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Park, Jinha. "Collective Motion in 3D and Hysteresis." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-156424.
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Many animal groups in nature exhibit collective motion, such as bird flocks and fish schools. The group's internal motion is complex and dynamic, but the group moves cohesively in the same direction. The mechanism behind this collective motion has been studied with various ways. Mathematical modeling provides powerful tools to study this. In particular, individual based, self-propelled particle (SPP) models are among the most popular. Several SPP models have been developed using different local interaction rules between each individual and its neighbours. Among them, the local attraction model is one of the simplest using only attraction as social force. This model is particularly interesting because it can produce a figure of eight pattern in two dimensional space. By studying the local attraction model, I investigate the hysteresis properties in simulated collective motions. I also extend the model to three dimensional space by including additional global attraction forces. In the three dimensional local attraction model, I find an analog of the figure of eight found in the two dimensional model as well as other types of internal dynamics. This present study demonstrates the importance of attraction as a social force and the usefulness of the local attraction model in describing collective motion both in two and three dimensions.
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Strömbom, Daniel. "Attraction Based Models of Collective Motion." Doctoral thesis, Uppsala universitet, Matematiska institutionen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205875.
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Animal groups often exhibit highly coordinated collective motion in a variety of situations. For example, bird flocks, schools of fish, a flock of sheep being herded by a dog and highly efficient traffic on an ant trail. Although these phenomena can be observed every day all over the world our knowledge of what rules the individual's in such groups use is very limited. Questions of this type has been studied using so called self-propelled particle (SPP) models, most of which assume that collective motion arises from individuals aligning with their neighbors. Here we introduce and analyze a SPP-model based on attraction alone. We find that it produces all the typical groups seen in alignment-based models and some novel ones. In particular, a group that exhibits collective motion coupled with non-trivial internal dynamics. Groups that have this property are rarely seen in SPP-models and we show that even when a repulsion term is added to the attraction only model such groups are still present. These findings suggest that an interplay between attraction and repulsion may be the main driving force in real flocks and that the alignment rule may be superfluous. We then proceed to model two different experiments using the SPP-model approach. The first is a shepherding algorithm constructed primarily to model experiments where a sheepdog is herding a flock of sheep. We find that in addition to modeling the specific experimental situation well the algorithm has some properties which may make it useful in more general shepherding situations. The second is a traffic model for leaf-cutting ants bridges. Based on earlier experiments a set of traffic rules for ants on a very narrow bridge had been suggested. We show that these are sufficient to produce the observed traffic dynamics on the narrow bridge. And that when extended to a wider bridge by replacing 'Stop' with 'Turn' the new rules are sufficient to produce several key characteristics of the dynamics on the wide bridge, in particular three-lane formation.
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Miller, Adam Morrison. "Simulating collective motion from particles to birds." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/80148/.
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The main work of this thesis is the construction of a 3D computer model of animal flocking based on vision. The model took an additional input, to those usually considered in tradition models: the projection of all other flock members on to an individual's field of view. Making 2D models is easy (in fact 4 new ones are included in this thesis), but we should be drawing parallels with experimental data for behaviour in animal systems and we should be cautious indeed when drawing conclusions, based on those models. It is common in the literature not to compare model behaviours with measurable quantities of natural flocks. However this work makes a concerted effort to do so in the case of the 3D model. A direct comparison was made in this work between the simulations and an empirical study of starling flocks, of the scaling behaviour of the maximum distance through the flock and the number of flock members, for which the agreement was very good. Other flock properties were compared with the natural flocks, but with less satisfactory results. A careful literature survey was made to investigate and ultimately support the biological plausibility of the 3D projection model. Biological and physiological plausibility is a factor not often considered by computational modellers. A series of novel and related 2D computer flocking models were investigated with hopes to find a single flocking rule that could manifest the most important features of collective motion and thereby be highly parsimonious. The final part of this thesis concerns a 2D computer model of photothermophoresis based on langevin dynamics, which it may be possible to use to find evidence of a density transition found in the continuum model. There was some evidence that a transition from a transparent diffuse state to an opaque compact one may exist for the discrete particle simulation.
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Jiang, Li. "Mechanisms and roles of information processing in collective motion." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30125.
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Le déplacement collectif est l'un des phénomènes les plus remarquables de la nature. Il a été observé pour de nombreuses espèces animales, comme les essaims de bactéries, l'agrégation des fourmis, les bancs de poissons, les nuées d'oiseaux ou encore les foules d'humains. Ces comportements collectifs d'animaux ne sont pas seulement des scènes spectaculaires mais sont aussi une source d'intérêt pour explorer les mécanismes sous-jacents dans le but de comprendre les lois et l'évolution des groups biologiques ou même de nous aider à élaborer des essaims auto-organisés de robots.Nous avons étudié différents systèmes de déplacements collectifs, incluant des systèmes avec une seule espèce, comme les bancs de poissons et les foules d'humains et d'autres à plusieurs espèces, comme les systèmes de fuite et poursuite en groupe. Parmi lesquels, nous nous concentrons sur les mécanismes et les rôles du traitement de l'information sur les motifs macroscopiques. De plus, pour palier à la difficulté d'extraire des trajectoires depuis des vidéos expérimentales de qualité médiocre, nous proposons un outil rapide et robuste de suivi du déplacement. Notre contenu de recherche détaillé est le suivant : 1. Nous avons étudié les mécanismes de traitement de l'information dans les déplacements du Nez-rouge dans un dispositive annulaire. Pour la première fois, nous avons définis un comportement particulier aux bancs de poissons : des évènements de demi-tour. En introduisant un délai entre l'interaction entre les poissons, nous avons trouvé qu'à un poisson d'intérêt correspondent seulement un ou deux poissons qui ne sont pas nécessairement les plus proches. De plus, nous avons montré que l'information de tourner pendant un évènement de demi-tour collectif se propage comme des dominos. Enfin, nous avons utilisé le transfert d'entropie pour quantifier les flux d'information dans l'espace et le temps durant les évènements de demi-tour. 2. Nous avons étudié le rôle d'une perturbation dans un système de foule humaine en plaçant des obstacles (les perturbations) dans un flux de fuite de panique. Nous avons trouvé une façon simple et efficace d'augmenter le flux de fuite dans le but de sauver plus de vies dans des situations dangereuses. Nous avons appliqué des algorithmes génétiques pour optimiser l'agencement des piliers dans les simulations puis nous avons testé la qualité de ces résultats contre des expériences avec de vrais humains. Les résultats suggèrent que placer deux piliers le long des deux côtés d'une sortie peut maximiser la vitesse de sortie. 3. Nous avons étudié le rôle des mécanismes de traitement de l'information dans les déplacements collectifs multi-espèces en introduisant différentes strategies pour les proies dans un modèle de poursuite en groupe. Nous proposons trois stratégies d'agrégation : se déplacer vers le centre de masse de toutes les proies (MC), se déplacer vers la proie la plus proche (NN) et minimiser la distance totale entre toutes les proies (MD). Les résultats montrent que l'agrégation augmente grandement la durée de survie du groupe, et ceci même en autorisant les proies à être immortelles. Il y a une transition de phase de t (la durée de survie moyenne) en fonction de M (le nombre de prédateurs). 4. Nous avons développé un nouvel outil de suivi de déplacement pour améliorer les algorithmes de reconnaissance d'image et de suivi actuels afin d'extraire des trajectoires depuis des vidéos de qualité médiocre. Notre outil intègre un filtre de moyenne glissante, la soustraction du bruit de fond, des réseaux de neurones artificiels, du partitionnement en k-moyennes et une fonction d'erreur définie minutieusement. L'outil peut extraire une trajectoire depuis une video de basse qualité qui ne peut être fait que très difficilement par d'autres outils. Il peut suivre plusieurs animaux comme des poissons, des drosophiles, des fourmis, etc. Les performances de notre outil sont meilleures que idTracker et CtraxCollective motion is one of the most striking phenomena in nature. It has been observed in a lot of animal species, such as bacteria, ants, fish, flocks of birds and crowds of human. These collective animal behaviors not only show us spectacular scenes, but also attract us to explore the underlying mechanisms in order to understand the laws and evolution of biological groups and even help us design smarter self-organizing robots. We study different collective motion systems including single species systems such as fish school and human crowd; and multi-species group chase and escape system. Among which, we focus on the mechanisms and roles of information processing on macro patterns. Moreover, regarding to the fact that it's very difficult to extract trajectory data from low quality experiment videos, we propose a fast and robust tracking tool. Details are as follows: 1. We study the mechanisms of information processing in the movements of Hemigrammus rhodostomus in a ring-shaped tank. For the first time, we define a special behavior of fish school: U-turn event. By introducing time delay between fish interaction, we find that a focal fish usually corresponds to only 1 or 2 fish which is not necessarily the nearest one. Moreover, we find the turning information during a group U-turn event propagates like domino. In addition, we use transfer entropy to quantify dynamic information flows in space and time across the U-turn events. 2. We study the role of perturbation information in human crowd system by introducing obstacles as perturbation information into a panic escaping flow. We find a useful and simple way to increase the panic flow in order to save more lives under dangerous situation. We apply genetic algorithms to optimize the layout of pillars in the simulations and then test the results with real human experiments. Results show that putting two pillars along the two sides of the exit can maximize the escape velocity. In the end, a tangential momentum theory is proposed to explain the role of the perturbation information. 3. We study the role of information processing mechanisms in multi-species collective motion by introducing different strateg?ies for the prey in a group chase model. We propose three aggregation strategies: moving to mass center of all preys, moving to the nearest prey and minimising the total distance to all preys. Results show that aggregation increase the group survival time greatly, even allowing immortal prey. There is a phase transition of t (average survival time) against M (number of predator). 4. We developed a new tracking tool to improve the current image recognizing and video tracking algorithms so as to extract trajectories from low quality videos. Our tool integrates mean-value filter, background substraction, artificial neural network, K-means clustering and a well defined cost function. It can track low quality videos which can be hardly tracked by other tools. And it can track different animals such as fish, drosophila, ants and so on. The overall tracking performance is better than idTracker and Ctrax
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Menezes, Debora Peres. "Boson mapping techniques and the nuclear collective motion." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329926.
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Janes, Jen. "The Texas chainsaw massacre: our collective nightmare." [Denver, Colo.] : Regis University, 2008. http://165.236.235.140/lib/JJanes2008.pdf.
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Zhou, Felix. "Phenotyping cellular motion." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:9fb6a57d-2e16-43c9-92e6-895330353e51.
