Polytechnic University of Catalonia

The Hilda group is a set of asteroids whose mean motion is in a 3:2 orbital resonance with Jupiter. In this paper, we use the planar Circular Restricted Three-Body Problem (CRTBP) as a dynamical model and we show that there exists a family of stable periodic orbits that are surrounded by islands of quasi-periodic motions. We have computed the frequencies of these quasi-periodic motions and we have shown how the Hilda family fits inside these islands. We have compared these results with the ones obtained using the Elliptic Restricted Three-Body Problem and they are similar, showing the suitability of the CRTBP model. It turns out that, to decide if a given asteroid belongs to the Hilda class, it is much better to look at its frequencies in the planar CRTBP rather than to use two-body orbital elements as it is commonly done today.

Researchers have extensively focused on the safety of the solid propellant preparation process, particularly the mixing process that was deemed critical for the safety of the entire procedure. Herein, the rheological curves of propellants at different stages of mixing are obtained experimentally. The obtained curves are fitted using the Herschel–Bulkley non-Newtonian model. CFD calculations were performed using this data, allowing us to obtain the pressure and velocity evolution within the fluid domain during mixing. Such calculations are then used to assess the variation in the homogeneity of the mixture over time. Experimental evidence reveals that the viscosity of the composite propellant slurry is 32 Pa s after the addition of fine-grained ammonium perchlorate (AP). The propellant slurry tends to be 15 Pa s at the end of mixing. Both the morphology and elemental analysis of the slurry demonstrated that the fine AP is more distributed near the coarse AP. In contrast, the aluminum powder is distributed more evenly within the propellant matrix. Moreover, theoretical simulation input parameters are obtained using the Herschel–Bulkley model fitting. Numerical simulation results show that the paddle and the inner wall are more prone to a sudden increase in pressure and velocity concentration due to the shear effect, and the mixing homogeneity and safety analysis of the propellant slurry can be visualized in a short time period.

Objective: Signal denoising methods based on deep learning have been extensively adopted on Electroencephalogram(EEG) devices. However, they are unable to deploy on edge-based portable or wearable (P/W) electronics due to the high computational complexity of the existed models. To overcome such issue, we propose an edge-based lightweight Kalman filter network (EKFNet) that does not require manual prior knowledge estimation. Approach: Specifically, we construct a multi-scale feature fusion (MSFF) module to capture multi-scale feature information and implicitly compute the prior knowledge. Meanwhile, we design an adaptive gain estimation (AGE) module that incorporates long short-term memory (LSTM) and sequential channel attention module (CAM) to dynamically predict the Kalman gain. Furthermore, we present an optimization strategy utilizing operator fusion and constant folding to reduce the model’s computational overhead and memory footprint. Main results: Experimental results show that the EKFNet reduces the sum of the square of the distances by at least 12% and improves the cosine similarity by at least 2.2% over the state-of-the-art methods. Besides, the model optimization shortens the inference time by approximately 3.3×. The code of our EKFNet is available at https://github.com/cathnat/EKFNet. Significance: By integrating Kalman filter with deep learning, the approach addresses the parameter-setting challenges in traditional algorithms while reducing computational overhead and memory consumption, which exhibits a good tradeoff between algorithm performance and computing power.

METASAT is a recently started project (January 2023) in the Horizon Europe programme, in the SPACE call, coordinated by the Barcelona Supercomputing Center (BSC). METASAT will develop model-based design (MBD) solutions for high performance on-board processors such as multicores, Graphics Processing Units (GPUs) and Artificial Intelligence (AI) Accelerators. While the developed tools and methodologies are particularly focusing on the space domain, reusability to other safety critical domains is also a project goal. This talk will provide an overview of the solutions which will be developed during the project, which will be centered around the open source TASTE framework used at the European Space Agency (ESA), which leverages AADL.

We show that for a wide range of channels and code ensembles with pairwise-independent codewords, with probability tending to 1 with the code length, expurgating an arbitrarily small fraction of codewords from a randomly selected code results in a code attaining the expurgated exponent.

