RCIPL
Institutional Repository of the Lisbon Polytechnic
Recent Submissions
Towards feature engineering for intrusion detection in IEC-61850 communication networks
Publication . Quincozes, Vagner; Ereno Quincozes, Silvio; Passos, Diego; Albuquerque, Célio; Mosse, Daniel
Digital electrical substations are fundamental in providing a reliable basis for smart grids. However, the deployment of the IEC-61850 standards for communication between intelligent electronic devices (IEDs) brings new security challenges. Intrusion detection systems (IDSs) play a vital role in ensuring the proper function of digital substations services. However, the current literature lacks efficient IDS solutions for certain classes of attacks, such as the masquerade attack. In this work, we propose the extraction and correlation of relevant multi-layer information through a feature engineering process to enable the deployment of machine learning-based IDSs in digital substations. Our results demonstrate that the proposed solution can detect attacks that are considered challenging in the literature, attaining an F1-score of up to 95.6% in the evaluated scenarios.
From the lebombo monocline to the Mozambique deep basin, using combined wide-angle and reflection seismic data
Publication . Moulin, Maryline; Leprêtre, Angelique; Verrier, Fanny; Schnürle, Philippe; Evain, Mikael; Clarens, Philippe; Thompson, Joseph; Dias, Nuno; Afilhado, Alexandra; Loureiro, Afonso; Aslanian, Daniel
The North Natal valley (NNV), South Mozambique margin, is a key area for the understanding of the SW Indian Ocean history since the Gondwana break-up as its crustal nature and geometry strongly impacted the recon-struction of the paleogeography before the rifting. It is also of considerable importance for the understanding of the evolution of a margin system as the NNV is situated at the transition between divergent and strike-slip segments and at the conjunction of Oxfordian-Kimmeridgian Indian Ocean and the Valanginian-Aptian Atlantic one. As one part of the PAMELA project (PAssive Margins Exploration Laboratories), the NNV and the East Limpopo margin have been investigated during the MOZ3/5 cruise (2016), through the acquisition of 7 intersecting wide-angle profiles and coincident marine multichannel (720 traces) seismic as well as potential field data. Simultaneously, land seismometers were deployed in the Mozambique coastal plain (MCP), extending six of those profiles on land for about 100 km in order to provide information on the onshore-offshore transition. Wide-angle seismic data are of major importance as they can highlight constraints on the crustal structure of the margin and the position of the continent-ocean boundary in an area where the crustal nature is poorly known and largely controversial. The MOZ3/5 data set therefore reveals new essential constraints for kinematic re-constructions. This work presents results on the crustal structure from P-waves velocity modeling along two E-W wide-angle profiles (MZ1 and MZ2) through the NNV, from the Lebombo Monocline to the Mozambique Basin (MB), and crossing the Mozambique Fracture Zone (MFZ). The new geophysical data reveals an upper sedimentary sequence characterized by low velocities generally not exceeding 3 km/s, and up to 3 km thick where a major contouritic structure was observed. This feature formes together with several other contouritic structures, a N-S alignment just west of the MFZ, which produces high positive gravity anomalies, previously thought to be related to the magmatism that built the Galathea and Dana Plateaus. High velocity lenses are locally identified through the sedimentary layers and interpreted as inter-bedded volcanic sills. Furthermore, from the NNV to the MFZ, the underlying sequence is formed of a 3.0-3.5 km thick volcano-sedimentary sequence presenting important lateral changes in its seismic signature and characterized by a large velocity range (4.4 to 5.8 km/s), which partly reflects variations in the volcanic/sedi-mentary ratio laterally and with depth. At depth, an initially smoother and reduced eastward thinning of the crust occurs to the West below the continental shelf, from 34 to 31 km thick. The crustal thickness remains relatively constant of about 28-29 km along the Central Domain (CD), whereas a second and major region of thinning (26 to 12 km thick) is imaged West of the MFZ, in the southward prolongation of the Limpopo Corridor (LC). By contrast, as the eastern extremity, the crust is <10 km thick when reaching the MB. Crustal velocities reveal low velocity gradients, with atypical high velocities, increasing to 7.3 to 7.6 km/s at the base of the crust, and globally in the whole crust in the LC, just West of the MFZ. We interpreted the velocity architecture com-bined with the evidence of volcanism at shallower depths as indicative of an intensively intruded continental
Freeze-in as a complementary process to freeza-out
Publication . Capucha, Rodrigo; Elyaouti, Karim; Mühlleitner, Margarete; Plotnikov, Johann; Santos, Rui
There are many extensions of the Standard Model with a dark matter (DM) candidate obtained via the freeze-out mechanism. It can happen that after all experimental and theoretical constraints are taken into account, all parameter points have a relic density below the experimentally measured value. This means that the models solve only partially the DM problem, and at least one more candidate is needed. In this work we show that it is possible to further extend the model with a DM candidate obtained via the freeze-in mechanism to be in agreement with the relic density experimental measurement. Once the relic density problem is solved with this addition, new questions are raised. This new model with at least two DM candidates could have a freeze-out undetectable DM particle both in direct and indirect detection. This could happen if the freeze-out DM particle would have a very low density. Hence, a collider DM hint via excess in the missing energy with no correspondence in direct and indirect detection experiments, could signal the existence of a Feebly Interacting Massive Particle (FIMP). Conversely, if a DM particle is found and a particular model can explain all observables except the correct relic density, an extension with an extra FIMP would solve the problem. The freeze-in DM candidate, due to the small portal couplings, will not change the remaining phenomenology.
P-xylene oxidation to terephthalic acid: New trends
Publication . dos Anjos Carvalho Lapa, Hugo Miguel; Martins, Luisa
Large-scale terephthalic acid production from the oxidation of p-xylene is an especially important process in the polyester industry, as it is mainly used in polyethylene terephthalate (PET) manufacturing, a polymer that is widely used in fibers, films, and plastic products. This review presents and discusses catalytic advances and new trends in terephthalic acid production (since 2014), innovations in terephthalic acid purification processes, and simulations of reactors and reaction mechanisms.
Deep learning soft-decision GNSS multipath detection and mitigation
Publication . Nunes, Fernando; Sousa, Fernando
A technique is proposed to detect the presence of the multipath effect in Global Navigation Satellite Signal (GNSS) signals using a convolutional neural network (CNN) as the building block. The network is trained and validated, for a wide range of 𝐶/𝑁0
values, with a realistic dataset constituted by the synthetic noisy outputs of a 2D grid of correlators associated with different Doppler frequencies and code delays (time-domain dataset). Multipath-disturbed signals are generated in agreement with the various scenarios encompassed by the adopted multipath model. It was found that pre-processing the outputs of the correlators grid with the two-dimensional Discrete Fourier Transform (frequency-domain dataset) enables the CNN to improve the accuracy relative to the time-domain dataset. Depending on the kind of CNN outputs, two strategies can then be devised to solve the equation of navigation: either remove the disturbed signal from the equation (hard decision) or process the pseudoranges with a weighted least-squares algorithm, where the entries of the weighting matrix are computed using the analog outputs of the neural network (soft decision).