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1
Obligado, Martín. "Fluid-particle interactions : from the simple pendulum to collective effects in turbulence". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI108/document.
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Cette thèse est organisée en deux parties. Après une brève introduction théorique (chapitre 1) et une discussion présentant la soufflerie du LEGI et des techniques expérimentales utilisées (chapitre 2), une première partie étudie les effets individuels des particules dans les écoulements tantôt laminaires et turbulents. Dans une seconde partie je me suis intéressé aux effets collectifs d’une population dense d’inclusions en interaction avec un champ turbulent.Dans le chapitre 3, nous montrons que l’équilibre d’un disque pendulaire faisant face à un écoulement présentant une vitesse moyenne présente un comportement bi-stable et hystérétique. Nous donnons une interprétation simple de ce comportement en termes d’une description par deux puits de potentiel, nécessitant uniquement de connaître la dépendance angulaire du coefficient de trainée normale d’une plaque statique inclinée. Nous étudions l’influence de la turbulence sur l’équilibre du pendule en général et sur la bi-stabilité observée en particulier.La dynamique des objets tractés dans un environnement fluide est d’intérêt pour de nombreuses situations pratiques. Les chapitres 4,5 et 6 concernent l’étude expérimentale de l’équilibre et de la stabilité de la trajectoire d’une sphère tractée à vitesse constante. Dans le chapitre 4, nous avons vu que le sillage d'une sphère peut produire un mouvement hélicoïdal d'une sphère remorqué par un fil. Nous avons constaté qu'il existe un nombre de Reynolds (défini avec le diamètre de la particule et la vitesse moyenne de l’écoulement) particulier pour activer cette motion instable. Une trajectoire en trois dimensions est reconstruite avec un dispositif expérimental extrêmement simple, utilisé pour la caractérisation de la forme de la trajectoire des particules. Dans le chapitre 5, nous étudions expérimentalement l'équilibre et la stabilité de la trajectoire d'une sphère remorqué à une vitesse constante dans la avec un rapport longueur - diamètre sans précédent. En ce chapitre, nous étudions les instabilités développées dans le fil pour un écoulement laminaire. Diffèrent types d’instabilités ont été trouvés dans cette expérience. Dans le chapitre 6, le même système est étudié, mais l'écoulement environnant est turbulent. Nous nous concentrons sur la comparaison entre la dynamique turbulente de la sphère tractée et d’une sphère librement advectèe. Nos résultats sont en accord avec un scénario de filtrage résultant du temps de réponse visqueuse d'une particule d'inertie dont la dynamique est couplée au fluide environnant par la force de traînée. Une caractéristique frappante des écoulements turbulents chargés de particules inertielles est la concentration préférentielle qui conduit à de très fortes hétérogénéités du champ de concentration en particules à différentes échelles. Les diagrammes de Voronoi ont été utilisés pour caractériser quantifier ce phénomène.En ce qui concerne les effets collectifs, trois écoulements différents ont été étudiés : bulles d’air (particules moins denses que le fluide, avec une taille de l’ordre de l´échelle de Kolmogorov) dans un canal a eau (chapitre 7), des particules solides légèrement plus denses que le fluide et diamètre supérieur à l´échelle de Kolmogorov dans une écoulement de von Kármán (chapitre 8) et gouttelettes d’eau dans la soufflerie (chapitre 9) ; de particules beaucoup plus denses que le fluide et diamètre inférieur à l’échelle de Kolmogorov. Enfin, nous proposons une nouvelle méthode de reconstruction des champs de concentration des particules dans les expériences par analogie avec le fonctionnement des caméras linéaire, et en exploitant l’hypothèse de Taylor dans la soufflerie. Cette nouvelle approche nous permet de reconstruire des champs de particules de plusieurs mètres de long. Ces champs permettent d’analyser la formation des superclusters. Nous montrons en effet que les clusters tendent eux-mêmes à s’organiser en superclusters (amas d’amas)This PhD thesis covers many features of fluid-particle interactions, ranging from a simple pendulum inmersed in a flow to the presence of superclusters of water droplets in a wind tunnel.The simplest case studied was a pendulum with a pendulum-blob facing the wind in the wind-tunnel. As the pendulum-blob was a plate, the aerodynamic coefficients as a function of the angle between the plate and the streamwise velocity present a non-trivial behavior, resulting in an hysteresis cycle. We also investigate the influence of turbulence on the equilibrium of the pendulum in general and on the observed bi-stability in particular.Then, different instabilities of towed systems has been studied. In chapter 4 we have seen that the wake of a sphere can produce helicoidal motion of a sphere towed by a wire. We found that there exists a particle Reynolds number Rep threshold for activating this unstable motion. A three-dimensional trajectory was reconstructed with an extremely simple experimental setup, used for characterizing the shape of particle's trajectory. In chapter 5 we investigate experimentally the equilibrium and the stability of the trajectory of a sphere towed at constant velocity in the wind tunnel at the tip of a cable with unprecedented large length-to-diameter aspect ratio. In thist chapter we study the instabilities developped in the wire for a laminar flow.Flutter and divergence instabilities has been found in this experiment.In chapter 6 the same system is studied, but the surrounding flow is turbulent. In this chapter we focus on a comparison with this towed system with freely advected particles in turbulence. Our results are consistent with a filtering scenario resulting from the viscous response time of an inertial particle whose dynamics is coupled to the surrounding fluid via the dragforce.Therefore, depending on several parameters such as the Reynolds number of the particle, the wire or the fluctuations level of the flow, a whole family of instabilities can appear, with no trivial dependencies and important consequences considering different applications of such systems.Concerning the collective effects, three different flows have been studied: a water tunnel, a von Karman flow and a wind tunnel. A broad range of Reynolds numbers, dissipation scales and particles diameters and densities has been covered. Using Voronoi diagrams, we have quantified preferential concentration as a function of the Stokes number and the Reynolds number. In chapter 7 and 8 simultaneous PIV measurements complemented the inertial particles acquisitions. The goal was to analyze if the particles tend to stick into special regions of the flow.In the last chapter also DNS have been performed for comparing with experimental results. A sweep-stick mechanism, in which inertial particles tend to have the same statistics as zero-acceleration points has been proved to be consistent with our results.Finally, a promising new technique has been presented. Based on the standard measurements, a spatial field has been reconstructed allowing us to acquire a several meters long image of particles. The enormous amount of structures present in the image has evidenced that the clusters are grouped at the same time in bigger clusters (i.e. clusters form clusters, that we call superclusters). This new result is still being studied and presents a new and fascinating field for studying particle-flow interactions
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Gazuz, Igor. "Active and passive particle transport in dense colloidal suspensions". [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-66299.
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Granick, Steve. "Surprises from single-particle imaging of passive and active diffusion". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179310.
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Pullen, John. "Particle image velocimetry applied to waves with surface active films". Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/12808.
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The technique of digital particle image velocimetry (DPIV) and the related technique of particle tracking velocimetry (PTV) are described. These techniques were extended and applied by the author to the study of surface active chemical films on the mechanics of capillary-gravity waves. The two custom-made facilities for these studies are described along with specialised image processing software developed by the author. Finally, results from a series of experiments are presented which detail the damping of wind waves by surface active films, measurements of wind induced surface drift and the alteration of surface particle trajectories. Results from all three experiments were compared with theoretical predictions.
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Granick, Steve. "Surprises from single-particle imaging of passive and active diffusion". Diffusion fundamentals 20 (2013) 1, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13521.
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Tarama, Mitsusuke. "Dynamics of active deformable particle - Two types of active spinning motions and dynamics in external flow field -". 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199091.
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Deptuch, Grzegorz. "New Generation of Monolithic Active Pixel Sensors for Charged Particle Detection". Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13115.
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Hernandez, Jorge L. Yordan. "Kinetics of bubble-particle adhesion in flotation". Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/91117.
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In order to study the role of electrical charge existing on air bubbles in the kinetics of the particle-bubble adhesion process in froth flotation, the zeta potential of microbubbles in the 40 -to 80-micron size range have been determined by means of a simple microelectrophoresis technique. In general, the bubble charge is determined by the charge of the polar head of the surfactants when ionic surfactants are used to produce bubbles. However, the magnitude of the zeta-potential is reduced when the surfactants are hydrolyzed. When using nonionic surfactants, the bubbles exhibit isoelectric points (i.e.p) in acidic and neutral pH ranges. It appears that the location of an i.e.p. is determined by the acid-base property of the surfactant molecule used. The negative charges observed with air bubbles and oil droplets in the absence of surfactants can be explained by the differences in the hydration energies of H⁺ and OH⁻ ions. An increase in the concentration of ionic surfactants results in an increase in bubble charge. However, the increase is minimal or non-existant when nonionic surfactants are used.
The flotation chemistry of the quartz-amine system has been studied using an induction time apparatus constructed in the present work which has a sensitivity limit of 100-150 micro-seconds. The basic unit is similar to the one used by Eigeles and Volova (1960) and Trahar (1983), but it operates with a micro-computer and has a greater sensitivity. It has been found that at a given dodecyl ammonium hydrochloride concentration, the induction time is at a minimum at approximately pH 10.5. At this pH, the collector hydrolizes to form neutral amine and the flotation recovery reaches a maximum, suggesting that iono-molecular species are the surface-active species responsible for flotation. This finding confirms the earlier conclusions obtained using the surface tension (Somasundaran, 1976; Finch and Smith, 1973) and the contact angle (Smith, 1963) techniques. The induction time measurements have also been conducted as a function of particle size, collector concentration, indifferent electrolyte concentration and temperature. The results are compared with flotation data, bubble charge, particle charge and film thickness.
Results of the induction time and microflctation experiments conducted using bubbles and particles of known electrical properties indicate that if the potential on the air/water interface is increase to a high value with the same sign as that of the s/l interface (e.g. by adding a suitable surfactant) the flotation kinetic is retarded; conversely, surfactant of the opposite sign can enhance the adhesion process.M.S.
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Lubbe, Elizabeth Cornelia. "Influence of particle size on solubility of active pharmaceutical ingredients / E.C. Lubbe". Thesis, North-West University, 2012. http://hdl.handle.net/10394/8763.
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The aqueous solubility of an active pharmaceutical ingredient (API) is an important property that requires evaluation during early development and prior to formulation of the final product. With general, experimental, solubility testing of different APIs, the question always arises as to whether particle size had been determined beforehand or not. All available literature suggests that particle size, for pharmaceutical powders, does not significantly affect equilibrium solubility. The dissolution rate will differ according to different particle sizes, but the overall results should be identical after equilibrium is established.
This study was therefore planned to investigate as to whether different particle size fractions of the same API, dissolving at different rates, would all reach solubility equilibrium within 24 hours. Also, APIs from different solubility classes were investigated, because poorly soluble substances would most likely require a longer period of time to equilibrate. The time period of 24 hours was selected, because many published solubility studies report using that interval and is it the standard for our research group also.
Available APIs were selected to determine the influence (if any) of particle size on their equilibrium solubilities and the time required for attaining that status. For the purpose of this investigation, five APIs were selected from compounds at our disposal in-house, ranging from freely soluble to poorly soluble in the order: chloroquine phosphate > pyrazinamide > mefloquine hydrochloride > closantel sodium > roxithromycin.
Solubility studies were successfully completed on four of the five APIs selected. For closantel sodium, pyrazinamide and roxithromycin it was demonstrated that the 24 hour test period was sufficient for the attainment of equilibrium solubility, regardless of the particle size fractions tested. Surprisingly, the only API in this study for which 24 hours was an insufficient test period was mefloquine HCl, which was not the least soluble compound tested. Further testing would be required to clarify this anomaly.
What was evident from the outcomes of this investigation was that although the ubiquitous 24 hour solubility test may work well in many cases, its suitability should be reviewed on a case-by-case basis and not just for the most poorly soluble compounds. Researchers testing solubility at temperatures lower than 37°C should be especially cautious of using a standardised test period, because equilibrium solubility would take longer to achieve with less energy available to the system.Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013
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Reichert, Julian [Verfasser] y Hartmut [Gutachter] Löwen. "Transport Coefficients in Dense Active Brownian Particle Systems / Julian Reichert ; Gutachter: Hartmut Löwen". Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2021. http://d-nb.info/1227038607/34.
