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Low-temperature quantum transport in CVD-grown single crystal graphene

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Nano Research 2016年第6期9卷 1823-1830页

作者： Shaohua Xiang Vaidotas Miseikis Luca Planat stefano Guiducci stefano Roddaro Camilla Coletti Fabio Beltram Stefan Heun NEST Istituto Nanoscienze--CNR and Scuola Normale Superiore Piazza San Silvestro 12 $6127 Pisa Italy Center for Nanotechnology Innovation @NEST Istituto Italiano di Tecnologia Piazza San Silvestro 12 56127 Pisa Italy

Chemical vapor deposition （CVD） is typically used for large-scale graphene synthesis for practical applications. However, the inferior electronic properties of CVD graphene are one of the key problems to be solved. Therefore, we present a detailed study on the electronic properties of high-quality single-crystal monolayer graphene. The graphene is grown via CVD on copper, by using a cold-wall reactor, and then transferred to Si/SiO2. Our low-temperature magneto-transport data demonstrate that the characteristics of the single-crystal CVD graphene samples are superior to those of polycrystalline graphene and have a quality which is comparable to that of exfoliated graphene on Si/SiO2. The Dirac point in our best samples occurs at back-gate voltages lower than 10 V, and a maximum mobility of 11,000 cm2/（V.s） is attained. More than 12 flat and discernible half-integer quantum Hall plateaus occur under a high magnetic field on both the electron and hole sides of the Dirac point. At a low magnetic field, the magnetoresistance exhibits a weak localization peak. Using the theory of McCann et al., we obtain inelastic scattering lengths of 〉1 um, even at the charge neutrality point of the samples.

关键词： high-quality chemicalvapor deposition (CVD)-graphene low-temperaturemagnetotransport quantum Hall effect weak localization

SPH numerical investigation of the characteristics of an oscillating hydraulic jump at an abrupt drop

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Journal of Hydrodynamics 2018年第1期30卷 106-113页

作者： Diana De Padova Michele Mossa stefano Sibilla Department of Civil Environmental Land Building Engineering and ChemistryPolytechnic University of Bari Department of Civil Engineering and Architecture University of Pavia

This paper shows the results of the smooth particle hydrodynamics（SPH） modelling of the hydraulic jump at an abrupt drop,where the transition from supercritical to subcritical flow is characterised by several flow patterns depending upon the inflow and tailwater conditions. SPH simulations are obtained by a pseudo-compressible XSPH scheme with pressure smoothing; turbulent stresses are represented either by an algebraic mixing-length model, or by a two-equation k-ε model. The numerical model is applied to analyse the occurrence of oscillatory flow conditions between two different jump types characterised by quasi-periodic oscillation,and the results are compared with experiments performed at the hydraulics laboratory of Bari Technical University. The purpose of this paper is to obtain a deeper understanding of the physical features of a flow which is in general difficult to be reproduced numerically,owing to its unstable character： in particular, vorticity and turbulent kinetic energy fields, velocity, water depth and pressure spectra downstream of the jump, and velocity and pressure cross-correlations can be computed and analysed.

关键词： Hydraulic jumps smoothed particle hydrodynamics(SPH) models oscillating characteristics

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A Generalised Lattice Boltzmann Equation on Unstructured Grids

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Communications in Computational Physics 2008年第2期3卷 342-356页

作者： stefano Ubertini Sauro Succi Universit`a degli Studi di Roma “Tor Vergata”Dip.Ingegneria MeccanicaVia del Politecnico10133 RomaItalia Istituto Applicazioni del Calcolo CNR Via del Policlinico13700161 RomaItalia.

This paper presents a new finite-volume discretization of a generalised LatticeBoltzmann equation (LBE) on unstructured grids. This equation is the continuumLBE, with the addition of a second order time derivative term (memory), and is derivedfrom a second-order differential form of the semi-discrete Boltzmann equationin its implicit form. The new scheme, named unstructured lattice Boltzmann equationwith memory (ULBEM), can be advanced in time with a larger time-step than the previousunstructured LB formulations, and a theoretical demonstration of the improvedstability is provided. Taylor vortex simulations show that the viscosity is the same aswith standard ULBE and demonstrates that the new scheme improves both stabilityand accuracy. Model validation is also demonstrated by simulating backward-facingstep flow at low and moderate Reynolds numbers, as well as by comparing the reattachmentlength of the recirculating eddy behind the step against experimental andnumerical data available in literature.

