Rotor loads prediction via virtual sensors : blending physics and AI

LAUREA MAGISTRALEQuesto lavoro di tesi presenta un approccio innovativo per la previsione dei carichi del rotore tramite sensori virtuali che combinano modellazione basata sulla fisica e tecniche di intelligenza artificiale (AI). La novità nell'approccio proposto consiste nel ricostruire i carichi (in questo lavoro il carico del dispositivo di smorzamento lead-lag) mediante la fusione delle previsioni AI dei parametri aeromeccanici come l'assetto del rotore con il modello fisico del dispositivo di smorzamento del rotore proveniente da [75]. Come ben sappiamo, i componenti meccanici del rotore sono soggetti a degradazione, che causa danni progressivi e perdita di funzionalità. Ciò è principalmente causato dai carichi, dalle vibrazioni e dagli spostamenti relativi che questi sistemi subiscono. Per stimare la vita utile residua del componente e il suo stato attuale di usura, la prognosi svolge un ruolo chiave. Tuttavia, per ottenere la prognosi, è necessaria la conoscenza delle cause di tale degradazione. La menzionata conoscenza può essere ottenuta mediante il rilevamento dei carichi e degli spostamenti dei componenti. Una stima di tali parametri potrebbe essere ottenuta installando sensori convenzionali in aree chiave, che potrebbero risultare tuttavia difficili da raggiungere. Inoltre, l'implementazione di tali sensori è costosa e richiede tempo, entrando in conflitto con l'obiettivo originale di ottimizzare le operazioni di manutenzione. I sensori virtuali consentono un'implementazione teorica di tale tecnologia mediante una ricostruzione dei carichi e degli spostamenti. L'implementazione di un approccio basato sui dati ha dimostrato di essere un percorso praticabile, come dimostrato da studi precedenti. Inoltre, l'uso di previsioni basate sulla fisica di tali quantità consente una spiegazione più affidabile con lo scopo ultimo di consentire in futuro non solo un'implementazione teorica, ma anche pratica e certificabile della prognostica. I modelli basati sulla fisica catturano i principi fondamentali della meccanica dei componenti dell'elicottero, mentre gli algoritmi AI apprendono dai dati storici per migliorare l'accuratezza delle previsioni degli spostamenti delle pale. Il lavoro di tesi fornisce una descrizione dettagliata del processo di sviluppo dei sensori virtuali, compresa la selezione delle variabili di input, la formulazione del modello e la stima dei parametri. L'efficacia dell'approccio proposto sarà dimostrata attraverso i risultati delle simulazioni, che mostrano che i sensori virtuali possono prevedere i carichi dei componenti del rotore. Il lavoro si conclude evidenziando i vantaggi della combinazione di modellazione basata sulla fisica e tecniche di AI nello sviluppo di sensori virtuali per la previsione dei carichi del rotore.This thesis work presents a novel approach for rotor loads prediction via virtual sensors that blend physics-based modelling and artificial intelligence (AI) techniques. The novelty in the proposed approach is to reconstruct the loads (in this work the lead-lag damper load) by means of merging AI predictions of aeromechanical parameters such as rotor trim with the rotor damper physical model coming from [75]. As we may know, rotor mechanical components are subjected to degradation, causing progressive damage and loss of functionality. And this is mainly driven by, loads, vibratory and relative displacements that these system experience. In order to estimate the component's residual useful life and current state of wear, prognostics plays a key role. However, in order to achieve the prognostics, knowledge of the causes of such degradation is required. The mentioned knowledge can be qualified by sensing loads and displacements of components. An estimation of these parameters could be obtained by installing conventional sensors in key areas that however could be difficult to reach. Moreover, the implementation of such sensors is also costly and time-consuming, coming into conflict with the original purpose to optimize maintenance operations. Virtual sensors enable a theoretical implementation of such technology by means of a reconstruction of loads and displacements. Implementing a data-driven approach has shown to be a viable path as demonstrated in previous studies. Additionally, the use of physics-informed prediction of these quantities allows a more reliable explanation with the ultimate scope to enable in the future not just a theoretical, but a practical and certifiable implementation of prognostics. The physics-based models capture the fundamental principles of rotorcraft component mechanics, while the AI algorithms learn from historical data to improve the prediction accuracy of blade displacements. The thesis work provides a detailed description of the virtual sensor development process, including the selection of input variables, model formulation, and parameter estimation. The effectiveness of the proposed approach will be demonstrated through simulation results, which show that virtual sensors can predict rotor component loads. The work concludes by highlighting the advantages of blending physics-based modelling and AI techniques in virtual sensor development for rotor loads prediction

Exploring the Relationship between Childhood Interpersonal Violence, Cortisol Stress Response, and Stress Eating

