Browsing by Issue Date, starting with "2020-06-26"
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- High-performance self-compacting concrete with recycled aggregates from the precast industry: durability assessmentPublication . Barroqueiro, Tiago; Raposeiro Da Silva, Pedro; De Brito, JorgeThe main objective of this paper is to provide the industry with a simple and practical way of disposing and recovering recycled waste from precast reinforced concrete elements rejected during the quality control process, while minimizing the consumption of natural resources in the production of concrete and, consequently, significantly reducing the environmental impact of both (construction and demolition waste and extracting natural aggregates). In other words, with this work, the intention is to evaluate the feasibility of producing high-performance self-compacting concrete with a less environmental impact, by replacing natural aggregates (NA) with fine and coarse recycled aggregates resulting from the precast industry, which allows the future use of this type of aggregates in the industrial process without reservations concerning the expected durability performance. To achieve these objectives, six types of self-compacting concrete (SCC) were produced incorporating diferente amounts of recycled aggregates. Six replacement ratios for fine recycled aggregates (FRA) and coarse recycled aggregates (CRA) were considered: (FRA/CRA) 0/0; 25/25; 50/50; 100/100; 0/100 and 100/0%. Six di_erent tests were carried out to characterize both the main concrete transport mechanisms and the main concrete degradation mechanisms, namely: the immersion water absorption test, capillary water absorption test, oxygen permeability test, chloride migration test, electrical resistivity test and carbonation test. The obtained results clearly demonstrate that, despite the negative influence of the inclusion of recycled aggregates, it is still possible to produce high-performance self-compacting concrete with perfectly acceptable durability properties.
- A aprendizagem numa comunidade de prática: apropriação dos instrumentos de pilotagem por parte dos novatosPublication . Batalha, Ana Sofia Andrade; Almeida, TiagoO presente relatório foi elaborado no âmbito da Unidade Curricular (UC) de Prática Profissional Supervisionada II (PPS II), a qual decorreu numa Instituição Particular de Solidariedade Social (IPSS) de Lisboa, com um grupo de 21 crianças com idades compreendidas entre os 2 e os 5 anos. Esta é uma instituição que pretende ser um apoio para as famílias do bairro em que está inserida, oferecendo uma resposta educativa ao nível de creche e jardim de infância (JI). É ainda uma instituição que se rege pelo modelo pedagógico do Movimento da Escola Moderna (MEM). Este relatório tem como objetivo apresentar e descrever o caminho percorrido durante os quatro meses de intervenção pedagógica e desenvolvimento de uma atitude investigativa, enquanto educadora estagiária. Neste sentido, será apresentada ao leitor, numa primeira fase, a caracterização do contexto em questão, assim como as intencionalidades que guiaram o percurso realizado, sendo ainda explicitados os moldes em que decorreu a avaliação de toda a intervenção. Numa segunda fase, será apresentada a investigação realizada no contexto descrito, a qual incide no processo de apropriação dos instrumentos de pilotagem por parte dos novatos do grupo tendo em consideração os veteranos do mesmo. Este tema surgiu devido aos vários níveis de familiaridade das crianças da sala para com estes instrumentos, principalmente devido ao tempo em que estão inseridos na sala em questão. A investigação teve como objetivo, aquando da utilização dos instrumentos de pilotagem (diário, contar, mostrar ou escrever e mapa das comunicações), identificar o modo como os novatos se apropriam destes através da interação com os veteranos. Os resultados indicam que uma parte do grupo de novatos se apropria destes instrumentos apenas estando envolvido numa comunidade de prática e tendo como exemplo as ações realizadas pelos veteranos. No entanto, algumas destas crianças necessitam de um apoio mais próximo por parte do educador para que consigam atribuir significado a estes instrumentos e utilizar os mesmos com o objetivo de comunicar em grupo.
- Mechanochemical preparation of Pd(II) and Pt(II) composites with carbonaceous materials and their application in the Suzuki-Miyaura reaction at several energy inputsPublication . Soliman, Mohamed Mostafa Aboelhassan; Peixoto, Andreia F.; Da Costa Ribeiro, Ana Paula; Kopylovich, Maximilian; Alegria, Elisabete; Pombeiro, ArmandoPd(II) and Pt(II) composites with activated carbon (AC), graphene oxide, and multiwalled carbon nanotubes were prepared by ball milling and used as catalysts for the Suzuki-Miyaura reaction, under several energy inputs (mechanical grinding, conventional heating, and microwave irradiation). The catalytic composites were characterized by ICP-MS, BET, XPS analyses, TEM, and SEM. The average particle size of the prepared composites was estimated to be in the range of 6-30 nm, while the loadings of Pd and Pt did not significantly affect the surface area of the AC support due to the tendency to agglomerate as observed by the TEM analysis. The Pd/AC composites exhibit high mechanochemical catalytic activity in cross-coupling of bromobenzene and phenylboronic acid with molar yields up to 80% with TON and TOF of 222 and 444 h(-1), respectively, achieved with Pd(4.7 wt%)-AC catalyst under the liquid assisted grinding for 0.5 h at ambient conditions, using cyclohexene as an additive.
- Hand-to-mouth consumers, rule-of-thumb savers, and optimal controlPublication . Gomes, OrlandoContemporaneous research in macroeconomics is experiencing a methodological transition. The well-established representative agent optimal control model, which has served for many decades as the fundamental point of reference to approach most of the aggregate phenomena in economics, is being gradually adapted or replaced. In the new settings, agent heterogeneity prevails: while some agents eventually continue to take optimal intertemporal decisions, others do not possess the ability or the willingness to do so, and therefore resort to simple heuristics in their decision-making processes. In this study, the basic Ramsey growth model of intertemporal choice is reinterpreted in the light of the heterogeneity assumption. Four different frameworks are proposed, and the respective dynamics investigated; these frameworks contemplate: (i) the coexistence of optimal planners and hand-to-mouth consumers; (ii) the coexistence of optimal planners and rule-of-thumb savers; (iii) intertemporal discount rate heterogeneity with endogenous determination of hand-to-mouth behavior; (iv) absence of optimal planning and full heuristic behavior. The derived results point to a richness of outcomes that can only be unveiled once the simple dynamic growth setup is expanded to include different consumption-savings profiles.