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Publications

Publications by CRAS

2024

PRELIMINARY ESTIMATION OF ELECTRICAL PROPERTIES OF THE LUNAR NEAR SURFACE FROM THE CHINESE YUTU-2 LUNAR PENETRATING RADAR (LPR)

Authors
Moura, R; Lomas, LA; Almeida, F;

Publication
International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM

Abstract
Geophysical studies on the lunar surface have, in the past, used various methods that contribute not only towards the knowledge of the lunar subsurface but also contribute towards the design of future lunar missions, namely those that will, in the near future, take humans to the Moon’s surface. This work analyzes a specific set of ground penetrating radar (GPR) data, collected during the Chang’E-4 mission of the Chinese Space Agency, using theYutu-2 rover within the von Kármán crater, on the far-side of the Moon. From this dataset two electrical parameters were estimated. The approach uses the backscatter of the electromagnetic wavefield in order to obtain estimates of the real component of the complex relative permittivity as well as the electrical resistivity. © 2024 International Multidisciplinary Scientific Geoconference. All rights reserved.

2024

GEOPHYSICAL EXPLORATION IN ARGEMELA DISTRICT, FUNDÃO, PORTUGAL - VLF RESULTS

Authors
Ribeiro R.; Moura R.; Carvalho A.; Lima A.; Gumiaux C.;

Publication
International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM

Abstract
Raw materials are essential for Europe’s industrial base, as they are used to produce vital goods and technologies. The European Comission’s assessment identifies lithium and tin as critical and strategic raw materials due to rising demand. A PhD thesis aims to create a 3D geological model of the Argemela District in Central Portugal to provide vital information about the genesis of the hydrothermal tin and lithium mineralizations founded in the region. The study places emphasis on the very-low-frequency (VLF) electromagnetic method as a tool to provide information about the mineralization, lithologic contacts, and structural features that can be related to the mineralizations. Argemela district has two main areas, the Argemela Tin and Lithium Mine and the Argemela Hill Top. VLF data was collected and analyzed, showing that low resistivity may be associated with mineralization in the Argemela Mine, while high resistivity may be linked to the Argemela microgranite in the Argemela Hill Top. This geophysical method is effective in non-invasively mapping subsurface features, assisting in the development of a comprehensive 3D geological model and enhancing resource evaluation.

2024

The Influence of Hydroxyapatite Crystals on the Viscoelastic Behavior of Poly(vinyl alcohol) Braid Systems

Authors
Quinaz, T; Freire, TF; Olmos, A; Martins, M; Ferreira, FBN; de Moura, MFSM; Zille, A; Nguyen, Q; Xavier, J; Dourado, N;

Publication
BIOMIMETICS

Abstract
Composites of poly(vinyl alcohol) (PVA) in the shape of braids, in combination with crystals of hydroxyapatite (HAp), were analyzed to perceive the influence of this bioceramic on both the quasi-static and viscoelastic behavior under tensile loading. Analyses involving energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) allowed us to conclude that the production of a homogeneous layer of HAp on the braiding surface and the calcium/phosphate atomic ratio were comparable to those of natural bone. The maximum degradation temperature established by thermogravimetric analysis (TGA) showed a modest decrease with the addition of HAp. By adding HAp to PVA braids, an increase in the glass transition temperature (Tg) is noticed, as demonstrated by dynamic mechanical analysis (DMA) and differential thermal analysis (DTA). The PVA/HAp composite braids' peaks were validated by Fourier transform infrared (FTIR) spectroscopy to be in good agreement with common PVA and HAp patterns. PVA/HAp braids, a solution often used in the textile industry, showed superior overall mechanical characteristics in monotonic tensile tests. Creep and relaxation testing showed that adding HAp to the eight and six-braided yarn architectures was beneficial. By exhibiting good mechanical performance and most likely increased biological qualities that accompany conventional care for bone applications in the fracture healing field, particularly multifragmentary ones, these arrangements can be applied as a fibrous fixation system.