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Gutschick, David D. "Characterization of Soft Gels with 2P Microrheology, a Novel, Active Paired-Particle Method". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534742722866439.
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Aland, Sebastian. "Modelling of two-phase flow with surface active particles". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-92397.
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Kolloidpartikel die von zwei nicht mischbaren Fluiden benetzt werden, tendieren dazu sich an der fluiden Grenzfläche aufzuhalten um die Oberflächenspannung zu minimieren. Bei genügender Anzahl solcher Kolloide werden diese zusammengedrückt und lassen die fluide Grenzfläche erstarren. Das gesamte System aus Fluiden und Kolloiden bildet dann eine spezielle Emulsion mit interessanten Eigenschaften. In dieser Arbeit wird ein kontinuum Model für solche Systeme entwickelt, basierend auf den Prinzipien der Massenerhaltung und der themodynamischen Konsistenz. Dabei wird die makroskopische Zwei-Phasen-Strömung durch eine Navier-Stokes Cahn-Hilliard Gleichung modelliert und die mikroskopischen Partikel an der fluiden Grenzfläche durch einen Phase-Field-Crystal Ansatz beschrieben. Zur Evaluation des verwendeten Strömungsmodells wird ein Test verschiedener Navier-Stokes Cahn-Hilliard Modelle anhand eines bekannten Benchmark Szenarios durchgeführt. Die Ergebnisse werden mit denen von anderen Methoden zur Simulation von Zwei-Phasen-Strömungen verglichen. Desweiteren wird eine neue Methode zur Simulation von Zwei-Phasen-Strömungen in komplexen Gebieten vorgestellt. Dabei wird die komplexe Geometrie implizit durch eine Phasenfeldvariable beschrieben, welche die charakteristische Funktion des Gebietes approximiert. Die Strömungsgleichungen werden dementsprechend so umformuliert, dass sie in einem größeren und einfacheren Gebiet gelten, wobei die Randbedingungen implizit durch zusätzliche Quellterme eingebracht werden. Zur Einarbeitung der Oberflächenkolloide in das Strömungsmodell wird schließlich die Variation der freien Energie des Gesamtsystems betrachtet. Dabei wird die Energie der Partikel durch die Phase-Field-Crystal Energie approximiert und die Energie der Oberfläche durch die Ginzburg-Landau Energie. Eine Variation der Gesamtenergie liefert dann die Phase-Field-Crystal Gleichung und die Navier-Stokes Cahn-Hilliard Gleichungen mit zusätzlichen elastischen Spannunngen. Zur Validierung des Ansatzes wird auch eine sharp interface Version der Gleichungen hergeleitet und mit der zuvor hergeleiteten diffuse interface Version abgeglichen. Die Diskretisierung der erhaltenen Gleichungen erfolgt durch Finiten Elemente in Kombination mit einem semi-impliziten Euler Verfahren. Durch numerische Simulationen wird die Anwendbarkeit des Modells gezeigt und bestätigt, dass die oberflächenaktiven Kolloide die fluide Grenzfläche hinreichend steif machen können um externen Kräften entgegenzuwirken und das gesamte System zu stabilisierenColloid particles that are partially wetted by two immiscible fluids can become confined to fluidfluid interfaces. At sufficiently high volume fractions, the colloids may jam and the interface may crystallize. The fluids together with the interfacial colloids compose an emulsion with interesting new properties and offer an important route to new soft materials. Based on the principles of mass conservation and thermodynamic consistency, we develop a continuum model for such systems which combines a Cahn-Hilliard-Navier-Stokes model for the macroscopic two-phase fluid system with a surface Phase-Field-Crystal model for the microscopic colloidal particles along the interface. We begin with validating the used flow model by testing different diffuse interface models on a benchmark configuration for a two-dimensional rising bubble and compare the results with reference solutions obtained by other two-phase flow models. Furthermore, we present a new method for simulating two-phase flows in complex geometries, taking into account contact lines separating immiscible incompressible components. In this approach, the complex geometry is described implicitly by introducing a new phase-field variable, which is a smooth approximation of the characteristic function of the complex domain. The fluid and component concentration equations are reformulated and solved in larger regular domain with the boundary conditions being implicitly modeled using source terms. Finally, we derive the thermodynamically consistent diffuse interface model for two-phase flow with interfacial particles by taking into account the surface energy and the energy associated with surface colloids from the surface PFC model. The resulting governing equations are the phase field crystal equations and Navier-Stokes Cahn-Hilliard equations with an additional elastic stress. To validate our approach, we derive a sharp interface model and show agreement with the diffuse interface model. We demonstrate the feasibility of the model and present numerical simulations that confirm the ability of the colloids to make the interface sufficiently rigid to resist external forces and to stabilize interfaces for long times
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Nguyen, Minh Chau. "Hydrodynamic transport phenomena in suspension of microalgae : particle separation using pulsatile flow". Thesis, Université Paris Cité, 2021. http://www.theses.fr/2021UNIP7174.
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La séparation des particules est nécessaire dans de nombreuses applications en chimie, physique, biologie, domaines médicaux et biotechnologie. Par exemple, la récolte de biomasse, qui est l'une des étapes clés de la production de biocarburants à partir des microalgues et des cyanobactéries, est un processus complexe et coûteux (20-30 % du coût total) en raison de la petite taille et aussi de la faible différence entre la densité des micro-organismes et celle de leurs milieux de culture. Ainsi, de nouvelles techniques peu coûteuses sont nécessaires pour remplacer ou améliorer le processus de la séparation. Tandis que plusieurs méthodes passives et actives ont été proposées pour la séparation des particules en écoulement stationnaire, l'écoulement pulsé a reçu moins d'attention. Le but de cette étude est de déterminer les effets de la pulsation d'écoulement sur la séparation des particules dans un microcanal du type « double Y». Seulement l'un des deux écoulements entrants contient des particules et l'efficacité de la séparation est définie comme le rapport entre le nombre des particules s'échappant de la sortie opposée et le nombre total des particules. Les cellules mortes et motiles de Chlamydomonas reinhardtii sont respectivement utilisées comme particules passives et actives. Des expériences microfluidiques et des simulations sont réalisées pour chaque partie de l'étude et les principaux résultats sont résumés ci-dessous: Pour les particules passives: - Lorsque les écoulements entrants dans le microcanal sont stationnaires, le seul paramètre qui permet de contrôler la séparation des particules est le rapport entre les débits aux entrées. L'efficacité de la séparation augmente avec l'augmentation de ce rapport. Pour approcher l'efficacité maximale (0,5), ce rapport doit être supérieur à 20, ce qui n'est pas toujours pratique. - Lorsque les écoulements entrants sont pulsés avec un déphasage, le réglage de ce déphasage peut contrôler l'efficacité de la séparation. - Lorsque 0,5 < amplitude de pulsation < 2 et 1 s < période de pulsation < 10 s, l'efficacité de la séparation augmente avec le déphasage de sorte qu'un déphasage de 180° aboutit à une efficacité maximale. Une tendance similaire est observée pour des valeurs plus élevées de l'amplitude (comme beta = 5) uniquement si la période de pulsation est suffisamment petite. Pour les particules actives: - Les particules actives (cellules motile) n'obéissent pas au protocole de contrôle imposé par la pulsation à l'entrée du système. Comme les particules actives choisissent aléatoirement leur sortie du microcanal, l'efficacité de la séparation reste toujours proche de 0,5. Par conséquent, la pulsation de l'écoulement (seule) ne présente aucun avantage par rapport à un écoulement stationnaire pour la séparation des particules actives. - Cependant, lorsque le comportement phototactique des algues est activé, l'avantage de la pulsation devient évident. En présence d'une stimulation lumineuse, l'efficacité de la séparation augmente respectivement jusqu'à 65 % et 75 % dans les écoulements stationnaires et pulsés. Bien que nos expériences soient menées sur une algue modèle (Chlamydomonas reinhardtii), une simulation numérique a démontré que l'idée d'utiliser un écoulement pulsé peut être étendue à la séparation de toutes autres particules actives stimulées par un champ externe attractif ou répulsif. Ainsi, les applications potentielles peuvent aller au-delà de la récolte des algues pour le control et l'amélioration des processus de séparation, de sélection ou d'accumulation sans avoir besoin de composants mécaniques ou de substances chimiquesParticle separation is an important requirement in chemistry, physics, biology, medical domains and biotechnology. For instance, the conventional biomass harvesting which is one of the key steps in production of biofuels from non-feed stocks such as microalgae and cyanobacteria, is a complex and costly process (20-30% of total cost) due to the small size and low-density difference of the photosynthesis microorganisms and their growth media. Thus, novel low-cost techniques are required to substitute or improve the downstream separation process. While a variety of active and passive techniques have been proposed for the separation process in steady flows, pulsatile flow has received much less attention. The purpose of this study is to determine the effects of flow pulsation on the separation of particles in a double Y-microchannel. Only one of the two entering flows contains the particles and the separation efficiency is defined as the ratio of the particles escaping from the opposite outlet to the total number of particles. Dead and motile cells of Chlamydomonas reinhardtii are used as passive and active particles, respectively. Both experiments and simulations are carried out for each part of the study. The key results can be summarized as follows: For passive particles: - When the inlet flows are in a steady regime, the only parameter that allows controlling the particle separation/distribution is the ratio between the flow rates at the inlets. The separation efficiency increases with increasing this ratio. To approach the maximum efficiency (0.5), this ratio should be more than 20, which is not always practical. - When the inlet flows are pulsating with a phase shift, adjusting the phase shift between the inlet flows can control the separation efficiency. - When 0.5 < pulsation amplitude < 2 and 1 s < pulsation period < 10 s, the separation efficiency increases with the phase shift such that phi = 180° gives the highest efficiency. A similar trend can be observed for higher values of amplitude (like beta = 5) only if the pulsation period is small enough. For active particles: - Active particles (motile cells) do not obey the control protocol imposed at the inlet of the system. The separation efficiency remains around 0.5 implying that active particles choose their exit from the microchannel randomly. Therefore, pulsation (alone) shows no advantage for separation of the active particles compared to a steady flow. - However, when the phototactic behavior of the algae is coupled with pulsatile flow features, the advantage of pulsation becomes clear. In the presence of light stimulation, the separation efficiency increases to 65% and 75% in steady and pulsatile flows respectively. Although the experiments are conducted on the well-known model alga, Chlamydomonas reinhardtii, a simplified numerical simulation demonstrated that the idea can be extended to any other active particle stimulated by an attractive or repulsive external field. Thus, the potential applications of pulsatile flow can go beyond algae harvesting to control and improve separation, selection or accumulation processes without using any mechanical component or chemical substance
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Mazyan, Walid Ibrahim. "Increasing efficiency of particle separation in natural gas cyclones using passive and active enhancements". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61486.
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Natural gas goes through several processes ranging from extraction, treatment, liquefaction and regasification. Among these processes, treatment, specifically the removal of solid particles, has a crucial role due to its impact on annual maintenance and efficiency of downstream equipment and processes. In essence, solid particles need to be removed at a high efficiency without increasing the pressure drop and hence power consumption in the system. Cyclone separators have been used to remove large solid particles through centrifugal forces. The main disadvantage of cyclones is their efficiency, especially for particles below 5 micrometer. Numerous studies have been conducted in improving the separation efficiency of cyclones by either spraying a mist of water or changing their geometry to increase the centrifugal forces. The main disadvantage of the majority of the geometrical modifications is the fact that they cause a significant increase in the pressure drop (at least by 15%). The mist approach, increasing the density of the particles and hence the efficiency, relies on water which adds additional cost.
