Dissertations / Theses on the topic 'Mixing problem'

Colloidal dispersions are found in many modern product formulation processes, and one of the problems commonly occurring in these processes is characterising the particles within these systems. The existing theories for predicting acoustic scattering in these systems do not fully account for the interactions between neighbouring particles. Most importantly they do not account for the thermal interactions in thermoacoustic scattering. In this thesis I develop an asymptotic solution in the small wave number limit to the multiple scattering problem. This is done by considering the thermoacoustic field interaction between two different sized particles close together, and applying this to a pair distribution probability function, giving an extra term in the far field scattering calculations. This provides a method of predicting attenuation in mono- and bi-disperse colloids, especially for those of higher concentrations. This theory is compared to attenuation experimental data for a number of different colloidal systems, mono- and bi-disperse of increasing concentrations, where the thermal field overlap between particles is more prominent. Comparing these experiments with the new two particle thermoacoustic scattering theory give more consistent results than previous theories for volume concentrations up to 30%. Further work, as part of a CASE studentship, on sedimentation detection in pipe flow using by monitoring the behaviour of pulses of ultrasound is also presented in this thesis.

It has been almost 50 years since York published an exact and general solution for the best-fit straight line to independent points with normally distributed errors in both x and y. York's solution is highly cited in the geophysical literature but almost unknown outside of it, so that there has been no ebb in the tide of books and papers wrestling with the problem. Much of the post-1969 literature on straight-line fitting has sown confusion not merely by its content but by its very existence. The optimal least-squares fit is already known; the problem is already solved. Here we introduce the non-specialist reader to York's solution and demonstrate its application in the interesting case of the isotopic mixing line, an analytical tool widely used to determine the isotopic signature of trace gas sources for the study of biogeochemical cycles. The most commonly known linear regression methods – ordinary least-squares regression (OLS), geometric mean regression (GMR), and orthogonal distance regression (ODR) – have each been recommended as the best method for fitting isotopic mixing lines. In fact, OLS, GMR, and ODR are all special cases of York's solution that are valid only under particular measurement conditions, and those conditions do not hold in general for isotopic mixing lines. Using Monte Carlo simulations, we quantify the biases in OLS, GMR, and ODR under various conditions and show that York's general – and convenient – solution is always the least biased.

Ce travail de thèse s'inscrit dans le cadre du développement de la méthode de mélange de configurations multiparticules-multitrous visant à décrire les propriétés de structure des noyaux atomiques. Basée sur un double principe variationnel, cette approche permet de déterminer simultanément les coefficients d'expansion de la fonction d'onde et les orbitales individuelles.Dans ce manuscrit, le formalisme complet méthode de mélange de configurations multiparticules-multitrous auto-cohérente est pour la première fois appliqué à la description de quelques noyaux des couches p et sd, avec l'interaction de Gogny D1S.Un première étude du 12C est effectuée afin de tester et comparer le double processus de convergence lorsque différents types de critères sont appliqués pour sélectionner les configurations à N-corps inclues dans la fonction d'onde du noyau. Une analyse détaillée de l'effet induit par l'optimisation des orbitales est conduite. En particulier, son impact sur la densité à un corps et sur la fragmentation de la fonction d'onde de l'état fondamental, est analysé.Une étude systématique de noyaux de la couche sd est ensuite conduite. Une analyse précise du contenu en corrélation de l'état fondamental est effectuée, et quelques quantités observables telles que les énergies de liaison et de séparation, ainsi que les rayons de charge, sont calculées et comparées à l'expérience. Les résultats obtenus sont satisfaisants. La spectroscopie de basse énergie est ensuite étudiée. Les énergies d'excitation théoriques sont en très bon accord avec les données expérimentales, et les caractéristiques dipolaires magnétiques sont également satisfaisantes. Les propriétés quadripolaires électriques, et en particulier les probabilités de transition B(E2), sont par contre largement sous-estimée par rapport aux valeurs expérimentales, et révèle un manque important de collectivité dans la fonction d'onde, dû à l'espace de valence restreint considéré. Si la renormalisation des orbitales induit une importante fragmentation de la fonction d'onde de l'état fondamental, seul un effet très faible est obtenu sur les probabilités de transition B(E2). Une tentative d'explication est donnée.Enfin, les informations de structure fournies par la méthode de mélange de configurations multiparticules-multitrous sont utilisées comme ingrédient de base pour des calculs de réactions telles que la diffusion inélastique de protons et d'électrons sur noyaux de la couche sd. Si les résultats révèlent aussi un manque de collectivité, les tendances expérimentales sont bien reproduites et sont améliorées par l'optimisation des orbitales
This thesis project takes part in the development of the multiparticle-multihole configuration mixing method aiming to describe the structure of atomic nuclei. Based on a double variational principle, this approach allows to determine the expansion coefficients of the wave function and the single-particle states at the same time. In this work we apply for the first time the fully self-consistent formalism of the mp-mh method to the description of a few p- and sd-shell nuclei, using the D1S Gogny interaction.A first study of the 12C nucleus is performed in order to test the doubly iterative convergence procedure when different types of truncation criteria are applied to select the many-body configurations included in the wave-function. A detailed analysis of the effect caused by the orbital optimization is conducted. In particular, its impact on the one-body density and on the fragmentation of the ground state wave function is analyzed.A systematic study of sd-shell nuclei is then performed. A careful analysis of the correlation content of the ground state is first conducted and observables quantities such as binding and separation energies, as well as charge radii are calculated and compared to experimental data. Satisfactory results are found. Spectroscopic properties are also studied. Excitation energies of low-lying states are found in very good agreement with experiment, and the study of magnetic dipole features are also satisfactory. Calculation of electric quadrupole properties, and in particular transition probabilities B(E2), however reveal a clear lack of collectivity of the wave function, due to the reduced valence space used to select the many-body configurations. Although the renormalization of orbitals leads to an important fragmentation of the ground state wave function, only little effect is observed on B(E2) probabilities. A tentative explanation is given.Finally, the structure description of nuclei provided by the multiparticle-multihole configuration mixing method is utilized to study reaction mechanisms such as electron and proton inelastic scattering on sd-shell nuclei. Although the results also suffer from the lack of collectivity, the experimental trends are well reproduced and improved by the orbital optimization

