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Browsing ESTG - Artigos em revistas internacionais by Sustainable Development Goals (SDG) "12:Produção e Consumo Sustentáveis"
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- 3D printing of new biobased unsaturated polyesters by microstereo-thermal-lithographyPublication . Gonçalves, Filipa A. M. M.; Costa, Cátia S. M. F.; Fabela, Inês G. P.; Farinha, Dina; Faneca, Henrique; Simões, Pedro N.; Serra, Arménio C.; Bártolo, Paulo J.; Coelho, Jorge F. J.New micro three-dimensional (3D) scaffolds using biobased unsaturated polyesters (UPs) were prepared by microstereo-thermal-lithography (μSTLG). This advanced processing technique offers indubitable advantages over traditional printing methods. The accuracy and roughness of the 3D structures were evaluated by scanning electron microscopy and infinite focus microscopy, revealing a suitable roughness for cell attachment. UPs were synthesized by bulk polycondensation between biobased aliphatic diacids (succinic, adipic and sebacic acid) and two different glycols (propylene glycol and diethylene glycol) using fumaric acid as the source of double bonds. The chemical structures of the new oligomers were confirmed by proton nuclear magnetic resonance spectra, attenuated total reflectance Fourier transform infrared spectroscopy and matrix assisted laser desorption/ionization-time of flight mass spectrometry. The thermal and mechanical properties of the UPs were evaluated to determine the influence of the diacid/glycol ratio and the type of diacid in the polyester's properties. In addition an extensive thermal characterization of the polyesters is reported. The data presented in this work opens the possibility for the use of biobased polyesters in additive manufacturing technologies as a route to prepare biodegradable tailor made scaffolds that have potential applications in a tissue engineering area.
- Additive manufactured porous biomaterials targeting orthopedic implants: A suitable combination of mechanical, physical and topological propertiesPublication . Bartolomeu, F.; Dourado, N.; Pereira, F.; Alves, N.; Miranda, G.; Silva, F. S.Orthopedic implants are under incessant advancement to improve their interactions with surrounding bone tissue aiming to ensure successful outcomes for patients. A successful biological interaction between implant and surrounding bone depends on the combination of mechanical, physical and topological properties. Hence, Ti6Al4V cellular structures appear as very promising solutions towards the improvement of conventional orthopedic implants. This work addresses a set of fundamental tools that allow improving the design of Ti6Al4V cellular structures produced by Selective Laser Melting (SLM). Three-point bending tests were carried out to estimate the elastic modulus of the produced structures. Morphological analysis allowed to evaluate the dimensional differences that were noticed between the model CAD and the SLM structures. Finite element models (adjusted CAD) were constructed with the experimentally obtained dimensions to replicate the mechanical response of the SLM structures. Linear correlations were systematically found for the dimensions of the SLM structures as a function of the designed model CAD dimensions. This has also been observed for the measured porosities as a function of the designed CAD models. This data can be used in further FE analyses as design guidelines to help engineers fabricating near-net-shape SLM Ti6Al4V cellular structures. Besides, polished and sandblasted surface treatments performed on the Ti6Al4V cellular structures allowed to obtain suitable properties regarding roughness and wettability when compared to as-produced surfaces. The capillarity tests showed that all the analyzed Ti6Al4V structures are able to transport fluid along its structure. The cell viability tests demonstrate Ti6Al4V cellular structures SLM produced did not release toxic substances to the medium, indicating that these structures can assure a suitable environment for cells to proliferate and attach. This study proposes a design methodology for Ti6Al4V cellular structures, that owe suitable mechanical properties but also provide a proper combination of porosity, roughness, wettability, capillarity and cell viability, all of them relevant for orthopedic applications. A Ti6Al4V cellular structured hip implant prototype gathering the suitable features addressed in this study was successfully SLM-produced.
- An automated system for 3D printing functionally graded concrete-based materialsPublication . Craveiro, Flávio; Nazarian, Shadi; Bartolo, Helena; Bartolo, Paulo Jorge; Duarte, José PintoIn recent years, the interest in developing additive manufacturing (AM) technologies in the architecture, engineering and construction (AEC) industry has increased, motivated by the potential to support greater formal complexity. In this context, AM has been largely used to design and fabricate physical parts with homogeneous materials. This paper proposes a new strategy, aimed at the design and fabrication of functionally graded concrete parts with specific thermo-mechanical performance. The paper describes the development of the AM system to materialize such parts. The computational tool developed to design the material to meet specific performance requirements, and the design and testing of the material are described elsewhere. A functionally graded concrete part obtained by replacing sand with cork was produced and is evaluated.
