9,510 results on '"Prodan A"'
Search Results
2. GHRL, LEP, LEPR genes polymorphism and their association with the metabolic syndrome in the Ukrainian population
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Prodan Andrii, Dzubanovsky Ihor, Kamyshnyi Oleksandr, Melnyk Natalia, Pidruchna Svitlana, and Voloshyn Stanislava
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metabolic syndrome ,lepr ,lep ,ghrl gene polymorphism ,adiponectin ,resistin ,ghrelin ,leptin ,Diseases of the endocrine glands. Clinical endocrinology ,RC648-665 - Abstract
Objective. Many conflicting results have been obtained in the study of leptin (LEP) and leptin receptor (LEPR) gene variants that are associated with the obesity and diabetes possibly due to differences in the study populations. The aim of this study was to evaluate changes in the metabolic hormones (leptin, ghrelin, adiponectin, resistin) levels in the blood of obese patients in relation to the GHRL (rs696217), LEP (rs7799039), LEPR (rs1137100, rs1137101, rs1805094) polymorphism in Ukrainian population.
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- 2023
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3. Reducing real-time complexity via sub-control Lyapunov functions: from theory to experiments
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Do, Huu-Thinh, Blanchini, Franco, Miani, Stefano, and Prodan, Ionela
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Electrical Engineering and Systems Science - Systems and Control ,Mathematics - Optimization and Control - Abstract
The techniques to design control Lyapunov functions (CLF), along with a proper stabilizing feedback, possibly in the presence of constraints, often provide control laws that are too complex for proper implementation online, especially when an optimization problem is involved. In this work, we show how to acquire an alternative, computationally attractive feedback. Given a nominal CLF and a nominal state feedback, we say that a different positive definite function is a Sub-control Lyapunov function (SCLF) if its Lyapunov derivative is negative-definite and bounded above by the Lyapunov derivative of the nominal function with the nominal control. It turns out that if we consider a family of basis functions, then a SCLF can be computed by linear programming, with an infinite number of constraints. The idea is that although the offline computational burden to achieve the new controller and solve the linear program is considerable, the online computational burden is drastically reduced. Comprehensive simulations and experiments on drone control are conducted to demonstrate the effectiveness of the study.
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- 2025
4. Magnetism and electronic dynamics in $CuCr_{2-x}Sn_xS_4$ spinels studied by transferred hyperfine fields at $^{119}Sn$ and muon spin rotation and relaxation
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Sadrollahi, Elaheh, Medrano, Cynthia P. C., Heringer, Magno A. V., Saitovitch, E. M. Baggio, Prodan, Lilian, Tsurkan, Vladimir, and Litterst, F. Jochen
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Condensed Matter - Strongly Correlated Electrons - Abstract
We investigated magnetization, muon spin rotation ($\mu$SR), and $^{119}Sn$ M\"{o}ssbauer spectroscopy on Sn substituted $CuCr_{2-x}Sn_xS_4$ (x=0.03 and 0.08) spinel compounds. The magnetization and $\mu$SR results reveal similar additional low-temperature magnetic transitions around 80 K and 40 K as found for the undoped material, indicating a magnetic ground state deviating from a simple collinear ferromagnet. The observed changes in the M\"{o}ssbauer hyperfine spectra are less pronounced and are discussed in view of the different positions of the local probes $\mu^+$ and $^{119}Sn$ and their different magnetic coupling to the magnetic Cr lattice. Above 80 K, both $\mu$SR and M\"{o}ssbauer spectra show temperature-dependent inhomogeneous broadening either due to structural or charge disorder and changing spin dynamics that can be related to a precursor magnetic phase above the well-defined static low-temperature phase., Comment: 15 pages, 13 figures
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- 2025
5. Strain engineering of magnetic anisotropy in the kagome magnet Fe3Sn2
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Kong, D., Kovács, A., Charilaou, M., Altthaler, M., Prodan, L., Tsuran, V., Meier, D., Han, X., Kezsmarki, I, and Dunin-Borkowski, R. E.
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Condensed Matter - Materials Science - Abstract
The ability to control magnetism with strain offers innovative pathways for the modulation of magnetic domain configurations and for the manipulation of magnetic states in materials on the nanoscale. Although the effect of strain on magnetic domains has been recognized since the early work of C. Kittel, detailed local observations have been elusive. Here, we use mechanical strain to achieve reversible control of magnetic textures in a kagome-type Fe3Sn2 ferromagnet without the use of an external electric current or magnetic field in situ in a transmission electron microscope at room temperature. We use Fresnel defocus imaging, off-axis electron holography and micromagnetic simulations to show that tensile strain modifies the structures of dipolar skyrmions and switches their magnetization between out-of-plane and in-plane configurations. We also present quantitative measurements of magnetic domain wall structures and their transformations as a function of strain. Our results demonstrate the fundamental importance of anisotropy effects and their interplay with magnetoelastic and magnetocrystalline energies, providing new opportunities for the development of strain-controlled devices for spintronic applications., Comment: 10 pages, 5 figures
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- 2024
6. Topological Dynamics of Synthetic Molecules
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Zhu, Yuming and Prodan, Emil
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Mathematical Physics ,Condensed Matter - Materials Science - Abstract
We study the dynamics of synthetic molecules whose architectures are generated by space transformations from a point group acting on seed resonators. We show that the dynamical matrix of any such molecule can be reproduced as the left regular representation of a self-adjoint element from the stabilized group's algebra. Furthermore, we use elements of representation theory and K-theory to rationalize the dynamical features supported by such synthetic molecules up to topological equivalences. These tools enable us to identify a set of fundamental models which generate by superposition all possible dynamical matrices up to homotopy equivalences. Interpolations between these fundamental models give rise to topological spectral flows.