The expansion of renewable energy sources highly increased the number of grid-connected converters associated to PV and wind in power plants as well as in residential areas. The appearance of voltage harmonics, which are typically generated by a large number of devices, is a common issue in weak grid environments and it is transitioning to the main utility grid. This harmonic distortion is significantly increasing due to the interaction between electronic power converters and the network, which not only contribute to damage other equipment connected to the same point of common connection (PCC), but also increase the losses and saturation of the transformers in the line. While previous studies have extensively addressed this issue for grid-following power converters, the harmonic control in parallel grid-forming converters, particularly those based on virtual synchronous emulation, remains underexplored. This paper intends to provide a solution focused on providing a selective harmonic control for synchronous power controller (SPC) based power converters. The proposed solution enables the parallelization of power converters to naturally share the harmonics attenuation effect at the PCC. The methodology is presented and validated through real-time simulations as well as experimental tests conducted in a 200 kVA microgrid testbed.

The capability of graphene oxide (GO) to enhance direct interspecies electron transfer (DIET) and improve anaerobic digestion (AD) performance is gaining attention in AD literature. The present review discusses the implications of GO and its ambivalent role in AD. Under anaerobic conditions, GO is rapidly converted to biologically reduced graphene oxide (bioRGO) through microbial respiration. GO addition could promote the release of extracellular polymeric substances and lead to toxic effects on anaerobic microorganisms. However, further research is needed to determine the GO toxic concentration thresholds. GO application can impact biogas production and organic micropollutants removal of anaerobic digesters. Nevertheless, most of the studies have been conducted at batch scale and further work in continuously operated anaerobic digesters is still needed. Finally, the review evaluates the economic potential of GO application in AD systems. Overall, this review lays the foundations to improve the applicability of GO in future full-scale digesters.

Corona discharge testing is critical to ensuring the safety, performance and reliability of high-voltage equipment and systems. Due to the high cost of shielded laboratories, many manufacturers test their components in unshielded laboratories for applications such as product research and development or quality control. This paper compares the sensitivity of two corona detection instruments in an unshielded laboratory. The sensitivity of an electrical detector according to IEC 60270 in combination with a measuring impedance and a coupling capacitor is compared with that of a digital single lens reflex (DSLR) camera. In addition, needle-to-plane and sphere-to-plane electrode geometries are studied under different types of high-voltage power supplies, i.e., 50 Hz alternating current (AC), positive direct current (DC+), and negative direct current (DC-). Experimental results performed in an unshielded high-voltage laboratory show that although the DSLR camera is not a standard method for PD detection, it has similar sensitivity to the conventional electrical method according to IEC 60270 in all cases analyzed, and that the digital camera behaves much better in pulseless glow corona mode

The i* modeling language was introduced to fill the gap in the spectrum of conceptual modeling languages, focusing on the intentional (why?), social (who?), and strategic (how? how else?) dimensions. i* has been applied in many areas, e.g., healthcare, security analysis, and e-commerce. Although i* has seen much academic application, the diversity of extensions and variations can make it difficult for novices to learn and use it in a consistent way. This chapter introduces the iStar 2.0 core language, evolving the basic concepts of i* into a consistent and clear set of core concepts, upon which to build future work and to base goal-oriented teaching materials. This chapter presents a more comprehensive illustrative example compared to the paper that first introduced iStar 2.0.

Terahertz time‐domain spectroscopy (THz–TDS) is a nondestructive imaging and characterization technique. It is currently used in the field of material science to obtain the surface conductivity and transmittance of bulk and 2D materials in the range from hundreds of GHz up to few THz. In this research, an alternative setup of the THz–TDS technique is proposed, based on a Michelson interferometer, with a double pass through the sample using a mirror and a semitransparent wafer. A single‐branch configuration is used to characterize a few‐layer WS 2 sample on a fused quartz substrate. The objectives of the experiment are to demonstrate that the configuration is viable for obtaining the parameters of the sample and the substrate, to present the models and equations used, and to explain the advantages and limitations of the method compared to the transmission configuration. The optical transmittance and surface conductivity of WS 2 are obtained with the new configuration in the frequency range from 0.2 to 1.2 THz. Raman spectroscopy is used to analyze the sample quality before performing the measurements.

