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Horton, Timothy Scott. "COLLISIONAL AND RADIATIVE RELAXATION IN SODIUM DIMER AND ARGON ATOM COLLISIONS". Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1480693544113525.
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Kantak, Advait Ashok. "Wet particle collisions". Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p3190381.
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Nesbitt, Brian. "Heavy-particle collisions". Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301028.
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Harris, Allison Lynn. "Fully differential cross sections for four-body scattering processes". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Harris_09007dcc806c3b59.pdf.
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Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 25, 2009) Includes bibliographical references (p. 84-92).
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Planchette, Carole. "Collisions de gouttes asymétriques". Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00647892.
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Dans cette thèse expérimentale, on s'intéresse aux collisions de gouttes mettant en jeu des interfaces asymétriques, soit deux gouttes constituées de liquide différent ou des gouttes de taille différente et recouvertes (ou non) d'une couche de particules hydrophobes. Dans une première partie, on étudie les collisions de gouttes de liquide immiscible. L'asymétrie de tels systèmes repose alors sur le contraste des propriétés des deux liquides : la tension de surface, la viscosité et la densité. Le résultat de ces collisions est une encapsulation totale d'un liquide par un autre ou une encapsulation suivie d'une fragmentation. On s'attache à décrire les régimes observés et à établir des lois permettant de prédire les limites de fragmentation de l'objet obtenu. La seconde partie est consacrée aux interfaces couvertes de particules hydrophobes. Pour ces systèmes, l'asymétrie réside à la fois dans la présence des particules sur une interface et pas sur l'autre et dans le contraste de taille entre les objets étudiés. Ainsi, on considère l'impact entre une petite goutte (recouverte ou non de particules) et une très grosse goutte (recouverte ou non de particules). On caractérise tout d'abord les propriétés mécaniques de ces interfaces via la propagation d'ondes de surface, notamment en terme de tension de surface effective et de module de courbure. Puis, on sonde, dans différentes situations d'impact, la robustesse de ces objets afin d'évaluer la capacité de ces couches particulaires à prévenir la coalescence
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McGuinness, Philip. "Electron-ion elastic collisions". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268236.
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Copeland, Fiona B. M. "Low energy rearrangement collisions". Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318881.
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McAlinden, Mary Trea. "Atomic collisions involving positrons". Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317480.
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Grishkevich, Sergey. "Ultracold collisions in traps". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16098.
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Die ultrakalte Atom- und Molekülephysik, zu welcher man zum Beispiel bei der Bose-Einstein-Kondensation von verdünnten Gasen Zugang hat, wurde untersucht. In solchen Systemen dominieren Zwei-Körper-Stöße und ihre detaillierte Untersuchung ist eines der zentralen Themen dieser Arbeit. Diese wurden durchgeführt unter Berücksichtigung von elementaren chemischen Reaktionen, Photoassoziation und magnetischen Feshbach-Resonanzen. Weiterhin wurden Untersuchungen von Atomen in optischen Gittern durchgeführt. Die Viel-Teilchen-Systeme wurden nicht nur mit dem üblichen mean-field Ansatz behandelt, sondern auch darüber hinausgehend, um die voll korrelierte Bewegung zu simulieren.The ultracold atomic and molecular physics as it is accessible, e.g., in Bose-Einstein condensates of dilute gases was investigated. In such systems two-body collisions are dominant and their detailed study is one of the central topics of this work. They were done considering elementary chemical reactions as photoassociation, and magnetic Feshbach resonances. Additionally, studies of atoms in optical lattice sites were carried out. The many-body systems were not only considered within the usually adopted mean-field approach but also beyond that in order to simulate the fully correlated motion.
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O'Connor, Daryl John. "Atomic collisions with surfaces". Thesis, Canberra, ACT : The Australian National University, 1997. http://hdl.handle.net/1885/144473.
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Braud, Isabelle. "Collisions agrégats-molécules : attachement, fragmentation, nanocalorimétrie". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30187/document.
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Le dispositif expérimental original développé à Toulouse permet de contrôler les collisions entre un agrégat chargé, libre, thermalisé, sélectionné en masse et des molécules. Il permet d'étudier l'attachement de la molécule sur l'agrégat ou la fragmentation induite par collision. Afin de mieux comprendre les processus d'attachement d'une molécule sur un agrégat, nous avons mesuré les sections efficaces d'attachement de molécules d'alcool, méthanol et éthanol, sur des agrégats d'alcool. Nous avons pu observer un comportement similaire aux agrégats d'eau, c'est à dire des sections efficaces d'attachement inférieures à la section efficace géométrique aux petites tailles qui tendent vers cette section géométrique quand la taille augmente. Ce comportement avait été attribué pour l'eau à un effet dynamique. Ce modèle dynamique peut être étendu avec un bon accord qualitatif aux agrégats d'alcools. Les processus d'attachement et de fragmentation nous permettent de réaliser des expériences de nanocalorimétrie. Nous avons pu déterminer les capacités calorifiques et les températures de transition de phase dans des agrégats d'eau protonés (H2O)nH+, qui viennent compléter les mesures effectuées sur les agrégats déprotonés (H2O)n-1OH-. La nature de la transition est discutée. Un troisième volet de cette thèse concerne la fragmentation induite par collision de molécules d'intérêt biologique : l'uracile protoné, isolé ou hydraté. Nous avons observé les différentes voies de fragmentation de l'uracile protoné. L'influence du nombre de molécules d'eau hydratant la molécule d'uracile sur le spectre de fragmentation est liée à l'affinité protonique des constituants et à la structure de l'agrégatThe experimental set-up developed in Toulouse enables to control collisions between a charged thermalised mass-selected free cluster and molecules. Processes of attachement of the molecule onto the cluster and collision induced fragmentation can be studied. In order to better understand the process of attachment of a molecule onto a cluster, we have measured attachment cross-sections of alcohol molecules, methanol and ethanol, onto alcohol clusters. We have observed a similar behaviour as the one observed with water clusters, that is attachment cross-sections that are lower than the geometrical cross-section at small sizes and that converge to this geometrical cross-section at bigger sizes. This behaviour had been assigned to a dynamical effect in the case of water. This dynamical model can be extended with a good qualitative agreement to alcohol clusters. Processes of attachment and fragmentation enable to realise nanocalorimetry measurements. We have determined heat capacities and transition temperatures for protonated water clusters (H2O)nH+. They complete measurements already done for deprotonated water clusters (H2O)n-1OH-. The nature of the phase transition is discussed. The last part of this dissertation concerns collision induced fragmentation for molecules that has some biological interest : protonated uracil, bare or hydrated. Fragmentation pathways of the protonated uracil molecule has been observed. The influence of the number of water molecules on the fragmentation pattern of solvated uracil is linked to the proton affinity of the constituants and to the cluster structure
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Alami, Rachad. "Contribution à l'étude de la dynamique des mécanismes très dissipatifs entre noyaux lourds". Paris 11, 1986. http://www.theses.fr/1986PA112326.
