Dissertations / Theses on the topic 'Implosion'
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1
Gish, Lynn Andrew. "Analytic and numerical study of underwater implosion." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81699.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 203-205).
Underwater implosion, the rapid collapse of a structure caused by external pressure, generates a pressure pulse in the surrounding water that is potentially damaging to adjacent structures or personnel. Understanding the mechanics of implosion, specifically the energy transmitted in the pressure pulse, is critical to the safe and efficient design of underwater structures. Hydrostatically-induced implosion of unstiffened metallic cylinders was studied both analytically and numerically. An energy balance approach was used, based on the principle of virtual velocities. Semi-analytic solutions were developed for plastic energy dissipation of a symmetric mode 2 collapse; results agree with numerical simulations within 10%. A novel pseudo-coupled fluid-structure interaction method was developed to predict the energy transmitted in the implosion pulse; results agree with fully-coupled numerical simulations within 6%. The method provides a practical alternative to computationally-expensive simulations when a minimal reduction in accuracy is acceptable. Three design recommendations to reduce the severity of implosion are presented: (1) increase the structure's internal energy dissipation by triggering higher collapse modes, (2) initially pressurize the internals of the structure, and (3) line the cylinder with a flexible or energy absorbing material to cushion the impact between the structure's imploding walls. These recommendations may be used singly or in combination to reduce or completely eliminate the implosion pulse. However, any design efforts to reduce implosion severity must be part of the overall system design, since they may have detrimental effects on other performance areas like strength or survivability.
by Lynn Andrew Gish.
Ph.D.
2
Scardigli, Corinne. "Implosion : gestion des stocks par la replanification amont." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0057.
Abstract:
Quel que soit le système de gestion adopté, les aléas de production, les retards, les commandes urgentes, les variations des carnets de commande entraînent de nombreux dysfonctionnements. Il en découle des différences entre le niveau réel des stocks et le niveau nécessaire au système de gestion. Peut-on pallier ce problème ? Pour répondre à cette question, nous avons développé un concept basé sur une approche de replanification amont appelé implosion. Dans ce mémoire, nous décrivons, dans une première partie, la situation actuelle des entreprises afin d'identifier la problématique. Celle-ci met en évidence l'apparition de nouveaux besoins qui sont la flexibilité, l'adaptabilité, la réactivité et le recouvrement qui, nous pensons, marquent l'entrée dans un nouveau paradigme de production. Ceci nous a amené à réaliser une recherche sur les nouveaux concepts de production et une enquête auprès d'entreprises de divers secteurs d'activité. Ces travaux nous ont permis de situer l'implosion et d'établir ses conditions d'utilisation. La seconde partie est consacrée à une analyse mathématique du problème. Nous établissons les notations et les principes sous-jacents à l'implosion. Nous avons ainsi montré que le problème était NP-Difficile et que l'ensemble des solutions définissait une famille de treillis distributifs. Différentes techniques de résolutions ont été étudiées et comparées: Enumération, Branch & Bound, Programmation linéaire, méthodes aléatoires, techniques d'amélioration successive, recuit simulé et algorithme génétiques
3
Krueger, Seth R. "Simulation of cylinder implosion initiated by an underwater explosion." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FKrueger.pdf.
Abstract:
Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2006.Thesis Advisor(s): Young S. Shin. "June 2006." Includes bibliographical references (p. 99-100). Also available in print.
4
Szirti, Daniel. "Development of a single-stage implosion-driven hypervelocity launcher." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112585.
Abstract:
The present study deals with the development of a single-stage implosion-driven hypervelocity launcher. A thin-walled tube filled with helium surrounded by explosives acts as a driver for the launcher. Implosion of the tube drives a strong shock that reflects back and forth between the projectile and the implosion pinch, generating very high temperatures and pressures. Simple analytic models were used to approximate the performance of the pump tube and its use as a driver for a launcher. Experiments to evaluate the implosion dynamics and performance of the pump tube were carried out, and implosion-driven launcher experiments demonstrated muzzle velocities above 4 km/s with 5-mm-diameter aluminum projectiles. Projectile integrity was verified by high-speed photography. Disagreement of experimental data with the analytical models of performance is mostly due to failure to seal the chamber of the launcher, resulting in loss of driver gas, and pump tube expansion, which weakens the precursor shock.
5
Sigley, Thomas E. "Evangelism implosion getting to the heart of the issue /." Theological Research Exchange Network (TREN), 1997. http://www.tren.com.
6
Kinnear, Timothy Michael. "Investigation into triggered star formation by radiative driven implosion." Thesis, University of Kent, 2016. https://kar.kent.ac.uk/52436/.
Abstract:
When massive stars form, they emit strong, hydrogen ionising radiation fields into their molecular cloud environment, forming HII regions. This is believed to be capable of inducing effects which can trigger further star formation through a process known as Radiative Driven Implosion. Hydrodynamic shock fronts are generated at the interface between ionised and un-ionised material. These shocks propagate into the clouds, and their motion and increase in density can result in the conditions required for star formation. Using the method of Smoothed Particle Hydrodynamics, the effect of varied initial geometrical and physical properties of a molecular cloud on the prospect of radiation triggered star formation is investigated over a large parameter space. The physical processes of the model include a detailed ray-tracing implementation of the ionising radiation, along with a thermodynamic model and chemical evolution for multiple species of atoms. A parameter d_euv, defined as the ratio of the initial ionising penetration depth to the scale length of the cloud along the radiation axis, was found to be an effective indicator of the final evolutionary prospects of the molecular clouds investigated. Low d_euv clouds typically exhibit shock front motion which converges on a focus or foci, and form symmetric or asymmetric B or C type Bright Rimmed Clouds depending on orientation. At medium d_euv there is a mixture of focus/foci convergent and linear or filamentary structure formation with cores formed indirectly, after disruption of material by the shock fronts. At high d_euv only fragment-core and irregular structures form, with the clouds being increasingly dominated by photoevaporation. At extremely high d_euv cores cannot form and the cloud will photoevaporate. In addition, qualitative impressions of the scope of structure morphologies, especially those for irregular morphologies, is compiled. Of note, it is found that the simple initial conditions of a uniform prolate cloud at inclinations to incident radiation are capable of producing a wide variety of the structures observed at HII boundaries.
7
Smith, Joel Aaron. "Implosion of steel fibre reinforced concrete cylinders under hydrostatic pressure." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ45939.pdf.
8
Cardoso, Pedro Daniel Martins Lucas. "The future of old-age pensions its explosion and implosion /." [Amsterdam : Amsterdam : Thela Thesis] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/76523.
9
Loiseau, Jason. "Phase velocity techniques for the implosion of pressurized linear drivers." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94919.
Abstract:
The present study deals with the evaluation of several explosive phase velocity techniques to produce very high apparent detonation velocities on linear or cylindrical targets. In particular, the pairing of two explosive components with different detonation velocities to drag a structured detonation wave was shown to be accurate in generating desired phase velocities. The technique of subdividing a detonation wave into multiple, discrete detonation channels and injecting them into the desired geometry was also evaluated and shown to be similarly accurate. Analytical models for designing the explosive components in these techniques in order to produce a desired phase velocity are presented in detail. A novel method of generating an axisymmetrical, implosive linear phase velocity was also developed by varying the wall thickness of a cylindrical metal flyer/liner. This device was experimentally demonstrated to produce phase velocities but with significant deviations from analytical modelling predictions. The two component phasing technique was also applied to a linear explosive shock tube. The shock tube was constructed from a thin-walled metal tube and surrounded by a thin annulus of explosives and then a thick-walled metal tube. The phased detonation wave was injected via a thin slit in the top of the thick-walled tube. A quasi-steady shock wave was driven at velocities between 10.5~km/s and 11~km/s with this device.L'étude présente porte sur l'évaluation de plusieurs techniques pour générer une vitesse de phase dans un explosif afin de produire de très hautes vitesses de détonation sur des cibles linéaires ou cylindriques. En particulier, il a été démontré que le jumelage de deux composantes explosives ayant des vitesses de détonation différentes pour faire glisser une onde de détonation structurée est une méthode pouvant précisément générer des vitesses de phase désirées. La méthode de la division d'une onde de détonation dans plusieurs canaux individuels fut évaluée et il fut démontré qu'elle est aussi précise. Des modèles analytiques pour la conception des composantes explosives nécessaires à la production des vitesses de phase désirées en utilisant ces techniques sont présentés en détail. Une nouvelle méthode pour générer une vitesse de phase axisymétrique, implosive et linéaire a été également mise au point en faisant varier l'épaisseur de la paroi d'un tube métallique cylindrique. Il fut démontré que cet appareil est capable de produire des vitesses de phase, mais avec des écarts importants avec les prévisions analytiques. La technique qui utilise les deux composantes a également été appliquée à un tube à chocs explosif linéaire. Le tube à chocs a été construit à partir d'un tube métallique à parois mince et entouré par un anneau mince d'explosifs puis un tube de métal à parois épaisse. L'onde de détonation a été progressivement injectée par une mince fente dans le haut du tube à parois épaisse. Une onde de choc a été entraînée à des vitesses allant jusqu'à 11~km/s avec cet appareil.
