Search results for "Solid"
showing 10 items of 3575 documents
CFD prediction of solid particle distribution in baffled stirred vessels under partial to complete suspension conditions
2013
Solid-liquid mixing within tanks agitated by stirrers can be easily encountered in many industrial processes. It is common to find an industrial tank operating at an impeller speed N lower than the minimum agitation speed for the suspension of solid particles: under such conditions the distribution of solid-particles is very far from being homogeneous and very significant concentration gradients exist. The present work evaluates the capability of a Computational Fluid Dynamics (CFD) model to reliably predict the particle distribution throughout the tank under either partial or complete suspension conditions. A flat bottomed baffled tank stirred by a Rushton turbine was investigated. Both tr…
Comparison of Agitators Performance for Particle Suspension in Top-Covered Unbaffled Vessels
2015
Power savings is a problem of crucial importance nowadays. In process industry, suspension of solid particles into liquids is usually obtained by employing stirred tanks, which often are very power demanding. Notwithstanding tanks provided with baffles are traditionally adopted for this task, recent studies have shown that power reductions can be obtained in top-covered unbaffled vessels. In the present work experiments were carried out in a top-covered unbaffled vessel with a diameter T=0.19m and filled with distilled water and silica particles. Two different turbines were tested: a standard six-bladed Rushton Turbine (RT) and a 45° four bladed Pitched Blade Turbine (PBT). For the case of …
Optimization of the performance of an air–cathode MFC by changing solid retention time
2017
BACKGROUND This work is focused on the optimization of the performances of air-cathode microbial fuel cells (MFC) by changing the solid retention time (SRT) of the suspended biomass culture. RESULTS Five MFCs inoculated with activated sludge obtained from a municipal wastewater treatment plant were fed with a highly-concentrated acetate solution (10 000 ppm COD) and operated over two-month tests in order to determine how SRT may influence the performances of the bio-electrogenic cells. The MFC operated at SRTs of 2.5 days was found to outperform the other cells, operated at SRT of 1.4, 5.0, 7.4 and 10.0 days. In order to evaluate the possibility of using SRT as a manipulated parameter for t…
CFD Predictions of Sufficient Suspension Conditions in Solid-Liquid Agitated Tanks
2012
Abstract Most research efforts on mechanically agitated solid-liquid contactors have been devoted to the assessment of the minimum impeller speed for complete off-bottom suspension, N js . Actually, many industrial vessels are operated at impeller speeds slightly lower than N js (Oldshue, 1983; Rieger et al., 1988). This suggests that the sufficient suspension condition, which is quantitatively specified in this paper by introducing a suitably defined quantity N ss , may represent a valid alternative to that of complete suspension. In the present work time-dependent RANS simulations were carried out with the aim of predicting the achievement of sufficient suspension conditions. The Eulerian…
An FPGA Implementation of a Quadruple-Based Multiplier for 4D Clifford Algebra
2008
Geometric or Clifford algebra is an interesting paradigm for geometric modeling in fields as computer graphics, machine vision and robotics. In these areas the research effort is actually aimed at finding an efficient implementation of geometric algebra. The best way to exploit the symbolic computing power of geometric algebra is to support its data types and operators directly in hardware. However the natural representation of the algebra elements as variable-length objects causes some problems in the case of a hardware implementation. This paper proposes a 4D Clifford algebra in which the variable-length elements are mapped into fixed-length elements (quadruples). This choice leads to a s…
Distacco del lavoratore, interesse solidaristico tra imprese e crisi economica
2021
Una delle questioni più dibattute a seguito dell'introduzione della disciplina del distacco, con il d.lgs. n. 276/2003, ha riguardato la natura dell'interesse del distaccante, soprattutto con riferimento a forme di interesse di natura non economica o di carattere non patrimoniale. Il saggio affronta l'ammissibilità di un interesse solidaristico tra imprese, e, attraverso un'analisi dei più recenti orientamenti giurisprudenziali, ne specifica i requisiti di legittimità: da rinvenirsi nella temporaneità, per l'intera durata del distacco, e nella possibilità di individuarlo nell'accrescimento della polivalenza della professionalità del distaccato, sebbene durante una transitoria situazione di …
Anticipo de jubilación en Italia: entre sustenibilidad financiera y solidaridad intergeneracional
2019
The essay focuses on the recent reform of the Italian pensions system ("quota cento") and it puts in evidence the criticalities of the reform having regard to its financial sustainability and to the principle of intergenerational solidarity. El ensayo analiza la reciente reforma al sistema de pensiones italiano ("quota cento") subrayando sus criticidades desde la doble vertiente de la sustenibilidad financiera y de la solidaridad intergeneracional.
Tutela dei crediti di lavoro e responsabilità solidale nel “contratto di logistica integrata”
2023
Il saggio esamina la nuova disciplina dell'art. 1677 bis c.c. in chiave giuslavoristica, soffermandosi sul problema del regime di responsabilità solidale applicabile ai lavoratori impiegati nell'ambito del cd. contratto di logistica integrata
Trasferimento d’azienda e debiti contributivi: la responsabilità solidale dell’acquirente
2001
Il contributo affronta la questione della responsabilità solidale tra cedente e cessionario in caso di trasferimento d'azienda, con riferimento ai debiti contributivi
UN «SALTO DI SPECIE» PER L’UE? LA SOLIDARIETA’ EUROPEA ALLA PROVA DELLA CRISI PANDEMICA
2020
La crisi da covid-19 ha riportato al centro del dibattito gli interrogativi sull’effettiva portata della solidarietà europea, quale parte integrante del modello sociale dell’Unione. L’emergenza sanitaria ha mostrato i limiti del processo di integrazione sovranazionale, caratterizzato da un perdurante deficit di legittimazione democratica dell’Unione e dall’assenza di strumenti di condivisione dei rischi tra gli Stati membri. Il paper ripercorre le iniziative prese dalle Istituzioni europee per fronteggiare la crisi pandemica, mettendo in evidenza il cambio di passo dell’Unione rispetto alla precedente crisi finanziaria, e soffermandosi sulle prospettive di approfondimento della sua dimensio…