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Social science & medicine (1982) 2025年 369卷 117577页

作者： Sophie Bright Charlotte Buckley Daniel Holman George Leckie Andrew Bell Nina Mulia Carolin Kilian Robin Purshouse Sheffield Centre for Health and Related Research (ScHARR) Faculty of Medicine Dentistry & Health University of Sheffield Sheffield UK. Electronic address: serbright1@sheffield.ac.uk. Department of Automatic Control and Systems Engineering University of Sheffield UK Department of Psychology Institute of Population Health University of Liverpool UK. Department of Sociological Studies University of Sheffield Sheffield UK. Centre for Multilevel Modelling and School of Education University of Bristol UK. Sheffield Methods Institute University of Sheffield Sheffield UK. Alcohol Research Group Public Health Institute Emeryville CA USA. Institute for Mental Health Policy Research Centre for Addiction and Mental Health Toronto Ontario Canada Center for Interdisciplinary Addiction Research (ZIS) Department of Psychiatry and Psychotherapy University Medical Center Hamburg-Eppendorf (UKE) Hamburg Germany. Department of Automatic Control and Systems Engineering University of Sheffield UK.

The temporal and spatial evolution of MHD wave modes in sunspots

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arXiv 2023年

作者： Albidah, A.B. Fedun, V. Aldhafeeri, A.A. Ballai, I. Jess, D.B. Brevis, W. Higham, J. Stangalini, M. Silva, S.S.A. MacBride, C.D. Verth, G. Department of Mathematics College Of Science Majmaah University P.O Box 66 Majmaah11952 Saudi Arabia Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom Mathematics and Statistic Department Faculty of Science King Faisal University Al-Hassa P.O. Box 400 Hofuf31982 Saudi Arabia Plasma Dynamics Group School of Mathematics and Statistics The University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Astrophysics Research Centre School of Mathematics and Physics Queen’s University Belfast BelfastBT7 1NN United Kingdom Department of Physics and Astronomy California State University Northridge NorthridgeCA91330 United States School of Engineering Pontificia Universidad Católica de Chile Chile School of Environmental Sciences Department of Geography and Planning University of Liverpool Roxby Building LiverpoolL69 7ZT United Kingdom ASI Italian Space Agency Via del Politecnico snc Rome00133 Italy

Through their lifetime sunspots undergo a change in their area and shape and, as they decay, they fragment into smaller structures. Here, for the first time we analyze the spatial structure of magneto-hydrodynamic (MHD) slow body and fast surface modes in observed umbrae as their cross-sectional shape changes. The Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) techniques were used to analyze 3 and 6 hours SDO/HMI time series of Doppler velocities at the photospheric level of approximately circular and elliptically shaped sunspots. Each time series were divided equally into time intervals, to evidence the change of the sunspots’ shape. To identify physical wave modes, the POD/DMD modes were cross-correlated with a slow body mode model using the exact shape of the umbra, whereas the shape obtained by applying a threshold level of the mean intensity for every time interval. Our results show that the spatial structure of MHD modes are affected, even by apparently small changes of the umbral shape, especially in the case of the higher-order modes. For the datasets used in our study, the optimal time intervals to consider the influence of the change in the shape on the observed MHD modes is 37 - 60 minutes. The choice of these intervals is crucial to properly quantify the energy contribution of each wave mode to the power spectrum. © 2023, CC0.

关键词： Dynamic mode decomposition

Abstractions of linear dynamic networks for input selection in local module identification

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arXiv 2019年

作者： Weerts, Harm H.M. Linder, Jonas Enqvist, Martin Hof, Paul M J Van den Control Systems Group Department of Electrical Engineering Eindhoven University of Technology Netherlands ABB Corporate Research Västerås Sweden Division of Automatic Control Linköping University Sweden

In abstractions of linear dynamic networks, selected node signals are removed from the network, while keeping the remaining node signals invariant. The topology and link dynamics, or modules, of an abstracted network will generally be changed compared to the original network. Abstractions of dynamic networks can be used to select an appropriate set of node signals that are to be measured, on the basis of which a particular local module can be estimated. A method is introduced for network abstraction that generalizes previously introduced algorithms, as e.g. immersion and the method of indirect inputs. For this abstraction method it is shown under which conditions on the selected signals a particular module will remain invariant. This leads to sets of conditions on selected measured node variables that allow identification of the target module. Copyright © 2019, The Authors. All rights reserved.