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In the development of multicellular organisms, tissue development and homeostasis require coordinated cellular motion. For example, in conditions such as wound healing, immune and epithelial cells need to proliferate and migrate. Deregulation of key signalling pathways in pathological conditions causes alterations in cellular motion properties that are critical for disease development and progression, in cancer it leads to invasion and metastasis. Consequently there is strong interest in identifying factors, including drugs that affect the motion and interactions of cells in disease using experimental models suitable for high-content screening. There are two main modes of cell migration; individual and collective migration. Currently analysis tools for robust, sensitive and comprehensive motion characterisation in varying experimental conditions for large extended timelapse acquisitions that jointly considers both modes are limited. We have developed a systematic motion analysis framework, Motion Sensing Superpixels (MOSES) to quantitatively capture cellular motion in timelapse microscopy videos suitable for high-content screening. MOSES builds upon established computer vision approaches to deliver a minimal parameter, robust algorithm that can i) extract reliable phenomena-relevant motion metrics, ii) discover spatiotemporal salient motion patterns and iii) facilitate unbiased analysis with little prior knowledge through unique motion 'signatures'. The framework was validated by application to numerous datasets including YouTube videos, zebrafish immunosurveillance and Drosophila embryo development. We demonstrate two extended applications; the analysis of interactions between two epithelial populations in 2D culture using cell lines of the squamous and columnar epithelia from human normal esophagus, Barrett's esophagus and esophageal adenocarcinoma and the automatic monitoring of 3D organoid culture growth captured through label-free phase contrast microscopy. MOSES found unique boundary formation between squamous and columnar cells and could measure subtle changes in boundary formation due to external stimuli. MOSES automatically segments the motion and shape of multiple organoids even if present in the same field of view. Automated analysis of intestinal organoid branching following treatment agrees with independent RNA-seq results.
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Eriksson, Markus. "Spatial sorting and collective motion in mixed shoals of fish." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-266207.
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Shoaling behaviour arises when fish respond to the movements and positions of nearby neighbours. The dynamic patterns of shoaling fish has been studied by the Mathematical department in Uppsala University. In this project experimental data collected for groups with two sizes of fish are analysed. An existing model was modified to reproduce the dynamic patterns in the fish shoal, this was done by comparing visual and statistical properties from the simulations with experimental observations. By analysing the impact of the parameters in the model it was found out that introducing limitations in the vision of the smaller fish are essential to be able to reproduce the behaviour of the mixed sized fish shoal. The limitations in the vision are speculated to be a representation of physiological limitations in the coordination of mechano-sensoric activities and visual information.
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Oyama, Norihiro. "Direct Numerical Calculation on the Collective Motion of Model Microswimmers." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225640.
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Cohen, Joanna (Joanna Renee). "Models and simulations of collective motion in biomimetic robots and bacteria." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39872.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 119-124).
In nature, one finds many examples of collective motion, from flocking birds to swarming bees. Any one organism makes its decisions based solely on local information; either it can sense what its close neighbors are doing, or in the case of a single-celled organism, it can sense some local property of its environment. Yet complex global behaviors arise from these local interactions, and these large-scale patterns have neither a leader nor any other centralized control system. In this thesis, two specific cases of collective motion are studied: fish schooling and bacteria swimming across a surface. When fish swim in schools, they swim in the same direction as each other at approximately the same speed. Previous studies of fish have discovered three primary behaviors that, together, lead to large-scale coordination and schooling in the animals. This thesis demonstrates that the same algorithms can be applied to a group of identical underwater robots. If the robots need to coordinate with each other, they can use biomimetic control laws and adopt the interaction algorithms used by fish. A series of simulations are run to see what possible group behaviors can come from these control laws. At a smaller scale, prior experiments have revealed that bacteria and other small organisms also show collective motion.
(cont.) Unlike fish, bacteria cannot see their neighbors; the individual can only sense the bulk contribution of its neighbors to the flow at its location. The single-celled organisms are small and swim slowly, so they have very small Reynolds numbers. They are modeled in this work in a Stokes flow regime; the model is built bottom-up starting from the hydrodynamic field created by one organism and then superimposing these fields on top of each other. Different possible control policies are tested where each organism has an instantaneous desired direction based on some local property of the flow. While simulations of the current model do not yield results that fully emulate real bacteria, they have some similarities and provide insight into the complex hydrodynamic interactions between low Reynolds number swimmers.
Joanna Cohen.
S.M.
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Sepulveda, Nestor. "Physics models and analysis of collective behavior : supersolidity and cell motion." Paris 7, 2009. http://www.theses.fr/2009PA077254.
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Cette thèse comporte deux parties : l'une consacrée à l'étude de la supersolidité et l'autre à la modélisation d'une expérience sur le mouvement collectif de cellules. L'étude sur la supersolidité est faite dans le cadre de l'équation de Gross-Pitaevskii, en considérant un potentiel d'interaction entre particules non local. Ce choix, nous permet d'avoir un minimum de rotons dans la relation de dispersion responsable de la cristallisation. Avec ce modèle, nous calculons la fraction de superfluide comme fonction de l'intensité de l'interaction entre particule. Nous obtenons cette fraction de superfluide par deux méthodes : la première, en séparant le comportement rapide et lent des champs présents dans nos équations ; la deuxième, en calculant la dérivée par rapport à la vitesse de l'impulsion linéaire, lorsque le système est soumis à une vitesse donnée. Nous trouvons que les deux méthodes sont équivalentes pour une et deux dimensions d'espace. Pour deux dimensions d'espace, nous considérons également l'effet du désordre dans notrexv cristal". Nous trouvons que la présence du désordre produit une augmentation dans la fraction de superfluide, dépendant de la quantité du désordre. La deuxième partie de cette thèse porte sur l'étude et la modélisation d'une expérience de mouvement collectif de cellules sur un substrat plan. Il s'agit d'un modèle idéalisé d'une blessure. Pour décrire ce système, nous considérons un modèle de type Langevin, avec un terme de couplage entre les vitesses des particules, un terme d'interaction entre particules, décrit par un potentiel de répulsion à courte portée, et un bruit gaussian qui prend en compte tous les processus biochimiques responsables du mouvement des cellules. Avec ce modèle, nous sommes capables de reproduire différentes quantités statistiques calculées dans l'expérience. Ceci nous permet de conclure que ce modèle peut être un bon candidat pour expliquer le comportement des cellules dans cette expérience, et, nous l'espérons, dans d'autres situations biologiquesThis thesis is composed by two parts: one about the study of supersolid and the other one about modelling an experiment of collective cell motion. The study of supersolidity was done in the frame of the Gross-Pitaevskii equation, considering a non-local potential of interaction between particles. This choice, allows us to have a roton minima in the dispersion relation responsible for crystallization. With this model, we compute the superfluid fraction as function of the intensity of interaction between particles. We obtain this superfluid fraction by two methods: the first one, consists in separating the rapid and the slow behavior of the fields present in our equations; the second one, in Computing the derivative with respect to the velocity of the linear momentum, when the System is submitted to a given velocity. We find that both methods are equivalent to one and two spatial dimensions. For two dimensions of space, we consider equally the effects of disorder in our "crystal". We find that disorder increases the superfluid fraction, that depends on the quantity of disorder. The second part of this thesis is about the study and modeling of an experiment of collective cell motion on a flat substrate: an idealized model of a wound. To describe this System, we consider a Langevin-like model, with a coupling term between the velocity of the particles, an interaction term between particles, described by a short range repulsion potential, and a gaussian noise that describes all the biochemical process responsible for cellular motion. Whit this model, we are able to reproduce different statistical quantities computed in the experiment. That allows us to conclude that this model may be a good candidate to explain the cell behavior in this experiment, and, we hope, in other biological situations
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Hinohara, Nobuo. "Microscopic description of nuclear large-amplitude collective motion by means of the adiabatic self-consistent collective coordinate method." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136880.
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Lukeman, Ryan J. "Modeling collective motion in animal groups : from mathematical analysis to field data." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/11873.
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Animals moving together cohesively is a commonly observed phenomenon in biology, with bird flocks and fish schools as familiar examples. Mathematical models have been developed in order to understand the mechanisms that lead to such coordinated motion. The Lagrangian framework of modeling, wherein individuals within the group are modeled as point particles with position and velocity, permits construction of inter-individual interactions via `social forces' of attraction, repulsion and alignment. Although such models have been studied extensively via numerical simulation, analytical conclusions have been difficult to obtain, owing to the large size of the associated system of differential equations. In this thesis, I contribute to the modeling of collective motion in two ways. First, I develop a simplified model of motion and, by focusing on simple, regular solutions, am able to connect group properties to individual characteristics in a concrete manner via derivations of existence and stability conditions for a number of solution types. I show that existence of particular solutions depends on the attraction-repulsion function, while stability depends on the derivative of this function.
Second, to establish validity and motivate construction of specific models for collective motion, actual data is required. I describe work gathering and analyzing dynamic data on group motion of surf scoters, a type of diving duck. This data represents, to our knowledge, the largest animal group size (by almost an order of magnitude) for which the trajectory of each group member is reconstructed. By constructing spatial distributions of neighbour density and mean deviation, I show that frontal neighbour preference and angular deviation are important features in such groups. I show that the observed spatial distribution of neighbors can be obtained in a model incorporating a topological frontal interaction, and I find an optimal parameter set to match simulated data to empirical data.
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Hu, Yinmeng M. Eng Massachusetts Institute of Technology. "Investigation of viscosity effects on bacteria collective motion using particle image velocimetry." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111517.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 70-72).
Swimming bacteria are known to display collective motion resulting from their flagella propulsion. Various models of such collective behavior have been proposed, and different motion patterns are also well-documented. However, no previous research has investigated how contrasts in fluid viscosity would influence the collective motion of swimming bacteria. In this paper, Particle Image Velocimetry (PIV), a commonly-used method to measure nonintrusive, instantaneous and whole-field velocity, is applied to visualize the swimming patterns and behavior of Escherichia coli and Vibrio alginolyticus. Firstly, various PIV post-processing tools are examined; next, different PIV conditions are tested and post-processing methods are optimized to best visualize bacteria collective motion; finally, the influence of viscosity contrast on bacteria behavior is investigated, and the swimming patterns that result from injecting active suspensions of bacteria with fluids of different viscosity are investigated.
by Yinmeng Hu.
