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- Utilização de representações visuaisPublication . Caetano, Fernando J. P.
- Desafiando o paradigma do ensino da química: o contributo da Universidade Aberta de PortugalPublication . Oliveira, Carla Padrel de; Caetano, Fernando J. P.A Universidade tem, ao longo dos anos, mantido uma enorme capacidade para se transformar e adaptar à evolução do Mundo e esse sentido de mudança é também plasmado na constante procura de novos caminhos, novas ideias e novas soluções. Pretende-se com este artigo apresentar o modelo pedagógico da Universidade Aberta – universidade pública portuguesa de ensino a distância – e em particular a sua aplicação ao ensino da química em contexto de e-learning e no âmbito do curso de 1º ciclo em Ciências do Ambiente. São apresentadas as diferentes estratégias que têm vindo a ser desenvolvidas, nomeadamente o recurso a trabalho experimental, o acesso a laboratórios virtuais e a disponibilização de feedback para as atividades formativas e avaliativas.
- Tris(2-Ethylhexyl) trimellitate (TOTM) a potential reference fluid for high viscosity. Part II: Density measurements at temperatures from (293 to 373) K and pressures up to 68MPaPublication . Diogo, João C. F.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.In Part I of the present work we describe the viscosity measurements performed on tris(2-ethylhexyl) trimellitate or 1,2,4-benzenetricarboxylic acid, tris(2-ethylhexyl) ester (TOTM) up to 65MPa and at six temperatures from (303 to 373) K, using a new vibrating-wire instrument. The main aim is to contribute to the proposal of that liquid as a potential reference fluid for high viscosity, high pressure and high temperature. The present Part II is dedicated to report the density measurements of TOTM necessary, not only to compute the viscosity data presented in Part I, but also as complementary data for the mentioned proposal. The present density measurements were obtained using a vibrating U-tube densimeter, model DMA HP, using model DMA5000 as a reading unit, both instruments from Anton Paar GmbH. The measurements were performed along five isotherms from (293 to 373)K and at eleven different pressures up to 68MPa. As far as the authors are aware, the viscosity and density results are the first, above atmospheric pressure, to be published for TOTM. Due to TOTM’s high viscosity, its density data were corrected for the viscosity effect on the U-tube density measurements. This effect was estimated using two Newtonian viscosity standard liquids, 20 AW and 200 GW. The density data were correlated with temperature and pressure using a modified Tait equation. The expanded uncertainty of the present density results is estimated as 0.2% at a 95% confidence level. Those results were correlated with temperature and pressure by a modified Tait equation, with deviations within 0.25%. Furthermore, the isothermal compressibility, kT, and the isobaric thermal expansivity, ap, were obtained by derivation of the modified Tait equation used for correlating the density data. The corresponding uncertainties, at a 95% confidence level, are estimated to be less than 1.5% and 1.2%, respectively. No isobaric thermal expansivity and isothermal compressibility for TOTM were found in the literature.
- Volumetric properties and spectroscopic studies of pyridine or nicotine solutions in liquid polyethylene glycolsPublication . Visak, Zoran P.; Ilharco, Laura; Garcia, Ana Rosa; Najdanovic-Visak, Vesna; Fareleira, João M. N. A.; Caetano, Fernando J. P.; Kijevcanin, Mirjana; Serbanovic, SlobodanDensities and molar excess volumes of the solutions of pyridine or nicotine in liquid polyethylene glycol, PEG200 and PEG400, have been determined at several temperatures. The experimental molar excess volumes are negative, thus indicating strong attractive interactions between the components, as could be expected considering their highly polar nature and good hydrogen bond abilities. For the pyridine systems, this negativity is slightly increased as the temperature rises, while the opposite tendency is observed for the nicotine mixtures. When pyridine and nicotine solutions are compared, the former—particularly those with PEG400—exhibit substantially more negative molar excess volumes than the latter. The effect of the polymer chain length on the results for the nicotine solutions is almost negligible. However, this is not the case when pyridine is one of the components: a longer chain induced considerably higher compression on mixing. The Fourier-transform infrared analysis allowed interpretation of the negative experimental molar excess volumes in terms of specific inter- and intramolecular interactions.