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Franck, Martin, i Roos Malin Holm. "COLLISIONS IN ICE : A STUDY OF COLLISIONS INVOLVING SWEDISH ICEBREAKERS IN THE BALTIC SEA". Thesis, Linnéuniversitetet, Sjöfartshögskolan (SJÖ), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-25468.
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This study was conducted with the purpose of furthering the knowledge of collisionsinvolving Swedish icebreakers in the Baltic Sea. It strived to identify the causes and directeffects of this type of collision. It also sought to establish if regulations and operationalguidelines, governing Swedish icebreakers and icebreaker assistance, were sufficient and ifthey were being adhered to.The method used to accomplish this was a qualitative literature study of all data regardingSwedish icebreaker collisions from the archives of the Swedish Maritime Administration andthe Swedish Transport Agency. Several accident investigation authorities from around theworld assisted in developing a method for processing the raw data.Having processed and examined the data the prevalence of different causes contributing to thecollisions could be established. All collisions occurred during icebreaker assistance. It wasfound that the all encompassing cause of the collisions was the difficulties of evaluating theice conditions and the behavior that difficult ice conditions necessitated the vessels to adopt.It was further made clear that the direct effects for the vessels, their crew and the environmentwere of limited severity. It was also concluded that the regulations and operational guidelinesgoverning Swedish icebreaker assistance, were generally being adhered to, and weresatisfactory in enabling a sufficiently safe and effective icebreaker assistance service.Denna studie genomfördes i syfte att utöka den akademiska kunskapen om kollisioner sominvolverar svenska isbrytare i Östersjön. Den ämnade identifiera orsakerna och de omedelbaraeffekterna av dessa kollisioner. Vidare sökte den fastslå huruvida regelverk och riktlinjer förden svenska isbrytartjänsten var tillräckliga och om de efterlevdes.Studien genomfördes som en kvalitativ litteraturstudie av all data, med anknytning tillisbrytarkollisioner, som fanns tillgänglig i Sjöfartsverkets och Transportstyrelsens arkiv. Ettflertal utländska myndigheter som utreder olyckor assisterade vid framtagandet av modellenför bearbetning av datan.Efter att ha bearbetat och undersökt datan kunde förekomsten av olika bidragande orsaker tillisbrytarkollisionerna slås fast. Alla kollisioner inträffade under isbrytarassistans. Det stodklart att den övergripande orsaken var svårigheten i att utvärdera isförhållandena och deåtgärder fartygen tvingas vidta för att kunna ta sig fram genom isen. Vidare fastslogs att deomedelbara effekterna, för såväl fartyg som besättning och miljö, inte var förödande utan avbegränsad karaktär. Det fastslogs även att de regelverk och riktlinjer som styr den svenskaisbrytarverksamheten överlag efterlevdes och var tillräckliga för att säkerställa entillfredställande säker och effektiv isbrytartjänst.
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Schönning, Karin. "Meson production in pd collisions". Doctoral thesis, Uppsala universitet, Kärn- och partikelfysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-100786.
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Meson production in proton-deuteron collisions has been studied using the WASA detector facility at the CELSIUS storage ring in Uppsala. Data were obtained at two different beam energies, 1360 MeV and 1450 MeV, slightly above threshold for η and ω mesons. The differential cross sections of pd → 3He ω constitute the first measurements of this reaction covering the whole angular range. The ω angular distributions are isotropic at 1360 MeV but have strong forward and backward enhancements at 1450 MeV. Theoretical calculations using a two-step model fail to reproduce the shapes of the angular distributions and underestimate the total cross sections. The tensor polarisation of the ω meson has been derived from the measured angular distributions of the ω decay products. The π+ π- π0 and the π0 γ decay channels gave consistent results, showing that the ω meson is produced unpolarised at both energies. This is in contrast to a recent MOMO measurement which showed that the Φ meson is produced almost completely polarised in the pd → 3HeΦ reaction. Different production dynamics of ω and Φ mesons close to threshold raises the question whether the Okubo-Zweig-Iizuka (OZI) rule is applicable in low-energy nucleon-nucleon reactions. The angular distributions of the η meson produced in the pd → 3He η reaction are strongly enhanced for forward going η mesons at both energies. The σ(pd → 3He π+ π- π0 )/σ(pd → 3He π0 π0 π0 ) ratio has been measured and discussed in terms of isospin amplitudes. A rough estimate of the pd → 3He π0 π0 π0 π0 cross sections has also been obtained and the pd → 3He η π0 reaction has been studied for the first time near threshold.