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- 2024
7. A space-adiabatic approach for bulk-defect correspondences in lattice models of topological insulators
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Ojito, Danilo Polo, Prodan, Emil, and Stoiber, Tom
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Mathematical Physics - Abstract
In space-adiabatic approaches one can approximate Hamiltonians that are modulated slowly in space by phase-space functions that depend on position and momentum. In this paper, we establish a rigorous relation between this approach and the operator-theoretic approach for topological insulators with defects, which employs $C^*$-algebras and operator K-theory. Using such tools, we show that by quantizing phase-space functions one can construct lattice Hamiltonians which are gapped at certain spatial limits and carry protected states at defects such as boundaries, hinges, and corners. Moreover, we show that the topological invariants that protect the latter can be computed in terms of the symbol functions. This enables us to compute boundary maps in K-theory that are relevant for bulk-defect correspondences., Comment: 39 pages, 3 figures
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- 2024
8. Magnon-phonon interactions in the spinel compound MnSc$_2$Se$_4$
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Sourd, J., Skourski, Y., Prodan, L., Tsurkan, V., Miyata, A., Wosnitza, J., and Zherlitsyn, S.
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Condensed Matter - Strongly Correlated Electrons - Abstract
We investigated the magnetic and magnetoelastic properties of MnSc$_2$Se$_4$ single crystals at low temperature under a magnetic field directed along the crystallographic [111] axis. The magnetization data at low temperature show a linear increase with magnetic field, until saturation is reached above 15 T. In ultrasound, a longitudinal acoustic mode shows a softening in field, which is absent for a transverse acoustic mode. We discuss these results using a microscopic model based on the framework of linear spin-wave theory. The magnetic and magnetoelastic data are qualitatively reproduced by considering magnon-phonon interactions arising from exchange-striction coupling between the crystal lattice and spin-wave fluctuations in the zero-temperature limit.
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- 2024
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9. Cutting Through the Confusion and Hype: Understanding the True Potential of Generative AI
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Prodan, Ante, Occhipinti, Jo-An, Ahlip, Rehez, Ujdur, Goran, Eyre, Harris A., Goosen, Kyle, Penza, Luke, and Heffernan, Mark
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Computer Science - Computers and Society ,Computer Science - Information Retrieval ,Computer Science - Multiagent Systems - Abstract
This paper explores the nuanced landscape of generative AI (genAI), particularly focusing on neural network-based models like Large Language Models (LLMs). While genAI garners both optimistic enthusiasm and sceptical criticism, this work seeks to provide a balanced examination of its capabilities, limitations, and the profound impact it may have on societal functions and personal interactions. The first section demystifies language-based genAI through detailed discussions on how LLMs learn, their computational needs, distinguishing features from supporting technologies, and the inherent limitations in their accuracy and reliability. Real-world examples illustrate the practical applications and implications of these technologies. The latter part of the paper adopts a systems perspective, evaluating how the integration of LLMs with existing technologies can enhance productivity and address emerging concerns. It highlights the need for significant investment to understand the implications of recent advancements, advocating for a well-informed dialogue to ethically and responsibly integrate genAI into diverse sectors. The paper concludes with prospective developments and recommendations, emphasizing a forward-looking approach to harnessing genAI`s potential while mitigating its risks.
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- 2024
10. Terahertz resonant emission by optically excited infrared-active shear phonons in KY(MoO4)2
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Kamenskyi, D., Vasin, K., Prodan, L., Kutko, K., Khrustalyov, V., Pavlov, S. G., and Hübers, H. -W.
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Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons ,Physics - Optics - Abstract
Generation of the monochromatic electromagnetic radiation in the terahertz (THz) range of frequencies for many decades remanes a chellenging task. Here we demonstrate the emission of monochromatic sub-THz radiation by coherent optical phonons in dielectric material KY(MoO4)2. The layered crystal structure of KY(MoO4)2 leads to infrared-active shear lattice vibrations with energies below 3.7 meV, which corresponds to the frequencies low than 900 GHz where solid-state compounds based monochromatic radiation sources are rare. Coherent infrared-active optical phonons are excited by broadband THz pulses lasting for tens of picoseconds and re-emit narrow-band subTHz radiation pulses with a decay time of 33 picoseconds, which is exceptionally long for the oscillators with frequencies below 1 THz. Such a long coherent emission allows for the detection of more than 50 periods of radiation with frequencies of 568 and 860 GHz. The remarkably long decay time together with the chemical stability of the employed materials suggest a variety of possible applications in THz laser technology.
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- 2024
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11. A machine learning framework to generate star cluster realisations
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Prodan, George P., Pasquato, Mario, Iorio, Giuliano, Ballone, Alessandro, Torniamenti, Stefano, Di Carlo, Ugo Niccolò, and Mapelli, Michela
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Astrophysics - Astrophysics of Galaxies - Abstract
Context. Computational astronomy has reached the stage where running a gravitational N-body simulation of a stellar system, such as a Milky Way star cluster, is computationally feasible, but a major limiting factor that remains is the ability to set up physically realistic initial conditions. Aims. We aim to obtain realistic initial conditions for N-body simulations by taking advantage of machine learning, with emphasis on reproducing small-scale interstellar distance distributions. Methods. The computational bottleneck for obtaining such distance distributions is the hydrodynamics of star formation, which ultimately determine the features of the stars, including positions, velocities, and masses. To mitigate this issue, we introduce a new method for sampling physically realistic initial conditions from a limited set of simulations using Gaussian processes. Results. We evaluated the resulting sets of initial conditions based on whether they meet tests for physical realism. We find that direct sampling based on the learned distribution of the star features fails to reproduce binary systems. Consequently, we show that physics-informed sampling algorithms solve this issue, as they are capable of generating realisations closer to reality., Comment: Accepted to A&A (4th Sep 2024)
