Modeling wave propagation through an analytical surface model

Nowadays there is a certain development in the use of railway, especially in the form of trams and underground lines in urban areas. Despite its many advantages, this kind of transport is a significant source of vibrations, which may affect residents and buildings near to the track. Wave transmission through the ground is therefore a phenomenon of particular interest. The object of this article is to formulate and test an analytical model of vibration propagation through the terrain surface. The model is based on the wave equation and takes into account wave scattering and reflection in the interfaces between different soil layers. A sensitivity analysis of its main parameters is carried out, and then a comprehensive set of simulations is made to test model performance and analyze factors such as load magnitude and velocity or soil configuration. The model has proved to be an interesting instrument to study the vibration phenomenon from a theoretical point of view and some improvements are proposed to turn it into a tool for engineers and designers

New Transition Wedge Design Composed by Prefabricated Reinforced Concrete Slabs

[EN] Important track degradation occurs in structure-embankment transitions, in which an abrupt change in track vertical stiffness arises, leading to a reduction in passengers comfort and safety. Although granular wedges are suggested by different railroad administrations as a solution to avoid these problems, they present some disadvantages which may affect track long-term performance. In this paper, a new solution designed with prefabricated reinforced concrete slabs is proposed. The aim of this solution is to guarantee a continuous and gradual track vertical stiffness transition in the vicinity of structures, overcoming granular wedges disadvantages. The aim of this study is to assess the performance of the novel wedge design by means of a 3-D FEM model and to compare it with the current solution.Real Herráiz, JI.; Zamorano-Martín, C.; Real-Herraiz, TP.; Morales-Ivorra, S. (2016). New Transition Wedge Design Composed by Prefabricated Reinforced Concrete Slabs. Latin American Journal of Solids and Structures. 13(8):1431-1449. doi:10.1590/1679-78252556S14311449138Gallego Giner, I., & López Pita, A. (2009). Numerical simulation of embankment—structure transition design. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 223(4), 331-343. doi:10.1243/09544097jrrt234Gallego, I., Muñoz, J., Rivas, A., & Sánchez-Cambronero, S. (2011). Vertical Track Stiffness as a New Parameter Involved in Designing High-Speed Railway Infrastructure. Journal of Transportation Engineering, 137(12), 971-979. doi:10.1061/(asce)te.1943-5436.0000288Insa, R., Salvador, P., Inarejos, J., & Roda, A. (2011). Analysis of the influence of under sleeper pads on the railway vehicle/track dynamic interaction in transition zones. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 226(4), 409-420. doi:10.1177/0954409711430174Li, D., & Davis, D. (2005). Transition of Railroad Bridge Approaches. Journal of Geotechnical and Geoenvironmental Engineering, 131(11), 1392-1398. doi:10.1061/(asce)1090-0241(2005)131:11(1392)Pita, A. L., Teixeira, P. F., & Robuste, F. (2004). High speed and track deterioration: The role of vertical stiffness of the track. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 218(1), 31-40. doi:10.1243/095440904322804411Molatefi, H., & Izadbakhsh, S. (2013). Continous rail absorber design using decay rate calculation in FEM. Structural Engineering and Mechanics, 48(4), 455-466. doi:10.12989/sem.2013.48.4.455Montalbán, L., Real, J., & Real, T. (2012). Mechanical characterization of railway structures based on vertical stiffness analysis and railway substructure stress state. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 227(1), 74-85. doi:10.1177/0954409712452348Montalbán Domingo, L., Real Herraiz, J. I., Zamorano, C., & Real Herraiz, T. (2014). Design of a new high lateral resistance sleeper and performance comparison with conventional sleepers in a curved railway track by means of finite element models. Latin American Journal of Solids and Structures, 11(7), 1238-1250. doi:10.1590/s1679-78252014000700009Montalbán Domingo, L., Zamorano Martín, C., Palenzuela Avilés, C., & Real Herráiz, J. I. (2014). Analysis of the Influence of Cracked Sleepers under Static Loading on Ballasted Railway Tracks. The Scientific World Journal, 2014, 1-10. doi:10.1155/2014/363547Real, J. I., Gómez, L., Montalbán, L., & Real, T. (2012). Study of the influence of geometrical and mechanical parameters on ballasted railway tracks design. Journal of Mechanical Science and Technology, 26(9), 2837-2844. doi:10.1007/s12206-012-0734-7Shan, Y., Albers, B., & Savidis, S. A. (2013). Influence of different transition zones on the dynamic response of track–subgrade systems. Computers and Geotechnics, 48, 21-28. doi:10.1016/j.compgeo.2012.09.006Shi, J., Burrow, M. P. N., Chan, A. H., & Wang, Y. J. (2012). Measurements and simulation of the dynamic responses of a bridge–embankment transition zone below a heavy haul railway line. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 227(3), 254-268. doi:10.1177/095440971246097

