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Semi-analytic construction of global transfers between quasi-periodic orbits in the spatial R3BP
No full textConsider the spatial restricted three-body problem, as a model for the motion of a spacecraft relative to the Sun-Earth system. We focus on the dynamics near the equilibrium point L1 located between the Sun and the Earth. We show that we can transfer the spacecraft from a quasi-periodic orbit that is nearly planar relative to the ecliptic to a quasi-periodic orbit that has large vertical amplitude, at zero energy cost. (In fact, the final orbit has the maximum vertical amplitude that can be obtained through the particular mechanism that we consider. Moreover, the transfer can be made through any prescribed sequence of quasi-periodic orbits in between). Our transfer mechanism is based on selecting trajectories homoclinic to a normally hyperbolic invariant manifold (NHIM) near L1 and then gluing them together. We present a theoretical result establishing the existence of such transfer orbits, and we verify numerically its applicability to our model. We provide several explicit constructions of such transfers, and also develop an algorithm to design trajectories that achieve the shortest transfer time for this particular mechanism. The change in the vertical amplitude along a homoclinic trajectory can be described via the scattering map. We develop a new tool, the ‘Standard Scattering Map’ (SSM), which is a series representation of the exact scattering map. We use the SSM to obtain a complete description of the dynamics along homoclinic trajectories. The SSM can be used in many other situations, from Arnold diffusion problems to transport phenomena in applications.Peer ReviewedPostprint (published version
Bioactive and degradable peg hydrogels: a multifunctional approach for tissue regeneration and antibacterial protection
No full textBiomaterial-associated infections pose a significant challenge, impairing tissue integration and frequently leading to implant failure and revision surgeries. Upon implantation, host cells and bacteria compete for colonizing the implant, in a process known as the “race for the surface,” which is critical for the long-term survival of the implant. However, conventional biomaterials commonly fail to simultaneously promote cellular integration and prevent infections. To address this issue, we developed a protease-degradable PEG hydrogel functionalized with the RGD integrin-binding motif to enhance cell adhesion and the antimicrobial peptide hLf1–11 (LF) to provide antibacterial activity. This hydrogel was crosslinked using a protease-sensitive peptide (VPM), enabling enzymatic degradation, and dynamic adaptation to the cellular microenvironment (PEG-RGDLF). Non-bioactive but degradable (PEG-50) and neither bioactive nor degradable (PEG-0) hydrogels were included as controls. PEG-RGDLF hydrogels showed an adequate internal structure, with well-defined porosity, swelling capacity, and protease-mediated degradation rate. PEG-RGDLF improved the adhesion, spreading, proliferation, and ALP activity of human bone marrow mesenchymal stem cells (hBMSCs) and reduced the viability and adhesion of Gram-positive and Gram-negative bacteria, significantly affecting their morphology. Furthermore, co-culture models were established under two clinically relevant scenarios: “pre-infection” and “post-infection”. In both settings, PEG-RGDLF hydrogels supported enhanced cellular responses, with hBMSCs displaying an elongated morphology and improved adhesion. In summary, by integrating cell-instructive and antibacterial properties with a controlled degradation mechanism, this multifunctional hydrogel presents a robust platform for implant-based therapies, actively promoting tissue regeneration while preventing infection, thus addressing the persistent challenge of implant-associated infections in regenerative medicine and clinical applications.This project has received funding from the Agencia Estatal de Investigación through grants PID2020-114019RB-I00 and PID2023-148538OB-I00. This work is part of Maria de Maeztu Units of Excellence Program CEX2023-001300-M / funded by MCIN/AEI / 10.13039/501100011033. The authors also thank financial support from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant Agreement No. 872869 (RISE Project Bio-TUNE), as well as the Generalitat de Catalunya for the predoctoral fellowship of P.L.-G. (AGAUR 2021 FI_B 00889), the ICREA Academia award of M.-P. G and the SGR recognition (2021 SGR 01368).Peer ReviewedPostprint (published version
A benchmark simulator for advanced control of ethanol steam reforming
No full text© 2025 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).This article presents a nonlinear dynamic simulator of an ethanol steam reforming process designed for pure hydrogen production for fuel-cell applications. The process consists of two stages: alcohol reforming and hydrogen separation within a staged-separation membrane reactor. The simulator is intended to serve as a benchmark for developing and testing advanced control, estimation, and optimization strategies. The simulator is extensively validated with experimental data. Detailed descriptions of the experimental setup, key modeling assumptions, and reference operating conditions are provided. Furthermore, critical control challenges that must be addressed to achieve optimal process operation are identified, along with quantitative metrics for evaluating the performance of control strategies implemented by users. A set of case studies illustrate the implementation of a proportional–integral–derivative (PID) controller in the benchmark simulator for tracking a hydrogen flow set-point and effectively rejecting disturbances. The benchmark simulator is developed in MATLAB® and is available in an online repository.This work was supported in part by the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR), Generalitat de Catalunya, Spain under Grant FI SDUR 2023 FISDU 00160 and the Spanish project SEAMLESS: Sustainable learning-based Management of Multi-resource Large-scale Systems (ref. PID2023-148840OB-I00), funded by MCIN/AEI/10.13039/501100011033/FEDER, UE.Peer ReviewedPostprint (published version
