Altres
http://hdl.handle.net/2117/15797
2017-02-25T11:42:10ZSlope stability in slightly fissured claystones and marls
http://hdl.handle.net/2117/101574
Slope stability in slightly fissured claystones and marls
Alonso Pérez de Agreda, Eduardo; Pinyol Puigmartí, Núria Mercè
The paper deals with the behavior of some characteristic soft rocks found in the Iberian Peninsula. In geological terms, they belong to Tertiary basins, the Keuper period and the Jurassic-Cretacic transition. The discussion is organized around the following aspects: (a) the intact material and its brittle behavior; (b) the weathering action of atmospheric events; (c) the persistent discontinuities and scale effects; and (d) the modification of strength after failure. In all cases, instability phenomena are addressed in connection with several case histories. Regarding material brittleness and the initial stress state, two cases of first time failures are discussed. Practical implications concerning the selection of operative strength will be given. Field observations of the relevance of weathering and, also, on the rate of weathering, are given for a Weald claystone. Field observations emphasize the importance of sharp transitions between weathered and intact (or slightly weathered) levels. A recent long-term laboratory investigation on the nature of degradation will be summarized. Macroscopic variables such as stiffness and tensile strength have been found to be uniquely predicted by a degradation law in terms of the accumulated plastic deformations. Persistent discontinuities and, in particular, sedimentation planes play a dominant role to explain slope failures not related to the shallow failures, usually associated with weathered profiles. The strength of discontinuities in a Weald formation was investigated by means of tests performed at two scales. Finally, the evolution in time of residual strength induced by chemical actions, associated with groundwater flow, is highlighted in connection with actual field data of unstable slopes.
The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-014-0526-5
2017-02-24T19:56:47ZAlonso Pérez de Agreda, EduardoPinyol Puigmartí, Núria MercèThe paper deals with the behavior of some characteristic soft rocks found in the Iberian Peninsula. In geological terms, they belong to Tertiary basins, the Keuper period and the Jurassic-Cretacic transition. The discussion is organized around the following aspects: (a) the intact material and its brittle behavior; (b) the weathering action of atmospheric events; (c) the persistent discontinuities and scale effects; and (d) the modification of strength after failure. In all cases, instability phenomena are addressed in connection with several case histories. Regarding material brittleness and the initial stress state, two cases of first time failures are discussed. Practical implications concerning the selection of operative strength will be given. Field observations of the relevance of weathering and, also, on the rate of weathering, are given for a Weald claystone. Field observations emphasize the importance of sharp transitions between weathered and intact (or slightly weathered) levels. A recent long-term laboratory investigation on the nature of degradation will be summarized. Macroscopic variables such as stiffness and tensile strength have been found to be uniquely predicted by a degradation law in terms of the accumulated plastic deformations. Persistent discontinuities and, in particular, sedimentation planes play a dominant role to explain slope failures not related to the shallow failures, usually associated with weathered profiles. The strength of discontinuities in a Weald formation was investigated by means of tests performed at two scales. Finally, the evolution in time of residual strength induced by chemical actions, associated with groundwater flow, is highlighted in connection with actual field data of unstable slopes.Textile Roofs 2016: Report
http://hdl.handle.net/2117/101573
Textile Roofs 2016: Report
Llorens Duran, Josep Ignasi de
2017-02-24T17:45:14ZLlorens Duran, Josep Ignasi deReal-time model-based video stabilization for microaerial vehicles
http://hdl.handle.net/2117/101572
Real-time model-based video stabilization for microaerial vehicles
Aguilar Castillo, Wilbert Geovanny; Angulo Bahón, Cecilio
The emerging branch of micro aerial vehicles (MAVs) has attracted a great interest for their indoor navigation capabilities, but they require a high quality video for tele-operated or autonomous tasks. A common problem of on-board video quality is the effect of undesired movements, so different approaches solve it with both mechanical stabilizers or video stabilizer software. Very few video stabilizer algorithms in the literature can be applied in real-time but they do not discriminate at all between intentional movements of the tele-operator and undesired ones. In this paper, a novel technique is introduced for real-time video stabilization with low computational cost, without generating false movements or decreasing the performance of the stabilized video sequence. Our proposal uses a combination of geometric transformations and outliers rejection to obtain a robust inter-frame motion estimation, and a Kalman filter based on an ANN learned model of the MAV that includes the control action for motion intention estimation.
