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 [...]
- Biomechanics modeling for functional analysis: Sheep modelPublication . Silva, Rui; Amado, Sandra; João, Filipa; Morouço, Pedro; Pascoal-Faria, Paula; Alves, Nuno; Veloso, AntónioThe aim of the present manuscript was to provide information on the suitability of using ovine as models for conducting in vivo bone tissue engineering studies, regarding the biomechanical considerations. Despite the need of knowledge of the animal model used for bone tissue research a good planning and study design is equal important. The purpose of this review is to contribute to extrapolation of reliable data for those who pretend to use the ovine model in tissue engineering and regenerative medicine.
- Computer-aided optimization in additive manufacturing: Processing parameters and 3D scaffold reconstructionPublication . Alves, Nuno; Gaspar, Miguel Belbut; Pascoal-Faria, PaulaScaffolds are implantable bio-absorbable systems capable of regenerating osteoporotic bone or other native tissues. Additive Manufacturing processes are used to produce scaffolds with customized external shape and predefined internal morphology, allowing some control over pore size and distribution. Despite significant advances in Additive Manufacturing processes, the experimental optimization of processing parameters is time-consuming and expensive usually generating biomaterials waste. Moreover, the manufacturing of such polymeric or hybrid scaffolds requires time-consuming human supervision procedures. Subsequently, measurements of the scaffold’s architecture such as filament diameter, distance between two consecutive filaments, pore geometry and size, and total porosity are usually performed using computer tomography or microscopy, which also requires significant human and physical resources. This research work intends to overcome some aforementioned limitations through the development of a novel approach based on in-situ computer-aided optimization of the extrusion-based processing parameters.
- Effects of Scaffold Electrical Properties on Electric Field Delivery in BioreactorsPublication . Meneses, João; Fernandes, Sofia R.; Alves, Nuno; Pascoal-Faria, Paula; Miranda, Pedro CavaleiroIn tissue engineering, cell culture scaffolds have been widely used in combination with electrical stimulation to promote multiple cellular outcomes, like differentiation and proliferation. Nevertheless, the influence of scaffolds on the electric field delivered inside a bioreactor is often ignored and requires a deeper study. By performing numerical analysis in a capacitively coupled setup, this work aimed to predict the effects of the scaffold presence on the electric field, considering multiple combinations of scaffold and culture medium electrical properties. We concluded that the effect of the scaffold on the electric field in the surrounding culture medium was determined by the difference in electrical conductivity of these two materials. The numerical simulations pointed to significant variations in local electric field patterns, which could lead to different cellular outcomes and confound the interpretation of the experimental results.
- 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 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.
- Multi-scale computer simulations of multi-tubular components manufactured by water-assisted injection mouldingPublication . Pascoal-Faria, Paula; Alves, Nuno; Kamma-Lorger, Christina S.; Marques, Rita; Gomes, Marta; Venkat, Anurag; Silva, Rui; Bastos, Lourenço; Carneiro, Filipa; Cunha, Jorge; Mateus, Artur; Mitchell, Geoffrey R.Water assisted injection moulding is a recent development in the manufacturing technology associated with injection moulding. Injection moulding involved the high pressure injection of molten plastic in to a preformed metal mould which defines the exterior of the shape of the object. Water assisted injection moulding is a variant with an addition step in which water is injected into the mould after its has been filled with molten plastic. The water jet sweeps out the molten plastic in its path to leave a hollow tube in which the interior of the part is defined by the water jet. This technology is used for preparing tubular components for use in the automotive industry and for domestic appliances. We have been developing the technology to prepare parts with branches in the tubing. We have used fine-element simulations to explore the relationship between the process parameters and the subsequent final part. Of course such simulations only serve to define the exterior and interior of the tubular part. It is clear from the outline of the technology above that the molten plastic is subjected to a complex pressure and temperature variation with time which vary across the part and its location within the mould. The specification of the part is in most cases is limited to the geometry and the materials which is used in its preparation, in this case polyamide6 with 30% glass fibre. From the development of plastic processes over the last 50 years we have learnt that the properties of plastic part depend critically on the processing pathway and in particular the timescale for the transformation from molten material to the semi-crystalline solid state. We know from the use of small-angle and wide-angle scattering mapping of the structure and morphology of the multi-tubular components that the level of crystallinity and the extent of preferred orientation varies throughout the part and this may lead to warpage and other geometrical changes in the part during its service life. We have set out to explore how we can use the temperature and pressure variation from the finite element modelling to predict the structure and morphology at different regions in the part in order to be able to establish the parameters which yield a geometrically correct part which is also homogenous in its structure and morphology and hence properties. This paper describes the approach we have taken to make progress with this complex matter of simulations on multiple scales and the application of this technique to realistic automotive tubular components.
- Optimalmould - part II: Global optimization of the injection moulding cycle timePublication . Ramos, Carina; Carreira, Pedro; Bartolo, Paulo; Alves, NunoThe time required to produce a plastic part is a key issue in injection moulding process as it strongly determine the cost per part. Several approaches have been proposed to address this problem. However they do not cover all aspects related to the complete cycle time of the injection moulding process, only focusing on steps such as filling time, cooling time and packing time. This paper presents a global optimisation strategy for the injection moulding cycle time, covering all time steps related to the injection moulding process, including a novel mathematical model to predict the ejection time. An industrial case study was considered to validate the proposed approach. The obtained results are very close to the experimental ones. © 2012 American Institute of Physics.
- OPTIMALMOULD | Cooling System Influence in Injection Moulding Cycle Time OptimizationPublication . Ramos, Carina; Carreira, Pedro; Bártolo, Paulo J.; Alves, NunoMost works undertaken on injection moulding cooling time optimization aimed at reducing the time required to produce plastic parts, this way minimizing industrial costs. An optimal cooling system is proposed to improve the injection moulding design. A multi-objective genetic algorithm called NSGA-II is used, to obtain the optimal parameters in the optimal-mould design. This new design method is an efficient tool to get optimal parameters for injection moulding design. A real case study was carried out to test the optimization platform.