# Física

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### Examinando Física por Materia "DINAMICA"

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Artículo de Publicación Periódica Active particles with desired orientation flowing through a bottleneck(2018-12) Parisi, Daniel; Cruz Hidalgo, Raúl; Zuriguel, IkerMás... "We report extensive numerical simulations of the flow of anisotropic self-propelled particles through a constriction. In particular, we explore the role of the particles’ desired orientation with respect to the moving direction on the system flowability. We observe that when particles propel along the direction of their long axis (longitudinal orientation) the flow-rate notably reduces compared with the case of propulsion along the short axis (transversal orientation). And this is so even when the effective section (measured as the number of particles that are necessary to span the whole outlet) is larger for the case of longitudinal propulsion. This counterintuitive result is explained in terms of the formation of clogging structures at the outlet, which are revealed to have higher stability when the particles align along the long axis. This generic result might be applied to many different systems flowing through bottlenecks such as microbial populations or different kind of cells. Indeed, it has already a straightforward connection with recent results of pedestrian (which self-propel transversally oriented) and mice or sheep (which self-propel longitudinally oriented)."Más... Artículo de Publicación Periódica Continuous-space automaton model for pedestrian dynamics(2011-05-11) Baglietto, Gabriel; Parisi, DanielMás... An off-lattice automaton for modeling pedestrian dynamics is presented. Pedestrians are represented by disks with variable radius that evolve following predefined rules. The key feature of our approach is that although positions and velocities are continuous, forces do not need to be calculated. This has the advantage that it allows using a larger time step than in force-based models. The room evacuation problem and circular racetrack simulations quantitatively reproduce the available experimental data, both for the specific flow rate and for the fundamental diagram of pedestrian traffic with an outstanding performance. In this last case, the variation of two free parameters (r min and rmax) of the model accounts for the great variety of experimental fundamental diagrams reported in the literature. Moreover, this variety can be interpreted in terms of these model parameters.Más... Artículo de Publicación Periódica Effect of physical distancing on the speed-density relation in pedestrian dynamics(2021-04) Echeverría Huarte, Iñaki; Garcimartín, Ángel; Parisi, Daniel; Martín-Gómez, CésarMás... "We report experimental results of the speed-density relation emerging in pedestrian dynamics when individuals keep a prescribed safety distance among them. To this end, we characterize the movement of a group of people roaming inside an enclosure varying different experimental parameters: (i) global density, (ii) prescribed walking speed, and (iii) suggested safety distance. Then, by means of the Voronoi diagram we are able to compute the local density associated to each pedestrian, which is afterward correlated with its corresponding velocity at each time. In this way, we discover a strong dependence of the speed-density relation on the experimental conditions, especially with the (prescribed) free speed. We also observe that when pedestrians walk slowly, the speed-density relation depends on the global macroscopic density of the system, and not only on the local one. Finally, we demonstrate that for the same experiment, each pedestrian follows a distinct behavior, thus giving rise to multiple speed-density curves."Más... Artículo de Publicación Periódica Effect of physical distancing on the speed–density relation in pedestrian dynamics(2021-04) Echeverría Huarte, Iñaki; Garcimartín, Ángel; Parisi, Daniel; Cruz Hidalgo, R.; Martín-Gómez, César; Zuriguel, IkerMás... "We report experimental results of the speed-density relation emerging in pedestrian dynamics when individuals keep a prescribed safety distance among them. To this end, we characterize the movement of a group of people roaming inside an enclosure varying different experimental parameters: (i) global density, (ii) prescribed walking speed, and (iii) suggested safety distance. Then, by means of the Voronoi diagram we are able to compute the local density associated to each pedestrian, which is afterward correlated with its corresponding velocity at each time. In this way, we discover a strong dependence of the speed-density relation on the experimental conditions, especially with the (prescribed) free speed. We also observe that when pedestrians walk slowly, the speed-density relation depends on the global macroscopic density of the system, and not only on the local one. Finally, we demonstrate that for the same experiment, each pedestrian follows a distinct behavior, thus giving rise to multiple speed-density curves."Más... Artículo de Publicación Periódica Pedestrian dynamics at the running of the bulls evidences an inaccessible region in the fundamental diagram(2021-09) Parisi, Daniel; Sartorio, Alan G.; Colonnello, Joaquín R.; Garcimartín, Ángel; Pugnaloni, Luis Ariel; Zuriguel, IkerMás... "We characterize the dynamics of runners in the famous “Running of the Bulls” Festival by computing the individual and global velocities and densities, as well as the crowd pressure. In contrast with all previously studied pedestrian systems, we unveil a unique regime in which speed increases with density that can be understood in terms of a time-dependent desired velocity of the runners. Also, we discover the existence of an inaccessible region in the speed–density state diagram that is explained by falls of runners. With all these ingredients, we propose a generalization of the pedestrian fundamental diagram for a scenario in which people with different desired speeds coexist."Más... Artículo de Publicación Periódica Physical distance characterization using pedestrian dynamics simulation(2022-01-22) Parisi, Daniel; Patterson, Germán; Pagni, Lucio; Osimani, Lucía; Bacigalupo, Tomás; Godfrid, Juan; Bergagna, Federico M.; Brizi, Manuel Rodríguez; Momesso, Pedro; Gómez, Fermín; Lozano, Jimena; Baader, Juan M.; Ribas, Ignacio; Astiz Meyer, Facundo; Di Luca, Miguel; Barrera, Nicolás Enrique; Keimel Álvarez, Ezequiel Martín; Herrán Oyhanarte, Maite Mercedes; Pingarilho, Pedro Remigio; Zuberbuhler, Ximena; Gorostiaga, FelipeMás... In the present work we study how the number of simulated customers (occupancy) af-fects social distance in an ideal supermarket, considering realistic typical dimensions and processing times (product selection and checkout). From the simulated trajectories we measure social distance events of less than 2 m, and their duration. Among other observ-ables, we define a physical distance coefficient that informs how many events (of a given duration) each agent experiences.Más... Artículo de Publicación Periódica Redefining the role of obstacles in pedestrian evacuation(2018) Garcimartín, Ángel; Maza, Diego; Pastor, José Martín; Parisi, Daniel; Martín-Gómez, César; Zuriguel, IkerMás... "The placement of obstacles in front of doors is believed to be an effective strategy to increase the flow of pedestrians, hence improving the evacuation process. Since it was first suggested, this counterintuitive feature is considered a hallmark of pedestrian flows through bottlenecks. Indeed, despite the little experimental evidence, the placement of an obstacle has been hailed as the panacea for solving evacuation problems. In this work, we challenge this idea and experimentally demonstrate that the pedestrians flow rate is not necessarily altered by the presence of an obstacle. This result—which is at odds with recent demonstrations on its suitability for the cases of granular media, sheep and mice differs from the outcomes of most of existing numerical models, and warns about the risks of carelessly extrapolating animal behaviour to humans. Our experimental findings also reveal an unnoticed phenomenon in relation with the crowd movement in front of the exit: in competitive evacuations, an obstacle attenuates the development of collective transversal rushes, which are hazardous as they might cause falls."Más...