10
Rallu, Arthur Seiji Daniel. "A multiphase fluid-structure computational framework for underwater implosion problems /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
11
Kamram, Kazem. "A compressible Lagrangian framework for the simulation of underwater implosion problems." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/128876.
Abstract:
The development of efficient algorithms to understand implosion dynamics presents a number of challenges. The foremost challenge is to efficiently represent the coupled compressible fluid dynamics of internal air and surrounding water. Secondly, the method must allow one to accurately detect or follow the interface between the phases. Finally, it must be capable of resolving any shock waves which may be created in air or water during the final stage of the collapse. We present a fully Lagrangian compressible numerical framework for the simulation of underwater implosion. Both air and water are considered compressible and the equations for the Lagrangian shock hydrodynamics are stabilized via a variationally consistent multiscale method [109]. A nodally perfect matched definition of the interface is used [57, 25] and then the kinetic variables, pressure and density, are duplicated at the interface level. An adaptive mesh generation procedure, which respects the interface connectivities, is applied to provide enough refinement at the interface level. This framework is then used to simulate the underwater implosion of a large cylindrical bubble, with a size in the order of cm. Rapid collapse and growth of the bubble occurred on very small spatial (0.3mm), and time (0.1ms) scales followed by Rayleigh-Taylor instabilities at the interface, in addition to the shock waves traveling in the fluid domains are among the phenomena that are observed in the simulation. We then extend our framework to model the underwater implosion of a cylindrical aluminum container considering a monolithic fluid-structure interaction (FSI). The aluminum cylinder, which separates the internal atmospheric-pressure air from the external high-pressure water, is modeled by a three
node rotation-free shell element. The cylinder undergoes fast transient deformations, large enough to produce self-contact along it. A novel elastic frictionless contact model is used to detect contact and compute the non-penetrating forces in the discretized domain between the mid-planes of the shell. Two schemes are tested, implicit using the predictor/multi-corrector Bossak scheme, and explicit, using the forward Euler scheme. The results of the two simulations are compared with experimental data.El desarrollo de métodos eficientes para modelar la dinámica de implosión presenta varios desafíos. El primero es una representación eficaz de la dinámica del sistema acoplado de aire-agua. El segundo es que el método tiene que permitir una detección exacta o un seguimiento adecuado de la interfase entre ambas fases. Por último el método tiene que ser capaz de resolver cualquier choque que podría generar en el aire o en el agua, sobre todo en la última fase del colapso. Nosotros presentamos un método numérico compresible y totalmente Lagrangiano para simular la implosión bajo el agua. Tanto el aire como el agua se consideran compresibles y las ecuaciones Lagrangianos para la hidrodinámica del choque se estabilizan mediante un método multiescala que es variacionalmente consistente [109]. Se utiliza una definición de interfase que coincide perfectamente con los nodos [57, 25]. Ésta, nos facilita duplicar eficazmente las variables cinéticas como la presión y la densidad en los nodos de la interfase. Con el fin de obtener suficiente resolución alrededor de la interfase, la malla se genera de forma adaptativa y respetando la posición de la interfase. A continuación el método desarrollado se utiliza para simular la implosión bajo el agua de una burbuja cilíndrica del tamaño de un centímetro. Varios fenómenos se han capturado durante el colapso: un ciclo inmediato de colapso-crecimiento de la burbuja que ocurre en un espacio (0.3mm) y tiempo (0.1ms) bastante limitado, aparición de inestabilidades de tipo Rayleigh-Taylor en la interfase y formaron de varias ondas de choque que viajan tanto en el agua como en el aire. Después, seguimos el desarrollo del método para modelar la implosión bajo el agua de un contenedor metálico considerando una interacción monolítica de fluido y estructura. El cilindro de aluminio, que a su vez contiene aire a presión atmosférica y está rodeada de agua en alta presión, se modelando con elementos de lámina de tres nodos y sin grados de libertad de rotación. El cilindro se somete a deformaciones transitorias suficientemente rápidos y enormes hasta llegar a colapsar. Un nuevo modelo elástico de contacto sin considerar la fricción se ha desarrollado para detectar el contacto y calcular las fuerzas en el dominio discretizado entre las superficies medianas de las laminas. Dos esquemas temporales están considerados, uno es implícito utilizando el método de Bossak y otro es explícito utilizando Forward Euler. Al final los resultados de ambos casos se comparan con los resultados experimentales.
12
Haboub, Abdelmoula. "Study of ablation and implosion phases in cylindrical and star wire arrays." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3387809.
13
Huneault, Justin. "Development of an implosion-driven hypervelocity launcher for orbital debris impact simulation." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117206.
Abstract:
The ability to soft-launch projectiles to velocities exceeding 10 km/s is of interest for a number of scientific fields, including orbital debris impact testing. Current soft-launch technologies have reached a performance plateau below this operating range. In the implosion-driven launcher (IDL) concept, explosives are used to linearly implode a pressurized steel tube, thereby dynamically compressing a light driver gas to significantly higher pressures and temperatures than typical light-gas launchers. As a result, the IDL has the potential to significantly outperform current state of the art hypervelocity launchers. This work will focus on establishing an understanding of the critical design parameters of the IDL with the goal of improving the velocity potential of the launcher. For this purpose, a computational gasdynamics solver capable of simulating the internal ballistics of the IDL has been developed. The elevated pressure and temperature in the driver gas lead to a number of non-ideal effects during the launch cycle, including expansion of the launcher walls, convective heat transfer, and gas leakage, which have a significant effect on launcher performance. These effects have been simulated by coupling the gasdynamics solver to loss models. Specifically, a structural hydrocode has been developed to provide a realistic model of reservoir and launch tube expansion, which has been identified as the main source of performance loss in the launch cycle. The complete internal ballistics solver will be used in conjunction with classical internal ballistics theory and experimental results, in order to gain valuable understanding of the key design parameters of the launcher and improve the design of the McGill IDL. This analysis has led to the development of an IDL capable of launching a 0.1-g projectile to 9.1 km/s.La capacité d'accéléré des projectiles à des vitesses au-delà de 10 km/s est d'intérêt pour de nombreuses applications, incluant la protection contre les débris spatiaux. La performance des lanceurs hyper-vitesse de pointe n'est pas capable de rejoindre ces vitesses. Le lanceur à implosion utilise des explosifs pour comprimer un gaz léger de façon dynamique, afin d'atteindre des pressions et des températures beaucoup plus élevés que des lanceurs hyper-vitesse typiques. Pour cette raison, le lanceur à implosion à le potentiel de surpasser la performance de tout autre lanceur. Ce travail mettra l'accent sur l'établissement d'une compréhension des paramètres de conception critiques du lanceur à implosion dans le but d'améliorer la performance du lanceur. A cet effet, un code capable de simuler la balistique interne du lanceur a été développé. La pression et la température élevées dans le gaz causent plusieurs pertes durant le cycle de lancement, y compris l'expansion des parois du lanceur, le transfert de chaleur par convection, et les fuites de gaz. Ces pertes ont un effet important sur la performance du lanceur. Les modèles utilisés pour simuler ces pertes sont aussi présentés. Le code complet sera utilisé en conjonction avec la théorie classique de la balistique interne ainsi que des résultats expérimentaux afin d'amélioré le lanceur. Cette analyse a conduit à l'élaboration d'un lanceur à implosion capable d'accéléré un projectile de 0,1 g à 9,1 km/s.
14
Oudkerk, Richard. "The parabolic implosion for f0(z) = z + zv+1 + O(zv+2)." Thesis, University of Warwick, 1999. http://wrap.warwick.ac.uk/56137/.