This research focuses on the implementation of active and passive modifications to enhance the separation efficiency of cyclones without increasing the pressure drop. The active modifications include the addition of electrostatic and magnetic forces, effects of which are studied theoretically and experimentally. The passive method involves addition of a tangential collecting chamber at the conical section. The effect of such a modification is studied thoroughly based on experiments and CFD modeling. The theoretical and experimental investigation of the electrostatic and magnetic effects show an increase in the separation efficiency of 34% and 24% for 4-micrometer particles, respectively. The results of the CFD analysis and experimental study for the passive modification (i.e., the additional chamber) suggest an increase of maximum 26% for 4-micrometer particles. The CFD results conducted for a range of particles also suggest that such a geometrical modification can increase the efficiency by 51% for 1-micrometer particles for which the increase in the pressure drop increase is only 8% (half of the minimum value reported before). These increases in the efficiency will make the cyclones a viable separator with minimum maintenance costs.Graduate Studies, College of (Okanagan)
Graduate
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Wei, Xiaomin. "Study and improvement of radiation hard monolithic active pixel sensors of charged particle tracking". Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00953382.
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Monolithic Active Pixel Sensors (MAPS) are good candidates to be used in High Energy Physics (HEP) experiments for charged particle detection. In the HEP applications, MAPS chips are placed very close to the interaction point and are directly exposed to harsh environmental radiation. This thesis focuses on the study and improvement of the MAPS radiation hardness. The main radiation effects and the research progress of MAPS are studied firstly. During the study, the SRAM IP cores built in MAPS are found limiting the radiation hardness of the whole MAPS chips. Consequently, in order to improve the radiation hardness of MAPS, three radiation hard memories are designed and evaluated for the HEP experiments. In order to replace the SRAM IP cores, a radiation hard SRAM is developed on a very limited area. For smaller feature size processes, in which the single event upset (SEU) effects get significant, a radiation hard SRAM with enhanced SEU tolerance is implemented by an error detection and correction algorithm and a bit-interleaving storage. In order to obtain higher radiation tolerance and higher circuitry density, a dual-port memory with an original 2-transistor cell is developed and evaluated for future MAPS chips. Finally, the radiation hardness of the MAPS chips using new available processes is studied, and the future works are prospected.
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Hoffmann, McElory Roberto. "Stochastic visual tracking with active appearance models". Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1381.
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Thesis (PhD (Applied Mathematics))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: In many applications, an accurate, robust and fast tracker is needed, for example in surveillance, gesture recognition, tracking lips for lip-reading and creating an augmented reality by embedding a tracked object in a virtual environment. In this dissertation we investigate the viability of a tracker that combines the accuracy of active appearancemodels with the robustness of the particle lter (a stochastic process)—we call this combination the PFAAM. In order to obtain a fast system, we suggest local optimisation as well as using active appearance models tted with non-linear approaches. Active appearance models use both contour (shape) and greyscale information to build a deformable template of an object. ey are typically accurate, but not necessarily robust, when tracking contours. A particle lter is a generalisation of the Kalman lter. In a tutorial style, we show how the particle lter is derived as a numerical approximation for the general state estimation problem. e algorithms are tested for accuracy, robustness and speed on a PC, in an embedded environment and by tracking in ìD. e algorithms run real-time on a PC and near real-time in our embedded environment. In both cases, good accuracy and robustness is achieved, even if the tracked object moves fast against a cluttered background, and for uncomplicated occlusions.
AFRIKAANSE OPSOMMING: ’nAkkurate, robuuste en vinnige visuele-opspoorderword in vele toepassings benodig. Voorbeelde van toepassings is bewaking, gebaarherkenning, die volg van lippe vir liplees en die skep van ’n vergrote realiteit deur ’n voorwerp wat gevolg word, in ’n virtuele omgewing in te bed. In hierdie proefskrif ondersoek ons die lewensvatbaarheid van ’n visuele-opspoorder deur die akkuraatheid van aktiewe voorkomsmodellemet die robuustheid van die partikel lter (’n stochastiese proses) te kombineer—ons noem hierdie kombinasie die PFAAM. Ten einde ’n vinnige visuele-opspoorder te verkry, stel ons lokale optimering, sowel as die gebruik van aktiewe voorkomsmodelle wat met nie-lineêre tegnieke gepas is, voor. Aktiewe voorkomsmodelle gebruik kontoer (vorm) inligting tesamemet grysskaalinligting om ’n vervormbaremeester van ’n voorwerp te bou. Wanneer aktiewe voorkomsmodelle kontoere volg, is dit normaalweg akkuraat,maar nie noodwendig robuust nie. ’n Partikel lter is ’n veralgemening van die Kalman lter. Ons wys in tutoriaalstyl hoe die partikel lter as ’n numeriese benadering tot die toestand-beramingsprobleem afgelei kan word. Die algoritmes word vir akkuraatheid, robuustheid en spoed op ’n persoonlike rekenaar, ’n ingebedde omgewing en deur volging in ìD, getoets. Die algoritmes loop intyds op ’n persoonlike rekenaar en is naby intyds op ons ingebedde omgewing. In beide gevalle, word goeie akkuraatheid en robuustheid verkry, selfs as die voorwerp wat gevolg word, vinnig, teen ’n besige agtergrond beweeg of eenvoudige okklusies ondergaan.
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Gross, Brandi Nicole. "Input of Factor Graphs into the Detection, Classification, and Localization Chain and Continuous Active SONAR in Undersea Vehicles". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/56609.
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The focus of this thesis is to implement factor graphs into the problem of detection, classification, and localization (DCL) of underwater objects using active SOund Navigation And Ranging (SONAR). A factor graph is a bipartite graphical representation of the decomposition of a particular function. Messages are passed along the edges connecting factor and variable nodes, on which, a message passing algorithm is applied to compute the posterior probabilities at a particular node.
This thesis addresses two issues. In the first section, the formulation of factor graphs for each section of the DCL chain required followed by their closed-form solutions. For the detector, the factor graph determines if the signal is a detection or simply noise. In the classifier, it outputs the probability for the elements in the class. Last, when using a factor graph for the tracker, it gives the estimated state of the object being tracked.
The second part concentrates on the application to Continuous Active SONAR (CAS). When using CAS, a bistatic configuration is used allowing for a more rapid update rate where two unmanned underwater vehicles (UUVs) are used as the receiver and transmitter. The goal is to evaluate CAS's effectiveness to determine if the tracking accuracy improves as the transmit interval decreases. If CAS proves to be more efficient in target tracking, the next objective is to determine which messages sent between the two UUVs are most beneficial. To test this, a particle filter simulation is used.Master of Science
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Garcia, Michaël. "Hydrodynamique de micro-nageurs". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY011/document.
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Les suspensions d'objets microscopiques ayant la faculté de se déplacer par eux-mêmes dans le fluide qui les entoure sont des systèmes qui présentent un intérêt croissant dans la communauté scientifique. Du fait de leur dynamique intrinsèquement hors-équilibre au sens de la physique statistique, ils génèrent des effets particulièrement complexes. Parmi les micro-objets autopropulsés existants, les micro-algues vertes représentent une part importante de la biomasse de la Terre et participent activement au retraitement du CO2 par leur activité photosynthétique. Elles présentent de plus un remarquable potentiel dans les domaines de la production de bio-carburants, du retraitement des déchets, de la fabrication de cosmétiques et de compléments alimentaires. La compréhension de la dynamique de nage de ce type de microorganisme est d'un intérêt primordial d'un point de vue industriel. Cet ouvrage présente l'étude de la dynamique de la micro-algue Chlamydomonas Reinhardtii. En utilisant un système de suivi de particules en imagerie optique que nous avons développé, nous analysons ici le mécanisme fondamental de nage utilisé par cette algue jusqu'à ses implications en terme d'effets collectifs sur la dynamique de nage d'une suspension semi-diluéeThe suspensions of microscopic objects with the ability to propel themselves into the surrounding fluid are systems of growing interest in the scientific community. Due to their intrinsic out-of-equilibrium dynamics in the sense of statistical physics, they generate complex effects. Among the existing self-propelled micro-objects, green micro-algae are an important part of the biomass of Earth and they actively participate to the recycling of CO2 by their photosynthetic activity. Moreover they have remarkable potential for the production of bio-fuels, waste reprocessing, cosmetics and dietary supplements production. From an industrial point of view, understanding the dynamics of this type of swimming microorganism is of primary interest. This work presents the study of the dynamics of microalgae Chlamydomonas Reinhardtii. Using a system of particle tracking with optical imaging that we have developed, we analyze the mechanism of stroke used by the algae up to its implications in terms of collective effects on the dynamics of swimming in a semi-dilute suspension
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Hoshi, Kento. "Study on Active Spacecraft Charging Model and its Application to Space Propulsion Systeｍ". Kyoto University, 2018. http://hdl.handle.net/2433/232002.
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Greber, Johannes [Verfasser] y Walter [Akademischer Betreuer] Zimmermann. "On Effects of Hydrodynamic Interaction in Active and Passive Suspensions : Multi Particle Simulations / Johannes Greber ; Betreuer: Walter Zimmermann". Bayreuth : Universität Bayreuth, 2017. http://d-nb.info/1132200938/34.
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Torres, i. Albà Núria. "High Energy Processes in Active Galaxies". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668158.
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This thesis has as an objective the study of very energetic phenomena in the central regions of active galaxies. Intense star formation is triggered by mergers of galaxies, and the funneling of large quantities of gas toward the inner regions is thought to also cause accretion onto the central black hole. Whether the two processes necessarily take place together as a step of galaxy evolution is still debated.
Regardless of the origin of their connection, star formation and strong AGN activity often coexist in the nuclei of galaxies. Even after star formation is no longer ongoing, the nuclear starburst in a merger results in the formation of galactic bulges. Therefore, stellar densities in the inner kiloparsecs of a galaxy are typically high. As stars, or star forming regions, are close to the AGN, interaction between the two is expected to be frequent, and it can result in a multitude of phenomena worthy of study.
The thesis thus focuses on high energy processes taking place in regions where AGN activity and stellar presence is likely important. In particular, the goal of the thesis is to study the emission produced by these phenomena, in the range of X-rays to gamma-rays, whether to disentangle their individual contributions or to detect emission resulting from their interaction. The thesis intends to provide data to continue the study of the starburst-AGN connection, and new models to explain the production of gamma rays in other galaxies.
Part I focuses on the X-ray analysis of a local sample of LIRGs. The Great Observatories All-Sky LIRG survey (GOALS) is a project to study the brightest infrared galaxies at z < 0.1, in all possible wavelengths. In this part we analyze data for 63 LIRGs in the lower luminosity range of GOALS. We provide X-ray images, fluxes, luminosities and radial profiles for 84 individual galaxies, spanning a wide range of activity types and merger stages. We also provide information on AGN presence using X-ray and IR diagnostics, and compare the results to those derived for the brightest GOALS galaxies. The data provided in this part will help shine light into the importance of AGN presence in LIRGs, in the context of galaxy evolution.
Parts II and III focus on the interaction of AGN jets with stellar populations. When the jet of an AGN impacts a stellar wind, or a blob of material, a shock is formed in which particles can be accelerated up to relativistic energies. We estimate, for different scenarios, the dynamical evolution of the obstacles in the jet and gamma-ray emission generated by the accelerated particles. Part II focuses on the presence of whole populations of stars with high mass-loss rates interacting with the jet, whether because they are inside it, or because they expel layers of accumulated shocked material at the moment they penetrate it. Part III deals with single obstacles, in particular the remnant of a supernova explosion that takes place within the jet. In both parts II and III we include dynamical simulations that illustrate the process and how it affects the jet.
