Participação no grupo cooperativo do movimento da escola moderna: contributos para o desenvolvimento profissional docente

Dissertação apresentada à Escola Superior de Educação de Lisboa para obtenção do grau de Mestre em Ciências da Educação, especialidade Supervisão em EducaçãoO trabalho cooperativo entre os professores tem merecido destaque nos últimos anos, relacionando-se com ajuda mútua (Carneiro, Geller & Nitzke, 2008), onde todos trabalham com o intuito de alcançar objetivos pré definidos entre si (Dillenbourg, 1999) e de obter competências profissionais. Muito embora as práticas de trabalho individual ainda sejam uma tentação para os professores na atualidade há uma maior tendência para trabalharem colaborativamente nas escolas ou em grupos de formação organizados pelas associações de professores. Neste contexto, o estudo que apresentamos tem como finalidade compreender os processos de autoformação cooperada no contexto dos grupos cooperativos do Movimento da Escola Moderna (MEM) e o seu impacto no desenvolvimento profissional docente. Tendo em conta o objeto de estudo, identificaram-se as seguintes questões: i) Que motivações levam os professores a integrar os grupos cooperativos do MEM? ii) Como se organiza e desenvolve a autoformação cooperada nos grupos cooperativos do MEM? iii) Quais os aspetos positivos e constrangimentos identificados pelos professores no trabalho desenvolvido nos grupos cooperativos? iv) Quais as razões que levam os professores a permanecer e a abandonar a sua participação nos grupos cooperativos do MEM? v) Qual o impacto das experiências realizadas no contexto dos grupos cooperativos no desenvolvimento profissional docente? Para o efeito, contámos com a participação de seis professores pertencentes a um grupo cooperativo do MEM. Tendo como referência o objeto de estudo recorremos a uma metodologia de natureza qualitativa e privilegiámos como técnica de recolha de dados a entrevista semiestruturada. Para o tratamento dos dados sustentámo-nos na análise de conteúdo seguindo os passos recomendados para a análise de conteúdo por Bardin (2009). Os resultados do estudo permitiram constatar que o trabalho realizado no seio do grupo cooperativo promove o desenvolvimento profissional docente dado que fomenta a competência reflexiva sobre a prática pedagógica, bem como o desenvolvimento de outras competências da praxis, nomeadamente, a identificação de estratégias mais adequadas à resolução de problemas emergentes do quotidiano profissional do professor.Abstract The cooperative work between teachers has been receiving more attention over the last years, in relation with the mutual assistance (Carneiro, Geller & Nitzke, 2008), where everybody works with an aim to achieve predefined goals, which were created in relation to one another (Dillenbourg, 1999) and to obtain professional skills. Although individual work practices are still tempting to teachers, there is currently a greater trend to work as a group in schools or in training groups organized by teachers’ associations. In this context, this study aims to understand the cooperative self-training processes within the context of MEM’s cooperative groups and their impact in the professional teacher development. Considering the subject of study, the following questions were identified: i) What motivations lead the teachers to integrate MEM’s cooperative groups? ii) How is the cooperative self-training organized and how is it developed within in MEM’s cooperative groups? iii) What are the positive aspects and constraints identified by the teachers within the work developed in the cooperative groups? iv) What are the reasons that lead the teachers to stay or abandon its participation in MEM’s cooperative groups? v) What is the impact of experiences carried in the context of cooperative groups in the professional teacher development? For this purpose, we had the participation of six teachers belonging to one of MEM’s cooperative groups. Keeping the subject of study as a reference, we use a qualitative methodology and gave preference to the semi structured interview as the data collection technique. We based the data processing in the content analysis, following the recommended steps for content analysis by Bardin (2009). The study’s results allowed determining that the executed work promotes the teachers professional development, given that it increases the reflexive competence about the pedagogic practice, as well as the development of other competences of praxis, namely, the identification of the most adequate strategies for the resolution of emerging issues in the teacher’s professional everyday life.N/

History and recent progress in ferroelectrets produced in Brazil

More than 30 years ago, a group of researchers in Tampere–Finland developed a thin foamed polymeric material for capacitive sensors. Such soft-voided films exhibited electrical charging characteristics, forming a powerful combination, which resulted in a smart-material with ferroelectric properties. The discovery of the electro-thermo mechanical film (ETMF) has sparked the curiosity of the electret community, leading to the development of several studies. At that time, ETMF became known as cellular electrets and, later, as ferroelectrets or piezoelectrets regarding their electromechanical properties. This paper provides a timeline review of the research on ferroelectrets produced in Brazil, between the years 1990 and 2020, towards demonstrating how the interest in the electret electrical charging mechanism has resulted in the use of ferroelectrets with well-controlled cavities for ultrasound applications

