Search results for "SEP"
showing 10 items of 2642 documents
Analysis of complex singularities in high-Reynolds-number Navier-Stokes solutions
2013
AbstractNumerical solutions of the laminar Prandtl boundary-layer and Navier–Stokes equations are considered for the case of the two-dimensional uniform flow past an impulsively-started circular cylinder. The various viscous–inviscid interactions that occur during the unsteady separation process are investigated by applying complex singularity analysis to the wall shear and streamwise velocity component of the two solutions. This is carried out using two different methodologies, namely a singularity-tracking method and the Padé approximation. It is shown how the van Dommelen and Shen singularity that occurs in solutions of the Prandtl boundary-layer equations evolves in the complex plane be…
Singularity formation and separation phenomena in boundary layer theory
2009
In this paper we review some results concerning the behaviour of the incompressible Navier–Stokes solutions in the zero viscosity limit. Most of the emphasis is put on the phenomena occurring in the boundary layer created when the no-slip condition is imposed. Numerical simulations are used to explore the limits of the theory. We also consider the case of 2D vortex layers, i.e. flows with internal layers in the form of a rapid variation, across a curve, of the tangential velocity.
Singularities for Prandtl's equations.
2006
We used a mixed spectral/finite-difference numerical method to investigate the possibility of a finite time blow-up of the solutions of Prandtl's equations for the case of the impulsively started cylinder. Our toll is the complex singularity tracking method. We show that a cubic root singularity seems to develop, in a time that can be made arbitrarily short, from a class of data uniformely bounded in H^1.
CANDIDA SEPTIC THROMBOSIS OF THE LEFT ATRIUM IN TWINS: REPORT OF TWO CASES
2009
Background: Preterms are often exposed to nosocomial infections in NICU. Candida infections are particularly common and can result in progressive organization of intracardiac thrombosis, usually in the right atrium. Design and population: GB (24.4 wg, 460 g, bigeminal pregnancy): he was affected by RDS, PDA, jaundice, anaemia and had been submitted to TPN with CVC, also because of anus imperforate. On the 50th day, haemoculture resulted positive for Candida parapsilosis and, by echocardiography, hyperecogen peduncolate formation in the appendix of left auricola. Despite antifungal therapy, exitus occurred. CM (32.4 wg, 1390 g, bigeminal pregnancy): on 2nd day, she was operated for “apple-pe…
Pregnenolone sulphate improves memory processing in early-handled female rats
2013
Early life experiences lead to sex-specific behavioural and neurochemical changes in adulthood. Indeed, early handling enhances learning and memory in male rats (Cannizzaro et al., 2005), whereas it impairs learning performance in female adult rats, a finding that has been correlated to decreased nitric oxide (NO) production in the hippocampus (Noschang et al., 2010). Pregnenolone sulfate (PREGS) is considered as one of the most potent memory-enhancing neurosteroids, since its activity as a potent positive modulator of N-methyl-d-aspartate receptors (NMDARs) and a negative modulator of gamma-aminobutyric acid(A) receptors (GABA(A)Rs) (Vallée et al., 2001). Given these premises, this study a…
Insindacabilità parlamentare e diritti fondamentali: un problema solo italiano?
2011
La Corte europea dei diritti dell'uomo (ECHR) ha condannato l'Italia per violazione dell'art. 6.1. CEDU ben sette volte in relazione alle modalità di applicazione dell'articolo 68 c. 1° Cost. It. La prerogativa parlamentare dell'insindacabilità, secondo la Corte di Strasburgo, avrebbe determinato una violazione del diritto d'accesso ad un giudice. Seppure la disicplina costituzionale della prerogativa è stata ritenuta necessaria alla tutela di un interesse fondamentale dello Stato (il principio di separazione dei poteri), nelle modalità applicative è risultata essere una "misura" non rispettosa del principio di proporzionalità rispetto al fine perseguito. L'analisi condotta mira a verificar…
CFD prediction of concentration polarization phenomena in spacer-filled channels for Reverse Electrodialysis
2014
Abstract Salinity Gradient Power generation through Reverse Electrodialysis (SGP-RE) is a promising technology to convert the chemical potential difference of a salinity gradient into electric energy. In SGP-RE systems, as in most membrane processes, concentration polarization phenomena may affect the theoretical driving force and thus the performance of the process. Operating conditions, including the feed solution flow rate and concentration and the channels׳ geometrical configuration, may greatly influence both the polarization effect and the pumping energy consumption. The present work uses CFD to investigate the dependence of concentration polarization and pressure drop on flow rate, f…
Method fragments for agent design methodologies: from standardisation to research
2007
The method engineering paradigm enables designers to reuse portions of design processes (called method fragments or chunks in literature) to build processes that are expressly tailored for realising a system that is specific for some problem or development context. This paper initially reports on the standardisation attempt carried out by the FIPA Methodology Technical Committee (TC) and then presents the research activities we did starting from that work; these resulted in a slightly different definition of some of the most important elements of the approach in order to support a multiview representation of the fragment (the views are process, reuse, storing and implementation). The paper …
A Study of the Separation of 1-Dodecene and 1-Tetradecene Hydroformylation Products in Aqueous Medium
2009
Abstract Experimental results of the solubilization of olefins in hydroformylation model systems, comprising 1-dodecene and 1-tridecanal or 1-tetradecene and 1-pentadecanal, water, butanol, sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and/or tri(m-sulfofenyl)phosphine trisodium salt (TPPTS-Na) are presented. The selected systems were used for the hydroformylation of 1-dodecene and 1-tetradecene whereby high yields of aldehydes were obtained. After the reaction, the mixture spontaneously separated into an organic phase with the reaction products and an aqueous phase comprising the catalyst and excess phosphine ligand.
Sulfonation of Triphenylphosphines and Separation of Sulfonated Triphenylphosphines by Crystallization and Solvent Extraction
2007
Abstract The effect of sulfonation conditions on the formation of sulfonated triphenylphosphines and their separation from the post‐reaction mixture, containing concentrated sulphuric acid, was studied. The solvent extraction was found to be a suitable technique to separate sulfonated triphenylphosphines from concentrated sulphuric acid, and the purity and yield was higher than obtained by crystallization from various solvents. Tributyl phosphate was a suitable extractant. Sodium salts of sulfonated triphenylphosphines could then be recovered as precipitates by treating the organic phase with the sodium hydroxide solution and separation by crystallization. The solvent extraction simplified …