2024

Design of a sensor to estimate suspended sediment transport in situ using the measurements of water velocity, suspended sediment concentration and depth

Authors
Matos, T; Martins, MS; Henriques, R; Goncalves, LM;

Publication
JOURNAL OF ENVIRONMENTAL MANAGEMENT

Abstract
The sediment transport plays a major role in every aquatic ecosystem. However, the lack of instruments to monitor this process has been an obstacle to understanding its effects. We present the design of a single sensor built to measure water velocity, suspended sediment concentration and depth in situ, and how to associate the three variables to estimate and analyse sediment transport. During the laboratory calibrations, the developed instrument presented a resolution from 0.001 g/L to 0.1 g/L in the 0-12 g/L range for the measurement of suspended sediment concentration and 0.05 m/s resolution for 0-0.5 m/s range and 0.001 m/s resolution for 0.5-1 m/s range for the measurement of water velocity. The device was deployed for 6 days in an estuarine area with high sediment dynamics to evaluate its performance. During the field experiment, the sensor successfully measured the tidal cycles and consequent change of flow directions, and the suspended sediment concentration in the area. These measurements allowed to estimate water discharge and sediment transport rates during the different phases of tides, and the daily total volume of water and total amount of sediment passing through the estuary.

2024

Exploring local chlorine generation through seawater electrolysis to Extend optical sensor lifespan in marine environments

Authors
Matos, T; Pinto, VC; Sousa, PJ; Martins, MS; Fernández, E; Goncalves, LM;

Publication
CHEMICAL ENGINEERING JOURNAL

Abstract
Biofouling in marine optical sensors poses a significant challenge as it can compromise data accuracy and instrument functionality. This study investigates the effectiveness of local chlorine generation by seawater electrolysis in mitigating biological fouling and extending the operational lifespan of optical oceanographic instruments. Eight similar turbidity probes integrated with a local chlorine generation system, along with a turbidity probe constructed from ABS and another from PLA with copper filament, were developed for testing in the marine environment. The chlorine probes were designed into two groups: four utilizing standard FTO glass and four featuring FTO glass coated with platinum nanoparticles. Each set of probes employed different excitation currents for chlorine generation. All probes underwent laboratory calibration using formazine before deployment in a coastal environment for 97 days. The findings demonstrate a correlation with higher electrical power leading to prolonged operation intervals free from biofouling interference. Additionally, probes coated with platinum nanoparticles demonstrate higher performance in comparison to those with standard FTO glass. The copper probe did not effectively shield the optical transducers from microfouling, although it effectively demonstrated its efficacy in protecting the structural housing of the device. Overall, this work offers a compelling in situ demonstration of local chlorine generation as a promising strategy for enhancing the performance and longevity of optical oceanographic instruments in marine environments.

2024

A review of methods and instruments to monitor turbidity and suspended sediment concentration

Authors
Matos, T; Martins, MS; Henriques, R; Goncalves, LM;

Publication
JOURNAL OF WATER PROCESS ENGINEERING

Abstract
Turbidity and suspended sediment concentration are crucial parameters indicative of water quality, playing pivotal roles in evaluating the well-being of aquatic ecosystems and the effectiveness of water treatment processes. This manuscript provides an in-depth review of various methods and instruments in use for in situ and inline applications. The exploration of optical instrumentation is central to this review, examining its widespread use and current challenges within standard methods, commercial instruments and scientific research. The study also delves into alternative techniques, such as acoustic and capacitive methods, elucidating their applications, calibration intricacies, and practical considerations. Furthermore, the paper scrutinizes the emerging importance of satellite and aerial imaging processing as a supplementary tool for turbidity monitoring, underscoring its potential to offer comprehensive insights on a larger scale. The review emphasizes the key accomplishments and challenges of the state-of-the-art technologies, providing a comprehensive overview of the current stage of the field and its prospects. and aims to provide valuable insights for researchers, practitioners, and decision-makers involved in environmental monitoring and water facility management, enabling a deeper comprehension of the significance of turbidity and suspended sediment concentration in safeguarding water quality and ecosystem health.

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