Part IV focuses on the interaction of AGN jets with the environment at large scales, in this case considering them as possible sources of reionization at z=6. We estimate the number of jetted sources at the epoch of reionization using rest-UV detections of AGN. We then correct the observed density of sources for effects of obscuration using X-ray data. Jets at high redshift interact strongly with the CMB, upscattering its photons up to ionizing wavelengths through IC, and possibly ionizing the ambient medium significantly.Esta tesis tiene como objetivo el estudio de fenómenos altamente energéticos en las regiones centrales de las galaxias activas. La formación intensa de estrellas se produce tras una fusión de galaxias, y este mismo fenómeno puede resultar en la acreción de material sobre el agujero negro supermasivo central (AGN). Incluso cuando el episodio de formación de estrellas ha terminado, este ha dado lugar a un bulbo galáctico; por lo que las densidades estelares en las zonas centrales de las galaxias son típicamente elevadas. Por lo tanto, es de esperar que las interacciones entre estrellas y AGN sean un fenómeno frecuente, que puede dar lugar a una gran cantidad de fenómenos interesantes. En particular, la tesis tiene como objetivo estudiar la emisión producida por estos fenómenos, en el rango de rayos X a rayos gamma, ya sea para distinguir las contribuciones individuales de cada uno o para estudiar la emisión generada en su interacción. La tesis pretende proveer datos para continuar el estudio de la relación entre formación estelar y actividad AGN, y nuevos modelos para explicar la producción de rayos gamma en otras galaxias. La primera parte de la tesis es un estudio en rayos X de galaxias lumínicas en el infrarojo. Se analiza una muestra local, proporcionando imágenes, flujos, luminosidades y perfiles radiales en rayos X de 84 galaxias individuales. También se proporciona información sobre la presencia de AGN en ellas, usando datos en rayos X e infrarojo. La parte central de la tesis se centra en el estudio de la interacción entre jets de AGN y estrellas, ya sea porque estas se encuentran dentro de él, porque le inyectan material al penetrarlo, o porque explotan como supernovas en su interior. Se estudia la evolución dinámica de estos fenómenos, y los rayos gamma producidos. La última parte estima la contribución de los jets de AGN a la reionización del universo, puesto que su interacción con los fotones del fondo cósmico de microondas puede resultar en radiación ionizante a través del mecanismo de Compton inverso.
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Ricci, Riccardo. "Study of bent monolithic active pixel sensors for the ALICE inner tracking system 3". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23514/.
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The ALICE experiment at CERN has planned an upgrade of the Inner Tracking System (ITS), named ITS3, for the LHC Long Shutdown 3, in 2025. The cornerstone of the upgrade is a new CMOS pixel sensor built in 65 nm technology and in bent-cylindrical configuration, replacing the inner layers of the existing detector, the ITS2. The ITS3 will reach much better tracking and vertexing performance, thanks to the improved spatial resolution and the much reduced material budget with respect to the previous Inner Tracking System.
The aim of this thesis is to report on the analysis of the data collected at beam tests on new ALPIDE chips (used for ITS2, based on Monolithic Active Pixel Sensor, MAPS) which have been bent in a cylindrical configuration as foreseen for the ITS3. This is the first bending proof of concept for a silicon detector.
In particular, data from beam test taken in 2020 have been studied through a data analysis framework that I have personally written to accomplish this task; the complexity of the data analysis is driven by the fact that each ALPIDE chip has a total of 1024x512 pixel MAPS and by the bent geometry of the sensor.
In this thesis, the promising performances obtained by studying the sensor total efficiency and spatial resolution in different experimental configurations will be presented and discussed.
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Ehrenhofer, Adrian y Thomas Wallmersperger. "Active hydrogel composite membranes for the analysis of cell size distributions". SPIE, 2019. https://tud.qucosa.de/id/qucosa%3A74237.
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Active membranes with switchable pores that are based on hydrogels can be used to measure the cell size distribution in blood samples. The system investigated in the present research is based on a polyethylene terephthalate (PET) membrane that is surface polymerized with poly (N-isopropyl acrylamide) (PNiPAAm) to form active pores of arbitrary geometry. The PET membrane provides the functionality of a backbone for mechanical rigidity, while the soft PNiPAAm hydrogel forms the active pores. Modeling and simulation of the active hydrogel behavior proved to adequately predict the opening and closing of the pores under application of an activating stimulus, e.g. temperature. The applied model is called Temperature-Expansion-Model and uses the analogy of thermal expansion to model the volume swelling of hydrogels. The Normalized Extended Temperature-Expansion-Model can englobe arbitrary hydrogels and large geometric displacements. Studies of pore opening - performed by using commercial finite element tools - show good agreement of the experimentally measured shape change of active pores. Based on these studies, the particulate fluid flow through the switchable pores is analyzed. Through application of a membrane process, i.e. a given variation of applied pressure and switching stimulus for the hydrogel, the size profile of the blocking particles can be measured directly using the flux difference under constant pressure. This allows the measurement of the cell size distribution in blood samples, e.g. to detect circulating tumor cells or anomalies in the distribution that hint to anemia.
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Bordikar, Maitrayee Ranade. "Analysis of Plasma Wave Irregularities Generated during Active Experiments in Near-Earth Space Environment". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23206.
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This work focuses on the analysis of plasma irregularities generated during two active space experiments: the injection of an artificial dust layer, and high-power radio waves. The objective of the "first experiment is to examine the effects of artificially created dust layers on the scatter of radars from plasma irregularities embedded in dusty plasma in space. This is an alternate approach for understanding the mechanisms of enhanced radar scatter from plasma irregularities embedded in Noctilucent Clouds and Polar Mesospheric Summer Echoes. The second experiment involves a transmission of high power electromagnetic waves into the ionospheric plasma from the ground, which can excite stimulated electromagnetic emissions offset from the transmitter frequency. These stimulated electromagnetic emissions provide diagnostic information of the ionosphere and thus can be used to investigate fundamental physical principles which govern the earth\'s ionosphere, so that present and future transmission technologies may take into account the complexities of the ionosphere. The interaction altitude of the artificial dust layer and high power radio waves is approximately 250 km and 160 km respectively, thus dealing with uniquely different regions of the ionosphere. Each experiment is discussed separately using theoretical, observational and advanced computational methodologies.
The study first investigates plasma turbulence associated with the creation of an artificial dust layer in the earth's ionosphere. Two scenarios are considered for plasma irregularity generation as dust is injected at an oblique angle across the geomagnetic field. The first is a shear-driven plasma instability due to inhomogeneities in the boundary layer between the injected charged dust layer and the background plasma. This begins to appear at very early times once the dust is released into the space plasma, which is of the order or less than the dust charging time period. The second mechanism is free streaming of the charged dust relative to the background plasma. This produces irregularities at times much longer than the dust charging period and also longer than the dust plasma period. Although both mechanisms are shown to produce turbulence in the lower hybrid frequency range, the resulting irregularities have important differences in their physical characteristics. A comparison between the processes is made to determine the consequences for upcoming observations. Both processes are shown to have the possibility of generating turbulence after the release of dust for the regimes of upcoming space experiments over a range of timescales.
This work also presents the first observations of unique narrowband emissions ordered near the Hydrogen ion (H+) gyro-frequency (fcH) in the Stimulated Electromagnetic Emission (SEE) spectrum when the transmitter is tuned near the second electron gyro-harmonic frequency (2fce), during ionospheric modification experiments. The frequency structuring of these newly discovered emission lines is quite unexpected since H+ is known to be a minor constituent in the interaction region which is near 160 km altitude. The spectral lines are typically shifted from the pump wave frequency by harmonics of a frequency about 10% less than fcH (" 800 Hz) and have a bandwidth of less than 50 Hz which is near the O+ gyro-frequency fcO. A theory is proposed to explain these emissions in terms of a Parametric Decay Instability (PDI) in a multi-ion species plasma due to possible proton precipitation associated with the disturbed conditions during the heating experiment. The observations can be explained by including several percent H+ ions into the background plasma. The implications are new possibilities for characterizing proton precipitation events during ionospheric heating experiments.Ph. D.
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Al-Saedi, Waleed Abood Baddai. "Optimal Control of Power Quality in Microgrids Using Particle Swarm Optimisation". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/611.
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Driven by environmental protection, economic factors, conservation of energy resources, and technical challenges, the microgrid has emerged as an innovative small-scale power generation network. Microgrids consist of a cluster of Distributed Generation units that encompass a portion of an electric power distribution system and may rely on different energy sources. Functionally, the microgrid is required to provide adequate levels and quality of power to meet load demands. The issue of power quality is significant as it directly affects the characteristics of the microgrid’s operation. This problem can be defined as an occurrence of short to long periods of inadequate or unstable power outputs by the microgrid. In a stand-alone operation mode, the system voltage and frequency must be established by the microgrid, otherwise the system will collapse due to the variety in the microgrid component characteristics. The harmonic distortion of the output power waveforms is also a serious problem that often occurs because of the high speed operation of the converter switches. The long transient period is a critical issue that is usually caused by changing the operation mode or the load demand. Power sharing among the Distributed Generation units is also an important matter for sharing the load appropriately, particularly given that some renewable energy resources are not available continuously. In a utility connected microgrid, the reliable power quality mainly depends on the regulation of both active and reactive power, because the microgrid’s behaviour is mostly dominated by the bulk power system. Therefore, an optimal power control strategy is proposed in this thesis to improve the quality of the power supply in a microgrid scenario. This controller comprises an inner current control loop and an outer power control loop based on a synchronous reference frame and conventional PI regulators. The power control loop can operate in two modes: voltage-frequency power control mode and active-reactive power control mode. Particle Swarm Optimisation is an intelligent searching algorithm that is applied here for real-time self-tuning of the power control parameters. The voltage-frequency power controller is proposed for an inverter-based Distributed Generation unit in an autonomous operation mode. The results show satisfactory system voltage and frequency, high dynamic response, and an acceptable harmonic distortion level. The active-reactive power controller is adopted for an inverter-based Distributed Generation unit in a utility operation mode. This controller provides excellent regulation of the active and reactive power, in particular when load power has to be shared equally between the microgrid and utility. The voltage-frequency and active-reactive power control modes are used for a microgrid configured from two DG units in an autonomous operation mode. The proposed control strategy maintains the system voltage and frequency within acceptable limits, and injects sustained output power from one DG unit during a load change. The reliability of the system’s operation is investigated through developing a small-signal dynamic model for the microgrid. The results prove that the system was stable for the given operating point and under the proposed power controller. Consequently, this research reveals that the microgrid can successfully operate as a controllable power generation unit to support the utility, thus reducing the dependency on the bulk power system and increasing the market penetration of the micro-sources.
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Martinez, Pujol Oriol. "Template tracking of articulated objects using active contours". Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/373919.
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En aquesta dissertació es fusionen dos dels temes tradicionals de la Visió per Computador: la segmentació i el seguiment d'objectes. Per a la segmentació s'utilitzen mètodes basats en "Active Contours (AC)" i per al seguiment mètodes basats en "templates" o patrons. El nostre objectiu és combinar-los per tal de crear mètodes robustos i eficients a l'hora de segmentar i seguir objectes articulats o deformables. Al capítol 1 es revisa el marc teòric dels AC i s'aplica en la segmentació de cossos i amenaces (com explosius o pistoles) que estan amagades darrera la roba en imatges MilliMeter-Waves (MMW). Al capítol 2 es revisen dos dels marcs principals de seguiment de patrons: el flux òptic de Lucas-Kanade i els filtres de partícules, i es combinen amb la segmentació mitjançant AC per tal de crear un mètode robust i eficient capaç de seguir objectes articulats o deformables sense informació a priori. Finalment, al capítol 3 es donen les claus per introduir informació a priori d'una manera robusta i eficient dins del marc del seguiment de patrons utilitzant AC.In this dissertation we fuse two of the traditional topics in Computer Vision: object segmentation and tracking. For segmentation we use the Active Contours (AC) framework and for tracking we use the Template Tracking (TT) scheme. Our aim is to combine them to create efficient and robust methods to segment and track articulated or deformable objects. In Chapter 1, we review the AC framework and we apply it over MilliMeter-Waves (MMW) images to segment bodies and concealed threats (such as explosives or guns) behind their wearing clothes. In Chapter 2 we review two of the main trends of TT methods: Lucas-Kanade optical flow and particle filters. Moreover, we combine them with an AC method to create a robust tracker for articulated or deformable objects without using prior shape information. Finally, in Chapter 3 we give the clues of how to efficiently introduce shape priors into the TT framework using AC methods.