关键词： Lattice Boltzmann equation finite-volumes unstructured grids memory term.

A review on membrane distillation in process engineering: design and exergy equations, materials and wetting problems

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Frontiers of Chemical Science and Engineering 2022年第5期16卷 592-613页

作者： stefano Capizzano Mirko Frappa Francesca Macedonio Enrico Drioli Institute of Membrane Technology National Research Council of ItalyRende 87036Italy Department of Environmental Engineering University of CalabriaRendeItaly Nanjing Tech University College of Chemical EngineeringNanjing 211816China

One of the problems that most afflicts humanity is the lack of clean *** stress,which is the pressure on the quantity and quality of water resources,exists in many places throughout the *** represents a valid solution to the scarcity of fresh water and several technologies are already well applied and successful(such as reverse osmosis),producing about 100 million m^(3)·d^(-1) of fresh *** advances in the field of desalination can be provided by innovative processes such as membrane *** latter is of particular interest for the treatment of waste currents from conventional desalination processes(for example the retentate of reverse osmosis)as it allows to desalt highly concentrated currents as it is not limited by concentration polarization *** perspectives have enhanced research activities and allowed a deeper understanding of mass and heat transport phenomena,membrane wetting,polarization phenomena and have encouraged the use of materials particularly suitable for membrane distillation *** work summarizes recent developments in the field of membrane distillation,studies for module length optimization,commercial membrane modules developed,recent patents and advancement of membrane material.

关键词： membrane distillation recent developments heat and mass transfer wetting membrane material

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Interferometric method to estimate the eigenvalues of a non-Hermitian two-level optical system

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Photonics Research 2022年第4期10卷 1134-1145页

作者： stefano BIASI RICCARDO FRANCHI FILIPPO MIONE LORENZO PAVESI Nanoscience Laboratory Dipartimento di FisicaUniversita di Trento38123 TrentoItaly

Non-Hermitian physics has found a fertile ground in optics. Recently, the study of mode coalescence, i.e., exceptional points, has led to the discovery of intriguing and counterintuitive phenomena. Degeneracies are typically modeled through the coupled mode theory to determine the behavior of eigenstates and eigenvalues. However,the complex nature of the eigenvalues makes their characterization from the response spectrum difficult. Here,we demonstrate that a coherent interferometric excitation allows estimation of both the real and imaginary parts of the eigenvalues. We study the clockwise and counter-clockwise modes in optical microresonators both in the case of Hermitian and non-Hermitian intermodal coupling. We show the conditions by which a resonant doublet,due to the dissipative coupling of counter-propagating modes caused by surface roughness backscattering, merges to a single Lorentzian. This permits us to estimate the optimal quality factor of the microresonator in the absence of modal coupling caused by backscattering. Furthermore, we demonstrate that a taiji microresonator working at an exceptional point shows a degeneracy splitting only in one propagation direction and not in the other. This follows from the strongly non-Hermitian intermodal coupling caused by the inner S-shaped waveguide.

关键词： eigenvalues exceptional intuitive

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Evolving strategies for liver fibrosis staging: Non-invasive assessment

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World Journal of Gastroenterology 2017年第2期23卷 191-196页

作者： cristina Stasi stefano Milani Department of Experimental and Clinical Medicine University of Florence Department of Biomedical Experimental and Clinical SciencesUniversity of Florence

Transient elastography and the acoustic radiation force impulse techniques may play a pivotal role in the study of liver fibrosis. Some studies have shown that elastography can detect both the progression and regression of fibrosis. Similarly, research results have been analysed and direct and indirect serum markers of hepatic fibrosis have shown high diagnostic accuracy for advanced fibrosis/cirrhosis. The prognosis of different stages of cirrhosis is well established and various staging systems have been proposed, largely based on clinical data. However, it is still unknown if either noninvasive markers of liver fibrosis or elastography may contribute to a more accurate staging of liver cirrhosis, in terms of prognosis and fibrosis regression after effective therapy. In fact, not enough studies have shown both the fibrosis regression in different cirrhosis stages and the point beyond which the prognosis does not change- even in the event of fibrosis regression. Therefore, future studies are needed to validate noninvasive methods in predicting the different phases of liver cirrhosis.

