1 - 5 de 47
- ÍtemSocial distance characterization by means of pedestrian simulation(2022-09-10)In the present work, we study how the number of simulated clients (occupancy) affects the social distance in an ideal supermarket. For this, we account for realistic typical dimensions and process time (picking products and checkout). From the simulated trajectories, we measure events of social distance less than 2 m and its duration. Between other observables, we define a social distance coefficient that informs how many events (of a given duration) suffer each agent in the system. These kinds of outputs could be useful for building procedures and protocols in the context of a pandemic allowing to keep low health risks while setting a maximum operating capacity.
- ÍtemContinuous-space automaton model for pedestrian dynamics(2011-05-11)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.
- ÍtemNoise-assisted multibit storage device(2011-08-29)In this Letter we extend our investigations on noise-assisted storage devices through the experimental study of a loop composed of a single Schmitt trigger and an element that introduces a finite delay. We show that such a system allows the storage of several bits and does so more efficiently for an intermediate range of noise intensities. Finally, we study the probability of erroneous information retrieval as a function of elapsed time and show a way for predicting device performance independently of the number of stored bits.
- ÍtemModified nonlinear Schrödinger equation for frequency-dependent nonlinear profiles of arbitrary sign(2019)In recent times, materials exhibiting frequency-dependent optical nonlinearities, such as nanoparticle-doped glasses and other metamaterials, have gathered significant interest. The simulation of the propagation of intense light pulses in such media, by means of the nonlinear Schrödinger equation (NLSE), poses the problem in that straightforward inclusion of a frequency-dependent nonlinearity may lead to unphysical results, namely, neither the energy nor the photon number is conserved in general. Inspired by a simple quantum-mechanical argument, we derive an energy- and photon-conserving NLSE (pcNLSE). Unlike others, our approach relies only on the knowledge of the frequency-dependent nonlinearity profile and a generalization of Miller’s rule for nonlinear susceptibility, enabling the simulation of nonlinear profiles of arbitrary frequency dependence and sign. Moreover, the proposed pcNLSE can be efficiently solved by the same numerical techniques commonly used to deal with the NLSE. Relevant simulation results supporting our theoretical approach are presented.
- ÍtemJoint position and clock tracking of wireless nodes under mixed LOS-NLOS conditions(2022-10)We propose an algorithm for the simultaneous position and clock tracking of a wireless mobile node by a set of reference nodes. Based on a protocol similar to that of two-way ranging, our algorithm efficiently estimates the position and velocity of the mobile, and the skew and offset of its clock. We take into account that the propagation conditions between each reference node and the mobile change as the latter moves. In particular, changes between line-of-sight (LOS) and several non-line-of-sight (NLOS) scenarios are considered. We study the performance of our algorithm and compare it to other relevant proposals in the literature by means of simulations, showing that our proposed method improves localization accuracy.