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Hendeby, Gustaf. "Development and Evaluation of an Active Radio Frequency Seeker Model for a Missile with Data-Link Capability". Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1473.
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To develop and maintain a modern combat aircraft it is important to have simple, yet accurate, threat models to support early stages of functional development. Therefore this thesis develops and evaluates a model of an active radio frequency (RF) seeker for a missile with data-link capability. The highly parametrized MATLAB-model consists of a pulse level radar model, a tracker using either interacting multiple models (IMM) or particle filters, and a guidance law.
Monte Carlo simulations with the missile model indicate that, under the given conditions, the missile performs well (hit rate>99%) with both filter types, and the model is relatively insensitive to lost data-link transmissions. It is therefore under normal conditions not worthwhile to use the more computer intense particle filter today, however when the data-link degrades the particle filter performs considerably better than the IMM filter. Analysis also indicate that the measurements generated by the radar model are neither independent, white nor Gaussian. This contradicts the assumptions made in this, and many other radar applications. However, the performance of the model suggests that the assumptions are acceptable approximations of actual conditions, but further studies within this are recommended to verify this.
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Gudi, Nikhil. "A Simulation Platform to Demonstrate Active Demand-Side Management by Incorporating Heuristic Optimization for Home Energy Management". University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279314597.
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Kumar, Anil. "Estimation and Mapping of Ship Air Wakes using RC Helicopters as a Sensing Platform". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82910.
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This dissertation explores the applicability of RC helicopters as a tool to map wind conditions. This dissertation presents the construction of a robust instrumentation system capable of wireless in-situ measurement and mapping of ship airwake. The presented instrumentation system utilizes an RC helicopter as a carrier platform and uses the helicopter's dynamics for spatial 3D mapping of wind turbulence. The system was tested with a YP676 naval training craft to map ship airwake generated in controlled heading wind conditions. Novel system modeling techniques were developed to estimate the dynamics of an instrumented RC helicopter, in conjunction with onboard sensing, to estimate spatially varying (local) wind conditions. The primary problem addressed in this dissertation is the reliable estimation and separation of pilot induced dynamics from the system measurements, followed by the use of the dynamics residuals/discrepancies to map the wind conditions.
This dissertation presents two different modelling approaches to quantify ship airwake using helicopter dynamics. The helicopter systems were characterized using both machine learning and analytical aerodynamic modelling approaches. In the machine learning based approaches, neural networks, along with other models, were trained then assessed in their capability to model dynamics from pilot inputs and other measured helicopter states. The dynamics arising from the wind conditions were fused with the positioning estimates of the helicopter to generate ship airwake maps which were compared against CFD generated airwake patterns. In the analytical modelling based approach, the dynamic response of an RC helicopter to a spatially varying parameterized wind field was modeled using a 30-state nonlinear ordinary differential equation-based dynamic system, while capturing essential elements of the helicopter dynamics. The airwake patterns obtained from both types of approach were compared against anemometrically produced wind maps of turbulent wind conditions artificially generated in a controlled indoor environment.
Novel hardware architecture was developed to acquire data critical for the operation and calibration of the proposed system. The mechatronics design of three prototypes of the proposed system were presented and performance evaluated using experimental testing with a modified YP676 naval training vessel in the Chesapeake Bay area. In closing, qualitative analysis of these systems along with potential applications and improvements are discussed to conclude this dissertation.Ph. D.
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Skoglund, Oskar. "Evaluation of bark material and granulated active carbon for treatment of perfluoroalkyl substances (PFASs) in wastewater". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-317453.
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Per- and polyfluoroalkyl substances (PFASs) are a group of artificial chemicals which have been used in a wide area of applications such as surface protection agents in cloths and different industrial applications. It has been found that PFASs are potentially toxic and are frequently found in the environment due to their persistent and mobile properties. Effluents from wastewater treatment plants (WWTPs) have been identified as an important point source of PFASs. Bark, by-product from the paper and wood industry, is a low-cost adsorbent and has the potential to be used as a filter material for PFASs in WWTPs. In this study, the removal of PFASs in wastewater has been investigated using granulated active carbon (GAC) (n = 2) and bark (n = 2) in a pilot scale experiment at Kungsängsverket, Uppsala over a period of five weeks. The specific objects included: i) investigate the influence of flow-rate (10, 30 40 and 60 Ld-1 ) on the removal efficiency of PFASs in the GAC and bark filters, ii) investigate the influence of particle size of bark on the removal efficiency of PFASs and iii) establish what circumstances that potentially promotes removal of PFASs in GAC and bark filters. The results showed that GAC was the most effective method compared to bark, with a reduction of 73-93%, with increasing efficiency under low flow (10-30 L d-1 ) conditions. The removal efficiency of bark was 45% with a particle size of 2-5 mm and under low flow conditions (10-30 L d-1 ), while under high flow conditions (60 L d-1 ) with the same particle size the removal of PFASs was not efficient, instead the total PFAS concentration increased with 40%. In contrast, bark with a particle size of 5-7 mm proved to be not efficient in removing PFASs (removal efficiency = 0%). In general, the removal efficiency increased with smaller particle size of the adsorbent and lower flow rate. The results indicate that bark may be a low-cost alternative in reducing PFASs from wastewater, under certain conditions.Per- och polyfluroalkyla ämnen (PFAS) är en familj av artificiella fluorerade organiska föreningar som har använts sedan 1950-talet i en rad olika applikationer, såsom impregnering i kläder. Studier har visat att PFAS är potentiellt toxiska och att de förekommer globalt på grund av deras persistenta och mobila egenskaper. Spillvatten från avloppsreningsverk etablerats som en betydande källa för PFAS. Bark, vilket är en biprodukt från pappers- och träindustrin, är ett poröst material vilket möjligen kan användas som adsorbent av PFAS. Denna studie har jämfört effektiviteten hos granulerat aktivt kol (GAC) och bark för att minska PFAS i avloppsvatten. Experimentet var utformat som ett småskaligt kolonn-experiment vid Kungsängsängsverket, Uppsala, och pågick under en fem veckors period. Frågeställningen var att i) studera vilka effekter flödes-hastigheten (10, 30, 40 och 60 L d-1 ) har på reduktionen av PFAS hos GAC och barkfiltren, ii) studera vilka effekter partikelstorleken hos bark har på reduktion av PFAS och iii) redogöra vilka förhållanden som potentiellt gynnar reduktionen av PFAS i GAC och bark filtren. Resultaten visade att GAC var det mest effektiva av de två materialen, med en total reduktion på 73- 93% av PFAS, med ökande effektivitet under låga flödesförhållanden (10-30 L d-1 ). Bark minskade den totala mängden av PFAS med 45% då partikelstorleken var 2-5 mm och under låga flödesförhållanden (10-30 L d-1 ) medan bark med samma partikelstorlek under ökade flödesförhållanden (60 L d-1 ) visade en ökning på 40% av PFAS i det utgående vattnet. Bark med en partikelstorlek på 5-7 mm visade ingen reduktion av PFAS. Generellt visade resultaten att reduktionen av PFAS ökar under låga flödesförhållanden och minskad partikelstorlek. Resultaten visade att bark kan vara ett alternativt material för att minska PFAS i avloppsvatten förutsatt att gynnsamma förhållanden upprätthålls.
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Hörbe, Mario Robert [Verfasser], Julia [Gutachter] Tjus y Garret [Gutachter] Cotter. "High-energy particle emission from plasmoids in jets of active galactic nuclei / Mario Robert Hörbe ; Gutachter: Julia Tjus, Garret Cotter ; Fakultät für Physik und Astronomie". Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1233484176/34.
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Santhanakrishnan, Arvind. "CHARACTERIZATION AND FLOW PHYSICS OF PLASMA SYNTHETIC JET ACTUATORS". UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/545.
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Plasma synthetic jet actuators are investigated experimentally, in which the geometrical design of single dielectric barrier discharge (SDBD) plasma actuators is modified to produce zero-mass flux jets similar to those created by mechanical devices. The SDBD plasma actuator consists of two rectangular electrodes oriented asymmetrically and separated by a layer of dielectric material. Under an input of high voltage, high frequency AC or pulsed DC, a region of plasma is created in the interfacial air gap on account of electrical breakdown of the ambient air. A coupling between the electric field in the plasma and the neutral air near the actuator is introduced, such that the latter experiences a net force which results in a horizontal wall jet. This effect of the actuator has been demonstrated to be useful in mitigating boundary layer separation in aerodynamic flows. To increase the impact that a plasma actuator may have on the flow field, this research investigates the development and characterization of a novel flow control device, the plasma synthetic jet actuator, which tailors the residual air in the form of a vertical jet resembling conventional continuous and synthetic jets. This jet can be either three dimensional using annular electrode arrays, or nearly two dimensional using two rectangular strip exposed electrodes and one embedded electrode. Detailed measurements on the isolated plasma synthetic jet reveal that pulsed operation of the actuator results in the formation of multiple counterrotating vortical structures in the flow field. The output jet velocity and momentum are found to be higher for unsteady pulsing as compared to steady operation. In the case of flow over a flat plate, the actuator is observed to create a localized interaction region within which the baseline flow direction and boundary layer characteristics are modified. The efficiency of the actuator in coupling momentum to the neutral air is found to be related to the plasma morphology, pulsing frequency, actuator dimension, and input power. An analytical scaling model is proposed to describe the effects of varying the above variables on the output jet characteristics and actuator efficiency, and the experimental data is used for model validation.
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Gachelin, Jeremie. "Rhéologie et comportement de suspensions de Escherichia Coli en milieux confinés". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066406/document.
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Lorsque des particules actives, des particules pouvant se mouvoir par elles-mêmes, sont mises en suspension dans un fluide, celles-ci peuvent avoir un comportement collectif. Dans ce document, nous présentons des travaux expérimentaux utilisant des Escherichia Coli, une particule biologique, des techniques microfluidiques, ainsi que des simulations numériques. Ceux-ci nous ont permis de caractériser les comportements collectifs de ces nageurs, leur modification en présence d'un cisaillement extérieur ainsi que l'impact de ces comportements microscopiques sur sa viscosité. Nous avons ainsi mis au jour le caractère progressif de l'apparition des mouvements collectifs avec la concentration, l'existence d'un taux de cisaillement critique commun pour les comportements individuels et collectifs des nageurs, ainsi qu'une rhéologie non-newtonienne de ces suspensionsIf we put active particles, ie. motile particles, in suspension into a _uid, collective behaviors can occur. In this document, we present experimental works using Escherichia Coli, a biological particle, micro_uidic devices, and numerical simulations. By these ways, we caracterized these swimmers, their collective motions, the impact of an external shear on their behavior, and rheological behavior of this kind of suspensions. We show that the typical size of these collective motions increases smoothly with the volume fraction, and that a critical shear rate exist and is the same for individual and collective motion under shear. We also show for that bacterial suspensions have a non-newtonian viscosity and describe their rheological behavior
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Ozkaya, Bora. "Application, Comparison, And Improvement Of Known Received Signal Strength Indication (rssi) Based Indoor Localization And Tracking Methods Using Active Rfid Devices". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613014/index.pdf.
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Localization and tracking objects or people in real time in indoor environments have
gained great importance. In the literature and market, many different location
estimation and tracking solutions using received signal strength indication (RSSI) are
proposed. But there is a lack of information on the comparison of these techniques
revealing their weak and strong behaviors over each other. There is a need for the
answer to the question&ldquo
which localization/tracking method is more suitable to my system needs?&rdquo
. So, one purpose of this thesis is to seek the answer to this question. Hence, we investigated the behaviors of commonly proposed localization methods, mainly nearest neighbors based methods, grid based Bayesian filtering and particle filtering methods by both simulation and experimental work on the same test bed. The other purpose of this thesis is to propose an improved method that is simple to install, cost effective and moderately accurate to use for real life applications. Our proposed method uses an improved type of sampling importance resampling (SIR) filter incorporating automatic calibration of propagation model parameters of logv distance path loss model and RSSI measurement noise by using reference tags. The proposed method also uses an RSSI smoothing algorithm exploiting the RSSI readings from the reference tags. We used an active RFID system composed of 3 readers, 1 target tag and 4 reference tags in a home environment of two rooms with a total area of 36 m²
. The proposed method yielded 1.25 m estimation RMS error for tracking a mobile target.
