Browsing by Author "Martins, J."
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- Colour filtering in a-SiC : H based p-i-n-p-i-n cells: A trade-off between bias polarity and absorption regionsPublication . Vieira, Manuela; Fantoni, Alessandro; Louro, Paula; Fernandes, Miguel; Martins, J.; Schwarz, R.; Lavareda, G.; Carvalho, C. N.A large area colour imager optically addressed is presented. The colour imager consists of a thin wide band gap p-i-n a-SiC:H filtering element deposited on the top of a thick large area a-SiC:H(-p)/a-Si:H(-i)/a-SiC:H(-n) image sensor, which reveals itself an intrinsic colour filter. In order to tune the external applied voltage for full colour discrimination the photocurrent generated by a modulated red light is measured under different optical and electrical bias. Results reveal that the integrated device behaves itself as an imager and a filter giving information not only on the position where the optical image is absorbed but also on it wavelength and intensity. The amplitude and sign of the image signals are electrically tuneable. In a wide range of incident fluxes and under reverse bias, the red and blue image signals are opposite in sign and the green signal is suppressed allowing blue and red colour recognition. The green information is obtained under forward bias, where the blue signal goes down to zero and the red and green remain constant. Combining the information obtained at this two applied voltages a RGB colour image picture can be acquired without the need of the usual colour filters or pixel architecture. A numerical simulation supports the colour filter analysis.
- Consumer energy management system with integration of smart metersPublication . Pereira, Rita Marcos Fontes Murta; Figueiredo, J.; Melício, Rui; Mendes, Victor; Martins, J.; Quadrado, Jose CarlosThis paper develops an energy management system with integration of smart meters for electricity consumers in a smart grid context. The integration of two types of smart meters (SM) are developed: (i) consumer owned SM and (ii) distributor owned SM. The consumer owned SM runs over a wireless platform - ZigBee protocol and the distributor owned SM uses the wired environment - ModBus protocol. The SM are connected to a SCADA system (Supervisory Control And Data Acquisition) that supervises a network of Programmable Logic Controllers (PLC). The SCADA system/PLC network integrates different types of information coming from several technologies present in modern buildings. The developed control strategy implements a hierarchical cascade controller where inner loops are performed by local PLCs, and the outer loop is managed by a centralized SCADA system, which interacts with the entire local PLC network. In order to implement advanced controllers, a communication channel was developed to allow the communication between the SCADA system and the MATLAB software. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
- Fuzzy clustering applied to a demand response model in a smart grid contingency scenarioPublication . Pereira, Rita; Melício, Rui; Mendes, Victor; Figueiredo, J.; Martins, J.; Fagundes, A.; Quadrado, Jose CarlosThis paper focus on a demand response model analysis in a smart grid context considering a contingency scenario. A fuzzy clustering technique is applied on the developed demand response model and an analysis is performed for the contingency scenario. Model considerations and architecture are described. The demand response developed model aims to support consumers decisions regarding their consumption needs and possible economic benefits.
- Fuzzy clustering applied to a demand response model in a smatr grid contingency scenarioPublication . Pereira, Rita; Melício, Rui; Mendes, Victor; Figueiredo, J.; Martins, J.; Fagundes, A.; Quadrado, Jose CarlosThis paper focus on a demand response model analysis in a smart grid context considering a contingency scenario. A fuzzy clustering technique is applied on the developed demand response model and an analysis is performed for the contingency scenario. Model considerations and architecture are described. The demand response developed model aims to support consumers decisions regarding their consumption needs and possible economic benefits.
- Procedures for measuring the near point of convergence and the point of asthenopia in individuals with and without postural deficiency syndromePublication . Dolan, Ana; Poças, Ilda Maria; Silva, O. A.; Silva, Carina; Barros, A. S.; Firmino, A.; Martins, J.; Vasco, H.; Mendanha, LuísPurpose: Postural Deficiency Syndrome is a multifactorial proprioceptive dysfunction with varied signs and symptoms, including convergence insufficiency and asthenopia which impact visual performance. The near point of convergence measurement is used to diagnose and clinically explore convergence insufficiency. Test speed and stimulus size influence values obtained. The definition of the most effective method to measure the near point of convergence and the point of asthenopia will allow early detection of alterations. This study aims to investigate the accuracy of measurements and variations in values obtained using different methods for the near convergence point and the point of asthenopia measurements in cases of Postural Deficiency Syndrome. Methods: The sample contained 39 patients, 27 with and 12 without Postural Deficiency Syndrome, measuring the near point of convergence and point of asthenopia with two stimuli (standard RAF rule and modified RAF rule) at two speeds (1cm/s and 3cm/s). Results: Neither method of measuring the near point of convergence had statistically significant values. The RAF near point rule at 1cm/s is more sensitive for alterations in the point of asthenopia (AUC 0.761 ± 0.084 standard error, p = 0.010). At 1cm/s, higher values for near point of convergence and point of asthenopia were measured, chiefly in the Postural Deficiency Syndrome group. Conclusion: Methods used to measure the parameters studied influenced the final values. No statistically significant values were obtained in the measurement of the near convergence point. To measure the point of asthenopia, the standard RAF rule at 1cm/s has the highest accuracy.
- Sensor element for a metal-insulator-semiconductor camera system (MISCam)Publication . Schwarz, R.; Fernandes, Miguel; Martins, J.; Fantoni, Alessandro; Vieira, Manuela; Sanguino, P.; Carvalho, C. N.; Muschik, T.We discuss the operation of a new type of optical sensor (MISCam) based on a metal-insulator-semiconductor (MIS) structure. The operation principle relies on light-induced changes of the band bending and barrier height at the interface between semiconductor and insulator. An image is obtained from the quenching of the ac signal in analogy to the principle of the laser-scanned photodiode (LSP). Lateral resolution depends on the semiconductor material chosen. We have characterised the MIS structures by C-V, I-V, and spectral response measurements testing different types of insulators like a-Si3N4, SiO2, and AlN. The presence of slow interface charges allows for image memory. Colour sensors can be realised by controlling sign and magnitude of the electric fields in the base and the interface region.