Histories of childhood interpersonal violence have been linked to overweight and obesity in adulthood. Despite the fact that victimization experiences are likely to co-occur within individuals, few studies have examined poly-victimization in the context of overweight or obesity. The current study aimed to: (1) determine whether poly-victimization was associated with body mass index and waist circumference in a sample of undergraduate women, and (2) explore plausible physiological and behavioral mechanisms accounting for the relationship, specifically cortisol and ad libitum eating in response to laboratory stress. Undergraduate women from the University of Pittsburgh responded to an online survey measuring history of six different childhood victimization experiences: physical abuse, sexual abuse, peer violence,intimate partner violence, community violence, and witnessing violence. Ninety-two healthy women were recruited into 2 study groups (n = 48 with no history of childhood victimization [controls]; and n = 44 endorsing a history of 2 or more different types of childhood victimization [poly-victims]). Study protocol occurred 3 hours after lunch and included standardized laboratory stressors (public speech and math task) followed by a 30 minute relaxation period that included ad libitum access to snack foods with varying caloric density. Salivary cortisol was assessed at three points across the laboratory session. Women reporting poly-victimization had higher body mass index after adjusting for childhood socioeconomic status, family history of obesity, and alcohol use. The relationship was weaker with the outcome of waist circumference. Poly-victims did not eat more following stress, although poly-victims who perceived their performance as worse on the stress task consumed more calories, controlling for childhood socioeconomic status and hunger at study entry. Unexpectedly, poly-victims showed blunted cortisol response to the stress task compared to controls, after adjusting for childhood socioeconomic status and birth control use. Bootstrapping tests of mediation showed that neither cortisol response to stress nor stress eating were significant mediators in the relationship between childhood interpersonal violence and body mass index. In conclusion, results from the present study suggest that poly- victimization is a risk factor for body mass index, and cortisol and eating responses to stress do not appear to mediate the relationship

Giant amplification of Berezinskii-Kosterlitz-Thouless transition temperature in superconducting systems characterized by cooperative interplay of small-gapped valence and conduction bands

Two-dimensional superconductors and electron-hole superfluids in van der Waals heterostructures having tunable valence and conduction bands in the electronic spectrum are emerging as rich platforms to investigate novel quantum phases and topological phase transitions. In this work, by adopting a mean-field approach considering multiple-channel pairings and the Kosterlitz-Nelson criterion, we demonstrate giant amplifications of the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature and a shrinking of the pseudogap for small energy separations between the conduction and valence bands and small density of carriers in the conduction band. The presence of the holes in the valence band, generated by intra-band and pair-exchange couplings, contributes constructively to the phase stiffness of the total system, adding up to the phase stiffness of the conduction band electrons that is boosted as well, due to the presence of the valence band electrons. This strong cooperative effect avoids the suppression of the BKT transition temperature for low density of carriers, that occurs in single-band superconductors where only the conduction band is present. Thus, we predict that in this regime, multi-band superconducting and superfluid systems with valence and conduction bands can exhibit much larger BKT critical temperatures with respect to single-band and single-condensate systems.Comment: 9 pages, 5 figure

Childhood Abuse and Neglect as Risk Factors for Central Adiposity: A Test of Association and Mediation Pathways

Childhood abuse and neglect are traumatic early-life stressors that may be risk factors for central adiposity. Our objective was to examine the association between childhood abuse/neglect and central adiposity and obesity in a sample of 311 women (106 Black, 205 White) from the Pittsburgh site of the Study of Women's Health Across the Nation (SWAN). SWAN included a baseline measurement of women in midlife (mean age = 45.7) and 8 follow-up visits during which waist circumference (WC) and body mass index (BMI) were measured. The Childhood Trauma Questionnaire, given at visit 8, retrospectively assessed 5 domains of abuse and neglect in childhood and adolescence: emotional, physical, and sexual abuse; emotional and physical neglect. ANCOVAs were used to determine whether a history of any abuse/neglect, or each type of abuse or neglect, was associated with WC, controlling for age. Results showed that women with a history of any abuse/neglect had significantly higher WC at visit 8 than women with no abuse history (M = 90.8, SE = 1.2; M = 96.1, SE = 1.5; F(1, 308)= 7.7, p = .01). Of the specific types of abuse, only physical abuse was significantly related to WC at visit 8 (M = 91.7, SE = 1.0; M = 97.9, SE = 2.3; F(1,308)=6.2, p = .01)]. Analyses for the outcome of BMI showed similar results, with the addition of sexual abuse being important for obesity. Histories of any abuse/neglect, or specific types of abuse or neglect, were not associated with increased WC from baseline to visit 8 in the full sample. However, among normal-weight and overweight women, a history of any abuse/neglect, emotional abuse, physical abuse, sexual abuse, or physical neglect predicted increased WC over time. Additional mediation analyses showed that Trait Anger scores mediated some relationships between abuse/neglect and WC. This study suggests that traumatic early-life stressors are associated with adulthood body fat distribution, especially among normal-weight and overweight women. Supported by NIH/DHHS AG012546 and MHO59689. The content of this abstract is solely the responsibility of the authors and does not necessarily represent the official views of the NIA, NIMH, or the NIH

