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- Monitorização para prevenção das úlceras por pressãoPublication . Azevedo, J. A. R.; Santos, C. L. A.; Santos, M. L. V. A.; Jardim, M. H. A. G.A permanência de pessoas em camas e cadeiras por períodos de 2 horas ou mais pode levar ao aparecimento de úlceras por pressão (UPP) nas zonas de contacto das proeminências ósseas. Este problema apresenta-se hoje com elevada magnitude afetando drasticamente a qualidade de vida dos indivíduos e das famílias e consequentemente da sociedade. Custos notáveis ao nível pessoal, familiar, social e económico solicitam respostas efetivas ao nível da sua prevenção. A elevada prevalência de UPP em pessoas com necessidade de cuidados de saúde, quer em hospitais, lares ou domicílios1 na Macaronésia suscitou o interesse de um grupo de investigadores para a sua prevenção. O trabalho aqui apresentado foi desenvolvido pelo projeto de Investigação Científica em Enfermagem2 no âmbito do programa MAC 2007-2013 (ICE2 MAC/1/A029). Trata-se de uma continuidade do estudo sobre sistemas de medição de pressão e de temperatura efetuado na Universidade da Madeira cujo objetivo foi criar um sistema automático de deteção precoce da lesão tecidular2. Ele expressa o esforço interdisciplinar de investigadores da área da engenharia e da enfermagem em prol de uma solução efetiva para apoiar os cuidadores a prevenir as UPP. O artigo começa por abordar a relação que a pressão e a temperatura têm no aparecimento da lesão tecidular, sugerindo-as como indicadores preditivos da mesma. Na segunda parte advoga a monitorização da pressão e da temperatura como mais-valias para uma eficaz prevenção das UPP e apresenta os resultados de um estudo com um sistema de monitorização de pressão e temperatura. Apresenta o protótipo em desenvolvimento, o sistema de monitorização para prevenção das UPP, constituído por matrizes de sensores, circuitos de aquisição de dados, sistema de transmissão sem fios e um software de visualização dos dados. Enfatiza-se como dado inovador o facto de cada matriz de sensores, aplicada numa superfície de contacto, cadeira ou cama, estar associada a um computador e a um nó sensor sem fios, permitindo que a informação relativa a cada superfície seja visualizada local e remotamente, constituindo-se uma ferramenta útil para o despiste precoce da lesão tecidular que origina uma úlcera por pressão.
- A more efficient technique to power home monitoring systems using controlled battery chargingPublication . Azevedo, Joaquim Amândio; Santos, Filipe EdgarHome energy monitoring has recently become a very important issue and a means to reduce energy consumption in the residential sector. Sensors and control systems are deployed at various locations in a house and an intelligent system is used to efficiently manage the consumed energy. Low power communication systems are used to provide low power consumption from a smart meter. Several of these systems are battery operated. Other systems use AC/DC adapters to supply power to sensors and communication systems. However, even using low-power technology, such as ZigBee, the power consumption of a router can be high because it must always be powered on. In this work, to evaluate power consumption, a system for monitoring energy usage and indoor air quality was developed. A technique is proposed to efficiently supply power to the components of the system. All sensor nodes are battery operated, and relays are used to control the battery charging process. In addition, an energy harvesting system based on solar energy was developed to power the proposed system.
- Energy harvesting from hydroelectric systems for remote sensorsPublication . Azevedo, Joaquim Amândio Rodrigues; Lopes, JorgeHydroelectric systems are well-known for large scale power generation. However, there are virtually no studies on energy harvesting with these systems to produce tens or hundreds of milliwatts. The goal of this work was to study which design parameters from large-scale systems can be applied to small-scale systems. Two types of hydro turbines were evaluated. The first one was a Pelton turbine which is suitable for high heads and low flow rates. The second one was a propeller turbine used for low heads and high flow rates. Several turbine geometries and nozzle diameters were tested for the Pelton system. For the propeller, a three-bladed turbine was tested for different heads and draft tubes. The mechanical power provided by these turbines was measured to evaluate the range of efficiencies of these systems. A small three-phase generator was developed for coupling with the turbines in order to evaluate the generated electric power. Selected turbines were used to test battery charging with hydroelectric systems and a comparison between several efficiencies of the systems was made. Keywords
- Adapted raised cosine window function for array factor control with dynamic range ratio limitationPublication . Santos, Filipe E. S.; Azevedo, Joaquim A. R.The use of window functions to improve the side lobe level of antenna arrays is hindered by high value of excitation currents dynamic range ratio. This paper proposes a fast and iterative window function generation strategy aimed at achieving improved side lobe level starting from a preset current dynamic range ratio. Based on this strategy a new window function is developed for standard set of conditions.
