CDRsp - Comunicações em conferências internacionais
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- Additive manufactured stoneware fired in microwave furnacePublication . Santos, Tiago; Ramani, Melinda; Devesa, Susana; Batista, Catarina; Franco, Margarida; Duarte, Isabel; Costa, Luís; Ferreira, Nelson; Alves, Nuno; Pascoal-Faria, PaulaAdditive manufacturing (AM) techniques have revolutionized the concept of building parts not only in laboratory contexts but also in industry environments and can be applied to distinct fields such as the health, automotive and aeronautics sectors [...]
- Aerodynamics of a wheelchair sprinter racing at the 100m world record pace by CFDPublication . Forte, Pedro; Marinho, Daniel A.; Morais, Jorge E.; Morouço, Pedro; Pascoal-Faria, Paula; Barbosa, Tiago M.The aim of this study was to analyze aerodynamics in a racing position of a wheelchair-racing sprinter, at the world record speed. The athlete and wheelchair were scanned at the beginning of the propulsive phase position (hands near the handrims at 12h) for the 3D model acquisition. Numerical simulation was run on Fluent, having as output the pressure, viscosity and total drag force, and respective coefficients of drag at the world record speed in T-52 category. Total drag was 7.56N and coefficient of drag was 1.65. This work helped on getting a deeper insight about the aerodynamic profile of a wheelchair-racing athlete, at a 100m world record speed.
- Comparison by computer fluid dynamics of the drag force acting upon two helmets for wheelchair racersPublication . Forte, P; Marinho, D. A.; Morouço, P; Pascoal-Faria, P.; Barbosa, T. M.The aim of this study was to compare the drag force created by two helmets (time trial and road)used by a wheelchair racer. The head and helmet of the racer were scanned to obtain the3D models. Numerical simulation was run on Fluent, having as output the drag force for both helmets (road and time trial) in two different positions (0º and 90º) and increasing velocities (from 2.0 to 6.5 m/s). The greatest aerodynamic drag was noted wearing a time trial helmet in 90º ranging from 0.1025N to 0.8475N; this was also the position with the highest drag. The velocity with higher drag for booth helmets was at 6.5 m/s. The time trial helmet at 0º had the lower aerodynamic drag, compared with the same position of road helmet. The drag force seems to be lower wearing the time trial helmet and keeping the 0º position and, thus, should be considered for sprinting events.
- DLL architecture for OFDM based VLC transceivers in FPGAPublication . Duarte, Luis; Rodrigues, Luis; Alves, Luis N.; Ribeiro, Carlos; Figueiredo, MónicaThis paper addresses the problem of achieving high bandwidth in a DLL design for OFDM based VLC broadcast systems. It describes the implementation of efficient Data Link Layer (DLL) and Forward Error Correction (FEC) modules in a Xilinx FPGA. The proposed DLL aims at furnishing the adequate means to fragment and route both high data-rate (HDR) and moderate data-rate (MDR) service requests while maintaining a continuous transmission flow. The FEC modules aims at providing sufficient error correction capabilities with reasonable computation overheads. Another goal was to develop these modules under a globally asynchronous locally synchronous paradigm, ensuring high modularity and performance.
- A eficiência da materialidade - O recurso a ferramentas digitais de simulação e fabricação aditiva na procura de uma maior eficácia dos dispositivosPublication . Gonçalves, Sérgio; Mateus, João Vasco; Hernandis-Ortuño, BernabéA praxis do Design de produtos, condicionada pelas crises sociais e ambientais que o mundo atravessa, deve passar pela procura de uma cada vez maior eficiência dos objetos na sua dimensão ambiental. Embora esta questão esteja a jusante de questões eventualmente mais relevantes na minimização deste problema, e que têm a ver com a legitimação da própria existência dos dispositivos, a otimização do recurso a matérias primas no fabrico de objetos é de fulcral importância. A possibilidade de otimizar os produtos pela redução da incorporação de matéria prima no seu fabrico e adequar o material a uma determinada utilização é central no seu processo de desenvolvimento. Por outro lado, as novas possibilidades trazidas pela fabricação aditiva no sentido de reduzir a quantidade de materiais e processos industriais associados à produção de componentes técnicos complexos permite perspetivar uma melhoria significativa do impacto ambiental tradicionalmente associado à sua obtenção. O presente artigo procura examinar como as tecnologias digitais de análise, otimização e fabricação aditiva poderão constituir uma resposta viável para uma produção mais eficiente do ponto de vista da incorporação de recursos não-renováveis e da minimização do impacto ambiental associado às tecnologias de produção tradicionais.
