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Modeling the Impact of CO₂ on Arctic and Antarctic Sea-Ice Volume: A Dynamic Nonlinear Approach
No full textThe year 2024 marked a critical milestone in global warming, with average global temperatures exceeding pre-industrial levels by 1.55°C— the highest on human historyrecords. Polar ice loss, largely attributed to anthropogenic CO₂ emissions has profound social, economic and financial implications that demand rigorous analysis. This study assesses the impact of atmospheric CO₂ on Arctic and Antarctic sea-ice volume usingnonlinear dynamic econometric models. We extend prior sea-ice forecasting models to allow for regime-switching specifications—Threshold Autoregressive (TAR) and Smooth Transition Regressions (STR) models—to capture the complex, nonlinear, and state-dependent responses of the sea-ice to CO₂ concentration changes. Our main contribution is to provide a flexible, reduced-form alternative to general circulation models (GCMs) for evaluating long-run climate scenarios under various emissions trajectories, including IPCC’s Shared Socioeconomic Pathways (SSPs). Results suggest Arctic sea-ice could disappear by 2060 [2045–2078] under a business-as-usual scenario, while Antarctic loss may extend beyond 2100 [2071–2300]. Importantly, models accounting for threshold effects reveal critical recovery tipping points that simpler linear climate models may overlook. Under an intermediate emissions path like SSP2-4.5, a fast recovery of sea-ice volume remains possible if regime shifts are driven by changes in CO₂ growth rates, with estimated tipping points for reversal occurring around 2033 for the Arctic and 2037 for the Antarctic. In contrast, the outlook is less favorable if regime dynamics are determined by CO₂ concentration levels: no recovery is projected for the Arctic, and the Antarctic recovery tipping point is delayed until 2069.Álvaro Escribano acknowledges the funding received from grants PID2022-
151414OB-100 and CEX2021-001181-M funded by MICIU/ AEI/10.13039/501100011033
Socio-Economic Contexts, Status and Political Behaviour in Western Democracies (1964-2019)
Get PDFMención Internacional en el título de doctorPrograma de Doctorado en Ciencias Sociales / Social Sciences por la Universidad Carlos III de MadridPresidenta: Ruth Dassonneville.- Secretaria: Amuitz Garmendia Madariaga.- Vocal: Hanspeter Kries
Microsoft HoloLens 2 vs. Tablet-based Augmented Reality and 3D printing for fronto-orbital reconstruction of craniosynostosis: a case study
No full textBackground
Craniosynostosis is a congenital condition characterized by the premature fusion of cranial sutures, leading to potential complications such as abnormal skull growth, increased intracranial pressure, and cognitive delays. Traditionally, open cranial vault reconstruction (OCVR) has been used to treat this condition. However, it is highly subjective and greatly dependent on the surgeon's expertise, which can lead to residual deformities and the need for reoperation. Effective preoperative planning can greatly improve surgical outcomes, although the major challenge is accurately translating this plan into the clinical setting. Recently, augmented reality (AR) and 3D printing have emerged as promising technologies to facilitate this endeavor. In this work, we propose three alternatives, leveraging these technologies, to guide the precise repositioning of remodeled bone fragments in the patient.
Methods
The three guidance methods are AR on a tablet, AR with Microsoft HoloLens 2, and 3D-printed spacers.
The accuracy of each method was assessed by measuring the deviation of each bone fragment from the virtual surgical plan (VSP) in a simulated environment using 3D-printed phantoms based on a 14-month-old boy with trigonocephaly. The same assessment was also performed during his actual surgery.
Results
All three guidance methods demonstrated similar levels of accuracy, with mean placement errors below 1 mm in all cases. The AR systems allowed for real-time adjustments, enhancing precision. Statistical analysis showed no significant differences in error rates between the different methods or attempts.
Conclusions
Integrating AR and 3D printing into craniosynostosis surgery holds great potential for improving OCVR.
