Scale invariance in natural and artificial collective systems : a review

Self-organized collective coordinated behaviour is an impressive phenomenon, observed in a variety of natural and artificial systems, in which coherent global structures or dynamics emerge from local interactions between individual parts. If the degree of collective integration of a system does not depend on size, its level of robustness and adaptivity is typically increased and we refer to it as scale-invariant. In this review, we first identify three main types of self-organized scale-invariant systems: scale-invariant spatial structures, scale-invariant topologies and scale-invariant dynamics. We then provide examples of scale invariance from different domains in science, describe their origins and main features and discuss potential challenges and approaches for designing and engineering artificial systems with scale-invariant properties

Diseño y Validación de las Componentes de un Proveedor de Servicios de Academia Virtual Económico y con Fines Docentes

Las actuales interfaces web de gestión de contenidos y del aprendizaje pueden ser favorecidas a través de nuevos componentes multimedia que son soportados por arquitecturas de software no propietario. De estos se destacan la transmisión de audio-video y la sincronización de presentaciones, los que permiten potenciar los sistemas de aprendizaje basados en web, hecho en que se fundamenta la importancia de la presente memoria. El objetivo general de este trabajo de título es mostrar alternativas de software no propietario que permitan llevar a cabo el diseño y la implementación de servicios basados en web. Estos últimos se utilizan en la academia virtual, la cual corresponde a una plataforma de apoyo a la docencia y de procesos formativos a distancia. Se utiliza una metodología que consiste en realizar una recopilación de los antecedentes de las tecnologías, como protocolos de comunicación, códecs, y las plataformas de desarrollo de software que permitan cumplir los objetivos planteados en este trabajo de título. Se definen los servicios que ha de tener la academia virtual, tomando en cuenta el ámbito económico y los fines docentes de este trabajo. Se procede al diseño de los componentes, subdividiéndolos de manera modular según sus funcionalidades. Se construyen ejemplos y se ponen a prueba, analizando el posible potencial y adaptabilidad a los objetivos propuestos en la memoria. Como resultado final se entrega una revisión de la tecnología Flash, del servidor de streaming RED5, de la plataforma de desarrollo Openlaszlo, y de herramientas de conversión de documentos por medio de ejemplos prácticos aplicados a la academia virtual. Además, se pone en funcionamiento el nuevo canal de comunicación desarrollado para Asterisk, software líder a nivel mundial en sistemas de telefonía open source, el cual permite la comunicación con Skype. Finalmente, se concluye que se han implementado de manera exitosa los componentes de la academia virtual, correspondientes a la transmisión de audio–video, la sincronización de presentaciones y la conversión de documentos. De esta forma se cumplen los objetivos propuestos, por utilizarse en su totalidad software no propietario. Asimismo, se entregan los lineamientos para futuros trabajos de título que puedan generar nuevas aplicaciones a los software usados dentro de esta memoria

Scale-Free Correlations in Flocking Systems with Position-Based Interactions

© 2014, Springer Science+Business Media New York. We consider a model of self-propelled agents with spring-like interactions that depend only on relative positions, and not on relative orientations. We observe that groups of these agents self-organize to achieve collective motion (CM) through a mechanism based on the cascading of self-propulsion energy towards lower elastic modes. By computing the correlation functions of the speed and velocity fluctuations for different group sizes, we show that the corresponding correlation lengths are proportional to the linear size of the group and have no intrinsic length scale. We argue that such scale-free correlations are a natural consequence of the position-based interactions and associated CM dynamics. We hypothesize that this effect, acting in the context of more complex realistic interactions, could be at the origin of the scale-free correlations measured experimentally in flocks of starlings, instead of the previously argued proximity to a critical regime.status: publishe

Scale-free correlations in collective motion with position-based interactions

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Modeling Phase Transition in Self-organized Mobile Robot Flocks

We implement a. self-organized flocking behavior in a group of mobile robots and analyze its transition front all aligned state to all unaligned state. We briefly describe the robot and the simulator platform together with the observed flocking dynamics. By experimenting with robotic and numerical systems, we find that an aligned-to-unaligned phase transition can be observed in both physical and simulated robots as the noise level is increased, and that this transition depends oil the characteristics of the heading sensors. We extend the Vectorial Network Model to approximate the robot dynamics and show that it displays all equivalent phase transition. By computing analytically the critical noise value and numerically the steady state solutions of this model, we Show that the model matches well the results obtained using detailed physics-based simulations

Explicit and Implicit Directional Information Transfer in Collective Motion

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Collective States, Multistability and Transitional Behavior in Schooling Fish

The spontaneous emergence of pattern formation is ubiquitous in nature, often arising as a collective phenomenon from interactions among a large number of individual constituents or sub-systems. Understanding, and controlling, collective behavior is dependent on determining the low-level dynamical principles from which spatial and temporal patterns emerge; a key question is whether different group-level patterns result from all components of a system responding to the same external factor, individual components changing behavior but in a distributed self-organized way, or whether multiple collective states co-exist for the same individual behaviors. Using schooling fish (golden shiners, in groups of 30 to 300 fish) as a model system, we demonstrate that collective motion can be effectively mapped onto a set of order parameters describing the macroscopic group structure, revealing the existence of at least three dynamically-stable collective states; swarm, milling and polarized groups. Swarms are characterized by slow individual motion and a relatively dense, disordered structure. Increasing swim speed is associated with a transition to one of two locally-ordered states, milling or highly-mobile polarized groups. The stability of the discrete collective behaviors exhibited by a group depends on the number of group members. Transitions between states are influenced by both external (boundary-driven) and internal (changing motion of group members) factors. Whereas transitions between locally-disordered and locally-ordered group states are speed dependent, analysis of local and global properties of groups suggests that, congruent with theory, milling and polarized states co-exist in a bistable regime with transitions largely driven by perturbations. Our study allows us to relate theoretical and empirical understanding of animal group behavior and emphasizes dynamic changes in the structure of such groups