Adaptive and predictive controllers applied to onshore wind energy conversion system

This paper presents a simulation of onshore energy conversion system connected to the electric grid and under an event-based supervisor control based on deterministic version of a finite state machine. The onshore energy conversion system is composed by a variable speed wind turbine, a mechanical transmission system described by a two-mass drive train, a gearbox, a doubly fed induction generator rotor and by a two-level converter. First, mathematical models of a variable speed wind turbine with pitch control are studied, followed by the study of different controller types such as adaptive controllers and predictive controllers. The study of an event-based supervisor based on finite state machines is also studied. The control and supervision strategy proposed for the onshore energy conversion system is based on a hierarchical structure with two levels, execution level where the adaptive and predictive controllers are included, and the supervision level where the event-based supervisor is included. The objective is to control the electric output power around the reference power and also to analyze the operational states according to the wind speed. The studied mathematical models are integrated into computer simulations for the onshore energy conversion system and the obtained numerical results allow for the performance assessment of the system connected to the electric grid. A comparison of the onshore energy conversion system performance without or with the supervisor is carried out to access the influence of the control and supervision strategy on the performance

Fuzzy, integer and fractional order control: application on a wind turbine benchmark model

This paper presents a comparison between proportional integral control approaches for variable speed wind turbines. Integer and fractional-order controllers are designed using linearized wind turbine model whilst fuzzy controller also takes into account system nonlinearities. These controllers operate in the full load region and the main objective is to extract maximum power from the wind turbine while ensuring the performance and reliability required to be integrated into an electric grid. The main contribution focuses on the use of fractional-order proportional integral (FOPI) controller which benefits from the introduction of one more tuning parameter, the integral fractional-order, taking advantage over integer order proportional integral (PI) controller. A comparison between proposed control approaches for the variable speed wind turbines is presented using a wind turbine benchmark model in the Matlab/Simulink environment. Results show that FOPI has improved system performance when compared with classical PI and fuzzy PI controller outperforms the integer and fractional-order control due to its capability to deal with system non linearities and uncertainties

Distributed MPC for Thermal Comfort and Load Allocation with Energy Auction

This paper presents a distributed predictive control methodology for indoor thermal comfort that optimizes the consumption of a limited shared energy resource using an integrated demand-side management approach that involves a power price auction and an appliance loads allocation scheme. The control objective for each subsystem (house or building) aims to minimize the energy cost while maintaining the indoor temperature inside comfort limits. In a distributed coordinated multi-agent ecosystem, each house or building control agent achieves its objectives while sharing, among them, the available energy through the introduction of particular coupling constraints in their underlying optimization problem. Coordination is maintained by a daily green energy auction bring in a demand-side management approach. Also the implemented distributed MPC algorithm is described and validated with simulation studies

Eczema das Mãos: Qualidade de Vida e Gravidade da Doença numa População Portuguesa

Introduction: Hand eczema is a very common disease with a significant social and occupational impact.Objectives: To characterize a Portuguese outpatient population with hand eczema; to evaluate the impairment of the disease in quality of life (QoL); to relate the disease severity with QoL.Methods: The authors designed a prospective study. Information about atopy, psoriasis, occupational exposure and duration of disease, was recorded. The QoL was assessed by the DLQI questionnaire (Dermatology Life Quality Index) and the severity was assessed using the hand eczema severity index (HECSI). All participants were patch tested.Results: Eighty-five patients were included with a female predominance (78.8%). The median DLQI was 9.0. We found statistically significant differences in the variable HECSI between genders with greater impact in males. A significant positive correlation was found between HECSI and DLQI. DLQI and HECSI were independent of atopy, psoriasis or etiology. Increasing age significantly affects DLQI but not HECSI.Conclusions: Hand eczema has a significant impact in QoL. Although the disease is more prevalent among women it was found to be of greater severity among men. The QoL seems to be influenced by disease severity and increasing age but it was independent of the other studied variables.Introdução: O eczema das mãos é uma doença muito comum e com importante impacto social e ocupacional.Objetivos: Caracterizar a população seguida no Hospital de Braga por eczema das mãos no período de um ano; avaliar o impacto da doença na qualidade de vida; correlacionar a gravidade da doença com a qualidade de vida.Métodos: Os autores desenharam um estudo prospetivo. Todos os doentes preencheram um questionário para avaliar a qualidade de vida (Dermatology Life Quality Index - DLQI) e foram avaliados para determinar a gravidade da doença usando o HECSI (Hand Eczema Severity Index). Todos os pacientes foram submetidos a testes epicutâneos. Foi definida a etiologia e duração da doença, assim como existência de antecedentes de atopia e/ou psoríase.Resultados: Foram incluídos 85 doentes, a maioria mulheres (78,8%). A mediana do DLQI foi 9,0. Encontraram-se diferenças estatisticamente significativas na variável HECSI entre géneros com maior impacto no sexo masculino. Observou-se correlação positiva significativa entre HECSI e DLQI. As variáveis DLQI e HECSI revelaram- se independentes das variáveis atopia, psoríase ou etiologia. O aumento da idade afetou significativamente o DLQI, mas não o HECSI.Conclusões: O eczema das mãos tem impacto significativo na qualidade de vida. Embora a doença seja mais prevalente no sexo feminino, verificou-se maior gravidade da doença entre os homens. A qualidade de vida parece ser influenciada pela severidade da doença e aumento da idade, mas foi independente das outras variáveis estudadas