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Ngunjiri, John Muthumbi. "Influenza virus noninfectious biologically active particle subpopulations| Detection, quantification, genetic complexity, function and their novel use as an in vitro screen for self-adjuvating live-attenuated influenza vaccines". Thesis, University of Connecticut, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3569980.
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This work investigates the functional heterogeneity of influenza virus quasispecies through quantitative analysis of cellular responses to the entry of noninfectious biologically active particles, the effect of reassortment of gene segments on the generation and function of these particle subpopulations, and the potential of these subpopulations as in vitro correlates of in vivo effectiveness of live-attenuated influenza vaccines (LAIVs).
For the first time, the clonogenic assay was used to show that populations of most influenza A viruses contained cell-killing particles in excess of infectious particles when tested in the same host cell. Thus, a new class of influenza virus particles was revealed – noninfectious cell-killing particles which required the synthesis of a specific viral polymerase subunit to kill cells and the expression of NS1 protein to temporally delay apoptosis/cell-killing.
The noninfectious cell-killing particles were clearly distinguished from the well known defective-interfering particles by differences in their numbers in standard influenza virus populations, their temporal appearance and quantity during serial high multiplicity propagation in mammalian and chicken cells, an inability of defective-interfering particles to kill cells or interfere with the cell-killing capacity of noninfectious cell-killing particles, genetic requirements (a small DI RNA ∼350 nt and a large RNA ∼2,300 nt for defective-interfering and noninfectious cell-killing particle activities, respectively), and the extracellular T½ at 40.5 °C (∼40h and ∼85h for noninfectious cell-killing particles and defective-interfering particles, respectively).
Specific exchange of the NS gene segment from lethal A/HK/156/97 (H5N1) (NS1: E92, or E92D) virus for the cognate NS gene segment of A/PR/834 (H1N1) (NS1: D92) virus caused de novo generation of large defective-interfering particle subpopulations and >10-fold enhancement of interferon-inducing particle efficiency. These changes were attributed to dysfunction of the H5N1 virus NS1 gene.
Populations of two effective LAIVs (Vac+) in chickens were characterized by high defective-interfering to interferon-inducing particle ratios and induction of large amounts of interferon in chicken cells. Interferon is an antiviral cytokine that acts as a potent natural adjuvant of adaptive immune responses in chickens. Populations of two ineffective LAIVs (Vac -) in chickens had lower defective-interfering to interferon-inducing particle ratios and induced less interferon. Unexpectedly, these phenotypes were reversed in mammalian cells. Populations of Vac- (in chickens) LAIV candidates were excellent interferon inducers with high defective-interfering to interferon-inducing particle ratios in mammalian cells. In contrast, populations of Vac+ (in chickens) LAIV candidates were poor interferon inducers with low defective-interfering to interferon-inducing particle ratios in mammalian cells. As predicted by the in vitro screen, the Vac phenotypes were reversed in vivo (in mice) relative to chickens.
Overall, this study shows that the majority of noninfectious particles of influenza virus are biologically active, reassortment can change the subpopulation make of influenza virus, and a high defective-interfering to interferon-inducing particle ratio is a strong in vitro correlate of the effectiveness of self-adjuvanting LAIVs. Taken together, these attributes of an influenza virus population represent a novel ensemble of in vitro parameters that may be used to distinguish between Vac+ and Vac - LAIV candidates.
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Bau, Sébastien. "Étude des moyens de la surface des aérosols ultrafins pour l'évaluation de l'exposition professionnelle". Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL095N/document.
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Ce travail s'inscrit dans le cadre de l'amélioration de la connaissance sur la mesure de la surface des aérosols ultrafins. En effet, l'essor des nanotechnologies peut être à l'origine de situations d'exposition professionnelle aux particules nanostructurées dispersées dans l'air, ce qui soulève une problématique nouvelle de prévention. Si à ce jour aucun des trois indicateurs (masse, surface, nombre) ne fait l'objet d'un consensus, il semble que le paramètre de surface des particules permet une bonne corrélation avec les effets biologiques observés lorsqu'elles sont inhalées. Un travail théorique original a donc été mené afin de positionner le paramètre de surface vis-à-vis d'autres grandeurs caractéristiques des aérosols. En vue de caractériser des méthodes de mesure de la surface des aérosols nanostructurés, le banc d'essais CAIMAN (CAractérisation des Instruments de Mesure des Aérosols Nanostructurés) a été dimensionné et réalisé. Celui-ci permet la production d'aérosols nanostructurés de propriétés variables et maîtrisées (taille, concentration, nature chimique, morphologie, état de charge), offrant une très bonne stabilité dans le temps. Les aérosols générés en laboratoire ont été utilisés en vue d'évaluer expérimentalement la réponse des instruments de mesure étudiés (NSAM & AeroTrak 9000 TSI, LQ1-DC Matter Engineering). Les fonctions de réponse expérimentales établies sur des aérosols monodispersés présentent un bon accord avec les courbes théoriques, dans une large gamme d'étude de 15 à 520 nm. Par ailleurs, des hypothèses ont été avancées en vue d'expliquer les écarts raisonnables observés lors des mesures effectuées sur des aérosols polydispersésThis work aims at improving knowledge on ultrafine aerosols surface-area measurement. Indeed, the development of nanotechnologies may lead to occupational exposure to airborne nanostructured particles, which involves a new prevention issue. There is currently no consensus concerning what parameter (mass, surface-area, number) should be measured. However, surface-area could be a relevant metric, since it leads to a satisfying correlation with biological effects when nanostructured particles are inhaled. Hence, an original theoretical work was performed to position the parameter of surface-area in relation to other aerosol characteristics. To investigate measurement techniques of nanostructured aerosols surface-area, the experimental facility CAIMAN (ChAracterization of Instruments for the Measurement of Aerosols of Nanoparticles) was designed and built. Within CAIMAN, it is possible to produce nanostructured aerosols with varying and controlled properties (size, concentration, chemical nature, morphology, state-of-charge), stable and reproducible in time. The generated aerosols were used to experimentally characterize the response of the instruments in study (NSAM & AeroTrak 9000 TSI, LQ1-DC Matter Engineering). The response functions measured with monodisperse aerosols show a good agreement with the corresponding theoretical curves in a large size range, from 15 to 520 nm. Furthermore, hypotheses have been formulated to explain the reasonable biases observed when measuring polydisperse aerosols
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Glawion, Dorit [Verfasser], Karl [Gutachter] Mannheim, Matthias [Gutachter] Kadler y Jan [Gutachter] Conrad. "Contemporaneous Multi-Wavelength Observations of the Gamma-Ray Emitting Active Galaxy IC 310 - New Clues on Particle Acceleration in Extragalactic Jets / Dorit Glawion. Gutachter: Karl Mannheim ; Matthias Kadler ; Jan Conrad". Würzburg : Universität Würzburg, 2015. http://d-nb.info/1111886997/34.
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Lepro, Valentino [Verfasser], Carsten [Akademischer Betreuer] Beta, Stefan [Akademischer Betreuer] Klumpp, Carsten [Gutachter] Beta, Stefan [Gutachter] Klumpp y Klaus [Gutachter] Kroy. "Experimental and theoretical study on amoeboid cell-cargo active motion : a physical analysis of cell-mediated particle transport / Valentino Lepro ; Gutachter: Carsten Beta, Stefan Klumpp, Klaus Kroy ; Carsten Beta, Stefan Klumpp". Potsdam : Universität Potsdam, 2021. http://d-nb.info/1228431574/34.
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Lee, Jehoon. "Statistical and geometric methods for visual tracking with occlusion handling and target reacquisition". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43582.
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Computer vision is the science that studies how machines understand scenes and automatically make decisions based on meaningful information extracted from an image or multi-dimensional data of the scene, like human vision. One common and well-studied field of computer vision is visual tracking. It is challenging and active research area in the computer vision community. Visual tracking is the task of continuously estimating the pose of an object of interest from the background in consecutive frames of an image sequence. It is a ubiquitous task and a fundamental technology of computer vision that provides low-level information used for high-level applications such as visual navigation, human-computer interaction, and surveillance system.
The focus of the research in this thesis is visual tracking and its applications. More specifically, the object of this research is to design a reliable tracking algorithm for a deformable object that is robust to clutter and capable of occlusion handling and target reacquisition in realistic tracking scenarios by using statistical and geometric methods. To this end, the approaches developed in this thesis make extensive use of region-based active contours and particle filters in a variational framework. In addition, to deal with occlusions and target reacquisition problems, we exploit the benefits of coupling 2D and 3D information of an image and an object.
In this thesis, first, we present an approach for tracking a moving object based on 3D range information in stereoscopic temporal imagery by combining particle filtering and geometric active contours. Range information is weighted by the proposed Gaussian weighting scheme to improve segmentation achieved by active contours. In addition, this work present an on-line shape learning method based on principal component analysis to reacquire track of an object in the event that it disappears from the field of view and reappears later. Second, we propose an approach to jointly track a rigid object in a 2D image sequence and to estimate its pose in 3D space. In this work, we take advantage of knowledge of a 3D model of an object and we employ particle filtering to generate and propagate the translation and rotation parameters in a decoupled manner. Moreover, to continuously track the object in the presence of occlusions, we propose an occlusion detection and handling scheme based on the control of the degree of dependence between predictions and measurements of the system. Third, we introduce the fast level-set based algorithm applicable to real-time applications. In this algorithm, a contour-based tracker is improved in terms of computational complexity and the tracker performs real-time curve evolution for detecting multiple windows. Lastly, we deal with rapid human motion in context of object segmentation and visual tracking. Specifically, we introduce a model-free and marker-less approach for human body tracking based on a dynamic color model and geometric information of a human body from a monocular video sequence. The contributions of this thesis are summarized as follows:
1. Reliable algorithm to track deformable objects in a sequence consisting of 3D range data by combining particle filtering and statistics-based active contour models.
2. Effective handling scheme based on object's 2D shape information for the challenging situations in which the tracked object is completely gone from the image domain during tracking.
3. Robust 2D-3D pose tracking algorithm using a 3D shape prior and particle filters on SE(3).
4. Occlusion handling scheme based on the degree of trust between predictions and measurements of the tracking system, which is controlled in an online fashion.
5. Fast level set based active contour models applicable to real-time object detection.
6. Model-free and marker-less approach for tracking of rapid human motion based on a dynamic color model and geometric information of a human body.
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Angeletti, Andrea. "Collective dynamics of active particles". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16772/.
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Il nostro scopo è lo studio e il confronto della dinamica di particelle passive e attive in un fluido. Vengono inoltre introdotti i modelli matematici che permettono di simulare il loro comportamento. Sono studiate le propietà e la soluzione numerica dell'equazione di Langevin nella sua approsimazione in regime 'overdamped'. Mostriamo come lo spostamento quadratico medio delle particelle passive sia diffusivo, i.e. lineare nel tempo, e proporzionale al coefficiente di diffusione lineare, mentre quello di particelle attive quadratico per un tempo minore dell'inverso del coefficiente di diffusione rotazionale e diffusivo per un tempo maggiore. Con la presenza di una parete repulsiva e osservando la distribuzione di probabilità della posizione delle particelle, notiamo come quelle attive tendano ad accumularsi su di essa. Infine osserviamo che sotto l'azione di un potenziale repulsivo particelle attive tendono a formare agglomerati.
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Wang, Xiaolu. "Janus Colloids Surfing at the Surface of Water". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS272/document.
