Analysis of Lateral Displacements in Large Railway Viaducts Under Traffic Loads. Impact on Ride Safety and Passenger Comfort.

The increasing design speed of the new high speed lines and the stringent requirements on track alignment parameters are leading to a sustained increase of the number of railway viaducts. The relevant standards impose limiting values on lateral vibrations. Both the Spanish and European standards establish a minimum value for the first natural frequency of lateral vibration of a span, that should not be lower than fh0 = 1,2 Hz. This limit was originally proposed by ERRI committee D181, which assessed the lateral forces in railway bridges. This limit was proposed in order to avoid lateral resonance in railway vehicles going across the structure, taking into account that the frequencies of lateral vibration of railway vehicles are, in general, not greater than 1,0 Hz. In the case of large continuous viaducts with high piers, the lateral deformations occurring during a train pass-by can be significant and the natural frequencies of the first mode of vibration of the deck can be very low. In these cases it is not clear whether the required verifications must be applied to spans considered independently, to several successive spans or to the whole viaduct. There is currently no analysis methodology allowing to assess this situation and check the viaduct design against the requirements of ride safety and passenger comfort. This paper analyzes the lateral deformations of a large continuous viaduct and the infrastructure vehicle interaction effects due to the circulation of freight trains and several types of high speed train sat different speeds. The application of this methodology will allow an optimized design of viaducts with significant lateral deformations that cannot be justified only by using the simplified criteria of the current applicable standards. In such cases, the compliance with standards may lead to over dimensioning or in other cases to neglect the limits without the adequate verification of the proper infrastructure behavior once it has been commissioned. As it is the case for vertical deformations, for which the European standards require the assessment of dynamic effects, we stress the need for a dynamic analysis of the effects of lateral deformations in large railway viaducts

Uncoupled GPS Road Constrained Positioning based on Constrained Kalman Filtering

Car navigation systems take advantage of the synergies between the Global Positioning System (GPS) and digital road maps. For this kind of applications the digital road maps can provide a priori information to improve the positioning accuracy. This paper presents a method for the estimation of the user’s position, based on GPS positioning estimates, constrained to a road map. A low-cost GPS receiver was assumed as being the source of the positioning information. The techniques used in the proposed estimator were developed taking in consideration that the platforms where typically they would be implemented are characterized by having reduced computational capabilities. The algorithm’s positioning accuracy was characterized based on real data from a low-cost GPS receiver installed in a car. Different scenarios were used in the field trials in order to evaluate the impact of the satellite constellation visibility and geometry in the algorithm’s performance

Stabilization of Palygorskite Aqueous Suspensions Using Bio-Based and Synthetic Polyelectrolytes

Palygorskite is a natural fibrous clay mineral that can be used in several applications, for which colloidal stability in aqueous suspensions is a key point to improve its performance. In this study, methods of magnetic stirring, high-speed shearing, and ultrasonication, as well as different chemical dispersants, combined with these methods, namely carboxymethylcellulose, alginate, polyphosphate, and polyacrylate, were used to improve the dispersibility and the formation of stable suspensions of palygorskite in different conditions of pH. The stability and particle size of suspensions with a low concentration of palygorskite were evaluated by visual inspection, optical and electron microscopy, dynamic light scattering, and zeta potential measurements. Moreover, the palygorskite used in this work was initially characterized for its mineralogical, chemical, physical, and morphological properties. It was found that more stable suspensions were produced with ultrasonication compared to the other two physical treatments, with magnetic stirring being inefficient in all tested cases, and for higher pH values (pH of 12 and pH of 8, the natural pH of the clay) when compared to lower pH values (pH of 3). Remarkably, combined with ultrasonication, carboxymethylcellulose or in a lesser extent polyphosphate at near neutral pH allowed for the disaggregation of crystal bundles of palygorskite into individualized crystals. These results may be helpful to optimize the performance of palygorskite in several domains where it is applied.The present research was supported by the R&D project titled “FILCNF-New generation of composite films of cellulose nanofibrils with mineral particles as high strength materials with gas barrier properties” (PTDC/QUI-OUT/31884/2017, CENTRO 01-0145-FEDER-031884), Strategic Research Centre Project UIDB00102/2020, and Techn & Art (UID/05488/2018) funded by the Fundação para a Ciência e Tecnologia (FCT) and FEDER.info:eu-repo/semantics/publishedVersio

Effect of the dispersion state of minerals on the properties of cellulose nanofiber-based composite films