Abstract:
In this thesis we examine the bifurcation in behaviour (for the dynamics) which occurs when we perturb the holomorphic germ fo(z) =z + zv+1 + O(zv+2) defined in a neigh- bourhood of 0, so that the multiple fixed point at 0 splits into v+1 fixed points (counted with multiplicity). The phenomenon observed is called the parabolic implosion, since the perturbation will typically cause the filled Julia set (if it is defined) to "implode. " The main tool used for studying this bifurcation is the Fatou coordinates and the associated Ecalle cylinders. We show the existence of these for a family of well behaved f's close to fo, and that these depend continuously upon f. Each well behaved f will have a gate structure which gives a qualitative description of the "egg-beater dynamic" for f. Each gate between the fixed points of f will have an associated complex number called the lifted phase. (Minus the real part of the lifted phase is a rough measure of how many iterations it takes for an orbit to pass through the gate. ) The existence of maps with any desired gate structure and any (sensible) lifted phases is shown. This leads to a simple parameterisation of the well behaved maps. We are particularly interested in sequences fk → fo where all the lifted phases of the fk converge to some limits, modulo Z. We show that there is a non-trivial Lavaurs reap g associated with these limits, which commutes with fo. The dynamics of fk are shown to (in some sense) converge to the dynamics of the system (fo, g). We also prove that for any Lavaurs map g there is a sequence fk → fo so that fk k → g as k → +oo, uniformly on compact sets.
15
Demeter, Jason M. "Melancholy and the Implosion of the Family in Early- and Post-Modern Tragedy." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1208264666.
16
Hall, Gareth. "The relationship between implosion dynamics and stagnation structure in aluminium wire-array Z-pinches." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444403.
17
Khoory, Essa. "Experimental study of plasma implosion dynamics in a two-stage wire array Z-pinch configuration." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/14271.
Abstract:
This thesis presents results from experiments of a two-stage wire array Z-pinch configuration carried out on the MAGPIE generator ( ~ 1.4MA in ~ 250ns) at Imperial College, London. This configuration preconditions the load wires (heating and expanding wires into columns of gas) before allowing the full current to rapidly switch into the load. The preconditioning effect of cylindrical Al wire array loads of different wire numbers and wire thicknesses were investigated from density analysis of laser interferometry. It was found that thicker wires expand to larger diameters than thinner wires in the preconditioning phase. The 30μm wire expanded to a diameter of 3.7±0.4mm while the 10μm wire expanded to a diameter of 1.6±0.4mm in ~ 170ns after current start. Experiments were also conducted on a single Al wire load of different thicknesses. Again thicker wires expanded to a larger diameter. This uniform column of Al gas on axis showed a high degree of azimuthal symmetry. The fast current switch into the load drives a snowplough implosion with an implosion time of ~ 25-30ns with no apparent development of Rayleigh-Taylor instability. It was observed at stagnation that the expansion the m=1 MHD instability into a helical structure was responsible for the main X-ray pulse. A cylindrical plasma ‘shell’ was formed by preconditioning an array of large wire number and a small inter-wire separation causing the expanding wires to merge before the current switch time. The shell imploded in a 0D manner with no ablation phase and no trailing mass left behind as in standards wire arrays. Implosion of the ‘shell’ was susceptible to R-T instability. Analysis of this instability growth estimated an initial effective perturbation of ~ 1-2μm on the preconditioned wires surface prior to implosion.
18
Bianchi, Fabrizio. "Motions of Julia sets and dynamical stability in several complex variables." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30099/document.
Abstract:
Dans cette thèse, on s'intéresse aux systèmes dynamiques holomorphes dépendants de paramètres. Notre objectif est de contribuer à une théorie de la stabilité et des bifurcations en plusieurs variables complexes, généralisant celle des applications rationnelles fondées sur les travaux de Mané, Sad, Sullivan et Lyubich. Pour une famille d'applications d'allure polynomiale, on prouve l'équivalence de plusieurs notions de stabilité, entre autres une version asymptotique du mouvement holomorphe des cycles répulsifs et d'un sous-ensemble de l'ensemble de Julia de mesure pleine. Cela peut etre considéré comme une généralisation mesurable à plusieurs variables du célèbre lambda-lemme et nous permet de dégager un concept cohérent de stabilité dans ce cadre. Après avoir compris les bifurcations holomorphes, on s'intéresse à la continuité Hausdorff des ensembles de Julia. Nous relions cette propriété à l'existence de disques de Siegel dans l'ensemble de Julia, et donnons un exemple de ce phénomène. Finalement, on étudie la continuité du point de vue de l'implosion parabolique. Nous établissons un théorème de Lavaurs deux-dimensionel, ce qui nous permet d'étudier des phénomènes de discontinuité pour des perturbations d'applications tangentes à l'identitéIn this thesis we study holomorphic dynamical systems depending on parameters. Our main goal is to contribute to the establishment of a theory of stability and bifurcation in several complex variables, generalizing the one for rational maps based on the seminal works of Mané, Sad, Sullivan and Lyubich. For a family of polynomial like maps, we prove the equivalence of several notions of stability, among the others an asymptotic version of the holomorphic motion of the repelling cycles and of a full-measure subset of the Julia set. This can be seen as a measurable several variables generalization of the celebrated lambda-lemma and allows us to give a coherent definition of stability in this setting. Once holomorphic bifurcations are understood, we turn our attention to the Hausdorff continuity of Julia sets. We relate this property to the existence of Siegel discs in the Julia set, and give an example of such phenomenon. Finally, we approach the continuity from the point of view of parabolic implosion and we prove a two-dimensional Lavaurs Theorem, which allows us to study discontinuities for perturbations of maps tangent to the identity
19
Chéritat, Arnaud. "Sur l'implosion parabolique, la taille des disques de Siegel et une conjecture de Marmi, Moussa et Yoccoz." Habilitation à diriger des recherches, Université Paul Sabatier - Toulouse III, 2008. http://tel.archives-ouvertes.fr/tel-00291673.
Abstract:
Tout le contenu de ce mémoire est un travail en commun de l'auteur et de Xavier Buff.Pour theta nombre de Brjuno, soit r(theta) le rayon conforme du disque de Siegel de P_theta(z)=exp(i.2.pi.theta)z+z^2 et Phi(theta) la variante due à Yoccoz de la somme de Brjuno. Soit Upsilon(theta) = log r(theta) + Phi(theta).
Nous avons démontré précédemment que Upsilon possède un prolongement continu à R, et donné une formule explicite pour sa valeur aux rationnels.
La conjecture de Marmi-Moussa-Yoccoz, toujours ouverte, est que la fonction Upsilon est 1/2-Höldérienne.
Nous démontrons ici que l'exposant ne peut être amélioré : quel que soit l'intervalle I non vide, Upsilon n'est delta-Höldérienne sur I pour aucun delta>1/2. Sa variation sur I est également non bornée.
La preuve est basée sur un développement asymptotique en tout p/q de Upsilon(x_n) pour certaines suites de rationnels x_n tendant vers p/q.
L'étude d'un point parabolique et de ses perturbations se fait parfois par l'introduction d'un champ de vecteurs auquel la dynamique est comparée.
Nous introduisons un champ de vecteurs particulier qui permet d'une part de donner des estimations suffisamment fines pour effectuer le développement asymptotique de Upsilon(x_n) ; d'autre part de proposer une normalisation intéressante des coordonnées de Fatou d'un point parabolique, dont nous donnons quelques propriétés de base.
J'ai apporté un soin particulier à la rédaction de l'implosion parabolique, qu'il a fallu raffiner légèrement et adapter à notre champs de vecteurs.
20
Ferris, Emma Grace. "A computational and experimental study of the underwater implosion of single and multiple metallic spherical shells." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/111762.
Abstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-104).
Analysis of the implosion of pressure vessels in a deep-water environment is an important research area for the ocean engineering community. The majority of previous implosion research focused on the implosion of metallic cylinders, while the implosion behavior of volumes of different geometries and materials is less well researched. The behavior of pressure pulses resulting from the implosion of multiple pressure vessels is also less well researched. This thesis addresses these questions by investigating the implosion behavior of single and multiple spherical shells. Over the course of this research, I designed and predicted the collapse depth of metallic spherical volumes using shell buckling theory, then used a computational tool to model several implosion scenarios of both single and multiple sphere configurations. I then conducted implosion tests of single and multiple spherical shell configurations. The results from the initial computational models were compared with results of experimental tests and used to develop updated computational models that more accurately represented the true geometry of the test articles. Based on the analysis of the results of initial computational models and the experimental results, and the correlation between the updated computational models and experimental results, I identified ways to more accurately model scenarios involving implosions of spherical shells. In addition, I analyzed the behavior of a sympathetic implosion event involving two spherical shells and compared the result of the sympathetic implosion event to that of a single equivalent volume. This thesis concludes with guidance for future modeling and experimental testing efforts.
by Emma Grace Ferris.
S.M.
21
Ferris, Emma Grace. "A computational and experimental study of the underwater implosion of single and multiple metallic spherical shells." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111762.
Abstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-104).
