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Testo ufficiale letto prima della cerimonia della consegna del Diploma Honoris Causa all'architetto americano Peter Eisenman

Crack Detection in Railway Axle Using Horizontal and Vertical Vibration Measurements

In this paper, numerical investigations are carried out to assess the possible use of vibration measurements to identify the presence of a fatigue crack in railway axles. A non-linear finite element model of a cracked axle, reproducing the crack breathing mechanism, is introduced. The solid model of the axle is built in the ABAQUS FEM software and a crack is introduced in it. Numerical simulations are presented for two different types of axle: hollow ones, as in passenger trains, and solid ones, as in freight trains. Simulation are carried out for different possible locations of the crack and different measuring points for the monitoring equipment. Results indicate that the presence of a crack in the shaft affects not only the vertical vibration signal, but also the horizontal (perpendicular to the axle axis) one, generating harmonic components of bending vibration at frequencies that are multiple integers of the frequency of revolution of the axle. Results revealed also that the horizontal vibration provides promising indicators of axle fault development because the effect of various sources of disturbance, namely wheel out-of-roundness, can be more easily dealt with

Element-resolved x-ray ferrimagnetic and ferromagnetic resonance spectroscopy

We report on the measurement of element-specific magnetic resonance spectra at gigahertz frequencies using x-ray magnetic circular dichroism (XMCD). We investigate the ferrimagnetic precession of Gd and Fe ions in Gd-substituted Yttrium Iron Garnet, showing that the resonant field and linewidth of Gd precisely coincide with Fe up to the nonlinear regime of parametric excitations. The opposite sign of the Gd x-ray magnetic resonance signal with respect to Fe is consistent with dynamic antiferromagnetic alignment of the two ionic species. Further, we investigate a bilayer metal film, Ni$_{80}$Fe$_{20}$(5 nm)/Ni(50 nm), where the coupled resonance modes of Ni and Ni$_{80}$Fe$_{20}$ are separately resolved, revealing shifts in the resonance fields of individual layers but no mutual driving effects. Energy-dependent dynamic XMCD measurements are introduced, combining x-ray absorption and magnetic resonance spectroscopies.Comment: 16 pages, 8 figure

Studio idrogeologico del bacino del rio di Santa Caterina di Pittinuri(Cuglieri, Sardegna Centro-Occidentale)

The catchment area of the river Santa Caterina is located in western part of Montiferru, one of most important volcanic complex of Sardinia. In order to determine the water balance of the basin, the base flow rates of streams and springs were measured for the purpose of assessing groundwater reservoirs and dynamic storage by means of depletion law of hydrogeologic system. Because of the prevalence of volcanics rocks a study of lava flow and fracture systems was required to determine the main directions of growndwater flow. It was found that hydrogeologic and hydrographic watershed do not coincide. In fact a fair amount of water out flow through bedding planes various lava flows

Gender, smart mobility and COVID-19

The COVID-19 pandemic has strongly impacted people’s main routine, which certainly includes their mobility habits. This paper aims to assess the pandemic’s mobility impacts and whether these may have increased the already existing inequality between men and women. In particular, the variation of mode choice in a pre-COVID and post-COVID scenario is investigated, focusing on the use of transport mode defined as Smart Mobility. The analysis is performed on data collected in thirteen European countries between July and September 2020 through a survey designed using an intersectional approach. Responses are analyzed to highlight correlations between different factors affecting mobility changes: some interest is reserved to the modes used according to the journey scope (work, errand, shopping). Overall, results reveal more people walking for their daily journeys, while a significant decrease in the use of public transport is observed. Although these changes affect women more, the main reason behind this is the need for more safety in terms of low risk of contagion, irrespective of gender. A specific focus on using modes commonly associated with a Smart Mobility offer (such as shared modes, public transport, walking, and biking) reveals differences originating when comparing men and women responses and various age ranges.info:eu-repo/semantics/acceptedVersio

Experiments on crack propagation and threshold at defects in press-fits of railway axles

Fatigue strength under fretting fatigue is one of the open problems in the area of fatigue. In the case of railway wheel-axle press-fits, there are no records of recent failures because design rules are today based on making the shape of geometrical transitions the most stressed point. However, it is important to analyze correctly the acceptability of defects and micro-cracks at press-fits. In this paper, after a preliminary presentation of the results obtained by a new criterion for predicting the non-propagation of cracks under rolling contact fatigue conditions, a new series of experiments on full-scale axle press-fits containing artificial defects is presented and discussed. Results show the modified Dang Van criterion is adequate for describing the development of natural cracks and cracks from artificial defects. The latter, characterized by a depth of 250 350 m, are competitors of fretting cracks naturally developed from surface scars and surface damage

MIS 5e at San Giovanni di Sinis (Sardinia, Italy): Stratigraphy, U/Th dating and "eustatic" inferences

AbstractThe most representative Late Pleistocene ("Tyrrhenian") outcrop in Sardinia (San Giovanni di Sinis) was re-visited based on detailed sedimentological and stratigraphical analysis supported by U-series dating of fossil corals. The stratigraphy shows shoreface–backshore sandstones overlying an erosional surface cut on vertebrate-bearing layers. Facies analysis and sequence-stratigraphic approaches suggest "eustatic" changes during the overall depositional interval of the marine sequence. Disconformities distinguish two coastal units suggesting a lateral shifts of the depositional environments driven by millennial-scale frequency sea level fluctuations, never exceeding a maximum height +1 to +3 m and by a subsequent rise to +5 ÷ +5.5 m asl.These deposits have historically been assigned to MIS 5, on the basis of i) their palaeontological content (warm "Senegalese" fauna), ii) lithostratigraphic interpretations and iii) amino-acid, geochronological data and generally attributed to the high sea-level episode of MIS 5e sub-stage, through sequential interpretation. U-series measurements in colonies of Cladocora caespitosa from the main outcrop of San Giovanni di Sinis and other minor deposits from the eastern side of the isthmus and from Capo San Marco, yielded 230Th-ages confirming an assignment of the embedding sediments to MIS 5e.Similar measurements in a pelecypod valve (Cerastoderma sp.) and a vermetid colony at San Marco yielded much younger apparent ages, tentatively attributed to late "diagenetic" U-uptake processes. Both the first minor pulses and the most important "eustatic" pulse recorded at San Giovanni di Sinis cannot be assigned unequivocally to one of the MIS 5e sea-level oscillations proposed in the recent literature, due to dating inaccuracies and uncertainties, but it seems probable that it occurred during an early part of the interval

Nets, relations and linking diagrams

In recent work, the author and others have studied compositional algebras of Petri nets. Here we consider mathematical aspects of the pure linking algebras that underly them. We characterise composition of nets without places as the composition of spans over appropriate categories of relations, and study the underlying algebraic structures.Comment: 15 pages, Proceedings of 5th Conference on Algebra and Coalgebra in Computer Science (CALCO), Warsaw, Poland, 3-6 September 201

First results from an aging test of a prototype RPC for the LHCb Muon System

Recent results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge of about 0.45 C/cm$^2$, corresponding to about 4 years of LHCb running at the highest background rate. The performance of the chamber has been studied under several photon flux values exploiting a muon beam. A degradation of the rate capability above 1 kHz/cm$^2$ is observed, which can be correlated to a sizeable increase of resistivity of the chamber plates. An increase of the chamber dark current is also observed. The chamber performance is found to fulfill the LHCb operation requirements.Comment: 6 pages, 9 figures, presented at the International Workshop on Aging Phenomena in Gaseous Detectors'', DESY-Hamburg (Germany), October 200