New piezoelectrets: manufacturing process and characterization

No final da década de 90, foi observado que filmes de espumas poliméricas carregadas eletricamente poderiam apresentar elevados coeficientes piezoelétricos quando eletricamente carregados. Isso devido a macro dipolos elétricos, formados por cargas elétrica opostas aprisionadas nas superfícies internas das cavidades do material. Esses filmes porosos, receberam os nomes de piezoeletretos ou ferroeletretos. Inicialmente produzidos por microextrusão aerada a partir de polipropileno, esses piezoeletretos estimularam as pesquisas devido aos elevados coeficientes piezoelétricos apresentados. No entanto, à baixa estabilidade térmica desse material, limitou sua aplicação em temperaturas mais elevadas. Isso direcionou as pesquisas para técnicas de produção de espumas com outros materiais. Recentemente, uma nova abordagem com dois filme de Teflon FEP moldados e colados por fusão, mostrou-se viável na produção de estruturas com cavidades fechadas. Por meio desse processo termo-moldado, não só estruturas termicamente mais estáveis foram produzidas mas também com elevados coeficientes piezoelétricos. Porém a principal vantagens desse processo foi a possibilidade de produzir estruturas com cavidades bem definidas, o que permite um carregamento mais uniforme e controle na freqüência de ressonância. Contudo, todos os processos de produção de piezoeletretos apresentados, possuem algumas limitações, como, por exemplo, o controle efetivo das cavidades e limites quanto ao número de camadas, o que tem se observado aumenta a resposta elétrica. Neste trabalho, é apresentada uma nova técnica para a produção de piezoeletretos, baseada em um sistema de laminação. Este possibilita elaborar estruturas com total controle das cavidades, através da fusão de dois poliméricos juntamente com um molde pré-fabricado. Os coeficientes piezoelétricos obtidos com essas estruturas foram similares aos encontrados nas espumas e termicamente mais estáveis quando produzidas com fluoropolímeros. Ainda neste trabalho foram analisadas a influência da altura e largura das cavidades no coeficiente piezoelétrico, o comportamento de estruturas formadas com diferentes polímeros, e também a versatilidade de estruturas com múltiplas camadas.At the end of 90´s, it was observed that electrically charged foams made from polymers films could exhibit very high piezoelectric coefficients, due to macro-dipoles formed by trapped charges in the inner surfaces of the internal voids of the film. This films with small cavities after has been electrically charged received the names of piezoelectrets or ferroelectrects. They were initially prepared from polypropylene grains extruded into films in a physical blow process. However, the low thermal stability of the piezoelectric coefficient presentec by this voided films, motivated researches to explore different materials which were thermically more stables. Recently a new approach, were two Teflon FEP films were molded and fused to produce cavities with bubbles shapes was presented. These thermo-fused structures reveal also to present very high piezoelectric coefficients, after received properly charging. One of the major advantages of this molded structures piezoelectrets is the possibility to create piezoelectrets with well defined voids, which is supposed to provide a more homogeneous charging and a broadband frequency control. Nevertheless, the methods to produce homogenic structures developed so far are still facing problems to control the cavities and to create multi-layer structures. In this work a new process to produce piezoelectrets is presented. The method based on the lamination of two polymer films with a pre-fabricated template provides full control of the air cavities. After the template is removed, a well defined open channel structures is formed. Later when electrodes are deposited on both sides of the fused films the structure is electrically chargec and a piezoelectret with piezoelectric coefficients similar to the foams is formed. With this new controlled process to prepare piezoeletrets several parameters of the cavities were investigated, including the comparison of ferroelectretcs made from different materials and multi-layers samples

Analysis and implementation of methods for the characterization of thermo-formed electrets