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- 2024
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12. C*-framework for higher-order bulk-boundary correspondences
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Ojito, Danilo Polo, Prodan, Emil, and Stoiber, Tom
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Mathematical Physics ,Condensed Matter - Strongly Correlated Electrons ,Mathematics - K-Theory and Homology ,Mathematics - Operator Algebras - Abstract
A typical crystal is a finite piece of a material which may be invariant under some point symmetry group. If it is a so-called intrinsic higher-order topological insulator or superconductor, then it displays boundary modes at hinges or corners protected by the crystalline symmetry and the bulk topology. We explain the mechanism behind such phenomena using operator K-theory. Specifically, we derive a groupoid C*-algebra that 1) encodes the dynamics of the electrons in the infinite size limit of a crystal; 2) remembers the boundary conditions at the crystal's boundaries, and 3) admits a natural action by the point symmetries of the atomic lattice. The filtrations of the groupoid's unit space by closed subsets that are invariant under the groupoid and point group actions supply equivariant cofiltrations of the groupoid C*-algebra. We show that specific derivations of the induced spectral sequences in twisted equivariant K-theories enumerate all non-trivial higher-order bulk-boundary correspondences., Comment: Classification for four geometries/symmetries fully worked out
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- 2024
13. Towards AI-Assisted Sustainable Adaptive Video Streaming Systems: Tutorial and Survey
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Farahani, Reza, Azimi, Zoha, Timmerer, Christian, and Prodan, Radu
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Computer Science - Multimedia - Abstract
Improvements in networking technologies and the steadily increasing numbers of users, as well as the shift from traditional broadcasting to streaming content over the Internet, have made video applications (e.g., live and Video-on-Demand (VoD)) predominant sources of traffic. Recent advances in Artificial Intelligence (AI) and its widespread application in various academic and industrial fields have focused on designing and implementing a variety of video compression and content delivery techniques to improve user Quality of Experience (QoE). However, providing high QoE services results in more energy consumption and carbon footprint across the service delivery path, extending from the end user's device through the network and service infrastructure (e.g., cloud providers). Despite the importance of energy efficiency in video streaming, there is a lack of comprehensive surveys covering state-of-the-art AI techniques and their applications throughout the video streaming lifecycle. Existing surveys typically focus on specific parts, such as video encoding, delivery networks, playback, or quality assessment, without providing a holistic view of the entire lifecycle and its impact on energy consumption and QoE. Motivated by this research gap, this survey provides a comprehensive overview of the video streaming lifecycle, content delivery, energy and Video Quality Assessment (VQA) metrics and models, and AI techniques employed in video streaming. In addition, it conducts an in-depth state-of-the-art analysis focused on AI-driven approaches to enhance the energy efficiency of end-to-end aspects of video streaming systems (i.e., encoding, delivery network, playback, and VQA approaches). Finally, it discusses prospective research directions for developing AI-assisted energy-aware video streaming systems., Comment: 33 pages, 7 figures, 6 Tables, Journal paper
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- 2024
14. Optical magnetoelectric effect in the polar honeycomb antiferromagnet Fe2Mo3O8
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Vasin, K. V., Strinic, A., Schilberth, F., Reschke, S., Prodan, L., Tsurkan, V., Nurmukhametov, A. R., Eremin, M. V., Kezsmarki, I., and Deisenhofer, J.
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Condensed Matter - Strongly Correlated Electrons - Abstract
The lack of both time-reversal and spatial inversion symmetry in polar magnets is a prerequisite for the occurrence of optical magnetoelectric effects such as nonreciprocal directional dichroism with the potential for the realization of optical diodes. In particular, antiferromagnetic materials with magnetic excitations in the THz range such as Fe2Mo3O8 are promising candidates for next-generation spintronic applications. In a combined experimental and theoretical effort we investigated the THz excitations of the polar honeycomb antiferromagnet Fe2Mo3O8 in external magnetic fields and their nonreciprocal directional dichroism, together with the temperature dependence of the electronic transitions in the mid- and near-infrared frequency range. Using an advanced single-ion approach for the Fe ions, we are able to describe optical excitations from the THz to the near-infrared frequency range quantitatively and successfully model the observed nonreciprocal directional dichroism in the THz regime.
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- 2024
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15. On the constrained feedback linearization control based on the MILP representation of a ReLU-ANN
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Do, Huu-Thinh and Prodan, Ionela
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Electrical Engineering and Systems Science - Systems and Control - Abstract
In this work, we explore the efficacy of rectified linear unit artificial neural networks in addressing the intricate challenges of convoluted constraints arising from feedback linearization mapping. Our approach involves a comprehensive procedure, encompassing the approximation of constraints through a regression process. Subsequently, we transform these constraints into an equivalent representation of mixed-integer linear constraints, seamlessly integrating them into other stabilizing control architectures. The advantage resides in the compatibility with the linear control design and the constraint satisfaction in the model predictive control setup, even for forecasted trajectories. Simulations are provided to validate the proposed constraint reformulation.
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- 2024
16. Detecting early stages of Alzheimer’s disease using a web-based cognitive battery
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Hoffmeister, Jordan R., Robison, Brady R., Copeland, Christopher T., Prodan, Calin I., Scott, Jim G., and Glenn, Jordan M.
