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Optimal and Constrained Magnetic Control for Tokamak Early Operations and Commissioning
Get PDFNuclear fusion is projected to be the future clean and sustainable source of energy. The research is intense and has broken several records in terms of the power and length of fusion reactions. This dissertation is centered on tokamaks, toroidal-shaped devices developed to confine the high-temperature and energy plasma (a perfectly ionized gas) exploiting magnetic fields. In tokamaks, the necessity to have a stable, high performing plasma leads to a high interest in plasma control, in particular in plasma magnetic control, that needs to control the plasma shape and/or centroid position, plasma current, and to guarantee plasma vertical stability. The future reactors are expected to be much larger than the current ones, making necessary careful planning and testing of capability to lower the risk of accidents that could lead to serious damage of the machine and delays. The preparatory work consists in developing and testing all the plant functionality using engineering designed code: to model plasma scenario, the simultaneous solution of the Grad-Shafranov equations and the time evolution of the plasma kinetic profiles is needed. To achieve the desired plasma evolution during ramp-up while staying within safe operational limits (such as the reduced active current and voltage limits typically applied during commissioning phases), a combination of feedforward and feedback control actions is essential. In this thesis, the development of a new model-based procedure for the constrained optimization of plasma ramp-up, called the CREATE-ILC code (an enhancement of the CREATE-BD code), is presented. This tool formulates a constrained quadratic programming problem and employs a linear time-varying electromagnetic model to generate active currents and voltages that ensure the desired breakdown and ramp-up phases, while adhering to the imposed constraints. Given that model-based approaches are sensitive to uncertainties and disturbances, an Iterative Learning Control (ILC) strategy is incorporated to handle discrepancies between the desired and experimental behaviors. The CREATE-ILC’s ability to optimize ramp-up currents is anticipated to be validated during the MAST-U tokamak RT-04 experimental campaign. Although the nominal scenario can be programmed to respect current and voltage saturation limits, the feedback control architecture, which compensates for model uncertainties and disturbances, may inadvertently cause active currents to exceed these limits. To mitigate this risk, three Current Limit Avoidance (CLA) algorithms, designed for integration within the magnetic control architecture, are proposed. These algorithms replace any currents that exceed saturation limits with a pattern that minimizes performance degradation. The CLA based on a quadratic programming algorithm has already been experimentally validated during the TCV tokamak RT-04 experimental campaign. When designing a scenario, the plasma evolution must also account for the heat fluxes impacting the machine, as the distribution of these fluxes on the first wall is closely tied to the plasma's magnetic characteristics. The thermal model used to numerically program the scenario is subject to modeling errors, and it is expected that these will be better characterized during the early stages of commissioning. This introduces the risk that pre-programmed scenarios could surpass the desired temperature, necessitating scenario adjustments to meet specifications. To address this, we propose a first wall temperature controller, consisting of an outer loop integrated with the classical magnetic control architecture, which applies limited plasma shape and active current variations to reduce heat fluxes as needed. This approach, with limited online plasma corrections, could prevent delays due to scenario re-tuning. Additionally, the control strategy can be applied during full-power plasma operation, where plasma power and heat fluxes are expected to be significantly higher
Linear vs. Machine Learning Approaches for Cross-Temporal Forecast Reconciliation with an Application to Italian Energy Load Data
No full textAccurate electricity load forecasting is crucial for efficient power grid management. Forecast reconciliation has emerged as a key technique to improve forecast coherence and accuracy, particularly within hierarchical and constrained time series frameworks. This paper compares linear and machine learning (ML) approaches for cross-temporal forecast reconciliation, focusing on Italian energy load data. The study evaluates the performance of both methods, emphasizing the role of covariance matrix estimation in forecast accuracy. Our results, measured using the Mean Absolute Scaled Error (MASE), indicate that linear reconciliation methods, when incorporating validation errors for covariance estimation, outperform machine learning-based alternatives, highlighting the importance of enhanced error estimation in forecasting. The findings provide insights into the trade-offs between model complexity and predictive accuracy, offering valuable implications for energy demand forecasting and broader time series reconciliation applications
Nonlinear model predictive yaw moment control through electric axle and friction brake torque distribution
