Simplified estimation of the train resistance parameters: full scale experimental tests and analysis

A CEN standard (EN 14067-4, 2005) describes the methodologies for the assessment of the running resistance of railway vehicles starting from full-scale test measurements. According to this standard, the speed dependent terms of the equation of Davis [1] have to be determined by means of coasting tests. In this paper, a new method to estimate the running resistance coefficients from a full-scale coasting test is proposed and compared with the two methods proposed in the CEN standard (the regression method and the speed history identification method). The main advantage of this new method is that it does not require the railway line characteristics to be known and it will be shown that the new method is able to evaluate the coefficients with an accuracy equivalent to that of the other methods considered

Numerical and Experimental Analysis of the Pressure Signature for different High-Speed Trains

This paper describes a procedure for the validation of numerical codes able to reproduce the pressures in tunnel due to the passage of trains. In the first step, the parameters of the numerical code are set by matching the train-tunnel pressure signature measured during a single-passage of different types of train within the tunnel and in the second step, without changing the parameters, the crossing of two trains is simulated. Within the paper, the methodology is applied to the numerical mono-dimensional code DB-Tunnel while the experimental data are those collected during an experimental research programme carried out in the tunnel La Fornace, on the Italian high-speed railway from Roma to Firenze. The accuracy of the numerical code estimation is evaluated in terms of the maximum pressure generated in the tunnel by the train passing/crossing because this is the key parameter, according to the TSI standard for railway infrastructures

Aerodynamic loads in open air of high speed trains: Analysis of experimental data

The homologation of high-speed trains is a demanding and expensive procedure. In particular, the evaluation of train slipstream according to the standard TSI, 2008 is divided in two different test programmes: one concerning the workers at the trackside and the other studying the passengers standing on the platform. This paper presents some slipstream measurements performed on three high speed trains and a comparison between them. The objective is to investigate the slipstream on the platform and relate it to the flow measured at the trackside at the same height with respect to the top of the rail. This topic is currently under revision by the commission in charge of the TSI standard. Interesting evidence concerning the improvements of the aerodynamic performance of new-generation trains are highlighted

GaAs Sub-Micron and Nano Islands by Droplet Epitaxy on Si

Merging the high effi?ciency light emitting III-V semiconductors with the state-of-the-art Silicon based electronics is of great interest for the realization of new optoelectronic devices. Unfortunately the heteroepitaxial growth of GaAs thin ?films on Si is a diffi?cult task because of the di?fference in the lattice constant, the polar/non-polar surface interaction and the di?fference in the thermal expansion coeffi?cients. We present for the ?first time the MBE growth of GaAs nanostructures on Si substrates by Droplet Epitaxy (DE) [1,2]. We believe this growth method to be promising for the growth of high quality GaAs nanoislands directly on Silicon. In the DE, the substrate is irradiated by a Ga molecular beam fl?ux ?first, leading to the formation of numerous fi?ne Ga droplets with uniform size, which are subsequently crystallized into GaAs nanostructures by an As molecular beam supply. By changing the Ga droplets deposition temperature is possible to change independently the size and the density of the droplets, while by varying the As ?flux for the crystallization we can change the fi?nal shape of the GaAs nanocrystals. We present the results for the growth of GaAs on Si by DE where the density of the GaAs nanoislands was changed by two orders of magnitude, while the size is varied from around 200 nm to around 20 nm. Measurements by X-ray microanalysis in the TEM con- fi?rmed the reaction between Ga and As with formation of GaAs. This has also seen by the presence of Moir? fringes in the TEM images taken in the two beam di?raction mode. The discontinuities of some Moir? fringes would suggest the presence of dislocations

Wave function engineering in quantum dot-ring nanostructures

Modern nanotechnology allows producing, depending on application, various quantum nanostructures with the desired properties. These properties are strongly influenced by the confinement potential which can be modified, e.g., by electrical gating. In this paper we analyze a nanostructure composed of a quantum dot surrounded by a quantum ring. We show that depending on the details of the confining potential the electron wave functions can be located in different parts of the structure. Since the properties of such a nanostructure strongly depend on the distribution of the wave functions, varying the applied gate voltage one can easily control them. In particular, we illustrate the high controllability of the nanostructure by demonstrating how its coherent, optical, and conducting properties can be drastically changed by a small modification of the confining potential.Comment: 8 pages, 10 figures, 2 tables, revte

On situ vibration based structural health monitoring of a railway steel truss bridge: a preliminary numerical study

Railway network is subject to increasing travelling loads and traffic frequency. In addition, since most of the bridges were built in the last century, they are subject to ageing and degradation. It is therefore necessary to develop proper structural health monitoring systems that can support periodical visual inspections. In this context, direct monitoring systems represent an important and promising solution for structural health monitoring purposes. This paper is the result of a numerical study performed on a 3D FE bridge model based on an existing structure: the latter is a Warren truss railway bridge, located in Northern Italy, built few years after the end of the second world war. The purpose of the study is to numerically evaluate the effectiveness in damage detection and localization of different vibration-based techniques. This analysis has been performed for a set of different damage scenarios, suggested by the infrastructure managers

Erratum to: Concentric Multiple Rings by Droplet Epitaxy: Fabrication and Study of the Morphological Anisotropy

We present the Molecular Beam Epitaxy fabrication of complex GaAs/AlGaAs nanostructures by Droplet Epitaxy, characterized by the presence of concentric multiple rings. We propose an innovative experimental procedure that allows the fabrication of individual portions of the structure, controlling their diameter by only changing the substrate temperature. The obtained nanocrystals show a significant anisotropy between [110] and [1–10] crystallographic directions, which can be ascribed to different activation energies for the Ga atoms migration processes

Self-Assembled Local Artificial Substrates of GaAs on Si Substrate

We propose a self-assembling procedure for the fabrication of GaAs islands by Droplet Epitaxy on silicon substrate. Controlling substrate temperature and amount of supplied gallium is possible to tune the base size of the islands from 70 up to 250 nm and the density from 107 to 109 cm−2. The islands show a standard deviation of base size distribution below 10% and their shape evolves changing the aspect ratio from 0.3 to 0.5 as size increases. Due to their characteristics, these islands are suitable to be used as local artificial substrates for the integration of III–V quantum nanostructures directly on silicon substrate

Preliminary evaluation of infrastructure and mobility services in mega-event: the Italian case study

Mega-events play an important role in the urban agenda of contemporary metropolises. This importance lies in the fact that such events are seen as possible catalysts for the urban development of a metropolis and more generally of a territory, and an opportunity to establish them as global cities. The planning and programming of a mega-event can be a country's showcase on the international landscape, and the mobility sector plays a significant role in defining its success or failure. Transport infrastructure generally requires high resources for both construction and maintenance even after the event. Therefore, in order to ensure a good outcome, it needs to be planned strategically at multiple levels; this condition brings a benefit to both the host city and the community. The main purpose of this study is to analyze a mega event like the Olympic Games by highlighting the relationship between existing mobility solutions and sustainable solutions considering also the surrounding area. This is to enable the creation of new intelligent transportation options. The Olympic Games, in fact, can represent a valuable opportunity to modernize the existing infrastructure of a country by improving the level of service and quality. The study considers, on the one hand, the expected demand for transport during the event and, on the other, the specific features of the different solutions that can be adopted to meet mobility needs