关键词： Network theory (graphs)

Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere

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arXiv 2020年

作者： Silva, Suzana S.A. Fedun, Viktor Verth, Gary Rempel, Erico L. Shelyag, Sergiy Department of Physics Aeronautics Institute of Technology So Jos dos Campos Brazil Plasma Dynamics Group Department of Automatic Control and Systems Engineering University of Sheffield Sheffield United Kingdom Plasma Dynamics Group School of Mathematics and Statistics University of Sheffield Sheffield United Kingdom Department of Mathematics Aeronautics Institute of Technology So Jos dos Campos Brazil School of Information Technology Deakin University Geelong Australia

In this work, a state-of-the-art vortex detection method, Instantaneous Vorticity Deviation, is applied to locate three-dimensional vortex tube boundaries in numerical simulations of solar photospheric magnetoconvection performed by the MURaM code. We detected three-dimensional vortices distributed along intergranular regions and displaying coned shapes that extend from the photosphere to the low chromosphere. Based on a well-defined vortex center and boundary, we were able to determine averaged radial profiles and thereby investigate the dynamics across the vortical flows at different height levels. The solar vortex tubes present nonuniform angular rotational velocity, and, at all height levels, there are eddy viscosity effects within the vortices, which slow down the plasma as it moves toward the center. The vortices impact the magnetic field as they help to intensify the magnetic field at the sinking points, and in turn, the magnetic field ends up playing an essential role in the vortex dynamics. The magnetic field was found to be especially important to the vorticity evolution. On the other hand, it is shown that, in general, kinematic vortices do not give rise to magnetic vortices unless their tangential velocities at different height levels are high enough to overcome the magnetic tension. Copyright © 2020, The Authors. All rights reserved.

关键词： Vortex flow

Event-triggered Learning for Linear Quadratic control

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arXiv 2019年

作者： Schlüter, Henning Solowjow, Friedrich Trimpe, Sebastian Intelligent Control Systems Group Max Planck Inst. for Intelligent Systems Stuttgart70569 Germany Institute for Systems Theory and Automatic Control University of Stuttgart Stuttgart70550 Germany Institute for Data Science in Mechanical Engineering RWTH Aachen University Aachen52068 Germany

When models are inaccurate, the performance of model-based control will degrade. For linear quadratic control, an event-triggered learning framework is proposed that automatically detects inaccurate models and triggers the learning of a new process model when needed. This is achieved by analyzing the probability distribution of the linear quadratic cost and designing a learning trigger that leverages Chernoff bounds. In particular, whenever empirically observed cost signals are located outside the derived confidence intervals, we can provably guarantee that this is with high probability due to a model mismatch. With the aid of numerical and hardware experiments, we demonstrate that the proposed bounds are tight and that the event-triggered learning algorithm effectively distinguishes between inaccurate models and probabilistic effects such as process noise. Thus, a structured approach is obtained that decides when model learning is beneficial. Copyright © 2019, The Authors. All rights reserved.

关键词： Stochastic systems

Slow magnetoacoustic waves in gravitationally stratified two-fluid plasmas in strongly ionised limit

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arXiv 2020年

作者： Alharbi, Abdulaziz Ballai, I. Fedun, V. Verth, G. Plasma Dynamics Group School of Mathematics and Statistics University of Sheffield Housnfield Road Hicks Building SheffieldS3 7RH United Kingdom Department of Mathematics Jamoum University College Umm Al-Qura University Jamoum Makkah Saudi Arabia Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom

The plasma dynamics at frequencies comparable with collisional frequency between various species has to be described in multi-fluid framework, where collisional interaction between particles is an important ingredient. In our study we will assume that charged particles are strongly coupled, meaning that they form a single fluid that interacts with neutrals, therefore we will employ a two-fluid model. Here we aim to investigate the evolutionary equation of slow sausage waves propagating in a gravitationally stratified flux tube in the two-fluid solar atmosphere in a strongly ionised limit using an initial value analysis. Due to the collisional interaction between massive particles (ions and neutrals) the governing equations are coupled. Solutions are sought in the strongly ionised limit and the density ratio between neutrals and charged particles is a small parameter. This limit is relevant to the upper part of the chromosphere. Our results show that slow sausage waves associated with charged particles propagate such that their possible frequency is affected by a cut-off due to the gravitational stratification. In contrast, for neutral acoustic waves the cut-off value applies on their wavelength and only small wavelength waves are able to propagate. Slow modes associated to neutrals are driven by the collisional coupling with ions. © 2020, CC0.

