ESTG - Comunicações em conferências e congressos internacionais
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- A 1.2V 900nW conductance converterPublication . Miranda, Nuno; Morais, RaulThis article describes a new electrical conductance converter method suitable for very low power applications, where energy constraints prevails over speed and measurement accuracy. Method idea gather voltage time integration and shopper stabilization techniques to process noisy low amplitude signals and to overcome severe limitations of weak inversion channel CMOS circuitry. Main features and tradeoffs are exploited. A 1.2V ASIC implementation on standard 0.35μm CMOS schematics is also presented. Post-layout simulations shows a total power consumption lower than 900nW including current source excitation inherent to the conductance measurement. Such low power consumption allows the measurement of several physical parameters on self-powered wireless networks.
- 3D Indoor Radio Coverage for 5G Planning: a Framework of Combining BIM with Ray-tracingPublication . Louro, João; Fernandes, Telmo Rui; Rodrigues, Hugo; Caldeirinha, Rafael F. S.This paper presents a framework to predict indoor radio wave coverage in buildings. Such method includes the capability to import BIM (Building Information Modelling) files that contain structured physical geometry and dimension data, including the material types that are of uttermost importance in evaluating their dielectric properties. Appropriated extraction of physical and dielectric attributes of the building elements was used as input to a 3D radio wave propagation ray-tracing developed in MatLab that allows the prediction of the received radio signal level at any location within the computational volume. Results are presented for line-of-sight contributions and first and second order reflections. Despite the generic nature of the proposed framework, prediction results are presented at 3.6 GHz, envisaging emerging 5G indoor radio coverage.
- 3D video shot boundary detection based on clustering of depth-temporal featuresPublication . Ferreira, Lino; Assunção, Pedro; Cruz, Luis A. da SilvaThis paper proposes an algorithm for automatic detection of 3D video shots with different perceptual features. The proposed algorithm is able to identify distinct three-dimensional visual scenes by detecting 3D video shot boundaries based on clustering of depth-temporal features. A combination of texture variation along the temporal dimension and depth variance is used by K-means clustering to find the stereo frames which comprised the 3D scene boundaries. An important characteristic of the proposed algorithm in comparison with others published in the literature for temporal segmentation of classic 2D video is that no thresholds are used in the decision processes neither training data sets. The experimental results show that the proposed method is capable of achieving high recall (e.g., 0.95) and precision rate (e.g., 1.0) in video sequences with both sharp and smooth 3D scene transitions.
- 4D Light Field Disparity Map estimation using Krawtchouk PolynomialsPublication . Lourenco, Rui; Rivero-Castillo, Daniel; Thomaz, Lucas A.; Assuncao, Pedro A. A.; Tavora, Luis M. N.; Faria, Sergio M. M. deThis work presents an improved method to estimate disparity maps obtained from light field cameras using a novel edge detection algorithm based on Krawtchouk polynomials. The proposed method takes advantage of these polynomials to determine gradient information and find the edges based on automatically estimated weak and strong thresholds. The calculated edges in the gray scale epipolar plane image representation of a light field are then used to improve the accuracy of object boundaries in the the disparity map. The proposed method achieves better results when compared to other edge detection algorithms, both in terms of objective and subjective quality, specifically by reducing the mean squared error and the artifacts in the object boundaries. Furthermore, on average, the proposed method outperforms the state-of-the-art depth estimation algorithms, in terms of the objective quality of the final disparity map, namely for the commonly used HCI dataset.
