Hydrodynamical Models of Superfluid Turbulence

This review paper puts together some of our results concerning the application of non equilibrium Thermodynamics to superfluid liquid helium. Two of the most important situations of this quantum fluid are rotating superfluid and superfluid turbulence, both characterized by the presence of quantized vortices (vortex lines whose core is about 1 Angstrom and the quantum of circulation is $h/m$, $h$ being the Plank's constant and $m$ the mass of helium atom). In the first part of the work a non-standard model of superfluid helium, which considers heat flux as independent variable, is briefly recalled, and compared with the well known two-fluid model, in absence of vortices, proposed by Tisza and Landau more than half a century ago. The model is generalized taking into account the presence of vortices in different cases of physical interest: rotating superfluids, counterflow superfluid turbulence (a particular situation in which no mass flux but only heat flux is present) and combined situations of counterflow and rotation. Since vortices are not fixed when all the hydrodynamical fields change, an additional scalar quantity, the averaged vortex line density per unit volume $L$, {\it line density} for short, is introduced in the model as a new field variable and an evolution equation is written for it, both in linear and in nonlinear regimes, via Extended Thermodynamics. Finally, to encompass more general situations, the model is further extended considering the flux of vortex line density as an independent new variable. In all these models the propagation of harmonic waves is studied, motivated by the fact that vortex lines density is experimentally detected via the attenuation of second sound. A new kind of waves, vortex density waves, is also dealt with

Education in mine waste engineering: the experience of "SIGEO" Master's Course

On 19th July 1985 the failure of two tailings dams at the service of a fluorite mine in the Stava Valley (Italy) caused the death of 268 people and severe environmental and socioeconomic damage. Similar accidents have happened in Sgorigrad (Bulgaria, 1966), Aberfan (U.K., 1966), Buffalo Creek (USA, 1972), Aznalcollar (Spain, 1998), Taoshi (China, 2008) and many other places worldwide. The European Union has recognized the seriousness of the problems concerning the management and disposal of mining waste (over 400 million tonnes per year worldwide). With the 2006/21/CE Directive, the EU has urged all member States to carry out censuses, monitoring and consolidation of existing structures under the supervision of qualified experts. These experts should be provided with interdisciplinary knowledge that is difficult to attain during normal degree courses. For this reason, the Trento and Modena-Reggio Emilia Universities and the Turin Polytechnic have set up a post-graduate Master’s Course in “Analysis and Management of Geotechnical Structures”. The article describes the interdisciplinary approach adopted in the course and aims to stimulate the sharing of this initiative among other European Universities

Vortex dynamics in rotating counterflow and plane Couette and Poiseuille turbulence in superfluid Helium

An equation previously proposed to describe the evolution of vortex line density in rotating counterflow turbulent tangles in superfluid helium is generalized to incorporate nonvanishing barycentric velocity and velocity gradients. Our generalization is compared with an analogous approach proposed by Lipniacki, and with experimental results by Swanson et al. in rotating counterflow, and it is used to evaluate the vortex density in plane Couette and Poiseuille flows of superfluid helium.Comment: 18 pages, 2 figure

GraphFind: enhancing graph searching by low support data mining techniques

<p>Abstract</p> <p>Background</p> <p>Biomedical and chemical databases are large and rapidly growing in size. Graphs naturally model such kinds of data. To fully exploit the wealth of information in these graph databases, a key role is played by systems that search for all exact or approximate occurrences of a query graph. To deal efficiently with graph searching, advanced methods for indexing, representation and matching of graphs have been proposed.</p> <p>Results</p> <p>This paper presents GraphFind. The system implements efficient graph searching algorithms together with advanced filtering techniques that allow approximate search. It allows users to select candidate subgraphs rather than entire graphs. It implements an effective data storage based also on low-support data mining.</p> <p>Conclusions</p> <p>GraphFind is compared with Frowns, GraphGrep and gIndex. Experiments show that GraphFind outperforms the compared systems on a very large collection of small graphs. The proposed low-support mining technique which applies to any searching system also allows a significant index space reduction.</p

Dynamic finite element analysis of interceptive devices for falling rocks

The widespread use of net barriers, which are flexible, as opposed to rigid, devices for intercepting falling rocks has led to the need for rigorous design criteria based on safe and sound theoretical methods. Consistently with current practice, full-scale experimental tests are necessary in order to assess the reliability of any such barrier. Here, a new simulation approach based on numerical methods is presented: the analysis of a complete typical falling-rock event has been performed, to study the response of these interceptive devices. A commercial finite element code featuring explicit dynamic capabilities, particularly useful when modelling high-speed phenomena has been used. The simplifying assumptions along with the model geometrical and mechanical data are discussed. Both single net panel and complete barrier simulations are presented. In the latter case, the results are compared with some experimental data obtained from in situ testing. The results of the numerical simulations highlight some limitations in the testing methods which are currently accepted, and suggest the use of new parameters to more precisely characterize the behaviour of such interceptive devices for falling rocks. The benefits of numerical simulations as supplements to or substitutes for full-scale crash tests are emphasized particularly for design or parametric studies

Interaction of Extremely Slow Landslides with Transport Structures in the Alpine Glacial Isarco Valley

This paper describes three cases of extremely slow landslides located in the Isarco Valley, and interacting with major transport infrastructures connecting Italy to the central Europe: SS12 State Road, A22 (E45) Motorway, Verona-Brennero railway, high-speed railway network TNT-T5. Field measurements of displacements and pore water pressure were carried out to understand the mechanism of landslide evolution and the interaction with the transport structures. In particular, mobile inclinometers, IPIs, direct pendula and Total Station were used for monitoring the subsurface or structure movements. The landslides were classified as complex landslides. Two of them are associated to DGSDs phenomena. Field and remote measurements of displacements revealed that the interaction with the transport infrastructures was due to deep rotational/translational slides as partial reactivations of the DGSDs. The residual shear strength was developed on the sliding surfaces and therefore these landslides may be classified as active landslides

INDAGINE SPERIMENTALE E ANALISI TEORICA DEL COMPORTAMENTO MECCANICO DI GEOSINTETICI

Vengono illustrati i risultati di una indagine sperimentale per la caratterizzazione meccanica di geosintetici e vengono altresì riportati i primi risultati di una modellazione teorica del comportamento meccanico degli stessi. In particolare, nove tipologie di geotessili (di cui sei geotessili nontessuti e tre geotessili tessuti) sono stati sottoposti a prova di trazione non confinata a banda larga e a prova di punzonamento statico (metodo CBR). Nella presente nota si descrivono inoltre le apparecchiature utilizzate, le modalità operative delle prove e le tecniche di misura adottate