Browsing by Author "Mendes, Luís"
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- Automated design of microwave discrete tuning differential capacitance circuits in Si‐integrated technologiesPublication . Mendes, Luís; Pires, E. J. Solteiro; Vaz, João C.; Rosário, Maria J.; Oliveira, P. B. de Moura; Machado, J. A. TenreiroA genetic algorithm used to design radio-frequency binary-weighted differential switched capacitor arrays (RFDSCAs) is presented in this article. The algorithm provides a set of circuits all having the same maximum performance. This article also describes the design, implementation, and measurements results of a 0.25 μm BiCMOS 3-bit RFDSCA. The experimental results show that the circuit presents the expected performance up to 40 GHz. The similarity between the evolutionary solutions, circuit simulations, and measured results indicates that the genetic synthesis method is a very useful tool for designing optimum performance RFDSCAs.
- Design of Radio-Frequency Integrated CMOS Discrete Tuning Varactors Using the Particle Swarm Optimization AlgorithmPublication . Pires, E. J. Solteiro; Mendes, Luís; Oliveira, P. B. de Moura; Machado, J. A. Tenreiro; Vaz, João C.; Rosário, Maria J.This paper presents an automated design procedure of radio- frequency integrated CMOS discrete tuning varactors (RFDTVs). This new method use the maximin and the particle swarm optimization (PSO) algorithms to promote well distributed non-dominated fronts in the parameters space when a single-objective function is optimized. The fitness function used in the search tool is proportional to the RFDTV quality factor. The outcome of the automated design method comprises a set of RFDTV circuits, all having the same maximum performance. Each solution, which corresponds to one RFDTV circuit, is defined by the number of cells and by the circuit components values. This approach allows the designer to choose among several possible circuits the one that is easier to implement in a given CMOS process. To validate the effectiveness of the synthesis procedure proposed in this paper (PSO-method) comparisons with a design method based on genetic algorithms (GA-method) are presented. A 0.18 μm CMOS radio-frequency binary-weighted differential switched capacitor array (RFDSCA) was designed and implemented (the RFDSCA is one of the possible topologies of the RFDTVs). The results show that both design methods are in very good agreement. However, the PSO technique outperforms the GA-method in the design procedure run time taken to accomplish the same performance results.
- Low-Cost Smart Surveillance System for Smart CitiesPublication . Brás Pereira, Rúben Filipe; Correia, Diogo; Mendes, Luís; Rabadão, Carlos; Barroso, João; Pereira, AntónioThe safety of people and spaces is of paramount importance for societies. With time, the implementation of safety measures is rapidly changing from a need to a priority. Video surveillance systems play a key role in the surveillance of crucial and critical areas as these systems help the authorities keep places safer. With the rapid growth of technology and the implementation of the smart city concept, it is becoming possible to develop and deploy wide area surveillance systems. The ease with which these systems can be installed in private and public spaces (e.g., homes, streets and parks) allow for the creation of ubiquitous monitored environments. Rapid intervention responses to any abnormal situation or the use of recorded video as evidence are some advantages of the use of this type of surveillance systems. Although ubiquitous video surveillance systems are relevant for present modern societies, their cost is still high. To solve or, at least to mitigate this problem, a low-cost smart surveillance system was developed, which is presented and described in this paper. The developed surveillance system, based on available low-cost technology, can help keep critical spaces under surveillance 24/7. The proposed solution was found to have a minimal cost, a low bandwidth, and to be scalable and adaptable to every client’s needs. Thus, the solution can be used by anybody (private and public) and applied in different contexts (e.g., residential, industrial). The system can provide still images, captured from surveillance video cameras, real time video and real time video processing, which can be used for motion detection. When this happens, the user is warned via an e-mail containing the identification of the respective surveillance camera. Only the relevant video events are sent, recorded and maintained in the cloud platform system, consequently reducing the amount of storage space required to maintain all the historical video events. The results of the tests carried out show that it is possible to stream a video from the surveillance cameras with an insignificant delay and that motion detection can be attained through real time video processing. The system presented potentiates a low-cost solution for a smart city in the surveillance field.