- Biomanufacturing for tissue engineering: Present and future trendsPublication . Bartolo, Paulo; Chua, C. K.; Almeida, Henrique de Amorim; Chou, S. M.; Lim, A. S. C.Tissue engineering, often referred to as regenerative medicine and reparative medicine, is an interdisciplinary field that necessitates the combined effort of cell biologists, engineers, material scientists, mathematicians, geneticists, and clinicians toward the development of biological substitutes that restore, maintain, or improve tissue function. It has emerged as a rapidly expanding approach to address the organ shortage problem and comprises tissue regeneration and organ substitution. Cells placed on/or within constructs is the most common strategy in tissue engineering. Successful cell seeding depends on fast attachment of cell to scaffolds, high cell survival and uniform cell distribution. The seeding time is strongly dependent on the scaffold material and architecture. Scaffolds provide an initial biochemical substrate for the novel tissue until cells can produce their own extra-cellular matrix (ECM). Thus scaffolds not only define the 3D space for the formation of new tissues, but also serve to provide tissues with appropriate functions. These scaffolds are often critical, both in vivo (within the body) or in vitro (outside the body) mimicking in vivo conditions. Additive fabrication processes represent a new group of non-conventional fabrication techniques recently introduced in the biomedical engineering field. In tissue engineering, additive fabrication processes have been used to produce scaffolds with customised external shape and predefined internal morphology, allowing good control of pore size and pore distribution. This article provides a comprehensive state-of-the-art review of the application of biomanufacturing additive processes in the field of tissue engineering. New and moving trends in biomanufacturing technologies and the concept of direct cell-printing technologies are also discussed.
- Cancellative conjugation semigroups and monoidsPublication . Garrão, A. P.; Martins-Ferreira, Nelson; Raposo, M.; Sobral, M.We show that the category of cancellative conjugation semigroups is weakly Mal’tsev and give a characterization of all admissible diagrams there. In the category of cancellative conjugation monoids we describe, for Schreier split epimorphisms with codomain B and kernel X, all morphisms h: X→ B which induce a reflexive graph, an internal category or an internal groupoid. We describe Schreier split epimorphisms in terms of external actions and consider the notions of precrossed semimodule, crossed semimodule and crossed module in the context of cancellative conjugation monoids. In this category we prove that a relative version of the so-called “Smith is Huq” condition for Schreier split epimorphisms holds as well as other relative conditions.
- Characterisation of Portuguese RC Precast Industrial Building StockPublication . Rodrigues, H.; Sousa, R.; Vitorino, H.; Batalha, N.; Varum, H.; Fernandes, P.; Liu, ZaobaoThe construction of a vulnerability model requires reliable information on the features of the buildings in the study. The purpose of this work is the characterisation of the precast industrial buildings in Portuguese industrial park, based on the survey of 73 design projects of existing buildings. The collected data are based on a previous study on the features that influence the seismic response of this type of buildings. The parameters collected are associated with the global geometry and specific elements characteristics (e.g., column dimensions, reinforcement ratios, and connections details), to the mechanical properties of the materials and other parameters that can give some important information in the characterisation of the buildings (e.g., construction year and localization). In the end, a comparison with other available databases, namely, from Italy and Turkey, is done in order to conclude about the similarity. This information is important to define representative experimental specimens and numerical simulation to conduce seismic risk analysis.
