830 research outputs found
Global Action-Angle Variables for Non-Commutative Integrable Systems
In this paper we analyze the obstructions to the existence of global
action-angle variables for regular non-commutative integrable systems (NCI
systems) on Poisson manifolds. In contrast with local action-angle variables,
which exist as soon as the fibers of the momentum map of such an integrable
system are compact, global action-angle variables rarely exist. This fact was
first observed and analyzed by Duistermaat in the case of Liouville integrable
systems on symplectic manifolds and later by Dazord-Delzant in the case of
non-commutative integrable systems on symplectic manifolds. In our more general
case where phase space is an arbitrary Poisson manifold, there are more
obstructions, as we will show both abstractly and on concrete examples. Our
approach makes use of a few new features which we introduce: the action bundle
and the action lattice bundle of the NCI system (these bundles are canonically
defined) and three foliations (the action, angle and transverse foliation),
whose existence is also subject to obstructions, often of a cohomological
nature
TORGA.net: the trans Portugal-Galicia communication network
The Trans Portugal Galicia Network
Project, TORGA.net, was a proposal
to the Program Interregional IIIA,
Galicia – North of Portugal sub-program with the following partners: University of Minho, University of Vigo, Centro de Supercomputación de Galicia and the Centro de Computação Gráfica in Guimarães. It has as its main objective the creation of infrastructures and the organization and development of the space beyond borders.
The project proposes to establish a broadband communication network with reduced operational costs that links the campuses of the Universities
of Vigo and Minho, as well as their associated Technological Centers, which are the Supercomputación de Galicia and the Centro de Computação Gráfica in Guimarães.
Using this telecommunications infrastructure, Access Centers will be installed in a Technology Access Grid, which will allow distance work sessions such as seminars, lessons, or
discussion meetings.Momentan arbeiten die Bildungs-, Forschungs- und Entwicklungs- Einrichtungen von Galicien und dem Norden von Portugal nur gelegentlich und auf einzelne Projekte beschränkt zusammen, obwohl sich längst herausgestellt hat, welche Synergien aus dieser Kooperation entstehen. Auf Grund dessen sieht das Torga.net Projekt die Implementierung einer Breitband- Kommunikations-Infrastruktur vor. Diese wird die Problematik, die durch die geringe Zusammenarbeit beider Regionen entsteht, reduzieren und den Zugang und das Teilen von Wissen erleichtern. Aufbauend auf dieser Kommunikationsplattform sind Lösungen der kooperativen Arbeit vorgesehen. Videokonferenzen und E-Learning dienen dabei als Unterstützung für dieb Zusammenarbeit zwischen den Institutionen beiderseits der Grenzen.União Europeia (UE) - Interregional IIIA, Galicia – North of Portugal Program - Direcção-Geral do Desenvolvimento Regional
Secretaria de Estado de Presupuestos y Gastos
Broker colaborativo na cloud para gestão de fontes distribuídas de energia
Neste trabalho é apresentado um sistema de informação (SI) que pretende ajudar à colaboração de VE de modo a entrarem no mercado de energia elétrica, conseguindo que o dono do VE seja compensado, minimizando o investimento inicial na compra do VE e ajude a criar um modelo de armazenamento de energia mais amigo do ambiente. A este SI chamou-se de Broker Colaborativo ou simplesmente Broker deverá permitir ao dono do VE criar um perfil com a sua informação pessoal, com a informação do VE que possui e informação relativa à colaboração que pretende efetuar, ou seja, horários, locais e percentagem da bateria que pretende usar na colaboração. Sendo necessário agrupar e filtrar um número significativo de VE, para entrada no mercado de energia, existe por parte do Broker a implementação dessas responsabilidades. Sendo que a otimização do consumo de energia é um fator importante neste trabalho, a implementação do Broker foi efetuado sobre o paradigma de Cloud Computing onde os recursos energéticos são partilhados e possuiu uma grande capacidade de escalamento onde se poderá criar os recursos à medida da necessidade.In this work it is proposed the design of a system to handle Distributed Energy Resources (DER), which is a new reality due to Electric Vehicles (EVs), Microgeneration (MG) and the open Electrical Markets (EM). This upcoming reality brings the need of the ‘old’ central energy control to be installed locally. For that we propose a local energy broker, responsible to handle local energy flow and to exchange energy with ‘big’ market players, and based on a collaborative approach, to promote user’s participation to increase systems knowledge. The energy broker uses cloud computing paradigm to create a collaborative communication between the involved parts.Fundação para a Ciência e a Tecnologia (FCT
Predictive control of a current-source inverter for solar photovoltaic grid interface
