Search results for "Large"
showing 10 items of 2197 documents
Time-resolved velocity measurements in a magnetic micromixer
2015
Abstract Mixing efficiency is lower in passive micromixers due to viscous forces and substantial research effort is focused on designing high performance micromixers. Active micromixers make use of external forces to enhance mixing efficiency. Among these, magnetic forces are popular because they are non-contact and therefore the micromixer design can be kept simple. Laser-based diagnostic tools have great potential in providing multi-parameter information in microfluidics research on mixing. MicroPIV experiments are performed to investigate the transient flow field in a magnetic micromixer undergoing labyrinthine instability. Velocity and interface front information is extracted from a seq…
Numerical observations of turbulence structure modification in channel flow over 2D and 3D rough walls
2015
Abstract The effects of wall roughness on turbulence structure modifications were explored by numerical experiments, carried out using Large Eddy Simulation techniques. The wall geometry was made using an archetypal artificial method, thus to achieve irregular two- and three-dimensional shapes. The proposed roughness shapes are highly irregular and are characterised by high and small peaks, thus it can be considered a practical realistic roughness. Their effects are analysed comparing the turbulence quantities over smooth, 2D and 3D rough walls of fully developed channel flow at relatively low friction Reynolds number Re τ = 395 . Both transitional and fully rough regimes have been investig…
Experimental and Numerical Study on the Flow Field and Friction Factor in a Pressurized Corrugated Pipe
2015
An experimental campaign including measurement of pressure drops and velocity profiles was conducted on the pressurized flow in a commercial corrugated pipe. The results show that the empirical graphs suggested by Morris in the fifties may produce inaccurate assessments of the friction factor, in particular, for low Reynolds numbers. The experimental data was then reproduced by means of a numerical model with the large eddy simulation (LES) technique. The friction factor behavior for low and relatively high Reynolds numbers was thus investigated. The numerical simulations were in good agreement with the experimental results, showing the LES suitability to predict the effect of the pipe wall…
Large Eddy Simulations of Rough Turbulent Channel Flows Bounded by Irregular Roughness: Advances Toward a Universal Roughness Correlation
2020
The downward shift of the mean velocity profile in the logarithmic region, known as roughness function, $$\Delta U^+$$ , is the major macroscopic effect of roughness in wall bounded flows. This speed decrease, which is strictly linked to the friction Reynolds number and the geometrical properties which define the roughness pattern such as roughness height, density, shape parameters, has been deeply investigated in the past decades. Among the geometrical parameters, the effective slope (ES) seems to be suitable to estimate the roughness function at fixed friction Reynolds number, Re $$_{\tau }$$ . In the present work, the effects of several geometrical parameters on the roughness function, i…
Scientific and technological approaches for sintering and joining of metallic materials by SPS
2013
The flash sintering technique (commonly known as spark plasma sintering, SPS) generates a craze worldwide. This process allows a powder densification from speeds generally 10 to 100 times higher than those of the traditional sintering techniques. In addition, this allows the synthesis of innovative and original dense materials, with a controlled microstructure, complex shapes and, sometimes large sizes. However, the control of scaling and microstructure homogeneity of parts obtained by such a process requires a perfect knowledge of technical equipment including flash sintering to reduce thermal gradients. Modeling is a valuable aid to achieve the improvement of its control. Another potentia…
Electrodeposition of CeO2 and Co-Doped CeO2 Nanotubes by Cyclic Anodization in Porous Alumina Membranes
2013
An anodic electrodeposition process is proposed to prepare CeO2 and Co-doped CeO2 nanotubes. Anodic alumina membrane is used as template and linear sweep voltammetry is employed to allow the formation of nanotubes without alumina dissolution. SEM micrographs showed large arrays of well defined and aligned NTs, which resulted to be crystalline soon after deposition according to XRD diffraction patterns and Raman Spectroscopy.
Study of the potential toxicity of enniatins A, A(1), B, B(1) by evaluation of duodenal and colonic bioavailability applying an in vitro method by Ca…
2010
Abstract The bioavailability of the minor Fusarium mycotoxins enniatins (ENs) utilizing an in vitro method which allows the simulation of the small and large intestine tracts has been studied. This method, based on the application of the Caco-2 cells grown alone or in symbiosis with several strains characteristics of the gastrointestinal tract, has permitted to simulate the duodenal and colonic intestinal compartments, respectively. The duodenal bioavailability expressed as absorption value after 4 h of exposure, ranged from 57.7 to 76.8% for EN A, from 68.8 to 70.2% for EN A1, from 65.0 to 67.0% for EN B, and from 62.2 to 65.1% for EN B1. Colonic bioavailability after 48 h of incubation ra…
FUTURE IS BACK
2017
«Trent'anni fa, un piano per il futuro di New York sarebbe apparso futile» Michael R. Bloomberg, sindaco di New York, che ha introdotto nel 2007 la relazione sul futuro della città per il 2030, PlaNYC, oppose la città degli anni 1970, «interamente concentrata sulla risoluzione di crisi immediate», alla città di quegli anni, «più forte che mai»: consapevole di aver ritrovato il desiderio del futuro. La data dell'11 settembre non è percepita come un presagio della fine della supremazia americana, è un evento superato - Future is back ! Questo ritorno nel futuro è immaginato da tutte le metropoli preoccupate di inserirsi nel mercato dell'attrattività3. Trent'anni dopo la fine del progresso, l'…
Hadronic calibration of the ATLAS liquid argon end-cap calorimeter in the pseudorapidity region in beam tests
2004
Abstract A full azimuthal φ -wedge of the ATLAS liquid argon end-cap calorimeter has been exposed to beams of electrons, muons and pions in the energy range 6 GeV ⩽ E ⩽ 200 GeV at the CERN SPS. The angular region studied corresponds to the ATLAS impact position around the pseudorapidity interval 1.6 | η | 1.8 . The beam test setup is described. A detailed study of the performance is given as well as the related intercalibration constants obtained. Following the ATLAS hadronic calibration proposal, a first study of the hadron calibration using a weighting ansatz is presented. The results are compared to predictions from Monte Carlo simulations, based on GEANT 3 and GEANT 4 models.
Search for neutralino pair production at root s = 189 GeV
2001
A search for pair-production of neutralinos at a LEP centre-of-mass energy of 189 GeV gave no evidence for a signal. This limits the neutralino production cross-section and excludes regions in the parameter space of the Minimal Supersymmetric Standard Model (MSSM).