9,352 research outputs found

    Phase Transitions in a Kinetic Flocking Model of Cucker-Smale Type

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    We consider a collective behavior model in which individuals try to imitate each others' velocity and have a preferred speed. We show that a phase change phenomenon takes place as diffusion decreases, bringing the system from a “disordered” to an “ordered” state. This effect is related to recently noticed phenomena for the diffusive Vicsek model. We also carry out numerical simulations of the system and give further details on the phase transition

    Trajectories of functioning and mental health: determinants in general population

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    Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Psiquiatría. Fecha de lectura: 17-10-201

    Particle interactions mediated by dynamical networks: assessment of macroscopic descriptions

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    We provide a numerical study of the macroscopic model of [3] derived from an agent-based model for a system of particles interacting through a dynamical network of links. Assuming that the network remodelling process is very fast, the macroscopic model takes the form of a single aggregation diffusion equation for the density of particles. The theoretical study of the macroscopic model gives precise criteria for the phase transitions of the steady states, and in the 1-dimensional case, we show numerically that the stationary solutions of the microscopic model undergo the same phase transitions and bifurcation types as the macroscopic model. In the 2-dimensional case, we show that the numerical simulations of the macroscopic model are in excellent agreement with the predicted theoretical values. This study provides a partial validation of the formal derivation of the macroscopic model from a microscopic formulation and shows that the former is a consistent approximation of an underlying particle dynamics, making it a powerful tool for the modelling of dynamical networks at a large scale

    Women’s disengagement from legal proceedings for intimate partner violence in southern Spain: Variables related to legal proceedings

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    This article studies the relationship between a set of variables related to the legal process and women’s disengagement from legal proceedings against their (ex)partners in Southern Spain. A total of 345 women answered a questionnaire. Results evidenced that request for a protection order (PO), granting such PO, imprisonment of the offender, and women’s perception of who decided during the process were significantly related to disengagement (medium effect size). In addition, a logistic regression model was developed to predict disengagement with two variables: granting a PO and women’s perception of who decided. Results are interpreted in terms of the necessity that the judicial system gives support, protects, and provides women with opportunities to participate in the recovery process.Junta de AndalucĂ­a 1071/0453Ministerio de EducaciĂłn, Cultura y Deporte (España) FPU15/0037

    Computation of the optimal relative pose between overlapping grid maps through discrepancy minimization

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    Grid maps are a common environment representation in mobile robotics. Many Simultaneous Localization and Mapping (SLAM) solutions divide the global map into submaps, forming some kind of graph or tree to represent the structure of the environment, while the metric details are captured in the submaps. This work presents a novel algorithm that is able to compute a physically feasible relative pose between two overlapping grid maps. Our algorithm can be used for correspondence search (data association), but also for integrating negative information in a unified way. This paper proposes a discrepancy measure between two overlapping grid maps and its application in a quasi Newton optimization algorithm, with the hypothesis that minimizing such discrepancy could provide useful information for SLAM. Experimental evidence is provided showing the high potential of the algorithm

    Asymptotic L1-decay of solutions of the porous medium equation to self-similarity

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    We consider the ïŹ‚ow of gas in an N -dimensional porous medium with initial density v0 (x) ≄ 0. The density v(x, t) then satisïŹes the nonlinear degenerate parabolic equation vt = ∆v m where m > 1 is a physical constant. Assuming that (1 + 2)v0(x)dx<∞,weprovethatv(x,t)behavesasymptotically,ast→∞,liketheBarenblatt−PattlesolutionV(2 )v0 (x) dx < ∞, we prove that v(x, t) behaves asymptotically, as t → ∞, like the Barenblatt-Pattle solution V ( , t). We prove that the L1 -distance decays at a rate t 1/((N+2)m−N) . Moreover, if N = 1, we obtain an explicit time decay for the L∞ distance at a suboptimal rate. The method we use is based on recent results we obtained for the Fokker-Planck equation [2], [3]
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