Search results for "fluids"
showing 10 items of 1936 documents
Two relaxation times and thermal nonlinear waves along wires with lateral heat exchange
2021
Abstract We propose a model for studying several nonlinear waves for heat transport along a cylindrical system with lateral non-linear heat transfer to the environment. We consider relaxational equations, each with its own relaxation time, for longitudinal heat transfer and for lateral heat transfer across the wall. We consider two kinds of nonlinear lateral heat transport: radiative heat transport, and flux-limited heat transport. This work generalizes our previous studies in which the relaxation time for the lateral heat transfer was considered equal to that of the longitudinal heat flux. We explore the influence of both relaxation times on the propagation speed of linear and nonlinear wa…
Effect of disorder on Majorana localization in topological superconductors: a quasiclassical approach
2020
Two-dimensional (2D) topological superconductors (TS) host chiral Majorana modes (MMs) localized at the boundaries. In this work, we study the effect of disorder on the localization length of MMs in two-dimensional spin-orbit (SO) coupled superconductors within quasiclassical approximation. We find nonmonotonic behavior of the Majorana localization length as a function of disorder strength. At weak disorder, the Majorana localization length decreases with an increasing disorder strength. Decreasing the disorder scattering time below a crossover value ${\ensuremath{\tau}}_{c}$, the Majorana localization length starts to increase. The crossover scattering time depends on the relative magnitud…
Thermal-hydraulic behaviour of the DEMO divertor plasma facing components cooling circuit
2017
Abstract Within the framework of the Work Package DIV 1 – “Divertor Cassette Design and Integration” of the EUROfusion action, a research campaign has been jointly carried out by ENEA and University of Palermo to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. A comparative evaluation study has been performed considering three different options for the cooling circuit layout of the divertor Plasma Facing Components (PFCs). The potential improvement in the thermal-hydraulic performance of the cooling system, to be achieved by modifying cooling circuit layout, has been also assessed and discussed in terms of optimization strategy. The research acti…
The design of the DONES lithium target system
2019
Abstract In the framework of the EU fusion roadmap implementing activities, an accelerator-based Li(d,xn) neutron source called DONES (Demo-Oriented early NEutron Source) is being designed within the EUROfusion Work Package Early Neutron Source as an essential irradiation facility for testing candidate materials for DEMO reactor and future fusion power plants. DONES will employ a high speed liquid lithium jet struck by a 125 mA, 40 MeV deuteron beam to generate the intense neutron flux used to irradiate the material samples up to the desired level of displacement damage (˜10 dpa/fpy for iron in 0.3 l) and He production rates (˜10-13 appm He/dpa). In order to rapidly achieve a sound and stab…
Parametric study of the influence of First Wall cooling water on the Water Cooled Lithium Lead Breeding Blanket nuclear response
2019
Abstract In the framework of EUROfusion Work Package International Cooperation R&D activities, a close collaboration has been started among University of Palermo, ENEA Brasimone and ENEA Frascati for the development of the Water Cooled Lithium Lead (WCLL) Breeding Blanket (BB) concept. In this context, a research campaign has been carried out at the University of Palermo in order to investigate the influence of First Wall (FW) cooling water configuration on the nuclear response of the WCLL BB under irradiation in EU-DEMO, in order to gain useful indications for the WCLL BB pre-conceptual designs. To this end, three-dimensional nuclear analyses have been performed by MCNP5 v. 1.6 Monte Carlo…
HOW TO MAKE A PIE: REPRODUCIBLE RESEARCH FOR EMPIRICAL ECONOMICS AND ECONOMETRICS
2020
Les recherches empiriques en sciences humaines et sociales necessitent la manipulation de nombreux fichiers : differents jeux de donnees, de multiples programmes, qu'ils soient destines a la manipulation de donnees, aux traitements statistiques, aux estimations econometriques ou a des simulations, et de nombreux fichiers successifs de resultats. Maitriser l’ensemble des etapes du projet de recherche est indispensable si l’on souhaite pouvoir reproduire ou repliquer les resultats a long terme. Cette rigueur (fiabilite, tracabilite, reproductibilite), est desormais de plus en plus exigee par notre profession ainsi que par les editeurs de revues scientifiques. Apres avoir mis en evidence les e…
Wronskian representation of solutions of NLS equation, and seventh order rogue wave.
2012
This work is a continuation of a recent paper in which we have constructed a multi-parametric family of the nonlinear Schrodinger equation in terms of wronskians. When we perform a special passage to the limit, we get a family of quasi-rational solutions expressed as a ratio of two determinants. We have already construct Peregrine breathers of orders N=4, 5, 6 in preceding works; we give here the Peregrine breather of order seven.
Three-dimensional splitting dynamics of giant vortices in Bose-Einstein condensates
2018
We study the splitting dynamics of giant vortices in dilute Bose-Einstein condensates by numerically integrating the three-dimensional Gross-Pitaevskii equation in time. By taking advantage of tetrahedral tiling in the spatial discretization, we decrease the error and increase the reliability of the numerical method. An extensive survey of vortex splitting symmetries is presented for different aspect ratios of the harmonic trapping potential. The symmetries of the splitting patterns observed in the simulated dynamics are found to be in good agreement with predictions obtained by solving the dominant dynamical instabilities from the corresponding Bogoliubov equations. Furthermore, we observe…
Impact of buffer gas quenching on the $^1S_0$ $\to$ $^1P_1$ ground-state atomic transition in nobelium
2017
International audience; Using the sensitive Radiation Detected Resonance Ionization Spectroscopy (RADRIS) techniquean optical transition in neutral nobelium (No, Z = 102) was identified. A remnant signal when delaying the ionizing laser indicated the influence of a strong buffer gas induced de-excitation of the optically populated level. A subsequent investigation of the chemical homologue, ytterbium (Yb, Z = 70), enabled a detailed study of the atomic levels involved in this process, leading to the development of a rate equation model. This paves the way for characterizing resonance ionization spectroscopy (RIS) schemes used in the studyof nobelium and beyond, where atomic properties are c…
A nonlinear oscillators network devoted to image processing
2004
A contrast enhancement and image inverting tool using a lattice of uncoupled nonlinear oscillators is proposed. We show theoretically and numerically that the gray scale picture contrast is strongly enhanced even if this one is initially very small. An image inversion can be also obtained in real time with the same Cellular Nonlinear Network (CNN) without reconfiguration of the network. A possible electronic implementation of this CNN is finally discussed.