Publicaciones del IMSE

Publicaciones recientes

The diverse meteorology of Jezero crater over the first 250 sols of Perseverance on Mars
J.A. Rodriguez-Manfredi, M. de la Torre Juarez, A. Sanchez-Lavega, R. Hueso, G. Martinez, M.T. Lemmon, C.E. Newman, A. Munguira, M. Hieta, L.K. Tamppari, J. Polkko, D. Toledo, E. Sebastian, M.D. Smith, I. Jaakonaho, M. Genzer, A. de Vicente-Retortillo, D. Viudez-Moreiras, M. Ramos, A. Saiz-Lopez, A. Lepinette, M. Wolff, R.J. Sullivan, J. Gomez-Elvira, V. Apestigue, P.G. Conrad, T. Del Rio-Gaztelurrutia, N. Murdoch, I. Arruego, D. Banfield, J. Boland, A.J. Brown, J. Ceballos, M. Dominguez-Pumar, S. Espejo, A.G. Fairén, R. Ferrandiz, E. Fischer, M. Garcia-Villadangos, S. Gimenez, F. Gomez-Gomez, S.D. Guzewich, A.-M. Harri, J.J. Jimenez, V. Jimenez, T. Makinen, M. Marin, C. Martin, J. Martin-Soler, A. Molina, L. Mora-Sotomayor, S. Navarro, V. Peinado, I. Perez-Grande, J. Pla-Garcia, M. Postigo, O. Prieto-Ballesteros, S.C.R. Rafkin, M.I. Richardson, J. Romeral, C. Romero, H. Savijärvi, J. T. Schofield, J. Torres, R. Urqui, S. Zurita & the MEDA team
Journal Paper · Nature Geoscience, 2023
NATURE    ISSN: 1752-0894
resumen      doi      

NASA’s Perseverance rover’s Mars Environmental Dynamics Analyzer is collecting data at Jezero crater, characterizing the physical processes in the lowest layer of the Martian atmosphere. Here we present measurements from the instrument’s first 250 sols of operation, revealing a spatially and temporally variable meteorology at Jezero. We find that temperature measurements at four heights capture the response of the atmospheric surface layer to multiple phenomena. We observe the transition from a stable night-time thermal inversion to a daytime, highly turbulent convective regime, with large vertical thermal gradients. Measurement of multiple daily optical depths suggests aerosol concentrations are higher in the morning than in the afternoon. Measured wind patterns are driven mainly by local topography, with a small contribution from regional winds. Daily and seasonal variability of relative humidity shows a complex hydrologic cycle. These observations suggest that changes in some local surface properties, such as surface albedo and thermal inertia, play an influential role. On a larger scale, surface pressure measurements show typical signatures of gravity waves and baroclinic eddies in a part of the seasonal cycle previously characterized as low wave activity. These observations, both combined and simultaneous, unveil the diversity of processes driving change on today’s Martian surface at Jezero crater.

Accurate Face Recognition on Highly Compressed Samples
A. Khan, J. Fernández-Berni and R. Carmona-Galán
Conference · International Conference on Signal Image Technology and Internet Based Systems SITIS 2022

Compressive sensing is an emerging field for lowdimensional data acquisition. Samples are acquired in the compressed domain and utilized for signal reconstruction or as input features for a classifier. In this work, hardware-aware face recognition using compressed samples was investigated. A linear support vector machine (SVM) classifier was exploited with compressed samples as input features; Faces can be reliably recognized with high average accuracy (up to 99%). To assess the robustness of the proposed scheme, three image datasets covering different facial and illumination conditions were analyzed. Random (binary) and structured (Haar-transform-based) measurement matrices were employed for generating compressed samples. For one of the datasets, Extended Yale B, and using a random binary measurement matrix, the proposed scheme achieved 82% accuracy from as few as 15 compressed samples, which means a 1/20480 sensing ratio. Accuracy and compression are also remarkably high with respect to the state-of-the-art for the other two datasets.