关键词： Elastography Non-invasive methods Chronic liver diseases Stiffness Non-invasive serum markers

Domain Decomposition Preconditioners for Discontinuous Galerkin Discretizations of Compressible Fluid Flows

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Numerical Mathematics(Theory,Methods and Applications) 2014年第2期7卷 123-148页

作者： stefano Giani Paul Houston School of Engineering and Computing Sciences Durham UniversitySouth RoadDurhamDH13LEUK. School of Mathematical Sciences University of NottinghamUniversity ParkNottingham NG72RDUK.

In this article we consider the application of Schwarz-type domain decomposition preconditioners to the discontinuous Galerkin finite element approximation of the compressible Navier-Stokes *** discretize this system of conservation laws,we exploit the(adjoint consistent)symmetric version of the interior penalty discontinuous Galerkin finite element *** define the necessary coarse-level solver required for the definition of the proposed preconditioner,we exploit ideas from composite finite element methods,which allow for the definition of finite element schemes on general meshes consisting of polygonal(agglomerated)*** practical performance of the proposed preconditioner is demonstrated for a series of viscous test cases in both two-and three-dimensions.

关键词： Composite finite element methods discontinuous Galerkin methods domain decomposition Schwarz preconditioners compressible fluid flows

3D Identification of Face and Flank in Micro-mills for Automatic Measurement of Rake Angle

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Nanomanufacturing and Metrology 2020年第2期3卷 151-163页

作者： stefano Petro Giovanni Moroni Department of Mechanical Engineering Politecnico di MilanoVia Giuseppe la Masa 120156 MilanItaly

In an Industry 4.0 context,to each object a"digital twin"is associated,which is a virtual counterpart of the object *** the case of a tool,this includes,together with its material and manufacturing information,its solid *** geometry knowledge is fundamental to enable effective tool management,manufacturing verification,and tooling *** for tool management the conventional 2D presetting is sufficient,tooling simulation and tool manufacturing verification require a complete 3D *** is particularly true in the case of the microtools:the process of micro-chip formation is still a research *** the 3D geometry of a tool is well established in the ISO 3002 series of standard,only recently 3D measurement of tools has been made possible by new measuring ***,tool geometry verification requires a lot of human *** paper aims at setting the base for the automatic analysis of point meshes scanned on the whole surface of tools,and in particular *** first step for doing this is the identification of the active surfaces of the tool,that is the face and the flank plus the cutting *** identification of these geometric features is in general possible thanks to their specific characteristics:in particular,the cutting edge is characterized by a high curvature,and it separates the face from the *** paper considers cylindrical micro end-mills as a first example of an approach that can be extended to in principle any kind of *** cylindrical helix characterizing the cutting edge is the key geometry to be considered in the development of the specific *** the tool features(face,flank,and cutting edge)have been separated,of the tool angles,for instance,can be *** first angle to study,the rake angle has been *** approach will be validated on simulated data and on real scans of micro-tools.

关键词： Tool metrology 3D measurement Partitioning Tool angles

Influence of Large woody debris on sediment scour at bridge piers

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International Journal of Sediment Research 2011年第2期26卷 121-133+135+134页

作者： stefano PAGLIARA Iacopo CARNACINA Prof.Dept. of Civil Engineering University of Pisa Ph.D.Dept. of Civil Engineering University of Pisa

Large woody debris(LWD) reduces the flow area,deviate the flow and increases the velocity in correspondence of the bridge pier,therefore increases the maximum scour hole depth and accelerates sediment *** and drifts accumulated on bridge piers are of different *** to logs characteristics and river morphology,drift accumulations can either extend downstream the bridge pier or they can accumulate totally *** paper aims to analyze the effect of drift accumulation planimetry on bridge pier *** experimental investigation has been carried out at the PITLAB hydraulic centre of Civil Engineering Department,University of Pisa,*** accumulation was characterized by different relative longitudinal lengths,flow area occlusions,length of longitudinal drift and downstream planimetrical positions relative to the pier *** experimental investigation has been carried out in clear-water *** pier sizes,channel widths and sediment materials have been *** scour hole in presence of drift accumulation have been compared to the maximum scour hole for an isolated ***,data were compared with previous literature findings,which highlight the effect of the downstream extension of drift accumulation on bridge pier *** relationships have been proposed to predict the effect of drift accumulation on bridge pier scour,both in terms of relative maximum scour and temporal scour evolution.

关键词： Bridge pier Bridge scour Drift shape Planimetry Temporal scour evolution