关键词： Magnetohydrodynamics

An Early Stage Researcher's Primer on systems Medicine Terminology

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Network and Systems Medicine

Network and systems Medicine 2021年第1期4卷 2-50页

作者： Zanin, Massimiliano Aitya, Nadim A.A. Basilio, José Baumbach, Jan Benis, Arriel Behera, Chandan K. Bucholc, Magda Castiglione, Filippo Chouvarda, Ioanna Comte, Blandine Dao, Tien-Tuan Ding, Xuemei Pujos-Guillot, Estelle Filipovic, Nenad Finn, David P. Glass, David H. Harel, Nissim Iesmantas, Tomas Ivanoska, Ilinka Joshi, Alok Boudjeltia, Karim Zouaoui Kaoui, Badr Kaur, Daman Maguire, Liam P. McClean, Paula L. McCombe, Niamh De Miranda, João Luís Moisescu, Mihnea Alexandru Pappalardo, Francesco Polster, Annikka Prasad, Girijesh Rozman, Damjana Sacala, Ioan Sanchez-Bornot, Jose M. Schmid, Johannes A. Sharp, Trevor Solé-Casals, Jordi Spiwok, Vojtěch Spyrou, George M. Stalidzans, Egils Stres, Blaa Sustersic, Tijana Symeonidis, Ioannis Tieri, Paolo Todd, Stephen Van Steen, Kristel Veneva, Milena Wang, Da-Hui Wang, Haiying Wang, Hui Watterson, Steven Wong-Lin, Kongfatt Yang, Su Zou, Xin Schmidt, Harald H.H.W. Centro de Tecnología Biomédica Universidad Politécnica de Madrid Madrid Spain Intelligent Systems Research Centre School of Computing Engineering and Intelligent Systems Ulster University Ulster United Kingdom Center for Physiology and Pharmacology Institute of Vascular Biology and Thrombosis Research Medical University of Vienna Vienna Austria TUM School of Life Sciences Weihenstephan Technical University of Munich Freising Germany Holon Israel CNR National Research Council IAC Institute for Applied Computing Rome Italy Lab of Computing Medical Informatics and Biomedical Imaging Technologies School of Medicine Aristotle University of Thessaloniki Thessaloniki Greece Université Clermont Auvergne INRAE UNH Plateforme d'Exploration du Métabolisme MetaboHUB Clermont Clermont-Ferrand France Université de Technologie de Compiègne Compiègne France Labex MS2T Control of Technological Systems-of-Systems CNRS and Université de Technologie de Compiègne Compiègne France Faculty of Engineering University of Kragujevac Kragujevac Serbia Kragujevac Serbia Steinbeis Advanced Risk Technologies Institute Doo Kragujevac Kragujevac Serbia Pharmacology and Therapeutics School of Medicine Galway Neuroscience Centre National University of Ireland Galway Ireland School of Computing Ulster University Ulster United Kingdom Holon Israel Department of Mathematics and Natural Sciences Kaunas University of Technology Kaunas Lithuania Faculty of Computer Science and Engineering Ss. Cyril and Methodius University Skopje Macedonia Medicine Faculty Université Libre de Bruxelles CHU de Charleroi Charleroi Belgium Northern Ireland Centre for Stratified Medicine Biomedical Sciences Research Institute Ulster University Ulster United Kingdom Escola Superior de Tecnologia e Gestão Instituto Politécnico de Portalegre Portalegre Portugal Instituto Superior Técnico Universidade de Lisboa Lisboa Portugal Faculty of Automatic Control and Computers University Politehnica of B

