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Optimal Control of a Passive Particle Advected by a Point Vortex 1st

Optimal Control of a Passive Particle Advected by a Point Vo...

1st International Conference on Advanced Research in Technologies, Information, Innovation and Sustainability, ARTIIS 2021

作者： Marques, G. Grilo, T. Gama, S. Pereira, F.L. CMUP - Department of Mathematics FCUP University of Porto Porto Portugal CFisUC - Department of Physics FCTUC University of Coimbra Coimbra Portugal SYSTEC - Department of Electrical and Computer Engineering FEUP University of Porto Porto Portugal

ISBN: (纸本)9783030902407

The objective of this work is to develop a mathematical framework for modeling, control and optimization of the movement of a passive particle advected by a point vortex. Dynamic equations are rewritten in polar coordinates, where the control acts only on the radial coordinate. The optimal control found is explicitly time dependent. This framework should provide a sound basis for the design and control of new advanced engineering systems arising in many important classes of applications, some of which encompass underwater gliders and mechanical fishes. The research effort has been focused in applying necessary conditions of optimality for some class of flow driven dynamic control systems, by using the vortex methods. The control problem of moving a passive particle between two given points driven by this class of flow in a prescribed time and minimizing the energy of the process has been solved by using the maximum principle. © 2021, Springer Nature Switzerland AG.

关键词： Maximum principle

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Efficient Approaches to Adapt Radial Network Protection Systems to Distributed Power Injections 45

Efficient Approaches to Adapt Radial Network Protection Syst...

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45th Annual Conference of the IEEE Industrial Electronics Society, IECON 2019

作者： Santos E Abreu, P.I. Martins, A. Gomes Universidade de Coimbra INESC Coimbra FCTUC Department of Electrical and Computer Engineering Coimbra Portugal

ISBN: (纸本)9781728148786

This paper aims at addressing the loss of coordination of protection systems in radial electricity networks with distributed generators and devising a strategy to ensure desirable quality of service to prevail in such cases. For this purpose, the behaviour of an IEEE test network is studied when distributed power injections are added to the network. The protection scheme used is the widely adopted arrangement of a recloser in the main feeder and fuses in the lateral feeders, which is prone to coordination problems when distributed power injections are added. One of the most economical options to tackle these problems consists of redefining some of the operational parameters of the protective devices, for which purpose power flow and short-circuit analyses have to be carried out. All simulations are performed using the Power Factory software package from DigSILENT. From the simulation results, conclusions are drawn that provide insights into the behaviour of protection systems, highlighting the limitations of the original protections, and devising strategies to provide quality assurance, coordination and selectivity through modifying the parameters of protective devices. © 2019 IEEE.

关键词： Distributed power generation

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Adequate Tialn Thin Films Deposited by Sputtering for Thermistor Sensors: The Study of Conduction Mechanisms and the Microstructure Role on the electrical Properties

SSRN

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SSRN 2022年

作者： Martins, Bruno Patacas, Carlos Cavaleiro, Albano Faia, Pedro Bondarchuk, Oleksandr Fernandes, Filipe IPN - LED&MAT - Instituto Pedro Nunes Laboratório de Ensaios Desgaste e Materiais Rua Pedro Nunes Coimbra3030-199 Portugal University of Coimbra CEMMPRE - Centre for Mechanical Engineering Materials and Processes Department of Mechanical Engineering Rua Luís Reis Santos Coimbra3030-788 Portugal University of Coimbra CEMMPRE – Electrical and Computer Engineering Department FCTUC Polo 2 Pinhal de Marrocos Coimbra3030-290 Portugal ISEP - School of Engineering Polytechnic of Porto Rua Dr. António Bernardino de Almeida 431 Porto4200-072 Portugal Avenida Mestre Jose Veiga Braga4715-330 Portugal

A combinatory deposition was performed by direct current magnetron sputtering (DCMS) to develop Ti1-xAlxN thin films with different Ti/Al ratios. The crystal structure as a function of the x was studied by X-ray diffraction, and sheet resistance response was measured up to 200˚C. From x = 0.16 to x = 0.56, the film shows an fcc phase with Al in solid solution in the TiN matrix, whilst from x ≥ 0.69, a mixture of hcp (AlN) and fcc phases is observed. A negative temperature coefficient (NTC) thermistor behavior was found from x = 0.21 onwards, and a maximum sensitivity β of 1600 K was observed for x = 0.56 and 0.69. One fcc sample (x = 0.46) was selected to analyze the chemical states by X-ray photonelectron spectroscopy and the impedance behavior with the temperature by electrical impedance spectroscopy. The crystal structure, bond states and impedance analysis were compared with an AlN thin film. The conduction mechanism for x = 0.46 is based upon electron hopping, and the resistance of the grain boundary is more relevant at low temperatures. We demonstrate that it is possible to use TiAlN as an NTC-thermistor with different crystal structures and chemical compositions. © 2022, The Authors. All rights reserved.

