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Aerodynamic interaction of side-by-side propellers in forward flight operating at low-Reynolds numbers
Get PDFAn experimental investigation is conducted to study the interaction of side-by-side propellers operating in forward flight at low Reynolds numbers. The effect on performance is first evaluated by means of load cell measurements, while the flow field is studied employing a stereoscopic particle image velocimetry (SPIV) setup. Three different configurations are tested: single propeller, co-rotating and counter-rotating cases at varying advance ratios. The results indicate that the performance of the single propeller is decreased due to aerodynamic interaction, leading to an average 3.2% reduction in propulsive efficiency, evaluated across all the tested operating conditions. The effect is stronger at lower advance ratios, owing to a greater interaction between the two streamtubes in such conditions. SPIV measurements indicate a widening of the wake as well as a reduction in the turbulence intensity for the cases with two propellers, with a stochastic fluctuations approximately 15% lower for the twin propeller cases than the single propeller. The data is then sorted and phase-ordered a posteriori via a data-driven approach, effectively reconstructing phase-averaged flow fields. This enables the decomposition of the velocity field into phase-correlated and purely turbulent components. The results show that the stochastic (turbulent) component of the velocity field increases when the propellers operate at advance ratios different from the maximum efficiency condition
Using airborne LiDAR to quantify changes in forest structure following an ice storm disturbance and subsequent salvage logging
Get PDFIce storms are common disturbance agents in temperate forests, often causing complex damage by partially destroying tree crowns. These irregular damage patterns pose challenges in production forests. Post-disturbance management decisions, such as salvage logging, are typically based on hastily collected field data, which is costly, time-consuming, and often fails to capture damage heterogeneity. Remote sensing offers a practical alternative. In 2014, a severe ice storm damaged mixed forests across the northern Dinaric Mountains. We used multitemporal high-density Airborne Laser Scanning data to validate a procedure for quantifying ice storm damage in stands dominated by Norway spruce, silver fir and European beech, using field data as a reference. LiDAR-derived leaf area density profiles and voxel-based biomass loss estimates effectively reflected field-observed patterns. Methods based on individual-tree segmentation underestimated post-disturbance tree density reductions, but basal area and volume loss estimates aligned closely with field measurements, even at low point densities. These methods offer a scalable approach to damage assessment and improve understanding of the spatial variability of ice storm impacts. They also hold considerable promise for land managers with access to regional bitemporal LiDAR datasets
Fare geografia giuridica. Un'analisi delle catene di attori nella produzione di legge e spazio nel diritto amministrativo in materia di edilizia di culto
No full textSulla scorta dei recenti contributi teorici sulla geografia giuridica in Italia, questo articolo ne propone un'applicazione pratica volta ad analizzare gli attori coinvolti nella produzione del diritto. A partire dal caso studio dei luoghi di culto islamici in Italia, e attraverso un'analisi sistematica dei contenziosi amministrativi sul tema dal 2009 al 2024 in Lombardia, lo studio rileva l'atteggiamento prolungato di accettazione acritica da parte dei giudici dei verbali di polizia durante i processi. L'uso, spesso banalizzato, di questi documenti (prodotti da agenti il cui operato è fortemente discrezionale e condizionato da pressioni gerarchiche, aspettative dei cittadini e senso del dovere) attribuisce un potere rilevante alla polizia locale. Ne risulta che quest'ultima emerge talvolta come un attore centrale nel processo giuridico e, di conseguenza, nella trasformazione dello spazio urbano
MAdaKron: a Mixture-of-AdaKron Adapters
