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Publicações

Publicações por CRAS

2023

Modeling and Identification of Li-ion Cells

Autores
dos Santos, PL; Perdicoúlis, TPA; Salgado, PA;

Publicação
IEEE CONTROL SYSTEMS LETTERS

Abstract
To develop a full battery model in view to accurate battery management, Li-ion cell dynamics is modelled by a capacitor in series with a simplified Randles circuit. The open circuit voltage is the voltage at the capacitor terminals, allowing, in this way, for the dependence of the open circuit voltage on the state-of-charge to be embedded in its capacitance. The Randles circuit is recognised as a trusty description of a cell dynamics. It contains a semi-integrator of the current, known as the Warburg impedance, that is a special case of a fractional integrator. To enable the formulation of a time-domain system identification algorithm, the Warburg impedance impulse response was calculated and normalised, in order to derive a finite order state-space approximation, using the Ho-Kalman algorithm. Thus, this Warburg impedance LTI model, with known parameters (normalised impedance) in series with a gain block, is suitable for system identification, since it has only one unknown parameter. A LTI System identification Algorithm was formulated to estimate the model parameters and the initial values of both the open circuit voltage and the states of the normalised Warburg impedance. The performance of the algorithm was very satisfactory on the whole state-of-charge region and when compared with low order Thevenin models. Once it is understood the parameters variability on the state-of-charge, temperature and ageing, we envisage to continue the work using parameter-varying algorithms.

2023

Development of Components for Autonomous Underwater Vehicles by Design for Excellence Concepts

Autores
Pereira, PNAAS; Campilho, RDSG; Pinto, AMG;

Publicação
Techniques and Innovation in Engineering Research Vol. 7

Abstract

2023

The INOVMineral Project's Contribution to Mineral Exploration-A WebGIS Integration and Visualization of Spectral and Geophysical Properties of the Aldeia LCT Pegmatite Spodumene Deposit

Autores
Cardoso Fernandes, J; Santos, D; de Almeida, CR; Vasques, JT; Mendes, A; Ribeiro, R; Azzalini, A; Duarte, L; Moura, R; Lima, A; Teodoro, AC;

Publicação
MINERALS

Abstract
Due to the current energetic transition, new geological exploration technologies are needed to discover mineral deposits containing critical materials such as lithium (Li). The vast majority of European Li deposits are related to Li-Cs-Ta (LCT) pegmatites. A review of the literature indicates that conventional exploration campaigns are dominated by geochemical surveys and related exploration tools. However, other exploration techniques must be evaluated, namely, remote sensing (RS) and geophysics. This work presents the results of the INOVMINERAL4.0 project obtained through alternative approaches to traditional geochemistry that were gathered and integrated into a webGIS application. The specific objectives were to: (i) assess the potential of high-resolution elevation data; (ii) evaluate geophysical methods, particularly radiometry; (iii) establish a methodology for spectral data acquisition and build a spectral library; (iv) compare obtained spectra with Landsat 9 data for pegmatite identification; and (v) implement a user-friendly webGIS platform for data integration and visualization. Radiometric data acquisition using geophysical techniques effectively discriminated pegmatites from host rocks. The developed spectral library provides valuable insights for space-based exploration. Landsat 9 data accurately identified known LCT pegmatite targets compared with Landsat 8. The user-friendly webGIS platform facilitates data integration, visualization, and sharing, supporting potential users in similar exploration approaches.

2023

Drilling Parameters in the Evaluation of Rock Mass Quality

Autores
Pereira, M; Fernandes, I; Moura, R; Plasencia, N;

Publicação
Advances in Science, Technology and Innovation

Abstract

2023

Environmental Impact Assessment of the Subsurface in a Former W-Sn Mine: Integration of Geophysical Methodologies

Autores
De Almeida, H; Marques, MCG; Sant'Ovaia, H; Moura, R; Marques, JE;

Publicação
MINERALS

Abstract
Associated with the exploitation of metallic minerals in Europe during the 20th century, several mining areas were abandoned without adequate environmental intervention. Furthermore, these areas lack studies to characterize the impact of pollution on the hydrogeological system. The area surrounding the tungsten mine of Regoufe, in northern Portugal, is one such area exploited during the Second World War. The accumulation of sulfide-rich tailings may have caused an acid mine drainage (AMD), where the leaching processes caused by seepage water led to soil contamination, evidenced by its acid character and anomalous concentrations of some Potentially Toxic Elements (PTE) reported in previous studies. The present research proposes an innovative approach that seeks the integration of different geophysical techniques to characterize the impact of mining activity on the subsurface. Electrical resistivity (ER) and electromagnetic (EM) were used to measure subsurface electrical properties. In addition, seismic refraction and Multichannel Analysis of Surface Waves (MASW) were performed to characterize the geometry, depth, and geomechanical behavior of the soil and rock bodies. The integration of these techniques allowed the interpretation of hydrogeological sections and a 3D resistivity volume to gain insight into the distribution of potentially contaminating fluids and tailings material present in the mining valley.

2023

Pyroelectrically Polarity Switched Electret for Flexible Invisible Digital Memory and Self-Powered Sensors

Autores
Gonzalez Losada, P; Martins, M; Vinayakumar, KB;

Publicação
IEEE SENSORS JOURNAL

Abstract
Advancement and opportunity in the Internet of Things (IoT) and circular economy are pushing the technologies required to develop eco-friendly memory devices, computing devices, advanced sensors, and actuators. In this manuscript, a thermally cycled lithium niobate pyroelectric crystal is used to store the surface charges in different dielectric samples (Kapton, Parafilm, and Teflon). Charge storing parameters, such as the effect of temperature ramp, the gap between the dielectric-to-pyroelectric, and the effect of charging cycles, were studied to understand the surface charge formation on dielectric samples. Pyroelectrically charged dielectrics showed a surface potential of up to 400 V, with a linear dependence on the thermal gradient of the pyroelectric crystal. The charged surface showed good charge storage uniformity and stability at high temperatures (90 degrees C) and relative humidity (>85%). Using the pyroelectrically charged dielectrics, wearable motion sensors offering output signals in the range of tens of millivolts and a digital flexible invisible memory encoding with polarity switched (positive and negative charges) electrostatic bits are demonstrated.

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