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- 2024
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17. Linking peripheral atherosclerosis to blood–brain barrier disruption: elucidating its role as a manifestation of cerebral small vessel disease in vascular cognitive impairment
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Nyúl-Tóth, Ádám, Patai, Roland, Csiszar, Anna, Ungvari, Anna, Gulej, Rafal, Mukli, Peter, Yabluchanskiy, Andriy, Benyo, Zoltan, Sotonyi, Peter, Prodan, Calin I., Liotta, Eric M., Toth, Peter, Elahi, Fanny, Barsi, Péter, Maurovich-Horvat, Pál, Sorond, Farzaneh A., Tarantini, Stefano, and Ungvari, Zoltan
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- 2024
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18. Development and characterization of PLA food packaging composite
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Moldovan, Andrei, Sarosi, Ioan, Cuc, Stanca, Prodan, Doina, Taut, Adrian Catalin, Petean, Ioan, Bombos, Dorin, Doukeh, Rami, Nemes, Ovidiu, and Man, Sorin Claudiu
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- 2024
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19. Cloud storage tier optimization through storage object classification
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Khan, Akif Quddus, Matskin, Mihhail, Prodan, Radu, Bussler, Christoph, Roman, Dumitru, and Soylu, Ahmet
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- 2024
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20. StoreLess: Serverless Workflow Scheduling with Federated Storage in Sky Computing
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Ristov, Sashko, Hautz, Mika, Gritsch, Philipp, Nastic, Stefan, Prodan, Radu, Felderer, Michael, Goos, Gerhard, Series Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Gaaloul, Walid, editor, Sheng, Michael, editor, Yu, Qi, editor, and Yangui, Sami, editor
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- 2025
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21. In the Shadow of Smith`s Invisible Hand: Risks to Economic Stability and Social Wellbeing in the Age of Intelligence
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Occhipinti, Jo-An, Hynes, William, Prodan, Ante, Eyre, Harris A., Green, Roy, Burrow, Sharan, Tanner, Marcel, Buchanan, John, Ujdur, Goran, Destrebecq, Frederic, Song, Christine, Carnevale, Steven, Hickie, Ian B., and Heffernan, Mark
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Computer Science - Computers and Society ,Computer Science - Artificial Intelligence ,Economics - General Economics - Abstract
Work is fundamental to societal prosperity and mental health, providing financial security, identity, purpose, and social integration. The emergence of generative artificial intelligence (AI) has catalysed debate on job displacement. Some argue that many new jobs and industries will emerge to offset the displacement, while others foresee a widespread decoupling of economic productivity from human input threatening jobs on an unprecedented scale. This study explores the conditions under which both may be true and examines the potential for a self-reinforcing cycle of recessionary pressures that would necessitate sustained government intervention to maintain job security and economic stability. A system dynamics model was developed to undertake ex ante analysis of the effect of AI-capital deepening on labour underutilisation and demand in the economy. Results indicate that even a moderate increase in the AI-capital-to-labour ratio could increase labour underutilisation to double its current level, decrease per capita disposable income by 26% (95% interval, 20.6% - 31.8%), and decrease the consumption index by 21% (95% interval, 13.6% - 28.3%) by mid-2050. To prevent a reduction in per capita disposable income due to the estimated increase in underutilization, at least a 10.8-fold increase in the new job creation rate would be necessary. Results demonstrate the feasibility of an AI-capital- to-labour ratio threshold beyond which even high rates of new job creation cannot prevent declines in consumption. The precise threshold will vary across economies, emphasizing the urgent need for empirical research tailored to specific contexts. This study underscores the need for governments, civic organisations, and business to work together to ensure a smooth transition to an AI- dominated economy to safeguard the Mental Wealth of nations., Comment: 10 pages, 5 figures, 1 table, an Appendix
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- 2024
22. Optical anisotropy of the kagome magnet FeSn: Dominant role of excitations between kagome and Sn layers
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Ebad-Allah, J., Jiang, M. -C., Borkenhagen, R., Meggle, F., Prodan, L., Tsurkan, V., Schilberth, F., Guo, G. -Y., Arita, R., Kézsmárki, I., and Kuntscher, C. A.
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Condensed Matter - Materials Science - Abstract
Antiferromagnetic FeSn is considered to be a close realization of the ideal two-dimensional (2D) kagome lattice, hosting Dirac cones, van Hove singularities, and flat bands, as it comprises Fe$_3$Sn kagome layers well separated by Sn buffer layers. We observe a pronounced optical anisotropy, with the low-energy optical conductivity being surprisingly higher perpendicular to the kagome planes than along the layers. This finding contradicts the prevalent picture of dominantly 2D electronic structure for FeSn. Our material-specific theory reproduces the measured conductivity spectra remarkarbly well. A site-specific decomposition of the optical response to individual excitation channels shows that the optical conductivity for polarizations both parallel and perpendicular to the kagome plane is dominated by interlayer transitions between kagome layers and adjacent Sn-based layers. Moreover, the matrix elements corresponding to these transitions are highly anisotropic, leading to larger out-of-plane conductivity. Our results evidence the crucial role of interstitial layers in charge dynamics even in seemingly 2D systems., Comment: 7 pages, 2 figures. Accepted for publication in Phys. Rev. B
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- 2024
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23. The recessionary pressures of generative AI: A threat to wellbeing
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Occhipinti, Jo-An, Prodan, Ante, Hynes, William, Green, Roy, Burrow, Sharan, Eyre, Harris A, Skinner, Adam, Ujdur, Goran, Buchanan, John, Hickie, Ian B, Heffernan, Mark, Song, Christine, and Tanner, Marcel
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Computer Science - Computers and Society - Abstract
Generative Artificial Intelligence (AI) stands as a transformative force that presents a paradox; it offers unprecedented opportunities for productivity growth while potentially posing significant threats to economic stability and societal wellbeing. Many consider generative AI as akin to previous technological advancements, using historical precedent to argue that fears of widespread job displacement are unfounded, while others contend that generative AI`s unique capacity to undertake non-routine cognitive tasks sets it apart from other forms of automation capital and presents a threat to the quality and availability of work that underpin stable societies. This paper explores the conditions under which both may be true. We posit the existence of an AI-capital-to-labour ratio threshold beyond which a self-reinforcing cycle of recessionary pressures could be triggered, exacerbating social disparities, reducing social cohesion, heightening tensions, and requiring sustained government intervention to maintain stability. To prevent this, the paper underscores the urgent need for proactive policy responses, making recommendations to reduce these risks through robust regulatory frameworks and a new social contract characterised by progressive social and economic policies. This approach aims to ensure a sustainable, inclusive, and resilient economic future where human contribution to the economy is retained and integrated with generative AI to enhance the Mental Wealth of nations., Comment: 7 pages, 3 figures
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- 2024
24. ANN-Based Adaptive NMPC for Uranium Extraction-Scrubbing Operation in Spent Nuclear Fuel Treatment Process
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Vo, Duc-Tri, Prodan, Ionela, Lefèvre, Laurent, Vanel, Vincent, Costenoble, Sylvain, and Dinh, Binh
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Electrical Engineering and Systems Science - Systems and Control - Abstract
This paper addresses the particularities in optimal control of the uranium extraction-scrubbing operation in the PUREX process. The control problem requires optimally stabilizing the system at a desired solvent saturation level, guaranteeing constraints, disturbance rejection, and adapting to set point variations. A qualified simulator named PAREX was developed by the French Alternative Energies and Atomic Energy Commission (CEA) to simulate liquid-liquid extraction operations in the PUREX process. However, since the mathematical model is complex and is described by a system of nonlinear, stiff, high-dimensional differential-algebraic equations (DAE), applying optimal control methods will lead to a large-scale nonlinear programming problem with a huge computational burden. The solution we propose in this work is to train a neural network to predict the process outputs using the measurement history. This neural network architecture, which employs the long short-term memory (LSTM), linear regression and logistic regression networks, allows reducing the number of state variables, thus reducing the complexity of the optimization problems in the control scheme. Furthermore, nonlinear model predictive control (NMPC) and moving horizon estimation (MHE) problems are developed and solved using the PSO (Particle Swarm Optimization) algorithm. Simulation results show that the proposed adaptive optimal control scheme satisfies the requirements of the control problem and provides promise for experimental testing.
