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Limongelli C.,University Roma | Sciarrone F.,Open Informatica srl | Sciarrone F.,University of Rome La Sapienza | Temperini M.,Open Informatica srl
Communications in Computer and Information Science | Year: 2013

Nowadays, thanks to the Internet, the request for distance learning is increasing. Private companies and public institutions are very sensitive to the saving of costs that such type of education could implicate, i.e., with no limits in time and place. Besides, the results obtained by this kind of learning are comparable to those reached by the classic in-presence lessons. Consequently, instructional designers need didactic instruments to build courses in a rapid way, especially if they would build their courses starting from learning objects already posted into Learning Object Repositories by other peers. Our work proposes a system, at a very early stage of development, with the aim to help instructional designers to find and retrieve learning objects suitable for their courses, starting from the classic conceptual map of the course to be built. The system contains an OLAP module to let teachers to drill-down into concepts as well. © Springer-Verlag Berlin Heidelberg 2013.

Siontas S.,National Technical University of Athens | Kyritsakis A.,National Technical University of Athens | Xanthakis J.P.,National Technical University of Athens | Iacobucci S.,CNR Institute for Photonics and Nanotechnologies | Stefani G.,University Roma
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2014

The authors have calculated the lateral distribution of field emitted electrons from a carbon nanofiber (CNF) array - a quantity of importance in designing field emission displays - by calculating the electron distribution from an individual CNF and subsequently summing the contribution from all individual CNFs. The authors have not obtained the absolute value of the current but only its relative distribution in space. The full width at half maximum of the lateral distribution has been examined with respect to the following parameters: 1) the CNF tip radius, 2) the anode to cathode distance, and 3) the cathode to anode potential difference. Reasonable agreement with experimental results is obtained. © 2014 American Vacuum Society.

La Rocca M.,University Roma | Mele P.,University Roma | Sciortino G.,University Roma | Boniforti M.A.,University of Rome La Sapienza
Environmental Hydraulics: Theoretical, Experimental and Computational Solutions - Proceedings of the International Workshop on Environmental Hydraulics, IWEH 2009 | Year: 2010

In this paper a mathematical model for 3D turbidity currents has been presented. The model consists in a system of partial differential equations in conservative form, formulated in the framework of the shallow water equations and it accounts for the main features of the turbidity currents: entrainment of environment fluid, settling and resuspension of particles, variation of density. A numerical investigation has been performed to assess the influence of the settling of particles on the turbidity current. To this aim different turbidity currents have been simulated, with the same excess density and initial volume, but realized with silicon carbide particles with increasing diameter. Numerical results are compared with experimental results by La Rocca et al.[8]. The agreement is fairly good and shows the ability of the proposed model in reproducing the main features of the physical phenomenon. © 2010 Taylor & Francis Group, London.

Rocca M.L.,University Roma | Adduce C.,University Roma | Lombardi V.,University Roma | Sciortino G.,University Roma | Hinkelmann R.,TU Berlin
International Journal for Numerical Methods in Fluids | Year: 2012

In this paper the dynamics of a two-layered liquid, made of two immiscible shallow-layers of different density, has been investigated within the framework of the lattice Boltzmann method (LBM). The LBM developed in this paper for the two-layered, shallow-water flow has been obtained considering two separate sets of LBM equations, one for each layer. The coupling terms between the two sets have been defined as external forces, acted on one layer by the other. Results obtained from the LBM developed in this paper are compared with numerical results obtained solving the two-layered, shallow-water equations, with experimental and other numerical results published in literature. The results are interesting. First, the numerical results obtained by the LBM and by the shallow-water model can be considered as equivalent. Second, the LBM developed in this paper is able to simulate motion conditions on nonflat topography. Third, the agreement between the LBM (and also shallow-water model) numerical results and the experimental results is good when the evolution of the flow does not depend on the viscosity, that is, during the initial phase of the flow, dominated by gravity and inertia forces. When the viscous forces dominate the evolution of the flow the agreement between numerical and experimental results depends strongly on the viscosity; it is good if the numerical LBM viscosity has the same order of magnitude of the liquid's kinematic viscosity. © 2012 John Wiley & Sons, Ltd.

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