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Large Eddy Simulation of the By-pass Transition Process under Different Inlet Turbulence Conditions

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Journal of Thermal Science 2021年第6期30卷 2112-2121页

作者： BARSI Dario COSTA Carlo LENGANI Davide SIMONI Daniele UBALDI Marina DIME-University of Genova Via Montallegro 11-16145 GenovaItaly

The transition process of the boundary layer developing over a flat plate with elevated inlet Free Stream Turbulence Intensity(FSTI)has been studied by means of Large Eddy Simulation(LES).To this purpose,four cases with different inflow disturbances have been tested varying the magnitude and the length scale of *** has been performed by using the finite-volume ANSYS Fluent *** computational domain,which was constituted by a rectangular domain with a zero thickness plate,was based on an ERCOFTAC test case in order to provide a validation with a well-known set of data by comparing the boundary layer integral parameters and mean and fluctuating streamwise velocity *** four cases were discussed within the paper by looking at classical statistical properties as well as advanced post-processing *** was shown that the decrease in the free stream turbulence level postpones the transition location,whereas the variation of the integral length scale has a very low influence on the distribution of the time-mean flow *** Orthogonal Decomposition(POD)has been applied to the instantaneous LES flow fields in order to provide a statistical representation of the structures responsible for transition and their response to free-stream turbulence intensity and length *** presence of vortical filaments parallel to the wall,typically referred as boundary layer streaks,is clearly identified;their characteristic dimensions and how they change as a function of FSTI properties were analyzed within the paper.

关键词： by-pass transition Large Eddy Simulation(LES) Proper Orthogonal Decomposition(POD) boundary layer streaks

Design of Off-statistics Axial-flow Fans by Means of Vortex Law Optimization

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Journal of Thermal Science 2014年第6期23卷 505-515页

作者： Andrea Lazari Andrea Cattanei DIME-Università degli Studi di Genova Via Montallegro 1I-16145 GenovaItaly Presently with FPZ S.p.A. Via Fratelli Cervi16I-20863ConcorezzoItaly

Off-statistics input data sets are common in axial-flow fans design and may easily result in some violation of the requirements of a good aerodynamic blade *** order to circumvent this problem,in the present paper,a solution to the radial equilibrium equation is found which minimizes the outlet kinetic energy and fulfills the aerodynamic constraints,thus ensuring that the resulting blade has acceptable aerodynamic *** presented method is based on the optimization of a three-parameters vortex law and of the meridional channel *** aerodynamic quantities to be employed as constraints are individuated and their suitable ranges of variation are *** method is validated by means of a design with critical input data values and CFD ***,by means of systematic computations with different input data sets,some correlations and charts are obtained which are analogous to classic correlations based on statistical investigations on existing *** new correlations help size a fan of given characteristics as well as study the feasibility of a given design.

关键词： axial flow fan statistical correlations optimum design feasibility study

Modeling the effect of sediment concentration on the flow-like behavior of natural debris flow

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International Journal of Sediment Research 2020年第4期35卷 315-327页

作者： Leonardo Schippa Department of Engineering University of Ferrara 1 Via Saragat

The rheological behavior of natural slurries consisting of fine-grained,reconstituted debris-flow deposits on pyroclastic terrains having different solid concentrations(ranging from 30 to 42%) has been investigated using a rotational rheometer equipped with a vane rotor *** were done by increasing the applied shear stress step by step;then a decreasing stress ramp was applied following the same shear stress *** slurry mixtures exhibit a typical yield-stress fluid behavior with a static yield stress larger than the dynamic yield *** the range of the shear rate corresponding to the flowlike behavior the slurry mixtures behave as a dilatant fluid at lower grain concentrations and as a pseudoplastic fluid in correspondence with the higher grain content,showing a strong discrepancy from the Bingham *** rheological behavior is better interpreted by a Herschel-Bulkley model,whose rheological parameters strongly depend on the granular ***,a generalized Herschel-Bulkley model accounting for the bulk sediment concentration effect is *** rheological behavior of natural slurries consisting of fine-grained, reconstituted debris-flow deposits on pyroclastic terrains having different solid concentrations(ranging from 30 to 42%) has been inves?tigated using a rotational rheometer equipped with a vane rotor system. Experiments were done by increasing the applied shear stress step by step; then a decreasing stress ramp was applied following the same shear stress levels. The slurry mixtures exhibit a typical yield-stress fluid behavior with a static yield stress larger than the dynamic yield stress. In the range of the shear rate corresponding to the flow?like behavior the slurry mixtures behave as a dilatant fluid at lower grain concentrations and as a pseudoplastic fluid in correspondence with the higher grain content, showing a strong discrepancy from the Bingham idealization. The rheological behavior is better i

