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Digital twinning of thermal problems in fusion energy systems
No full textDigital Twinning (DT) technology is in the process of becoming an essential instrument for optimising efficiency, ensuring safety, and enhancing research productivity of the fusion energy experimental facilities. A digital twin represents a virtual counterpart of a physical system that maintains real-time synchronisation through the sensor-derived data. Within fusion energy experimental facilities, DT technology enables enhanced information extraction from the experimental data and facilitates optimal control. This work presents two distinct methodologies facilitating DT control of a sample.The first DT approach, Finite Element-based Digital Twinning (FE DT) is a dual-component control system comprising of a full-solution construction from limited data and a control mechanism. The solution reconstruction operates in near-real-time for small scale problems through a novel Finite Element (FE)-based data integration approach that transforms sparse measurements into comprehensive solutions for non-linear systems. This method integrates FE discretisation with a loss function minimisation to generate complete solutions from limited measurement data. Jacobian matrices are computed analytically rather than through Automatic Differentiation (AD). The control component consists of a digital (discrete) Proportional–Integral–Derivative (PID)controller that regulates the cooling water temperature of the test specimens. The modification of the solution construction approach involves its coupling with the thermal eigenvalue-based Reduced Order Modelling (ROM). This allows for the speed-up of the solution construction process whilst keeping the overall procedure the same.The second DT approach, Physics-Driven Machine Learning-based Digital Twinning (PD-ML DT), is rooted in Machine Learning (ML). It involves training two Neural Network (NN) using steady-state data. A two-part NN system is employed, forming a control loop. The first part, the heat flux NN, addresses the challenge of estimating thermal conditions. Its aim is to construct a steady-state equivalent of the heat flux based on the provided temperature measurements. The second part, the coolant NN, provides a solution for active thermal management. In this work, it determines the necessary coolant velocity to maintain the maximum sample temperature below a specified threshold. The additional adjustments are made to ensure the system’s effectiveness and robustness when dealing with dynamic system. These include extrapolating the constructed heat flux and selecting the maximum value from a range of past and extrapolated data points. These adjustments are critical as they account for the fact that both NNs are trained on steady-state data, allowing them to operate effectively in non-steady-state conditions. This combined approach enables real-time temperature monitoring and control addressing a challenge in thermal system management.The performance of two DT systems is demonstrated through the cooling control analysis of samples which were previously evaluated in a fusion energy experimental facility.Various system responses are generated under their control, and they are compared based on the accuracy, speed, and the resistance to measurement noise. The results show that they display advantages and disadvantages based on the information which could be provided during the experiment. Primarily, FE DT requires more measurements than PD-ML DT in the presence of noise; however, it has the ability to provide more information compared with PD-ML DT in the form of the full temperature field. As opposed with PD-ML DT, FE DT does not have instantaneous inference time; however, by employing ROM as part of the workflow it could be reduced.The reported development of DT process for thermal systems, powered by FE combined with PID controller or a dual NN control loop, holds significant implications for the future of fusion energy research and beyond. By enabling real-time monitoring and active thermal management, it provides a crucial tool for optimising the performance and ensuring the safety of experimental fusion facilities. This approach moves the progress closer to autonomous, self-correcting systems that can operate with greater efficiency and reliability. The methodology’s application extends beyond fusion, offering a template for managing thermal systems in a wide range of engineering fields where sparse measurements are involved
Simple minimally unsatisfiable subsets of 2-CNFs