- Maximin spreading algorithmPublication . Pires, E. J. Solteiro; Mendes, Luís; Lopes, António M.; Oliveira, P. B. de Moura; Machado, J. A. Tenreiro; Vaz, João; Rosário, Maria J.This paper presents a genetic algorithm to optimize uni-objective problems with an infinite number of optimal solutions. The algorithm uses the maximin concept and e-dominance to promote diversity over the admissible space. The proposed algorithm is tested with two well-known functions. The practical results of the algorithm are in good agreement with the optimal solutions of these functions. Moreover, the proposed optimization method is also applied in two practical real-world engineering optimization problems, namely, in radio frequency circuit design and in kinematic optimization of a parallel robot. In all the cases, the algorithm draws a set of optimal solutions. This means that each problem can be solved in several different ways, all with the same maximum performance.
- Particle swarm optimization with fractional-order velocityPublication . Pires, E. J. Solteiro; Machado, J. A. Tenreiro; Oliveira, P. B. de Moura; Cunha, J. Boaventura; Mendes, LuísThis paper proposes a novel method for controlling the convergence rate of a particle swarm optimization algorithm using fractional calculus (FC) concepts. The optimization is tested for several wellknown functions and the relationship between the fractional order velocity and the convergence of the algorithm is observed. The FC demonstrates a potential for interpreting evolution of the algorithm and to control its convergence.
- (Re)educação funcional respiratória pré-operatória em pessoas com patologia colorretal: estudo observacionalPublication . Correia, Nuno; Mendes, Luís; Areias, Sandra; Pereira, Maria Queiroz Vaz; Bernardes, RafaelEnquadramento: a cirurgia colorretal está associada ao risco de morbilidade e mortalidade, relacionando-se com o surgimento de complicações. Os exercícios de reeducação funcional respiratória (RFR) realizados por enfermeiros de reabilitação, tornam-se fundamentais para prevenir/minimizar complicações pós-operatórias. Objetivos: avaliar o impacto da RFR em pessoas com indicação para cirurgia colorretal, nos valores da capacidade vital (CV) e saturação periférica de O2 (SpO2) e descrever as capacidades adquiridas após a aplicação de um programa de RFR pré-operatório. Metodologia: estudo observacional descritivo, com amostra de conveniência de pessoas com patologia colorretal submetidas a um programa de RFR pré-operatória num Centro Hospitalar e Universitário da região centro de Portugal. Resultados: a amostra foi de 78 pessoas. Avaliados parâmetros respiratórios como a CV e SpO2, assim como a avaliação das capacidades adquiridas. A média de sessões de RFR por utente foi de 3,97, obtendo-se uma variação positiva da SpO2 em 46 e variação positiva da CV em 41. À exceção de 3 pessoas, a maioria adquiriu capacidades preconizadas a diferentes níveis. Conclusão: são visíveis ganhos obtidos na preparação pré-operatória das pessoas na função respiratória e nas capacidades para lidarem com a dor. Estes resultados são importantes para a prevenção de complicações respiratórias no período pós-operatório.
- Security Monitoring in a Low Cost Smart Home for the ElderlyPublication . Ferreira, Gabriel; Penicheiro, Paulo; Bernardo, Ruben; Neves, Álvaro; Mendes, Luís; Barroso, João; Pereira, AntónioThe general increase in life expectancy and the consequent ageing of the general population impose major challenges to modern societies. Most elderly people experience the typical problems related to old age, such as chronic health problems, as well as sensory and cognitive impairments. In addition, in today’s modern societies, where families have less and less time to look after their older relatives, the isolation of the elderly is a real concern and a highly recurrent problem, which is enhanced when they live alone. To solve, or at least minimize, these problems, a smart home monitoring system was developed, as presented and described in this paper. This solution is implemented based on a sensory network which detects anomalous behaviors, immediately triggering a warning to the caregiver or family. A strong concern when developing a project of this kind is the physical security of the elderly. Houses tend to have hazardous objects and characteristics that may inflict serious injuries to their occupants or, in extrema, even death. As time goes by, the elderly start losing muscle mass and osteoporosis may appear, as well as vision and hearing impairments, which increase the likelihood of falling. Several other serious accidents may also occur, such as gas leaks, floods and fire outbreaks. Therefore, this population would strongly benefit from a solution which helps predict and even prevent accidents before they happen.