关键词： Thermistors

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Ultrasonic C-scan techniques for damage evaluation of Carbon Fiber Reinforced Polymers submitted to low energy impacts

Ultrasonic C-scan techniques for damage evaluation of Carbon...

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2019 International Congress on Ultrasonics, ICU 2019

作者： Santos, Mário J. Santos, Jaime B. Reis, Paulo Amaro, Ana FCTUC DEEC Coimbra3030-290 Portugal CEMMPRE Department of Electrical and Computer Engineering University of Coimbra R. Sílvio Lima Coimbra3030-790 Portugal C-MAST Department of Electromechanical Engineering UBI Covilhã Portugal CEMMPRE Department of Mechanical Engineering University of Coimbra R. Luís Reis Santos Coimbra3030-788 Portugal

In this work, different approaches for damage evaluation in composite laminates using ultrasonic C-scan imaging were used: (1) amplitude and (2) time-of-flight (TOF) immersion pulse-echo and (3) air-coupled through-transmission. Five carbon/epoxy laminates with different stacking sequences and thicknesses were impacted. The immersion C-scan images were produced using different frequencies and were compared with the ones obtained by the air-coupled system. The images show that the different methodologies are all able to detect the defects and give reasonable information about their size. The TOF images provide better information about the defects, whenever the delaminations behavior over the sample thickness is of interest, for instance their location and evolution. Better image resolution with sharp defects contour were obtained for high frequencies, as expected. The main advantage of ultrasonic air-coupled system is the absence of water in the inspection procedure, which makes it simpler and less expensive. It is also important when the materials to inspect cannot be wetted for integrity or contamination reasons. As disadvantage, the air C-scan requires transmitted waves of higher power and a great amplification of the received signals in order to face the problem of acoustic losses associated with air. ©2019 Acoustical Society of America.

关键词： Defects

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Assessment of the behavior of protection systems in radial networks with distributed generation 51

Assessment of the behavior of protection systems in radial n...

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51st International Universities Power engineering Conference, UPEC 2016

作者： Santos E Abreu, P.I. Martins, A. Gomes Department of Electrical and Computer Engineering FCTUC Universidade de Coimbra Coimbra Portugal

ISBN: (纸本)9781509046508

This paper evaluates the behavior of electricity distribution networks protection systems, through a systematic short-circuit analysis, as a means of characterizing the behaviour of protective devices in distribution systems. A comparison is made between two of the most common protection schemes, the first one using recloser and fuses and the second using overcurrent relays, with distributed power injections, in one of the IEEE publicly available radial test feeders. All simulations are performed using the Power Factory software package from DigSILENT. From the simulation results, conclusions are drawn that provide insights into the behavior of protection systems, highlighting the limitations of the original protections, and devising strategies to meet quality assurance, coordination and selectivity of proposed modified protection schemes. © 2016 IEEE.

关键词： Overcurrent protection

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Ultrasonic C-scan techniques for damage evaluation of Carbon Fiber Reinforced Polymers submitted to low energy impacts

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Proceedings of Meetings on Acoustics 2019年第1期38卷

作者： Mário J. Santos Jaime B. Santos Paulo Reis Ana Amaro 1FCTUC DEEC Coimbra 3030-290 PORTUGAL marioj@deec.uc.pt 2CEMMPRE Department of Electrical and Computer Engineering University of Coimbra R. Sílvio Lima 3030-790 Coimbra PORTUGAL jaime@deec.uc.pt 3C-MAST Department of Electromechanical Engineering UBI Covilhã PORTUGAL preis@ubi.pt 4CEMMPRE Department of Mechanical Engineering University of Coimbra R. Luís Reis Santos 3030-788 Coimbra PORTUGAL ana.amaro@dem.uc.pt