Background: systems Medicine is a novel approach to medicine, that is, an interdisciplinary field that considers the human body as a system, composed of multiple parts and of complex relationships at multiple levels, and further integrated into an environment. Exploring systems Medicine implies understanding and combining concepts coming from diametral different fields, including medicine, biology, statistics, modeling and simulation, and data science. Such heterogeneity leads to semantic issues, which may slow down implementation and fruitful interaction between these highly diverse fields. Methods: In this review, we collect and explain more than100 terms related to systems Medicine. These include both modeling and data science terms and basic systems medicine terms, along with some synthetic definitions, examples of applications, and lists of relevant references. Results: This glossary aims at being a first aid kit for the systems Medicine researcher facing an unfamiliar term, where he/she can get a first understanding of them, and, more importantly, examples and references for digging into the topic. © Massimiliano Zanin et al., 2021;Published by Mary Ann Liebert, Inc. 2021.

关键词： Semantics

The Propagation of Coherent Waves Across Multiple Solar Magnetic Pores

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arXiv 2022年

作者： Grant, Samuel D.T. Jess, D.B. Stangalini, M. Jafarzadeh, S. Fedun, V. Verth, G. Keys, P.H. Rajaguru, S.P. Uitenbroek, H. Macbride, C.D. Bate, W. Gilchrist-Millar, C.A. Astrophysics Research Centre School of Mathematics and Physics Queen's University Belfast BelfastBT7 1NN United Kingdom Department of Physics and Astronomy California State University Northridge NorthridgeCA91330 United States ASI Italian Space Agency Via del Politecnico snc Rome00133 Italy Schöneckstr. 6 Freiburg79104 Germany Rosseland Centre for Solar Physics University of Oslo P.O. Box 1029 Blindern Oslo0315 Norway Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom Plasma Dynamics Group School of Mathematics and Statistics The University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Indian Institute of Astrophysics Bangalore34 India National Solar Observatory University of Colorado Boulder 3665 Discovery Drive BoulderCO80303 United States

Solar pores are efficient magnetic conduits for propagating magnetohydrodynamic wave energy into the outer regions of the solar atmosphere. Pore observations often contain isolated and/or unconnected structures, preventing the statistical examination of wave activity as a function of atmospheric height. Here, using high resolution observations acquired by the Dunn Solar Telescope, we examine photospheric and chromospheric wave signatures from a unique collection of magnetic pores originating from the same decaying sunspot. Wavelet analysis of high cadence photospheric imaging reveals the ubiquitous presence of slow sausage mode oscillations, coherent across all photospheric pores through comparisons of intensity and area fluctuations, producing statistically significant in-phase relationships. The universal nature of these waves allowed an investigation of whether the wave activity remained coherent as they propagate. Utilizing bi-sector Doppler velocity analysis of the Ca II 8542 Å line, alongside comparisons of the modeled spectral response function, we find fine-scale 5 mHz power amplification as the waves propagate into the chromosphere. Phase angles approaching zero degrees between co-spatial line depths spanning different line depths indicate standing sausage modes following reflection against the transition region boundary. Fourier analysis of chromospheric velocities between neighboring pores reveals the annihilation of the wave coherency observed in the photosphere, with examination of the intensity and velocity signals from individual pores indicating they behave as fractured wave guides, rather than monolithic structures. Importantly, this work highlights that wave morphology with atmospheric height is highly complex, with vast differences observed at chromospheric layers, despite equivalent wave modes being introduced into similar pores in the photosphere. © 2022, CC BY.

关键词： Magnetohydrodynamics

Magnetohydrodynamic wave mode identification in circular and elliptical sunspot umbrae: evidence for high order modes

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arXiv 2022年

作者： Albidah, Abdulrahman B. Fedun, V. Aldhafeeri, A.A. Ballai, I. Brevis, W. Jess, D.B. Higham, J. Stangalini, M. Silva, S.S.A. Verth, G. Plasma Dynamics Group School of Mathematics and Statistics The University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Department of Mathematics College of Science Al-Zulfi Majmaah University Al-Majmaah 11952 Saudi Arabia Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom Mathematics and Statistic Department Faculty of Science King Faisal University Al-Hassa P.O. Box 400 Hofuf31982 Saudi Arabia School of Engineering Pontificia Universidad Católica de Chile Chile Astrophysics Research Centre School of Mathematics and Physics Queen's University BelfastBT7 1NN United Kingdom Department of Physics and Astronomy California State University Northridge NorthridgeCA91330 United States School of Environmental Sciences Department of Geography and Planning University of Liverpool Roxby Building LiverpoolL69 7ZT United Kingdom ASI Italian Space Agency Via del Politecnico snc Rome00133 Italy