15
Diehl, Markus. "Diffraction in electron-proton collisions". Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/265482.
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Subject of this thesis is diffractive collisions of electrons and protons, i.e. collisions wher~ the proton remains intact or is slightly excited, and loses only a small fraction of its initial energy. Such processes can be described by the exchange of a pomeron, which is well-known from the phenomenology of highenergy hadron scattering but far from being understood in the framework of quantum chromodynamics. We use the simple model of Landshoff and Nachtmann, where the pomeron is approximated by two nonperturbative gluons, to calculate the cross section for diffractive production of a quark-antiquark pair from a real or virtual photon. This allows us to give detailed predictions for diffractive electro- or photoproduction of a jet pair, for diffractive charm production, and for the inclusive cross section in diffractive deep inelastic scattering at not too large masses of the diffractive system. For the latter we find rather good agreement with the data taken at the HERA collider, taking into account the uncertainties of our calculation. We then turn our attention to azimuthal correlations in diffractive scattering. The dependence of the electron-proton cross section on the angle between the lepton plane and some direction in the hadronic final state has a simple relation with cross sections and interference terms of the photon-proton subprocess for definite photon helicity. Its measurement can be used to constrain the cross section for longitudinally polarised photons. We compute the distribution of the azimuthal jet angle in diffractive dijet production in the Landshoff-Nachtmann model and find that useful bounds on the longitudinal cross section for such events might be obtained from its measurement. Going further we extend our calculation of quark-antiquark production to finite squared momentum transfer from the proton. This enables us to investigate the distribution of another important azimuthal angle, that of the scattered proton, which contains information about the helicity of the pomeron. The last part of this thesis is devoted to the phenomenological pomeron model of Donnachie and Landshoff. When applied to diffractive quark-antiquark production it violates electromagnetic gauge invariance. We suggest a prescription to deal with this problem and compare the results we then obtain with those of the Landshoff-Nachtmann model. We find remarkable similarities between the two models, but they also show important differences, especially in details of kinematical distributions.
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Nagy, Jozsef Bordas. "Kilovolt collisions of small ions". Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/21086.
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O'Rouke, Sheelagh Francesca Camille. "Theory of ion-atom collisions". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334486.
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McSherry, D. M. "Ionization in ion-atom collisions". Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368567.
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Turrell, Yvonne. "Grip force adjustments in collisions". Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368433.
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Agg, Philip James. "Rotational excitation in molecular collisions". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358317.
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Cooke, Andrew William. "Electronic excitation in molecular collisions". Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/12002.
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This thesis concerns the study of electronic excitation in ion/atom-molecule collisions. An extensive review of the subject is given first. At high energies, the quasidiatomic correlation diagram, that is so useful in the interpretation of atomic inelastic collisions, can also be applied in the case of molecular collisions. The model breaks down at small impact parameters where orientation of the molecule begins to play a role, and diabatic potential energy surfaces must be calculated instead. Recent developments in this area are reviewed. At lower energies, a host of new theoretical techniques can now be used, notably the infinite order sudden approximation, and time-dependent semiclassical methods. With these recent theoretical developments, it is concluded that the experimentalist must increasingly turn to the coincidence technique to probe the orientation of molecules during collisions, and to supply state-specific data. Such an experiment on the K + CH3I collision system is described next. In these collisions, CH3I is excited to Rydberg levels and subsequently ionises and fragments. The process is known to onset at low scattering angles (500 eVo), and the aim here was to observe these fragment ions in coincidence with the scattered atoms. No coincidence signal was observed, from which an upper estimate of the cross section ratio igmai(θ)/igma_itot could be set. Previous workers have interpreted the excitation mechanism as involving excited ionic intermediate surfaces, and a discussion here using a correlation diagram confirms this view. A comparison with the analogous atomic systems suggest an alternative interpretation, in which the collision is viewed as a scattering of the potassium valence electron off the molecule. In the final part of the thesis, work on an apparatus designed specifically for photon-ion coincidence measurements is described. The apparatus features a multi-angle particle detector, that will allow 45 angular measurements to be made simultaneously. Here the performance of the apparatus is critically assessed, and suggestions are made for improvement. Two pulsing devices are described. The first generate bunching fields for pulsing the ion beam, and will allow us to perform time-of-flight measurements. The second is positioned after the collision zone, and is designed to deflect away the elastically scattered ions that would otherwise contribute to noise in the coincidence experiment.
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Schönning, Karin. "Meson production in pd collisions /". Uppsala : Acta Universitatis Upsaliensis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-100786.
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Piilo, Jyrki. "Cold collisions in optical lattices". Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/piilo/.
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Vosskuhle, Michel. "Particle collisions in turbulent flows". Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2013. http://tel.archives-ouvertes.fr/tel-00946618.
