos das mães mais novas, apesar de apresentarem menor CGM de ATS IgG, ao final de 12 meses de idade poderão ainda apresentar um teor de ATS IgG que pode interferir com a resposta vacinal à VASPR I. Vacinar com VASPR II aos 5-6 anos de idade ou vacinar entre os 10-13 anos parece ser indiferente o que parece relevante é o tempo que passa desde a última vacinação VASPR II. Nove anos depois de VASPR II a percentagem de seronegativos já ultrapassa os 5% recomendados pela OMS. Conclusão: As idades da toma de VASPR I e VASPR II poderão ter de ser alteradas por forma a adequarem-se às mudanças epidemiológicas ocorridas nos últimos anos em Portugal e contribuírem para a eliminação do sarampo no país.

Performance analysis of an SRI screen based on employment quality in high and low capital industries: International evidence

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Finance from the NOVA – School of Business and Economics and Maastricht University School of Business and Economics

Lucuma as an exotic high quality fruit imported into Portugal and the UE

This project has two different goals, one of them is to promote the consumption of exotic fruits with high quality. The other goal of the project is to look for the viability of turning this work project into a real business, focusing in two different channels to diversify its revenues: B2B and B2C. In order to achieve this second goal, this project aims to see the best way to commercialize this product (Lucuma powder and Pulp of Lucuma) and how to make it in an efficient way with right companies. Therefore, the project aims to create a company to commercialize the product between the producers in Peru and possibly small businesses interested in acquire the processed fruit and also individuals interested in own consumption in small quantities. This project, if successful, tries to diversify the consumption into other good organic healthy products in the long-term.

Semantic relations extraction from unstructured information for domain ontologies enrichment

Based in internet growth, through semantic web, together with communication speed improvement and fast development of storage device sizes, data and information volume rises considerably every day. Because of this, in the last few years there has been a growing interest in structures for formal representation with suitable characteristics, such as the possibility to organize data and information, as well as the reuse of its contents aimed for the generation of new knowledge. Controlled Vocabulary, specifically Ontologies, present themselves in the lead as one of such structures of representation with high potential. Not only allow for data representation, as well as the reuse of such data for knowledge extraction, coupled with its subsequent storage through not so complex formalisms. However, for the purpose of assuring that ontology knowledge is always up to date, they need maintenance. Ontology Learning is an area which studies the details of update and maintenance of ontologies. It is worth noting that relevant literature already presents first results on automatic maintenance of ontologies, but still in a very early stage. Human-based processes are still the current way to update and maintain an ontology, which turns this into a cumbersome task. The generation of new knowledge aimed for ontology growth can be done based in Data Mining techniques, which is an area that studies techniques for data processing, pattern discovery and knowledge extraction in IT systems. This work aims at proposing a novel semi-automatic method for knowledge extraction from unstructured data sources, using Data Mining techniques, namely through pattern discovery, focused in improving the precision of concept and its semantic relations present in an ontology. In order to verify the applicability of the proposed method, a proof of concept was developed, presenting its results, which were applied in building and construction sector.

Switching mode power amplifier for bluetooth applications

Modern fully integrated transceivers architectures, require circuits with low area, low cost, low power, and high efficiency. A key block in modern transceivers is the power amplifier, which is deeply studied in this thesis. First, we study the implementation of a classical Class-A amplifier, describing the basic operation of an RF power amplifier, and analysing the influence of the real models of the reactive components in its operation. Secondly, the Class-E amplifier is deeply studied. The different types of implementations are reviewed and theoretical equations are derived and compared with simulations. There were selected four modes of operation for the Class-E amplifier, in order to perform the implementation of the output stage, and the subsequent comparison of results. This led to the selection of the mode with the best trade-off between efficiency and harmonics distortion, lower power consumption and higher output power. The optimal choice was a parallel circuit containing an inductor with a finite value. To complete the implementation of the PA in switching mode, a driver was implemented. The final block (output stage together with the driver) got 20 % total efficiency (PAE) transmitting 8 dBm output power to a 50 W load with a total harmonic distortion (THD) of 3 % and a total consumption of 28 mW. All implementations are designed using standard 130 nm CMOS technology. The operating frequency is 2.4 GHz and it was considered an 1.2 V DC power supply. The proposed circuit is intended to be used in a Bluetooth transmitter, however, it has a wider range of applications.