1,721,116 research outputs found
Comparison of anti-plane surface waves in strain-gradient materials and materials with surface stresses*
No full textHere we discuss the similarities and differences in anti-plane surface wave propagation in an elastic half-space within the framework of the theories of Gurtin–Murdoch surface elasticity and Toupin–Mindlin strain-gradient elasticity. The qualitative behaviour of the dispersion curves and the decay of the obtained solutions are quite similar. On the other hand, we show that the solutions relating to the surface elasticity model are more localised near the free surface. For the strain-gradient elasticity model there is a range of wavenumbers where the amplitude of displacements decays very slowly
Breve storia del "TAPIRO"
Full text linkIl Reattore Sorgente Veloce Taratura Pila Rapida a potenza zero (R.S.V. TAPIRO) fu concepito agli inizi degli anni ’60 dai ricercatori del Comitato Nazionale per l’Energia Nucleare (CNEN), come strumento di supporto al programma italiano sui reattori veloci. Dall’approvazione del progetto nel 1965, dopo solo 5 anni e mezzo, il 2 aprile del 1971 il TAPIRO produsse il suo primo flusso stabile di neutroni rag- giungendo la sua prima criticità. Da allora, il reattore nucleare di ricerca TAPIRO è stato utilizzato come sorgente di neutroni veloci per diverse attività di ricerca nell’ambito dell’aerospazio, della fusione nu- cleare, del bruciamento degli attinidi minori, degli acceleratori di particelle, della misura di sezioni d’urto, del danneggiamento biologico... Questo documento raccoglie la storia delle prime fasi di pro- gettazione e realizzazione dell’impianto e le principali attività effettuate nei successivi 50 anni. A com- pletare il documento c’è un elenco della documentazione tecnica prodotta nella fase di progettazione e delle pubblicazioni realizzate sulla base dei risultati sperimentali ottenuti con i neutroni prodotti dal TAPIRO.The zero-power fast research reactor TAPIRO was conceived in the early 1960s by the researchers of the Italian National Committee for Nuclear Energy (CNEN) to assist the Italian program on fast nuclear reactors. After the approval of the project in 1965, only 5 and a half years later, on April 2, 1971, TAPIRO provided its first stable neutron flux reaching its first criticality. Since then, the TAPIRO nuclear research reactor has been used as a source of fast neutrons for several research activities in the fields of aero-space, nuclear fusion, burning of mino years. To complete the document there is a list of the technical documentation produced in the design phase and actinides, particle accelerators, neutron cross sections measu- rement, biological damage.This document collects the history of the first phases of design and construction of the installation and the main activities carried out in the following 50 of the publications cresis of the experimental results obtained with the neutrons produced by TAPIRO
Surface/interfacial anti-plane waves in solids with surface energy
No full textIn this paper we discuss new type of surface anti-plane waves localized near the surface an elastic half-space and in the vicinity of plane interface between two half-spaces, when considering surface strain and kinetic energies. We also consider the case of non-perfect interface, i.e. when a jump of displacement or of its gradient, with the aim of modelling lacking of adhesion between solids. The phase velocity profiles and dispersion relations of surface waves are presented and several different material parameters are considered. Among the results, we observe an anomalous dispersion when the surface/interface is stiffer than the bulk material. These results can be exploited for the nondestructive characterization and the analysis of thin inter-phases between two solids, and can find several engineering applications
Transverse surface waves on a cylindrical surface with coating
Full text linkWe discuss the propagation of transverse surface waves that are so-called whispering-gallery waves along a surface of an elastic cylinder with coating. The coating is modelled in the framework of linearized Gurtin–Murdoch surface elasticity. Other interpretations of the surface shear modulus are given and relations to so-called stiff interface and stiff skin model are discussed. The dispersion relations are obtained and analyzed
Bifurcation analysis of a nonlinear piezoelectric beam subjected to combined conservative and nonconservative loads
No full textPropagation of linear compression waves through plane interfacial layers and mass adsorption in second gradient fluids
No full textThis paper addresses the problem of reflection and transmission of compression waves at the phase transition layer between the vapour and liquid phases of the same fluid. Within the framework of second gradient fluid modeling, we use a nonconvex free energy in order to describe the phase transition phenomenon. A stationary solution for the fluid density is found for an infinite domain, and an analytical expression for the phase transition is presented. Then the propagation of linear waves superposed to this stationary solution is discussed, with particular attention to the behaviour in correspondence of the interfacial layer. The reflection and transmission of waves is studied and analized with the aid of numerical simulations, and an interesting phenomenon of mass adsorption at the interface is observed and discussed
Bifurcation analysis of nonlinear piezoelectric controlled systems under nonconservative loads
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