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- 2024
25. A $C^\ast$-algebraic view on the interaction of real- and reciprocal space topology in skyrmion crystals
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Prass, Pascal, Lux, Fabian R., Prodan, Emil, van Straten, Duco, and Mokrousov, Yuriy
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Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
Understanding the interaction of real- and reciprocal space topology in skyrmion crystals is an open problem. We approach it from the viewpoint of $C^\ast$-algebras and calculate all admissible Chern numbers of a strongly coupled tight-binding skyrmion system on a triangular lattice as a function of Fermi energy and texture parameters. Our analysis reveals the topological complexity of electronic states coupled to spin textures, and the failure of the adiabatic picture to account for it in terms of emergent electromagnetism. On the contrary, we explain the discontinuous jumps in the real-space winding number in terms of collective evolution in real-, reciprocal, and mixed space Chern numbers. Our work sets the stage for further research on topological dynamics in complex dynamic spin textures coupled to external fields., Comment: 40 pages, 13 figures, Submission to SciPost, resubmission in response to referee
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- 2024
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26. A Stabilizing NMPC Strategy for a Class of Nonholonomic Systems with Drift
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Nguyen, Huu Thien, Fontes, Fernando A. C. C., and Prodan, Ionela
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Mathematics - Optimization and Control - Abstract
In this paper, we present a stabilizing Nonlinear Model Predictive Control (NMPC) scheme tailored for a class of nonholonomic systems with drift, where the acceleration is laterally restrained. Examples include a mobile robot with drifting wheels on a planar surface or a spacecraft maneuvering in a vacuum. The novelty lies in the formulation of the terminal set, reachable from a significant distance from the equilibrium, and the terminal cost, represented as the integration of the stage cost. The proposed approach establishes essential steps for ensuring stability and feasibility guarantees. Simulation results substantiate the viability and effectiveness of the NMPC scheme., Comment: Submitted to an international conference
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- 2024
27. Pre-perihelion Monitoring of Interstellar Comet 2I/Borisov
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Prodan, George P., Popescu, Marcel, Licandro, Javier, Akhlaghi, Mohammad, de León, Julia, Tatsumi, Eri, Pastrav, Bogdan Adrian, Hibbert, Jacob M., Văduvescu, Ovidiu, Simion, Nicolae Gabriel, Pallé, Enric, Narita, Norio, Fukui, Akihiko, and Murgas, Felipe
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Astrophysics - Earth and Planetary Astrophysics - Abstract
The discovery of interstellar comet 2I/Borisov offered the unique opportunity to obtain a detailed analysis of an object coming from another planetary system, and leaving behind material in our interplanetary space. We continuously observed 2I/Borisov between October 3 and December 13, 2019 using the 1.52-m Telescopio Carlos S\'{a}nchez equipped with MuSCAT2 instrument, and the 2.54-m Isaac Newton Telescope with Wide Field Camera. We characterize its morphology and spectro-photometric features using the data gathered during this extended campaign. Simultaneous imaging in four bands ($g$, $r$, $i$, and $z_s$) reveals a homogeneous composition and a reddish hue, resembling Solar System comets, and as well a diffuse profile exhibiting familiar cometary traits. We discern a stationary trend fluctuating around a constant activity level throughout October and November 2019. Subsequently, a reduction in activity is observed in December. Dust production and mass loss calculations indicate approximately an average of 4 kg/s before perihelion, while after perihelion the net mass loss is about 0.6 kg/s. Our simulations indicate the most probable size of coma dust particles should be in the range 200-250 nm, and the terminal speed around 300 m/s. The spectrum acquired with the 4.2-m William Herschel Telescope shows the presence of a strong CN line for which we find a gas production rate of $1.2 \times 10^{24}~s^{-1}$. We also detected NH$_2$ and OI bands. The ratio between NH$_2$ and CN productions is $\log (NH_2/CN) =-0.2$. Overall, this observing campaign provides a new understanding of 2I/Borisov's unique characteristics and activity patterns., Comment: accepted to MNRAS on 12th Feb 2024
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- 2024
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28. PSO-Based Adaptive NMPC for Uranium Extraction-Scrubbing Operation in Spent Nuclear Fuel Treatment Process
- Author
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Vo, Duc-Tri, Prodan, Ionela, Lefèvre, Laurent, Vanel, Vincent, Costenoble, Sylvain, and Dinh, Binh
- Subjects
Electrical Engineering and Systems Science - Systems and Control - Abstract
This paper addresses the particularities of adaptive optimal control of the uranium extraction-scrubbing operation in the PUREX process. The process dynamics are nonlinear, high dimensional, and have limited online measurements. In addition, analysis and developments are based on a qualified simulation program called PAREX, which was validated with laboratory and industrial data. The control objective is to stabilize the process at a desired solvent saturation level, guaranteeing constraints and handling disturbances. The developed control strategy relies on optimization-based methods for computing control inputs and estimates, i.e., Nonlinear Model Predictive Control (NMPC) and Nonlinear Moving Horizon Estimation (NMHE). The designs of these two associated algorithms are tailored for this process's particular dynamics and are implemented through an enhanced Particle Swarm Optimization (PSO) to guarantee constraint satisfaction. Software-in-the-loop simulations using PAREX show that the designed control scheme effectively satisfies control objectives and guarantees constraints during operation.