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Considérant une particule isolée, la différence principale entre un colloïde actif et un colloïde passif réside dans le temps de persistance du régime balistique. La transition du régime balistique vers le régime diffusif est déterminée dans les deux cas par des coefficients de friction ou de manière équivalente par des coefficients de diffusion. Le mouvement d’une particule colloïdale passive micrométrique est diffusif lorsqu’il est observé sur des intervalles de temps d’au moins une microseconde, suffisamment longs pour que la direction de la quantité de mouvement soit rendue aléatoire par des collisions avec les molécules de solvant. A l’échelle macroscopique ces collisions se traduisent par un coefficient de friction de translation. Pour une particule colloïdale active, un mouvement diffusif est observé pour des intervalles de temps de plusieurs secondes, suffisamment longs pour que la direction d’auto-propulsion soit rendue aléatoire par la diffusion rotationnelle de la particule.Dans cette thèse, nous étudions le mouvement d’une particule colloïdale active déposée à la surface de l’eau. Des particules Janus aux propriétés catalytiques ont été préparées par dépôt de platine métal à la surface de particules de silice. La profondeur d’immersion des particules ainsi que leur orientation par rapport à la surface de l’eau ont été caractérisées et discutées en tenant compte des propriétés de mouillage non-uniformes de la surface des particules Janus. Le mouvement de particules isolées en présence de quantités variables d’eau oxygénée utilisée comme source d’énergie, a été enregistré par vidéo-microscopie optique et les trajectoires analysées en termes de déplacement carré moyen et de fonction d’auto-corrélation des vitesses. L’observation de deux types de trajectoires, rectilignes et circulaires, révèle la force effective ainsi que le couple induit par la décomposition catalytique de l’eau oxygénée à la surface de la particule Janus. Le résultat principal de ce travail est que le mouvement des particules actives confinées à l’interface persiste plus longtemps dans le régime balistique que celui de particules actives totalement immergées en solution. Ceci est dû au confinement qui réduit le nombre de degrés de liberté de rotation mais aussi aux conditions de mouillage partiel qui font apparaître des contributions supplémentaires à la friction de rotationAt the single-particle level, the main difference between active colloids and passive ones is the time scale over which the motion crosses over from ballistic to diffusive regime. In both cases, friction coefficients or equivalently diffusion coefficients determine this time scale. For instance, the motion of a passive colloid of 1m radius is diffusive when observed over lag times longer than a microsecond, once the direction of its momentum has been randomized by collisions with solvent molecules. At the macroscopic scale these collisions are accounted for by the translational friction coefficient. For an active colloid the effective diffusive behavior observed over lag times larger than few seconds results from the randomization of the direction of self-propulsion by rotational diffusion. In this thesis we investigated the motion of an active Janus colloid trapped at air-water interface. Spherical catalytic Janus colloids have been prepared through the deposition of platinum metal at the surface of silica particles. Immersion depth of the Janus colloid as well as their orientation with respect to the water surface, has been characterized and interpreted in terms of the non-uniform wetting properties of the Janus particles. The motion of the active Janus colloids in the presence of various concentration of hydrogen peroxide H2O2 as fuel was characterized by video microscopy and the trajectories analyzed through the mean square displacement and the velocity autocorrelation function. The types of trajectories, directional and circular ones that we observed in our experiments, revealed the effective force and torque induced by the catalytic decomposition of H2O2. At the water surface, active colloids perform more persistent directional motions as compared to the motions performed in the bulk. This has been interpreted as due to the loss of degrees of freedom resulting from the confinement at interface and also to the partial wetting conditions that possibly bring new contributions to the rotational friction at interface
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Benton, Stuart Ira. "Capitalizing on Convective Instabilities in a Streamwise Vortex-Wall Interaction". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437664298.
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Katuri, Jaideep. "Guiding active particles through surface interactions". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663989.
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Living organisms and systems are continually converting energy, either internally stored or transduced from their surroundings, into motion. This activity and the resulting self-propulsion constantly push these biological systems out of thermal equilibrium. A number of exotic phenomenon result from the intrinsic non-equilibrium nature of these living systems, that are not accessible in a system at thermal equilibrium. In recent years, these ubiquitous non-equilibrium systems have come to be classified as active matter. Active matter, by definition, refers to systems composed of active units, each capable of converting ambient or stored energy into systematic movement. Examples range from the sub-micrometer scale, with microtubules associated with motor proteins in the cytoplasm, to the micrometer length scales of swimming bacteria, and the meter-length scales of greater familiarity, such as that of fish and birds.
There are two common themes that run through all these active matter systems. The first is the emergence of correlated collective phenomenon through particle-particle interactions as exemplified in flocking of birds, swarming of bacteria and crystallization of self-propelled particles. And the second is the ability of the active units to interact with their surroundings through self-propulsion. Common examples of this include chemotaxis and rheotaxis, observed in many biological systems. In this thesis, I have focussed on studying the ability of artificial active matter systems to respond to their local environment.
As a model active matter system, we use colloidal active particles, that propel due to self-diffusiophoresis. These particles coated with two different materials on each half are referred to as Janus particles. In a solution of H2O2, one of the sides has catalytic properties (Pt), while the other half remains inert (SiO2). This creates a concentration gradient of the reaction product along the surface of the particle and induces a phoretic slip, which propels the particle. We study the dynamics of these self-phoretic particles close to solid surfaces. The particles interact with their surroundings via hydrodynamic and phoretic effects and we observe that when confined closed to a surface, a strong alignment interaction comes into play. This effect can be used to guide micron sized active particles along predetermined pathways. We then exploit this alignment interaction to design micropatterned ratchets capable of generating a strong directional flow of active particles. A different geometry of the same system can also be used to accumulate active particles in confined areas. Finally, we study the influence of an applied external shear flow on the dynamics of active particles near surfaces. We find that a strong directional response emerges for the active particles in the direction perpendicular to the flow direction leading to the cross-stream migration of active particles. This response is dependent on the applied shear flow and the propulsion velocity of the particle, potentially opening up a possibility to sort particles of different activities based on their response to shear flows. Overall, our results indicate that active particles can have a strong directional response in certain environments allowing us to engineer ways of guiding them.Los organismos y sistemas vivos convierten energía almacenada internamente o derivada de sus alrededores en movimiento de forma continua. Esta actividad puede causar una constante auto-propulsión que lleva a estos sistemas a un estado fuera de equilibrio térmico. Gracias a esto, aparecen un gran número de fenómenos exóticos que no son accesibles para un sistema que se encuentra en equilibrio térmico. En los últimos años se ha clasificado a estos sistemas de no equilibro como “material activa”. La materia activa, por definición, incluye los sistemas compuestos de unidades activas, cada una de ellas capaz de convertir la energía almacenada o del entorno en movimiento sistemático. Existen varios ejemplos que van desde la escala sub-micrométrica, donde podemos encontrar a los microtúbulos asociados a proteínas motoras en el citoplasma, a las grandes escalas, donde se encuentran sistemas más familiares como peces o pájaros, pasando por la escala micrométrica, donde nadan las bacterias. Podemos diferenciar dos temas principales que se manifiestan en todos estos sistemas de materia activa. El primero es la aparición de fenómenos colectivos correlacionados a través de interacciones partícula-partícula, como ocurre en bandadas de pájaros, enjambres bacterianos y la cristalización de partículas auto-propulsadas. El segundo es la capacidad de estas unidades activas de interaccionar con sus alrededores a través del fenómeno de la auto-propulsión, por ejemplo, a través de quimiotaxia o reotaxia, como se puede observar en muchos sistemas biológicos y que ya han sido reportados en varios estudios. En esta tesis, me he enfocado en el estudio de este último tema principal: la interacción de partículas activas con su entorno local. Como modelo de sistema de materia activa, usamos partículas activas coloidales que se propulsan gracias al fenómeno de auto-difusioforesis. Estas partículas están recubiertas por dos materiales diferentes en cada una de sus caras, y son comúnmente llamadas “partículas Janus”. Una de sus caras está recubierta con Pt, material que cataliza la descomposición de H2O2, mientras que la otra cara está recubierta de un material inerte (SiO2). En una solución de H2O2, la reacción que ocurre en la parte catalítica produce un gradiente de concentración de producto a lo largo de la superficie de la partícula e induce un deslizamiento forético que la propulsa. En esta tesis se ha estudiado la dinámica de estas partículas "autoforéticas" cerca de superficies sólidas. De manera natural, las partículas interaccionan con su alrededor debido a los efectos foréticos e hidrodinámicos. Cuando estas partículas se hayan confinadas cerca de una superficie, observamos que se origina en ellas una fuerte interacción de alineamiento. A partir de ello, consideramos interesante diseñar ratchets micro estampados capaces de generar un flujo direccional de partículas activas. Por otra parte, estudiamos la influencia de aplicar un flujo de cizalla externo en la dinámica de las partículas activas cerca de superficies. A consecuencia del flujo externo, encontramos que en el sistema emerge una respuesta fuertemente direccional para las partículas activas en la dirección perpendicular al flujo provocando una migración "cross-stream" de partículas activas.
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Bechinger, Clemens. "Active Brownian motion of asymmetric particles". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179545.
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Bechinger, Clemens. "Active Brownian motion of asymmetric particles". Diffusion fundamentals 20 (2013) 16, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13540.
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De, Franco Andrea. "Development of a camera for Tera-electron Volt gamma-ray astronomy". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:bfa00ea0-3be1-455c-9f82-3429e4bef0da.
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In this thesis I describe the development of a compact camera for ground-based multi TeV gamma-ray astronomy, using the Imaging Atmospheric Cherenkov Telescope (IACT) technique. The camera is based on multi-anode photomultipliers (MAPM) and is designed for use on the Gamma Cherenkov Telescope (GCT), which is proposed to be part of the Small Size Telescope (SST) array of the Cherenkov Telescope Array (CTA). GCT achieves high performance with a compact and cost efficient design via a Schwarzschild-Couder (SC) dual-mirror optical system. The GCT optical design allows the use of a compact camera of diameter roughly 0.5 m. The curved focal plane is equipped with 32 tiles of 64-pixels MAPM for a total of 2048 pixels of ~0.2° angular size, resulting in a field of view of ~9°. The GCT camera is designed to record the flashes of Cherenkov light from electromagnetic cascades, which last only a few tens of nanoseconds. I give a detailed description of the design, the challenges encountered during testing in the lab, and the performance of the most critical components. I give details on the custom front-end electronics modules that provide the required fast electronics, facilitating sampling and digitization, as well as first level of triggering. The camera-level triggering system is a custom backplane, developed to reject spurious triggers on the night sky background, which typically is of the order of few tens of millions of photons per pixel per second. This is to be compared with the rate of the astrophysical signal, which is of the order of few hundreds of events per second at the relevant energies. Additionally I provide a detailed description of all the software needed for the data acquisition and control of the camera, from the very low level drivers to high level and user friendly processes. I follow the commissioning of the camera, from the individual core components to the integration of the system. I then describe the integration of the camera on the GCT prototype telescope structure, and the achievement of "first light", validating for the first time the full proof-of-concept of an IACT with SC optics. I also report a study I performed on expectations for an extragalactic survey for blazars with CTA. The cumulative source count distribution of blazars is presented, including implications from two different phenomena: axion-like particle (ALP) to gamma-ray oscillations in the intergalactic magnetic field, and secondary gamma rays from hadronic origins. I conclude that a shallow and wide survey will provide the best science return for CTA, that the impact of ALP is modest and that the secondary mechanism of gamma-ray production would allow detection of blazars up to redshift of 1 in the multi-TeV energy band.
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Ponsa, Mussarra Daniel. "Model-Based Visual Localisation Of Contours And Vehicles". Doctoral thesis, Universitat Autònoma de Barcelona, 2007. http://hdl.handle.net/10803/5782.