O objetivo deste trabalho é aplicar os métodos de medidas dinâmicos dos polímeros piezoelétricos na caracterização dos eletretos termo-formados de Teflon-FEP desenvolvidos no Laboratório de Medidas e Padrões da Escola de Engenharia de São Carlos (EESC) - Universidade de São Paulo (USP). Para isso, foram implementados os métodos dinâmico direto, acústico direto, acústico inverso e interferométrico. Também foram desenvolvidos neste trabalho dois aplicativos computacionais de controle e aquisição de dados dos equipamentos de medidas, Lock-in SR510, osciloscópio Tektronix TDS 210 e gerador de áudio Tektronix CFG253. Esta caracterização é importante porque visa utilizar os eletretos termo-formados como dispositivos eletromecânicos para realizar inúmeras aplicações nas áreas da robótica, da bioengenharia e nas medidas elétricas e mecânicas. A vantagem dos eletretos termo-formados com relação aos demais polímeros piezoelétricos, é que estes são estruturas homogêneas, com grande reprodutibilidade no processo de fabricação e apresentam altos coeficientes piezoelétricos.The aim of this work is to apply the dynamical measurement methods of piezoelectric polymers into the characterization of thermo-formed electrets of Teflon-FEP developed in the Laboratory of Measurements and Standards of the School of Engineering of Sao Carlos (EESC) - University of Sao Paulo (USP). The direct dynamical, direct acoustic, inverse acoustic and interferometric methods are aplyed to implement these measurements. Two routines were also developed to control and realize the data acquisition of the measurement equipments Lock in SR510, Tektronix TDS-210 oscilloscope and Tektronix CFG-253 function generator. The characterization of these termo-formed electret is important because they can be used into electromechanical devices for innumerable applications in the areas such as robotics, bioengineering and electric and mechanic measurements. The advantage of the thermo-formed electrets, compared to all others piezoelectric polymers, is that they are homogeneous structures with reproducible fabrication process, to presenting high piezoelectric coefficients

Template-based fluoroethylenepropylene piezoelectrets with tubular channels for transducer applications

We describe the concept, the fabrication, and the most relevant properties of a piezoelectric-polymer system: Two fluoroethylenepropylene (FEP) films with good electret properties are laminated around a specifically designed and prepared polytetrafluoroethylene (PTFE) template at 300 degrees C. After removing the PTFE template, a two-layer FEP film with open tubular channels is obtained. For electric charging, the two-layer FEP system is subjected to a high electric field. The resulting dielectric barrier discharges inside the tubular channels yield a ferroelectret with high piezoelectricity. d(33) coefficients of up to 160 pC/N have already been achieved on the ferroelectret films. After charging at suitable elevated temperatures, the piezoelectricity is stable at temperatures of at least 130 degrees C. Advantages of the transducer films include ease of fabrication at laboratory or industrial scales, a wide range of possible geometrical and processing parameters, straightforward control of the uniformity of the polymer system, flexibility, and versatility of the soft ferroelectrets, and a large potential for device applications e.g., in the areas of biomedicine, communications, production engineering, sensor systems, environmental monitoring, etc.Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Brazil(DAAD) Deutscher Akademischer Austausch Dienst, GermanyUniversity of Potsdam, GermanyDeutsche Forschungsgemeinschaft (DFG)[QI 65/1-1

Laminated composite based on polyester geotextile fibers and polyurethane resin for coating wood structures

New environmental laws have restricted the use of hardwood trees in overhead power lines structures, such as, poles and cross-arms, leading companies to seek alternative materials. Reforested wood coated with polymeric resin has been proposed as an environmental friendly solution, with improved electrical properties and protection against external agents, e.g. moisture, ultraviolet radiation and fungi. However, the single thin layer of resin, normally applied on such structures reveal to be inefficient, due to be easily damage during handling. In this paper, we present a composite coating, based on geotextile fibers and polyurethane resin that is suitable for wooden structures. Results obtained from two different tree species (from managed and reforested areas) coated with the composite reveal that the additional layer not only provided a stronger adhesion between wood and ccoating layer but also a further improvement in the electrical properties and better protection against abrasion and moisture

Ferroelectrets: Heterogenous polymer electrets with high piezoelectric sensitivity for transducers

Nowadays, the demand for advanced functional materials in transducer technology is growing rapidly. Piezoelectric materials transform mechanical variables (displacement or force) into electrical signals (charge or voltage) and vice versa. They are interesting from both fundamental and application points of view. Ferrooelectrets (also called piezoelectrets) are a relatively young group of piezo-, pyro- and ferroelectric materials. They exhibit ferroic behavior phenomenologically undistinguishable from that of traditional ferroelectrics, although the materials per se are essentially non-polar space-charge electrets with artificial macroscopic dipoles (i.e., internally charged cavities). A lot of work has been done on ferroelectrets and their applications up to now. In this paper, we review and discuss mostly the work done at University of Potsdam on the research and development of ferroelectrets. We will, however, also mention important results from other teams, and prospect the challenges and future progress trend of the field of ferroelectret research