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- 2024
29. Magnetism of CuCr$_2$X$_4$ (X= S and Se) spinels studied with muon spin rotation and relaxation ($\mu$SR)
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Sadrollahi, Elaheh, Litterst, F. Jochen, Prodan, Lilian, Tsurkan, Vladimir, and Loidl, Alois
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Condensed Matter - Strongly Correlated Electrons - Abstract
We present muon spin rotation and relaxation ($\mu$SR) results for chalcogenide spinels CuCr$_2$X$_4$ with X= S and Se. Both compounds are known as ferromagnetic metals with high Curie temperatures. Our $\mu$SR and magnetization data show clear signatures for additional magnetic transitions far below the respective Curie temperatures. They can be related to changes in the Cr valence system from the mixed valence between Cr$^{3+}$ and Cr$^{4+}$ at high temperatures with collinear ferromagnetism to a charge-ordered state at low temperatures with a different ferromagnetic structure. Our results demonstrate that the electronic systems and the related spin structures of both compounds are more complex than assumed so far., Comment: 17 pages, 10 Figures, experimental results
- Published
- 2024
30. DFARM: a deadline-aware fault-tolerant scheduler for cloud computing
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Awan, Ahmad, Aleem, Muhammad, Hussain, Altaf, and Prodan, Radu
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- 2024
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31. Atherosclerotic burden and cerebral small vessel disease: exploring the link through microvascular aging and cerebral microhemorrhages
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Csiszar, Anna, Ungvari, Anna, Patai, Roland, Gulej, Rafal, Yabluchanskiy, Andriy, Benyo, Zoltan, Kovacs, Illes, Sotonyi, Peter, Kirkpartrick, Angelia C., Prodan, Calin I., Liotta, Eric M., Zhang, Xin A., Toth, Peter, Tarantini, Stefano, Sorond, Farzaneh A., and Ungvari, Zoltan
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- 2024
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32. Numerical Simulation of Performance of Micro Gas Turbine Engine Combustion Chamber Taking into Account Oil Addition to Fuel
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Bulat, P. V., Vokin, L. O., Volkov, K. N., Nikitenko, A. B., Prodan, N. V., and Renev, M. E.
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- 2024
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33. Spectral and Combinatorial Aspects of Cayley-Crystals
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Lux, Fabian R. and Prodan, Emil
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- 2024
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34. Scheduling of Distributed Applications on the Computing Continuum: A Survey
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Mehran, Narges, Kimovski, Dragi, Hellwagner, Hermann, Roman, Dumitru, Soylu, Ahmet, and Prodan, Radu
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Computer Science - Distributed, Parallel, and Cluster Computing - Abstract
The demand for distributed applications has significantly increased over the past decade, with improvements in machine learning techniques fueling this growth. These applications predominantly utilize Cloud data centers for high-performance computing and Fog and Edge devices for low-latency communication for small-size machine learning model training and inference. The challenge of executing applications with different requirements on heterogeneous devices requires effective methods for solving NP-hard resource allocation and application scheduling problems. The state-of-the-art techniques primarily investigate conflicting objectives, such as the completion time, energy consumption, and economic cost of application execution on the Cloud, Fog, and Edge computing infrastructure. Therefore, in this work, we review these research works considering their objectives, methods, and evaluation tools. Based on the review, we provide a discussion on the scheduling methods in the Computing Continuum., Comment: 7 pages, 3 figures, 3 tables
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- 2024
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35. Giant natural optical rotation from chiral electromagnons in a collinear antiferromagnet
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Maluski, D., Langenbach, M., Szaller, D., Reschke, S., Prodan, L., Mayorga, I. Cámara, Cheong, S. -W., Tsurkan, V., Kézsmárki, I., Hemberger, J., and Grüninger, M.
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Condensed Matter - Strongly Correlated Electrons - Abstract
In NiTe$_3$O$_6$ with a chiral crystal structure, we report on a giant natural optical rotation of the lowest-energy magnon. This polarization rotation, as large as 140 deg/mm, corresponds to a path difference between right and left circular polarizations that is comparable to the sample thickness. Natural optical rotation, being a measure of structural chirality, is highly unusual for long-wavelength magnons. The collinear antiferromagnetic order of NiTe$_3$O$_6$ makes this giant effect even more peculiar: Chirality of the crystal structure does not affect the magnetic ground state but is strongly manifested in the lowest excited state. We show that the dynamic magnetoelectric effect, turning this magnon to a magnetic- and electric-dipole active hybrid mode, generates the giant natural optical rotation. In finite magnetic fields, it also leads to a strong optical magnetochiral effect., Comment: 9 pages, 4 figures
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- 2023
36. Content-Adaptive Variable Framerate Encoding Scheme for Green Live Streaming
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Menon, Vignesh V, Afzal, Samira, Rajendran, Prajit T, Schoeffmann, Klaus, Prodan, Radu, and Timmerer, Christian
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Computer Science - Multimedia - Abstract
Adaptive live video streaming applications use a fixed predefined configuration for the bitrate ladder with constant framerate and encoding presets in a session. However, selecting optimized framerates and presets for every bitrate ladder representation can enhance perceptual quality, improve computational resource allocation, and thus, the streaming energy efficiency. In particular, low framerates for low-bitrate representations reduce compression artifacts and decrease encoding energy consumption. In addition, an optimized preset may lead to improved compression efficiency. To this light, this paper proposes a Content-adaptive Variable Framerate (CVFR) encoding scheme, which offers two modes of operation: ecological (ECO) and high-quality (HQ). CVFR-ECO optimizes for the highest encoding energy savings by predicting the optimized framerate for each representation in the bitrate ladder. CVFR-HQ takes it further by predicting each representation's optimized framerate-encoding preset pair using low-complexity discrete cosine transform energy-based spatial and temporal features for compression efficiency and sustainable storage. We demonstrate the advantage of CVFR using the x264 open-source video encoder. The results show that CVFR-ECO yields an average PSNR and VMAF increase of 0.02 dB and 2.50 points, respectively, for the same bitrate, compared to the fastest preset highest framerate encoding. CVFR-ECO also yields an average encoding and storage energy consumption reduction of 34.54% and 76.24%, considering a just noticeable difference (JND) of six VMAF points. In comparison, CVFR-HQ yields an average increase in PSNR and VMAF of 2.43 dB and 10.14 points, respectively, for the same bitrate. Finally, CVFR-HQ resulted in an average reduction in storage energy consumption of 83.18%, considering a JND of six VMAF points.