关键词： Debris flow Rheology Grain concentration Herschel-Bulkley model

Metal-Halide Perovskite Submicrometer-Thick Films for Ultra-Stable Self-Powered Direct X-Ray Detectors

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Nano-Micro Letters 2024年第9期16卷 410-431页

作者： Marco Girolami Fabio Matteocci Sara Pettinato Valerio Serpente Eleonora Bolli Barbara Paci Amanda Generosi Stefano Salvatori Aldo Di Carlo Daniele M.Trucchi CNR‑ISM Consiglio Nazionale delle RicercheIstituto di Struttura della MateriaSede Secondaria di MontelibrettiDiaTHEMA LabStrada Provinciale 35D900010 MontelibrettiRomeItaly CHOSE–Centre for Hybrid and Organic Solar Energy Department of Electronic EngineeringUniversity of Rome“Tor Vergata”Via del Politecnico 100133 RomeItaly Faculty of Engineering Universita degli Studi Niccolo CusanoVia don Carlo Gnocchi 300166 RomeItaly SpecXLab CNR‑ISMConsiglio Nazionale Delle RicercheIstituto di Struttura Della MateriaArea della Ricerca di Tor VergataVia del Fosso del Cavaliere 10000133 RomeItaly

Metal-halide perovskites are revolutionizing the world of X-ray detectors,due to the development of sensitive,fast,and cost-effective ***-powered operation,ensuring portability and low power consumption,has also been recently demonstrated in both bulk materials and thin ***,the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours,often reporting degradation of the detection *** it is shown that self-powered direct X-ray detectors,fabricated starting from a FAPbBr_(3)submicrometer-thick film deposition onto a mesoporous TiO_(2)scaffold,can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss,demonstrating ultra-high operational stability and excellent *** structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy,revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin *** addition,trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy^(−1)cm^(−3)at 0 V,an unprecedented value in the field of thin-film-based photoconductors and photodiodes for“hard”***,prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced.

关键词： Metal-halide perovskite thin films Direct X-ray detectors Self-powered devices Operational stability Medical linear accelerator

Management of cholelithiasis in Italian children:A national multicenter study

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World Journal of Gastroenterology 2008年第9期14卷 1383-1388页

作者： Claudia Della Corte Diego Falchetti Gabriella Nebbia Marisa Calacoci Maria Pastore Ruggiero Francavilla Matilde Marcellini Pietro Vajro Raffaele Iorio Department of Paediatrics University of Naples "Federico Ⅱ"Via S. Pansini 5Naples 80131 Italy Department of Pediatric Surgery "Spedali Civili"Piazza Spedali Civili 1Brescia 25100Italy Department of Pediatrics Ⅱ Fondazione IRCCS Ospedale Maggiore di MilanoVia F.Sforza 35Milan 20122Italy Department of Pediatrics University of FerraraVia Savonarola 944100 FerraraItaly Department of Pediatrics IRCCS "Casa Sollievo della Sofferenza" Viale Cappuccini 1 San Giovanni Rotondo 71013Italy Department of Pediatrics University of Bari Piazza Giulio Cesare 11 Bari 70124 Italy Department of Pediatrics Ospedale "Bambin Gesù"Piazza S. Onofrio 4 Rome 00165Italy Department of Paediatrics University of Naples "Federico Ⅱ" Via S. Pansini 5 Naples 80131Italy Department of Paediatrics University of Naples"Federico Ⅱ" Via S.Pansini 5Naples 80131Italy

AIM:To evaluate the management of Italian children with cholelithiasis observed at Pediatric and Surgical Departments linked to Italian Society of Pediatric Gastroenterology Hepatology and Nutrition. METHODS: One-hundred-eighty children (90 males, median age at diagnosis 7.3 years; range, 0-18 years) with echographic evidence of cholelithiasis were enrolled in the study; the data were collected by an anonymous questionnaire sent to participating centers. RESULTS: One hundred seventeen patients were treated with ursodeoxycholic acid; in 8 children dissolution of gallstones was observed, but the cholelithiasis recurred in 3 of them. Sixty-five percent of symptomatic children treated became asymptomatic. Sixty-four patients were treated with cholecystectomy and in only 2 cases a postoperative complication was reported. Thirty- four children received no treatment and were followed with clinical and echographic controls; in no case thedevelopment of complications was reported. CONCLUSION: The therapeutic strategies were extremely heterogeneous. Ursodeoxycholic acid was ineffective in dissolution of gallstones but it had a positive effect on the symptoms. Laparoscopic cholecystectomy was confirmed to be an efficacy and safe treatment for pediatric gallstones.