M. Eng.
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Bode, Nikolai W. F. "Modelling collective motion in animals and the impact of underlying social networks." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1609/.
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Nature is rich with examples of the collective motion of animal groups, such as flocks of birds or shoals of fish. The mechanisms of self-organization resulting in these spectacular phenomena have received wide attention. Individual-based models are a popular and promising approach to investigate and explain features of animal collective motion. The first part of this thesis gradually develops a novel modelling framework for the collective motion of animals and justifies it by comparison to empirical findings. Key aspects of the model are stochastic asynchronous updates and sensory zone sampling of individuals. Higher updating frequencies are related to increased levels of perceived threat and reduced stochastic effects leading to synchronisation in moving groups. Sensory zone sampling, biased according to the distance between individuals, provides a possible mechanism for the empirical finding that animals on average only interact with a fixed number of nearest neighbours. Many group-living animals show social preferences for relatives, familiar conspecifics or individuals of similar attributes, such as size. How such preferences could affect the collective motion of animal groups has been rather unexplored. The second part of this thesis reviews previous theoretical work that combines the concepts of social networks and collective motion. Although many of the models reviewed have not been explored with ecology in mind, they present a current context in which a biologically relevant theory can be developed. The modelling framework from the first part is extended to include social connections as preferential reactions between individuals. This is used to show that the structure of social networks could influence the cohesion of groups, the spatial position of individuals within groups and the hierarchical dynamics within such groups. This thesis aims to contribute possible mechanisms, testable hypotheses and an informed starting point for future research on how social networks could affect animal group movement.
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Beyer, Konrad [Verfasser], and Ulrich [Akademischer Betreuer] Schwarz. "Collective motion and adhesin dynamics of Plasmodium sporozoites / Konrad Beyer ; Betreuer: Ulrich Schwarz." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1178010422/34.
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Beyer, Konrad [Verfasser], and Ulrich S. [Akademischer Betreuer] Schwarz. "Collective motion and adhesin dynamics of Plasmodium sporozoites / Konrad Beyer ; Betreuer: Ulrich Schwarz." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:16-heidok-235610.
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Lee, Hye Rin Lindsay. "MATHEMATICAL STUDY OF HUMAN DYNAMICS WITH MODELING OF COLLECTIVE MOTION AND SOCIAL MEDIA." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1592359639613619.
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Stuart, Daniel Scott. "Implementation of Robot Arm Networks and Experimental Analysis of Consensus-Based Collective Motion." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/440.
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Within the field of multi-robot control, there is a large focus in research involving consensus. In this thesis two parts will be studied. The first development of this thesis is a consensus-based robot arm platform. To implement, two robotic arms are developed and studied. The most effective robot arm is then utilized to create a robot arm network testbed. Consensus is used to coordinate several robot arms and decentralize system computation. The research explores a platform to facilitate consensus on a group of robotic arms. The second development is in Cartesian coordinate collective motion. This collective motion control combines consensus through coupling of Cartesian coordinates. The controller is presented with simulation and experimental validation. Integration of both parts of the thesis is then discussed in application. An example is provided to demonstrate usefulness. In conclusion, this thesis provides more control to a system of ground robots using collective motion and consensus-based robot arms.
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Boczkowska, Ewelina. "Sites of remembrance music and memory in Polish film /." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1973844971&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Lecheval, Valentin. "Experimental analysis and modelling of the behavioural interactions underlying the coordination of collective motion and the propagation of information in fish schools." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30361/document.
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Les bancs de poissons sont des entités pouvant regrouper plusieurs milliers d'individus qui se déplacent de façon synchronisée, dans un environnement sujet à de multiples perturbations, qu'elles soient endogènes (e.g. le départ soudain d'un congénère) ou exogènes (e.g. l'attaque d'un prédateur). La coordination de ces bancs de poissons, décentralisée, n'est pas encore totalement comprise. Si les mécanismes sous-jacents aux interactions sociales proposés dans des travaux précédents reproduisent qualitativement les structures collectives observées dans la nature, la quantification de ces interactions et l'accord quantitatif entre ces mesures individuelles et les motifs collectifs sont encore rares dans les recherches récentes et forment l'objet principal de cette thèse. L'approche de ce travail repose sur une étroite combinaison entre les méthodes expérimentales et de modélisation dans l'objectif de découvrir les liens entre les comportements individuels et les structures observées à l'échelle collective. Nous avons caractérisé et quantifié les interactions et mécanismes à l'origine, d'abord, de la coordination des individus dans les bancs de poissons et, ensuite, de la propagation d'information, quand le groupe subit une perturbation endogène ou exogène. Ces travaux, tous réalisés en étudiant la même espèce de poisson d'eau douce, le nez-rouge (Hemigrammus rhodostomus), ont mobilisé une diversité de méthodes expérimentales, d'analyses statistique et de modélisation, à l'interface de l'éthologie, de la physique statistique et des sciences computationnellesFish schools are systems in which thousands of individuals can move in a synchronised manner in a changing environment, with endogenous perturbations (e.g. when a congener leaves the group) or exogenous (e.g. the attack of a predator). The coordination of fish schools, decentralised, is not completely understood yet. If the mechanisms underlying social interactions discussed in previous studies qualitatively match the social patterns observed in nature, the quantification of these interactions and the quantitative match between individual measurements and collective patterns are still sparse in recent works and are the main focus of this thesis. This work combines closely experimental and modelling methods in order to investigate the links between the individual behaviours and the patterns observed at the collective scale. We have characterised and quantified the interactions and mechanisms at the origin of, first, the coordination of individuals in fish schools and, second, the propagation of information, when the group is under endogenous or exogenous perturbations. This thesis focuses on one freshwater fish species, the rummy-nose tetra (Hemigrammus rhodostomus), and is the result of a diversity of experimental methods, statistical analyses and modelling, at the interface of ethology, statistical physics and computational sciences
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Aylward, Ryan P. "Sensemble : a wireless inertial sensor system for the interactive dance and collective motion analysis." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37391.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2006.Includes bibliographical references (p. 251-256).
The motivation for this project is the recent opportunity to leverage low-power, high-bandwidth RF devices and compact inertial sensors to create a wearable, wireless, motion analysis system meeting the demands of many points of measurement and high data rates. This thesis outlines the implementation of such a system intended for interactive dance, in which sensor nodes are worn on the wrists and ankles of dancers in an ensemble. Interactive dance is in some ways an ideal situation for pushing high performance requirements. Collecting data in a highly active environment of human motion demands a comfortable yet sturdy wearable design. Obtaining detailed information about the movement of the human body and the interaction of multiple human bodies demands many points of measurement and high resolution. Most importantly, using this information as a vehicle for interactive performance demands the real-time translation of data into an efficient feature set that a composer, designer, or choreographer can interpret. Now that it is possible to extend expressive motion sensing to multiple points on multiple dancers, an interactive system is capable of responding not only to individual motions, but also to how an ensemble is working together.
(cont.) The primary goal in this work is to demonstrate that simple features describing this type of collective activity can be extracted from the system and interpreted real-time, in order to generate responsive music or other immediate feedback. To this end, relevant strategies for feature extraction and music generation were implemented and tested, using data from a small dance ensemble. The results presented in this thesis show promising opportunities for future development in the areas of dance and interactive performance. In the broader scope, the hope is to expand this system to other applications, such as analyzing the dynamics of team sports, physical therapy, biomotion measurement and analysis, or personal physical training. Preliminary testing in these areas is also discussed.
by Ryan P. Aylward.
S.M.
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Croft, Simon. "Modelling collective motion and obstacle avoidance to assess avian collision risk with wind turbines." Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/11940/.
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Hazardous obstacles are a prominent feature of all natural environments and moving animals must demonstrate a robust avoidance response in order to prevent collisions. Whilst the study of collective motion has yielded many models for simulating animal movements, comparatively few have considered interactions with such obstacles. This thesis outlines a framework for incorporating obstacles into existing models of collective motion and uses these models to explore the impact of social interactions on collision risk. The findings presented show that in the case of obstacle avoidance, where navigational information can be contradictory, the collective decisions of homogeneous groups often results in increased collision risk due to contradictory information between individuals. The introduction of heterogeneous social networks, which gives preference to particular individuals, acts as a natural mechanism by which these conflicted decisions may be averted, thereby facilitating coherent avoidance manoeuvres. However, this comes at the cost of cohesion, and groups must balance staying together against the benefits of more effective decision making. The insights provided by models are applied to assess avian collision risk with wind turbines. This is an increasingly important ecological problem and has received wide attention. The difficulties in obtaining accurate empirical data at the individual level require that accurate and robust modelling solutions are developed. The models presented in this thesis provide a powerful tool in which collision risk can be assessed taking into account site- and species-specific factors. The key observation is that both social factors such as flock size, and spatial factors such as array design, significantly affect avoidance rates and consequently collision risk. Therefore the established methods of risk assessment, which assume a general avoidance rate and apply this to each individual independently, are argued to be inadequate.
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Rosén, Emil. "Analysis and visualization of collective motion in football : Analysis of youth football using GPS and visualization of professional football." Thesis, Uppsala universitet, Avdelningen för systemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-269457.
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Football is one of the biggest sports in the world. Professional teams track their player's positions using GPS (Global Positioning System). This report is divided into two parts, both focusing on applying collective motion to football. % The goal of the first part was to both see if a set of cheaper GPS units could be used to analyze the collective motion of a youth football team. 15 football players did two experiments and played three versus three football matches against each other while wearing a GPS. The first experiment measured the player's ability to control the ball while the second experiment measured how well they were able to move together as a team. Different measurements were measured from the match and Spearman correlations were calculated between measurements from the experiments and matches. Players which had good ball control also scored more goals in the match and received more passes. However, they also took the middle position in the field which naturally is a position which receives more passes. Players which were correlated during the team experiment were also correlated with team-members in the match. But, this correlation was weak and the experiment should be done again with more players. The GPS did not work well in the team experiment but have potential to work well in experiments done on a normal-sized football field. % The goal of the second part of the report was to visualize collective motion, more specifically leader-follower relations, in football which can be used as a basis for further research. This is done by plotting the player's positions at each time step to a user interface. Between each player, a double pointed arrow is drawn, where each side of the arrow has a separate color and arrow width. The maximum time lag between the between the two players is shown as the "pointiness" of the arrow while the color of the arrow show the maximum time lag correlation. The user can change the metrics the correlations are based of. As a compliment to the lagged correlation, a lag score is defined which tell the user how strong the lagged correlation is.