Analysis of the implosion of pressure vessels in a deep-water environment is an important research area for the ocean engineering community. The majority of previous implosion research focused on the implosion of metallic cylinders, while the implosion behavior of volumes of different geometries and materials is less well researched. The behavior of pressure pulses resulting from the implosion of multiple pressure vessels is also less well researched. This thesis addresses these questions by investigating the implosion behavior of single and multiple spherical shells. Over the course of this research, I designed and predicted the collapse depth of metallic spherical volumes using shell buckling theory, then used a computational tool to model several implosion scenarios of both single and multiple sphere configurations. I then conducted implosion tests of single and multiple spherical shell configurations. The results from the initial computational models were compared with results of experimental tests and used to develop updated computational models that more accurately represented the true geometry of the test articles. Based on the analysis of the results of initial computational models and the experimental results, and the correlation between the updated computational models and experimental results, I identified ways to more accurately model scenarios involving implosions of spherical shells. In addition, I analyzed the behavior of a sympathetic implosion event involving two spherical shells and compared the result of the sympathetic implosion event to that of a single equivalent volume. This thesis concludes with guidance for future modeling and experimental testing efforts.
by Emma Grace Ferris.
S.M.
22
Čepukas, Andrius. "Medijų visuomenės kritika J. Baudrillardo filosofijoje." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080924_181309-83071.
Abstract:
Darbe analizuojama J. Baudrillardo filosofija, fundamentalios problemos, iškylančios medijoms radikaliai transformavus šiuolaikinę visuomenę.In the study we analyse Baudrillard's philosophy, Problematics of the study lies on media analysis and transformation of the society.
23
Astorg, Matthieu. "Théorie de Teichmüller dynamique infinitésimale et domaines errants." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30042/document.
Abstract:
Soit f une fraction rationnelle de degré d au moins 2. McMullen et Sullivan ont introduit l'espace de Teichmüller dynamique Teich(f), qui est une variété complexe de dimension au plus 2d-2 et qui paramétrise la classe de conjugaison quasiconforme de f dans l'espace des modules ratd via une application holomorphe F allant de Teich(f) dans ratd.Nous donnons une nouvelle construction élémentaire de Teich(f), et nous prouvonsque F est une immersion, ce qui répond à une question posée par McMullen et Sullivan.Ce dernier résultat nous permet d'obtenir des preuves simplifiées de résultats dus à Makienko et Levin sur la rigidité de f sous une hypothèse d'expansivité le long de l'orbite critique. Dans une seconde partie, nous construisons une famille d'exemples d'endomorphismes polynômiaux de P^2(C) ayant un domaine errant. Nos exemples sont des produits fibrés, de la forme (z,w) -> ( f(z) + aw, g(w)). De plus, on construira des exemples à coefficients réels où le domaine errant intersectera R^2Let f be a rational map of degree d at last 2. McMullen and Sullivan introduced the dynamical Teichmüller space Teich(f), which is a complex manifold of dimension at most 2d-2. It paramtrizes the quasiconformal conjugacy class of f in the moduli space ratdvia a holomorphic map F from Teich(f) to ratd. We give a new and elementary construction of Teich(f), and we prove that the parametrization F is an immersion, answering a question of McMullen and Sullivan. This last result enables us to give simplified proofs of rigidity results of Makienko and Levin under the assumption of expansion along the critical orbit. In a second part, we construct a family of examples of polynomial endomorphisms of¨P^2(C) with a wandering domain. Our examples are skew-products, of the form (z,w) -> (f(z)+aw, g(w)). Moreover, we will construct examples with real coefficients where the wandering domain intersects R^2
24
Leckie, Barbara. "That ancient darkness : madness and implosion in Michael Ondaatje's The collected works of Billy the Kid and Coming through slaughter." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65982.
25
Spens, Ellen. "Diffrakterande praktiker med implosiva konsekvenser: Perspektiv på estetiska lärprocesser." Thesis, Malmö högskola, Fakulteten för lärande och samhälle (LS), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-34773.
Abstract:
Studiens övergripande syfte är att fördjupa kunskaper om och söka nya perspektiv på estetiska lärprocesser i relation till demokrati- och värdegrundsfrågor. Den teoretiska ansatsen hämtas från poststrukturalistisk teoribildning med förgreningar inom genusteori. Studien är strukturerad i tre delar inom vilken den första utgörs av en samläsning mellan kunskapsområdet scenkonstnärlig teori/praktik och pedagogisk teori/praktik. Dessa diskurser karaktäriseras av ifrågasättanden av konsten som ”god” respektive antaganden om värdeneutrala pedagogiska modeller och det ”goda” samhället som automatisk följd av bildning och fostran. Utifrån samläsningen analyseras inom studiens andra del dokumenterade utsnitt hämtade från ett projektarbete på en skola. Detta empiriska material fyller funktionen att både exemplifiera och problematisera samläsningens utfall. Den tredje delen av studien grundar sig på de tidigare delarna och avser överskrida uppdelningen mellan scenkonstnärlig respektive pedagogisk teori/praktik genom ett framskrivande av vad som inom studien benämns som diffrakterade praktiker med implosiva konsekvenser.Genom studien analyseras det risktagande som det alltid innebär att öppna upp för liksom ingå i processer av förhandling där det inte finns några givna svar samt hur dessa processer också kräver ständiga ställningstaganden utifrån den specifika kontexten. Vidare synliggörs hur processer som ifrågasätter det förgivettagna också förutsätter vissa strukturer. Studien lyfter också fram betydelsen av andra förhållningssätt till den osäkerhet, ambivalens och det motstånd som estetiska lärprocesser exempelvis genom olika positionsförflyttningar kan resultera i. På detta sätt är avsikten att värdera dessa konsekvenser som syften i sig. I en avslutande diskussion belyses studiens resultat i perspektiv av ett samhälle präglat av förändring och mångfald och därmed också relevansen av estetiska lärprocesser i en utbildningspolitisk kontext.
26
Chéritat, Arnaud. "Recherche d'ensembles de Julia de mesure de Lebesgue positive." Paris 11, 2001. http://www.theses.fr/2001PA112313.
Abstract:
Nous introduisons la notion de taille asymptotique d'un point parabolique, qui nous permet de démontrer une conjecture de Douady, ainsi que de donner une nouvelle preuve d'un théorème de Yoccoz. Nous donnons une constuction géométrique d'une application holomorphe, qui généralise aux applications de cornes des résultats que la fraction de Blaschke z au carré fois z moins trois sur un moins trois z permettait d'obtenir pour les polynômes quadratiques ayant un point fixe indifférent de nombre de rotation de type constant. Nous énonçons deux conjectures et deux hypothèses et prouvons qu'elles impliquent l'existence d'un irrationnel theta tel que le polynôme P de z égale rho fois z plus z au carré, avec rho égale exponentielle de i fois deux fois pi fois theta, ait un ensemble de Julia J de mesure de Lebesgue strictement positiveWe define the asymptotic size of a parabolic fixed point, that enables to prove a conjecture of Douady and to give a new proof of a theorem of Yoccoz. We give a geometric construction of a holomorphic map, that extends to horn maps some results that the Blaschke fraction z squared times z minus three over one minus three z gave for quadratic polynomials with an indifferent fixed point of bounded type rotation number. We state two conjectures and two hypotheses, and prove that they imply the existence of an irrational theta such that the polynomial P of z equals rho times z plus z squared, with rho equals exponential of i times two times pi times theta has a Julia set J of positive Lebesgue measure
27
Samulski, Camille Clement. "Deceleration Stage Rayleigh-Taylor Instability Growth in Inertial Confinement Fusion Relevant Configurations." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/103703.
