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Magnetoelastic actuated motion of fine ferromagnetic particles
No full textWireless magnetic actuation offers precise control over microscopic devices, yet full planar manipulation of rigid, tethered magnetic particles remains challenging. We introduce a minimal variational model: a permanently magnetized planar ellipse anchored by two linear springs. First, we derive exact geometric conditions under which the springs can be configured so that the ellipse rotates freely without elastic penalty -producing a continuous family of zero-energy equilibria in which the ellipse's centre traces a closed loop dictated solely by spring geometry. Next, we incorporate a uniform in-plane magnetic field and prove that the equilibrium magnetization aligns uniformly with the field. In the so-called full-controllability regime -when the spring rest lengths are long enough -rotating the external field directly prescribes the ellipse's orientation: the particle follows its zero-energy trajectory to maintain magnetic alignment, achieving a global energy minimum. For shorter springs, zero-energy configurations exist over a restricted orientation range; outside this range, the ellipse is pinned at the origin. Our results yield exact criteria for planar control in this simplest magnetoelastic setting, offering clear guidelines for the design of microscale actuators and metamaterials
Virtual Coupling Formation Control for Heterogeneous High-Speed-Trains With Uncertain Dynamics, Nonuniform Communication Delays and Switching Topologies
No full textThe Virtual Coupling (VC) control problem becomes more challenging when considering High-Speed Trains (HST), where unexpected/unpredictable external factors, nonlinearities effects and unavoidable communication impairments have a stronger impact on trains convoy performance and safety because of the higher velocity operative range. To simultaneously handle all these critical aspects in a unified framework, this paper proposes a novel robust distributed time-delay control strategy which ensures the VC of autonomous connected HST under variable inter-train spacing policy which accounts for the effective convoy conditions. This is also guaranteed in the presence of variations in the active communication links as a result of cooperative manoeuvres. By exploiting matrix theory and the Lyapunov-Krasovskii approach, we derive the control gains tuning procedure and the exponential stability conditions, which are expressed as a set of feasible delay-dependent Linear Matrix Inequalities. These latter allow analytically evaluating the stability margin of the VC convoy with respect to uncertainties, unmodeled dynamics and the maximum allowable delay upper bound, as well as ensuring, based on a desired exponential decay rate, that the closed-loop state trajectories remain bounded within a safe region. Theoretical derivation is confirmed by an extensive simulation campaign, also including different railways cooperative maneuvers, Monte Carlo analysis and comparative evaluation against an alternative strategy
Soot and nanoparticle formation in ethylene counterflow diffusion flames: effects of nitrogen dilution and strain rate
No full textStricter health regulations now cap sub-23 nm particle emissions from all combustion devices. High strain rate (α) and inert dilution each curb soot formation. To our knowledge, however, their combined effect on nanoparticle inception and soot growth has never been quantified in a single, well-characterised burner. To decouple these effects, we systematically investigated ethylene (C2H4) counterflow diffusion flames (CDFs) at three nitrogen (N2)-dilution levels (baseline SF21, and the more heavily diluted SF26 and SF18) while changing the α from 26 to 103 s−1. Dual-wavelength laser induced fluorescence UV-LIF (at 350 nm) and laser induced incandescence LII (at 500 nm) yielded spatially resolved nanoparticle and soot maps. Across all dilutions, increasing the α from 26 to 103 s−1 lowered the peak soot-volume fraction (SVF) by 78–82 % and reduced the maximum LII signal proportionally, confirming the sensitivity of soot growth to the residence time. Nanoparticle LIF behaved asymmetrically: in the fuel-rich (pyrolytic) zone, it fell by ≈ 30 %, whereas on the oxidizer side, it plunged by ≈ 62 %. At the same time, the axial location of the maximum rate of soot formation advanced about 1.0 ± 0.1 mm toward the stagnation plane (SP), and sectional modelling reproduced this shift within 15 %. Dilution amplified the strain-induced attenuation, especially in the oxidative zone, but alone could not match the reduction achieved at the highest α. Moderate N2 dilution combined with high α clarifies how reduced residence time and enhanced mixing jointly suppress nanoparticle inception and soot growth. Importantly, this approach does so without changing the fuel composition or compromising flame stability
Clinical presentation and echocardiographic characteristics of women with peripartum cardiomyopathy: Insights from the Italian Multicentre Registry
No full textBackground: Peripartum cardiomyopathy (PPCM) is a rare, life-threatening form of heart failure occurring in late pregnancy or postpartum, with variable clinical course and outcomes. We report preliminary clinical and echocardiographic findings from a national Italian registry of PPCM patients METHODS: The study was approved by the institutional Ethics Committee and registered at ClinicalTrials.gov (NCT05878041). Twenty-eight patients aged ≥18 years with confirmed PPCM diagnosis were included. At enrollment, all patients underwent clinical assessment, echocardiography, and peripheral blood sampling for multi-omics profiling. Results: Participants had a mean age of 33.9 ± 5.1 years and a median body mass index of 28 kg/m2 (25.5-32.9). Key characteristics of enrolled patients included African ethnicity (10.7 %), assisted reproduction (14.3 %), pre-eclampsia (14.3 %), autoimmune disease (10.7 %), hypertension (21.4 %), diabetes mellitus (3.5 %), and smoking (32.1 %). Most patients were diagnosed PPCM with NYHA class III/IV symptoms within one month postpartum; mean Left Ventricular Ejection Fraction (LVEF) at admission was 33.2 ± 9.3 %. Arrhythmic presentation occurred in 25 % of patients. Despite initial severity, 50 % of patients recovered LVEF over 11 ± 19 months, while persistent severe dysfunction (LVEF<35 %) requiring defibrillator implantation was observed in 14 % of patients. Several echocardiographic markers differed significantly in enrolled patients according to recovery status, and those with persistent dysfunction had larger LV end-diastolic diameters (61.2 ± 8.1 mm) and left atrial volumes (47.0 ± 24.7 ml/m2), lower LV strain (9.0 ± 1.4 %), and TAPSE (17.5 ± 4.2 mm, p < 0.005 for all). Conclusions: Clinical and echocardiographic predictors of LV recovery in PPCM need further investigation