Get PDFAdapting pre-trained Large Language Models to specific tasks has traditionally involved updating all of their parameters. Nonetheless, this technique becomes impractical for models containing billions of parameters. This has led to intensive research on Parameter-Efficient Fine-Tuning (PEFT) techniques, which aim to train a small fraction of the model’s parameters while maintaining comparable performance to Full Fine-Tuning. A popular method is the Adapter, i.e. small trainable layers added to pre-trained models. Recently, we present AdaKron, an Adapter-based PEFT technique, which leverages the Kronecker product to combine the outputs of two small networks, training less than 0.55% of the model’s parameters while outperforming Full Fine-Tuning. In this paper, we put forward a novel technique, called MAdaKron, a Mixture-of-AdaKron model, which combines AdaKron with a Mixture of Experts approach. MAdaKron combines the flexibility of a Mixture of Experts architecture with the efficiency given by AdaKron to further enhance its performance. We then extensively evaluate MAdaKron on eighteen Natural Language Understanding and Generation benchmarks, showing that it achieves performance on par or even better than recent state-of-the-art PEFT methods, while reducing the number of trainable parameters. These findings highlight MAdaKron as an efficient solution for Fine-Tuning LLMs, offering substantial computational cost reductions without losing performance
SrCoO3-δ and SrCo1-xTixO3-δ perovskites as electrocatalytic materials for oxygen evolution reaction in alkaline environment
Get PDFHere, we report the deposition of SrCoO3-δ perovskites thin films by chemical bath deposition, employed as electrocatalytic layers for oxygen evolution reaction (OER) in alkaline water splitting. The effect of Co excess and Ti-doping on the crystalline structure, composition and electrochemical performances was investigated. The former had effect only on electrochemical performance whilst Ti-doping, above 3 %, induced the formation of a secondary phase. Among all the investigated samples, SrCoO3-δ:Co3O4 (SCO:CB) sample showed the best electrochemical performance toward OER in 1 M KOH aqueous solution, reporting an onset overpotential, ηonset, of 284 mV and a Tafel slope of 59 mV dec 1. In contrast, Ti-doping (i.e. 3 %, SCT:CB 3 sample) drastically improved stability of the electrocatalytic layer, enabling 24 h of continuous operation, demonstrating the effectiveness of doping strategy to enhance SrCoO3-δ perovskites durability. XPS analyses revealed that degradation of electrochemical performance of thin films is related to Sr leaching, even if Ti-doping decreased leached Sr amount improving layers stability
A 3D Camera-Based Approach for Real-Time Hand Configuration Recognition in Italian Sign Language
No full textDeafness poses significant challenges to effective communication, particularly in contexts
where access to sign language interpreters is limited. Hand configuration recognition
represents a fundamental component of sign language understanding, as configurations
constitute a core cheremic element in many sign languages, including Italian Sign Lan-
guage (LIS). In this work, we address configuration-level recognition as an independent
classification task and propose a machine vision framework based on RGB-D sensing. The
proposed approach combines MediaPipe-based hand landmark extraction with normalized
three-dimensional geometric features and a Support Vector Machine classifier. The first
contribution of this study is the formulation of LIS hand configuration recognition as a
standalone, configuration-level problem, decoupled from temporal gesture modeling. The
second contribution is the integration of sensor-acquired RGB-D depth measurements into
the landmark-based feature representation, enabling a direct comparison with estimated
depth obtained from monocular data. The third contribution consists of a systematic exper-
imental evaluation on two LIS configuration sets (6 and 16 classes), demonstrating that the
use of real depth significantly improves classification performance and class separability,
particularly for geometrically similar configurations. The results highlight the critical role
of depth quality in configuration-level recognition and provide insights into the design of
robust vision-based systems for LIS analysis
Design and optimization of a curved three-strap antenna for DTT ICRH system
Get PDFThe Divertor Tokamak Test facility (DTT) aims at demonstrating possible solutions to the power exhaust issue to pave the path to DEMO. Here we present the numerical design and optimization of a threestrap Ion Cyclotron Resonance Heating (ICRH) antenna suitable to deliver Ion Cyclotron Radio Frequency (RF) Power on DTT plasmas. The launcher operates in the frequency range 60– 90 MHz and here has been studied and optimized by using the commercial RF simulation software CST Studio Suite. The plasma is considered as an equivalent, high permittivity, lossy dielectric. Considering the mechanical and operational severe constraints of DTT, we firstly designed an antenna flat model with the objectives to optimize the structure for coupling a power ≥ 1.5 MW to the dielectric load with a progressive phase shift of 180◦ between toroidally adjacent straps. The second part of the work regarded the design and optimization of a parametric curved antenna model in CST, which employs poloidal and toroidal curvatures suitable to better couple RF to DTT plasmas. The antenna curved model has been re-optimized in terms of coupled power and electric field values to match DTT requirements