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- 2023
37. Photometry of the Didymos system across the DART impact apparition
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Moskovitz, Nicholas, Thomas, Cristina, Pravec, Petr, Lister, Tim, Polakis, Tom, Osip, David, Kareta, Theodore, Rożek, Agata, Chesley, Steven R., Naidu, Shantanu P., Scheirich, Peter, Ryan, William, Ryan, Eileen, Skiff, Brian, Snodgrass, Colin, Knight, Matthew M., Rivkin, Andrew S., Chabot, Nancy L., Ayvazian, Vova, Belskaya, Irina, Benkhaldoun, Zouhair, Berteşteanu, Daniel N., Bonavita, Mariangela, Bressi, Terrence H., Brucker, Melissa J., Burgdorf, Martin J., Burkhonov, Otabek, Burt, Brian, Contreras, Carlos, Chatelain, Joseph, Choi, Young-Jun, Daily, Matthew, de León, Julia, Ergashev, Kamoliddin, Farnham, Tony, Fatka, Petr, Ferrais, Marin, Geier, Stefan, Gomez, Edward, Greenstreet, Sarah, Gröller, Hannes, Hergenrother, Carl, Holt, Carrie, Hornoch, Kamil, Husárik, Marek, Inasaridze, Raguli, Jehin, Emmanuel, Khalouei, Elahe, Eluo, Jean-Baptiste Kikwaya, Kim, Myung-Jin, Krugly, Yurij, Kučáková, Hana, Kušnirák, Peter, Larsen, Jeffrey A., Lee, Hee-Jae, Lejoly, Cassandra, Licandro, Javier, Longa-Peña, Penélope, Mastaler, Ronald A., McCully, Curtis, Moon, Hong-Kyu, Morrell, Nidia, Nath, Arushi, Oszkiewicz, Dagmara, Parrott, Daniel, Phillips, Liz, Popescu, Marcel M., Pray, Donald, Prodan, George Pantelimon, Rabus, Markus, Read, Michael T., Reva, Inna, Roark, Vernon, Santana-Ros, Toni, Scotti, James V., Tatara, Taiyo, Thirouin, Audrey, Tholen, David, Troianskyi, Volodymyr, Tubbiolo, Andrew F., and Villa, Katelyn
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Astrophysics - Earth and Planetary Astrophysics - Abstract
On 26 September 2022, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes (Thomas et al. 2023). Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite's orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from July 2022 to February 2023. We focus here on decomposable lightcurves, i.e. those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the post-impact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ~1 day after impact, and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days post-impact. This bulk photometric behavior was not well represented by an HG photometric model. An HG1G2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least March 2023. Its persistence implied ongoing escape of ejecta from the system many months after DART impact., Comment: 52 pages, 5 tables, 9 figures, accepted to PSJ
- Published
- 2023
38. Operator product states on tensor powers of C∗-algebras
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Prodan, Emil
- Published
- 2025
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39. Cost modelling and optimisation for cloud: a graph-based approach
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Khan, Akif Quddus, Matskin, Mihhail, Prodan, Radu, Bussler, Christoph, Roman, Dumitru, and Soylu, Ahmet
- Published
- 2024
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40. Biopurification using non-growing microorganisms to improve plant protein ingredients
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Nugroho, Avis Dwi Wahyu, van Schalkwijk, Saskia, Cebeci, Sabri, Jacobs, Simon, Wesselink, Wilma, Staring, Guido, Goerdayal, Soenita, Prodan, Andrei, Stijnman, Ann, Teuling, Emma, Broersen, Kerensa, and Bachmann, Herwig
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- 2024
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41. Dynamic learning of individual-level suicidal ideation trajectories to enhance mental health care
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Varidel, Mathew, Hickie, Ian B., Prodan, Ante, Skinner, Adam, Marchant, Roman, Cripps, Sally, Oliveria, Rafael, Chong, Min K., Scott, Elizabeth, Scott, Jan, and Iorfino, Frank
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- 2024
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42. Exploring the influence of nasal morbidity on quality of life following endoscopic endonasal skull base surgery: a retrospective cohort study of 95 patients
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Hegde, Rutwik, Prodan, Vlad, Futera, Karolina, Hathorn, Iain, Gohil, Rohit, and Hughes, Mark A.
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- 2024
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43. Implementing fundamental symmetries with passive meta-materials
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Prodan, Emil, speaker
- Abstract
Time-reversal and particle-hole symmetries are fundamental for stabilizing the topological phases seen in the periodic table of topological insulators and superconductors. These symmetries can act anti-unitarily and square to minus the identity and, as such, are un-natural for system with classical degrees of freedom. In this talk, I will review a proposal on how to implement these symmetries exactly and over a large range of frequencies. I will also emphasize why is important to implement every entry in the classification table and I will review several applications enabled by the proposed theoretical framework.
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- 2024
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44. Direct imaging of spatial heterogeneities in type II superconductors
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Evans, Donald M., Conroy, Michele, Puntigam, Lukas, Croitori, Dorina, Prodan, Lilian, Douglas, James O., Gault, Baptiste, and Tsurkan, Vladimir
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Condensed Matter - Superconductivity ,Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons - Abstract
Understanding the exotic properties of quantum materials, including high-temperature superconductors, remains a formidable challenge that demands direct insights into electronic conductivity. Current methodologies either capture a bulk average or near-atomically-resolved information, missing direct measurements at the critical intermediate length scales. Here, using the superconductor Fe(Se,Te) as a model system, we use low-temperature conductive atomic force microscopy (cAFM) to bridge this gap. Contrary to the uniform superconductivity anticipated from bulk assessments, cAFM uncovers micron-scale conductive intrusions within a relatively insulating matrix. Subsequent compositional mapping through atom probe tomography, shows that differences in conductivity correlated with local changes in composition. cAFM, supported by advanced microscopy and microanalysis, represents a methodological breakthrough that can be used to navigate the intricate landscape of high-temperature superconductors and the broader realm of quantum materials. Such fundamental information is critical for theoretical understanding and future guided design.
