Search results for "Railway"

Laser ultrasonics for defect evaluation on coated railway axles

2020

Abstract This scientific paper focuses on the application of an advanced non-destructive technique for an effective inspection of railway axles. The method pertains to ultrasonic techniques, which are widely used in the railway field. The experimental investigation was carried out on simulated defects tooled near the cross section reduction of the axle, in order to simulate fatigue cracks which, due to notch effect, can trigger crack propagation and axle failure. The aim of this research activity is to evaluate how efficiently the proposed technique detects defects and to verify its applicability to axles with a black coating for protection. In view of the experimental setup, comprising a p…

Spiral wave induced numerically using electrical stimulation and comparison with experimental results.

2010

Experiments in vitro on a Microelectrode Array (MEA) platform show that electrical stimulation can provoke the generation of spiral waves in cardiac tissue. Nevertheless, the conditions leading to this artificial fibrillation state remain unclear. In order to have a better understanding of this phenomenon, a numerical simulation study has been conducted. The results obtained with a two-dimensional FitzHugh-Nagumo model proved that it is possible to create spiral waves by adding a stimulation current under certain conditions, which are made explicit.

Intensity spiral patterns in a semiconductor microresonator

2005

Spiral waves appear frequently in nature. They have been studied, e.g., in hydrodynamic systems, chemical reactions, and in a large variety of biological and physical systems [Grill et al., Phys. Rev. Lett. 75, 3368 (1995); Goryachev and Kapral, Phys. Rev. Lett. 76, 1619 (1996)]. In contrast to chemical and hydrodynamic processes where the field amplitude exhibits the spiral patterns (intensity spirals), in optics the spiral structures relate generally to the phase structure of the optical field (so-called 'optical vortices' [Lugiato et al., Adv. At., Mol., Opt. Phys. 40, 229 (1999); Arecchi et al., Phys. Rep. 318, 1 (1999); Weiss et al., Appl. Phys. B:Lasers Opt. B68, 151 (1999)]). Thus th…

A new type of railway monoblock sleeper

2012

A railway sleeper is the structural element which transversally connects the two rails by means of fastening components, thus ensuring its gauge. Its additional function is to firmly secure the track to the ballast and to distribute the loads transferred from railway carriages to the ballast. One of the most important parameters in the characterisation of performances given by railway sleepers is represented by their lateral resistance to the sliding: the higher its value increases, the better the track stability becomes, thus reducing the frequency of maintenance interventions necessary to keep the superstructure efficient. This article focuses on the performance profile of an innovative r…

A MARKOVIAN MODEL AS A TOOL FOR OPTIMISATION OF MAINTENANCE INTERVENTIONS ON RAILWAYS LINES

2008

This paper is designed to develop a procedure which defines a planning criterion for railway superstructure maintenance by means of Markov decision processes. This methodology allows to formulate a specific policy  which carries out the best configuration of budget allocation (min. Ф), and at the same time to guarantee the highest efficiency level in the railway superstructure. Thanks to the dynamic programming technique applied to decision processes, the report has examined the possibility of establishing the best management policy in order to maintain adequate safety levels of implementation and quality speed levels, in the presence of budget constraints, thus optimizing the available re…

French railway history in geo-historical perspectives, infrastructure, demographic dynamics and territorial change

2014

International audience

Les traces de la vitesse entre réseau et territoire : approche géohistorique de la croissance du réseau ferroviaire français

2016

The interaction between space and network are frequently questioned in the academic literature, by asking the economical and demographical impacts of a new infrastructure, often studied at the scale of a project. This work aims to investigate the components of the interaction in both large spatial and temporal scales. The hypothesis is that the temporal depth and the national scale could bring new explanations. This work is based on the collect, the exploitation and the analysis of the large spatio-temporal database FRANcE (French Railway Network). It identifies all sections of the network since the 19th century and the population census. This database also contains the traces of the speed,…

Nuove stazioni, periferie e città

2016

L’infrastruttura contemporanea amplia e fa slittare il proprio campo semantico, trasformandosi definitivamente da artefatto tecnico di carattere titanico ed epico ad elemento riparatore dei tessuti urbani, flessibile, trasformabile. In questo quadro in mutazione, numerose esperienze negli ultimi trent’anni hanno affermato in Europa occidentale il ruolo dei grandi progetti ferroviari come vettori di trasformazione urbana. A quindici anni dall’avvio della prima stagione di concorsi internazionali banditi per le nuove stazioni dell’Alta Velocità in Italia, è possibile un bilancio volto non solo al semplice confronto dei risultati direttamente pertinenti la realizzazione e l’esercizio dell’oper…

Mechanical characterisation and 3D fractional viscoelastic modelling of railway sub-ballast rubberised asphalt

SAFETY PROBLEMS AND GLOBAL COMFORT IN RAILWAYS OPERATIONAL MANAGMENT

2008

In the planning process of a railway intervention and in its operational management, it needs to analyse carefully the relations between the different classes of variables constituting the complex system “vehicle-infrastructure-environment” to find the most suitable actions in optimisation the travelling comfort and safety, with respect for the ecosystem compatibilities. The problem can be tackled, in a systematic way, according to set theory and vector analysis, in a hyperspace Âd of d-dimension up to determining a characteristic global comfort vector that can be combined with each alternatives of intervention in the transport network examined. From this point of view, after the proper ach…