Percorrer por autor "Margato, Elmano"
A mostrar 1 - 10 de 24
Resultados por página
Opções de ordenação
- Comparing the power losses of power supplies for fast-field cycling nuclear magnetic resonance equipmentPublication . Lima, Marco; Pereira, Bruno; Sousa, Duarte M.; Roque, António; Margato, ElmanoThe main feature of the Fast-Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) power supplies is to drive a controlled current fulfilling the requirements of this technique. This feature allows fast switching the current of the FFC magnet and performing accurate and repetitive current cycles. When designing this equipment the power losses is not a fundamental parameter of the optimization process but are estimated in order to validate the topology of the final solution giving that the efficiency of the power solution influences the power consumption, and therefore the operational costs, which should be minimized. Under this context, from the power efficiency viewpoint, the power losses of two possible solutions are compared and discussed in this paper. Typical FFC current cycles are used as reference in order to balance the pros and cons of both solutions.
- Comparing two power supplies for fast-field cycling nuclear magnetic resonance relaxometers power losses and performancePublication . Lima, Marco; Pereira, Bruno; Sousa, Duarte M.; Roque, António; Margato, ElmanoThe main power supply of a Fast Field-Cycling Nuclear Magnetic Resonance (FFC-NMR) is the key element comparing the performance of different solutions. The power supply is a current source that supplies a magnet being the current controlled in order to perform adjustable and repetitive current cycles. This power supply can be based on different topologies, operating principles and controlled using distinct techniques. If for the final users of this experimental technique the current cycles of the equipment is the core feature, for the developers also the power losses distribution needs to be analyzed in order to develop efficient solutions. In this paper, the power losses and the dynamic behavior of two solutions for the FFC-NMR power supply are compared and discussed.
- Control of a power supply with cycling current using different controllersPublication . Roque, António; Maia, José; Margato, Elmano; Sousa, Duarte de Mesquita e; Marques, GilFast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometers require controlled current sources in order to get accurate flux density with respect to its magnet. The main elements of the proposed solution are a power semiconductor, a DC voltage source and the magnet. The power semiconductor is commanded in order to get a linear control of the flux density. To implement the flux density control, a Hall Effect sensor is used. Furthermore, the dynamic behavior of the current source is analyzed and compared when using a PI controller and a PD2I controller.
- Control of a power supply with cycling current using different controllersPublication . Roque, António; Maia, José; Margato, Elmano; Sousa, Duarte de Mesquita e; Marques, GilFast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometers require controlled current sources in order to get accurate flux density with respect to its magnet. The main elements of the proposed solution are a power semiconductor, a DC voltage source and the magnet. The power semiconductor is commanded in order to get a linear control of the flux density. To implement the flux density control, a Hall Effect sensor is used. Furthermore, the dynamic behavior of the current source is analyzed and compared when using a PI controller and a PD2I controller.
- Design of current power sources for a FFC NMR apparatus: a comparisonPublication . Roque, António; Pinto, Sónia F.; Santana, João; Sousa, Duarte; Margato, Elmano; Maia, JoséThe power supply of a Fast Field Cycling Nuclear Magnetic Resonance apparatus is typically a current power source, with characteristics that are not fulfilled by most of the commercially available power supplies. This current source is used to supply a specially designed magnet, and should be able to drive a cycling current with a slew rate lower than 3 A/ms. In this paper, two solutions for this current source are designed and discussed. The first uses two power supplies: the main voltage source and an auxiliary power supply to guarantee the current transitons from the low level to the high level. In the second solution the auxiliary power supply is replaced by a capacitor. To guarantee the required current slews rates, the possibility of using resistors to dissipate the energy store in the magnet is also discussed.
- Discurso do presidente do Instituto Politécnico de Lisboa na sessão de aberturaPublication . Margato, ElmanoA Escola Superior de Educação de Lisboa comemora hoje os 100 anos do início da construção do seu edifício sede. Este belo edifício, do qual ainda hoje desfrutamos, da autoria do Arquiteto Arnaldo Adães Bermudes, foi mandado construir pelo Governo da Primeira República para o funcionamento da Escola Normal Primária de Lisboa, posteriormente, Escola do Magistério Primário de Lisboa e, atualmente, Escola Superior de Educação de Lisboa. Coube ao então Presidente da República, Bernardino Machado, a sua inauguração e cabe-nos hoje a nós e à Sr.ª Prof.ª Isabel Alçada, em representação do atual Presidente da República, Prof. Marcelo Rebelo de Sousa, o assinalar, com enorme regozijo, do trabalho que tem vindo a ser desenvolvido por esta Escola em prol de uma melhor educação para todos.