Thermodynamic-kinetic relationship in Pd-based metallic glasses
No full textEstablishing a direct correlation between thermodynamic and kinetic behaviors in metallic glasses is of paramount importance, yet it remains an unresolved challenge in the field. Here, we conduct a comprehensive investigation on Pd-based metallic glasses, integrating dynamic mechanical analysis and differential scanning calorimetry to probe the interplay between mechanical relaxation and thermodynamic properties. Our results demonstrate that the temperature-dependent evolution of excess entropy remarkably parallels the kinetic spectrum, providing compelling evidence for a strong thermodynamic-kinetic relationship. Notably, we quantitatively explore the relationship between stress relaxation kinetics and excess entropy. This work provides new insights into the intrinsic coupling between thermodynamic disorder and mechanical relaxation behaviors in metallic glasses, offering a novel framework for understanding glass transition dynamics.Postprint (author's final draft
Computer validation of open gaps for the almost Mathieu operator with critical coupling
No full textWe present some computer assisted methods to prove the existence of spectral gaps for the Almost Mathieu operator at critical coupling and give rigorous numerical estimates on their size. As an example we show that the first 8 gaps predicted by the Gap Labelling theorem are open when the frequency ¿ is v 5-1)/2 and 12 of them are open when ¿=¿-2. A dynamical method based on the constructive conjugation to a hyperbolic cocycle and a spectral method based on the rigorous computation of the eigenvalues of finite-dimensional matrices are presented. We also present some experiments and conjectures on gap size for the associated periodic problems.Jordi-Lluís Figueras has been partially supported by the VR Grant 2024-04764. The research of Joaquim Puig is supported by the grant PID-2021-122954NB-100 funded by MCIN/AEI (Spain) and “ERDF: A way of making Europe”Postprint (published version
A new methodology for ultra-fast and accurate statistical EMT analysis in electric power-systems
No full textThis paper introduces Quadrature Mirror Filter Electromagnetic Transient (QMF-EMT) methodology as a novel, precise, and ultra-fast method for statistical studies (SS) of EMTs in electrical networks. Building on a previously proposed approach for real-time EMT simulation, QMF-EMT incorporates nonlinear elements such as surge arresters, sequential switching operations, and a statistical switching model. The method is highly parallelizable and achieves superior accuracy and computational speed compared to conventional time-domain (TD) and frequency-domain (FD) techniques. The effectiveness of QMF-EMT is demonstrated through its application to the statistical analysis of two test networks. Validation is performed by comparing the results with established techniques, including PSCAD/EMTDC and the Numerical Laplace Transform (NLT) method. The case studies include the integration of surge arresters, controlled switching operations as overvoltage (OV) mitigation measures, and a large-scale network comprising 39 three-phase nodes. Notably, QMF-EMT's high computational speed on conventional CPUs enables efficient determination of the required number of events and integration steps for statistical analyses. This work underscores QMF-EMT's potential as a transformative tool for addressing computational challenges in EMT studies, particularly in large-scale power-systems.This work was supported in part by the National Council of Science and Technology (CONACYT), Mexico, under Grant No. 1074592. The work of Luis A. Garcia-Reyes received funding from the ADOreD project, part of the European Union’s Horizon Europe Research and Innovation Programme, under the Marie Skłodowska-Curie Grant Agreement No. 101073554.Peer ReviewedPostprint (published version
PGD-based local surrogate models via overlapping domain decomposition: A computational comparison
No full textAn efficient strategy to construct physics-based local surrogate models for parametric linear elliptic problems is presented. The method relies on proper generalized decomposition (PGD) to reduce the dimensionality of the problem and on an overlapping domain decomposition (DD) strategy to decouple the spatial degrees of freedom. In the offline phase, the local surrogate model is computed in a non-intrusive way, exploiting the linearity of the operator and imposing arbitrary Dirichlet conditions, independently at each node of the interface, by means of the traces of the finite element functions employed for the discretization inside the subdomain. This leads to parametric subproblems with reduced dimensionality, significantly decreasing the complexity of the involved computations and achieving speed-ups up to 100 times with respect to a previously proposed DD-PGD algorithm that required clustering the interface nodes. A fully algebraic alternating Schwarz method is then formulated to couple the subdomains in the online phase, leveraging the real-time (less than half a second) evaluation capabilities of the computed local surrogate models, that do not require the solution of any additional low-dimensional problems. A computational comparison of different PGD-based local surrogate models is presented using a set of numerical benchmarks to showcase the superior performance of the proposed methodology, both in the offline and in the online phase.The authors acknowledge funding as follows. MD: EPSRC grant EP/V027603/1. BJE: EPSRC Doctoral Training Partner-ship grant EP/W523987/1. MG: Spanish Ministry of Science, Innovation and Universities and Spanish State Research Agency MICIU/AEI/10.13039/501100011033 (Grant No. PID2023-149979OB-I00); Generalitat de Catalunya, Spain (Grant No. 2021-SGR-01049); MG is Fellow of the Serra Húnter Programme of the Generalitat de Catalunya.Peer ReviewedPostprint (published version