While 3D-printed spacers are useful when digital technologies are unavailable, AR-based methods provide more comprehensive guidance. Nevertheless, our study suggests that the choice may depend more on the specific clinical context, user-specific skills, and available resources rather than on a clear superiority of one method over the others.This research was supported by projects PI22/00601 and AC20/00102 PerPlanRT (Ministerio de Ciencia, Innovación y Universidades, Instituto de Salud Carlos III, Asociación Española Contra el Cáncer and European Regional Development Fund ''Una manera de hacer Europa'', ERA PerMed) and projects TED2021-129392B-I00 and TED2021-132200B-I00 (MCIN/AEI/https://doi.org/10.13039/501100011033 and European Union' NextGeneration/PRTR), and project MAGERIT-CM TEC-2024/COM-44 (Comunidad de Madrid)
Deterministic Fabrication of Fluorescent Nanostructures Featuring Distinct Optical Transitions
No full textThe precise and deterministic integration of fluorescent emitters with photonic nanostructures is an important challenge in nanophotonics and key to the realization of hybrid photonic systems, supporting effects such as emission enhancement, directional emission, and strong coupling. Such integration typically requires the definition or immobilization of the emitters at defined positions with nanoscale precision. While various methods were already developed for creating localized emitters, in this work we present a new method for the deterministic fabrication of fluorescent nanostructures featuring well-defined optical transitions; it works with a minimal amount of steps and is scalable. Specifically, electron-beam lithography is used to directly pattern a mixture of the negative-tone electron-beam resist with the europium complex Eu(TTA)3, which exhibits both electric and magnetic dipolar transitions. Crucially, the lithography process enables precise control over the shape and position of the resulting fluorescent structures with a feature size of approx. 100 (Formula presented.) (Formula presented.). We demonstrate that the Eu(TTA)3 remains fluorescent after exposure, confirming that the electron beam does not alter the structure the optical transitions. This work supports the experimental study of local density of optical states in nanophotonics. It also expands the knowledge base of fluorescent polymer materials, which can have applications in polymer-based photonic devices. Altogether, the presented fabrication method opens the door for the realization of hybrid nanophotonic systems incorporating fluorescent emitters for light-emitting dielectric metasurfaces.This research was funded by the Deutsche Forschungsgemeinschaft (DFG), IRTG 2675 Meta-Active, 437527638. A.B. gratefully acknowledges financial support from the Spanish national project No. PID2022-137857NA-I00. A.B. thanks MICINN for the Ramon y Cajal Fellowship (grant No. RYC2021-030880-I)
Interval Observer for Vehicle Sideslip Angle Estimation Using Extended Kalman Filters
Get PDFAccurate estimation of the vehicle sideslip angle is critical for the effective operation of advanced driver assistance systems and active safety functions such as electronic stability control. However, direct measurement of sideslip angle is impractical in series-production vehicles due to high sensor cost. Furthermore, existing estimation methods often neglect the impact of model uncertainties on estimation error, which can compromise estimation reliability and, consequently, vehicle stability. To address these limitations, this paper proposes an interval observer based on a Kalman filter that accounts explicitly for model uncertainties in the sideslip angle estimation process. The proposed method generates both upper and lower bounds of the estimated sideslip angle, providing a quantifiable measure of uncertainty that enhances the robustness of control systems that depend on this measurement. Given the limitations of simplified vehicle models, a combined vehicle roll and lateral dynamics model is utilized to improve estimation accuracy. The effectiveness of the proposed methodology is demonstrated through a series of simulation experiments conducted using CarSim.This work was supported in part by UC3M’s grants for young doctors (Grant No. 2024/00741/001) and by the grant [PID2022-136468OB-I00] funded by MCIN/AEI/10.13039/501100011033, and by “ERDF A way of making Europe”
Analysis of the linear and nonlinear stability of Alfven eigenmodes and fish-bones in JET DT discharges: mode identification and shear flows generation