- Viscosity measurements of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIM OTf) at high pressures using the vibrating wire techniquePublication . Sequeira, Maria Carolina; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.The goal of the present work is to contribute to the characterization of ionic liquids by measuring their viscosity at high pressures. As 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIM OTf) has been used as a solvent in CO2 capture processes, the temperature and pressure ranges of the measurements cover the intervals used in those processes. Measurements of the viscosity of EMIM OTf along five isotherms in the range (298–358) K and at pressures up to 50 MPa, have been performed using the vibrating wire technique in the forced mode of operation. As far as the authors are aware, these are the first measurements of this ionic liquid at pressures higher than 0.1 MPa, to be published. The viscosity results were correlated with the molar volume, using a modified hard-spheres model. The root mean square (σ) deviation of the data from the correlation is less than 0.5% The expanded uncertainty of the present viscosity data is estimated as ±2.0% at a 95% confidence level. As a complement, the pressure-viscosity coefficient has been calculated within the temperature range of the present results. Previous studies of the influence of the electric conductivity of ionic liquids, including EMIM OTf, in the vibrating wire method, have been taken into account for the present work. Complementary measurements of the density have been performed along seven isotherms in the temperature range from (298–363) K and pressures from (0.1–70) MPa. The density measurements were carried out with an Anton Paar vibrating U-tube densimeter and the raw data were corrected for viscosity effects. The density results were correlated with the temperature and pressure using a modified Tait equation. The expanded uncertainty of the present density data is estimated as ±0.2% at a 95% confidence level.
- Relatório de Atividades do Conselho Científico: 2018Publication . Alves, Carlos Duarte; Pimentel, Carmen; Fonseca, Sónia; Caetano, Fernando J. P.; Marcos, Adérito
- Quest for a reference standard for viscosity at high temperatures and high pressuresPublication . Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Diogo, João C. F.; Fareleira, João M. N. A.; Pereira, Marta F. V.; Santos, Fernando J. V.; Santos, Tânia V. M.; Wakeham, William A.This communication is dedicated to give notice of the present situation concerning the proposal of tris(2-ethylhexyl) trimellitate (TOTM) to be a reference standard fluid for viscosity at high temperatures and high pressures. This proposal stems from an internal project of the International Association for Transport Properties (IATP). A general overview of the efforts carried out so far by the scientific community towards that objective will be made. This will be complemented by a description of its main characteristics that support its proposal. In particular, the present work is concerned with the determination of the shear dependence of the viscosity of TOTM. Moreover, new results for the density of TOTM at moderately high temperatures and pressures up to 70 MPa are presented.
- Viscosity of liquid diethylene, triethylene and tetraethylene glycols at moderately high pressures using a vibrating wire instrumentPublication . Pereira, Marta F. V.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.New viscosity measurements of compressed liquid diethylene glycol (DiEG), triethylene glycol (TriEG) and tetraethylene glycol (TeEG) have been performed using a vibrating wire instrument operated in the forced oscillation mode. The measurements have been carried out in a range of pressures up to 70 MPa and temperatures from (293 - 363) K, covering a total range of viscosities from (3.46 - 1.15 x 10^2) mPa,s. Complementary experimental density data were obtained for the same glycols using an Anton Paar vibrating U-tube densimeter. These measurements have been performed in a range of temperatures from about (283 - 363) K and at pressures up to about 70MPa. The viscosity results were correlated with density, using a modified hard-spheres scheme. The experimental density data were correlated, as a function of temperature and pressure, with a modified Tait-type equation. The expanded uncertainty of the present viscosity results at a 95% confidence level is estimated to be less than ±2.0% for viscosities up to 68 mPa s and less than ±2.6% for higher viscosities. The densities have an expanded uncertainty of ±0.2% at a 95% confidence level.
- Microcredentials: an opportunity towards the digital transformationPublication . Caetano, Fernando J. P.; Casanova, Diogo; Moreira, DarlindaThis communication aims to present one of the online courses included in the Microcredentials portfolio of the Universidade Aberta, in Portugal. We start by presenting a framework of the European guidelines on Microcredentials, defining its main characteristics, namely highlighting its advantages in the context of reskilling or upskilling with a view to its applicability in the labor sector. Following the guidelines of the Portuguese Ministry of Higher Education, and specific EU funding under the Impulso Adultos programme, a proposal for a Microcredential in Digital and Distance Learning was conceptualized and developed for teachers´ training, with more than 1200 teachers already involved. An evaluation carried out through a survey delivered to trainees shows very positive results in all items evaluated, with strong emphasis on the transferability and applicability of the knowledge acquired to work contexts. These results show that this course, developed within the scope of Microcredentials, broadly meets the needs of reskilling and upskilling, which are increasingly important in the adaptability of adults to the new challenges that digital transformation implies.
- Compreender o efeito das emissões de carbono sobre a biodiversidade em meio aquáticoPublication . Caetano, Fernando J. P.