Search results for "ROV"

The pressure-induced ringwoodite to Mg-perovskite and periclase post-spinel phase transition: a Bader’s topological analysis of the ab initio electro…

2011

In order to characterize the pressure-induced decomposition of ringwoodite (c-Mg2SiO4), the topological analysis of the electron density q(r), based upon the theory of atoms in molecules (AIM) developed by Bader in the framework of the catastrophe theory, has been performed. Calculations have been carried out by means of the ab initio CRYSTAL09 code at the HF/DFT level, using Hamiltonians based on the Becke- LYP scheme containing hybrid Hartree– Fock/density functional exchange–correlation terms. The equation of state at 0 K has been constructed for the three phases involved in the post-spinel phase transition (ringwoodite -> Mg-perovskite + periclase) occurring at the transition zone–lower…

Proposals for improvement of Annex I of Directive 92/43/ EEC: Central Italy

2021

The main purpose of the 92/43/EEC Habitats Directive is to contribute to the conservation of biodiversity, understood as habitat types and species of the flora and fauna of the European Union. To achieve this goal, natural and semi-natural biodiversity as a whole must be recognized and included in its annexes. As for the conservation of biotopes, named habitat types, Italy is unfortunately lacking as it the Annex I does not include important ecosystems that are typical of its territory, rare for biogeographical reasons or threatened. Therefore, the opportunity to identify a first list of significant habitats for central Italy is discussed here. For each of the new proposed types (new habita…

Bitumen stabilized ballast: a potential solution for railway track-bed

2016

Railway ballast degradation under dynamic loads progressively leads to loss of mechanical performance and geometry of the track, so that maintenance interventions are frequently needed. In order to system- atically avoid this issue, recently solutions have been proposed to reinforce track-bed by using polyur- ethane and/or resins as well as asphalt layers among others. Nonetheless, their main limitations are related to the high initial cost and low productivity. To cope with these limitations, in this study, bitumen stabilized ballast (BSB) is proposed as a new solu- tion for ballast stabilization. This method aims at improving durability and reducing settlement by mod- ifying both stiffnes…

A Dynamic Model of Ballasted Rail Track with Bituminous Sub-Ballast Layer

2012

AbstractThe bituminous sub-ballast layer within the ballasted rail track allows some mechanical and environmental advantages. An analytical model of a ballasted rail track with sub-ballast layer has been proposed by considering the rail as viscous-elastic continuous beam discretely supported, at four levels of elasticity.The model was used to compare the mechanical performance of both ballasted track with and without bituminous sub-ballast layer. The results confirmed that the bituminous sub-ballast layer reduces the dynamic forces on the ground and achieves the technical objectives as reduction of ground borne vibrations and increase of the design life of the rail track.

Novel performance-based technique for predicting maintenance strategy of bitumen stabilised ballast

2018

Abstract Despite being the most used worldwide, railway ballasted tracks presents high maintenance cost related to ballast settlement and particle degradation. With the aim of reducing life cycle costs, bitumen stabilised ballast (BSB) has been recently proposed as a relatively cheap alternative maintenance solution to be applied to existing tracks. This study aims at assessing the potential advantages of this technology, defining a novel maintenance strategy of traditional ballasted track-beds. A protocol for the application of the BSB technology and its associated maintenance strategy is defined. To estimate minor and major maintenance operations of BSB scenario in comparison to tradition…

A New High-Efficiency Procedure for Aggregate Gradation Determination of the Railway Ballast by Means Image Recognition Method

2013

Abstract The mechanical characteristics of the railway superstructure are related to the properties of the ballast, and especially to the particle size distribution of its grains. Under the constant stress-strain of carriages, the ballast can deteriorate over time, and consequently it should properly be monitored for safety reasons. The equipment which currently monitors the railway superstructure (like the Italian diagnostic train Archimede) do not make any “quantitative” evaluation of the ballast. The aim of this paper is therefore to propose a new methodology for extracting railway ballast particle size distribution by means of the image processing technique. The procedure has been teste…

Digital image analysis technique for measuring railway track defects and ballast gradation

2018

Abstract In order to guarantee safety and driving comfort and to maintain an efficient railway infrastructure, the first step is to carefully monitor the track geometry and wear level of the materials constituting the superstructure. To that end diagnostic trains are widely used on main lines, in that they can detect several geometric track parameters and rail wear, but under no circumstances they can yet detect ballast gradation. Due to the practical implications for the planning of maintenance operations on the railway network, this article presents a “DIP” digital image processing technique for measuring the transverse profile and corrugations of the rails as well as ballast gradation. T…

Effect of temperature and traffic on mix-design of bituminous asphalt for railway sub-ballast layer

2017

A wide integrated research has been carried out to assess the suitability of bituminous mixtures as the sub-ballast layer in railways. The influence of temperature on the mechanical characteristics and thermal susceptibility of the bituminous conglomerate—which forms sub-ballast layer of railway lines—has provided the motivation for carrying out a measurement of the thermal cycles in this layer. The evaluation of the average seasonal temperatures has proven to be well interpolated by sinusoidal functions, of which characteristic parameters are determined. To expand the validity of the study in different weather situations apart from Sicily, where the experiment was held, we proceeded to app…

Extact der Sämbelichen Landtäglichen Schlüssen de Anno MDCXVIII bis MDCCXLIV

1751

Einige Fragen an die Nordische Post: gestellt von dem Herausgeber der Livländischen Beiträge,18./30. November 1867

1868

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