Solar photovoltaic systems are an increasing option for electricity production, since they produce electrical energy from a clean renewable energy resource, and over the years, as a result of the research, their efficiency has been increasing. For the interface between the dc photovoltaic solar array and the ac electrical grid is necessary the use of an inverter (dc-ac converter), which should be optimized to extract the maximum power from the photovoltaic solar array. In this paper is presented a solution based on a current-source inverter (CSI) using continuous control set model predictive control (CCS-MPC). All the power circuits and respective control systems are described in detail along the paper and were tested and validated performing computer simulations. The paper shows the simulation results and are drawn several conclusions.FCT - Fundação para a Ciência e Tecnologia within scope of the project: PEst- UID/CEC/00319/201
Development of a digital controller with data acquisition to a test bench for eletric motors
The electric motors’ test benches are greatly used by electric motors manufacturers and drive system designers. In this paper it is described the conversion process of an older manually controlled test bench, in an automatic digitally controlled one with integrated data acquisition system. The renewed test bench is based in a two quadrant eddy current electromagnetic brake, in which the manual torque controller and analog indicator have been replaced by an automatic digital controller, by which is possible to predefine a torque profile for the test. With the data acquisition system it is possible the acquisition and recording of speed, torque and internal temperature on the brake. Special focus is given to the power converter used to control the current in the electromagnetic brake and to the torque data acquisition system, namely, the calibration of the load cell.FEDER Funds - Operational Programme for Competitiveness Factors (COMPETE)Fundação para a Ciência e a Tecnologia (FCT) - PTDC/EEA-EEL/104569/2008, MIT-PT/EDAM-SMS/0030/2008
Discrimination of idiopathic Parkinson's disease and vascular parkinsonism based on gait time series and the levodopa effect
Idiopathic Parkinson's disease (IPD) and vascular parkinsonism (VaP) present highly overlapping phenotypes, making it challenging to distinguish between these two parkinsonian syndromes. Recent evidence suggests that gait assessment and response to levodopa medication may assist in the objective evaluation of clinical differences. In this paper, we propose a new approach for gait pattern differentiation that uses convolutional neural networks (CNNs) based on gait time series with and without the influence of levodopa medication. Wearable sensors positioned on both feet were used to acquire gait data from 14 VaP patients, 15 IPD patients, and 34 healthy subjects. An individual's gait features are affected by physical characteristics, including age, height, weight, sex, and walking speed or stride length. Therefore, to reduce bias due to intersubject variations, a multiple regression normalization approach was used to obtain gait data. Recursive feature elimination using the linear support vector machine, lasso, and random forest were applied to infer the optimal feature subset that led to the best results. CNNs were implemented by means of various hyperparameters and feature subsets. The best CNN classifiers achieved accuracies of 79.33%±6.46, 82.33%±10.62, and 86.00%±7.12 without (off state), with (on state), and with the simultaneous consideration of the effect of levodopa medication (off/on state), respectively. The response to levodopa medication improved classification performance. Based on gait time series and response to medication, the proposed approach differentiates between IPD and VaP gait patterns and reveals a high accuracy rate, which might prove useful when distinguishing other diseases related to movement disorders.This research was partially financed by NORTE2020 and FEDER within the project NORTE-01–0145-FEDER- 000026 (DeM-Deus Ex Machina) and by Portuguese Funds through FCT (Fundação para a Ciência e a Tecnologia) within the Projects UIDB/00013/2020, UIDP/00013/2020 and UIDB/00319/2020
A novel two-switch three-level active rectifier for grid-connected electrical appliances in smart grids
A novel topology of two-switch three-level active
rectifier (TSTL-AR) is proposed in order to connect electrical
appliances to smart grids considering power quality aspects. The
proposed active rectifier is presented as a powerful solution to
mitigate the negative effects of current harmonic distortion of the
diode-bridge rectifiers, besides the ability of operating with
unitary power factor. These aspects are particularly relevant
considering the new paradigm of smart grids, where almost all
the electrical appliances should be controlled in order to comply
normative impositions of power quality. In addition, active
rectifiers are also fundamental devices regarding the electric
vehicle battery chargers, which are a new and significant class of
electrical appliances for smart grids. In this paper, a
comprehensive and detailed description of the novel topology of
TSTL-AR is presented and compared with the classical power
factor correction topology. Along the paper, it is discussed in
detailed a digital current control structure based on finite control
set model predictive control, permitting an accurate, robust, and
faster control of the grid current. A laboratory prototype was
developed and experimental tests were performed, verifying the
precise operation, and demonstrating the importance of the
proposed active rectifier for electrical appliances in smart grids.