2017-02-24T17:11:41ZAguilar Castillo, Wilbert GeovannyAngulo Bahón, CecilioThe emerging branch of micro aerial vehicles (MAVs) has attracted a great interest for their indoor navigation capabilities, but they require a high quality video for tele-operated or autonomous tasks. A common problem of on-board video quality is the effect of undesired movements, so different approaches solve it with both mechanical stabilizers or video stabilizer software. Very few video stabilizer algorithms in the literature can be applied in real-time but they do not discriminate at all between intentional movements of the tele-operator and undesired ones. In this paper, a novel technique is introduced for real-time video stabilization with low computational cost, without generating false movements or decreasing the performance of the stabilized video sequence. Our proposal uses a combination of geometric transformations and outliers rejection to obtain a robust inter-frame motion estimation, and a Kalman filter based on an ANN learned model of the MAV that includes the control action for motion intention estimation.Image restoration using HOS and the Radon transform
http://hdl.handle.net/2117/101571
Image restoration using HOS and the Radon transform
Sayrol Clols, Elisa; Chrysostomos, Nikias; Gasull Llampallas, Antoni
The authors propose the use of higher-order statistics (HOS) to study the problem of image restoration. They consider images degraded by linear or zero phase blurring point spread functions (PSF) and additive Gaussian noise. The complexity associated with the combination of two-dimensional signal processing and higher-order statistics is reduced by means of the Radon transform. The projection at each angle is an one-dimensional signal that can be processed by any existing 1-D higher-order statistics-based method. They apply two methods that have proven to attain good one-dimensional signal reconstruction, especially in the presence of noise. After the ideal projections have been estimated, the inverse Radon transform gives the restored image. Simulation results are provided.
2017-02-24T17:05:43ZSayrol Clols, ElisaChrysostomos, NikiasGasull Llampallas, AntoniThe authors propose the use of higher-order statistics (HOS) to study the problem of image restoration. They consider images degraded by linear or zero phase blurring point spread functions (PSF) and additive Gaussian noise. The complexity associated with the combination of two-dimensional signal processing and higher-order statistics is reduced by means of the Radon transform. The projection at each angle is an one-dimensional signal that can be processed by any existing 1-D higher-order statistics-based method. They apply two methods that have proven to attain good one-dimensional signal reconstruction, especially in the presence of noise. After the ideal projections have been estimated, the inverse Radon transform gives the restored image. Simulation results are provided.Response by Álvarez-García et al. to Letters Regarding article, “Electrophysiological effects of selective atrial coronary artery occlusion in humans”
http://hdl.handle.net/2117/101570
Response by Álvarez-García et al. to Letters Regarding article, “Electrophysiological effects of selective atrial coronary artery occlusion in humans”
Álvarez-García, Jesus; Vives Borras, Miquel; Gomis Román, Pedro; Ordoñez Llanos, Jordi; Ferrero-Gregori, Andreu; Serra Peñaranda, Antoni; Cinca Cuscullola, Juan Maria
2017-02-24T16:53:53ZÁlvarez-García, JesusVives Borras, MiquelGomis Román, PedroOrdoñez Llanos, JordiFerrero-Gregori, AndreuSerra Peñaranda, AntoniCinca Cuscullola, Juan MariaNumerical and experimental study of ASR in concrete at the meso-level
http://hdl.handle.net/2117/101569
Numerical and experimental study of ASR in concrete at the meso-level
Liaudat, Joaquín; López Garello, Carlos María; Carol, Ignacio
In this paper, an ongoing research project on the mechanisms of concrete deterioration due to Alkali-Silica Reaction (ASR) is presented, together with some preliminary results. The research program includes both experimental and numerical modelling work.
The first part includes the development of two new experimental setups, one devoted to study the ASR expansion mechanisms at the level of a single matrix-aggregate interface and the other to the study of ASR expansions of cubic concrete specimens under triaxial confinement.
The second part includes the formulation and numerical implementation of a chemo-mechanical model for ASR expansions in concrete at the meso-level. The model considers three main diffusion/reaction field equations for the concentrations of silicates, calcium and alkalis in concrete pore solution, complemented by a number of chemical kinetics and chemical equilibrium equations. The volume fraction distribution of the solid constituents of the hardened cement paste and the reaction products evolve with the progress of the reaction, determining the diffusivity properties of the material and, eventually, inducing expansions.