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Ferguson, Laura Elizabeth. "Kicking the Vietnam syndrome? : collective memory of the Vietnam War in fictional American cinema following the 1991 Gulf War." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2672/.
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This thesis analyses the concept of the “Vietnam Syndrome” and its continuing manifestation in fictional American films produced after the 1991 Gulf War, with reference to depictions of the Vietnam, Gulf and Iraq Wars. Based on contemporary press reports as source material and critical analysis, it identifies the “Vietnam Syndrome” as a flexible and altering national psychological issue characterised initially as a simple aversion to military engagement, but which grew to include collective feelings of shame, guilt and a desire to rewrite history. The thesis argues that the “Syndrome” was not quashed by the victory of the Gulf War in 1991, as had been speculated at the time. Rather, the thesis argues that it was only temporarily displaced and continues to be an ingrained feature of the collective American psyche in current times. The argument is based on theories of collective memory, according to which social attitudes are expressed in cultural products such as films. The relationships between memory and history, and between memory and national identity are explored as two highly relevant branches of collective memory research. The first of these combines the theories of Bodnar (1992), Sturken (1997), Winter and Sivan (1999) and Wertsch (2002), among others, to define memory’s relationship with history and position in the present. The discussion of the relationship between memory and national identity describes the process by which memory is adopted into the national collective, based on the research of Schudson (1992) and Hall (1999). Consideration is given to the alternative theories of Comolli and Narboni (1992 [1969]), Hobsbawm and Ranger (1983) and Miller (2005) that propose a unified representation from a dominant ideology and of The Popular Memory Group (1982) who argue a counter-hegemonic popular memory. The thesis argues that both are insufficient to account for public memory, establishing a multi-sourced collective memory as the basis for its arguments, as described by Hynes (1999) and Wertsch (2002). Successive chapters provide a close analysis of films in relation to the “Vietnam Syndrome”. Each of the films shows the different approaches to the conflicts and ways the “Vietnam Syndrome” manifests itself. Chapter 3 provides a summary of Vietnam War films released prior to the main period focused upon in this thesis, in order to contextualise the post-Gulf War texts. Chapter 4 analyses Heaven and Earth (1993, Dir. Oliver Stone) as a revolutionary depiction of the Vietnam War from a Vietnamese depiction. Chapter 5 discusses The War (1994, Dir. Jon Avnet) as a late revisionist text. The focus of Chapter 6 is Apocalypse Now Redux (2001, Dir. Francis Ford Coppola), a revision of a vision, in which the additional scenes are analysed for their contribution to this later, more reflective version of the 1970s text Apocalypse Now. The last Vietnam film analysed, We Were Soldiers (2002, Dir. Randall Wallace), is the subject of Chapter 7 and is discussed with reference to post-September 11 American society and the dormant period of the “Vietnam Syndrome.” Chapter 8 brings the previous Vietnam War film analysis chapters together to form intermediate conclusions prior to the progression to Gulf War films. Chapter 9 provides a break in the film analysis chapters to consider the press coverage of the Gulf War, compared to that of Vietnam, paving the way for the following discussion of Gulf War films. Press coverage of the Gulf War influences the visual depiction of the Gulf War in both Three Kings (1999, Dir. David O’Russell) in Chapter 10 and Jarhead (2005, Dir. Sam Mendes) in Chapter 11. The reading of Three Kings also analyses the narrative as a metaphor for American concerns over the American-led coalition’s conduct during the conflict, while Chapter 11 argues the use of Vietnam War films as media templates (Kitzinger, 2000) in Jarhead. Finally, Chapter 13 brings the film analysis to a close by discussing the early representations of the Iraq War that have emerged in recent years, including: American Soldiers: A Day in Iraq (2005, Dir. Sidney J. Furie), Home of The Brave (2006, Dir. Irwin Winkler), Stop-Loss (2008, Dir. Kimberley Peirce), Lions For Lambs (2007, Dir. Robert Redford) Redacted (2008, Dir. Brian de Palma) and The Hurt Locker (2008, Dir. Kathryn Bigelow). The main, but not exclusive, features typifying the “Vietnam Syndrome” expressed through the films include: a reluctance to engage in or support foreign military intervention; use of “good war” and “bad war” discourse; signs of a collective national trauma of defeat; expressions of guilt for the consequences of American actions and failings of policy; attempts to restore the national self-image. This thesis concludes that the “Vietnam Syndrome” is still relevant to American society and that it is expressed through films in a variety of ways. It argues that the Vietnam War and the “Vietnam Syndrome” have become frames of reference for the discussion and representation of conflict and that the American collective psyche suffers a mixture of syndromes, some mutually enforcing and some contradictory, that are triggered by a variety of circumstances. The “Vietnam Syndrome” is identified as the most prolific of these and through its construction and circulation in media products, including cinema, this thesis argues it has become an umbrella term for the remnants of angst over Vietnam and new concerns over other conflicts.
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Bregulla, Andreas Paul. "Role of thermo-osmotic flows at low Reynolds numbers for particle driving and collective motion." Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-206615.
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The main subject of this thesis is to examine thermo-osmotic flows, which occur on interfaces of non-uniform temperature. Such thermo-osmotic flows are purely non-thermal equilibrium phenomena. Along the non-isothermal interface, specific interaction of a liquid and its solutes with a boundary vary in strength across the interface, according to the local temperature. This boundary can be a solid, a membrane or a phase boundary. The flow is thereby continuously pumping fluid across the interface in direction of the local temperature gradient, resulting in an extended flow pattern in the bulk due to mass conservation. In a system containing particles and heat sources in a liquid under spatial confinement, the thermo-osmotic flow may drive particles in a directed manner, or can lead to collective phenomena. To approach this broad topic of (self-)thermophoresis and collective motion of active particles and quantify the role of the thermo-osmotic flow upon the latter effects, different experiments have been performed:
The first experiments aim to quantify the thermo-osmotic flow at a non-isothermal liquid/solid interface for two fundamentally different substrate properties. Further, the bulk flow was investigated for two different systems. The form and spatial extension of this bulk flow pattern depends sensitively on the form of the container and the interface, as well as on the thermo-osmotic flow. The first system is a liquid film confined between two planar glass cover slips. The second case is a Janus particle immobilized on one of the glass slips. In the first case, the non-uniform temperature profile is generated by optical heating of a nanometer sized gold colloid, and in the second case, the heat source is the Janus particle. The bulk flow pattern consists, for the second case, of the flow pattern created by the glass cover slips and the one created by the Janus particle.
The following experiments are focusing on the dynamics of mobile self-thermophoretic Janus particles. In particular, their dynamics and the contributions of the thermo-osmotic flow to the interaction of multiple active particles are investigated. To investigate those particles under controlled conditions and examine their interactions at low concentrations for an effectively unlimited amount of time, a real-time feedback algorithm was co-developed to gain control of the motion of multiple active particles simultaneously, called ”photon nudging”. With the help of this method, first experiments have been performed to quantify the dynamics of a Janus particle located close to a heat source.
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Geyer, Delphine. "Du mouvement au blocage collectif dans des assemblées de rouleurs colloïdaux : hydrodynamique et solidification des liquides polaires actifs." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN026/document.
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Des mouvements collectifs dirigés émergent dans des systèmes très variés, depuis les assemblées synthétiques de grains vibrés jusqu'aux nuées d'oiseaux dans la nature. En essayant de comprendre le caractère générique de ces comportements dynamiques collectifs, les physiciens ont décrit les populations d'individus motiles comme des matériaux ordonnés.Dans cette thèse, nous réalisons expérimentalement des troupeaux synthétiques en laboratoire et nous explorons leurs propriétés hydrodynamiques.Nous tirons avantage du mécanisme d’électro rotation de Quincke pour motoriser des millions de colloïdes. Ces rouleurs de Quincke sont capables de s'auto-organiser pour former un troupeau appelé liquide polaire où toutes les particules se déplacent en moyenne dans la même direction.Nous montrons que la dynamique de ce liquide polaire est très bien décrite par des prédictions théoriques laissées sans preuves expérimentales depuis vingt-cinq ans. En particulier,nous démontrons que deux modes sonores s'y propagent et nous montrons que l’étude de leur spectre fournit une méthode non invasive pour mesurer ses constantes hydrodynamiques.Finalement, nous montrons que le mouvement dirigé peut être supprimé collectivement dans un troupeau dense. Un solide actif peut nucléer et se propager à contre-courant dans le liquide polaire. Nous établissons que cette solidification est une transition du premier ordre et qu'il s'agit de la première démonstration expérimentale complète d'une séparation de phase induite par la motilité des particules actives (aussi appelée MIPS)Spontaneous collective motion arises in many different systems, from assembly of synthetic shaken grains to living bird flocks. In order to understand the generic features of those collective behaviours, physisicts describe the flocks of motile units as ordered materials. In this thesis we study experimentally the dynamics of synthetic flocks and explore their hydrodynamic properties. We take advantage of the Quincke mechanism to motorize millions of colloids. Those Quincke rollers self-organize into a polar liquid, where all the particles, on average flow in the same direction. We provide the first experimental proof that the dynamics of polar liquids is well described by a theoretical prediction established more than twenty-five years ago. In particular, we demonstrate that two sound modes propagate along all directions of the fluid and we design a non invasive spectroscopic method to measure its hydrodynamics constants.Finally, we show that collective motion can be arrested in a dense flock. An active solid can nucleate, grow and propagate in a polar liquid. We establish that this solidification is a first order phase transition and demonstrate that the formation of this active solid is the first experimental proof of a complete motility induced phase separation of active particles (also known as MIPS)
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Toulet, Sylvain. "Déplacements collectifs auto-organisés : décision individuelle et transfert d'information." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30172/document.