Abstract:
Experimental results and simulations of imploding fusion concepts have identified the Rayleigh-Taylor (RT) instability as one of the largest inhibitors to achieving fusion. Understanding the origin and development of the RT instability will allow for the development of mitigating measures to dampen the instability growth, thus improving the chance that fusion concepts such as inertial confinement fusion (ICF) are successful. A study of 1D and 2D simulations are presented for investigating RT instability growth in deceleration stage of imploding geometries. Two cases of laser-driven implosion geometry, Cartesian and cylindrical, are used to study late stage deceleration-phase RT instability development on the interior surface of imploding targets. FLASH's hydrodynamic (HD) and magnetohydrodynamic (MHD) modeling capabilities are used for different laser and target parameters in order to study the RT instability and the impact of externally applied magnetic fields on their evolution. Several simulation regimes have been identified that provide novel insight into the impact that a seeded magnetic field can have on RT instability growth and the conditions under which magnetic field stabilization of the RT instability is observable. Finally, future work and recommendations are made.Master of Science
The direction for the future of renewable energy is uncertain at this time; however, it is known that the future of human energy consumption must be green in order to be sustainable. Fusion energy presents an opportunity for an unlimited clean renewable energy source that has yet to be realized. Fusion is achieved only by overcoming the earthly limitations presented by trying to replicate conditions at the interior of stellar structures. The pressures, temperature, and densities seen in the interior of stars are not easily reproduced, and thus human technology must be developed to reach these difficult stellar conditions in order to harvest fusion energy. There are two main branches of developmental technology geared towards achieving the difficult conditions controlled nuclear fusion presents, magnetic confinement fusion (MCF) and inertial confinement fusion (ICF)[17]. Yet in both approaches barriers exist which have thwarted the efforts toward reaching fusion ignition which must be addressed through scientific discovery. Successfully reaching ignition is only the first step in the ultimate pursuit of a self sustaining fusion reactor. This work will focus on the experimental ICF configuration, and on one such inhibitor toward achieving ignition, the Rayleigh-Taylor (RT) instability. The RT instability develops on the surfaces of the fusion fuel capsules, targets, and causes nonuniform compression of the target. This nonuniform compression of the target leads to lower pressures and densities through the material mixing of fusion fuel and the capsule shell, which ultimately leads to challenges with reaching fusion ignition. The work presented here was performed utilizing the University of Chicago's FLASH code, which is a state-of-the-art open source radiation magneto-hydrodynamic (MHD) code used for plasma and astrophysics computational modeling [11]. Simulations of the RT instability are performed using FLASH in planar and cylindrical geometries to explore fundamental Rayleigh-Taylor instability evolution for these two different geometries. These geometries provide easier access for experimental diagnostics to probe RT dynamics. Additionally, the impact of externally applied magnetic fields are explored in an effort to examine if and how the detrimental instability can be controlled.
28
Skrudupis, Patrikas. "Tikrovės problema Jean'o Baudrillard'o filosofijoje." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050602_221029-28883.
Abstract:
The study deals with J. Baudrillad’s conception of reality as hyper reality. J. Baudrillad’s conception of hyper reality and the lost of referential reality is presented through the analysis of numerous writings, articles as well as critical texts. First of all, the author’s conception of simulated and non-referential reality is compared with the classical understanding of reality, which contains dualistic tension, whereas the other is nuclear and the distinctions between object/subject, true/false, real/unreal are no longer possible. Then the author of the study also brings the theme of ‘produced reality’ and mass mediated life as it is represented in J. Baudrillad’s philosophical writings. The influence of hyper reality on the practical way of life is also analyzed. Finally, the themes of non-referential language, philosophical dialogue and possibility for classical philosophy are considered.
29
Daou, Maya Mounir. "Investigation of the plate-impact method as a precursor of physical phenomena and chemical processes." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066245/document.
Abstract:
Ce manuscrit a pour but d'étudier un nouveau dispositif générateur de cavitation dont le potentiel favorable à l'intensification de réactions chimiques est évalué. Ce dispositif est constitué d'une plaque mobile qui frappe un liquide contenu dans un réacteur. L'impact génère une forte augmentation de pression dans le milieu suivi d'une dépressurisation. Nous montrons que la couche de gaz/vapeur piégée entre le piston et la surface du liquide influence les pics de pression et les fréquences générées dans le milieu. La visualisation à l'aide d'une caméra rapide montre que la dépressurisation active les sites de nucléation à l'origine des bulles de cavitation qui grandissent et implosent en générant occasionnellement des jets de grande vitesse. Nous étudions aussi la réponse de bulles préexistantes. Nous identifions un rayon de bulle critique qui dépend de la hauteur d'impact, de la pression extérieure et des caractéristiques du piston. Les bulles dont le rayon initial est supérieur à la valeur critique implosent au moment de l'impact, tandis que les petites bulles ne sont activées qu'après (sous tension). Des évolutions de pression différentes sont observées après l'impact en fonction de la présence/absence de grandes bulles. Nous étudions enfin l'oxydation du phénol en montrant que l'impact sur l'eau pure est incapable de générer des espèces radicalaires responsables de la dégradation. En ajoutant du peroxyde d'hydrogène comme oxydant, la molécule est décomposée sous certaines conditions. En général, la quantité d'oxydant requise pour déclencher une oxydation significative diminue lors de l'augmentation de l'intensité de l'impact sur lequel dépend le taux de dégradationThis manuscript aims at characterizing a new device based on a plate impact on a liquid surface to generate cavitation and evaluate its potential to induce chemical reactions. The device is composed of a reactor containing a liquid that a piston hits due to pressure difference. This impact generates a strong and uniform pressure increase in the medium followed by a depressurization. We show that the gas/vapor layer trapped between the piston and the liquid free surface influences the pressure peaks and frequencies generated in the medium. High-speed camera visualization shows that depressurization activates nucleation sites leading to bubble appearance in the solution. Bubbles expand and collapse intensively generating high velocity jets under some conditions. We also investigate the response of pre-existing bubbles. We identify a critical bubble radius that depends on the impact height, external pressure and piston’s characteristics. Bubbles with an initial radius larger than the critical one collapse at the moment of impact while smaller bubbles are only activated after it (under tension). Significant differences are observed in the pressure recordings after the impact depending on the presence/absence of large bubbles. We finally study the oxidation of phenol. We show that impacting on pure water is incapable of generating radical species responsible of the degradation. By adding hydrogen peroxide as an oxidant we show that the molecule is decomposed under certain conditions. In general, the amount of hydrogen peroxide required to initiate a significant oxidation decreases when increasing the intensity of the impact on which the degradation rate mainly depends
30
Kamolnick, Paul. "Abu Muhammad Al-Adnani’s May 21, 2016 Speech: More Evidence for Extreme Marginalization, Implosion, and the Islamic State Organization’s Certain Future as a Hunted Underground Ultra-Takfiri Terrorist Criminal Entity." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/646.
Abstract:
Excerpt: On May 21, 2016 a 31-minute audio file by Islamic State Organization (ISO) chief spokesman Abu Muhammad al-Adnani (real name: Taha Sobhi Falaha) was uploaded by the ISO’s Al Furqan Media outlet onto the internet.
31
Kamolnick, Paul. "Abu Muhammad al-Adnani’s May 21, 2016 Speech: More Evidence for Extreme Marginalization, Implosion, and the Islamic State Organization’s Certain Future as a Hunted Underground Ultra-Takfiri Terrorist Criminal Entity." Digital Commons @ East Tennessee State University, 2018. https://amzn.com/1543478824.
Abstract:
Book Summary: This work is the fourth Small Wars Journal anthology focusing on radical Sunni Islamic terrorists and insurgent groups. It covers this professional journals writings for 2016 and is a compliment to the earlier Global Radical Islamist Insurgency anthologies that were produced as Vol. I: 2007-2011 (published in 2015) and Vol. II: 2012-2014 (published in 2016) and Jihadi Terrorism, Insurgency, and the Islamic State spanning 2015 (published in 2017). This anthology, which offers well over 900 pages of focused analysis, follows the same general conceptual breakdown as the earlier works and is divided into two major thematic sectionsone focusing on Al Qaeda and Islamic state activities in 2016 and the other focusing on US-Allied policies and counterinsurgent strategies.
32
Haworth, Thomas James. "Radiation hydrodynamic models and simulated observations of radiative feedback in star forming regions." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14465.
Abstract:
This thesis details the development of the radiation transport code torus for radiation hydrodynamic applications and its subsequent use in investigating problems regarding radiative feedback. The code couples Monte Carlo photoionization with grid-based hydrodynamics and has the advantage that all of the features available to a dedicated radiation transport code are at its disposal in RHD applications. I discuss the development of the code, including the hydrodynamics scheme, the adaptive mesh refinement (AMR) framework and the coupling of radiation transport with hydrodynamics. Extensive testing of the resulting code is also presented. The main application involves the study of radiatively driven implosion (RDI), a mechanism where the expanding ionized region about a massive star impacts nearby clumps, potentially triggering star formation. Firstly I investigate the way in which the radiation field is treated, isolating the relative impacts of polychromatic and diffuse field radiation on the evolution of radiation hydrodynamic RDI models. I also produce synthetic SEDs, radio, Hα and forbidden line images of the bright rimmed clouds (BRCs) resulting from the RDI models, on which I perform standard diagnostics that are used by observers to obtain the cloud conditions. I test the accuracy of the diagnostics and show that considering the pressure difference between the neutral cloud and surrounding ionized layer can be used to infer whether or not RDI is occurring. Finally I use more synthetic observations to investigate the accuracy of molecular line diagnostics and the nature of line profiles of BRCs. I show that the previously unexplained lack of dominant blue-asymmetry (a blue-asymmetry is the expected signature of a collapsing cloud) in the line profiles of BRCs can be explained by the shell of material, swept up by the expanding ionized region, that drives into the cloud. The work in this thesis combines to help resolve the difficulties in understanding radiative feedback, which is a non–linear process that happens on small astrophysical timescales, by improving numerical models and the way in which they are compared with observations.