2017-02-24T16:05:14ZLiaudat, JoaquínLópez Garello, Carlos MaríaCarol, IgnacioIn this paper, an ongoing research project on the mechanisms of concrete deterioration due to Alkali-Silica Reaction (ASR) is presented, together with some preliminary results. The research program includes both experimental and numerical modelling work.
The first part includes the development of two new experimental setups, one devoted to study the ASR expansion mechanisms at the level of a single matrix-aggregate interface and the other to the study of ASR expansions of cubic concrete specimens under triaxial confinement.
The second part includes the formulation and numerical implementation of a chemo-mechanical model for ASR expansions in concrete at the meso-level. The model considers three main diffusion/reaction field equations for the concentrations of silicates, calcium and alkalis in concrete pore solution, complemented by a number of chemical kinetics and chemical equilibrium equations. The volume fraction distribution of the solid constituents of the hardened cement paste and the reaction products evolve with the progress of the reaction, determining the diffusivity properties of the material and, eventually, inducing expansions.Solvation dynamics in water: 2. Energy fluxes on excited- and ground-state surfaces
http://hdl.handle.net/2117/101568
Solvation dynamics in water: 2. Energy fluxes on excited- and ground-state surfaces
Rey Oriol, Rosendo; Hynes, James T.
This series’ first installment introduced an approach to solvation dynamics focused on expressing the emission frequency shift (following electronic excitation of, and resulting charge change or redistribution in, a solute) in terms of energy fluxes, a work and power perspective. This approach, which had been previously exploited for rotational and vibrational excitation-induced energy flow, has the novel advantage of providing a quantitative view and understanding of the molecular-level mechanisms involved in the solvation dynamics via tracing of the energy flow induced by the electronic excitation’s charge change or redistribution in the solute. This new methodology, which was illustrated for the case in which only the excited electronic state surface contributes to the frequency shift (ionization of a monatomic solute in water), is here extended to the general case in which both the excited and ground electronic states may contribute. Simple monatomic solute model variations allow a discussion of the (sometimes surprising) issues involved in assessing each surface’s contribution. The calculation of properly defined energy fluxes/work allows a more complete understanding of the solvation dynamics even when the real work for one of the surfaces does not directly contribute to the frequency shift, an aspect further emphasizing the utility of an energy flux approach.
2017-02-24T16:03:23ZRey Oriol, RosendoHynes, James T.This series’ first installment introduced an approach to solvation dynamics focused on expressing the emission frequency shift (following electronic excitation of, and resulting charge change or redistribution in, a solute) in terms of energy fluxes, a work and power perspective. This approach, which had been previously exploited for rotational and vibrational excitation-induced energy flow, has the novel advantage of providing a quantitative view and understanding of the molecular-level mechanisms involved in the solvation dynamics via tracing of the energy flow induced by the electronic excitation’s charge change or redistribution in the solute. This new methodology, which was illustrated for the case in which only the excited electronic state surface contributes to the frequency shift (ionization of a monatomic solute in water), is here extended to the general case in which both the excited and ground electronic states may contribute. Simple monatomic solute model variations allow a discussion of the (sometimes surprising) issues involved in assessing each surface’s contribution. The calculation of properly defined energy fluxes/work allows a more complete understanding of the solvation dynamics even when the real work for one of the surfaces does not directly contribute to the frequency shift, an aspect further emphasizing the utility of an energy flux approach.Los retos de las aguas subterráneas en países en vías de desarrollo
http://hdl.handle.net/2117/101567
Los retos de las aguas subterráneas en países en vías de desarrollo
Folch Sancho, Albert; Closas, Alvar
2017-02-24T16:01:02ZFolch Sancho, AlbertClosas, AlvarUrban seismic risk index for Medellín, Colombia, based on probabilistic loss and casualties estimations
http://hdl.handle.net/2117/101566
Urban seismic risk index for Medellín, Colombia, based on probabilistic loss and casualties estimations
Salgado Gálvez, Mario Andrés; Zuloaga Romero, Daniela; Velásquez Villada, Cesar Augusto; Carreño Tibaduiza, Martha Liliana; Cardona Arboleda, Omar Dario; Barbat Barbat, Horia Alejandro
Medellín is the second largest city of Colombia with more than 2 million inhabitants according to the latest census and with more than 240,000 public and private buildings. It is located on an intermediate seismic hazard area according to the seismic zonation of Colombia although no destructive earthquakes have occurred having as a consequence low seismic risk awareness among its inhabitants. Using the results of a fully probabilistic risk assessment of the city with a building by building resolution level and considering the dynamic soil response, average annual losses by sectors as well as casualties and other direct effects are obtained and aggregated at county level. Using the holistic evaluation module of the multi-hazard risk assessment CAPRA platform, EvHo, a comprehensive assessment that considered the social fragility and lack or resilience at county level is performed making use of a set of indicators with the objective of capturing the aggravating conditions of the initial physical impact. The urban seismic risk index, USRi, is obtained at county level which is useful to communicate risk to decision-makers and stakeholders besides making easy identifying potential zones that can be problematic in terms of several dimensions of the vulnerability. This case study is an example of how a multidisciplinary research on disaster risk reduction helps to show how risk analysis can be of high relevance for decision-making processes in disaster risk management.
