Percorrer por autor "Silva, M."
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- An alternative method to produce metal/plastic hybrid components for orthopedics applicationsPublication . Silva, M.; Mateus, A.; Oliveira, D.; Malça, C.The demand for additive processes that provide components with high technological performance became overriding regardless of the application area. For medical applications, the orthopedics field—multimaterial orthoses and splints—can clearly benefit from direct additive manufacturing using a hybrid process instead of the traditional handmade manufacturing, which is slow, expensive, inaccurate, and difficult to reproduce. The ability to provide faster better orthoses, using innovative services and technologies, resulting in lower recovery times, reduced symptoms, and improved functional capacity, result in a significant impact on quality of life and the well-being of citizens. With these purposes, this work presents an integrate methodology, that includes the tridimensional (3D) scanning, 3D computer-aided design modeling, and the direct digital manufacturing of multimaterial orthoses and splints. Nevertheless, additive manufacturing of components with functional gradients, multimaterial components, e.g. metal/plastic is a great challenge since the processing factors for each one of them are very different. This paper proposes the addition of two advanced additive manufacturing technologies, the selective laser melting and the stereolithography, enabling the production of a photopolymerization of the polymer in the voids of a 3D metal mesh previously produced by selective laser melting. Based on biomimetic structures concept, this mesh is subject to a previous design optimization procedure in order to optimize its geometry, minimizing the mass involved and evidencing increased mechanical strength among other characteristics. A prototype of a hybrid additive manufacturing device was developed and its flexibility of construction, geometrical freedom, and different materials processability is demonstrated through the case study—arm orthosis—presented in this work.
- Antioxidant Food Additives – Applications and Side EffectsPublication . Silva, M.; Lidon, F.Antioxidant food additives are added in small amounts to food stuff improve its durability by preventing food from deterioration due to oxidation. There are two main oxidation processes of foodstuff: (I) the enzymatic oxidation of fruits, vegetables, and processed derivatives like juices, soft drinks, jellies and jams; (II) oxidation and rancidity of spreadable fats and cooking fats and oils. So, the agro food companies use antioxidant food additives in a great diversity of food namely meat products, sauces, cheese, canned fish and meat, pre-cooked food, charcuterie and salted products, fruit and vegetables canned, several preserves, jams and jellies, juices and refrigerants, packaged bread, confectionery, cooked and frozen crustaceans, fish, shellfish and mollusc, oils and fats emulsified, and many other food products. The use of food additives with the antioxidant function is regulated in European law and transposed into Portuguese law. There are authorized the use of more them fifty food additives with the antioxidant technological function. The specific applications of each food additive depend of several factors, namely solubility, antioxidant characteristics and safety. Some food antioxidants, such as tocopherols, acid ascorbic and ascorbates, citric acid and citrates, tartaric acid and tartrates, lactic acid and lactates, when applied to foodstuffs do not appear to have side effects in the amounts indicated by the EU regulation. Other antioxidant food additives, such as BHA, BHT, gallates, stannous chloride present meaningful side effects, and should be used in the smallest possible amount, maintaining the necessary technological features. Among side effects that can occur stand out skin rashes and itching, urticarial and eczema, breathing difficulty, sneezing, gastrointestinal upsets, cholesterol in blood, hyperkinesis. This work is a synoptical review of food additives used as antioxidants authorized in the European Union, considering then characteristics, applications and side effects.
- Application of a Hybrid Additive Manufacturing Methodology to Produce a Metal/Polymer Customized Dental ImplantPublication . Silva, M.; Felismina, R.; Mateus, A.; Parreira, P.; Malça, C.In this paper an integrated methodology for implants personalized manufacturing is presented. This methodology materializes the hybrid material implants manufacturing through the integration of two or more advanced Additive Manufacturing (AM) technologies. Furthermore, high strength biomechanical implants with optimized geometry and mass can be manufactured by biomimetic concepts application. The combination of polymers and ceramics or polymers and metal materials (or metal alloys) allows a significant leap in the development and production of a great diversity of components and applications. The combination of advanced additive manufacturing processes, e.g. the Selective Laser Melting (SLM) or Selective Laser Sintering (SLS) and the StereoLithography (SL), make possible the production of parts with almost unlimited geometric freedom and custom multimaterial. The manufacturing flexibility and the processing capacity of the different combinations of materials - metal/polymer - obtained from hybrid additive manufacturing systems - SLM/SL - are demonstrated here by the manufacture of a dental bridge implant.
- Direct Digital Manufacturing: A Challenge to the Artistic Glass ProductionPublication . Felismina, R.; Silva, M.; Mateus, A.; Malça, C.Currently the high hand-labor costs, long production times, lack of automation and high energy consumption associated with the high temperatures required to produce pieces of glass, are identified as the main inhibitors of growth and economic development of the decorative and utility glass industrial sector. Current production processes impose limitations on the complexity of the geometry and shape of the glass pieces to be produced, which in turn greatly restricts the creativity of designers and consequently, the characteristics of differentiation and innovation presented by new products on the market.