33
Artrip, Ryan Edward. "Virulence and Digital Culture." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/80512.
Abstract:
This dissertation is a theoretical study of the role of virality/virulence as a predominant technological term in the reproduction of social and cultural information in the digital age. I argue that viral media are not new phenomena, only the name is new. Media have always behaved as viruses; it is only when they become hyper-intensified in digital technology that their virulent function surfaces in language and culture. The project examines processes of self-replication and evolution undergone by various new media phenomena as they relate back to the global profusion of social networks, data centers, and cybernetic practices. Drawing from several contributions in media theory, political and social theory, and critical media studies, I argue that digital media have a hyper-intensifying effect on whatever objects, subjects, or realities they mediate or represent; thus networked societies are virulently swarmed by their own signs and images in information. Through an examination of three primary categories of digital proliferation—language, visuality, and sexuality—I situate digital culture in a framework of virulence, arguing that the digital may be best understood as an effect of cultural hyper-saturation and implosion. I argue that virulent media networking processes come to constitute a powerful cybernetic system, which renders the human subject a mere function in its global operations. Lastly, I begin to develop a political critique of cybernetics, claiming that the proliferation of information, digital media, and communicative/representational technologies in the contemporary world emerges through an intensified ideological, economic, social, cultural, and metaphysical framework of productivism. This intensification engenders a system, or series of communicational circuits, whereby all techno-subjective activities are strategically stimulated, networked, recorded, and algorithmically appropriated to strengthen and reproduce 1) a global productivist system of cybernetics; 2) The material and ideological conditions for such a system to exist and thrive; 3) limitless virtual and digital production.Ph. D.
34
Capuano, Marion. "Simulations numériques d'écoulements diphasiques compressibles, visqueux et conductifs à l'aide de schémas aux différences finies d'ordre élevé." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC016/document.
Abstract:
Ce travail de thèse porte sur le simulation d’écoulements diphasiques compressibles, visqueux et conductifs, à l’aide de schémas numériques aux différences finies centrées d’ordre élevé. Pour cela, les équation utilisées sont les équations de Navier-Stokes complétées de deux équations d’advection décrivant l’interface et d’une équation permettant d’estimer la température au sein d’un liquide et d’un gaz. Elles sont résolues à l’aide de méthodes numériques conservatives précédemment développées pour l’aéroacoustique, adaptées dans la présente étude à la simulation d’écoulements diphasiques. Les choix des équations et des méthodes numériques sont validés à l’aide de divers cas test monodimensionnels proposés dans la littérature. Les résultats obtenus sont en accord avec les solutions analytiques ou de référence. Deux écoulements 2D composés de deux gaz sont ensuite considérés. Le premier cas concerne l’instabilité de Richtmyer-Meshkov qui se développe à l’interface entre de l’air et du SF6. Le second cas porte sur une bulle cylindrique remplie d’hélium ou de R22 impactée par une onde de choc plane se propageant dans l’air. Pour ces deux écoulements, une étude de convergence de maillage est effectuée et les solutions numériques sont comparables aux données expérimentales de la littérature. L’influence du nombre de Reynolds sur la déformation de l’interface de la bulle d’hélium est également montrée. Enfin, l’implosion d’une bulle d’air dans l’eau est étudiée. Dans un premier temps, l’implosion sphérique de la bulle suite à son interaction avec une onde de pression convergente est simulée. Les résultats sont en bon accord avec les solutions prédites par le modèle de Rayleigh-Plesset. L’influence de l’épaisseur initiale de l’interface et de la conductivité thermique est montrée. Dans un second temps, l’implosion non sphérique d’une bulle proche d’un mur et impactée par une onde de choc plane est considérée. La pression imposée sur le mur et la température au sein de l’écoulement sont quantifiées. Enfin, une étude de l’effet de la distance initiale entre le mur et la bulle sur l’implosion est menéeThis PhD work concerns the simulation of compressible, viscous and conductive two-phase flows, using high-order centered finite-difference schemes. The equations governing two-phase flows are the Navier-Stokes equations in conjunction with two advection equations governing the interface and one equation allowing to estimate the temperature within a liquid and a gas. These are solved using conservative numerical methods which are validated from the resolution of various 1D test cases taken from the literature. The results obtained are in good agreement with the analytical or reference solutions. Then, two 2-D flows composed of two gases are considered. The first case concerns the Richtmyer-Meshkov instability developping at the interface between air and SF6. The second case deals with a cylindrical bubble filled with helium or R22 which is hit by a plane shock wave travelling through air. For these two flows, a grid convergence study is conducted and the numerical solutions compare well with the experimental data of the literature. The effect of the Reynolds number on the deformation of the bubble interface is also shown. Finally, the collpase of an air bubble in water is studied. Firstly, the spherical collapse of the bubble due to its interaction with a spherical converging shock wave is simulated. The results are in good agreement with the solutions predicted by the Rayleigh-Plesset model. The effect of the initial interface thickness and the thermal conductivity on the collapse is investigated. Secondly, the non-spherical collapse of a bubble near a wall impacted by a plane shock wave is considered. The pressure imposed on the wall and the temperature within the flow are quantified. Finally, the influence of the initial stand-off distance between the wall and the bubble is examined
35
Wang, Juntao. "Coronal implosions in solar eruptions and flares." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/31010/.
Abstract:
Coronal implosions - the convergence motion of plasmas and entrained magnetic field in the corona due to a reduction in magnetic pressure - can help to locate and track sites of magnetic energy release or redistribution during solar flares and eruptions. Although this conjecture was proposed almost two decades ago, observa- tions of such phenomena are still rare, and even our understanding of it is far from complete. In this thesis, following an introduction to the background and techniques used, we first generalise the implosion idea based on its spirit concerning about the relationship between magnetic energy release and field shrinkage, which allows us to unite and explain three different phenomena, that is, peripheral implosions, inflows and dipolarisations, using only one single principle. Previous observations of apparent contractions in the periphery of active regions are mainly in a face-on state, which cannot exclude the possibilty of field inclining instead of a real contraction as the cause. This then motivates us to study an excellent event observed near the solar disk center, and evidence from both observations and coronal magnetic field extrapolations is found to support the implosion idea. In a unification of three main concepts for active region magnetic evolution implied by the observation, namely the metastable eruption model, the implosion conjecture, and the standard “CSHKP” flare model, the contraction of the field is explained by the removal of the erupting filament originally underneath rather than local magnetic energy dissipation in a flare invoked by previous authors. However, the observation and extrapolation results in the work above are indirect and still not adequate, as the complex structure of the solar atmosphere, and the simplified assumption and preprocessing in the extrapolation may lead us to a wrong conclusion. Thus in the following four carefully seleted events with the continuously contracting loops in an almost edge-on geometry are for the first time investigated, demonstrating the reality of contraction of field lines in the global coronal dynamics unambiguously. Meanwhile, two categories of implosions, flare- and eruption-driven, are identified, which could be interpreted well in the framework of the implosion conjecture, disproving other authors’ proposal. We also revisit one of the original assumptions of the implosion conjecture which may fail when a heavily-mass-loaded filament is involved, and in this case implosions can be suppressed, possibly served as an alternative explanation for their observational rarity. In the end, we move on to one of the generalised implosion types, i.e., the inflow, and also study other reconnection flows associated with it. Intrinsic to the well- accepted reconnection picture of a solar eruptive event, particularly in the standard model for two-ribbon flares (“CSHKP” model), are an advective flow of magnetized plasma into the reconnection region, expansion of field above the reconnection region as a flux rope erupts, retraction of heated post-reconnection loops, and downflows of cooling plasma along those loops. However, the evidence of these flows is still circumstantial and rare. We report in this work on a unique set of SDO/AIA imaging and Hinode/EIS spectroscopic observations of a flare in which all four flows are present simultaneously. This also includes spectroscopic evidence for a plasma upflow at the edge of the active region claimed by previous authors, which we suggest decomposing into two components, one associated with open field at quasi- separatrix layers, the other with large-scale expanding closed arcade field. The reconnection inflows are symmetric, and consistent with fast reconnection, and the post-reconnection loops show a clear cooling and deceleration as they retract. Unlike previous events observed at the solar limb which are obscured by complex foregrounds and thus makes the relationship between the plasma flows, the flare ribbons, cusp field and arcades formed in the lower atmosphere difficult to interpret, the disk location and favorable perspective of this event studied here have removed these ambiguities giving a clear picture of the reconnection dynamics. We end with a brief chapter summarizing the thesis and suggesting some future work.
36
Kemp, Andreas J. "Magnetized cylindrical implosions driven by heavy ion beams." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962128287.
