### Examinando por Autor "Parisi, Daniel"

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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 Clogging transition of vibration-driven vehicles passing through constrictions(2017-12) Patterson, Germán; Fierens, Pablo Ignacio; Sangiuliano Jimka, Federico; König, Pablo; Garcimartín, Ángel; Zuriguel, Iker; Pugnaloni, Luis Ariel; Parisi, DanielMás... "We report experimental results on the competitive passage of elongated self-propelled vehicles rushing through a constriction. For the chosen experimental conditions, we observe the emergence of intermittencies similar to those reported previously for active matter passing through narrow doors. Noteworthy, we find that, when the number of individuals crowding in front of the bottleneck increases, there is a transition from an unclogged to a clogged state characterized by a lack of convergence of the mean clog duration as the measuring time increases. It is demonstrated that this transition—which was reported previously only for externally vibrated systems such as colloids or granulars—appears also for self-propelled agents. This suggests that the transition should also occur for the flow through constrictions of living agents (e.g., humans and sheep), an issue that has been elusive so far in experiments due to safety risks."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... Ponencia en Congreso Data-driven simulation for pedestrian avoiding a fixed obstacle(2019-07) Martin, Rafael F.; Parisi, DanielMás... "Data-driven simulation of pedestrian dynamics is an incipient and promising approach for building reliable microscopic pedestrian models. We propose a methodology based on generalized regression neural networks, which does not have to deal with a huge number of free parameters as in the case of multilayer neural networks. Although the method is general, we focus on the one pedestrian—one obstacle problem. The proposed model allows us to simulate the trajectory of a pedestrian avoiding an obstacle from any direction."Más... Artículo de Publicación Periódica Data-driven simulation of pedestrian collision avoidance with a nonparametric neural network(2020-02) Martin, Rafael F.; Parisi, DanielMás... "Data-driven simulation of pedestrian dynamics is an incipient and promising approach for building reliable microscopic pedestrian models. We propose a methodology based on generalized regression neural networks, which does not have to deal with a huge number of free parameters as in the case of multilayer neural networks. Although the method is general, we focus on the one pedestrian - one obstacle problem. Experimental data were collected in a motion capture laboratory providing high-precision trajectories. The proposed model allows us to simulate the trajectory of a pedestrian avoiding an obstacle from any direction. Together with the methodology specifications, we provide the data set needed for performing the simulations of this kind of pedestrian dynamic system."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... Ponencia en Congreso Elongated self-propelled particles roaming a closed arena present financial stylized facts(2019-07) Patterson, Germán; Parisi, DanielMás... "We report the existence of financial stylized facts in a system of mechanical vehicles driven by vibration (VDV). The VDVs are restricted to a closed geometry that is composed of two chambers connected by an opening which allows a continuous flow of agents between the two regions. We studied the temporal evolution of the density of particles around the opening and made a statistical comparison with the price evolution of bitcoin (BTC). We found remarkable similarities between these two systems enabling us to study financial systems from a new perspective."Más... Artículo de Publicación Periódica Flow of pedestrians through narrow doors with dierent competitiveness(2016) Garcimartín, Ángel; Parisi, Daniel; Pastor, José Martín; Martín-Gómez, César; Zuriguel, IkerMás... "We report a thorough analysis of the intermittent flow of pedestrians through a narrow door. The observations include five diferent sets of evacuation drills with which we have investigated the efect of door size and competitiveness on the flow dynamics. Although the outcomes are in general compatible with the existence of the faster-is-slower efect, the temporal evolution of the instantaneous flow rate provides evidence of new features. These stress the crucial role of the number of people performing the tests, which has an influence on the obtained results. Once the transients at the beginning and end of the evacuation are removed, we have found that the time lapses between the passage of two consecutive pedestrians display heavy-tailed distributions in all the scenarios studied. Meanwhile, the distribution of burst sizes decays exponentially; this can be linked to a constant probability of finding a long-lasting clog during the evacuation process. Based on these results, a discussion is presented on the caution that should be exercised when measuring or describing the intermittent flow of pedestrians through narrow doors."Más... Ponencia en Congreso Fusion of magnetic and WiFi fingerprints for indoor positioning(2018) Grisales Campeón, Juan Pablo; López, Sebastián; de Jesús Meleán, Sergio R.; Moldovan, Horatiu; Parisi, Daniel; Fierens, Pablo IgnacioMás... "WiFi received signal strength (RSS) and magnetic field intensity are common measures for indoor localization because they are readily available on most mobile devices. There is a vast literature on smartphone positioning using RSS and it has been widely implemented in real-world scenarios in the last two decades. There is much work done on localization aided by magnetic field measurements. We have recently evaluated the accuracy of RSS-based positioning applying state-of-the-art algorithms to measurements in a well-controlled experimental setup. In this paper, we extend this work to assess the accuracy improvements achievable by fusing WiFi and magnetic field information. We show that accuracy improvements of up to 30% are possible."Más... Ponencia en Congreso Indoor positioning based on RSSI of WiFi signals: how accurate can it be?