The final publication is available at Springer via http://dx.doi.org/10.1007/s11069-015-2056-4
2017-02-24T15:55:22ZSalgado Gálvez, Mario AndrésZuloaga Romero, DanielaVelásquez Villada, Cesar AugustoCarreño Tibaduiza, Martha LilianaCardona Arboleda, Omar DarioBarbat Barbat, Horia AlejandroMedellín is the second largest city of Colombia with more than 2 million inhabitants according to the latest census and with more than 240,000 public and private buildings. It is located on an intermediate seismic hazard area according to the seismic zonation of Colombia although no destructive earthquakes have occurred having as a consequence low seismic risk awareness among its inhabitants. Using the results of a fully probabilistic risk assessment of the city with a building by building resolution level and considering the dynamic soil response, average annual losses by sectors as well as casualties and other direct effects are obtained and aggregated at county level. Using the holistic evaluation module of the multi-hazard risk assessment CAPRA platform, EvHo, a comprehensive assessment that considered the social fragility and lack or resilience at county level is performed making use of a set of indicators with the objective of capturing the aggravating conditions of the initial physical impact. The urban seismic risk index, USRi, is obtained at county level which is useful to communicate risk to decision-makers and stakeholders besides making easy identifying potential zones that can be problematic in terms of several dimensions of the vulnerability. This case study is an example of how a multidisciplinary research on disaster risk reduction helps to show how risk analysis can be of high relevance for decision-making processes in disaster risk management.Multi-step derivative-free preconditioned Newton method for solving systems of nonlinear equations
http://hdl.handle.net/2117/101565
Multi-step derivative-free preconditioned Newton method for solving systems of nonlinear equations
Ahmad, Fayyaz
Preconditioning of systems of nonlinear equations modifies the associated Jacobian and provides rapid convergence. The preconditioners are introduced in a way that they do not affect the convergence order of parent iterative method. The multi-step derivative-free iterative method consists of a base method and multi-step part. In the base method, the Jacobian of the system of nonlinear equation is approximated by finite difference operator and preconditioners add an extra term to modify it. The inversion of modified finite difference operator is avoided by computing LU factors. Once we have LU factors, we repeatedly use them to solve lower and upper triangular systems in the multi-step part to enhance the convergence order. The convergence order of m-step Newton iterative method is m + 1. The claimed convergence orders are verified by computing the computational order of convergence and numerical simulations clearly show that the good selection of preconditioning provides numerical stability, accuracy and rapid convergence.
2017-02-24T15:53:27ZAhmad, FayyazPreconditioning of systems of nonlinear equations modifies the associated Jacobian and provides rapid convergence. The preconditioners are introduced in a way that they do not affect the convergence order of parent iterative method. The multi-step derivative-free iterative method consists of a base method and multi-step part. In the base method, the Jacobian of the system of nonlinear equation is approximated by finite difference operator and preconditioners add an extra term to modify it. The inversion of modified finite difference operator is avoided by computing LU factors. Once we have LU factors, we repeatedly use them to solve lower and upper triangular systems in the multi-step part to enhance the convergence order. The convergence order of m-step Newton iterative method is m + 1. The claimed convergence orders are verified by computing the computational order of convergence and numerical simulations clearly show that the good selection of preconditioning provides numerical stability, accuracy and rapid convergence.