A mechanistic predictive model for pressure drop and void fraction calculation in two-phase flows and annular flow regime
No full textThis paper presents a mechanistic model for predicting the pressure gradient and other relevant flow characteristics during annular two-phase flow, by introducing a novel physical interpretation of the enhancement of the friction factor at the vapor–liquid interface, as a function of the liquid to vapor core inertia forces ratio. This interpretation is demonstrated to be consistent with literature relating the interfacial friction factor to the equivalent sand roughness. An experimental database, consisting of 6377 annular flow data points, has been used to enlarge the range of operating conditions with mass velocities from 99 to 2000 kg m-2s−1, tube diameters from 0.5 to 14.0 mm, reduced pressures from 0.0363 to 0.6896 and frictional pressure drop values from 0.3 to 1332 kPa/m. The proposed method is able to predict pressure gradients with a mean absolute percentage error of 18 % and 83 % of data points falling within a ± 30 % error range. The method allows also the calculation of the void fraction with a good agreement with the Rouhani-Axelsson correlation
Verità storica e logica del “nonostante”. L’incontro tra Federico II e Leonardo Pisano nella riflessione storiografica
No full text[IT] L’articolo analizza il celebre incontro tra Federico II di Svevia e il matematico Leonardo Pisano (Fibonacci), tradizionalmente collocato a Pisa nei primi decenni del XIII secolo, come caso esemplare per riflettere sulle forme della conoscenza storica. A partire da fonti documentarie incerte e da interpretazioni divergenti, l’episodio viene esaminato secondo due principali prospettive epistemologiche. Da un lato, l’approccio abduttivo proposto da Andrea Bonaccorsi, che interpreta la ricostruzione dell’evento come un processo inferenziale fondato sulla plausibilità delle ipotesi e sul confronto critico con le fonti. Dall’altro, la lettura simbolica di Ernst Kantorowicz, per il quale l’incontro assume un valore figurale e diventa espressione della logica del “nonostante” (trotzdem), capace di cogliere la tensione tra necessità politica e libertà intellettuale nell’agire storico. Attraverso il dialogo con autori come Charles S. Peirce, Carlo Ginzburg, Heinrich Rickert, Max Weber e Reinhart Koselleck, il contributo mette in luce la pluralità delle razionalità che operano nella storiografia: quella ipotetico-critica, orientata alla verifica e alla plausibilità, e quella simbolico-ermeneutica, attenta alla configurazione narrativa e al significato dell’azione storica. L’episodio dell’incontro tra l’imperatore e il matematico diventa così una porta d’accesso privilegiata per indagare il rapporto tra evento, interpretazione e verità storica, mostrando come la scrittura della storia si sviluppi nella tensione tra spiegazione, immaginazione e costruzione di senso. [EN] This article examines the famous encounter between Emperor Frederick II and the mathematician Leonardo of Pisa (Fibonacci), traditionally dated to Pisa in the early thirteenth century, as a case study for reflecting on the forms of historical knowledge. Starting from uncertain documentary evidence and divergent interpretations, the episode is analysed through two main epistemological perspectives. On the one hand, the abductive approach proposed by Andrea Bonaccorsi interprets the reconstruction of the event as an inferential process based on the plausibility of hypotheses and their critical testing against historical sources. On the other hand, the symbolic interpretation developed by Ernst Kantorowicz reads the encounter as a figurative expression of the logic of trotzdem (“nonetheless”), capable of capturing the tension between political necessity and intellectual freedom in historical action. Engaging with thinkers such as Charles S. Peirce, Carlo Ginzburg, Heinrich Rickert, Max Weber, and Reinhart Koselleck, the article highlights the plurality of rationalities at work in historiography: an abductive-critical rationality oriented toward verification and plausibility, and a symbolic-hermeneutic rationality attentive to narrative configuration and historical meaning. The episode of the meeting between the emperor and the mathematician thus becomes a privileged entry point for exploring the relationship between event, interpretation, and historical truth, showing how historical writing develops within the tension between explanation, imagination, and the construction of meaning
High order nonstandard finite-difference methods
No full textNonstandard finite difference (NSFD) methods have been considered to overcome some issues of standard methods, particularly when the numerical solution must preserve important properties of the exact solution. These issues increase for high order methods. In this paper we first derive a general procedure to obtain unconditionally positive second order NSFD methods. Furthermore, by suitably adding some parameters αi within these schemes, we show that it is still possible to get positivity, and also to preserve other qualitative properties of the exact solution. In fact, for each particular problem we can get optimal values of αi that guarantee positivity, elementary stability and the minimization of the local truncation error, being possible to achieve also third order nonstandard schemes, which are not present in the literature. As an example of use, we employ the developed theory to derive positive and elementary stable NSFD methods of order one, two and three for a predator-prey model, showing their advantages over other nonstandard methods from the literature