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Cette thèse est consacrée au mécanisme conduisant à des taux de collisions importants dans les suspensions turbulentes de particules inertielles. Le travail a été effectué en suivant numériquement des particules, par simulations directes des équations de Navier-Stokes, et également par étude de modèles simplifiés. Les applications de ce domaine sont nombreuses aussi bien dans un contexte industriel que naturel (astrophysique, géophysique). L'approximation des collisions fantômes (ACF), souvent utilisée pour déterminer les taux de collision numériquement, consiste à compter dans une simulation, le nombre de fois que la distance entre les centres de deux particules devient plus faible qu'une distance seuil. Plusieurs arguments théoriques suggéreraient que cette approximation conduit à une surestimation du taux de collision. Cette thèse fournit non seulement une estimation quantitative de cette surestimation, mais également une compréhension détaillée des mécanismes des erreurs faites par l'ACF. Nous trouvons qu'une paire de particules peut subir des collisions répétées avec une grande probabilité. Ceci est relié à l'observation que, dans un écoulement turbulent, certaines paires de particules peuvent rester proches pendant très longtemps. Une deuxième classe de résultats obtenus dans cette thèse a permis une compréhension quantitative des très forts taux de collisions souvent observés. Nous montrons que lorsque l'inertie des particules n'est pas très petite, l'effet " fronde/caustiques ", à savoir, l'éjection de particules par des tourbillons intenses, est responsable du taux de collision élevé. En comparaison, la concentration préférentielle de particules dans certaines régions de l'espace joue un rôle mineur.
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Li, Bo. "Inelastic collision and three-body recombination". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29779.
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Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009.Committee Chair: M. Raymond Flannery; Committee Member: Daniel Goldman; Committee Member: Dewey H. Hodges; Committee Member: Li You; Committee Member: Turgay Uzer. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Jutzi, Martin. "Studies of collisions involving porous bodies /". [S.l.] : [s.n.], 2009. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Triana, Iglesias Miquel. "Holographic collisions and non-conformal dynamics". Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/460684.
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The gauge/gravity duality has proven to be a very useful tool in the understanding of quantum field theories outside the perturbative regime. In particular, holography has been able to shed light not only on generic mechanisms of strongly coupled theories, but also on processes occurred in experimental set-ups, such as the heavy ion collisions. Experimental observations such as small viscosities or fast hydrodynamization find a natural explanation when the problem is expressed in terms of gravity and black holes. Despite the successes, however, it is important to bear in mind that holography provides computational tools for toy models rather than for QCD itself, and that these models are usable only under certain assumptions. Nature is very often far more nuanced than the models physicists use to describe it. In the case of heavy ion experiments and QCD there are many features that are commonly coarse grained in the holographic computations. For instance, non-trivial RG flows or baryon currents have not been included in the holographic models until very recently, although these are very relevant to experiments, and fundamental in critical phenomena.
In this thesis we present a series of works in the topics field theory and heavy ion collisions that use applied holography and numeric GR as computational tools. The unifying factor among them is that they consider gravitational set-ups beyond pure gravity to describe the physics of conserved currents, non-trivial RG flows and phase transitions.
In chapter 2 we use an Einstein-Maxwell set-up to compute the collision of two shock-waves with a conserved current and the hydrodynamization of the subsequent plasma. This conserved current is used to model the baryonic charge deposition by rapidity, observed in the experiments. The simulations are done with and without including the backreaction of the Maxwell field into the metric, which corresponds to the quenched approximation for the effects of the baryon charge on the gluons.
In chapter 3 we present a one parameter family of non-conformal models. By adding an scalar field with a polynomial potential to the pure gravity set-up, we can achieve a non-trivial RG flow between two fixed points in the dual field theory. In this work we compute the thermodynamics and the quasi-normal modes spectra for the homogeneous states, being the latter one of the main results of the chapter.
In chapter 4 we present the first holographic shock-wave collisions in a non-conformal model. To do so, we use the model introduced in chapter 3. In non-conformal models the average pressure in equilibrium is not fixed by symmetry, but by the equation of state. Out of equilibrium the average pressure might take any value, giving a new probe for the equilibration of the system. When the plasma's average pressure is well approximated by the equation of state value, we say that the system has “EoSizied”. In this chapter we show that the EoSization can indeed happen before the plasma has hydrodynamized.
Finally, in chapter 5 we explore a holographic model that can contain phase transitions. This model is the same as the one presented in chapter 3, but now taking pure imaginary numbers for the controlling parameter. In an effort to understand the instabilities present in models with phase transitions, we trigger and evolve a spinoidal instability to its inhomogeneous end state. This is done by adding a small perturbation to a uniform black brane in a locally unstable branch, triggering a Gregory-Laflamme type instability in the gravity side. The most remarkable result found in the simulation is that both the evolution and the final result are well described by second order hydrodynamics.La cromodinàmica quàntica (QCD), la teoria que descriu la força nuclear forta, és cas paradigmàtic de teoria quàntica de camps amb fases fortament acoblades. Amb l'objectiu d'entendre en profunditat la QCD i la seva dinàmica, és va iniciar a la dècada de 1970 el programa de col·lisions de ions pesants. Aquest programa experimental té com a objectiu crear, mitjançant acceleradors de partícules, fases de QCD de-confinades i estudiar-ne les seves propietats. Entre els formalismes utilitzats per a descriure sistemes fortament acoblats, com les col·lisions d'ions pesants, hi ha la dualita “gauge/string” o holografia. L'holografia és una correspondència entre dues teories -- una teoria gauge i una teoria de cordes -- que permet fer càlculs en una de les dues teories per mitjà de la seva dual. La correspondència es pot fer servir per relacionar un plasma fortament acoblat i el seu dual, forats negres en un espai asimptòticament anti-de-Sitter (AdS), on els càlculs resulten factibles. Així, per simular la col·lisió d'ions pesants s'evoluciona numèricament la col·lisió d'ones gravitatòries en AdS, i la subseqüent relaxació del seu horitzó d'esdeveniments. En aquesta tesi s'hi presenten un seguit de treballs emmarcats en el camp de l'holografia aplicada, on s'hi considera dinàmica en models més enllà de gravetat pura. En el capítol 2 es presenta la primera simulació hologràfica de col·lisions amb càrrega bariònica, un observable accessible en els experiments. Els capítols 3, 4 i 5 estan dedicats a una família de models no conformes. En el capítol 3 se n'estudia la dinàmica prop de l'equilibri per mitjà dels modes quasi-normals. En el capítol 4 s'hi estudien col·lisions hologràfiques. Finalment en el capítol 5 es genera una inestabilitat espinoidal en un model amb transició de fase i se segueix fins a un estat final inhomogeni.