- Comentário ao Processo C-324/17, Gavanozov, 24 de outubro de 2019: O princípio do reconhecimento mútuo versus Direitos FundamentaisPublication . Castilhos, Daniela Serra; Pacheco, Fátima; Barata, Mário SimõesO artigo dedica-se à análise e comentário da decisão resultante do Processo (C-324/17, Gavanozov, de 24 de outubro de 2019) que constitui a primeira decisão do Tribunal de Justiça da União Europeia relativamente à Decisão Europeia de Investigação. Para tanto, pretende fazer-se o enquadramento da cooperação judiciária em matéria penal e do princípio do reconhecimento mútuo. Começa-se por analisar a Diretiva 2014/41/UE que aprovou a Decisão Europeia de Investigação (DEI), integrando-a no Espaço da Liberdade, Justiça e Segurança. São igualmente considerados os motivos de não reconhecimento ou de não execução de uma DEI, nomeadamente aqueles que se prendem com os direitos fundamentais. Por fim, analisa-se o litígio e a questão prejudicial colocada, bem como as conclusões do Advogado-geral, na perspetiva de avaliar se houve, no caso, uma violação dos direitos fundamentais, designadamente os Artigos 47º e 48º da Carta dos Direitos Fundamentais da União Europeia, pela autoridade judicial de emissão na Bulgária.
- Component redundancy allocation in optimal cost preventive maintenance schedulingPublication . Siopa, Jorge; Garção, José Eugénio Semedo; Silva, Júlio Montalvão eThis work presents a methodology to assist maintenance teams in defining the maintenance schedule and redundancy allocation that minimise the life-cycle average cost of a system. The minimal data required are three average costs and one reliability function. This methodology is useful in a system design phase, since in this situation data is usually scarce or inaccurate, but can also be applied in the exploration phase. It consists of an adaptation of the classical optimal age replacement method, combined with a redundancy allocation problem. A set of simple illustrative examples covering a variety of operating conditions is presented, demonstrating quantitatively the applicability of the methodology to a range of maintenance optimisation decisions.
- O conceito de “autoridade judiciária de emissão” a partir dos Processos apensos C-508/18 e C-82/19 PPU (Caso Parquet de Lübeck) e eventuais ecos na Decisão Europeia de Investigação em PortugalPublication . Guimarães, Ana Paula; Castilhos, Daniela Serra; Barata, Mário SimõesNa interpretação dada pelo Tribunal de Justiça da União Europeia, no caso Parquet de Lübeck, que versa sobre matéria do mandado de detenção europeu, do conceito de “autoridade judiciária de emissão” ficam excluídas as Procuradorias por força de estas poderem ser permeáveis a influência direta ou indireta do poder executivo. Por sua vez, o Ministério Público é “autoridade de emissão” em sede de decisões europeias de investigação em matéria penal, nos termos do artigo 3.º, alínea c), da Lei n.º 88/2017, de 21 de agosto, que transpôs a Diretiva 2014/41/UE, do Parlamento Europeu e do Conselho, de 3 de abril de 2014. Tendo em consideração a autonomia e hierarquia do Ministério Público e o modo de nomeação e exoneração do Procurador-Geral da República, procuramos ver se o decidido no Acórdão supra referido teria alguma repercussão ao nível da competência do Ministério Público para emissão de uma decisão europeia de investigação. Concluímos em sentido negativo. O Ministério Público não depende do Ministro da Justiça, tem consagração constitucional e atribuições definidas na lei e respetivo estatuto e só pode emitir uma decisão europeia de investigação restrita aos atos processuais que são da sua competência nos termos da lei interna.
- Design of a Video Otoscope Prototype with an Integrated Scanner for Hearing Aid Direct Digital Manufacturing: A Preliminary StudyPublication . Ganhão, Francisco; Santos, António Carvalho; Silva, Carla; Monteiro de Moura, Carla SofiaIn the current landscape of hearing rehabilitation, ear mold manufacturing typically involves the injection of silicone into the external ear canal (EEC) of each patient. This invasive procedure poses several risks, including the potential for silicone residue retention and tympanic membrane perforation, which may necessitate surgical intervention. To mitigate these risks, we present the design of a video otoscope that integrates a scanner capable of capturing high-precision, real-time images of the EEC’s geometry. The developed device allows (i) the generation of a 3D CAD model leading to the direct, quick, and low-cost production of customized hearing aids using 3D printing and (ii) the establishment of medical protocols for carrying out diagnoses and monitoring of hearing pathology evolution using methodologies based on Artificial Intelligence. Furthermore, the use of customized hearing aids that allow the application of Rhythmic Auditory Stimulation (RAS) and music therapy enhances audiology as an alternative and innovative way to treat cognitive and degenerative diseases, as well as pathological disorders.