Analysis of high-temperature degradation mechanisms at the interface between bismuth telluride and metals and their effect on contact resistance increase
No full textInterfacial reliability of thermoelectric generation (TEG) devices with multilayered material structure is a crucial factor affecting conversion efficiency and device reliability. Previous work demonstrated that specific contact resistivity (ρc) between barrier metals/Bi2Te3 interfaces increased with temperature. Furthermore, results showed that the Ti/Bi2Te3 interface had the lowest ρc at 298 K, whereas the Ni/Bi2Te3 interface exhibited the lowest ρc at 378 K. To investigate the cause of the temperature dependence of ρc with barrier metals, we analyzed several interfacial phenomena after the measurement at 298 and 378 K. As a result,
Ag diffusion into Bi2Te3, distortion of the barrier metal, and interfacial alloying were observed under the high temperature. These interfacial degradation phenomena were attributed to thermal stresses. Additionally Ag diffusion increased in the order of Ni < Ti < Cr. Therefore, the results of this study provide unique insights into the degradation mechanisms of material interfaces in TEG devices under high-temperature conditions and clarify the relationships between interfacial deterioration and specific contact
resistivity increases
Turbulence-distortion modelling for Amiet’s theory enhancement
Get PDFWhen applied to aerofoils with non-negligible thickness, Amiet’s theory for turbulence-interaction noise prediction does not account for the alterations in the velocity field and acoustic response induced by the surface, resulting in an overestimation of the radiated noise. This study proposes a semi-analytical method that models turbulence distortion in the immediate vicinity of the surface starting from upstream flow conditions and considers the resulting effects on the acoustic response of the aerofoil. The distorted spectrum of the upwash velocity component is calculated using the asymptotic results of the rapid distortion theory (RDT) for very large- and small-scale turbulence, overcoming the need to define a representative location where turbulence characteristics are sampled. This distorted spectrum is characterised by an increased energy content that is encompassed in the model by scaling the analytical flat-plate formulation of the aeroacoustic transfer function. The proposed approach relies on defining the aerofoil geometrical feature that affects distortion mechanisms, required to extend the RDT results to such geometries. This parameter is identified as the path travelled by the turbulent eddies from the stagnation point to the position of maximum surface-pressure fluctuations, which is, in turn, related to flow acceleration and leading-edge sharpness. The accuracy of this methodology in enhancing noise prediction is demonstrated using numerical and experimental data of grid-generated turbulence interacting with different aerofoils
Personalized multiscale modeling of coronary plaque progression: the interaction between low-density-lipoprotein transport and cellular dynamics
Get PDFMultiscale agent-based modeling has shown promise in elucidating the mechanobiological mechanisms underlying atherosclerotic plaque formation and progression. However, the integration of advanced models of low-density lipoprotein (LDL) transport in the lumen and across the endothelium with agent-based models (ABMs) of plaque growth remains underexplored. Furthermore, patient-specific applications are lacking. This study introduces a novel agent-based modeling framework for atherosclerosis, integrating hemodynamics and LDL transport in the lumen through computational fluid dynamics simulations, a three-pore model of trans-endothelial LDL migration, and an ABM of lipid and cellular dynamics. For the first time, the framework was applied to a patient-specific coronary artery and validated against 1-year follow-up data. Furthermore, it was used to explore potential plaque evolution over 5 years and under elevated LDL concentration. The calibrated model predicted the 1-year variation in wall area in two patient-specific coronary cross-sections with an error of less than 10%. Simulated scenarios indicated that variations in blood LDL concentrations can result in distinct plaque morphologies, from localized to diffuse patterns. This study provided an innovative, advanced multiscale model of atherosclerotic plaque formation and progression. As the first patient-specific application of a multiscale agent-based modeling framework for atherosclerosis with initial validation, this study underscored the potential of the approach for deciphering the mechanobiological pathways driving coronary plaque progression. The developed model provided valuable insights into how the interplay between LDL transport and hemodynamics influences arterial wall cellular dynamics in a patient-specific context