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Vrinceanu, Daniel. "Quantal-classical correspondence in atomic collisions". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/28035.
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Wu, Xin 1967. "Probing colloidal forces with surface collisions". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40469.
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The principal objectives of this thesis are to introduce a new method, colloidal particle scattering (CPS), to measure colloidal and surface forces, and to demonstrate various applications of this method. CPS determines particle-particle interaction forces through creating particle collisions and extracting the interaction forces from the degree of asymmetry of the collision trajectories. Since the force to deflect a micron-sized particle is much smaller than that to deform a macroscopic spring or cantilever used in a commercial force apparatus, this new technique increases the resolution of force determination by four orders of magnitude.Based on the CPS principles, we have built a force apparatus called "microcollider". It successfully determined the van der Waals forces and the electrostatic force between two 5 $ mu$m latex spheres at different salt concentrations. A "hairy" latex model was introduced to explain the measured van der Waals forces which are weaker than those predicted by theory assuming smooth latex surfaces. This is consistent with other experimental findings about the surfaces of latex particles.
A similar "hairy" model was applied to determine the adsorption layer thicknesses of two triblock copolymers adsorbed on latex particles. The results show that the configuration of the buoy block composed of polyethylene oxide (PEO) is more extended than a random PEO coil, which agrees with theoretical predictions. Moreover, excellent quantitative agreement between the adsorption layer thicknesses determined by CPS and other methods has been found.
Dynamic steric interactions between two high molecular weight PEO adlayers have also been studied. Both the elastic modulus and the adsorption layer thickness were determined. The results show that a thick layer has a lower elastic modulus than a thin one composed of the same polymer. This implies that an extended loop/tail structure in a thick layer is less stiff than a flat compact one in a thin layer, which is consistent with theory.
In addition, the microcollider can accurately determine particle-wall interactions as well. A rather weak electrokinetic lift force was measured. The results are in good agreement with the solutions rigorously derived from two new theories.
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Hughes, Timothy John. "Luminescent collisions of energetic manganese atoms". Thesis, Northumbria University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262819.
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McLeod, Andrew. "Instabilities in supersonic cloud-cloud collisions". Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/38842/.
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We study the effects of the supersonic collision of molecular clouds using smoothed particle hydrodynamics (SPH) simulations. We review the observational evidence for cloud-cloud collision and previous computational work. We describe the SPH method, the algorithms used in the SPH code SEREN, and how we have extended the parallelization of SEREN. We review the non-linear thin shell instability (NTSI) and gravitational instability in a shock-compressed layer. We present the results of two sets of SPH simulations. In the first set of simulations we collide supersonic flows of gas without self-gravity. We impose a range of velocity perturbations, including monochromatic perturbations, white noise perturbations and both subsonic and supersonic turbulence. The colliding flows create a dense shock-compressed layer which is unstable to the NTSI. We examine the effect of the differing initial perturbations on the NTSI, and calculate rates of growth of both bending modes and breathing modes as a function of time and wavenumber. We compare our results to the time-independent result predicted by Vishniac (1994) for a one-dimensional monochromatic perturbation, and examine how this result can be extended to two-dimensional perturbations and non-monochromatic perturbations. In our second set of simulations we model the head-on supersonic collision of two identical uniform-density spheres. We include self-gravity, allowing the dense layer to become gravitationally unstable and produce stars. We explore the effect of increasing collision velocity, and show that the NTSI is present only at higher collision velocities. At the highest collision velocities the NTSI severely disrupts the layer, and the collision does not produce stars. Although the global properties of the collision, such as the thickness of the layer, the size of the star-forming region and the time of first star formation, depend on the collision velocity, most individual properties of the stars do not.
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Newell, Catherine A. "INELASTIC COLLISIONS IN COLD DIPOLAR GASES". UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/30.
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Inelastic collisions between dipolar molecules, assumed to be trapped in a static electric field at cold (> 10−3K) temperatures, are investigated and compared with elastic collisions. For molecules with a Λ-doublet energy-level structure, a dipole moment arises because of the existence of two nearly degenerate states of opposite parity, and the collision of two such dipoles can be solved entirely analytically in the energy range of interest. Cross sections and rate constants are found to satisfy simple, universal formulas. In contrast, for molecules in a Σ electronic ground state, the static electric field induces a dipole moment in one of three rotational sublevels. Collisions between two rotor dipoles are calculated numerically; the results scale simply with molecule mass, rotational constant, dipole moment, and field strength.
It might be expected that any particles interacting only under the influence of the dipole-dipole interaction would show similar behavior; however, the most important and general result of this research is that at cold temperatures inelastic rate constants and cross sections for dipoles depend strongly upon the internal structure of the molecules. The most prominent difference between the Λ-doublet and rotor molecules is variation of the inelastic cross section with applied field strength. For Λ-doublet dipoles, cross sections decrease with increasing field strength. For rotor dipoles, cross sections increase proportionally with the square of field strength. Furthermore, the rate constants of the two types of molecules depend very differently on the angular orientations of the dipoles in the electric field.