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Les déplacements collectifs se manifestent souvent de façon spectaculaire et intriguent tant les amateurs de la nature que les chercheurs. Comment émergent ces formes spectaculaires et comment la cohésion des groupes est elle assurée ? Si de nombreux travaux ont été consacrés à l'identification des règles permettant la cohésion dans les groupes en mouvement, plus rares sont ceux consacrés aux transitions entre les états d'arrêt et de déplacement. Cette thèse traite des mécanismes comportementaux impliqués dans les prises de décisions collectives et la dynamique de transition de tels évènements chez le mouton Merinos (Ovis aries). Nous proposons de nouvelles hypothèses sur la modulation des interactions entre individus par des effets spatiaux dans des groupes de grande taille. Nous proposons un modèle spatio-temporel reproduisant nos résultats expérimentaux sur les départs, les déplacements collectifs et les arrêts de groupes de taille croissante et permettant d'explorer les décisions collectives dans des conditions nouvelles. Les résultats expérimentaux et théoriques per- mettent d'améliorer la compréhension des mécanismes individuels à l'origine des décision collectives permettant de maintenir ou non la cohésion des groupesCollective movements often involve very spectacular displays that fascinate nature lovers and researchers. How do such amazing patterns appear and how group cohesion can be maintained ? If many studies were carried out to decipher the rules underlying cohesion for groups in movement, there is a lack of works adressing the transitions involved in collective movements : departures and stops. This thesis adresses the behavioural mechanisms involved in the collective decision-making processes oc- curing in such transitions in Merino sheep (Ovis aries) groups. We propose some new kinds of spatial hypotheses that can account for the way interactions between individuals are locally modulated in large groups where individuals cannot have an access to the global information of all individuals. We developed a novel spatiotemporal model of sheep collective motion that reproduces the experimental observations and allows to explore the outcomes of collective decisions in various conditions. The experimental and theoretical results increase the understanding of the individual mechanisms that produce collective decisions allowing to maintain group cohesion
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Thüroff, Florian Peter [Verfasser], and Erwin [Akademischer Betreuer] Frey. "Collective motion in active matter : from microscopic models to macroscopic dynamics / Florian Peter Thüroff. Betreuer: Erwin Frey." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1080122400/34.
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Hämmerling, Jens [Verfasser], Thomas [Akademischer Betreuer] Guhr, and Klaus [Akademischer Betreuer] Hornberger. "Collective Motion in Quantum Many-Body Systems / Jens Hämmerling. Gutachter: Klaus Hornberger ; Thomas Guhr. Betreuer: Thomas Guhr." Duisburg, 2011. http://d-nb.info/1016172656/34.
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Vazquez-Rodríguez, Ana-Maria. "Conflicted societies in motion: A study of individual and collective responses to drug-related violence in Mexico." Thesis, Boston College, 2018. http://hdl.handle.net/2345/bc-ir:108053.
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Thesis advisor: Margaret LombeThesis advisor: Alfonso Hernandez
Drug-related violence in Mexico has grown into a profound social problem, aggravating existing insecurity, vulnerability, and citizen’s wellbeing. In critical scenarios of this kind, the virtues of social engagement for enhanced wellbeing, improved security and true democracy appear futile. This research examines how resources and incentives for mobilization operate. Specifically, social capital and political culture are studied as mechanisms that may affect those relationships. This research draws upon theories of Collective Action and Social Capital Theory. Also used are studies on the influence of emotions and perceptions on citizen’s collective mobilization. This approach contributes by accounting for informal participation and their various political loadings in conflict environments. To achieve the objective, Regression Analysis and Structural Equation Modelling were conducted. The study uses secondary data collected in 2011 (N = 7,416) using a probabilistic sample design representative of seven Mexican states selected by their levels of violence. Two subsamples were constructed to examine the varying effects of social and political resources on mobilization across regions (north and south). Results show the emotional component associated with citizen’s mobilization for collective action. The findings also exhibit social capital and political culture as key indicators of people’s decision to organize for social change. Finally, intriguing results related to the “negative form” of social capital were observed. To be precise, social capital appears to be insufficient to explain citizens' motives to mobilize with others for social change. Implications for policy and scholarship are presented. Specifically, initiatives regarding the importance of the effects of the weakened democratic environment, social lack of trust, government unresponsiveness and impunity, and self-directed processes of justice at the community level are highlighted
Thesis (PhD) — Boston College, 2018
Submitted to: Boston College. Graduate School of Social Work
Discipline: Social Work
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Ginot, Félix. "Dynamical aspects of active colloids : from dilute to dense systems." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1213/document.
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Les effets collectifs sont présents dans la nature à de nombreuses échelles et dans des systèmes très différents.On peut notamment citer les vols d'oiseaux, les bancs de poissons, les nuages d'insectes, ou encore les troupeaux de moutons.Pour pouvoir décrire ces effets collectifs, il est nécessaire de disposer de systèmes expérimentaux abiotiques modèles.Dans cette thèse nous présentons un système expérimental composé de colloïdes Janus or et platine. Au contact d'eau oxygénée ces colloïdes se mettent en mouvement tout en consommant ce carburant.Ce système est donc fondamentalement hors équilibre puisque de l'énergie est consommée à l'échelle des individus. Il a la particularité de présenter des effets collectifs sous la forme de l'apparition de clusters, agrégats dynamiques de colloïdesCollective motion are present at every scales and in very various biological systems. For example one can observe flocks of birds, schools of fishes, or swarms of insects. To be able to describe and understand these collective effects, it is necessary to have experimental abiotic model systems.In this PhD we present an experimental system made of Janus colloids of gold and platinum. When putted in an hydrogen peroxide bath, they set in motion, consuming fuel.This system is fully out of equilibirum because energy is consumed at the scale of individuals. It presents collective motion with the apparition of clusters, dynamical aggregates of active colloids.This PhD is structured around three parts :- the study of the kinetics and dynamics of the clusters- the achievement of sedimentation experiments- the study of the system in dense assemblies, forming an active colloidal glass
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Merrifield, Alistair James. "An Investigation Of Mathematical Models For Animal Group Movement, Using Classical And Statistical Approaches." Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/1132.
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Collective actions of large animal groups result in elaborate behaviour, whose nature can be breathtaking in their complexity. Social organisation is the key to the origin of this behaviour and the mechanisms by which this organisation occurs are of particular interest. In this thesis, these mechanisms of social interactions and their consequences for group-level behaviour are explored. Social interactions amongst individuals are based on simple rules of attraction, alignment and orientation amongst neighbouring individuals. As part of this study, we will be interested in data that takes the form of a set of directions in space. In Chapter 2, we discuss relevant statistical measure and theory which will allow us to analyse directional data. These statistical tools will be employed on the results of the simulations of the mathematical models formulated in the course of the thesis. The first mathematical model for collective group behaviour is a Lagrangian self-organising model, which is formulated in Chapter 3. This model is based on basic social interactions between group members. Resulting collective behaviours and other related issues are examined during this chapter. Once we have an understanding of the model in Chapter 3, we use this model in Chapter 4 to investigate the idea of guidance of large groups by a select number of individuals. These individuals are privy to information regarding the location of a specific goal. This is used to explore a mechanism proposed for honeybee (Apis mellifera) swarm migrations. The spherical theory introduced in Chapter 2 will prove to be particularly useful in analysing the results of the modelling. In Chapter 5, we introduce a second mathematical model for aggregative behaviour. The model uses ideas from electromagnetic forces and particle physics, reinterpreting them in the context of social forces. While attraction and repulsion terms have been included in similar models in past literature, we introduce an orientation force to our model and show the requirement of a dissipative force to prevent individuals from escaping from the confines of the group.
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Merrifield, Alistair James. "An Investigation Of Mathematical Models For Animal Group Movement, Using Classical And Statistical Approaches." University of Sydney, 2006. http://hdl.handle.net/2123/1132.
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Doctor of PhilosophyCollective actions of large animal groups result in elaborate behaviour, whose nature can be breathtaking in their complexity. Social organisation is the key to the origin of this behaviour and the mechanisms by which this organisation occurs are of particular interest. In this thesis, these mechanisms of social interactions and their consequences for group-level behaviour are explored. Social interactions amongst individuals are based on simple rules of attraction, alignment and orientation amongst neighbouring individuals. As part of this study, we will be interested in data that takes the form of a set of directions in space. In Chapter 2, we discuss relevant statistical measure and theory which will allow us to analyse directional data. These statistical tools will be employed on the results of the simulations of the mathematical models formulated in the course of the thesis. The first mathematical model for collective group behaviour is a Lagrangian self-organising model, which is formulated in Chapter 3. This model is based on basic social interactions between group members. Resulting collective behaviours and other related issues are examined during this chapter. Once we have an understanding of the model in Chapter 3, we use this model in Chapter 4 to investigate the idea of guidance of large groups by a select number of individuals. These individuals are privy to information regarding the location of a specific goal. This is used to explore a mechanism proposed for honeybee (Apis mellifera) swarm migrations. The spherical theory introduced in Chapter 2 will prove to be particularly useful in analysing the results of the modelling. In Chapter 5, we introduce a second mathematical model for aggregative behaviour. The model uses ideas from electromagnetic forces and particle physics, reinterpreting them in the context of social forces. While attraction and repulsion terms have been included in similar models in past literature, we introduce an orientation force to our model and show the requirement of a dissipative force to prevent individuals from escaping from the confines of the group.
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Jin, Di. "Cell-cycle dependent motility of Chlamydomonas reinhardtii and its collective motion in response to a Hagen-Poiseuille flow." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/284912.
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Motility of unicellular algal cells, especially its ability to respond to environmental cues, is crucial in industrial and ecological contexts and has been studied extensively with the model organism Chlamydomonas. However, little is known about the relationship between motility and the cell-cycle, despite the apparent link of mitosis dependent morphological changes which involve the flagella and the dependency on light/dark conditions of the cellular reactions. In this study, the cell swimming speed, the rotational diffusivity and its swimming bias against gravity were measured with high-speed video microscopy with Chlamydomonas reinhardtii cultures highly synchronised to a diurnal cycle. A simulation of gravitactic cell trajectories was developed to assist the statistical analysis of the cell trajectories from the images, which subject to a projection effect and has not been addressed previously. Its morphological changes, including cell size, shape, mass density, and presence of flagella were also evaluated. Un unforeseen change of cell motility at a critical mitosis time point was discovered, and our analysis suggests a connection to the alternating cell energetic regimes rather than the cell morphology. As indicated by results obtained from imaging based experimental measurements and by computational methods, the motility variation has direct consequences on the collective motion of algal cells in a Hagen-Poiseuille flow, a relevant component flow for air-lift photobioreactors. The cell number density profiles were calculated by an individual-based simulation and a continuum system inclusive of the buoyancy effect imposed by the aggregated cells on their surrounding fluid. Qualitative experimental-theoretical agreement suggests that the models can be employed for optimisation problems of photobioreactor flow designs inclusive of the non-negligible cell-cycle effects, which has been commonly overlooked in previous studies.
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Segerer, Felix J. Verfasser], and Joachim [Akademischer Betreuer] [Rädler. "From single-cell migration to the emergence of collective motion using microstructured surfaces / Felix Jakob Segerer. Betreuer: Joachim Rädler." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1111505314/34.