- A European Portuguese Children Speech Database for Computer Aided Speech TherapyPublication . Lopes, Carla, Alexandra Calado Lopes; Veiga, Arlindo; Perdigão, FernandoThis paper introduces a European Portuguese speech database containing spoken material recorded from children. The need for such database arose from the need of train phone models for the development of a computer aided speech therapy system. Articulatory disorders affect a significant number of children in pre-school age. We propose a system intended to assist and reinforce the conventional speech therapy programs. Through the systematic use of games, it learns the phones where the child has more difficulty to pronounce. The child is then taken to train the production of those phones by playing games. Another interest of a children speech database is that accurate children's phone recognition is only possible using training data that reflects the population of users. It is a difficult task due to the high pitch of children's speech
- ACTIVE CFRP-BASED CONFINEMENT STRATEGIES FOR RC COLUMNS WITH RECTANGULAR CROSS SECTIONSPublication . Agante, Marta; Júlio, Eduardo N. B. S.; Barros, Joaquim A. O.; Santos, João M. C.FRP wrapping is a strengthening technique for RC columns mostly used when a significant confinement increase is required. This technique is extremely effective in the case of circular cross-sections, but of marginally effectiveness for rectangular cross-sections columns. The use of post-tensioned CFRP jackets was an attempt to improve the confinement effectiveness for rectangular RC columns, but the level of success has been quite limited. This paper analyzes the viability of using an expansive resin to introduce some level of post-tension in CFRP jacket. In a first step, the optimal percentage of water added to trigger the resin expansion was analyzed. Using the obtained optimal value of water, the influence on the level of jacket post-tension of the width of the gap between the concrete surface and the CFRP jacket was investigated, and its timedependent sensitivity was assessed. Finally, the compression behaviour of specimens confined with this technique was assessed by performing experimental tests. The obtained results revealed that the adopted expansive resin is not an effective technique to assure high levels of post-tension in CFRP jackets for the concrete confinement.
- Ad-hoc changes in IoT-aware business processesPublication . Domingos, Dulce; Martins, Francisco; Martinho, Ricardo; Silva, MárioThe Internet of Things makes it possible to adapt the behaviour of business processes in response to real-time context updates. In addition, physical items can run and validate parts of the business processes and optimise their execution, while reducing message transmissions. State-of-the-art event-driven, service-oriented architecture approaches contribute to enabling inter-organisational collaboration and interoperability of heterogeneous hardware, but their applicability is limited to preplanned, well-structured processes. We take a step forward by supporting ad-hoc changes within business processes, considering changes in the state of the Things; likewise, whenever needed, the software controlling the behaviour of sensors may be dynamically reconfigured as a result of changes in the functional specifications of business processes.
- Adaptive coding tree for complexity control of high efficiency video encodersPublication . Correa, G.; Assunção, P.; Silva Cruz, L. A. da; Agostini, L.The emerging HEVC standard introduces several techniques which increase compression efficiency in comparison to its predecessors. However, such advances are accompanied by increases in computational complexity, limiting the encoder use in computational or power-constrained devices. This paper proposes a novel complexity control method for the future HEVC encoders based on a dynamic adjustment of the newly proposed coding tree structures. The relationship between coding tree depths and the encoding complexity is explored to selectively constrain encoding possibilities in order to not exceed a predefined complexity target. Experimental results show that the encoder computational complexity can be downscaled to 60% with a bit rate increase under 3.5% and a PSNR decrease under 0.1 dB.
- All-digital reconfigurable STDCC radar baseband implementation in FPGAPublication . Duarte, Luís; Ribeiro, Carlos; Alves, Luís N.; Caldeirinha, Rafael F. S.This paper reports the architecture of an all-digital Swept Time-Delay Cross-Correlator (STDCC) baseband. Until recently, the sliding correlator technique has been mainly em-ployed for sounding the radio propagation channel. However, recent benchmarks have shown promising results in target detection context when compared to commercially available solutions. STDCC takes advantage of the sliding correlation properties of Pseudo-Noise (PN) sequences. Therefore, this paper presents the baseband generation for this new radar technique with on-the-fly sequence tuning using a Field-Programmable Gate Array (FPGA). The reconfigurable STDCC radar baseband generates both PN sequences digitally and requires a low-cost ADC to acquire the time dilated result. At the end, the proposed architecture is evaluated regarding resource usage efficiency and then the radar performance will be discussed in terms of the all-digital PN sequence spectrum and the real-time slide correlation. Our analysis confirmed a strong correlation between both sequence length and sampling frequency with radar detectable distance.
- Alternative Zigbee codes derived from orthogonal perfect DFT sequencesPublication . Pereira, João S.; Silva, Henrique J. A. daThe performance of a code-division multiple access (CDMA) system is directly related with the choice of adequate codes. The codes for use in CDMA communication systems should have a perfect aperiodic (or periodic) autocorrelation function and should be orthogonal to each other at all time shifts. A mathematical property that provides a way to find large sets of real perfect DFT (discrete Fourier transform) sequences is presented. These sequences can be transformed into real orthogonal perfect DFT sequences and also into bipolar codes that have better properties than the codes used in the Zigbee communication system. These new bipolar codes are approximately orthogonal and have nearly optimum periodic and aperiodic autocorrelation functions. We also evaluate our bipolar codes with an improved error probability model.