Selective excitations of trasverse vibrational modes of a carbon nanotube through a "shuttle-like" electromechanical instability

We study the dynamics of transverse oscillations of a suspended carbon nanotube into which current is injected from the tip of a scanning tunneling microscope (STM). In this case the correlations between the displacement of the nanotube and its charge state, determined by the position-dependent electron tunneling rate, can lead to a "shuttle-like" instability for the transverse vibrational modes. We find that selective excitation of a specific mode can be achieved by an accurate positioning of the STM tip. This result suggests a feasible way to control the dynamics of this nano-electromechanical system (NEMS) based on the "shuttle instability".Comment: revised version, 5 pages, 3 figure

Identificazione di modello di un pneumatico aeronautico in frenata

Oggetto della presente tesi di laurea è lo studio della dinamica longitudinale di pneumatici radiali di impiego aeronautico in condizioni di frenata su macchina dinamometrica. Obiettivo principale è l’identificazione dei parametri di un modello del pneumatico, elaborato in precedenti attività di ricerca, finalizzata a minimizzare le differenze tra le risposte simulate e quelle misurate sperimentalmente nel corso di prove di frenata su macchina dinamometrica. Un secondo obiettivo consiste nel rivedere criticamente il modello esistente e nel formularne uno nuovo a partire da ipotesi alternative. Il nuovo modello sfrutta interamente la capacità di identificazione automatica dei parametri in quanto è più complesso e i suoi parametri, svincolati dalla fisica del problema, non sono identificabili manualmente

Semantic web approach for italian graduates' surveys: the AlmaLaurea ontology proposal

Il crescente sviluppo e la promozione della trasparenza dei dati nell’ambito della pubblica amministrazione copre molteplici aspetti, fra cui l’educazione universitaria. Attualmente sono difatti numerosi i dataset rilasciati in formato Linked Open Data disponibili a livello nazionale ed internazionale. Fra le informazioni pubblicamente disponibili spiccano concetti riguardo l’occupazione e la numerosità dei laureati. Nonostante il progresso riscontrato, la mancanza di una metodologia standard per la descrizione di informazioni statistiche sui laureati rende difficoltoso un confronto di determinati fatti a partire da differenti sorgenti di dati. Sul piano nazionale, le indagini AlmaLaurea colmano il gap informativo dell’eterogeneità delle fonti proponendo statistiche centralizzate su profilo dei laureati e relativa condizione occupazionale, aggiornate annualmente. Scopo del progetto di tesi è la realizzazione di un’ontologia di dominio che descriva diverse peculiarità dei laureati, promuovendo allo stesso tempo la definizione strutturata dei dati AlmaLaurea e la successiva pubblicazione nel contesto Linked Open Data. Il progetto, realizzato con l’ausilio delle tecnologie del Web Semantico, propone infine la creazione di un endpoint SPARQL e di una interfaccia web per l'interrogazione e la visualizzazione dei dati strutturati

Suppression of stochastic fluctuations of suspended nanowires by temperature-induced single-electron tunnelling

We investigate theoretically the electromechanical properties of freely suspended nanowires that are in tunnelling contact with the tip of a scanning tunnelling microscope (STM) and two supporting metallic leads. The aim of our analysis is to characterize the fluctuations of the dynamical variables of the nanowire when a temperature drop is mantained between the STM tip and the leads, which are all assumed to be electrically grounded. By solving a quantum master equation that describes the coupled dynamics of electronic and mechanical degrees of freedom we find that the stationary state of the mechanical oscillator has a Gaussian character, but that the amplitude of its root-mean square center-of-mass fluctuations is smaller than would be expected if the system were coupled only to the leads at thermal equilibrium.Comment: Published versio

Comparison of short-stretch bandage and long-stretch bandage for post-traumatic hand edema

Introduction and importance: Hand edema is a common post-surgical or traumatic complication in orthopedic patients, necessitating effective treatment interventions. This study aimed to investigate the effects of two different types of bandages, along with finger flexion exercises, on managing hand edema. Case presentation: Our orthopedic patients with post-surgical or traumatic hand edema and three non-edematous hands were enrolled in the study. A mixed model effect with fixed factors of time (pre-post) and bandage type (M, C, N), and random factors of hand, edema, fingers, and phalanges was applied. The bandage types were circular with short elastic bandage (M) and circular with elastic bandage (C). Finger flexion exercises involved alternating contractions of extrinsic and intrinsic flexors. Randomization ensured unbiased allocation to bandage types. Clinical discussion: The M bandage demonstrated a significant reduction in hand edema by effectively moving free fluids, reinforcing tissue hydrostatic pressure, and facilitating venous and lymphatic flow. On the other hand, the C bandage did not produce significant pre-post differences in hand circumference. Conclusions: The combination of a circular bandage with finger flexion exercises shows promise in reducing hand edema in orthopedic patients. Particularly, the stiff bandage M exhibited superior efficacy compared to the elastic one C in reducing hand circumference. These findings provide valuable insights for clinical practice, offering an effective strategy for managing hand edema and promoting better patient outcome