37
Town, Richard Paul John. "Three dimensional hydrodynamical simulations of laser driven implosions." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46585.
38
Krispinsson, Charlotta. "Ung, samtida och postmodern : En studie av det svenska konstfältet under 1980-talet utifrån Lars Nilssons konstnärskap." Thesis, Södertörn University College, School of Culture and Communication, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-3311.
Abstract:
The aim of this thesis is to study the Swedish art field during the 1980s, from the perspective of the artistic production of Lars Nilsson. During this decade he became one of the most well known young artists associated with postmodernism.
The thesis is divided into three parts, where the first part examines different influences and aspects of the art of Lars Nilsson, as well as the contexts he was a part of. This is performed through a chronological as well as a categorizing presentation, based upon different exhibitions where Nilsson participated during the 1980s.
In the second part the subject is the Swedish art field, and how Lars Nilsson came to be part of a a new established category of a young generation of artists, mostly born in the 1950s, who were associated with youth, postmodernism and contemporaneousness. This part also puts attention to the importance of Lars Nittve, then art critic and curator, in introducing postmodernism, as well as establishing this new categorization of artists in Sweden.
The last part of the thesis studies four different group exhibitions, and how they all exemplify how "a younger generation of artists" were to be connected with notions of postmodernism and contemporaneousness through curatorial practice. Lars Nilsson participated at the thirst three of these exhibitions. This is followed with a last group exhibition, where the idea of younger artists as the most contemporary were to be questioned. The thesis ends with a summary and a discussion.
39
Arias, Beatriz. "Grupos consonánticos cultos en el siglo XVI y XVII: ¿representación fonémica o norma gráfica?" Pontificia Universidad Católica del Perú, 2012. http://repositorio.pucp.edu.pe/index/handle/123456789/100139.
Abstract:
Este trabajo analiza la representación gráfica de algunos grupos consonánticos “cultos” del español colonial mexicano en documentos, cartillas y ortografías de los siglos XVI y XVII. A partir de este estudio se ha podido registrar varios tipos de representación gráfica de las consonantes en posición implosiva, muchas de las cuales son similares a las que se registran en el habla popular de esta zona. La presente investigación advierte, por una parte, que el estudio gráfico de documentos novohispanos ofrece pistas sobre la “realización” de los grupos cultos de la época en cuestión. Por otra parte, concluimos que muchos de estos fenómenos que ocurren en los contornos de la sílaba, en concreto en la coda, son bastante parecidos a los analizados en el habla popular de los mexicanos del siglo XXI.This paper examines the graphic representation of some consonant groups considered educated in the colonial Mexican Spanish in documents, charts and orthographies from XVI and XVII centuries. As of this work, it has been possible the registration of some different types of graphic representations for the consonants in implosive position, they are similar to the ones registered in the popular language of this zone. This research offers two striking points. On one side, it demonstrates that the graphic study of novo-Hispanic documents provides clues about the “realization” of the educated groups from the period under scrutiny. On the other hand, I conclude that many of these phenomena occur in the outlines of the syllable, specifically in the coda, and that they are very similar to those found in the popular speech of Mexicans from the XXI.
40
Bland, Simon Nicholas. "Plasma dynamics in aluminium wire array Z-pinch implosions." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342345.
41
Savage, Maura Christine. "Studies of laser compression of high aspect ratio DT filled shells." Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317484.
42
El, Rafei Moustassem. "Three-Dimensional Numerical Simulations of Shock-Induced Turbulent Mixing in Spherical Implosions." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/28607.
Abstract:
Compressible turbulent mixing evolving from Richtmyer–Meshkov and Rayleigh–Taylor instabilities and Bell–Plesset effects has been investigated using carefully designed high-resolution spherical algorithms and implicit large eddy (ILES) simulations of fundamental spherical implosion problems. Multimode narrowband and broadband initial perturbations consisting of spherical harmonics and multimode cosine perturbations are investigated considering a high Atwood number (At = 0.9) setup and a moderate convergence ratio Cr = 3.6. Several integral quantities, mixedness parameters and turbulence statistics are presented to provide a detailed understanding of the mixing process and the effect of the initial spectrum of perturbations on the subsequent mixing. Furthermore, this research is one of the few efforts to examine turbulent transport and budgets of turbulent kinetic energy, turbulent mass flux and density self-correlation, considering high-Atwood implosion configurations and different initial perturbations spectra. The budgets are investigated while also quantifying the contribution from numerical dissipation and diffusion to the transport equations. Different analytical mix models have been developed for the prediction of mixing layer growth and amount of mixing that occurs. The first model, denoted as the Bell-Plesset model, is an extension of a single mode perturbation growth model, that is based on small-amplitude and linear growth assumptions, to multimode perturbations and reshocks. Bubble and spike growth is also modelled using a Buoyancy-Drag (BD) approach to which modifications were applied to introduce an effective length scale in the drag term to consider the initial conditions and early stages of the mixing process. The BD model was adapted to the spherical implosion case considered here and the effect of geometric convergence was also added to the model.
43
Weinwurm, Marcus. "Cylindrically convergent implosions of metal liners for quasi-isentropic compression of deuterium." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/23296.
Abstract:
To date our understanding of strongly coupled, degenerate plasmas is incomplete. In particular considerable disagreement exists between theories of hydrogenic matter (HM) at pressures greater than 100 gigapascals (GPa) and temperatures below 3 electronvolts (eV). The predicted transition of fluid molecular hydrogen to a metallic atomic liquid has large implications for models of the interior structure and evolution of gas giants. Experimental confirmation of this transition is still pending. Furthermore, the properties of deuterium-tritium in this regime are of great interest to inertial confinement fusion. In this thesis we propose a scheme that can create strongly coupled, degenerate hydrogenic plasmas at terapascal (TPa) pressures on pulsed power machines. Our results show that this can be achieved by initiating cylindrically converging isentropic flow of sample material inside a metal liner. The liner acts as a pusher that drives a predefined compression of the fill, which is obtained by constructing an asymptotically self-similar implosion of cryogenically condensed HM. An empirical model that gives the required pulse shape for recreating this implosion inside the liner is introduced. Results of magnetohydrodynamic simulations demonstrate that a peak current of 10.8 megaamperes (MA) is sufficient for assembling nearly uniform HM at a stagnation pressure of 13 TPa and at temperatures of approximately 1.5 eV. A study of the stability of the implosion to imperfections of the liner's surface finds that liner-driven isentropic compression of hydrogen is robust to magneto-Rayleigh-Taylor growth for sufficiently thick liners. Since the methods in this work are readily adapted to a range of materials, an experimental realization could significantly extend our knowledge of degenerate, strongly coupled plasmas in general. Finally, we broaden our focus to the compression of the metal liner itself. Potential advantages of reducing shock heating and thereby increasing the degeneracy of liner material during a magnetized liner inertial fusion implosion are discussed.
44
Johns, Heather M. "Constrained analysis of Ti line absorption spectra in OMEGA direct-drive implosions." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1456409.
45
Xavier, Christine Fernandes. "Modelos de implosão de bolhas esféricas para sonoluminescência." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277081.
Abstract:
Orientador: Roberto Antonio ClementeTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"
Made available in DSpace on 2018-07-27T10:17:15Z (GMT). No. of bitstreams: 1 Xavier_ChristineFernandes_D.pdf: 1987811 bytes, checksum: c93687e4e77aad2b24119978aedca0f2 (MD5) Previous issue date: 2000
Resumo: Os processos de relaxação associados aos graus de liberdade vibracional, de dissociação e ionização em bolhas de gás diatômicos e monoatômicos em SBSL (sonoluminescência de uma única bolha) são analisados através da elaboração de modelos hidrodinâmicos apropriados onde o efeito da condução térmica na interface bolha-líquido é incluído de maneira auto-consistente. Simulações numéricas dos diversos processos de relaxação permitiram caracterizar a dinâmica de tais bolhas, além de permitir a obtenção dos valores associados às frações dissociadas e ionizadas dos gases no interior da cavidade. Em conexão com a análise do processo de ionização, um modelo para a emissão de radiação em SBSL é construído, suas conseqüências sendo analisadas e discutidas. O efeito da condução térmica na interface bolha líquido é também considerado
Abstract: We analyze, under appropriate hydrodynamical models, the processes of relaxation associated to vibrational degrees of freedom, dissociation and ionization of diatomic and monoatomic gas bubbles in the sonoluminescence phenomena. Numerical simulations allowed to characterize the dynamics of such bubbles and to infer values for dissociated and ionized fractions of gases that are present inside the cavity. In connection to an analysis of ionization process, we have constructed a model for the emission of SBSL (single bubble sonoluminescence) radiation whose main features are discussed. The effect of thermal conduction at the bubble-liquid interface is also considered.