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Glover, Edward William Nigel. "Studies of high energy pp collisions". Thesis, Durham University, 1985. http://etheses.dur.ac.uk/7113/.
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The Standard Model of particle physics is examined in the context of high energy proton-antiproton collider experiments. The large energies available offer the possibility of producing new particles which may then be observed via their decay. Heavy quark production is examined through the production of unlike-sign lepton pairs. Methods for isolating several dilepton production mechanisms are given, including an eu signal for the top quark. Moreover, ψ production is shown to serve as a particularly clean tag for the production of particles containing b quarks. The possibility of observing a fourth generation heavy lepton via W decay is investigated. The hadronic decay mode leads to a promising signature of large missing accompanied by two hadronic jets and has a very healthy event rate. The monojet events found by the UA1 experiment are reviewed. Various extensions of the Standard Model are examined as possible explanations of these events. The first interpretation involves the production of SUSY particles. These are found to be compatible with the data if two squarks exist with mass 0(30GeV) and the gluino has mass > 0(60GeV). Secondly, interpretations based on four point effective interactions of the form qqZg are investigated, and are shown to be unable to account for the observed monojet rate. Finally, the production and decay of new heavy states (for example excited quarks) could account for the monojet data, but are found to predict large numbers of W + jet and γ + jet events which have not been seen.
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Hughes, Ian G. "Electron ion and ion-ion collisions". Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335410.
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Bradley, J. P. "Charge transfer during ion-atom collisions". Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426960.
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Segura-Sanchez, Mararita. "Collisions in a stream of drops". Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364298.
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Barry, N. J. "Molecular beam studies of reactive collisions". Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375059.
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Truhins, Kaspars. "Stereodynamics of asymmetric rotor - atom collisions". Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363381.
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Moores, John Demeritt. "Collisions of orthogonally polarized solitary waves". Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14420.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1989.Includes bibliographical references.
Support from the Office of Naval Research in the form of a 1986-1989 ONR Fellowship.
by John Demeritt Moores.
M.S.
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Côté, Joseph Noël Robin. "Ultra-cold collisions of identcial atoms". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32632.
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Obisesan, Abayomi. "Stochastic damage modelling of ship collisions". Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231845.
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Ship collision accidents are rare events but pose huge threat to human lives, assets, and the environment. Collision resistance of ships is usually assessed in terms of ship structural response such as member displacement, energy dissipation and the extent of damage. Many researchers have sought for effective models that compute ship stochastic response during collisions by considering the variability of collision scenario parameters. However, the models were limited by the capability of the collision computational models and did not completely capture collision scenario, and material and geometric uncertainties. In addition, the simplified models capturing the input-response relationships of the ship structural impact mechanics are in implicit forms which makes them unsuitable for assessing the performance of structural design specifications in collisions. Furthermore, with increasing ship passages in the Arctic region, the probabilities of ship-iceberg interactions are increasing, highlighting the need to focus on risk based ship designs. In this research, a conceptual stochastic modelling framework is developed for performance characterisation and quantitative risk assessment of ship-ship and ship-iceberg collisions. In this direction, an interface for automated stochastic finite element computations was developed to model ship structural resistance in reference collision scenarios. The stochastic structural response was characterised based on the onset of the ship structural failure. The focus was initially on ship-ship collisions to quantify the uncertainties experimentally and to characterise the performance for a variety of striking ships. The framework was then extended to consider probabilistic performance measures in ship-iceberg collisions. The computationally intensive collision response models were captured with efficient surrogate representations so that the performance measures can be obtained with gradient based reliability approaches. The most probable input design sets for the response distribution were sampled with Latin Hypercube models. The probabilistic performance measures were also combined with available collision frequency models from literature for risk computations and to demonstrate the risk tolerance measures. The framework underlines the significance of different risk components, providing valuable guidance for improving risk-based ship designs. Although, a double-hull crude oil carrier is presented as the struck ship, the approach can be readily extended to characterise the performance and risk of other ship structures in collisions.
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Pons, Bernard. "Collisions ion-atome aux énergies intermédiaires". Bordeaux 1, 1994. http://www.theses.fr/1994BOR10612.
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L'approche moleculaire de la theorie des collisions ion-atome est etendue au domaine des energies intermediaires. L'emploi d'un facteur de translation commun optimise permet une evaluation quantitative precise des processus de capture et d'excitation ainsi qu'une evaluation implicite du processus d'ionisation a haute energie d'impact. Une modelisation du canal d'ionisation est alors proposee afin d'obtenir un traitement theorique unique permettant de calculer les sections efficaces des trois processus inelastiques. Le mecanisme d'ionisation dans un cadre moleculaire est explicite et corrobore le mecanisme d'ionisation au point de selle dont la mise en evidence est fort controversee experimentalement
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Lévêque, Sandrine. "Collisions ions surfaces. Effets initiaux d'oxydation". Paris 11, 1994. http://www.theses.fr/1994PA112387.
