Analisi di modelli e sviluppo di algoritmi computazionali per lo studio della dinamica di una rete neuro-astrocitaria

Sin dalla loro scoperta si è pensato che le cellule gliali avessero la sola funzione di sostegno e nutrizionale per i neuroni e che l’elaborazione dell’informazione nel cervello fosse un compito adibito ai soli neuroni. Tra le cellule gliali la varietà più numerosa e più studiata è quella degli astrociti, cosiddetti per la loro caratteristica forma a stella. Negli ultimi dieci anni è stato dimostrato che essi costituiscono il terzo elemento attivo della sinapsi chimica, modulando la sua funzione: tali cellule ascoltano ed intervengono nella comunicazione neuronale mediante una codifica tra linguaggio astrocitario (variazioni nella concentrazione di calcio intracellulare) e linguaggio neurale (emissione di neurotrasmettitori). L’obiettivo principale di questo lavoro consiste nell’analisi di modelli per la comprensione del funzionamento delle interazioni tra neuroni ed astrociti, al fine di creare un sistema computazionale di complessità trattabile con cui poter simulare e quindi cercare di capire le dinamiche che potrebbe presentare una rete neuro-astrocitaria

Mass transfer in fluidized bed drying of moist particulate

Bubbling fluidized bed technology is one of the most effective mean for interaction between solid and gas flow, mainly due to its good mixing and high heat and mass transfer rate. It has been widely used at a commercial scale for drying of grains such as in pharmaceutical, fertilizers and food industries. When applied to drying of non-pours moist solid particles, the water is drawn-off driven by the difference in water concentration between the solid phase and the fluidizing gas. In most cases, the fluidizing gas or drying agent is air. Despite of the simplicity of its operation, the design of a bubbling fluidized bed dryer requires an understanding of the combined complexity in hydrodynamics and the mass transfer mechanism. On the other hand, reliable mass transfer coefficient equations are also required to satisfy the growing interest in mathematical modelling and simulation, for accurate prediction of the process kinetics. This chapter presents an overview of the various mechanisms contributing to particulate drying in a bubbling fluidized bed and the mass transfer coefficient corresponding to each mechanism. In addition, a case study on measuring the overall mass transfer coefficient is discussed. These measurements are then used for the validation of mass transfer coefficient correlations and for assessing the various assumptions used in developing these correlations

Learning with side information: PAC learning bounds

AbstractThis paper considers a modification of a PAC learning theory problem in which each instance of the training data is supplemented with side information. In this case, a transformation, given by a side-information map, of the training instance is also classified. However, the learning algorithm needs only to classify a new instance, not the instance and its value under the side information map. Side information can improve general learning rates, but not always. This paper shows that side information leads to the improvement of standard PAC learning theory rate bounds, under restrictions on the probable overlap between concepts and their images under the side information map

Mass transfer coefficient for drying of moist particulate in a bubbling fluidized bed

Experiments on drying of moist particles by ambient air were carried out to measure the mass transfer coefficient in a bubbling fluidized bed. Fine glass beads of mean diameter 125?µm were used as the bed material. Throughout the drying process, the dynamic material distribution was recorded by electrical capacitance tomography (ECT) and the exit air condition was recorded by a temperature/humidity probe. The ECT data were used to obtain qualitative and quantitative information on the bubble characteristics. The exit air moisture content was used to determine the water content in the bed. The measured overall mass transfer coefficient was in the range of 0.0145–0.021?m/s. A simple model based on the available correlations for bubble-cloud and cloud-dense interchange (two-region model) was used to predict the overall mass transfer coefficient. Comparison between the measured and predicted mass transfer coefficient have shown reasonable agreement. The results were also used to determine the relative importance of the two transfer regions

Analysis of process variables via CFD to evaluate the performance of a FCC riser

Feedstock conversion and yield products are studied through a 3D model simulating the main reactor of the fluid catalytic cracking (FCC) process. Computational fluid dynamic (CFD) is used with Eulerian-Eulerian approach to predict the fluid catalytic cracking behavior. The model considers 12 lumps with catalyst deactivation by coke and poisoning by alkaline nitrides and polycyclic aromatic adsorption to estimate the kinetic behavior which, starting from a given feedstock, produces several cracking products. Different feedstock compositions are considered. The model is compared with sampling data at industrial operation conditions. The simulation model is able to represent accurately the products behavior for the different operating conditions considered. All the conditions considered were solved using a solver ANSYS CFX 14.0. The different operation process variables and hydrodynamic effects of the industrial riser of a fluid catalytic cracking (FCC) are evaluated. Predictions from the model are shown and comparison with experimental conversion and yields products are presented; recommendations are drawn to establish the conditions to obtain higher product yields in the industrial process

Continuum modelling of granular particle flow with inelastic inter-particle collisions

The kinetic theory of granular flow is a successful model for gas-solid flows. However, inelastic collisions between particles, among other mechanisms, cause agglomeration of particles, which may be the reason why undue sensitivity of the model to any slight inelasticity in inter-particle collisions has been seen previously. In contrast to a dry (i.e. no interstitial gas) granular system, this tendency to agglomerate in a gas driven two-phase system may be countered by the carrier gas turbulence. In this paper, a heuristic model for particle gas turbulence interaction is introduced within the scope of a generalized kinetic theory model which incorporates the carrier fluid effect on particulate stresses. The numerical results for the flow of granular particles in vertical pipes, which considers slightly inelastic inter-particle collisions, are in reasonably good agreement with published experimental data. Even in this relatively simple model, the results indicate that the interactions between the particle phase and gas turbulence need to be appropriately addressed in any kinetic theory based model for gas solid flows

Personal Protective Equipment (PPE) waste valorisation via pyrolysis: Face masks and nitrile gloves products, characterisation and challenges

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The performance of air and fuel reactors in a chemical looping combustion plant

In chemical looping combustion (CLC) technology, two interconnected fluidised beds are usually employed to carry out the oxidation and the reduction of the metal oxide circulating between them. We present models for the two fluidised beds which take into account both kinetic and hydrodynamic phenomena. We developed hydrodynamic models for each fluidised bed which consider the influence of mass transfer, the variation of solid void fraction and conversion; simulation tests were carried out to study the effects of such factors on the performance of the beds. Optimisation of the main variables affecting the process was carried out to minimise the total solid inventory within the two fluidised beds which is believed to account for the major operational cost of the plant. The plant efficiency was evaluated and an optimal thermal integration investigated; the results are discussed in relation to the conditions needed to increase the thermal efficiency of the process and to reduce the utilities’ cost