Get PDFThe plasma in future nuclear fusion reactors will be heated by neutral beam injectors (NBIs) and high frequency electromagnetic waves as well as fusion born alpha particles. Energetic particles (EPs), with energies up to two orders of magnitude larger than the thermal plasma, can trigger EP driven modes and induce harmful EP losses, reducing the plasma heating efficiency and the economical viability of the reactor. The present study is dedicated to analyze the Alfven Eigenmode (AE) activity in JET D–T discharges, the closest experiment to reactor-like operation performed until now. There, EP driven modes are induced by the combined effect of tangential NBIs and ion cyclotron resonance heating (ICRH) driven EP. Linear and nonlinear simulations are performed with the gyro-fluid FAR3d code to analyze the AE activity observed in the discharge 99896. The linear simulations reproduce the unstable n = 3 to 5 toroidal AEs (TAE) at the inner plasma region observed in the experiment, triggered by highly energetic passing deuterium populations injected by the tangential NBIs, further accelerated by the effect of the ICRH up to 1 MeV. In addition, fish-bones triggered by energetic trapped hydrogen induced by the ICRH are also reproduced. On the other hand, the alpha particles density is too small to destabilize AEs in the experiment. Nonetheless, increasing artificially the alpha density by one order of magnitude, an n = 1 beta induced AE can be destabilized in the inner plasma region. Nonlinear simulations indicate the generation of zonal structures during the AE/fish-bone saturation phase. TAE and fish-bones causes a rather weak increase of the passing D and trapped H EP (around 2%), respectively. Shear flows and zonal currents are generated during the saturation of TAE and fish-bones. Nonlinear simulations performed for D–T and pure deuterium thermal plasma indicate AE/fish-bone activity is weaker and shear flows are less intense in the pure deuterium case, trends consistent with the experimental observations that also indicates a deterioration of the thermal plasma confinement. Therefore, both numerical studies and experimental evidence indicate the generation of shear flows by AE/fish-bones could be connected with an improvement of the thermal plasma confinement.The authors would like to thank the JET technical staff for their contributions in the operation and maintenance of JET. We also thanks Alex Tinguely for very productive discussions about TAE-EAE damping rates in JET plasma. This work was supported by the EUROfusion Project CfP-FSD-AWP23-TE-04-JET, the US DOE under Grant DE-FG02-04ER54742, Comunidad de Madrid under the Project 2019-T1/AMB-13648 and the Spanish National Research Project No. PID2022-137869OB-I00. Data available on request from the authors. This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200–EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. Use has been made of Uranus, a supercomputed cluster located at the Universidad Carlos III de Madrid (Spain) and funded jointly by EU FEDER funds and by the Spanish Government via national Projects UNC313-4E-23612, ENE2009-12213-C03-03, ENE2012-33219, ENE2012-31753 and ENE2015-68265
Effect of Biot number on the thermocline evolution of a packed bed TES system
Get PDFThermal Energy Storage systems are becoming of paramount importance in the context of an efficient and sustainable energy use utilization. These systems are particularly attractive for Concentrated Solar Power plants where the energy surplus is stored as heat and dispatched when solar radiation is insufficient to drive the power block. Among the different storage alternatives, sensible heat storage in granular media is widely used but strongly affected by the behaviour of the thermocline, which directly depends on the particle Biot number. The effect of the Biot number on the thermocline performance of a packed bed Thermal Energy Storage system of sensible heat based on granular material is analysed through particle resolved simulations and an analytical model of a bed of particles. The models used for analysing this kind of systems usually neglect intraparticle conduction. This simplifies the solution of the numerical models and it is a reasonable assumption provided a small enough Biot number. Nonetheless, certain combinations of particle properties and operating conditions might promote non-negligible intraparticle conduction (viz. a sufficiently high Biot number) being required to be considered. Particle Resolved Simulations are required to analyse the coupled problem of the fluid percolating through the particle voids and the heat transfer both inside the particles and from its surface to the fluid. The main novelty of the work is the coupled analysis using two different modelling approaches of packed bed Thermal Energy Storage systems and, more particularly, the successful modelling of the Particle Resolved Simulations. The results indicate a great variation of the thermocline thickness when the Biot number changes, penalizing its performance when the thickness grows. This increase is observed not only when the Biot number augments but also when the Biot number approaches 0, showing an optimum behaviour in a range of Biot numbers, roughly, from 0.1 to 1.5.The authors gratefully acknowledge the financial support provided by the Spanish Government under the project STORESOL, reference number PID2019-109224RA-100. The authors also acknowledge the Multiannual Agreement with UC3M from the Madrid Government (Comunidad de Madrid) in the line of “Fostering Young Doctors Research” (NANOSOLREC-CM-UC3M)
Mathematical Dimensional Synthesis of Four-Bar Linkages Based on Cognate Mechanisms