We present a novel space‐time Bayesian hierarchical model (BHM) to reconstruct annual Sea Surface Temperature (SST) over a large domain based on SST at limited proxy (i.e., sediment core) locations. The model is tested in the equatorial Pacific. The BHM leverages Principal Component Analysis to identify dominant space‐time modes of contemporary variability of the SST field at the proxy locations and employs these modes in a Gaussian process framework to estimate SSTs across the entire domain. The BHM allows us to model the mean field and covariance, varying in space and time in the process layers of the hierarchy. Using the Markov Chain Monte Carlo (MCMC) method and suitable priors on the model parameters, posterior distributions of the model parameters and, consequently, posterior distributions of the SST fields and the attendant uncertainties are obtained for any desired year. The BHM is calibrated and validated in the contemporary period (1854–2014) and subsequently applied to reconstruct SST fields during the Holocene (0–10 ka). Results are consistent with prior inferences of La Niña‐like conditions during the Holocene. This modeling framework opens exciting prospects for modeling and reconstruction of other fields, such as precipitation, drought indices, and vegetation.

X‐Ray bursts (XRBs) are powerful thermonuclear events on the surface of accreting neutron stars (NSs), which can synthesize intermediate‐mass elements. Although the high surface gravity prevents an explosive ejection, a small fraction of the envelope may be ejected by radiation‐driven winds. In our previous works, we have developed a non‐relativistic radiative wind model and coupled it to an XRB hydrodynamic simulation. We now apply this technique to another model featuring consecutive bursts. We determine the mass‐loss and chemical composition of the wind ejecta. Results show that, for a representative XRB, about of the envelope mass is ejected per burst, at an average rate of . Between and of the ejecta composition is ⁶⁰ Ni, ⁶⁴ Zn, ⁶⁸ Ge, ⁴ He and ⁵⁸ Ni. We also report on the evolution of observational quantities during the wind phase and simulate NICER observations that resemble those of 4 U 1820–40.

This paper presents a novel methodology that combines Particle Image Velocimetry - Numerical Particles (PIV-NP) and Short-Wave Infrared Spectral Imaging for the non-invasive measurement of displacements and degree of saturation on moving soils. This allows for continuous monitoring and visualization of soil behavior and provides valuable insight into the deformation patterns and moisture evolution. The method was applied to a small-scale dam failure experiment. The methodology offers an integrated, comprehensive, and non-invasive approach to investigating soil physical models by simultaneously measuring displacements, strains, velocities, and degree of saturation in soils in motion.

The impact of cognitive biases on decision-making in the digital world remains under-explored despite its well-documented effects in physical contexts. This paper addresses this gap by investigating the attractiveness halo effect using AI-based beauty filters. We conduct a large-scale online user study involving 2748 participants who rated facial images from a diverse set of 462 distinct individuals in two conditions: original and attractive after applying a beauty filter. Our study reveals that the same individuals receive statistically significantly higher ratings of attractiveness and other traits, such as intelligence and trustworthiness, in the attractive condition. We also study the impact of age, gender and ethnicity and identify a weakening of the halo effect in the beautified condition, resolving conflicting findings from the literature and suggesting that filters could mitigate this cognitive bias. Finally, our findings raise ethical concerns regarding the use of beauty filters.

This report offers a comprehensive overview of Zambia’s energy system, focusing on consumption trends, energy production, and the associated challenges. The first in a three-part series, it serves as the basis for understanding Zambia’s energy framework by highlighting the critical sectors that shape the nation’s energy dynamics and the broader implications for sustainable growth. Zambia’s energy system is characterised by a dependence on traditional energy sources, particularly hydropower and biomass, which has constrained the country’s ability to achieve energy security and sustainability. The urgent need for reforms to diversify energy sources, modernise infrastructure, and implement cost-reflective tariffs is evident. Addressing these issues is crucial for improving energy access and supporting Zambia’s broader development objectives.

This report delves into the essential technologies and strategies that Zambia can adopt to transition towards a sustainable, low-carbon energy future. It is the second in a series of three reports and explores the intersection of technology, policy, and investment, providing a roadmap for reducing emissions while maintaining economic growth and improving energy security. The report acknowledges the significant challenges that lie ahead. Financing remains a major barrier, with limited access to capital for large-scale renewable projects and carbon removal initiatives. Additionally, the technical capacity to implement and maintain new technologies is still developing, requiring targeted training and knowledge transfer initiatives. With the right mix of policy incentives, technological investments, and international collaboration, Zambia could potentially position itself as a leader in low-carbon development within the region, while simultaneously achieving its climate goals and improving energy security.