- Performance evaluation of directional antennas in ZigBee networks under NLOS propagation conditionsPublication . Azevedo, Joaquim Amândio; Santos, FilipeMany authors suggest directional antennas to enhance the transmission performance of ZigBee networks. For line-of-sight propagation, directional antennas can extend the transmission range or reduce the transmit power. Directional antennas may also reduce interference between networks operating in the same frequency channel. However, these antennas may not perform similarly under non-line-of-sight propagation conditions. This work presents a study with ZigBee modules comparing the performance of a directional antenna with an omnidirectional one. The measurements were conducted on a university campus for different propagation outdoor environ ments. A deconvolution technique was applied to estimate the received signal as a function of the azimuth angle. The results demonstrated that the received power followed the gain difference between antennas only for paths with low attenuation. Considering the same Effective Isotropic Radiated Power (EIRP), the system with directional antennas started to lose packets at the same distance as the omnidirectional antennas. The directional antenna did not allow the increase in the link range compared to the omnidirectional antenna. The power consumption was also measured for different transmit power levels of the ZigBee radio. The study showed that the control circuits of directional antennas typically consume more power than omnidirectional antennas operating at a higher transmit power level.
- Noncontact Automatic Water-Level Assessment and Prediction in an Urban Water Stream Channel of a Volcanic Island Using Deep LearningPublication . Mendonça, Fabio; Mostafa, Sheikh Shanawaz; Dias, Fernando Morgado; Azevedo, Joaquim Amândio; Ravelo-García, Antonio G.; Navarro-Mesa, Juan L.Traditional methods for water-level measurement usually employ permanent structures, such as a scale built into the water system, which is costly and laborious and can wash away with water. This research proposes a low-cost, automatic water-level estimator that can appraise the level without disturbing water flow or affecting the environment. The estimator was developed for urban areas of a volcanic island water channel, using machine learning to evaluate images captured by a low-cost remote monitoring system. For this purpose, images from over one year were collected. For better performance, captured images were processed by converting them to a proposed color space, named HLE, composed of hue, lightness, and edge. Multiple residual neural network architectures were examined. The best-performing model was ResNeXt, which achieved a mean absolute error of 1.14 cm using squeeze and excitation and data augmentation. An explainability analysis was carried out for transparency and a visual explanation. In addition, models were developed to predict water levels. Three models successfully forecasted the subsequent water levels for 10, 60, and 120 min, with mean absolute errors of 1.76 cm, 2.09 cm, and 2.34 cm, respectively. The models could follow slow and fast transitions, leading to a potential flooding risk-assessment mechanism.
- Aplicação do processamento de sinal à análise e síntese de agrupamentosPublication . Azevedo, Joaquim Amândio Rodrigues; Casimiro, António Manuel Esteves Santos
- A model to estimate the path loss in areas with foliage of treesPublication . Azevedo, Joaquim A.; Santos, Filipe E.This paper presents an empirical model to predict attenuation in forest environments considering parameters related to vegetation. Typically, environmental parameters are only included in theoretical models, but they are more difficult to apply. The developed model uses tree density, average tree canopy diameter and foliage density as input parameters. The foliage density is very difficult to determine since it depends on the characteristics of trees. A simple metric of this parameter was obtained by measuring the background light silhouetted by the canopy. The model was developed with measurements obtained in different forest environments for two frequencies within the UHF band (Ultra High Frequency). A procedure was also applied to extend the operating frequency range of the model.
- Non-uniform sampling and polynomial interpolation for array synthesisPublication . Azevedo, J. A. R.; Casimiro, A. M. E. S.
- Antenna pattern control of planar arrays for long distance communicationsPublication . Azevedo, J. A. R.As an alternative to standard antennas and due to the advent of low-cost digital processors and materials, adaptive antenna arrays are increasingly considered for applications in long distance communications. The pattern beam control potentialities provide the performance improvement of the communication systems. In this context, this work presents a technique that permits to synthesize the antenna pattern of a planar array. Considering that the relationship between the array factor and the array excitations for the far field region is a Fourier transform in the appropriate variables, the non-uniform sampling procedure is extended for planar arrays. These arrays permit a further control of the antenna pattern since two dimensions of space are used. The technique considers a number of array factor points equal to the array size, which is used to impose appropriated values in the antenna pattern. The produced array factor passes through those points with the desired values, which allows the synthesis of antenna patterns with appropriated characteristics. The theory is presented in order to develop the necessary direct expressions to calculate the array excitation. The array factor can be obtained using the inverse Fourier transform. As application examples, with this technique it is possible to define the level of each sidelobe of the antenna pattern, to control the main beam and to impose nulls in prescribed directions of the pattern.
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