关键词：

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Generating a pronunciation dictionary for European Portuguese using a joint-sequence model with embedded stress assignment

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Journal of the Brazilian computer Society 2013年第2期19卷 127-134页

作者： Veiga, Arlindo Candeias, Sara Perdigão, Fernando Instituto de Telecomunicações-polo de Coimbra Coimbra Portugal Department of Electrical and Computer Engineering FCTUC Universidade de Coimbra Coimbra Portugal

This paper addresses the problem of grapheme to phoneme conversion to create a pronunciation dictionary from a vocabulary of the most frequent words in European Portuguese. A system based on a mixed approach funded on a stochastic model with embedded rules for stressed vowel assignment is described. The implemented model can generate pronunciations from unrestricted words;however, a dictionary with the 40k most frequent words was constructed and corrected interactively. The dictionary includes homographs with multiplepronunciations. The vocabulary was defined using the CETEMPúblico corpus. The model and dictionary are publicly available. © 2012 The Brazilian computer Society.

关键词： Stochastic models

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Comparison of different modulation strategies applied to PMSM drives under inverter fault conditions 1

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2nd IFIP WG 5.5/SOCOLNET Doctoral Conference on Computing, electrical and Industrial Systems, DoCEIS 2011

作者： Estima, Jorge O. Cardoso, A. J. Marques University of Coimbra FCTUC/IT Department of Electrical and Computer Engineering P - 3030-290 Coimbra Portugal

ISBN: (数字)9783642191701

ISBN: (纸本)9783642191695

This paper presents a comparative study of two distinct modulation strategies applied to a permanent magnet synchronous motor drive, under inverter faulty operating conditions. A rotor field oriented control is used and a performance evaluation is conducted by comparing a hysteresis current control with a space vector modulation technique. Three different operating conditions are considered: normal situation, a single power switch open-circuit fault and a single-phase open-circuit fault. In order to compare the drive performance under these conditions, global results are presented concerning the analysis of some key parameters such as motor efficiency, power factor, electromagnetic torque and currents rms and distortion values. © 2011 IFIP International Federation for Information Processing.

关键词： Timing circuits

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Grid interface for a wind turbine-fuel cell system

Grid interface for a wind turbine-fuel cell system

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International Conference on electrical Machines

作者： Ribeiro, Eunice Cardoso, A. J. Marques Boccaletti, Chiara University of Coimbra FCTUC/IT Department of Electrical and Computer Engineering 3030-290 Coimbra Portugal Sapienza University of Rome Department of Electrical Engineering Via Eudossiana 18 00184 Rome Italy

ISBN: (纸本)9781424441754

Environmental and sustainability concerns are increasing the importance of distributed generation based on renewable energy sources and its grid integration. This paper proposes a grid interface for a hybrid system composed by fuel cells, a wind turbine and supercapacitors. Such grid interface permits to control the wind turbine energy using a diode rectifier and an intermediate DC boost converter and the low voltage of the supercapacitors-fuel cell system is raised by a voltage-fed full-bridge converter. All these power converters are connected to a DC bus and a supervisory control manages the power flow between them, according to the wind turbine production. A voltage source inverter converts the direct current from the DC bus to alternating current, controlling the reactive energy. The inverter output voltage is filtered and raised by a transformer before being delivered to the grid. This grid interface has a low cost and a fast compensation to disturbances. ©2010 IEEE.

关键词： Fuel cells

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Faulty operation analysis of permanent magnet synchronous generator drives for wind turbine applications

Faulty operation analysis of permanent magnet synchronous ge...

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5th IET International Conference on Power Electronics, Machines and Drives, PEMD 2010

作者： Estima, Jorge O. Fernandes, José L.J. Cardoso, A.J. Marques University of Coimbra FCTUC/IT Department of Electrical and Computer Engineering Pólo II - Pinhal de Marrocos P-3030-290 Coimbra Portugal

ISBN: (纸本)9781849192316

This paper presents a performance evaluation of a permanent magnet synchronous generator drive, typically used for wind turbine applications, under distinct faulty operating conditions. A back-to-back topology with full-scale power converters is considered. Several open-circuit fault combinations are introduced on both power converters and their effects are investigated by the calculation and analysis of some parameters such as currents rms and distortion values, power factor, electromagnetic torque and overall drive efficiency.

关键词： Wind turbines

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