- Finite element analysis of a human temporomandibular joint disc: Preliminary resultsPublication . Gomes, Sara; Ângelo, David; Pascoal-Faria, Paula; Mateus, Artur; Alves, NunoThe temporomandibular joint (TMJ) is an important joint that plays a paramount role during the mandibular movement. TMJ disc is an essential component in the normal TMJ, interposed between the mandibular condyle and temporal fossa with the following functions: it distributes the intra-articular load, stabilizes the joints during translation and decreases the wear of the articular surface. The mechanical behaviour study of this element is therefore essential to provide alternative solutions when its replacement becomes essential. The aim of this study is to present a preliminary three dimensional mechanical model to study the stresses distributions at TMJ disc and to provide an efficient tool as an alternative to experimental preclinical studies. The human mandibular condyle, the TMJ disc and the temporal fossa were considered to build the finite element model; additionally, two types of connections were used between the disc and the bone simulating the retrodiscal tissue and lateral pterygoid muscle: frictionless and bonded. At this stage, the elastic behaviour of materials was taken into account. Results show that the computed von Mises stresses are in accordance with previous studies.
- A finite element method to study multimaterial wind towersPublication . Pascoal-Faria, P.; Dias, C.; Oliveira, M; Alves, N.Wind towers are used to produce electrical energy from the wind. A significant number of towers is manufactured using tubular separately steel or concrete, having limitations such as maximum diameter and height imposed essentially by transportation limitations. Developed computational studies on structural design of towers have been mainly focused on a single material. This investigation aims to develop a finite element method able to study structural design of wind towers combining different materials. The finite element model combines solid and shell elements encompassing different geometries. Several case studies are considered to validate the proposed method and accurate results are obtained.
- Further remarks on the "Smith is Huq" conditionPublication . Martins-Ferreira, Nelson; Van der Linden, TimWe compare the Smith is Huq condition (SH) with three commutator conditions in semi-abelian categories: first an apparently weaker condition which arose in joint work with Bourn and turns out to be equivalent with (SH), then an apparently equivalent condition which takes commutation of non-normal subobjects into account and turns out to be stronger than (SH). This leads to the even stronger condition that weighted commutators in the sense of Gran, Janelidze and Ursini are independent of the chosen weight, which is known to be false for groups but turns out to be true in any two-nilpotent semi-abelian category.
- A method for automatic detection of rectangular regions of interest in arbitrary imagesPublication . Martins-Ferreira, Nelson; Ferreira, Lino; Pascoal-Faria, Paula; Cruz, Luis A. da Silva; Assunção, Pedro; Alves, NunoThis paper presents a computational method to extract optimum rectangular Regions of Interest (RoI) in images with an associated saliency map. Although saliency maps provide an individual relevance measure for each pixel, to find the sub-image (i.e., rectangular region) that contains the set of the most relevant pixels requires an optimisation procedure to define the boundaries of the best RoI. This is achieved by the method devised in the paper, by following an approach based on balancing the amount of relevant information that is included and excluded from the RoI. The results show that such method is capable of finding the most relevant rectangular RoI and thus to extract the optimum sub-images according to the relevance measure given by a generic saliency map. Since the method is not tied to any particular type of images, it finds application in quite different fields, such as salient object extraction and processing in industry and surveillance, image compression using attention modelling, biomedical imaging, etc.
- Micro-cooling constructal design: An application to mold inserts thermal managementPublication . Clemente, Miguel R.; Panão, Miguel R.; Pascoal-Faria, Paula; Alves, NunoMold thermal performance has a direct influence on part properties, quality and defects, and mold productivity. Through additive manufacturing, inserts can be developed with features that respect the necessary high complex geometries the part requires and that increase thermal performance. Constructal design is explored as a design tool to produce guidelines for cooling channels development.