(2019-02-20) Grisales Campeón, Juan Pablo; López, Sebastián; de Jesús Meleán, Sergio R.; Parisi, Daniel; Fierens, Pablo Ignacio; Moldovan, HermanMás... "There is abundant literature on positioning systems based on WiFi signals. Most of the systems with off-the-shelf hardware use RSSI measurements. In this paper, we try to determine the highest achievable accuracy of such systems. Instead of resorting to a theoretical analysis, e.g., Cram´er-Rao or Ziv-Zakai bounds, we apply state-of-the-art localization algorithms to measurements in a well-controlled experimental setup. We conclude that an accuracy of less than 1 meter seems unrealistic."Más... Artículo de Publicación Periódica Influence of bottleneck lengths and position on simulated pedestrian egress(2017-01) Parisi, Daniel; Patterson, GermánMás... "In this paper, the problem of pedestrian egress under di erent geometries is studied by means of two numerical models. The length of the bottleneck after the exit and the distance of the exit to the lateral wall of a squared room are investigated. Both models show that an increase in the bottleneck length increases the evacuation time by more than 20%, for any exit position. Hence, a bottleneck length tending to zero is the best choice. On the contrary, the results of moving the exit closer to the lateral wall are different in both models and, thus, its convenience cannot be stated. To unveil whether this layout modi cation is favorable, experimental data are required. Moreover, the discrepancy between models indicates that they should be validated considering several scenarios."Más... Artículo de Publicación Periódica Pedestrian collective motion in competitive room evacuation(2017-12) Garcimartín, Ángel; Pastor, José Martín; Martín-Gómez, César; Parisi, Daniel; Zuriguel, IkerMás... "When a sizable number of people evacuate a room, if the door is not large enough, an accumulation of pedestrians in front of the exit may take place. This is the cause of emerging collective phenomena where the density is believed to be the key variable determining the pedestrian dynamics. Here, we show that when sustained contact among the individuals exists, density is not enough to describe the evacuation, and propose that at least another variable-such as the kinetic stress-is required. We recorded evacuation drills with different degrees of competitiveness where the individuals are allowed to moderately push each other in their way out. We obtain the density, velocity and kinetic stress fields over time, showing that competitiveness strongly affects them and evidencing patterns which have been never observed in previous (low pressure) evacuation experiments. For the highest competitiveness scenario, we detect the development of sudden collective motions. These movements are related to a notable increase of the kinetic stress and a reduction of the velocity towards the door, but do not depend on the density."Más... Ponencia en Congreso Pedestrian collision avoidance with a local dynamic goal(2018-08-21) Martin, Rafael F.; Parisi, DanielMás... "We present here a general formalism for equipping simulated pedestrians with an avoidance mechanism. The central idea is to use a short-range target which is adjusted dynamically depending on the environment and thus modulating the desired velocity of the agent. This formulation can be implemented over any type of existing pedestrian model, being force-based or rule-based. As an example, we implement a simple instance of the formulation which is adjusted to reproduce previous reported and available experimental data of collision avoidance in scenarios of low density. The proposed minimal model shows good agreement with the real trajectories and other macroscopic observables."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 People counting using visible and infrared images(2020-10) Biagini, Martín; Filipic, Joaquín; Mas, Ignacio; Pose, Claudio D.; Giribet, Juan I.; Parisi, DanielMás... "We propose the use of convolutional neural networks (CNN) for counting and positioning people in visible and infrared images. Our data set is made of semi-artificial images created from real photographs taken from a drone using a dual FLIR camera. We compare the performance between CNN’s using 3 (RGB) and 4 (RGB+IR) channels, both under different lighting conditions. The 4-channel network responds better in all situations, particularly in cases of poor visible illumination that can be found in night scenarios. The proposed methodology could be applied to real situations when an extensive databank of 4-channel images will be available."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 Properties of balanced flows with bottlenecks: common stylized facts in finance and vibration-driven vehicles(2020-04-13) Patterson, Germán; Sornette, Didier; Parisi, DanielMás... "We study experimentally the properties of the flow of mechanical vibration-driven vehicles confined in two chambers connected through a narrow opening. We report that the density of particles around the opening presents critical behavior and scaling properties. By mapping this density to the financial market price, we document that the main stylized facts observed in financial systems have their counterparts in the mechanical system. The experimental model accurately reproduces financial properties such as scaling of the price fluctuation, volatility clustering, and multiscaling."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... Ponencia en Congreso Set-up of a method for people-counting using images from a UAV(2019-07-02) Parisi, Daniel; Giribet, Juan I.; Pose, Claudio D.; Mas, IgnacioMás... "We present a new method for obtaining the positions of each person attending an outdoor gathering. From this information it is possible to calculate the density field and the number of people. A dual-camera (visible + infrared (IR)) is mounted on an unmanned aerial vehicle (UAV). In this work, we only use the IR channel and present an initial set-up and calibration of the system along with the characterization of a small group of people."Más...