Statistical learning of target and distractor spatial probability shape a common attentional priority computation

Converging evidence recently put forward the notion that dedicated neurocognitive mechanisms do exist for the suppression of salient, but irrelevant distractors. Along this line, it is plausible to hypothesize that, in appropriate contexts, experience-dependent forms of attentional learning might selectively induce plastic changes within this dedicated circuitry, thus allowing an independent shaping of priorities at the service of attentional filtering. Conversely, previous work suggested that statistical learning (SL) of both target and distractor spatial probability distributions converge in adjusting only the overall attentional priority of locations: in fact, in the presence of an independent manipulation, either related to the target or to the distractor only, SL induces indirect effects (e.g., changes in filtering efficiency due to an uneven distribution of targets), suggesting that SL-induced plastic changes affect a shared neural substrate. Here we tested whether, when (conflicting) target- and distractor-related manipulations are concurrently applied to the very same locations, dedicated mechanisms might support the selective encoding of spatial priority in relation to the specific attentional operation involved. In three related experiments, human healthy participants discriminated the direction of a target arrow, while ignoring a salient distractor, if present; both target and distractor spatial probability distributions were concurrently manipulated in relation to each single location. Critically, the selection bias produced by the target-related SL was marginally reduced by an adverse distractor contingency, and the suppression bias generated by the distractor-related SL was erased, or even reversed, by an adverse target contingency. Our results suggest that even conflicting target- and distractor-related SL manipulations result in the adjustment of a unique spatial priority computation, likely because the process directly relies on direct plastic alterations of shared spatial priority map(s)

Charge transfer and trapping as origin of a double dip in the transfer characteristics of graphene based field-effect transistors

We discuss the origin of an additional dip other than the charge neutrality point observed in transfer characteristics of graphene-based field-effect transistors. The double-dip is proved to arise from charge transfer between graphene and metal electrodes, while charge storage at the graphene/SiO2 interface enhances it. Considering different Fermi energy from the neutrality point along the channel and partial charge pinning at the contacts, we propose a model which explains all features in gate voltage loops.Comment: 14 pages, 5 figure

An investigation on the 'width and size effect' in the evaluation of the fracture energy of concrete

The parameters that describe the fracture behavior of concrete are crucial to investigate numerically the response of reinforced concrete (RC) structures. Among them, the fracture energy plays a key role in all those applications that aim to simulate the behavior of RC structures. The fracture energy is a characteristic property of a material but its experimental evaluation could be difficult for quasi-brittle materials such as concrete due to the "width effect" and "size effect" that can lead to some uncertainties in the definition of this parameter. This study presents the results of an experimental campaign conducted on notched specimens to evaluate the fracture energy of concrete. Concrete prisms with different sizes were tested using a three-point bending (TPB) set-up to evaluate the influence of the width and the size on the results. The setup has been designed to become potentially part of the ACI 446 report on fracture. Digital image correlation (DIC) was used to qualitatively and quantitatively study the strain field near the crack tip. Preliminary numerical simulations were performed to investigate the "width effect" in a discrete element framework. Copyright (C) 2017 The Authors. Published by Elsevier B.V

Experimental Perfect Quantum State Transfer

The transfer of data is a fundamental task in information systems. Microprocessors contain dedicated data buses that transmit bits across different locations and implement sophisticated routing protocols. Transferring quantum information with high fidelity is a challenging task, due to the intrinsic fragility of quantum states. We report on the implementation of the perfect state transfer protocol applied to a photonic qubit entangled with another qubit at a different location. On a single device we perform three routing procedures on entangled states with an average fidelity of 97.1%. Our protocol extends the regular perfect state transfer by maintaining quantum information encoded in the polarisation state of the photonic qubit. Our results demonstrate the key principle of perfect state transfer, opening a route toward data transfer for quantum computing systems