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L'etude experimentale des collisions d'ions et d'atomes de gaz rares sur des surfaces a ete effectuee grace a une analyse angulaire et/ou energetique des particules lourdes et des electrons ejectes lors de la collision. L'appareil utilise fonctionne en ultravide. Les mesures ont permis de mettre en evidence la presence de processus de transferts de charges entre les projectiles et la cible, ainsi que la presence de processus d'excitation vers des etats autoionisants. Les processus d'excitation mis en jeu dependent de la nature du projectile et de la cible ; ils sont decrits, par analogie aux collisions en phase gazeuse, grace au modele quasimoleculaire de barat fano lichten. Les particules peuvent se desexciter dans le vide ou a l'interieur du solide. Certains mecanismes de rearrangement ont lieu lors de la phase de sortie de la collision, ils sont caracteristiques des collisions sur les surfaces. L'etude des effets initiaux de l'oxydation ont permis de caracteriser l'adsorption de l'oxygene sur differentes surfaces, et de montrer que la variation du travail d'extraction est maximale pour une exposition correspondant a la saturation de la surface. Nos mesures ont permis de mettre en evidence la disparition progressive des pics attribues a l'autoionisation des projectiles et des atomes-cibles. Des variations differentes en fonction de l'exposition a l'oxygene ont ete observees pour differents etats excites. Ces resultats sont attribues a l'effet d'ecran des atomes-cibles par l'oxygene, a la variation du travail d'extraction et de la densite d'etats de la cible, en presence d'oxygene
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Lidström, Olof, i Oscar Edling. "Injury prevention in vehicle side collisions". Thesis, KTH, Skolan för teknikvetenskap (SCI), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276669.
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In America around 30% of all fatal car collisions are a result of side collisions. Furthermore, in Europe between 28% to 38% of all side collisions results in serious injury or death. There are existing protection systems to minimize the risk of injury. Most commonly a combination airbag system or a curtain system is used to protect the occupants in the event of a side collision. A combination bag deploys forwards from the back-rest to protect the occupants thorax and pelvis. For head protection this system implements an extension from the seat mounted bag which deploys upwards towards the head area. The drawback of this system is that the area covered by the airbag is limited. Curtain solutions commonly work in tandem with a seat mounted thorax airbag, which protects the occupants upper body, like the combo solution. The curtain solution protects the head by deploying an inflatable curtain alongside the inner wall of the vehicle. Unlike the combo solution a curtain has the ability to cover a greater area. However, the downside is that it deploys further from the occupants body, which allows the body to move more freely. In this report the combination and curtain systems were compared. A general comparison was conducted using data from Euro NCAP, which showed that the combination system offers slightly better protection for the head in a collisions directed 90 degrees from the side, while the curtain solution offers greater protection for the thorax region if the collision is at an angle. Whiplash is the most common traffic related injury in Sweden. However, it is not usually a fatal one. Commonly whiplash injuries occur in rear ends collisions when the head jerks back. The jerking motion that occurs in a side collision can also result in acute whiplash associated disorders (WAD). Analyzing the WAD effect of the inflatable curtain airbag systems compared to the combination airbag system in side injuries is a complex task. A comparison was made using accelerometer data acquired from NHTSA's. database and a modified implementation of the NIC-criterion. The results indicated that there is a risk for whiplash injuries present in side collisions and that different cars have different prerequisites for preventing injury. A definite answer which of the airbag systems offer better protection from WAD could not be found using the provided data.I USA orsakas cirka 30\% av alla trafikdödsfall av sidokollisioner. I Europa är motsvarande siffra mellan 28% och 38%. Vidare rapporterar Shanghai United Road Traffic Safety Scientific Research Center (SHUFO) att mer än hälften av dödsfallen vid sidokollisioner är till följd av huvud och nackskador. Det finns befintliga skyddssystem för att minimera risken för huvud och nackskador vid dessa typer av kollisioner. Vanligtvis används airbags konfigurationerna kombinationssystem (combo) eller gardinsystem (IC). En kombinationssystem utlöses framåt från ryggstödet för att skydda passagerarens överkropp. För att skydda huvudet använder detta system en tilläggskudde, som vecklas ut från den sätesmonterade kudden upp mot huvudet. Nackdelen med detta system är systemet har begränsat täckningsområde. Gardinlösningar fungerar vanligtvis i tandem med en sätesmonterad krockkudde, vilket skyddar passagerarnas överkropp, likt kombinationssystemet. Gardinlösningen skyddar huvudet genom en uppblåsbar gardin som utlöses längs fordonets innervägg. Till skillnad från kombinationssystemet har ett gardinsystem förmågan att täcka en större yta. Nackdelen är dock att denna befinner sig längre bort från passagerna, vilket tillåter huvudet att röra sig relativt överkroppen. I denna rapport jämfördes kombinations- och gardinsystemen. En övergripande jämförelse gjordes med hjälp av data från Euro NCAP. Resultatet av denna jämförelse visade att kombinationssystemet ger något bättre skydd för huvudet i en kollision riktad 90 grader från sidan, medan gardinlösningen erbjuder bättre skydd för bröstkorgen då kollisionen är vinklad. Pisksnärtsskador (Whiplash) är den vanligaste trafikskadan i Sverige. Värt att notera är dock att dessa sällan har dödlig utgång. De flesta whiplash-skador uppstår vid kollisioner bakifrån, då huvudet rycker tillbaka. Denna rörelse kan inträffa även vid sidokollisioner, vilket innebär att även dessa typer av kollisioner kan resultera i pisksnärtsskador. En jämförelse mellan piskssnärtskade-effekten hos gardinsystemet och kombinationssystemet gjordes med hjälp av accelerometerdata som erhållits från NHTSA:s databas och en modifierad implementering av NIC-kriteriet. Resultaten indikerade att det finns en risk för whiplash-skador vid sidokollisioner och att olika bilar har olika förutsättningar för att passagerarna ska drabbas av dessa typer av skador. Ett definitivt svar på vilket av krockkuddesystemen som erbjuder bäst skydd mot pisksnärtsskador kunde inte finnas med den erhållna datan.\\
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Tan, Jonathan S. "Compiler Optimization Effects on Register Collisions". DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1841.