A Facial Authentication System using Post-Quantum-Secure Data Generated on Mobile Devices
P. López-González, R. Arjona, R. Román and I. Baturone
Conference · International Conference on Mobile Computing and Networking MOBICOM 2022

This paper describes a demonstrator of a post-quantum-secure facial authentication system distributed between a mobile device acting as a client and a remote computer acting as an authentication server. Homomorphic encryption based on Classic McEliece, one of the fourth-round candidates of the NIST post-quantum standardization process, is carried out by the client for protecting the biometric data extracted from the users’ faces at enrollment and verification. The remote computer only stores and compares the received protected data, thus preserving user privacy. An Android App and a Graphical User Interface (GUI) were implemented at the client and the server, respectively, to show the system performance in terms of computation and security.

A Methodology for Defect Detection in Analog Circuits based on Causal Feature Selection
G. Leger, A. Gines, V. Gutierrez and M.J. Barragan
Conference · IEEE International Conference on Electronics Circuits and Systems ICECS 2022

The cost of assuring test quality significantly increases when dealing with complex systems with tightly integrated AMS-RF building blocks. Machine learning-based test may be a promising solution to this issue. These tests rely on regression models trained to replace costly performance measurements by simpler test signatures. However, these regression models are targeted only at parametric performance variations in defect-free circuits. The presence of spot defects may be undetected by these tests and lead to test quality degradation and reliability issues. In this work we propose a methodology based on causal discovery algorithms to screen out these spot defects.

Mitigating the Impact of Variability in NCFET-based Coupled-Oscillator Networks Applications
J. Núñez, S. Thomann, H. Amrouch and M.J. Avedillo
Conference · IEEE International Conference on Electronics Circuits and Systems ICECS 2022

Coupled oscillators are attracting increasing interest because of their potential to perform computation efficiently, enabling new applications in computing and information processing. Coupled nano-oscillator implementations using emerging devices have arisen, but the immaturity of these technologies has allowed only simple experimental demonstrations. The potential of Negative Capacitance FET (NCFET) for such applications has recently been recognized, which is a step towards the physical realization given their ease of co-integration with commercial CMOS technologies. However, the design of circuits using these devices can be seriously compromised by the variability inherent in them. In this paper, we will highlight this problem through the design of an oscillatory neural network for pattern recognition applications. We propose the application of subharmonic injection mechanisms to mitigate the impact of NCFET transistor variability and present results showing that the performance of these circuits improves significantly.

Uso de la termografía para el análisis y seguimiento de los hemangiomas infantiles
J.A. Leñero, J.A. Pérez-Carrasco, C. Serrano, B. Acha, J.O. Álvárez and J. Bernabéu-Wittel
Conference · Congreso Anual de la Sociedad Española de Ingeniería Biomédica CASEIB 2022

Los hemangiomas infantiles se encuentran entre los tumores más comunes en los bebés. Para una correcta evolución es fundamental determinar su extensión, volumen y ubicación. Sin embargo, esto puede representar un desafío, ya que los hemangiomas pueden presentar patrones irregulares, estar cubiertos por cabello y su profundidad no se puede estimar fácilmente. Habitualmente, su diagnóstico se basa en estimaciones de área, textura y color. En este trabajo presentamos una técnica alternativa de diagnóstico, la termografía, que es una herramienta útil e inmediata para un examen preciso de los hemangiomas. Los hemangiomas alteran localmente la temperatura corporal, debido a que el flujo sanguíneo en su interior es mayor debido a la proliferación de células endoteliales de los vasos sanguíneos. Por tanto, midiendo las variaciones de temperatura en la piel, se puede estimar la extensión del hemangioma. Se analizaron 30 pacientes con hemangiomas infantiles con una cámara térmica durante varias sesiones en dos fases. A raíz de los resultados obtenidos concluimos que un aumento de la temperatura en el interior del tumor durante el seguimiento era indicativo de una evolución no deseable.

Experimental Validation of a High-Voltage Compliant Neural Stimulator Implemented in a Standard 1.8V/3.3V CMOS Process
D. Palomeque-Mangut, A. Rodríguez-Vázquez and M Delgado-Restituto
Conference · IEEE Biomedical Circuits and Systems Conference BioCAS 2022

This paper describes a neural stimulator with 4 × VDD compliance voltage, delivering up to 2.08 mA, and implemented in a standard 180nm 1.8V/3.3V CMOS Process. The wide range of stimulation currents and high compliance voltage makes it suitable for stimulation applications both in rodents and mammals. Besides, it can be configured both as electrical and optical stimulator. Stacked transistor cells with dynamic gate biasing have been used for withstanding voltages well above the nominal supply. The system has been fabricated, occupying an active area of 2.34mm2. The circuit has been experimentally tested by connecting it to a custom μelectrode array which was immersed into a phosphate-buffered saline solution.