- Published
- 2023
45. Comparison of Microservice Call Rate Predictions for Replication in the Cloud
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Mehran, Narges, Haghighi, Arman, Aminharati, Pedram, Nikolov, Nikolay, Soylu, Ahmet, Roman, Dumitru, and Prodan, Radu
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Computer Science - Distributed, Parallel, and Cluster Computing ,Computer Science - Artificial Intelligence ,Computer Science - Machine Learning ,Computer Science - Neural and Evolutionary Computing - Abstract
Today, many users deploy their microservice-based applications with various interconnections on a cluster of Cloud machines, subject to stochastic changes due to dynamic user requirements. To address this problem, we compare three machine learning (ML) models for predicting the microservice call rates based on the microservice times and aiming at estimating the scalability requirements. We apply the linear regression (LR), multilayer perception (MLP), and gradient boosting regression (GBR) models on the Alibaba microservice traces. The prediction results reveal that the LR model reaches a lower training time than the GBR and MLP models. However, the GBR reduces the mean absolute error and the mean absolute percentage error compared to LR and MLP models. Moreover, the prediction results show that the required number of replicas for each microservice by the gradient boosting model is close to the actual test data without any prediction., Comment: 7 pages, 5 figures, 4 tables
- Published
- 2023
46. Quasimolecular $J_{\rm tet}$=3/2 moments in the cluster Mott insulator GaTa$_4$Se$_8$
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Magnaterra, M., Attig, J., Peterlini, L., Hermanns, M., Upton, M. H., Kim, Jungho, Prodan, L., Tsurkan, V., Kézsmárki, I., van Loosdrecht, P. H. M., and Grüninger, M.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
Quasimolecular orbitals in cluster Mott insulators provide a route to tailor exchange interactions, which may yield novel quantum phases of matter. We demonstrate the cluster Mott character of the lacunar spinel GaTa$_4$Se$_8$ using resonant inelastic x-ray scattering (RIXS) at the Ta $L_3$ edge. Electrons are fully delocalized over Ta$_4$ tetrahedra, forming quasimolecular $J_{\rm tet}$=3/2 moments. The modulation of the RIXS intensity as function of the transferred momentum q allows us to determine the cluster wavefunction, which depends on competing intracluster hopping terms that mix states with different character. This mixed wavefunction is decisive for the macroscopic properties since it affects intercluster hopping and exchange interactions and furthermore renormalizes the effective spin-orbit coupling constant. The versatile wavefunction, tunable via intracluster hopping, opens a new perspective on the large family of lacunar spinels and cluster Mott insulators in general., Comment: 7 pages, 4 figures, plus supplementary information
- Published
- 2023
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47. Nonlinear Model Predictive Control for Uranium Extraction-Scrubbing Operation in Spent Nuclear Fuel Treatment Process
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Vo, Duc-Tri, Prodan, Ionela, Lefèvre, Laurent, Vanel, Vincent, Costenoble, Sylvain, and Dinh, Binh
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Electrical Engineering and Systems Science - Systems and Control - Abstract
This paper addresses the particularities of the uranium extraction-scrubbing operation in a spent nuclear fuel treatment process (PUREX-Plutonium Uranium Refining by Extraction) through the use of set-point tracking MPC (Model Predictive Control). The presented controller uses the feed solution flow rate as the manipulated variable to control the saturation of the solvent at the extraction step. In addition, it guarantees not to loose uranium in the raffinates, and ensures equipment limitations during operation time. Simulation results show that the tracking NMPC effectively ensures accurate set point tracking and constraints guarantee. As a result, the system can be driven to its optimal working condition, avoid and recover from constraint violations. The control performance was compared with PID and openloop controllers.
- Published
- 2023
48. Experimental validation of an explicit flatness-based MPC design for quadcopter position tracking
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Do, Huu-Thinh and Prodan, Ionela
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Electrical Engineering and Systems Science - Systems and Control - Abstract
Due to the nonlinearities and operational constraints typical to quadcopter missions, Model Predictive Control (MPC) encounters the major challenge of high computational power necessary for the online implementation. This problem may prove impractical, especially for a hardware-limited or small-scale setup. By removing the need for online solvers while keeping the constraint satisfaction and optimality, Explicit MPC (ExMPC) stands out as a strong candidate for this application. Yet, the formulation was usually hindered by the two main problems: nonlinearity and dimensionality. In this paper, we propose an ExMPC solution for the quadcopter position stabilization by analyzing its description (dynamics and constraints) in the flat output space. With the former issue, the system is exactly linearized into a concatenation of three double integrators at a price of cumbersome constraints in the new coordinates. For the latter, with a suitable characterization of these constraints, the stabilizing ExMPC can be computed for each double integrator separately. The controller is then validated via simulations and experimental tests. The proposed scheme achieves similar performance and guarantees to the state-of-the-art solution but with notably less computational effort, allowing scalability in a centralized manner
- Published
- 2023
49. Enhancements on a saturated control for stabilizing a quadcopter: adaptive and robustness analysis in the flat output space
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Do, Huu-Thinh, Blanchini, Franco, and Prodan, Ionela
- Subjects
Electrical Engineering and Systems Science - Systems and Control - Abstract
This paper extends our previous study on an explicit saturated control for a quadcopter, which ensures both constraint satisfaction and stability thanks to the linear representation of the system in the flat output space. The novelty here resides in the adaptivity of the controller's gain to enhance the system's performance without exciting its parasitic dynamics and avoid lavishing the input actuation with excessively high gain parameters. Moreover, we provide a thorough robustness analysis of the proposed controller when additive disturbances are affecting the system behavior. Finally, simulation and experimental tests validate the proposed controller.
- Published
- 2023
50. Classifying the Dynamics of Architected Materials by Groupoid Methods
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Mesland, Bram and Prodan, Emil
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Mathematics - Operator Algebras ,Condensed Matter - Materials Science ,Mathematical Physics - Abstract
We consider synthetic materials consisting of self-coupled identical resonators carrying classical internal degrees of freedom. The architecture of such material is specified by the positions and orientations of the resonators. Our goal is to calculate the smallest C*-algebra that covers the dynamical matrices associated to a fixed architecture and adjustable internal structures. We give the answer in terms of a groupoid C*-algebra that can be canonically associated to a uniformly discrete subset of the group of isometries of the Euclidean space. Our result implies that the isomorphism classes of these C*-algebras split these architected materials into classes containing materials that are identical from the dynamical point of view.
- Published
- 2023
- Full Text
- View/download PDF
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