- Discursos do Presidente: presidência 2016-2025Publication . Margato, ElmanoEsta publicação contém os discursos proferidos pelo Presidente do Instituto Politécnico de Lisboa (IPL), Polytechnic University of Lisbon (PUL), ao longo dos seus dois mandatos, de 14 de março de 2016 a 09 de fevereiro de 2025. Este legado permite conhecer o pensamento estratégico do Presidente, na liderança da equipa cujo trabalho conduziu ao incremento do desenvolvimento científico, pedagógico, artístico, cultural e de extensão de uma instituição, localizada na área metropolitana de Lisboa, que possui nove unidades orgânicas (6 escolas e 2 institutos e 1 serviço de ação social). Em 2024, o Politécnico de Lisboa reunia cerca de 14000 estudantes, 1200 docentes, 400 funcionários e tem‑se vindo a pautar por uma taxa de colocação de estudantes na primeira fase do Concurso Nacional de Acesso ao Ensino Superior acima de 95%. A internacionalização da instituição, ao nível dos estudantes e, também, da investigação, foram preocupações sempre presentes. Destaca‑se pela sua relevância a colaboração com a Universidade de Macau e a integração da Universidade Europeia U!REKA de que fazem parte mais cinco universidades de ciências aplicadas da europa. Para apoio à concretização deste objetivo foi criado o Centro de Línguas e Cultura do IPL (CLiC‑IPL), de que desfrutam estudantes, docentes e funcionários não docentes.
- Fast optimum-predictive control and capacitor voltage balancing strategy for bipolar back-to-back NPC converters in high-voltage direct current transmission systemsPublication . Chaves, Miguel; Margato, Elmano; Silva, J. F.; Pinto, S. F.; Santana, J.Multilevel power converters have been introduced as the solution for high-power high-voltage switching applications where they have well-known advantages. Recently, full back-to-back connected multilevel neutral point diode clamped converters (NPC converter) have been used inhigh-voltage direct current (HVDC) transmission systems. Bipolar-connected back-to-back NPC converters have advantages in long-distance HVDCtransmission systems over the full back-to-back connection, but greater difficulty to balance the dc capacitor voltage divider on both sending and receiving end NPC converters. This study shows that power flow control and dc capacitor voltage balancing are feasible using fast optimum-predictive-based controllers in HVDC systems using bipolar back-to-back-connected five-level NPC multilevel converters. For both converter sides, the control strategytakes in account active and reactive power, which establishes ac grid currents in both ends, and guarantees the balancing of dc bus capacitor voltages inboth NPC converters. Additionally, the semiconductor switching frequency is minimised to reduce switching losses. The performance and robustness of the new fast predictive control strategy, and its capability to solve the DC capacitor voltage balancing problem of bipolar-connected back-to-back NPCconverters are evaluated.
- Fast-Field Cycling Nuclear Magnetic Resonance relaxometer's electromagnet with optimized homogeneity and reduced volumePublication . Videira, P.; Sebastião, P.; Roque, A.; Sousa, D. M.; Margato, ElmanoIn this article a Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) electromagnet with low power consumption (less than 200 W), high field homogeneity and reduced volume is projected and described. The electromagnet is iron and copper based, possessing a high permeability and allowing for good magnetic field homogeneity in the operating range of 0 to 0.33 T. With this solution, it is possible to increase 65% the maximum magnetic field keeping the magnetic field homogeneity in comparison with former similar FFC relaxometers. Electromagnet's experimental and simulation results evaluating the generated magnetic field, field homogeneity, heating effects and cooling requirements are also presented. In addition, some technical aspects of the required coupled systems such as the cooling, sample heating are assessed.
- FFC NMR relaxometer with magnetic flux density controlPublication . Roque, Antonio; Duarte M. Sousa, Duarte; Sebastiao, Pedro; Margato, Elmano; Marques, GilThis paper describes an innovative solution for the power supply of a fast field cycling (FFC) nuclear magnetic resonance (NMR) spectrometer considering its low power consumption, portability and low cost. In FFC cores, the magnetic flux density must be controlled in order to perform magnetic flux density cycles with short transients, while maintaining the magnetic flux density levels with high accuracy and homogeneity. Typical solutions in the FFC NMR literature use current control to get the required magnetic flux density cycles, which correspond to an indirect magnetic flux density control. The main feature of this new relaxometer is the direct control of the magnetic flux density instead of the magnet current, in contrast with other equipment available in the market. This feature is a great progress because it improves the performance. With this solution it is possible to compensate magnetic field disturbances and parasitic magnetic fields guaranteeing, among other possibilities, a field control below the earth magnetic field. Experimental results validating the developed solution and illustrating the real operation of this type of equipment are shown.
- «
- 1 (current)
- 2
- 3
- »