The results show a low level of current THD, a unitary power
factor, and a regulated dc-link voltage.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT - Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF - European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 - POCI − 01–0145-FEDER-016434.info:eu-repo/semantics/publishedVersio
Residual granitic soil improvement for rammed earth construction
This paper describes the research developed to evaluate the performance of stabilised residual granitic soil from the north region of Portugal. It is part of a research project designed to investigate the possibility of using this soil for rammed earth construction. Since its reduced plasticity makes the use of lime less effective, and the increasing environmental concerns with cement production can no longer be ignored, the study was focused on binders made from alkaline activation of low calcium fly ash. Therefore, the aim of this work was to determine, through a parametric analysis using laboratory tests, the optimum fly ash – based alkaline activated binder for improving granitic soil, in terms of mechanical strength. Identification of the key parameters allowed the characterisation of the most effective mixtures, which will be later used in the construction of large rammed earth wall panels that will be tested according to proper specifications
Directed play and spontaneous play in preshool education
A presente investigação analisa a influência de dois programas de intervenção psicomotora no desenvolvimento sócio-emocional e do autoconceito infantil: 1) Jogo espontâneo (GE), onde o adulto participa ativamente nos diferentes jogos criados espontaneamente pela criança, e 2) Jogo dirigido (GD), que consiste em diferentes jogos planeados e organizados pelo adulto para as crianças, tendo este apenas a função de ensinar o jogo e de dar feedback sobre a performance da criança. Participaram 46 crianças (4.1±0.8 anos de idade), 46 encarregados de educação (34.9±5.5 anos de idade) e 3 educadoras (54±2.9 anos de idade) de crianças organizadas em 3 grupos experimentais: GE, GD e grupo controlo (GC), que não sofreu intervenção. Os participantes foram avaliados previamente e após a fase de intervenção (24 sessões) através dos seguintes instrumentos de avaliação: 1) Escala de Percepção do Autoconceito Infantil; 2) Preschool and Kindergarten behavior scale- second edition. Ao primeiro responderam as crianças e ao segundo os encarregados de educação e as educadoras. Foram encontradas diferenças estatisticamente significativas no GE, entre o pré e o pós-teste. Estas diferenças foram observadas ao nível da diminuição dos problemas de comportamento sinalizados pelas educadoras, e no aumento do autoconceito das criançasinfo:eu-repo/semantics/publishedVersio
Environmental Performance of a Solid Waste Monetization Process Applied to a Coal-Fired Power Plant with Semi-Dry Flue Gas Desulfurization
Mixing of semi-dry flue gas desulfurization solids and fly-ash from coal-fired power plants results in a solid waste contaminated by calcium sulfite. Therefore, it becomes useless for industry and is often landfilled. To support decision-making on process configurations to monetize this solid residue a gate-to-gate life cycle assessment was performed, considering three scenarios: BASE case – standard 360 MW power plant,
CASE I – base plant adopting dry thermal oxidation treatment of spray dryer solids, CASE II ‒ bypass of desulfurization system. Cases I and II allow commercialization of the solid residue as class C fly-ash. Evaluated alternatives were compared based on quantitative potential environmental impacts, using United States Environmental Protection Agency waste reduction algorithm. Based on the results, the BASE case was more aggressive to the environment, due to solid waste production. CASE II increased photochemical oxidation and acidification potentials. CASE I was the more environmentally friendly but demands additional capital and operational expenditure
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