The dispersion state and the efficiency of the mixture of the different components in a composite film have an important impact on its mechanical and optical properties. In the present work, the impacts of different dispersion treatments on the disaggregation state of fibrous clay particles in water, and on the properties of related cellulose nanofiber (CNF)-based composite films, were evaluated. X-ray diffraction studies, performed on samples of sepiolite and palygorskite, revealed only minor changes in the diffraction pattern when the minerals were subjected to ultrasonic treatment, with or without the addition of different chemical dispersing agents. Conversely, microscopic studies revealed important differences in the dispersion state of the samples, induced by the addition of the different dispersants, showing an improvement in the disaggregation of the mineral crystals. The composite films prepared with sepiolite (and carboxymethylcellulose, as chemical dispersant) dispersed using ultrasonic treatment, and different types of CNF, showed improved optical and mechanical properties when compared with composites of the same counterparts prepared with sepiolite dispersed using a high-speed shear disperser.info:eu-repo/semantics/publishedVersio

A study of the lateral dynamic behaviour of high speed railway viaducts and its effect on vehicle ride comfort and stability

The study of the lateral behaviour of railway bridges and vehicles is an important issue on bridges with low lateral stiffness, which has been defined by ERRI (1996) as those with lateral natural frequencies below 1.2 Hz. This limit applies to the deformation of the deck in one span, and was demonstrated to be a real issue on measurements and models of bridges with open deck sections and supporting trusses, of low lateral bending stiffness for the deck. Although not included in the above category, modern long viaducts for HSR with continuous decks on tall piers may also exhibit very low lateral stiffness and frequencies, which could produce undesired effects for the comfort or even the stability of the railway vehicles. In this work a simple model has been developed and applied to consider worst-case scenarios in a representative bridge, the “Arroyo de las Piedras” viaduct in Spain. The trains considered are representative of those circulating in the Spanish HSR network, as well as a freight wagon. Threedimensional dynamic models were developed with finite elements. The actions considered include the lateral deformation of the bridge in response to vertical eccentric loads, track alignment irregularities and finally lateral motion of vehicles due to conicity of wheel-rail contact. The results show that there is, at least in this case, no cause for concern. However, for some scenarios the results in terms of lateral motion and forces are not negligible and should be considered in the design

El gran abanico aluvial del Guadiana alto. Reflexiones en torno al concepto de yacimiento

[ES] En el abanico aluvial del Guadiana Alto se documenta, en una enorme extensión, material arqueológico. El presente trabajo continúa y completa un estudio anterior insistiendo en la identificación de cadenas operativas y la realización de pruebas objetivas. El espacio en el que se dispersa la industria hace cuestionarse el concepto clásico de "yacimiento", lo que es abordado en último lugar.[EN] The Guadiana Alto is a big extensión with a lot of archeological material. This paper continué an anterior work, with special interest in the identification of operatoires chaines and objetive test. The área where lithic industry is distributed debates the classic idea of site

Simplificación Automática de las Imágenes a Partir de Expresiones Semi-Analíticas

Las etapas de simplificación de las imágenes, eliminación del ruido y realce de los bordes, son esenciales para las tareas posteriores de segmentación. Estas técnicas de procesado requieren, normalmente, de la sintonización de sus parámetros de control, situación incompatible con la segmentación automática. Esta ponencia trata de emplear un procesamiento, basado en difusión no lineal, capaz de auto sintonizarse mediante el uso de expresiones analíticas que relacionen los tiempos de difusión con el módulo del gradiente. Se exponen dos métodos numéricos y se presentan resultados experimentales en 1D, 2D y 3D

Analytic formulation for 3D diffusion tensor

This work deals with image processing based upon non-linear diffusion PDEs (Partial Differential Equations). Some analytic formulation will be introduced to obtain the 3D diffusion tensor, replacing Jacobi´s numerical methods by expressions based on invariants of the symmetric matrix. Later, CED (Coherence Enhancing Filtering) anisotropic filtering properties will be observed and will be combined with isotropic diffusion, providing a type of filtering that allows combining noise removal and local structure preservation. Last, some applications 3D grey-level will be presented

Solución Semi-analítica 1D para Funciones Uniparamétricas de Realce.

El proceso de realce resulta crucial en el análisis de imágenes. En esta contribución estudiamos el comportamiento numérico de filtros de difusión uniparamétricos que automaticen el estudio de estas imágenes. Para ello se propone la técnica de los tres píxeles que da lugar a una solución semianalítica del proceso de difusión no lineal con una función de difusión uniparamétric