Galactic Archaeology with CoRoT and APOGEE: Creating mock observations from a chemodynamical model

In a companion paper, we have presented the combined asteroseismic-spectroscopic dataset obtained from CoRoT lightcurves and APOGEE infra-red spectra for 678 solar-like oscillating red giants in two fields of the Galactic disc (CoRoGEE). We have measured chemical abundance patterns, distances, and ages of these field stars which are spread over a large radial range of the Milky Way's disc. Here we show how to simulate this dataset using a chemodynamical Galaxy model. We also demonstrate how the observation procedure influences the accuracy of our estimated ages.Comment: 5 pages, 6 figures. To appear in Astronomische Nachrichten, special issue "Reconstruction the Milky Way's History: Spectroscopic surveys, Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J. Montalb\'an, and M. Steffe

African American Vernacular English : a representation of a non-mainstream variety of English in Kathryn Stockett's The Help

Non-mainstream varieties are sometimes stereotyped when they are represented in a piece of fiction work. African American Vernacular English is presumably one of the varieties which is subject to this uncharacteristic portrayal. The purpose of the paper was to analyse the morphological and syntactic properties of this non-standard variety in The Help and determine whether this could be faithfully portrayed in this novel. The two main characters that were studied were Aibileen and Minny who are African American speakers. Half of the chapters belonging to these characters were analysed. The results suggest that Aibileen and Minny exhibit some interesting differences in their speech, but the novel properly reflected African American's speech in a fair manner.Les varietats no estàndard són a vegades estereotipades quan es tracta de representar-les a una novel·la. L'anglès afroamericà és probablement una de les varietats en la qual es contempla aquesta representació poc característica. L'objectiu d'aquest treball consisteix en analitzar les propietats morfològiques i sintàctiques de l'anglès afroamericà a The Help i en determinar si aquesta varietat no estàndard es troba fidelment representada a la novel·la. Els dos personatges que es van estudiar són Aibileen i Minny, les quals són parlants d'aquesta varietat. La meitat dels capítols en els que apareixen aquests personatges van ser analitzats. Els resultats d'aquest estudi mostren que Aibileen i Minny presenten algunes diferències interessants en relació a l'ús del llenguatge, però la novel·la va resultar ser una bona representació de la llengua dels afroamericans

Design and validation of a railway inspection system to detect lateral track geometry defects based on axle-box accelerations registered from in-service trains

Metropolitan railway transport has become an efficient solution to the mobility necessities in urban areas. Railway track maintenance tasks have to be improved and adjusted to metropolitan requirements, in particular the few hours available to operate due to the high frequency service offered. This paper describes and proposes an inertial monitoring system to detect and estimate track irregularities by using in-service vehicles. A new maintenance strategy is established, based on the railway track conditions and continuous monitoring is provided to do so. The system proposed consists of at least two accelerometers mounted on the bogie axle-box and a GPS (Global Positioning System). Lateral accelerations have been analyzed to study gauge and lateral alignment deviations. Accelerations have been treated and processed by high-pass filtering and validation has been carried out by comparison with measurements provided by a track monitoring trolley. Measurements were made on Line 1 of the Alicante metropolitan and tram network (Spain)

Railway traffic induced vibrations: comparison of analytical and finite element models

The recent increase in the use of the railway and the establishment of more restrictive policies of harmful environmental effects of railway transport highlights the need to investigate ground vibrations related to trains. Therefore models to evaluate how this phenomenon affects have been performed. This article aims to expose both analytical and 3D-FE models and to compare theoretical formulation and results. Models have been calibrated and validated with real data. Furthermore, a simulation of the acceleration level of different railway infrastructure elements has been achieved

Light elements in stars with exoplanets

It is well known that stars orbited by giant planets have higher abundances of heavy elements when compared with average field dwarfs. A number of studies have also addressed the possibility that light element abundances are different in these stars. In this paper we will review the present status of these studies. The most significant trends will be discussed.Comment: 10 pages, 6 figures. Submitted to the proceedings of IAU symposium 268: Light elements in the universe