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Garcia, Simon. "Maturation et mise en compétition de monocouches cellulaires." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066438/document.
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Les mouvements cellulaires collectifs jouent un rôle fondamental dans de nombreux phénomènes biologiques (développement, régénération, cancer, etc.). Pour autant, les mécanismes régissant ces mouvements sont toujours mal connus. Nous nous proposons dans cette thèse d'étudier deux situations expérimentales mettant en jeu ces mouvements dans des monocouches cellulaires.Nous nous intéressons en premier lieu à des cellules HBEC, épithéliales mais peu cohésives. On calcule par PIV (vélocimétrie par images de particules) le champ de vitesse dans des populations de cellules déposées de manière homogène sur le substrat. On observe un ralentissement des mouvements et une progression non monotone de leur corrélation spatiale en fonction du temps. La combinaison de nos expériences, d'un modèle analytique et de simulations nous permet de conclure que cette évolution est la signature d'une transition de jamming contrôlée par la vitesse et que le ralentissement est dû à une maturation des jonctions cellule-cellule et des adhésions cellules-substrat.Nous étudions ensuite la compétition pour l'espace entre deux lignées HEK-HT, l'une normale et l'autre transformée par une mutation oncogénique RasV12. On dépose face à face les deux populations, porteuses d'un fluorophore différent, séparées par une bande de substrat libre pour les faire migrer l'une vers l'autre. On combine l’analyse des images de fluorescence aux techniques de PIV pour étudier la dynamique des deux fronts de population. Après contact et malgré un certain mélange des deux types, les monocouches forment une interface relativement bien définie qui se déplace dans le sens d'avancée du type transforméCollective cellular motion plays a fundamental role in several biological phenomena: development, regeneration, cancer, etc. However, the mechanisms behind this motion are still poorly understood. In this thesis, we study two experimental situations involving collective motion in cellular monolayers.We first look at HBEC cells, which are epithelial but weakly cohesive. Using particle image velocimetry (PIV), we monitor the velocity field in populations of cells homogeneously seeded on the susbtrate. We observe a slowdown in the cellular motion as its spatial correlation non-monotonically changes with time. Combining our experiments with an analytical model and simulations allows us to conclude that the system undergoes a jamming transition with speed as the main control parameter. We also show that the observed slowdown is a consequence of the maturation of cell-cell junctions and cell-substrate adhesions.We then study the competition for space between two HEK-HT cell lines, one being normal and the other being transformed by an oncogenic RasV12 mutation. The two fluorescently-labeled populations are set to migrate antagonistically towards an in-between stripe of free substrate. Through analysis of the fluorescence images and PIV methods, we study the dynamics of both population fronts. After contact, even though the two types mix to a certain extent, we observe a relatively well-defined interface, which moves towards the normal population
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Kumar, Priya Haryant. "Ruptured nations, collective memory & religious violence : mapping a secularist ethics in post-partition South Asian literature and film." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37904.
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This dissertation maps the emergence of a 'secularist ethics' in post-independence South Asian literature and film, an ethics which is a deeply felt poetic response to particular historical conjunctures marked by religio-nationalist conflict in the Indian subcontinent. It is my argument that literary and cultural productions, in striving to dream and envision a world free of violence, terror and religious intolerance, have some central contributions to make to contemporary intellectual and political debates on secularism. Through close readings of fictions by Salman Rushdie, Amitav Ghosh, Mukul Kesavan, Bapsi Sidhwa, Saadat Hasan Manto, Khwaja Ahmad Abbas, Rajinder Singh Bedi, Jamila Hashmi, Jyotirmoyee Devi, and Lalithambika Antherjanam, as well as films by M. S. Sathyu, Saeed Akhtar Mirza, Khalid Mohamed and Shyam Benegal, which are concerned to address the issue of peaceful co-existence between different religious communities and nations in the Indian subcontinent, I argue that literary and imaginative endeavors by way of their alternative secularist imaginaries enable us to begin to imagine the possibilities of more habitable futures. Significantly, the 'secularist' fictions and films I invite attention to in my project enable a revisioning of the secular in terms quite different from normative understandings of liberal secularism. Such a renewed secularism seeks to make visible the normalization and neutralization of majoritarian religious beliefs and practices as constitutive of the representative secular-nationalist self in post-Partition India; it also emerges, significantly, from a gendered critique of the deep-seated patriarchal norms underlying most religious communities. Responding to different moments of crisis, predominantly the Partition of India in 1947, the 1984 anti-Sikh riots, and the destruction of the Babri Masjid in 1992, the radical secularist poetics of these works call attention to the fundamentalist agenda of Hindu nationalism, the limit
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Delmotte, Blaise. "Modeling and Simulation of Individual and Collective Swimming Mechanisms in Active Suspensions." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14354/1/delmotte_partie_1_sur_2_2.pdf.
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We have all witnessed the flocking of starlings in the sky and the schools of fish that form in the ocean. This kind of organization of living creatures is not limited to those that we see, but also occurs for those that we don’t : swimming microorganisms. Suspen- sions of micro-swimmers exhibit a rich dynamics. Their behaviors can play an important role in the survival of the group, its development, the balance between species, their trophic strategies and even animal fertility. They can form coherent structures due to collective motion, mix the surrounding fluid or modify its rheological properties. Such diversity results from the complex interplay between swimming strategies, physiological processes, chemical reactions and hydrodynamic interactions. Fluid Mechanics is there- fore essential to understand and master the mechanisms involved in these phenomena. While experimental studies bring out new findings and, sometimes, provide physical ex- planations, modeling remains essential. Yet, including an accurate description of the micro-swimmers in a suspension containing thousands (nay millions) individuals, requires considering a wide range of coupled scales (from one micron 10^−6m to several millimeters 10^−3m). What happens on large scales depends on sophisticated mechanisms occurring two or three orders of magnitude below. Therefore, the multiscale modeling of such phenomena is still a major challenge for the state-of-the-art numerical methods. This thesis aims at providing a contribution in that direction. In a first part, we will show that reproducing swimming mechanisms at the scale of the micro-swimmer can be achieved with various models spanning different levels of complexity. We will then present our developments to incorporate these models in an efficient framework for large scale simulations. We will show how to simultaneously account for the Brownian motion of the smallest particles (10^−6m). Our code reproduces known results from the literature with the same accuracy, but at lower cost and at larger scales, thus bridging a gap between particle-based models, experiments and continuum formulations from kinetic theory. Using the capabilities afforded by our method, we eventually address two open problems in the experimental literature : the origins of orientational correla- tions between interacting self-propelled micro-droplets and the mechanisms at play in the nonlinear enhancement of Brownian particle diffusion in active suspensions.
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Locatelli, Emanuele. "Dynamical and collective properties of active and passive particles in Single File." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423763.
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Particles motion inside complex, irregular or crowded environments is a common phenomenon ranging from microscopic to macroscopic scales. It can be involved in everyday practical problems, like traffic, in fundamental biological mechanisms, like growth and reproduction of cells, and in important industrial or chemical applications, like oil catalysis. In many cases, transport in crowded environments is guided by 'active' elements, i.e. units that consume energy in order to produce motion. Among systems belonging in this class, the diffusion of hard-core particles in a channel so narrow they cannot pass each other, known as Single File Diffusion, has assumed a particular role. Single File Diffusion is responsible for the transport of ions in membrane channels, the diffusion in nano- and micro-porous materials and has been observed in many other natural and artificial systems.
Aim of this thesis is to investigate Single File system of passive (purely diffusive) or active (self propelled) particles, focusing on the effects of the activity on the Single File motion and on the Single File properties in the presence of absorbing boundaries. Most of the work has been carried out developing analytical and numerical tools within the framework of the Stochastic Processes. By using single particle techniques in a microfluidic approach, we obtained an excellent comparison between experimental data and numerical model of particles emptying a Single File channel with open ends.
