CFD analysis of devices i oscillating water column - OWC

The paper is about the development of a fluid-dynamic model for simulating the behaviour of a device for the production of electric energy based on an oscillating water column (OWC). First of all it has been developed a 3-D model of the device using a tool in order to create the grid used for the simulation. The code used for the fluid dynamic simulation is OpenFoam, in particular the solver InterFoam suitable for two-phase isothermal flow characterized by immiscible and incompressible fluids, it uses the VOF (Volume of Fluids) model. The aim of this work is the optimization of the model from the computational point of view, in particular it has been conducted a sensitivity analysis on the processor’s number and on the time step of calculation. In the first phase of the work were taken into account two forcing, approximated with a sinusoidal profile, corresponding to two types of waves more realistic for the site in which it was made the experimental apparatus. Subsequently it has been developed an analysis of the boundary condition in order to simulate in the best way the incident wave. Obviously it is possible to investigate more in detail the model realized in order to optimize the simulation and validate the model with more experimental data

An ant-colony based approach for real-time implicit collaborative information seeking

This document is an Accepted Manuscript of the following article: Alessio Malizia, Kai A. Olsen, Tommaso Turchi, and Pierluigi Crescenzi, ‘An ant-colony based approach for real-time implicit collaborative information seeking’, Information Processing & Management, Vol. 53 (3): 608-623, May 2017. Under embargo until 31 July 2018. The final, definitive version of this paper is available online at doi: https://doi.org/10.1016/j.ipm.2016.12.005, published by Elsevier Ltd.We propose an approach based on Swarm Intelligence — more specifically on Ant Colony Optimization (ACO) — to improve search engines’ performance and reduce information overload by exploiting collective users’ behavior. We designed and developed three different algorithms that employ an ACO-inspired strategy to provide implicit collaborative-seeking features in real time to search engines. The three different algorithms — NaïveRank, RandomRank, and SessionRank — leverage on different principles of ACO in order to exploit users’ interactions and provide them with more relevant results. We designed an evaluation experiment employing two widely used standard datasets of query-click logs issued to two major Web search engines. The results demonstrated how each algorithm is suitable to be employed in ranking results of different types of queries depending on users’ intent.Peer reviewedFinal Accepted Versio

Heat Exchange Analysis on Latent Heat Thermal Energy Storage Systems Using Molten Salts and Nanoparticles as Phase Change Materials

The increase of carbon dioxide emissions is the most important contributor to climate change. A better use of produced energy, increasing systems efficiency and using renewable sources, can limit them. A key technological issue is to integrate a thermal energy storage (TES). It consists in stocking thermal energy through the heating/cooling of a storage material for future needs. Among various technologies, latent heat TES (LHTES) provides high energy storage density at constant temperature during melting/solidification of storage media. The bottleneck in the use of typical PCMs is their low thermal conductivity. To improve the heat exchange between heat transfer fluid and PCM, three methods are possible and here experimentally analyzed: conductivity systems enhancements; convective flows promotion in liquid phase; and improvement of PCM thermal properties including small amounts of nanoparticles. CFD models were used to evaluate physical phenomena that are crucial for optimized LHTES systems design. The study of the heat exchange mode allowed some useful indications to achieve an optimized LHTES, taking advantage by convective flows and conductivity promotion systems. The use of NEPCM, to maximize the stored energy density and realize compact systems, makes necessary the improvement of its thermal diffusivity. These will be the future research topics

Preface of the 31st Italian Symposium on Advanced Database Systems

This volume contains the proceedings of the 31st Italian Symposium on Advanced Database Systems (SEBD - Sistemi Evoluti per Basi di Dati), held in Galzinagno Terme (Padua, Italy) from 2 to 5 July 2023.</p

Preface of the 31st Italian Symposium on Advanced Database Systems

This volume contains the proceedings of the 31st Italian Symposium on Advanced Database Systems (SEBD - Sistemi Evoluti per Basi di Dati), held in Galzinagno Terme (Padua, Italy) from 2 to 5 July 2023.</p

Oxidation mechanism of diethyl ether : a complex process for a simple molecule

International audienceA large number of organic compounds, such as ethers, spontaneously form unstable peroxides through a self-propagating process of autoxidation (peroxidation). Although the hazards of organic peroxides are well known, the oxidation mechanisms of peroxidizable compounds like ethers reported in the literature are vague and often based on old experiments, carried out in very different conditions (e. g. atmospheric, combustion). With the aim to (partially) fill the lack of information, in this paper we present an extensive Density Functional Theory (DFT) study of autoxidation reaction of diethyl ether (DEE), a chemical that is largely used as solvent in laboratories, and which is considered to be responsible for various accidents. The aim of the work is to investigate the most probable reaction paths involved in the autoxidation process and to identify all potential hazardous intermediates, such as peroxides. Beyond the determination of a complex oxidation mechanism for such a simple molecule, our results suggest that the two main reaction channels open in solution are the direct decomposition (beta-scission) of DEE radical issued of the initiation step and the isomerization of the peroxy radical formed upon oxygen attack (DEEOO(center dot)). A simple kinetic evaluation of these two competing reaction channels hints that radical isomerization may play an unexpectedly important role in the global DEE oxidation process. Finally industrial hazards could be related to the hydroperoxide formation and accumulation during the chain propagation step. The resulting information may contribute to the understanding of the accidental risks associated with the use of diethyl ether