Get PDFNegative pressure pulmonary edema and hemorrhage after near fatal suffocation in an infant: a case report
Get PDFBackground: Pulmonary hemorrhage is rare but potentially life-threatening in children. Many causes are usually described, as cardiogenic, infective or immune. Pulmonary hemorrhage related to negative pressure pulmonary edema (NPPE) is uncommon in the pediatric population and there is limited literature about it. This is one of the few case reports regarding NPPE in infants presenting with pulmonary hemorrhage. Case presentation: We describe the story of a 6-weeks-old boy who presented epistaxis and hemoptysis associated with symptoms related to NPPE after near fatal suffocation. Radiological findings were consistent with alveolar hemorrhage. Supportive therapy was performed, with clinical recovery within a few days and radiological normalization within one month. Conclusion: NPPE associated with pulmonary hemorrhage is a dramatic condition but usually has a quick recovery with just supportive therapy. The aim of our report is to increase the awareness and emphasizes the importance of including this entity in the differential diagnosis of pulmonary hemorrhage in children with a suspicious anamnestic history of upper airway obstruction
Beyond the Enviro-toon - The Ecocritical Theme in contemporary Animated Seriesfor TV and OTT Media Services
Get PDFIn 2011, Robin Murray and Joseph Heumann proposed an ecocritical reading of US animated production, further focusing on the definition of enviro-toon. It is a category that frames the dominant narrative models in US animation, introduced in 2004 by Jaime Weinman to distinguish superficially moralistic products from those animated works where, although the ecological theme is central, easy schematisations are not used (where 'good' would coincide with nature conservation, and 'evil' with pollution and the like), but a complex stratification of perspectives is created, and conclusions remain open. These are what, in 2012, Deidre Pike more precisely identified as dialogical enviro-toons.
In the contemporary panorama of animation, though, the fictional serial products distributed by OTT media services seem to be implementing new discursive strategies about ecocritical issues, which are in turn also influencing TV serial animation. The ecological topic is often not the main force driving the narrative, but just one major thread within a more complex thematic texture. This is especially evident in the so-called “adult”-targeted animation, a marketing label introduced since the early 2000s in Western animation (for example by the night programming of Cartoon Network, called Adult Swim) to differentiate the serial products covering more sensible themes, like violence or sensuality, from the “regular” ones, supposedly targeted to children. While this labelling unfortunately perpetuates longstanding stereotypes about the perception of animation in the Western audience, the exploration of the so-called “adult” audience has fostered the development of series with a complex writing and a matching refined design and visual research. Among the series that cleverly embed ecocritical issues in their narratives, without being literal enviro-toons, are the Adult Swim Primal (2019-present), by Genndy Tartakovsky, as well as several episodes of Love, Death & Robots (2019-present), based on a strong critical interplay between thematic content and visual style.
The article analyses these series, to discuss how they challenge and expand the notion of enviro-toon
Effects of Ribbed Blades on the Aerodynamic Performance of a Controlled Vortex Design Tube-Axial Fan
No full textLeading-edge bumps, serrations, and trailing-edge indentations are commonly used to improve fan stall margin
and mitigate noise emissions. However, these modifications often contribute to a reduction in aerodynamic performance at the design point. This paper aims to quantify the degree of confinement imposed on the meridional flow within the rotor passages by incorporating chordwise-aligned bumps, referred to here as ribs, on the blade surface. To this end, the aerodynamic performance of three fan configurations is investigated using validated CFD and analyzed in relation to local flow features. The baseline fan has a hub-to-tip ratio of 0.5 and an aerodynamic loading distribution characterized by a nearly constant exit swirl component. The second fan
incorporates a spanwise-uniform distribution of ribs extending from the leading edge to the trailing edge across the entire blade surface. The third fan features the same ribs as the second but is designed to meet the same requirements as the baseline fan, with its design process neglecting the radial flow migration typically imposed by radial equilibrium in controlled vortex blade designs. The fans equipped with blades modified with five ribs matched the aerodynamic performance of the baseline fan, with a significant improvement observed at reduced flow rates and near-stall conditions
Tra pianura e Prealpi: pecore, agricoltori e transumanze
No full textIl sistema di allevamento e transumanza tra le pianure e le Prealpi venete ha rappresentato un eccellente esempio di dinamica economica tra l'età antica e il Medioevo. Le greggi svernavano in pianura per trascorrere lunghi mesi presso i pascoli d'altura, la cui verdeggiante vegetazione garantiva ottime produzioni di lana per le manifatture patavine, note dalle fonti antiche e medievali