In this thesis, after a brief introduction in the framework of confined diffusion processes, we will review the most relevant works in the theoretical and experimental literature of Single File Diffusion, with particular attention to an analytical technique, the Reflection Principle Method, which will be extensively used in this thesis. We will investigate the properties of Single File systems of diffusing particles in presence of two absorbing boundaries, with particular interest to the survival probability, i.e. the probability to find a particle between the boundaries at time t. We will provide an analytical solution of the emptying process, i.e. we calculate the probability characterizing the progressive decrease of the number of particles in the presence of absorbing boundaries, and for the survival probability of a Tagged Particle within the file, either in the presence or in the absence of a constant external force. We also characterize the trend of the characteristic survival times (also called Mean First Passage Times) as function of the system size and of the initial number of particles. We also investigate numerically the case when only the central particle is affected by the absorbing boundaries. We find an exponential decay of the survival probability, as it happens for normal diffusive processes, even in the presence of overcrowding. We will then introduce activity in a Single File system, through a Self-Propelled Particle model, for which we will provide a detailed characterization. In particular, within this model, particles can be either runners or tumblers, if their motion is dominated by straight runs or by changes of direction, respectively. Under Single File conditions, runners tend to form dynamical aggregates: these clusters are continuously formed and disassembled due to random fluctuations of the activity. For tumblers, the survival probabilities are still well described by the analytical theory developed for passive diffusing particles. Conversely, the formation of dynamical clusters enhances anomalous behaviours in the characteristic survival times of runners and induces a remarkable capacity to overcome the action of an external force.Il moto di particelle in mezzi irregolari, complessi o affollati è un fenomeno comune, dalla scala microscopica a quella macroscopica. Lo si può incontrare tanto in situazioni comuni, come il traffico, quanto in meccanismi biologici, come la riproduzione e la crescita delle cellule, e in importanti processi chimici e tecnologici, come la catalisi di idrocarburi. In molti casi, il trasporto in mezzi confinati o affollati è guidato da elementi 'attivi', cioè unità che consumano energia per sostenere il loro stato di moto. Fra i diversi sistemi soggetti a confinamento, particolare rilevanza è rivestita dalla diffusione di sfere impenetrabili in un canale così stretto da non permettere il passaggio di più di una particella alla volta, conosciuto come diffusione in Single File. La diffusione in Single File è il meccanismo responsabile del trasporto di ioni attraverso la membrana cellulare, della diffusione in materiali micro e nanoporosi ed è stata osservata in molti altri sistemi naturali ed artificiali. Scopo di questa tesi è lo studio su scala mesoscopica di particelle passive (diffusive) o attive (auto-propellenti) in condizioni di Single File, con particolare attenzione all'effetto dell'attività sulla dinamica e sulle proprietà delle particelle nel caso siano presenti condizioni al contorno assorbenti. Gran parte del lavoro è stato svolto nello sviluppo di risultati analitici e numerici nel contesto dei Processi Stocastici. Inoltre, mediante tecniche di manipolazione ottica di singola particella in canali microfluidici, abbiamo ottenuto una eccellente confronto fra dati sperimentali e numerici per il processo di svuotamento di un sistema di particelle in condizioni di Single File. In questa tesi, dopo una breve introduzione ai processi diffusivi fortemente confinati, passeremo in rassegna i lavori più rilevanti della letteratura teorica e sperimentale sulla Single File Diffusion, con particolare attenzione ad un formalismo matematico, il Reflection Principle Method, che sarà applicato in maniera estensiva nel corso della tesi. Studieremo poi le proprietà di un sistema di particelle diffusive in Single File in presenza di condizioni al contorno assorbenti, concentrandoci sulla survival probability, cioè la probabilità di trovare una particella fra gli estremi del sistema al tempo t. Mostreremo come, in condizioni di Single File, abbiamo ottenuto una soluzione analitica per il processo di svuotamento, cioè calcoleremo la probabilità che caratterizza la progressiva diminuzione del numero di particelle in presenza di condizioni al contorno assorbenti, e per la survival probability di una particella 'marcata' all'interno della Single File sia in presenza che in assenza di una forza esterna costante. Caratterizzeremo gli andamenti dei tempi caratteristici di sopravvivenza, chiamati Tempi Medi di Primo Passaggio, in funzione della taglia del canale e del numero iniziale di particelle. Indagheremo inoltre numericamente il caso in cui solo la particella centrale del sistema in Single File subisce l'effetto delle condizioni al contorno assorbenti. Osserviamo un decadimento esponenziale della survival probability, come accade nell'usuale moto Browniano, anche in presenza di estremo confinamento. Introdurremo l'attività nella Single File attraverso un modello di particelle Self-Propelled, di cui descriveremo le proprietà in dettaglio. In particolare in questo modello le particelle possono essere o runners o tumblers, a seconda che la loro traiettoria sia dominata da lunghi tratti rettilinei o da cambi di direzione. In condizioni di Single File, i runners tendono a formare aggregati dinamici: questi cluster vengono continuamente formati e distrutti dalle fluttuazioni casuali della forza propulsiva. Per i tumblers, le probabilità di sopravvivenza sono ben descritte dalla teoria analitica sviluppata per le particelle passive. Per contro, la formazione di cluster dinamici accresce i comportamenti anomali nei tempi caratteristici di sopravvivenza dei runners e ne induce una notevole capacità di opporsi all'azione di un campo esterno.
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Jory, Myriam. "Approche biophysique de la fonction muco-ciliaire de l'épithélium bronchique : propriétés d'écoulement du mucus et coordination du battement ciliaire." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS078.
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Comprendre et soigner les pathologies respiratoires chroniques constituent des enjeux médicaux croissants du fait des modifications de nos modes de vie et de notre environnement. L’épithélium des voies respiratoires assure le rôle de première barrière contre les agressions extérieures grâce à la fonction muco-ciliaire. Les deux éléments fonctionnels de la fonction muco-ciliaire sont la couche de mucus sécrétée par l’épithélium et le battement des cils des cellules ciliées qui contribue à la mise en mouvement de cette couche et à son évacuation des bronches. Le mucus est un fluide complexe et hétérogène et ses propriétés mécaniques couplées aux mécanismes de coordination des cils restent encore mal compris. Mes travaux de thèse ont porté sur une approche biophysique de ces mécanismes. Premièrement, l’étude de la rhéologie du mucus a été menée à deux échelles : en macro-rhéologie de cisaillement et par micro-rhéologie active grâce aux pincettes optiques. Les pincettes optiques permettent également des mesures in situ sur le tissu et des mesures d’adhésion. L’utilisation de la rhéologie comme marqueur des pathologies respiratoires chroniques a été explorée. Deuxièmement, la quantification et la compréhension de la coordination spatiotemporelle de l’activité ciliaire et du transport du mucus engendré ont été conduites, en développant un nouvel outil de traitement d’images de vidéo-microscopie et d’analyse de donnéesUnderstanding and treating chronic respiratory diseases are growing medical challenges due to changes in our lifestyles and environment. The epithelium of the respiratory tract is the first barrier against external aggression, in particular thanks to the mucociliary function. Functional elements are the mucus layer lining the tissue and the beating of cilia from the ciliated cells of the epithelium. Mucus is a complex and heterogeneous fluid that acts as a protective barrier by trapping particles and pathogens present in the inhaled air, while the coordination of the cilia beating allows the directed transport of the mucus layer and its evacuation from the bronchi. The mechanical properties of mucus coupled with the coordination mechanisms of beating cilia are still poorly understood. My thesis work focused on two biophysical aspects of these mechanisms: i) the study of mucus rheology at two scales, in macro-rheology and by active micro-rheology using optical tweezers directly on the tissue; ii) the understanding and quantification of the spatiotemporal coordination of ciliary activity and on the associated mucus transport, by developing a new tool for processing video-microscopy images and data analysis
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Pandit, Yadav. "AZIMUTHAL ANISOTROPY IN HEAVY ION COLLISIONS." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1353871180.
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Gueleri, Roberto Alves. "Desenvolvimento de técnicas de aprendizado de máquina via sistemas dinâmicos coletivos." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-13112017-111652/.
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O aprendizado de máquina consiste em conceitos e técnicas que permitem aos computadores melhorar seu desempenho com a experiência, ou em outras palavras, aprender com dados. Duas de suas principais categorias são o aprendizado não-supervisionado e o semissupervisionado, que respectivamente consistem em inferir padrões em bases cujos dados não têm rótulo (classe) e classificar dados em bases parcialmente rotuladas. Embora muito estudado, trata-se de um campo repleto de desafios e com muitos tópicos abertos. Sistemas dinâmicos coletivos, por sua vez, são sistemas constituídos por muitos indivíduos, cada qual um sistema dinâmico por si só, de modo que todos eles agem coletivamente, ou seja, a ação de cada indivíduo é influenciada pela ação dos vizinhos. Uma característica notável desses sistemas é que padrões globais podem surgir espontaneamente das interações locais entre os indivíduos, fenômeno conhecido como emergência. Os desafios intrínsecos e a relevância do tema vêm motivando sua pesquisa em diversos ramos da ciência e da engenharia. Este trabalho de doutorado consiste no desenvolvimento e análise de modelos dinâmicos coletivos para o aprendizado de máquina, especificamente suas categorias não-supervisionada e semissupervisionada. As tarefas de segmentação de imagens e de detecção de comunidades em redes, que de certo modo podem ser entendidas como tarefas do aprendizado de máquina, são também abordadas. Em especial, desenvolvem-se modelos nos quais a movimentação dos objetos é determinada pela localização e velocidade de seus vizinhos. O sistema dinâmico assim modelado é então conduzido a um estado cujo padrão formado por seus indivíduos realça padrões subjacentes do conjunto de dados. Devido ao seu caráter auto-organizável, os modelos aqui desenvolvidos são robustos e as informações geradas durante o processo (valores das variáveis do sistema) são ricas e podem, por exemplo, revelar características para realizar soft labeling e determinar classes sobrepostas.Machine learning consists of concepts and techniques that enable computers to improve their performance with experience, i.e., learn from data. Unsupervised and semi-supervised learning are important categories of machine learning, which respectively consists of inferring patterns in datasets whose data have no label (class) and classifying data in partially-labeled datasets. Although intensively studied, machine learning is still a field full of challenges and with many open topics. Collective dynamical systems, in turn, are systems made of a large group of individuals, each one a dynamical system by itself, such that all of them behave collectively, i.e., the action of each individual is influenced by the action of its neighbors. A remarkable feature of those systems is that global patterns may spontaneously emerge from the local interactions among individuals, a phenomenon known as emergence. Their relevance and intrinsic challenges motivate research in various branches of science and engineering. In this doctorate research, we develop and analyze collective dynamical models for their usage in machine-learning tasks, specifically unsupervised and semi-supervised ones. Image segmentation and network community detection are also addressed, as they are related to machine learning as well. In particular, we propose to work on models in which the objects motion is determined by the location and velocity of their neighbors. By doing so, the dynamical system reaches a configuration in which the patterns developed by the set of individuals highlight underlying patterns of the dataset. Due to their self-organizing nature, it is also expected that the models can be robust and the information generated during the process (values of the system variables) can be rich and reveal, for example, features to perform soft labeling and determine overlapping classes.
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Mahault, Benoît. "Outstanding problems in the statistical physics of active matter." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS250/document.