Transduction mechanisms, micro-structuring techniques, and applications of electronic skin pressure sensors: A review of recent advances

PD/BD/105876/2014Electronic skin (e-skin), which is an electronic surrogate of human skin, aims to recreate the multifunctionality of skin by using sensing units to detect multiple stimuli, while keeping key features of skin such as low thickness, stretchability, flexibility, and conformability. One of the most important stimuli to be detected is pressure due to its relevance in a plethora of applications, from health monitoring to functional prosthesis, robotics, and human-machine-interfaces (HMI). The performance of these e-skin pressure sensors is tailored, typically through micro-structuring techniques (such as photolithography, unconventional molds, incorporation of naturally micro-structured materials, laser engraving, amongst others) to achieve high sensitivities (commonly above 1 kPa−1), which is mostly relevant for health monitoring applications, or to extend the linearity of the behavior over a larger pressure range (from few Pa to 100 kPa), an important feature for functional prosthesis. Hence, this review intends to give a generalized view over the most relevant highlights in the development and micro-structuring of e-skin pressure sensors, while contributing to update the field with the most recent research. A special emphasis is devoted to the most employed pressure transduction mechanisms, namely capacitance, piezoelectricity, piezoresistivity, and triboelectricity, as well as to materials and novel techniques more recently explored to innovate the field and bring it a step closer to general adoption by society.publishersversionpublishe

Numerical simulation of the filling and curing stages in reaction injection moulding, using CFX

Mestrado em Engenharia MecânicaOs métodos habitualmente utilizados para a simulação de injecção em moldes envolvem um número considerável de simplificações, originando reduções significativas do esforço computacional mas, nalguns casos também limitações. Neste trabalho são efectuadas simulações de Reaction Injection Moulding (RIM) com o mínimo de simplificações, através da utilização do software de CFD multi-objectivos CFX, concebido para a simulação numérica de escoamentos e transferência de calor e massa. Verifica-se que o modelo homogéneo para escoamentos multifásicos do CFX, geralmente considerado o apropriado para a modelação de escoamentos de superfície livre em que as fases estão completamente estratificadas, é incapaz de modelar correctamente o processo de enchimento. Este problema é ultrapassado através da implementação do modelo não homogéneo juntamente com a condição de fronteira de escorregamento livre para o ar. A reacção de cura é implementada no código como uma equação de transporte para uma variável escalar adicional, com um termo fonte. São testados vários esquemas transitórios e advectivos, com vista ao reconhecimentos de quais os que produzem os resultados mais precisos. Finalmente, as equações de conservação de massa, quantidade de movimento, cura e energia são implementadas conjuntamente para simular os processos simultâneos de enchimento e cura presentes no processo RIM. Os resultados numéricos obtidos reproduzem com boa fidelidade outros resultados numéricos e experimentais disponíveis, sendo necessários no entanto tempos de computação consideravelmente longos para efectuar as simulações. ABSTRACT: Commonly used methods for injection moulding simulation involve considerable number of simplifications, leading to a significant reduction of the computational effort but, in some cases also to limitations. In this work, Reaction Injection Moulding (RIM) simulations are performed with minimum of simplifications, by using the general purpose CFD software package CFX, designed for numerical simulation of fluid flow and heat and mass transfer. The CFX’s homogeneous multiphase flow model, which is generally considered to be the appropriate choice for modelling free surface flows where the phases are completely stratified and the interface is well defined, is shown to be unable to model the filling process correctly. This problem is overcome through the implementation of the inhomogeneous model in combination with the free-slip boundary condition for the air phase. The cure reaction is implemented in the code as a transport equation for an additional scalar variable, with a source term. Various transient and advection schemes are tested to determine which ones produce the most accurate results. Finally, the mass conservation, momentum, cure and energy equations are implemented all together to simulate the simultaneous filling and curing processes present in the RIM process. The obtained numerical results show a good global accuracy when compared with other available numerical and experimental results, though considerably long computation times are required to perform the simulations

