The double cantilever beam test applied to mode I fracture characterization of polyamide 12 processed by selective laser sintering technology

In recent years, parts produced by Selective Laser Sintering (SLS) technology have aroused growing interest due to their valuable potential for end-use applications. However, to ensure the applicability of SLS products for advanced structural purposes, an accurate characterization of their mechanical behaviour is essential, which includes the assessment of fracture performance. Thus, cohesive zone modelling that allows mimicking damage initiation and propagation in quasi-brittle materials is used in this work to identify the cohesive laws of Polyamide 12 parts sintered by SLS with different values of energy density. This has been accomplished with success in this work for pure mode I loading employing the Double Cantilever Beam (DCB) test. In this context, experimental data is used to evaluate the critical energy release rate under quasi-static loading, by means of the Compliance-Based Beam Method (CBBM). The identification of the cohesive laws comprises finite element analysis to achieve accurate agreement with the experimental load-displacement curves obtained under quasi-static loading. The experimental protocols are duly validated for the tested conditions, which includes a developed numerical procedure combined with experimental data.The authors acknowledge the financial support given by FCT through the reference PhD research scholarship 2020.04520.BD, the reference projects UID/CTM/50025/2019 and UID/EEA/04436/2019, the European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project n° 037902; Funding Reference: POCI-01-0247-FEDER-037902], the ‘Laboratório Associado de Energia, Transportes e Aeronáutica’ (LAETA) through the project UID/EMS/50022/2019 and the FCT/MCTES through national funds (PIDDAC)

Floração em acessos de mandioca do banco de germoplasma da Embrapa Amazônia Oriental.

A região Norte é a segunda maior produtora de mandioca do país, atrás apenas da região Nordeste. A floração em mandioca é essencial para a realização de cruzamentos em um programa de melhoramento genético. O BAG de mandioca da Embrapa Amazônia Oriental mantém acessos coletados em diferentes locais, principalmente no Estado do Pará. Visando identificar a incidência de floração nos acessos e o período em que estes florescem, foram feitas visitas semanais a uma parte dos acessos pertencentes ao BAG no período de agosto a dezembro de 2010 e fevereiro a junho de 2011. Ao final das avaliações foi calculada a porcentagem de acessos que floresceram e a porcentagem de floração de cada acesso. Dos 208 acessos verificados, 13,5% apresentaram floração no período avaliado. Os acessos iniciaram a floração aproximadamente aos cinco meses de idade. Houve um grupo de 12 acessos que teve floração precoce, florescendo de 150 a 300 dias após o plantio. Já o segundo grupo, de 16 acessos, iniciou a floração aos 270 dias. O primeiro grupo foi mais uniforme, enquanto o segundo grupo apresentou variações de início e fim de floração.PIBIC-2011

Advanced oxidation of organic matter in natural waters with TiO2 immobilized films

The purpose of this paper is to report the development of a laboratory -scale pilot based on the use of TiO2 photocatalytic thin films for degrading organic matter and pollutants from natural water. The photoreactor consists of a channel inclined with a glass plate coated by TiO2 in both faces and fixed at 1 cm from the bottom. The thin film was immobilized on the glass plates by Sputtering technique. The reactor was designed to be able of reproduce the hydraulic conditions of a water treatment plant. In experimental testing of degradation of organic matter with solar irradiation maximum efficiency of 50% was achieved. At optimal conditions it was possible to exceed the efficiencies of a full scale preozonization in a water treatment plant , thus providing a more sustainable process

Descrição das fases do desenvolvimento reprodutivo da mamoneira visando ao manejo da colheita.

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Metodologia científica: determinação da atividade antioxidante total em frutas pela captura do radical livre ABTSº+.

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Metodologia científica: determinação da atividade antioxidante total em frutas pela captura do radical livre DPPH.

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