Pettenghi H.,Institute Engineering Of Sistemas E Computadores Investigac Ao E Desenvolvimento |
Avedillo M.J.,CSIC - National Center of Microelectronics |
Avedillo M.J.,University of Seville |
Quintana J.M.,CSIC - National Center of Microelectronics |
Quintana J.M.,University of Seville
IEEE Transactions on Nanotechnology | Year: 2011
Many logic circuit applications of resonant tunneling diodes are based on the monostablebistable logic element (MOBILE). Threshold logic is a computational model widely used in the design of MOBILE circuits, i.e., these circuits are built from threshold gates (TGs). This paper describes the design of full adders (FAs), using TG-based circuit topologies. Both the selection of different MOBILE TG networks and the use of gates that can be considered extensions of the MOBILE TG are addressed. The FAs are applied to the design of nanopipelined carry propagations adders, which are evaluated and compared to a previously reported one, showing advantages in terms of speed, power, and power-delay product. © 2010 IEEE.
Rosado L.S.,Telecommunications Institute of Portugal |
Rosado L.S.,Institute Engineering Of Sistemas E Computadores Investigac Ao E Desenvolvimento |
Rosado L.S.,University of Lisbon |
Ramos P.M.,Telecommunications Institute of Portugal |
And 3 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2014
The design, implementation, and evaluation of a real-time digital signal processing architecture to generate and process multifrequency signals for eddy currents testing is described in this paper. This architecture is implemented on a dedicated instrument whose processing core is a field-programmable gate array. Stimulus generation is achieved using direct digital synthesis with some important improvements to reduce spurious frequency components. An in-phase and in-quadrature demodulation scheme is implemented to estimate the real and imaginary parts of the probe output signal. A cascaded integrator comb decimator is used to lower the sampling frequency and then allow narrowband filtering with low resources. The proposed architecture is able to generate and process the stimulus and input data at 125 MSamples/s and to estimate the input data components at 1.25 MSamples/s rate for eddy-currents with multiple simultaneous testing frequencies between 2.5 kHz and 10 MHz. Experimental validation is performed using a set of synthetic defects and two stimulus with different spectral composition. © 1963-2012 IEEE.
Pellegrini T.,Institute Engineering Of Sistemas E Computadores Investigac Ao E Desenvolvimento |
Correia R.,Institute Engineering Of Sistemas E Computadores Investigac Ao E Desenvolvimento |
Correia R.,University of Lisbon |
Correia R.,Carnegie Mellon University |
And 7 more authors.
Computer Speech and Language | Year: 2013
Spoken European Portuguese (EP) is known to be difficult to understand for L2 learners, due to phenomena such as strong vowel reduction. In this paper, we present a method to automatically generate exercises aimed at improving listening comprehension skills in EP. Learners identify the words pronounced in real speech utterances. The exercises introduce two innovative aspects: using broadcast news videos for curriculum and automatically generating exercises with material updated on a daily basis. The videos are automatically transcribed by a speech recognition engine. A filtering chain, used to select appropriate sentences, was validated by a first survey comprised of both manually and automatically selected sentences. Both sets were assigned good to very good subjective quality scores. A second survey concerned the features of the exercise interface. Subjects with varying self-reported exposure to Portuguese as a second language tested several interfaces and functionalities and highlighted their preferred features. The results confirmed that the largest difficulty was the fast speech rate. All participants valued slowed-down audio and video documents, though this feature was more often used by the lowest proficiency subjects. The exercises were integrated into aWeb platform where they are automatically updated daily. Though further evaluation is needed to find whether the platform affords skill acquisition, it is expected to be particularly valuable for distance learners who need opportunities to access authentic audio documents in EP. © 2013 Elsevier Ltd. All rights reserved.
Santos Ribeiro A.,Imperial College London |
Santos Ribeiro A.,University of Lisbon |
Salvado D.,University of Lisbon |
Salvado D.,University College London |
And 3 more authors.
PhyCS 2014 - Proceedings of the International Conference on Physiological Computing Systems | Year: 2014
Advances in low-voltage integrated circuits have enabled the development of low-cost, low-power, and down-sized portable instrumentation. In the biomedical field, mobile sensing platforms provide an efficient way to monitor the physical condition of a subject. Moreover, these platforms provide an input for human-computer interaction. We developed a low-cost platform that can be adapted to acquire different electrophysiological signals, and interface with portable devices for storing, processing, and displaying of data. The developed platform was used to acquire electrocardiography (ECG), electromyography (EMG), electroencephalography (EEG), and electrooculography (EOG) signals, and the results were compared with signals obtained with the benchmark BIOPAC system. For the same frequency bands, results show that our portable platform was able to acquire electrophysiological signals with similar accuracy as those acquired with the BIOPAC system. Due to its simplicity, low-cost design, and easy implementation, the developed platform suits researchers, developers, and hobbyists, in the fields of physiological monitoring, human-computer interaction, and perceptual computing. Copyright © 2014 SCITEPRESS - Science and Technology Publications. All rights reserved.
Tavares G.N.,University of Lisbon |
Tavares G.N.,Institute Engineering Of Sistemas E Computadores Investigac Ao E Desenvolvimento |
Petrolino A.,INESC ID
IEEE Transactions on Communications | Year: 2011
In this paper the problem of generating a stationary band-limited Gaussian random vector with arbitrary complex autocorrelation by the inverse discrete Fourier transform (IDTF) algorithm is considered. Instead of using the classical frequency mask (FM), determined from samples of the (band-limited) target power spectral density (PSD) of the process, a new FM is obtained by matching the autocorrelation obtained with the IDFT algorithm to a desired arbitrary autocorrelation. Example results presented show that the new FM is able to significantly increase the autocorrelation accuracy of the generated process at no additional online computational cost. © 2011 IEEE.