Optimization of zno nanorods concentration in a micro-structured polymeric composite for nanogenerators

The growing use of wearable devices has been stimulating research efforts in the de-velopment of energy harvesters as more portable and practical energy sources alternatives. The field of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), especially employing zinc oxide (ZnO) nanowires (NWs), has greatly flourished in recent years. Despite its modest piezoelectric coefficient, ZnO is very attractive due to its sustainable raw materials and the facility to obtain distinct morphologies, which increases its multifunctionality. The integration of ZnO nanostructures into polymeric matrices to overcome their fragility has already been proven to be fruitful, nevertheless, their concentration in the composite should be optimized to maximize the harvesters’ output, an aspect that has not been properly addressed. This work studies a composite with variable concentrations of ZnO nanorods (NRs), grown by microwave radiation assisted hydrothermal synthesis, and polydimethylsiloxane (PDMS). With a 25 wt % ZnO NRs concentration in a composite that was further micro-structured through laser engraving for output enhancement, a nanogenerator (NG) was fabricated with an output of 6 V at a pushing force of 2.3 N. The energy generated by the NG could be stored and later employed to power small electronic devices, ultimately illustrating its potential as an energy harvesting device.publishersversionpublishe

"Foliáceos ovóides" e "grandes pontas bifaciais" nos povoados de São Pedro (Redondo)

O sítio de S. Pedro (Redondo, Alentejo), ocupado entre os finais do 4º e inícios do 3º milénio a.n.e, caracteriza-se por uma abundante componente artefactual em pedra lascada, sobretudo em xistos siliciosos e quartzitos. A partir de uma primeira abordagem tecno-tipológica a este conjunto lítico, é destacável a presença de utensílios foliáceos de talhe bifacial, prestando-se aqui um especial enfoque aos chamados “foliáceos ovóides” e “grandes pontas bifaciais” pela sua raridade no contexto neo-calcolítico da região alentejana.The archaeological site of S. Pedro (Redondo, Alentejo), occupied between the final of the 4th and the beginning of the 3rd Millenium b.C., is characterized by a huge quantity of lithic industry remains, namely on siliceous slates and quartzites. Through a first technological and typological approach to this set, a significant presence of bifacial retouch tools was detected. In this text, we will focus on the “ovoid bifaces” and “large bifacial points”, due to their scarcity in the Neo-Chalcolithic of Alentejo region.info:eu-repo/semantics/publishedVersio

Parylene C as a Multipurpose Material for Electronics and Microfluidics

Funding Information: This work was financed by national funds from FCT—Fundação para a Ciência e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020, UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication—i3N. Furthermore, the work received funding from FCT in the scope of projects UIDP/04378/2020 and UIDB/04378/2020 of the Research Unit on Applied Molecular Biosciences—UCIBIO and the project LA/P/0140/2020 of the Associate Laboratory Institute for Health and Bioeconomy—i4HB. This work also received funding from the European Community’s H2020 program under grant agreements 716510 (ERC-2016-StG TREND), 787410 (ERC-2019-AdG DIGISMART) and 952169 (SYNERGY, H2020-WIDESPREAD-2020-5, CSA), 101008701 (EMERGE, H2020-INFRAIA-2018-2020). B. J. Coelho acknowledges FCT for the attribution of grant SFRH/BD/132904/2017 and grant COVID/BD/152453/2022. Publisher Copyright: © 2023 by the authors.Poly(p-xylylene) derivatives, widely known as Parylenes, have been considerably adopted by the scientific community for several applications, ranging from simple passive coatings to active device components. Here, we explore the thermal, structural, and electrical properties of Parylene C, and further present a variety of electronic devices featuring this polymer: transistors, capacitors, and digital microfluidic (DMF) devices. We evaluate transistors produced with Parylene C as a dielectric, substrate, and encapsulation layer, either semitransparent or fully transparent. Such transistors exhibit steep transfer curves and subthreshold slopes of 0.26 V/dec, negligible gate leak currents, and fair mobilities. Furthermore, we characterize MIM (metal–insulator–metal) structures with Parylene C as a dielectric and demonstrate the functionality of the polymer deposited in single and double layers under temperature and AC signal stimuli, mimicking the DMF stimuli. Applying temperature generally leads to a decrease in the capacitance of the dielectric layer, whereas applying an AC signal leads to an increase in said capacitance for double-layered Parylene C only. By applying the two stimuli, the capacitance seems to suffer from a balanced influence of both the separated stimuli. Lastly, we demonstrate that DMF devices with double-layered Parylene C allow for faster droplet motion and enable long nucleic acid amplification reactions.publishersversionpublishe