Percorrer por autor "Silva, A."
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- Enabling Cyber-Physical Systems for Industry 4.0 operations: A Service Science PerspectivePublication . Dionísio, Andreia; Almeida, Isabel; Silva, AgostinhoBased on the Internet of Things (IoT) and Smart Technologies, manufacturing industries are witnessing the fourth Industrial Revolution, the Industry 4.0 (I4.0), and digital transformation is a keystone in this change. Cyber-Physical Systems (CPS) are strategic in thoroughly digitalizing companies, and I4.0 operations depend on CPS efficiency. Digital plants are held by digital technologies that provide excellent tools for improving product security and supply chain security but requires structured information management to maintain the CPS in its highest level of efficiency. These systems are overly complex and hard to handle when several CPS need to be combined as in a large factory, where several machines must work together to achieve a common goal. This research addresses these issues, and we propose an information management framework of industrial CPS that, towards the industrial efficiency, affords an increase in value for all stakeholders. The framework structures the information through the introduction of two innovative value co-creation concepts: (i) Fingerprint (FP-I4.0), a virtual vehicle that can carry two types of structured information and (ii) Cockpit4.0, an interaction entity between the various service systems, applied from cradle-to-cradle. Validated through the Service Science Theory, we conclude that the proposed empirical framework may boost up CPS efficiency and, from it, I4.0 operations will be more effective
- Flexible-lean processes optimization: A case study in stone sectorPublication . Dionísio, Andreia; Coelho, Luís; Silva, AgostinhoDuring the downturn in demand in Engineering and Construction Architecture (AEC) activities registered in 2007, the Cluster of Mineral Resources of Portugal (CPMR) put into practice an initiative to boost the Ornamental Stone sector, based on incorporating lean thinking concepts, combined with techniques and technologies to make production processes more flexible. This was called the leanstone hornbook (LH). Since then, the LH has been adopted by several Portuguese Ornamental Stone (OS) companies. For these companies, using the LH means changing their operations to a new model based on (i) their participation in R&D consortium projects, (ii) incorporating the resulting innovations, and (iii) combining innovation with lean thinking. Based on a convenience sample of OS companies, the objective of this research was to assess the economic-financial impact of leanstone operations on Portuguese OS companies. Through a methodological framework based on Key Performance Indicators (KPI) and Innovation Outcomes (IO), indexed to companies’ economic-financial performance, LH was found to generate a potentially positive impact in terms of sales volume, exports, investment capacity and net result.
- An iterative pilot-data aided estimator for OFDM-based relay-assisted systemsPublication . Neves, D.; Ribeiro, Carlos; Silva, A.; Gameiro, A.We propose and assess a pilot-data aided channel estimation scheme for realistic relay-assisted scenarios designed for the downlink SFBC OFDM-based systems. We consider that both the base station and the relay node are equipped with an antenna array whereas the user terminal is a single antenna device. The relay protocol considered is equalise-and-forward. The channel estimation method iteratively uses the information carried by the pilots and data to improve the estimate of the equivalent channels for the path Base Station - Relay Node - User Terminal. The MMSE criterion is used in the design of the estimator for both the pilot-based and data-aided iterations. The results show the benefits of cooperation in terms of MSE and also show that the proposed scheme allows, with a single data iteration, a reduction of the number of pilots when compared with non-data-aided schemes.
- Mysterious Bones Unearthed:Development of an Online Therapeuticserious Game for Children with Attention Deficit-hyperactivity DisorderPublication . Rijo, R.; Costa, P.; Bastos, D.; Bastos, D.; Matos, P.; Silva, A.; Ferrinho, J.; Almeida, N.; Oliveira, A.; Xavier, S.; Santos, S.; Oliveira, C.; Brites, S.; Martins, V.; Pereira, A.; Fernandes, S.Attention deficit-Hyperactivity Disorder is a disease that affects 3 to 5 percent of children globally. The treatment roots on medication and behavioral exercises. There are unwanted, documented, side effects of the medication, and the behavioral exercises are very demanding for children. In this context the goal of the present research was the development of a serious game for children with 6-8 years old with behavioral exercises as the basis for the action of the game, using a ludic approach. This ludic approach intends to increase the motivation for the game. The present work is part of the research project Therapy4All. The objective of the project is not to replace the traditional form of treatment, but to complement it by allowing a physician to maintain her/his patients under supervision between their regular consultations. The goalis the development of research on serious games to provide patients a better control of their symptoms more than with just traditional therapy. Our first results, with a very small sample, show encouraging improvements in the children's competencies.
- Non-Newtonian Blood Flow in Portal Vein with Thrombosis: A Study by Computational Fluid DynamicsPublication . Soares, A. A.; Gonzaga, S.; Silva, José Silvestre; Marinho, D.; Silva, A.; Rouboa, AbelWe investigate the effects on non‐Newtonian blood flow model on the wall shear stress (wss), velocity and viscosity distributions. The 3D Navier‐Stokes equations coupled with viscosity models describing the steady flow in Portal Vein have been solved numerically. Three blood viscosity models (Newtonian, Power‐law and Carreau) are used in numerical simulations. The results highlight the influence of these models on the blood flow and show that the viscosity model of blood may have significant impact on the numerical results especially in the region of the thrombosis.