关键词： Pediatric cholelithiasis Ursodeoxycholic acid Laparoscopic cholecystectomy Gallstones Children

Surface and transport properties of Cu-Sn-Ti liquid alloys

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Rare Metals 2006年第5期25卷 457-468页

作者： R.Novakovic E.Ricci1 S.Amore T.Lanata National Research Council (CNR)–Institute for Energetics and Interphases (IENI) Via De Marini6-16149-GenoaItaly National Research Council (CNR)–Institute for Energetics and Interphases (IENI) Via De Marini6-16149-GenoaItalyDCCI-University of Genoa & Genoa Research Unit of National Consortium of Materials Science & Technology (INSTM)Via Dodecaneso31 - 16146-GenoaItaly National Research Council (CNR)–Institute for Energetics and Interphases (IENI) Via De Marini6-16149-GenoaItalyDIAM-University of GenoaVia Opera Pia15 - 16145-GenoaItaly

The lack of experimental data and / or limited experimental information concerning both surface and transport properties of liquid alloys often require the prediction of these quantities. An attempt has been made to link the thermophysical properties of a ternary Cu-Sn-Ti system and its binary Cu-Sn, Cu-Ti and SnoTi subsystems with the bulk through the study of the concentration dependence of various thermodynamic, structural, surface and dynamic properties in the frame of the statistical mechanical theory in conjunction with the quasi-lattice theory （QLT）. This formalism provides valuable qualitative insight into mixing processes that occur in molten alloys.

关键词： equilibrium thermodynamics and statistical mechanics surface segregation surface tension surface thermodynamics (including phase transitions) liquid surfaces copper tin titanium alloys

Analysis of Tonal Noise Generating Mechanisms in Low-Speed Axial-Flow Fans

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Journal of Thermal Science 2016年第4期25卷 302-311页

作者： Edward Canepa Andrea Cattanei Fabio Mazzocut Zecchin DIME-Universita di Genova via Montallegro 1 1-16145 Genoa Italy

The present paper reports a comparison of experimental SPL spectral data related to the tonal noise generated by axial-flow fans.A nine blade rotor has been operated at free discharge conditions and in four geometrical configurations in which different kinds of tonal noise generating mechanisms are present:large-scale inlet turbulent structures,tip-gap flow,turbulent wakes,and rotor-stator *** measurements have been taken in a hemi-anechoic chamber at constant rotational speed and,in order to vary the acoustic source strength,during low angular acceleration,linear speed *** order to avoid erroneous quantitative evaluations if the acoustic propagation effects are not considered,the acoustic response functions of the different test configurations have been computed by means of the spectral decomposition ***,the properties of the tonal noise generating mechanisms have been *** this aim,the constant-Strouhal number SPL,obtained by means of measurements taken during the speed ramps,have been compared with the propagation ***,the analysis of the phase of the acoustic pressure has allowed to distinguish between random and deterministic tonal noise generating mechanisms and to collect information about the presence of important propagation effects.

关键词： Axial-flow fans Tonal noise Acoustic response

CFD Study of Ejector Flow Behavior in a Blast Furnace Gas Galvanizing Plant

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Journal of Thermal Science 2015年第1期24卷 58-66页

作者： Giorgio Besagni Riccardo Mereu Fabio Inzoli Politecnico di Milano Department of EnergyVia Lambruschini 4 Milan 20156 Italy

In recent years, there has been a growing interest toward Blast Furnace Gas （BFG） as a low-grade energy source for industrial furnaces. This paper considers the revamping of a galvanic plant furnace converted to BFG from natural gas. In the design of the new system, the ejector on the exhaust line is a critical component. This paper studies the flow behavior of the ejector using a Computational Fluid Dynamics （CFD） analysis. The CFD model is based on a 3D representation of the ejector, using air and exhaust gases as working fluids. This paper is divided in three parts. In the first part, the galvanic plant used as case study is presented and discussed, in the second part the CFD approach is outlined, and in the third part the CFD approach is validated using experimental data and the numerical results are presented and discussed. Different Reynolds-Averaged Navier-Stokes （RANS） turbulence models （k-to SST and k-e Realizable） are evaluated in terms of convergence capability and accuracy in predicting the pressure drop along the ejector. Suggestions for future optimization of the system are also provided.

关键词： CFD Ejector Blast Furnace Gas Galvanic plant RANS Turbulence models

Setting a highway for converting skin into neurons

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Journal of Molecular Cell Biology 2011年第6期3卷 322-323页

作者： Vania Broccoli Massimiliano Caiazzo Maria Teresa Dell’Anno San Raffaele Scientific Institute Via Olgettina 58Milan 20132Italy

Direct conversion of human skin fibroblasts into induced neuronal(iN)cells has been recently achieved by using different combi-nations of transcription factors eventually associated with *** findings lay the ground for a straightforward and effi-cient generation of human neurons in vitro with elaborated functional properties instrumental for disease modeling and cell-based approaches of brain repair.

关键词： eventually straight finding