No full textWe present a study of minimal unsatisfiable subsets (MUSs) of 2-CNF Boolean formulas, building on the Abbasizanjani-Kullmann classification of minimally unsatisfiable 2-CNFs (2-MUs). We start by giving a linear-time procedure for recognising 2-MUs. Then we study the problem of finding one simple MUS. On the one hand we extend the results by Kleine Buening et al, which showed NP-completeness of the decision, whether a deficiency-1 MUS exists. On the other hand we show that deciding/finding an MUS containing one or two unit-clauses (which are special deficiency-1 MUSs) can be done in polynomial time. Finally we present an incremental polynomial time algorithm for some special type of MUSs, namely those MUSs containing at least one unit-clause. We conclude by discussing the main open problem, developing a deeper understanding of the landscape of easy/hard MUSs of 2-CNFs
Enhanced super-harmonic resonance in piezoelectrically laminated curved microbeam resonators under fringing-field electrostatic actuation
No full textAchieving low-frequency MEMS resonators while maintaining the compact size of MEMS sensors has long been a challenge in MEMS design and fabrication. This study focuses on the super-harmonic resonance regions and associated bifurcation points of a curved microbeam sandwiched between two piezoelectric layers and subjected to fringing-field electrostatic actuation. The nonlinear equations of motion are derived, and the dependence of the electrostatic force on displacement is analysed using a finite element approach. The microbeam is excited by a combination of DC and AC electrostatic actuation, along with a tuning DC piezoelectric voltage. The influence of the piezoelectric voltage on the variation of the natural frequency under a given DC electrostatic excitation is examined. The frequency response curves are obtained over a broad excitation range, extending from below the primary resonance, through the super-harmonic regime, and beyond the primary resonance region. Bifurcation points are identified using Floquet multipliers. The results indicate that strong quadratic and cubic nonlinearities lead to the emergence of super-harmonic resonance zones of orders 1/2 and 1/3 in the frequency response, enabling the development of low-frequency resonators while retaining the advantages of MEMS-scale sensors. This effect is particularly significant in the design of MEMS energy harvesters, facilitating energy extraction from low-frequency mechanical noise. The simultaneous presence of nonlinearities of orders 1/2 and 1/3 and even higher orders generates multiple resonance zones within the super-harmonic regime, enabling the design of broadband low-frequency energy harvesters and MEMS wide-bandpass filters
If you find me on the floor, stick some sugar in my mouth: The social production (and protection) of insulin risk among IPED communities
Full text linkIntroductionInsulin is used among image and performance enhancing drug (IPED) communities for its anabolic effects, but its use carries significant risks, with the acute danger being hypoglycaemia, which can be life-threatening if not properly managed. Within these communities, harm reduction practices and informal peer knowledge exchange play a critical role in the way substances are consumed. This qualitative study sought to understand these community practices regarding non-medical insulin use among people who use IPEDs.MethodSemi-structured interviews were conducted with people who use IPEDs, and specifically, insulin. Participants were asked about their risk practices, harm reduction strategies, and the community dynamics that shape their use of insulin. Our analysis centred on how social and material networks of peers, technologies, and information flows contribute to the social production and protection of risk.ResultsThe study involved an international cohort of 14 participants (13 men, 1 woman, aged 25-45, M = 33.34) who used insulin for non-medical purposes. The analysis revealed two themes: Intersecting Risks, which encompassed the physical, psychosocial, and self-imposed risks associated with insulin use, and Social Protection of Risks, focusing on community-driven harm reduction strategies. People who use insulin actively construct risk through community-driven knowledge and informal education. Social protection is facilitated through peer networks, where harm reduction strategies are shared.DiscussionThis research underscores the importance of community-care in harm reduction and challenges individualised models of risk management. It highlights the need for community-centred health interventions that recognise the relational dynamics of risk management among IPED-using communities
Does social health insurance portability promote rural labor migration? Evidence from health care reform in China
No full textA noncanonical role for Jagged1 in endothelial mechanotransduction