Doutorado
Física
Doutor em Ciências
46
Casey, Daniel Thomas. "Diagnosing inertial confinement fusion implosions at OMEGA and the NIF Using novel neutron spectrometry." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76813.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 139-148).
A novel neutron spectrometer, called the Magnetic Recoil Spectrometer (MRS), was designed, built, and implemented on the OMEGA laser facility and the National Ignition Facility (NIF) to measure the neutron spectra from inertial confinement fusion (ICF) implosions. Using the MRS, the down-scattered neutron (DSn) spectrum has been used to infer the areal density ([rho]R) of ICF implosions for the first time. The DSn technique is essential for diagnosing high [rho]R (>180mg/cm²) cryogenic deuterium-tritium (DT) implosions, where most other methods fail. The MRS has helped to guide the cryogenic campaign toward the highest [rho]Rs ever achieved at OMEGA. In addition, the MRS is currently being used to diagnose the DSn spectrum from cryogenic implosions at the NIF during the beginning phases of the National Ignition Campaign (NIC). MRS data have already been essential for tuning these implosions to the highest [rho]Rs ever achieved in an ICF implosion (>1 g/cm²), and thus for guiding the NIC toward the realization of thermonuclear ignition. The first measurements of the T(t,2n)⁴He (TT) neutron spectrum in DT implosions at OMEGA have also been conducted using the MRS. The TT-neutron (TTn) spectrum was measured at low reactant central-mass energies of ~23 keV. The results from these measurements indicate that the TT reaction proceeds primarily through the direct three-body reaction channel, which is in contrast to the results obtained in higher energy accelerator experiments. Measurements of the TTn and DD proton yields were also conducted and compared to the DT neutron yield in DT implosions. From these measurements, it is concluded that the DD yield is anomalously low and the TTn yield is anomalously high, relative to the DT yield. These results have been explained by a stratification of the fuel in the core of an ICF implosion.
by Daniel Thomas Casey.
Ph.D.
47
Rinderknecht, Hans G. "Studies of non-hydrodynamic processes in ICF implosions on OMEGA and the National Ignition Facility." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99291.
Abstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references.
Ion kinetic effects are expected to modify plasma dynamics when ion mean-free-paths and collision times become comparable to the scale sizes of the plasma. Such conditions arise during the shock convergence phase of inertial confinement fusion (ICF) implosions, when they may modify the compression and ignition of the fuel from the evolution predicted by main-line hydrodynamic simulations. Kinetic plasma dynamics relevant to ICF implosions have been studied experimentally using strongly-shocked ICF implosions containing multiple ion species, and diagnosed using both new and established nuclear diagnostics and techniques. Implosions of deuterated plastic shells filled with equivalent-mass-density mixtures of deuterium and 3He gas have demonstrated for the first time ion diffusive mixing of the fuel and shell material through observations of the D3He-proton and DD-neutron yields. Implosions with initially separated populations of D in the shell and 3He in the gas produced D3He-fusion from the mixed region on par with implosions filled with equimolar D3 He fuel and an order of magnitude larger than is produced by hydrodynamic models of fuel/shell mix. An extensive survey of kinetic mix- and yield-generation mechanisms and their signatures in nuclear diagnostics establishes ion diffusion as the best candidate to explain these observations. A series of shock-driven implosions of D3He-gas filled glass shells has demonstrated two signatures of significant ion kinetic plasma effects for the first time: ion thermal decoupling and ion species separation. In low-initial gas density implosions, for which the thermal equilibration times were much longer than the burn duration, the burn-averaged ion temperatures were observed to be anomalously invariant with ion species fraction. This behavior has been shown to signify thermal decoupling of the D and 3He ion species between the shock- and fusion-phases. Comprehensive nuclear diagnostic information has been used to infer the burn-averaged deuterium fraction, which was reduced from the expectations of hydrodynamic simulations, the first direct measurement of species separation in an ICF implosion. When corrected for these effects, simulations agreed better with the observed anomalously low nuclear yields. These results have demonstrated the significant modification of ICF-relevant shocked plasmas by kinetic plasma dynamics, motivating further experimental and theoretical investigation of these highly dynamic and poorly understood regimes.
by Hans G. Rinderknecht.
Ph. D.
48
Schwartz, Brook-Eden 1979. "Imaging the burn region of laser driven implosions on OMEGA using the proton core imaging spectroscope." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29443.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2004.Includes bibliographical references (p. 143).
The first measurements of the nuclear burn region of OMEGA implosions have been made with the Proton Core Imaging Spectroscope (PCIS). Using CR-39 nuclear track detectors, PCIS applies the technique of penumbral imaging to measure the radial profile of D-D and D-3He protons produced by implosions of D2-3He-filled capsules. For capsules with 20 [mu]m-CH shells, images of D-3He protons resulted in Gaussian profiles with an average l/e radius of [approx.]35 [mu]m. Gaussian profiles inferred from the D-3He protons and D-D protons produced by implosions of 2 [mu]tm SiO2-shell capsules had average l/e radii of 60 [mu]m and 94 [mu]m, respectively. [mu]m and 94 [mu]m, respectively.
by Brook-Eden Schwartz.
S.M.
49
Sinenian, Nareg. "Fast-ion spectrometry of ICF implosions and laser-foil experiments at the omega and MTW laser facilities." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80661.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2013.Cataloged from PDF version of thesis. Page 224 blank.
Includes bibliographical references.
Fast ions generated from laser-plasma interactions (LPI) have been used to study inertial confinement fusion (ICF) implosions and laser-foil interactions. LPI, which vary in nature depending on the wavelength and intensity of the driver, generate hot electrons with temperatures ranging from tens to thousands of kilo-electron-volts. These electrons, which accelerate the ions measured in this work, can be either detrimental or essential to implosion performance depending on the ICF scheme employed. In direct-drive hot-spot ignition, hot electrons can preheat the fuel and raise the adiabat, potentially degrading compression in the implosion. The amount of preheat depends on the hot-electron source characteristics and the time duration over which electrons can deposit energy into the fuel. This time duration is prescribed by the evolution of a sheath that surrounds the implosion and traps electrons. Fast-ion measurements have been used to develop a circuit model that describes the time decay of the sheath voltage for typical OMEGA implosions. In the context of electron fast ignition, the produced fast ions are considered a loss channel that has been characterized for the first time. These ions have also been used as a diagnostic tool to infer the temperature of the hot electrons in fast-ignition experiments. It has also been shown that the hot-electron temperature scales with laser intensity as expected, but is enhanced by a factor of 2-3. This enhancement is possibly due to relativistic effects and leads to poor implosion performance. Finally, fast-ion generation by ultra-intense lasers has also been studied using planar targets. The mean and maximum energies of protons and heavy ions has been measured, and it has been shown that a two-temperature hot-electron distribution affects the energies of heavy ions and protons. This work is important for advanced fusion concepts that utilize ion beams and also has applications in medicine.
by Nareg Sinenian.
Ph.D.
50
Kurebayashi, Shinya 1976. "Using Nuclear data and Monte-Carlo techniques to study areal density and mix in D² inertial confinement fusion implosions." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29369.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references.
Measurements from three classes of direct-drive implosions at the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] were combined with Monte-Carlo simulations to investigate models for determining hot-fuel areal density ([rho]Rhot) in compressed, D2-filled capsules, and to assess the impact of mix and other factors on the determination of pRhot. The results of the Monte-Carlo calculations were compared to predictions of commonly used models that use ratios of either secondary D3He proton yields or secondary DT neutron yields to primary DD neutron yields to provide estimates [rho]Rhot or [rho]Rhot,n, respectively, for pRhot. For the first class of implosions, where [rho]Rhot is low (=/< 3 mg/cm2), [rho]Rhot,p and [rho]Rhot,n often agree with each other and are often good estimates of the actual [rho]Rhot. For the second class of implosions, where [rho]Rhot is of order 10 mg/cm2, pRhot,p often underestimates the actual value due to secondary proton yield saturation. In addition, fuel-shell mix causes pRhot,p to further underestimate, and [Rho]Rhot,n to overestimate, [rho]Rhot. As a result, values of [Rho]Rhot,p and [Rho]Rhot,n can be interpreted as lower and upper limits, respectively. For the third class of implosions, involving cryogenic capsules, secondary protons and neutrons are produced mainly in the hot and cold fuel regions, respectively, and the effects of the mixing of hot and cold fuel must be taken into account when interpreting the values of [rho]Rhot,p and pRhot,n. From these data sets, we conclude that accurate inference of [rho]Rhot requires comprehensive measurements in combination with detailed modeling.
by Shinya Kurebayashi.
S.M.