Pairing amplification induced by nonadiabatic effects on the electron-phonon interaction throughout the BCS-BEC crossover

Nonadiabatic effects in the electron-phonon coupling are important whenever the ratio between the phononic and the electronic energy scales, the adiabatic ratio, is non negligible. For superconducting systems, this gives rise to additional diagrams in the superconducting self-energy, the vertex and cross corrections. In this work we explore these corrections in a two-dimensional single-band system through the crossover between the weak-coupling BCS and strong-coupling Bose-Einstein regimes. By focusing on the pseudogap phase, we identify the parameter range in which the pairing amplitude is amplified by nonadiabatic effects and map them throughout the BCS-BEC crossover. These effects become stronger as the system is driven deeply in the crossover regime, for phonon frequencies of the order of the hopping energy and for large enough electron-phonon coupling. Finally, we provide the phase space regions in which the effects of nonadiabaticity are more relevant for unconventional superconductors.Comment: 11 pages, 5 figure

Thiol-Ene Photo-Click Hydrogels with Tunable Mechanical Properties Resulting from the Exposure of Different -Ene Moieties through a Green Chemistry

Temperature and light responsiveness are widely exploited stimuli to tune the physico-chemical properties of double network hydrogels. In this work, new amphiphilic poly(ether urethane)s bearing photo-sensitive moieties (i.e., thiol, acrylate and norbornene functionalities) were engineered by exploiting the versatility of poly(urethane) chemistry and carbodiimide-mediated green functionalization procedures. Polymers were synthesized according to optimized protocols maximizing photo-sensitive group grafting while preserving their functionality (approx. 1.0 × 10E19, 2.6 × 10E19 and 8.1 × 10E17 thiol, acrylate and norbornene groups/gpolymer), and exploited to prepare thermo- and Vis-light-responsive thiol-ene photo-click hydrogels (18% w/v, 1:1 thiol:ene molar ratio). Green light-induced photo-curing allowed the achievement of a much more developed gel state with improved resistance to deformation (~60% increase in critical deformation, γL). Triethanolamine addition as co-initiator to thiol-acrylate hydrogels improved the photo-click reaction (i.e., achievement of a better-developed gel state). Differently, L-tyrosine addition to thiol-norbornene solutions slightly hindered cross-linking, resulting in less developed gels with worse mechanical performances (~62% γL decrease). In their optimized composition, thiol-norbornene formulations resulted in prevalent elastic behavior at lower frequency compared to thiol-acrylate gels due to the formation of purely bio-orthogonal instead of heterogeneous gel networks. Our findings highlight that exploiting the same thiol-ene photo-click chemistry, a fine tuning of the gel properties is possible by reacting specific functional groups

Hemorrhagic pericarditis with cardiac tamponade after percutaneous coronary intervention associated with the use of abciximab

Glycoprotein (GP) IIb/IIIa inhibitors, such as abciximab, are used as adjunctive therapy for percutaneous coronary intervention (PCI) in high-risk non-ST-elevation myocardial infarction (NSTEMI) and in ST-elevation myocardial infarction (STEMI), although their effects when used for STEMI are less clear. As the use of GP IIb/IIIa inhibitors becomes more widespread, determining the risks associated with them becomes more important. The major risks associated with the use of GP IIb/IIIa inhibitors are the potential for major bleeding and thrombocytopenia. This is the first reported case in Korea of hemorrhagic pericarditis resulting in cardiac tamponade associated with the use of abciximab, a commonly used GP Ilb/IIa inhibitor, following PCI

Upper critical magnetic field and multiband superconductivity in artificial high-Tc superlattices of nano quantum wells

Artificial high-Tc superlattices (AHTS) composed of quantum building blocks with tunable superconducting critical temperature have been synthesized by engineering their nanoscale geometry using the Bianconi-Perali-Valletta (BPV) two gaps superconductivity theory. These quantum heterostructures consist of quantum wells made of superconducting, modulation-doped Mott insulators (S), confined by a metallic (N) potential barrier. The lattice geometry has been carefully engineered to induce the predicted Fano-Feshbach shape resonance between the gaps, near a topological Lifshitz transition. Here, we validate the BPV theory by providing compelling experimental evidence that AHTS samples, at the peak of the superconducting dome, exhibit resonant two-band, two-gap superconductivity. This is demonstrated by measuring the temperature dependence of the upper critical magnetic field,Bc2, in samples with superlattice periods 3.3<5.28 nm and L/d ratios close to the magic value 2/3 (where L is the thickness of the superconducting La2CuO4 layer and d is the superlattice period). The data reveal the predicted upward concavity in Hc2(T) and a characteristic kink in the coherence length as a function of temperature, confirming the predicted two-band superconductivity with Fermi velocity ratio 0.25 and significant pair exchange term among the two condensates