No full textIn the field of mechanical engineering, understanding mechanisms is essential for designing and developing devices and systems. Mechanisms, composed of interconnected elements, transform the energy applied to the input link into motion or force in the output link. Mechanisms are found in a wide variety of machines, from industrial machines to household machines. In this paper, a mechanism synthesis method is developed that can model four-bar linkages and build their cognate mechanisms to be able to select the mechanism that best suits the required work. Studying four-bar mechanisms offers a strong foundation for grasping more complex mechanical systems. The concepts and principles learned from four-bar mechanisms are widely applicable to advanced mechanical systems, making them a crucial starting point in mechanical engineering education and research. The mechanism synthesis method proposed in this article is organized into three main sections. The first section provides a comprehensive overview of the theoretical and mathematical foundations required for modeling mechanisms, laying the groundwork for understanding the subsequent calculations. The second section delves into the process of obtaining and analyzing the initial mechanism and constructing cognate mechanisms, detailing the procedures and algorithms used for modeling and calculating the coupling curve. Finally, the third section discusses the practical implementation of the method, including the graphical representation of mechanisms and a comparative analysis of the solutions obtained, assessing dimensional differences, design and manufacturing efficiency, and their suitability for various practical applications. The proposed four-bar mechanism synthesis method serves as a valuable tool for mechanism design, offering versatile and adaptable solutions that can optimize both technical performance and economic viability across a wide range of engineering applications
Politics in the facebook era. Evidence from the 2016 US presidential elections
Get PDFSocial media allow political campaigns to reach specific groups of voters with unprecedented precision, yet the effect on voting behaviour of this political micro-targeting is still uncertain. To identify this effect we match survey data with a novel indicator of Facebook political ads intensity, based on audience-specific ad prices and collected during the 2016 US presidential campaign. We find that being exposed to Facebook micro-targeted ads reduced the likelihood of persuading Democrat respondents to cast the ballot in favour of the Democrat candidate and, on the other hand, it increased the likelihood of persuading Republicans and residents of traditionally red or swing states to switch their vote in favour of Mr Trump. A counterfactual analysis exercise exploring the effect on voter mobilisation and persuasion of varying the intensity of political campaigning on Facebook confirms that Trump was the primary beneficiary of micro-targeted ad campaigns on Facebook
Anomalous dynamic scaling of Ising interfaces
Get PDFUntil very recently, the asymptotic occurrence of intrinsic anomalous scaling has been expected to require concomitant effects for kinetically rough interfaces, like quenched disorder or morphological instabilities. However, counterexamples have been recently reported for simpler situations dominated by time-dependent noise, as in the discrete growth system associated with an Ising model proposed by Dashti-Naserabadi et al (2019 Phys. Rev. E 100, 060101(R)), who assessed the equilibrium behaviour of the model. Here, we revisit this system to characterise its time-dependent behaviour in two and three dimensions (one- and two-dimensional interfaces, respectively). While the 3D case seems dominated by a fast evolution beyond critical dynamics, in the 2D case, numerical simulations of an associated time-dependent Ginzburg–Landau equation retrieve the same static (roughness) exponents and the same intrinsic anomalous scaling ansatz as in the equilibrium case throughout the complete time evolution. However, the dynamic exponent is seen to cross over between two different values, none of which enables identification with previously known universality classes of kinetic roughening. Moreover, simulations for larger system sizes suggest a breakdown of scaling behaviour at the largest scales, suggesting that the previously reported scaling behaviour may be effective and restricted to relatively small systems.Part of our numerical simulations were done in Uranus, a supercomputer cluster located at Universidad Carlos III de Madrid and funded jointly by EU-FEDER and the Spanish Government via Grants No. UNC313-4E-2361, No. ENE2009-12213-C03-03, No. ENE2012-33219, and No. ENE2015-68265, and via Grant No. SIMTURB-CM-UC3M from the Convenio Plurianual of Comunidad de Madrid (CAM, Spain). In addition, this work has been partially supported by Ministerio de Ciencia e Innovación (Spain), by Agencia Estatal de Investigación (AEI, Spain, 10.13039/501100011033), and by European Regional Development Fund (ERDF, A way of making Europe) through Grants No. PGC2018-094763-B-I00, No. PID2022-140217NB-I00, and No. PID2021-123969NB-I00, and by CAM (Spain) under the Multiannual Agreements with UC3M in the line of Excellence of University Professors (EPUC3M14 and EPUC3M23), in the context of the V Plan Regional de Investigación Científica e Innovación Tecnológica (PRICIT). E. R.-F. acknowledges financial support from CAM through contract No. 2022/018 under the EPUC3M23 line and from Universidad Carlos III de Madrid through the Margarita Salas program