- A Pilot-Data Based Channel Estimation Method for OFDM Relay-Assisted SystemsPublication . Neves, D.; Ribeiro, C.; Silva, A.; Gameiro, A.In this work we propose and evaluate a pilot and data-based channel estimation scheme for SFBC OFDM-based cooperative scenario. We consider that both the base station and the relay node are equipped with double antenna arrays whereas the user terminal is a single antenna device. The relay protocol considered is equalise-andforward. In this paper we propose a channel estimation method that iteratively uses the information carried by the pilots and data to improve the estimate of the equivalent channels for the path Base Station – Relay Node – User Terminal. The MMSE criterion is used in the design of the estimator for both the pilot-based and data-aided iterations. The proposed method is evaluated in terms of the channel estimation MSE and the results show that the proposed scheme allows, with a single data iteration, a reduction of the number of pilots by a factor of approximately two when compared with non-data-aided schemes.
- Qualitative analysis of the limestone waste potential from the Serra de Aire e Candeeiros quarriesPublication . Monteiro, S. M. C. S.; Jorge, Muanassa; Oliveira, N. S.; Alves, M.L.; Veiga, A.; Silva, A.The mountains of Aires and Candeeiros are part of the Maciço Calcário Estremenho where the landscape is predominantly made up of limestone. The limestone explored in the region has been the driver of social and cultural development, contributing significantly to the local economy. This emerging concern has motivated public and private organisations to develop solutions to improve the sector's sustainability. The present work aims to evaluate the limestone waste potential to produce precipitated (PCC) and ground (GCC) calcium carbonate in the region by surveying the local extraction industries that fulfil the defined minimum requirements to produce high quality PCC and GCC. The results allowed to stablish an estimate of the amount of waste resulting from the extraction process. The conversion of these wastes into PCC or GCC constitutes a possibility of recovery into by-products, allowing use in noble and profitable applications and contributing to the circular economy and the sustainability of the sector.
- Sustainability study of limestone quarry waste into value-added products: PCC and GCCPublication . Monteiro, S. M. C. S.; Jorge, Muanassa; Heleno, M. L.; Oliveira, N. S.; Alves, M. L.; Veiga, A.; Silva, A.Calcium carbonate can be obtained naturally from limestone, chalk, marble, and other sedimentary rock forms. Ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC) are two materials that can be produced from natural calcium carbonate. The future of GCC and PCC is promising since they are linked to industries with high demand, such as packaging, building & construction, transportation, and industrial applications, with an expected compound annual growth rate higher than 4% until 2027. This research focuses on the production of GCC and PCC through a comparative analysis that identifies the macro conditions that become advantageous to produce and commercialising PCC in a quarry context. This allows a valorisation of the limestone waste resulting from the extraction operations, converting it into by-products of the process. Not all existing limestone quarries in the Serra de Aire e Candeeiros region are suitable sources of raw material to produce PCC. The five extraction poles were identified with the potential for extracting suitable raw materials, associated with several companies dedicated to the extraction operation in these quarries.
- The Interaction Between Intra-Cyclic Variation of the Velocity and Mean Swimming Velocity in Young Competitive SwimmersPublication . Barbosa, T.; Morouço, Pedro G.; Jesus, S.; Feitosa, W.; Costa, M.; Marinho, D.; Silva, A.; Garrido, N.The aim of this study was to assess the relationship between the intra-cyclic variation of the horizontal velocity (dv) and the velocity of the 4 competitive swimming techniques in young swimmers. 45 young swimmers performed a set of maximal 4 × 25 m (freestyle, backstroke, breaststroke and butterfl y stroke) swims with in water start. A speed-meter cable was attached to the swimmer’s hip. The dv and the swimming velocity were analyzed. Within-subject tests presented signifi cant variations in the dv based on the swimming technique. Post-hoc test revealed signifi cant diff erences across all pairwised swimming techniques (P < 0.001), except for the comparison between freestyle and backstroke (P = 0.98). The dv was higher in the breaststroke, followed by the butterfl y, the backstroke and the freestyle. The quadratic models had the best goodness-of-fi t and the lower error of estimation for the relationship between the dv and the swimming velocity in all swimming techniques (0.24 ≤ R 2 ≤ 0.51). As a conclusion, there is a non-linear relationship where the increase of swimming velocity leads to a decrease of dv in young competitive swimmers.
- A Time Domain Channel Estimation Scheme for Equalize-and-Forward Relay-Assisted SystemsPublication . Neves, D.; Ribeiro, C.; Silva, A.; Gameiro, A.In this paper we propose a scheme with a dedicated relay node for an OFDM-based system. We consider an antenna array at the base station and a single antenna at both the user terminal and the relay node. The relay-assisted protocol considered is equalize-and-forward. The proposed scheme requires the computation of parameters which depend on unknown variables at the destination and we show that under some assumptions the scheme is suitable to provide all those requirements. Also, we show that since the pilots at the relay node are properly designed the TD-MMSE estimator can still provide the required channel estimate. The system performance is evaluated by considering a typical pedestrian scenario based on WiMAX specification. The results show that the degradation in the estimator performance is negligible.