In this paper we provide clear direct evidence of multiple concurrent higher order magnetohydrodynamic (MHD) modes in circular and elliptical sunspots by applying both Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) techniques on solar observational data. These techniques are well documented and validated in the areas of fluid mechanics, hydraulics, and granular flows, yet are relatively new to the field of solar physics. While POD identifies modes based on orthogonality in space and it provides a clear ranking of modes in terms of their contribution to the variance of the signal, DMD resolves modes that are orthogonal in time. The clear presence of the fundamental slow sausage and kink body modes, as well as higher order slow sausage and kink body modes have been identified using POD and DMD analysis of the chromospheric Hα line at 6562.808 Å for both the circular and elliptical sunspots. Additionally, to the various slow body modes, evidence for the presence of the fast surface kink mode was found in the circular sunspot. All the MHD modes patterns were cross-correlated with their theoretically predicted counterparts and we demonstrated that ellipticity cannot be neglected when interpreting MHD wave modes. The higher-order MHD wave modes are even more sensitive to irregularities in umbral cross-sectional shapes, hence this must be taken into account for more accurate modelling of the modes in sunspots and pores. Copyright © 2022, The Authors. All rights reserved.

关键词： Magnetohydrodynamics

Small-scale solar jet formation and their associated waves and instabilities

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arXiv 2022年

作者： Skirvin, Samuel Verth, Gary González-Avilés, José Juan Shelyag, Sergiy Sharma, Rahul Guzmán, Francisco S. Ballai, Istvan Scullion, Eamon Silva, Suzana S.A. Fedun, Viktor Center for Mathematical Plasma Astrophysics Mathematics Department KU Leuven Celestijnenlaan 200B bus 2400 LeuvenB-3001 Belgium Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom Plasma Dynamics Group School of Mathematics and Statistics The University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Investigadores por México CONACYT Servicio de Clima Espacial Méxio Laboratorio Nacional de Clima Espacial Instituto de Geofísica Unidad Michoacán Universidad Nacional Autónoma de México Antigua Carretera a Pátzcuaro 8701 Ex-Hacienda de San José de la Huerta Michoacán Morelia58190 Mexico School of Information Technology Deakin University Melbourne3125 Australia Department of Mathematics Physics and Electrical Engineering Northumbria University Newcastle upon TyneNE1 8ST United Kingdom Instituto de Física y Matemáticas Universidad Michoacana de San Nicolás de Hidalgo Edificio C3 Cd. Universitaria Morelia Michoacán 5840 Mexico

Studies on small-scale jets’ formation, propagation, evolution, and role, such as type I and II spicules, mottles, and fibrils in the lower solar atmosphere’s energetic balance, have progressed tremendously thanks to the combination of detailed observations and sophisticated mathematical modelling. This review provides a survey of the current understanding of jets, their formation in the solar lower atmosphere, and their evolution from observational, numerical, and theoretical perspectives. First, we review some results to describe the jet properties, acquired numerically, analytically and through high-spatial and temporal resolution observations. Further on, we discuss the role of hydrodynamic and magnetohydrodynamic instabilities, namely Rayleigh-Taylor and Kelvin-Helmholtz instabilities, in jet evolution and their role in the energy transport through the solar atmosphere in fully and partially ionised plasmas. Finally, we discuss several mechanisms of magnetohydrodynamic wave generation, propagation, and energy transport in the context of small-scale solar jets in detail. This review identifies several gaps in the understanding of small-scale solar jets and some misalignments between the observational studies and knowledge acquired through theoretical studies and numerical modelling. It is to be expected that these gaps will be closed with the advent of high-resolution observational instruments, such as Daniel K. Inouye Solar Telescope, Solar Orbiter, Parker Solar Probe, and Solar CubeSats for Linked Imaging Spectropolarimetry, combined with further theoretical and computational developments. © 2022, CC BY.

关键词： Magnetohydrodynamics