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La matière active, désignant les systèmes hors d’équilibre composés de particules étant capable d’utiliser l’énergie présente dans leur environnement afin de se déplacer de façon systématique, a suscité beaucoup d’attention auprès des communautés de mécanique statistique et matière molle ces dernières décennies. Les systèmes actifs couvrent en effet un large panel d’exemples allant de la biologie aux granulaires. Cette thèse se concentre sur l’étude de modèles minimaux de matière active sèche (ceux pour lesquels le fluide dans lequel les particles sont immergées est négligé), tel que le modèle de Vicsek qui considère des particules ponctuelles se déplaçant à vitesse constante tout en alignant leur direction de mouvement avec celles de leurs voisins localement en présence de bruit, et définit une classe d’universalité hors équilibre pour la transition vers le mouvement collectif. Quatre problèmes en suspens ont été abordés : La définition d’une classe d’universalité en matière active sèche qui décrit des systèmes de particles présentant un alignement polaire et un mouvement apolaire. Cette nouvelle classe exhibe une transition continue vers un quasi-ordre polaire doté d’exposants variant continument, et donc analogue au modèle XY à l’équilibre, mais n’appartenant pas à la classe d’universalité Kosterlitz-Thouless. Ensuite, l’étude de la validité des théories cinétiques décrivant les modèles de type Vicsek, qui sont confrontées aux résultats obtenus aux niveaux microscopique et hydrodynamique. Puis une évaluation quantitative de la théorie de Toner et Tu, permettant de mesurer les exposants caractérisant les fluctuations dans la phase ordonnée du modèle de Vicsek, à partir de simulations numériques à grande échelle du modèle microscopique. Enfin, la création d’un formalisme pour la dérivation d’équations hydrodynamiques à partir de modèles de matière active sèche à trois dimensions, ainsi que leur étude au niveau linéaireActive matter, i.e. nonequilibrium systems composed of many particles capable of exploiting the energy present in their environment in order to produce systematic motion, has attracted much attention from the statistical mechanics and soft matter communities in the past decades. Active systems indeed cover a large variety of examples that range from biological to granular. This Ph.D. focusses on the study of minimal models of dry active matter (when the fluid surrounding particles is neglected), such as the Vicsek model: point-like particles moving at constant speed and aligning their velocities with those of their neighbors locally in presence of noise, that defines a nonequilibrium universalilty class for the transition to collective motion. Four current issues have been addressed: The definition of a new universality class of dry active matter with polar alignment and apolar motion, showing a continuous transition to quasilong-range polar order with continuously varying exponents, analogous to the equilibrium XY model, but that does not belong to the Kosterlitz-Thouless universality class. Then, the study of the faithfulness of kinetic theories for simple Vicsek-style models and their comparison with results obtained at the microscopic and hydrodynamic levels. Follows a quantitative assessment of Toner and Tu theory, which has allowed to compute the exponents characterizing fluctuations in the flocking phase of the Vicsek model, from large scale numerical simulations of the microscopic dynamics. Finally, the establishment of a formalism allowing for the derivation of hydrodynamic field theories for dry active matter models in three dimensions, and their study at the linear level
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Bregulla, Andreas Paul [Verfasser], Frank [Akademischer Betreuer] Cichos, Frank [Gutachter] Cichos, and Clemens [Gutachter] Bechinger. "Role of thermo-osmotic flows at low Reynolds numbers for particle driving and collective motion / Andreas Paul Bregulla ; Gutachter: Frank Cichos, Clemens Bechinger ; Betreuer: Frank Cichos." Leipzig : Universitätsbibliothek Leipzig, 2016. http://d-nb.info/1240482930/34.
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Lopez, Ugo. "Étude expérimentale et modélisation des déplacements collectifs chez deux espèces de poissons, Khulia mugil et hemigrammus rhodostomus." Toulouse 3, 2015. http://www.theses.fr/2015TOU30362.
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Alors que l'étude des domportements individuels permettant le mouvement collectif, très reliée historiquement à une approche computationnelle, cherche à prendre appui sur l'expérimentation en laboratoire, il apparaît importnat de prendre en compte les caractéristiques de la nage des espèces dont on modélise le comportement. L'inclusion dans la modélisation du comportement de kuhlia mugil des caractéristiques de nage de l'espèce, à vitesse constante et adaptant continûment son orientation, procède pour partie de la nécessité d'intégrer les données recueillies. Le modèle de déplacement résultant est très différent des modèles classiquement étudiés dans la littérature du point de vue de son formalisme et de ses propriétés. Dans cette thèse nous en prolongeons l'étude en explorant l'espace des états collectifs atteignables par la simulation numérique ainsi que sa sensibilité aux perturbations. Ayant développé un dispositif expérimantal permettant d'étudier les déplacements collectifs d'un modèle animal différent, Hemigrammus rhodostoomus, nous proposons un paradigme por son mode de nage constitué d'une succession discrète d'actes locomoteurs conduisant à une vitesse variable et à des décisions de réorientation ponctuelles. Nous exploitons par l'étude géométrique de sa nage spontanée dans un milieu confiné afin de comprendre sa réaction aux obstacles.
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Young, Alexander L., and Alexander L. Young. "Three Essays on Complex Systems: Self-Sorting in a One-Dimensional Gas, Collective Motion in a Two-Dimensional Ensemble of Disks, and Environment-Driven Seasonality of Mosquito Abundance." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624567.
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Complex systems offer broad, unique research challenges due to their inability to be understood through a classic reductionist perspective, as they exhibit emergent phenomena that arise through the interactions of their components. In this thesis, we briefly review some characteristics of complex systems and the interplay of mathematical and computational methods to study them. We then discuss these approaches, how they are implemented, and how they support one another in three settings. First, we present a study that connects weather data to seasonal population-abundance of mosquitoes, using a microscopic model. Secondly, we consider the collective motions that arise in ensembles of disks interacting through non-elastic collisions and investigate how such behaviors affect macroscopic transport properties. Finally, we consider a 'self-sorting' one-dimensional collection of point-particles. In all of these cases, agent-based models and simulations are used to guide analysis, and in the final example, we explain how the simulations led to new theorems. Articles and molecular dynamics computer codes are provided as appendices.
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Ющенко, Ольга Владимировна, Ольга Володимирівна Ющенко, Olha Volodymyrivna Yushchenko, and А. Ш. Баранова. "Синергетическое описание коллективного движения активных частиц." Thesis, Изд-во СумДУ, 2009. http://essuir.sumdu.edu.ua/handle/123456789/3919.
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Исследования показывают, что коллективное движение живых
организмов не зависит от уровня биологических скоплений, что
позволяет представить такие скопления как ансамбли активных
броуновских частиц, каждая из которых, обладая запасом внутренней
энергии, может менять свое внутреннее состояние. В результате
группа живых организмов может совершать следующие типы
движения: вращательное движение вокруг относительно пустого
центра масс; поступательное, при котором скопление движется как
целое; прерывистое – последовательное чередование указанных
режимов.
Для описания таких режимов движения в данной работе
используется трехпараметрическая система Лоренца, отвечающая
простейшему представлению самоорганизующейся системы.
При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/3919
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Marchetti, Benjamin. "Sédimentation de particules : effets collectifs et filaments déformables." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0364/document.
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Une étude expérimentale et numérique traitant de l'influence de structures tourbillonnaires sur la sédimentation de nuage de particules sphériques sous l'effet de la gravité est présentée dans une première partie de ce manuscrit. L'écoulement est créé par électro-convection, ce qui permet de générer un réseau de vortex contrôlés en vitesse et de taille constante qui imite un écoulement tourbillonnaire. Des techniques de PIV (Particle image-velocimetry) et de suivi de particules sont utilisés pour étudier la sédimentation du nuage.Le nuage est modélisé comme un ensemble de particules ponctuelles pour lesquelles les forces d'interaction hydrodynamiques entre particules sont prépondérantes. Le comportement du nuage est comparé aux prédictions obtenues avec des modèles numériques. Dans une seconde partie est présentée une étude expérimentale et numérique concernant la sédimentation à faible nombre de Reynolds de fibres flexibles dans un fluide visqueux au repos. L'état d'équilibre atteint par la fibre flexible est étudié. Nous identifions trois régimes ayant des signatures différentes sur l'état stationnaire de la fibre flexible: un régime de faibles déformations dans lequel la force de traînée est proportionnelle à celle d'une fibre sédimentant horizontalement par rapport à la gravité; un régime de grandes déformations dans lequel la force de traînée est aussi proportionnelle à la vitesse de la fibre, mais avec un coefficient de traînée qui est celui d'une fibre chutant parallèlement à la gravité; et un régime de reconfiguration élastique où le filament se déforme avec une traînée plus faible qui n'est plus proportionnelle à sa vitesse, mais à la racine carrée de celle-ciIn the first part, a jointed experimental and numerical study examining the influence of vortical structures on the settling of a cloud of solid spherical particles under the action of gravity at low Stokes numbers is presented. We use electro-convection to generate a two-dimensional array of controlled vortices which mimics a simplified vortical flow. Particle image-velocimetry and tracking are used to examine the motion of the cloud within this vortical flow. The cloud is modeled as a set of point-particles for which the hydrodynamic interaction is preponderant. The cloud behavior (trajectory, velocity, aspect ratio, break-up time …) is compared to the predictions of a two-way-coupling numerical simulation. In the second part, a jointed experimentally and numerical study on the dynamics of slender flexible filaments settling in a viscous fluid at low Reynolds number is presented. The equilibrium state of a flexible fiber settling in a viscous fluid is examined using a combination of macroscopic experiments, numerical simulations and scaling arguments. We identify three regimes having different signatures on this equilibrium configuration of the elastic filament: a weak deformation regime wherein the drag is proportional to the fiber velocity settling perpendicular to the gravity; a large deformation regime wherein the drag is proportional to the fiber velocity settling parallel to the gravity and an intermediate elastic reconfiguration regime where the filament deforms to adopt a shape with a smaller drag which is no longer linearly proportional to the velocity but to the square root of the velocity
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Pédèches, Laure. "Stochastic models for collective motions of populations." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30083/document.
Full textAbstract:
Dans cette thèse, on s'intéresse à des systèmes stochastiques modélisant un des phénomènes biologiques les plus mystérieux, les mouvements collectifs de populations. Pour un groupe de N individus, vus comme des particules sans poids ni volume, on étudie deux types de comportements asymptotiques : d'un côté, en temps long, les propriétés d'ergodicité et de flocking, de l'autre, quand le nombre de particules N tend vers l'infini, les phénomènes de propagation du chaos. Le modèle, déterministe, de Cucker-Smale, un modèle cinétique de champ moyen pour une population sans structure hiérarchique, est notre point de départ : les deux premiers chapitres sont consacrés à la compréhension de diverses dynamiques stochastiques qui s'en inspirent, du bruit étant rajouté sous différentes formes. Le troisième chapitre, originellement une tentative d'amélioration de ces résultats, est basé sur la méthode du développement en amas, un outil de physique statistique. On prouve l'ergodicité exponentielle de certains processus non- markoviens à drift non-régulier. Dans la dernière partie, on démontre l'existence d'une solution, unique dans un certain sens, pour un système stochastique de particules associé au modèle chimiotactique de Keller et SegelIn this thesis, stochastic dynamics modelling collective motions of populations, one of the most mysterious type of biological phenomena, are considered. For a system of N particle-like individuals, two kinds of asymptotic behaviours are studied: ergodicity and flocking properties, in long time, and propagation of chaos, when the number N of agents goes to infinity. Cucker and Smale, deterministic, mean-field kinetic model for a population without a hierarchical structure is the starting point of our journey: the fist two chapters are dedicated to the understanding of various stochastic dynamics it inspires, with random noise added in different ways. The third chapter, an attempt to improve those results, is built upon the cluster expansion method, a technique from statistical mechanics. Exponential ergodicity is obtained for a class of non-Markovian process with non-regular drift. In the final part, the focus shifts onto a stochastic system of interacting particles derived from Keller and Segel 2-D parabolic-elliptic model for chemotaxis. Existence and weak uniqueness are proven