Full text linkThe Notch signaling pathway plays a crucial role in regulating endothelial biology. Notch signaling is sensitive to hemodynamic forces and governs mechanically driven cardiovascular development, physiology, and remodeling. However, the mechanisms by which mechanical forces integrate with the Notch pathway remain largely unknown. Here, we uncover a noncanonical role for the Notch ligand protein jagged-1 (Jagged1) in regulating the activity of mechanosensitive kinases in endothelial cells. We show that shear stress induces expression and relocalization of Jagged1 to cell junctions downstream of flow. Jagged1 expression under stress demonstrates magnitude dependence, and peaks at 0.8–1 Pa without impacting the Notch-activation potential of Jagged1. Jagged1 also regulates the activity of mechanosensitive kinases. Deletion of Jagged1 reduces the activity of vascular endothelial growth factor receptor 2 (VEGFR2) and mitogen-activated protein kinase (ERK) in vitro and diminished ERK activity in zebrafish embryos without affecting canonical Notch signaling. Furthermore, direct physical stimulation of Jagged1 using antibody-conjugated beads triggers the activation of VEGFR2 and ERK, mediated by Jagged1-induced proto-oncogene tyrosine-protein kinase Src activation. Taken together, we demonstrate a previously unknown noncanonical role for Jagged1 as a regulator of the activity of pathways involved in endothelial mechanotransduction
Underexplored Dimensions of Emerging Indoor Photovoltaics
Full text linkIndoor photovoltaics (IPVs) can significantly reduce reliance on disposable batteries in Internet of Things (IoT) devices. Yet, most evaluations use idealized lighting setups and single performance metrics, neglecting the influence of real indoor environments on device performance. This Perspective advances a deployment-centered approach: (i) realistic testing under mixed or hybrid lighting (daylight + artificial); (ii) intelligent integration that aligns absorber bandgap, series-connected cells, geometric fill factor, and power management integrated circuits with workloads and duty cycles; and (iii) IoT-ready stability assessed under the same realistic indoor scenes and light/dark sequences. We propose a compact field-to-lab pipeline, translate it into voltage-matching design rules, and use photon-to-compute metrics to link harvested power to on-device sensing and learning. The goal is low-maintenance, battery-free nodes that scale reliably in buildings, logistics, and wearable applications─ultimately cutting electronic waste
A comprehensive exposure-age dating approach to interpreting complex glacial and periglacial landscapes: The landform mosaic of Alnesdalen, a Norwegian alpine drainage basin
No full textOur aim was to use two exposure dating techniques in combination to understand the age and development of the full complement of glacial and periglacial landforms in the Alnesdalen drainage basin, southern Norway. This required the development of a comprehensive, landscape-scale approach based on 32 10Be dates from 9 landforms and 121 Schmidt-hammer dates from 106 landforms, which identified a palimpsest landscape consisting of a mosaic of landforms of different ages. The approach enabled a spatial and temporal reconstruction of Late Glacial and Holocene glacial variations, and a deeper understanding of the periglacial, paraglacial, and paraperiglacial response of the landscape to environmental change. Results suggest that the whole of the Alnesdalen drainage basin was ice-covered by the Scandinavian Ice Sheet at the Last Glacial Maximum and that deglaciation of the valley sides and floors occurred during the Bölling-Allerød Interstadial (~14.6–12.9 ka). Dated ice-marginal moraines establish the limits of the Scandinavian Ice Sheet and of local glaciers during the Younger Dryas Stadial (~12.9–11.7 ka). Glacier extent at the maxima of the Early Holocene ‘Erdalen Event’ (~10.2 ka) and the Late-Holocene ‘Little Ice Age’ (~0.3 ka) is clarified. The periglacial response to environmental change was dominated by paraglacial processes. In the Bölling-Allerød Interstadial, large rock-slope failures were activated and talus slopes, pronival ramparts, snow-avalanche fans, large-scale patterned ground, boulder fields and boulder pavements began to form. Permafrost aggradation during the Younger Dryas may have led to the formation of a short-lived rock glacier. Large-scale patterned ground, boulder fields and boulder pavements became inactive in a seasonal-frost climate before the onset of the Early Holocene Thermal Maximum. The wide range of Holocene exposure ages from periglacial landforms with diachronous surfaces, including snow-avalanche fans, talus slopes and pronival ramparts, indicate low-levels of periglacial activity throughout a relatively benign Holocene
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