Tracing marine litter sources along the Barcelona coastline: Insights from observations and numerical modelling
No full textPlastic debris concentrations in Barcelona coastal waters are among the highest in the Mediterranean Sea, comparable to those observed in subtropical gyres. This study quantifies the marine litter budget and fluxes along the Barcelona coastline using Lagrangian numerical backtracking simulations informed by one year of sampling data (2020–2021) from five urban and two metropolitan area beaches. Sensitivity analyses were conducted to determine optimal simulation parameters, identifying a simulation duration of -28 days and a median time of particles to come from a known source of -26.35 h. These parameters were used to develop a probabilistic module accounting for unresolved nearshore processes. Additional behavioural conditions for this module were derived from the sensitivity assessments. Analysis of beach water marine litter as simulation input revealed multiple pollution hot-spots, linking marine litter sources to known emission points such as combined sewer overflows, marinas, and coastal structures such as breakwaters. Marine litter amounts in urban beach waters reached 1.8 × 109 items km-2 y-1, with simulations indicating that >55% originated from outside the study domain. These findings highlight the Barcelona coastal zone as both a significant emitter and recipient of plastic debris due to regional hydrodynamic connectivity and transport. High levels of plastic pollution highlight the urgent need for upstream waste reduction and targeted mitigation measures to prevent litter from reaching the sea.The present study was developed within the TRAP (EsTRAtegias participativas para la gestión de la contaminación por Plástico del litoral transfronterizo) project (EFA147/03) funded by the POCTEFA Program/Interreg VI-A 2021–2027. Financial support was provided by the Catalan Government Grups de Recerca Consolidats grant (2021 SGR 01195), the ICREA Academia program, and the Surfing for Science projects funded by FECY.Peer ReviewedPostprint (published version
Software for simulation and analysis of far-field diffraction patterns in transient grating spectroscopy
No full textWe present a software package for the simulation and analysis of far-field diffraction patterns in transient grating (TG) spectroscopy. The code is designed to assist both experimental planning and post-processing interpretation by modeling the optical response of TG configurations across a wide range of conditions. It supports input through structured MATLAB variables or Excel-based spreadsheets and provides automated consistency checks and visual output generation. The implementation includes integration over detector pixels, enabling realistic simulations that account for spatial averaging and resolution effects. We demonstrate the software’s capabilities through representative use cases, including the influence of the grating-to-sample distance, the pump-to-probe intensity ratio, and the selection of the division parameter governing pixel integration accuracy. The code is freely available and modular, facilitating its adaptation to different experimental geometries and beam conditions. While full validation is provided elsewhere, this work establishes the core methodology and illustrates the practical value of the tool for TG spectroscopy research.Peer ReviewedPostprint (author's final draft
Flexible body-integrated breathing monitoring system based on near-field coupling printed sensor
No full textBody-integrated sensors have gained increasing attention for their potential to monitor physiological signals unobtrusively in real-time, offering a promising approach for early detection of health changes. This paper introduces an innovative non-contact sensor system designed for unobtrusive monitoring of respiration patterns. The sensor system, comprised of a loop antenna and a split-ring resonator (SRR) tag, accurately detects and distinguishes signals generated by human breathing. Placed in proximity to the diaphragm, the sensors concurrently capture breathing-induced motion and muscle stretch with high precision. The body-worn RF tag is fabricated using inkjet and extrusion printing technologies, which deposit conductive ink onto flexible substrates. The sensor components utilize polyimide for the loop antenna and PET for the SRR tag. The sensor system operates based on near-field electromagnetic coupling between the loop antenna and the SRR tag, detecting changes in resonance frequency induced by breathing motion. Through analysis of near-field coupling, different breathing patterns are analyzed, enabling the identification of subtle and rapid changes in chest movement. To validate the proposed sensor system, a comparative study was conducted using a BIOPAC breathing belt sensor as a reference. Experimental results demonstrate a strong correlation between the measurements obtained from the proposed sensor and those from the BIOPAC system, confirming its accuracy in tracking respiratory motion. The sensor system demonstrates the ability to detect subtle changes in chest motion with a sensitivity of 1.7 MHz/mm. The wireless nature of the proposed system, with a tag area of (50 mm × 50 mm), ensures body-conformable operation and enables unobtrusive and accurate monitoring of respiration patterns in real-time, especially for early respiratory change detection, a key indicator of declining health.Postprint (published version