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El treball d'aquesta tesi es centra en l'anàlisi de seqüències de vídeo, aplicant tècniques basades en models per extreure'n informació quantitativa. En concret, es realitzen diferents propostes en dues àrees d'aplicació: el seguiment de formes basat en models de contorns, i la detecció i seguiment de vehicles en imatges proveïdes per una camera instal·lada en una plataforma mòbil.El treball dedicat al seguiment de formes s'enquadra en el paradigma de contorns actius, del qual presentem una revisió de les diferents propostes existents. En primer lloc, mesurem el rendiment obtingut pels algorismes de seguiment més comuns (filtres basats en Kalman i filtres de partícules), i en segon lloc avaluem diferents aspectes de la seva implementació en un extens treball experimental on es consideren múltiples seqüències sintètiques, distorsionades amb diferents graus de soroll. Així, mitjançant aquest estudi determinem la millor manera d'implementar a la pràctica els algorismes de seguiment clàssics, i identifiquem els seus pros i contres.
Seguidament, el treball s'orienta cap a la millora dels algoritmes de seguiment de contorns basats en filtres de partícules. Aquest algorismes aconsegueixen bons resultats sempre que el número de partícules utilitzades sigui suficient, però malauradament la quantitat de partícules requerides creix exponencialment amb el número de paràmetres a estimar. Per tant, i en el context del seguiment de contorns, presentem tres variants del filtre de partícules clàssic, corresponents a tres noves estratègies per tractar aquest problema. En primer lloc, proposem millorar el seguiment de contorns mirant de propagar més acuradament les partícules emprades per l'algorisme d'una imatge a la següent. Això ho duem a terme utilitzant una aproximació lineal de la funció de propagació òptima. La segona estratègia proposada es basa en estimar part dels paràmetres de manera analítica. Així, es pretén fer un ús més productiu de les partícules emprades, reduint la part dels paràmetres del model que s'han d'estimar amb elles. El tercer mètode proposat té com a objectiu treure profit del fet de que, en aplicacions de seguiment de contorns, sovint els paràmetres relatius a la transformació rígida es poden estimar prou acuradament independentment de la deformació local que el contorn presenti. Això s'utilitza per realitzar una millor propagació de les partícules, concentrant-les més densament en la zona on el contorn seguit es troba. Aquestes tres propostes es validen de manera extensiva en seqüències amb diferents nivells de soroll, amb les que es mesura la millora aconseguida.
A continuació proposem tractar directament l'origen del problema anterior mitjançant la reducció del nombre de paràmetres a estimar per tal de seguir una determinada forma d'interès. Per aconseguir això, proposem modelar aquesta forma usant múltiples models, on cadascun requereix una quantitat de paràmetres inferior a la requerida per un únic model. Es proposa un nou mètode per aprendre aquests models a partir d'un conjunt d'entrenament, així com un nou algorisme per emprar-los en el seguiment dels contorns. Els resultats experimentals certifiquen la validesa d'aquesta proposta.
Finalment, la tesi es centra en el desenvolupament d'un sistema de detecció i seguiment de vehicles. Les propostes realitzades comprenen: un mòdul de detecció de vehicles, un mòdul dedicat a determinar la posició i velocitat 3D dels vehicles detectats, i un mòdul de seguiment per actualitzar la localització dels vehicles a la carretera de manera precisa i eficient. Es realitzen diverses aportacions originals en aquests tres temes, i se n'avalua el rendiment.
This thesis focuses the analysis of video sequences, applying model-based techniques for extracting quantitative information. In particular, we make several proposals in two application areas: shape tracking based on contour models, and detection and tracking of vehicles in images acquired by a camera installed on a mobile platform.
The work devoted to shape tracking follows the paradigm of active contours, from which we present a review of the existent approaches. First, we measure the performance of the most common algorithms (Kalman based filters and particle filters), and then we evaluate its implementation aspects trough an extensive experimental study, where several synthetic sequences are considered, distorted with different degrees of noise. Thus, we determine the best way to implement in practice these classical tracking algorithms, and we identify its benefits and drawbacks.
Next, the work is oriented towards the improvement of contour tracking algorithms based on particle filters. These algorithms reach good results provided that the number of particles is high enough, but unfortunately the required number of particles grows exponentially with the number of parameters to be estimated. Therefore, and in the context of contour tracking, we present three variants of the classical particle filter, corresponding to three new strategies to deal with this problem. First, we propose to improve the contour tracking by propagating more accurately the particles from one image to the next one. This is done by using a linear approximation of the optimal propagation function. The second proposed strategy is based in estimating part of the parameters analytically. Thus, we aim to do a more productive use of the particles, reducing the amount of model parameters that must be estimated through them. The third proposed method aims to exploit the fact that, in contour tracking applications, the parameters related to the rigid transform can be estimated accurately enough independently from the local deformation presented by the contour. This is used to perform a better propagation of the particles, concentrating them more densely in the zone where the tracked contour is located. These three proposals are validated extensively in sequences with different noise levels, on which the reached improvement is evaluated.
After this study, we propose to deal directly with the origin of the previous problem by reducing the number of parameters to be estimated in order to follow a given shape of interest. To reach that, we propose to model the shape using multiple models, where each one requires a lower quantity of parameters than when using a unique model. We propose a new method to learn these models from a training set, and a new algorithm to use the obtained models for tracking the contours. The experimental results certify the validity of this proposal.
Finally, the thesis focuses on the development of a system for the detection and tracking of vehicles. The proposals include: a vehicle detection module, a module devoted to the determination of the three-dimensional position and velocity of the detected vehicles, and a tracking module for updating the location of vehicles on the road in a precise and efficient manner. Several original contributions are done in these three subjects, and their performance is evaluated empirically.
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Westman, Peter y Mikael Andersson. "Design of behavior classifying and tracking system with sonar". Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11495.
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The domain below the surface in maritime security is hard to monitor with conventional methods, due to the often very noisy environment. In conventional methods the measurements are thresholded in order to distinguish potential targets. This is not always a feasible way of treating measurements. In this thesis a system based on raw measurements, that are not thresholded, is presented in order to track and classify divers with an active sonar. With this system it is possible to detect and track weak targets, even with a signal to noise ratio that often goes below 0 dB.
The system in this thesis can be divided into three parts: the processing of measurements, the association of measurements to targets and the classification of targets. The processing of measurements is based on a particle filter using Track Before Detect (TBD). Two algorithms for association of measurements, Joint Probabilistic Data Association (JPDA) and Highest Probability Data Association (HPDA), have been implemented. The classification of targets is done using an assumed novel approach. The system is evaluated by doing simulations with approximately 8 hours of recorded data, where divers are present at nine different times. The simulations are done a number of times to catch The classification rate is high and the false alarm rate is low.
Undervattensdomänen är svår att övervaka i marina säkerhetssystem med sedvanliga metoder, på grund av den brusiga miljön. I traditionella metoder trösklas mätningarna för att urskilja potentiella mål. Detta är inte alltid ett godtagbart sätt att behandla mätningar på. I den här rapporten presenteras ett system baserat på behandling av rå mätdata, som inte trösklas, för att spåra och klassificera dykare med en aktiv sonar. Med detta system är det möjligt att detektera och spåra svaga mål, trots att signal till brus förhållandet ofta går under 0 dB.
Systemet i den här rapporten kan delas upp i tre delar: behandling av mätningar, association av mätningar till mål samt klassificering av mål. Behandlingen av mätningarna görs med ett partikelfilter som använder Track Before Detect (TBD). Två algoritmer för associering av mätningar, Joint Probabilistic Data Association (JPDA) och Highest Probability Data Association (HPDA), har implementerats. Klassificeringen av mål görs med en egenutvecklad metod som inte har hittats i existerande dokumentation. Systemet utvärderas genom att simuleringar görs på ungefär 8 timmar inspelad data, där dykare är närvarande vid nio olika tillfällen. Simuleringarna görs ett antal gånger för att fånga upp stokastiska beteenden. Andelen lyckade klassificeringar är hög och andelen falsklarm är låg.
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Giuriato, Umberto. "Dynamique des particules actives dans les superfluides et leur interaction avec les vortex quantiques". Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4062.
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Les superfluides sont des fluides non visqueux dans lesquels la vorticité se concentre sur des filaments ayant une circulation quantifiée. Ces objets, appelés vortex quantiques, possèdent un comportement hydrodynamique. Expérimentalement, la dynamique des superfluides est souvent étudiée en utilisant des particules. Les particules sont aujourd’hui devenues l’outil principal pour visualiser les vortex quantiques. Dans cette thèse, nous étudions numériquement et analytiquement la dynamique des particules actives et de taille finie dans les superfluides. Le superfluide est modélisé avec l’équation Gross–Pitaevskii, tandis que les particules sont implémentées comme des potentiels répulsifs mobiles couplés avec la fonction d’onde macroscopique décrivant le superfluide. Le modèle est utilisé pour étudier l’interaction entre les particules et les tourbillons quantiques à très basse température. Cette première partie vise à donner un contexte théorique aux expériences actuelles dans lesquelles des particules macroscopiques sont utilisées pour échantillonner les vortex superfluides et la turbulence quantique. Plus précisément, nous abordons les problèmes suivants : la capture d’une particule par un vortex quantique, les reconnexions des filaments de vortex et la propagation des ondes Kelvin en présence de particules piégées, ainsi que la dynamique des particules dans la turbulence quantique en déclin. Dans la dernière partie du manuscrit, les effets de température finis sont étudiés dans le modèle Gross–Pitaevskii avec une troncature spectrale. L’objectif est de caractériser la dynamique des impuretés immergées dans un bain thermal et comment leur présence modifie les propriétés statistiques du fluide. En particulier, le mouvement aléatoire des impuretés et la dépendance en température du coefficient de frottement sont étudiés. Enfin, le clustering des impuretés et son effet sur les transitions de phase du condensat sont examinésSuperfluids are inviscid flows in which vorticity is supported on filaments with quantized circulation. Such objects, known as quantum vortices, exhibit a hydrodynamical behavior. Experimentally, the dynamics of superfluids has been studied by using particles, which nowadays have become the main tool for visualizing quantum vortices. In this Thesis, we study numerically and analytically the dynamics of active and finite-size particles in superfluids. The superfluid is modeled with the Gross–Pitaevskii equation, while the particles are implemented as moving repulsive potentials coupled with the macroscopic wave function describing the superfluid. Firstly, the model is used to investigate the interaction between particles and quantum vortices at very low temperatures. This part aims to give a theoretical background to the current experiments in which macroscopic particles are used to sample superfluid vortices and quantum turbulence. Specifically, we address the following problems: the capture of a particle by a quantum vortex, the reconnections of vortex filaments and the propagation of Kelvin waves in presence trapped particles and the dynamics of particles in decaying quantum turbulence. In the last part of the manuscript, finite temperature effects are studied in the Fourier-truncated Gross–Pitaevskii model. The goal is to characterize the dynamics of impurities immersed in a thermal bath and how their presence modifies the statistical properties of the fluid. In particular, the random motion of the impurities and the temperature dependence of the friction coefficient are studied. Finally, the clustering of impurities and its effect on the phase transitions of the condensate are investigated
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Rozman, Jaroslav. "Navigace mobilních robotů". Doctoral thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2011. http://www.nusl.cz/ntk/nusl-261251.
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Mobile robotics has been very discussed and wide spread topic recently. This due to the development in the computer technology that allows us to create better and more sophisticated robots. The goal of this effort is to create robots that will be able to autonomously move in the chosen environment. To achieve this goal, it is necessary for the robot to create the map of its environment, where the motion planning will occur. Nowadays, the probabilistic algorithms based on the SLAM algorithm are considered standard in the mapping in these times. This Phd. thesis deals with the proposal of the motion planning of the robot with stereocamera placed on the pan-and-tilt unit. The motion planning is designed with regard to the use of algorithms, which will look for the significant features in the pair of the images. With the use of the triangulation the map, or a model will be created. The benefits of this work can be divided into three parts. In the first one the way of marking the free area, where the robot will plan its motion, is described. The second part describes the motion planning of the robot in this free area. It takes into account the properties of the SLAM algorithm and it tries to plan the exploration in order to create the most precise map. The motion of the pan-and-tilt unit is described in the third part. It takes advantage of the fact that the robot can observe places that are in the different directions than the robot moves. This allows us to observe much bigger space without losing the information about the precision of the movements.