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We often want a compiler to generate executable code that runs as fast as possible. One consideration toward this goal is to keep values in fast registers to limit the number of slower memory accesses that occur. When there are not enough physical registers available for use, values are ``spilled'' to the runtime stack. The need for spills is discovered during register allocation wherein values in use are mapped to physical registers. One factor in the efficacy of register allocation is the number of values in use at one time (register collisions). Register collision is affected by compiler optimizations that take place before register allocation. Though the main purpose of compiler optimizations is to make the overall code better and faster, some optimizations can actually increase register collisions. This may force the register allocation process to spill. This thesis studies the effects of different compiler optimizations on register collisions.
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Xia, Jianjun. "Finite Element Analysis of Ship Collisions". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34133.
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The serious consequence of ship collisions necessitates the development of regulations and requirements for the subdivision and structural design of ships so that damage and environmental pollution is reduced, and safety is improved. A simplified collision model (SIMCOL) is currently being developed at Virginia Tech to conduct probabilistic analysis of damage in ship collisions and ultimately optimize ship structural designs to improve crashworthiness. Collision data for validation of SIMCOL is very difficult to obtain, and model testing is very costly. Finite Element Analysis (FEA) provides an alternative to physical validation that can be used to increase confidence and insight in simplified model results.
This thesis develops a complete methodology for ship-to-ship collision simulations using the explicit non-linear FE code LS-DYNA3D. Various modeling alternatives are considered. The ability to model a complete ship-to-ship collision is developed incrementally starting with bow collisions with a rigid wall. A super-element (intersection model) approach is considered to increase the calculation speed of bow models. A conventional fine mesh finite element bow model is also developed. Results from both models are compared with each other, and with a closed-form calculation from Pedersen. A fine mesh model is developed for a struck tanker cargo section and integrated in a total ship framework modeling external dynamics and ship-to-ship contact. A series of collision scenarios is simulated using the conventional bow model and a rigid bow model striking a double hull tanker. Results are compared with SIMCOL, DAMAGE, DTU and ALPS/SCOL models. LS-DYNA provides detailed and reasonable results for ship collision analysis and comparison to increase confidence in simplified models.Master of Science
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Daniello, Allison Louise. "Injury Mechanisms in Roadside Motorcycle Collisions". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/20381.
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More motorcyclists are fatally injured each year in guardrail crashes than passengers of any other vehicle, while only accounting for three percent of the vehicle fleet. Since motorcyclists account for a high percentage of these fatalities, the goal of zero deaths on the road cannot be achieved without addressing the safety of motorcyclists. The objective of this research was to determine the factors that lead to serious or fatal injury in motorcycle barrier crashes, given that a crash occurred. The likelihood of serious or fatal injury in barrier crashes was significantly influenced by both barrier type and rider trajectory after striking the barrier. A national study of motorcyclist fatality risk using the Fatality Analysis Reporting System (FARS) and General Estimates System (GES) showed that crashes with guardrail than crashes were about 7 times more likely to be fatal than those with the ground, based on the most harmful event reported. An analysis of 1,000 riders in barrier crashes in three states showed that the odds of serious injury were 1.4 times greater in guardrail crashes than in concrete barrier crashes. These analyses did not take into account the trajectory of the rider after striking the barrier, since this was unknown. The police accident report for 350 barrier crashes in New Jersey was used to determine the rider trajectory in those crashes. Being ejected from the motorcycle after impacting the barrier significantly increased the odds of serious injury over crashes where the rider was not ejected.
While providing insight into factors influencing injury severity, these analyses do not provide an understanding of the nature of injuries incurred in these crashes. To further understand how injuries were caused in motorcycle-barrier crashes, we developed a methodology for determining injury mechanisms in motorcycle-barrier collisions. Using this methodology, we investigated 9 serious motorcycle-to-barrier crashes. In these crashes, as well as in an analysis of 106 barrier crashes in Maryland, the thorax and lower extremities most commonly suffered serious injury. Of particular concern are the posts and top of the rail, both of which can lead to lacerations and blunt trauma.
Ph. D.
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Pandit, Yadav. "AZIMUTHAL ANISOTROPY IN HEAVY ION COLLISIONS". Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1353871180.
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Taliotis, Anastasios Socrates. "Geometrical Methods in Heavy Ion Collisions". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285088429.
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Chao, Megan(Megan C. ). "Physically accurate collisions in StarLogo Nova". Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130683.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, February, 2021Cataloged from the official PDF of thesis.
Includes bibliographical references (page 56).
StarLogo Nova is a blocks-based programming language for students that helps teach programming by allowing users to model their own physical simulations and create games. In many simulations and games, it may be useful to have physically accurate elastic, inelastic, or partially inelastic collisions. However, StarLogo's current collision detection system relies on detecting overlapping objects after they have already collided, so it cannot simulate such collisions. We create a new continuous-time collision detection algorithm which computes the exact time two objects collide and processes collisions in time order. To verify it is possible to add physically accurate collisions to StarLogo using this algorithm, we test the continuous collision algorithm in the GlowScript, using elastic, inelastic, and partially elastic collision behavior. The new algorithm can be integrated into the execution model and new blocks can be added for different types of physically accurate collisions in order to bring accurate collisions to StarLogo.
by Megan Chao.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science