Post-Quantum Secure Communication with IoT Devices Using Kyber and SRAM Behavioral and Physical Unclonable Functions
R. Román, R. Arjona and I. Baturone
Conference · International Workshop on Attacks and Defenses for Internet-of-Things ADIoT 2022

For a secure Internet-of-Things (IoT) ecosystem, not only the estab-lishment of secure communication channels but also the authentication of devices is crucial. Authenticated key exchange protocols establish shared cryptographic keys between the parties and, in addition, authenticate their identities. Usually, the identities are based on a pair of private and public keys. Physical Unclonable Functions (PUFs) are widely used recently to bind physically the private key to a device. However, since PUFs are vulnerable to attacks, even non-invasive at-tacks without accessing the device, this paper proposes the use of Behavioral and Physical Unclonable Functions (BPUFs), which allow multimodal authentication and are more difficult to be virtually or physically cloned. In order to resist at-tacks from classic and quantum computers, this paper considers a Kyber key ex-change protocol. Recently, Kyber has been selected by the Post-Quantum Cryp-tography standardization process of the National Institute of Standards and Tech-nology (NIST) for key establishment protocols. In this work, we propose to strengthen a Kyber key exchange protocol with BPUFs extracted from SRAMs included in IoT devices. Experimental results prove the feasibility of the proposal in WiPy boards.

True Random Number Generation Capability of a Ring Oscillator PUF for Reconfigurable Devices
L.F. Rojas-Muñoz, S. Sánchez-Solano, M.C. Martínez-Rodríguez and P. Brox
Journal Paper · Electronics, vol. 11, no. 23, article 4028, 2022
MDPI    ISSN: 2079-9292
resumen      doi      

This paper presents the validation of a novel approach for a true-random number generator (TRNG) based on a ring oscillator-physical unclonable function (RO-PUF) for FPGA devices. The proposal takes advantage of the different noise sources that affect the electronic implementation of the RO-PUF to extract the entropy required to guarantee its function as a TRNG, without anything more than minimal changes to the original design. The new RO-PUF/TRNG architecture has been incorporated within a hybrid HW/SW embedded system designed for devices from the Xilinx Zynq-7000 family. The degree of randomness of the generated bit streams was assessed using the NIST 800-22 statistical test suite, while the validation of the RO-PUF proposal as an entropy source was carried out by fulfilling the NIST 800-90b recommendation. The features of the hybrid system were exploited to carry out the evaluation and validation processes proposed by the NIST publications, online and on the same platform. To establish the optimal configuration to generate bit streams with the appropriate entropy level, a statistical study of the degree of randomness was performed for multiple TRNG approaches derived from the different implementation modes and configuration options available on the original RO-PUF design. The results show that the RO-PUF/TRNG design is suitable for secure cryptographic applications, doubling its functionality without compromising the resource-efficiency trade-off already achieved in the design.

Using ANNs to Predict Frequency Spectrum Occupancy in Cognitive-Radio Receivers
P.I. Okorie, L.A. Camuñas-Mesa and J.M. de la Rosa
Conference · Conference on Design of Circuits and Integrated Systems DCIS 2022

This paper analyses the use of Artificial Neural Networks (ANNs) to identify vacant portions of the electromagnetic spectrum or frequency holes in Cognitive Radio (CR) systems. Several ANN topologies are considered, including Convolutional Neural Networks (CNNs), Long Short-Term Memory (LSTM) networks or hybrid combinations of them. These ANNs are modeled and compared in terms of their complexity, speed and accuracy of the prediction. As an application, a CR-based receiver is simulated, where Radio-Frequency (RF) signals are digitized by a Band-Pass Sigma-Delta Modulator (BP-ΣΔM) with a tunable notch frequency, which is modified according to the less occupied band predicted by the ANNs.
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