vi, 48 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
We compare the relaxation times of two random walks - the simple random walk and the metropolis walk - on an arbitrary finite multigraph G. We apply this result to the random graph with n vertices, where each edge is included with probability p = [Special characters omitted.] where λ > 1 is a constant and also to the Newman-Watts small world model. We give a bound for the reconstruction problem for general trees and general 2 × 2 matrices in terms of the branching number of the tree and some function of the matrix. Specifically, if the transition probabilities between the two states in the state space are a and b , we show that we do not have reconstruction if Br( T ) [straight theta] < 1, where [Special characters omitted.] and Br( T ) is the branching number of the tree in question. This bound agrees with a result obtained by Martin for regular trees and is obtained by more elementary methods. We prove an inequality closely related to this problem.
Committee in charge: David Levin, Chairperson, Mathematics; Christopher Sinclair, Member, Mathematics; Marcin Bownik, Member, Mathematics; Hao Wang, Member, Mathematics; Van Kolpin, Outside Member, Economics

Thesis (Ph.D.)--Case Western Reserve University, 2004
Title from PDF (viewed on 01 October 2009) Department of Mechanical Engineering Includes abstract Includes bibliographical references Available online via the OhioLINK ETD Center

This diploma thesis deals with optimization models with design of a new waste management infrastructure in the Czech Republic, such that combustible waste, which is not utilized by the material recovering, can be used by energy recovering. This task is handled by optimization models, including trac and mixing problems. First of all, the concepts of graph theory and optimization are presented in this paper. Subsequently, some of the GAMS functions are discussed, and later the VBA programming language used to handle the larger data quickly is presented. In the main part, three gradually expanding models are developed. At the end the data from the waste management information system are implemented into them.

Geochemical and reactive transport modelling are essential tools in hydrogeology. They help to identify and assess geochemical processes occurring in applications such as groundwater contamination, water-rock interactions and geologic carbon sequestration. In this thesis we present methods for mixing and speciation calculations to be used for both interpretation of hydrochemical data and numerical modelling. The first method presented allows solving geochemical speciation using redundant information, while acknowledging errors in data. Traditional speciation algorithms use a fixed number of data and equilibrium assumptions to calculate the concentration of the species present in a chemical system. We demonstrate that using redundant data (i.e., data or assumptions that exceed the minimum required and therefore are not strictly necessary) can improve speciation results by reducing estimation errors. In fact, we show that speciation errors decrease when increasing the number of redundant data. The second method presented allows calculating mixing proportions of a number of end-members in a water sample from uncertain chemical data. Traditional methods for evaluating mixing ratios require the use of conservative tracers, which severely limits their applicability. The novelty of the method lies on the possibility of imposing equilibrium conditions on the mixture, while acknowledging kinetic reactions, which naturally leads to quantification of reactions. We applied the method to a freshwater-saltwater mixing problem in a set of samples collected by Sanz (2007), where we also characterized carbonate dissolution/precipitation and the production/consumption of CO2. These methods have been implemented in an Object-Oriented library called "CHEPROO++". This library can be used for hydrogeochemical calculations such as mixing waters linked to mass balance programs, which allows extending conservative transport simulators to solve reactive transport. One peculiarity of CHEPROO++ is the possibility of defining components decoupling constant activity species (CAS) such as, for example, pure equilibrium minerals or water (if the solution is sufficiently diluted). CHEPROO++ treats CAS as primary species. Decoupling CAS can be useful for speciation calculations because it allows reducing the system to be solved iteratively. To check if decoupling CAS is advantageous, we applied the speciation algorithm that decouples CAS to a reactive transport application. In particular we used this speciation algorithm for the chemical step of the Sequential Iteration Approach for reactive transport modelling. We compared the proposed algorithm with the traditional method, which does not decouple CAS, on a onedimensional domain where calcite is dissolving in equilibrium. Results show that decoupling CAS can decrease the number of iterations necessary for transport and chemistry calculations in case of equilibrium dissolution.
El transporte reactivo y la modelación geoquímica son herramientas necesarias en hidrogeología, porque ayudan a identificar y cuantificar procesos geoquímicos que ocurren en diferentes aplicaciones como contaminación de aguas subterráneas, interacción agua-roca y secuestro geológico de CO2. En estas tesis presentamos métodos para cálculos de mezcla y especiación para interpretación de datos hidrogeoquímicos y modelación numérica. El primer método que presentamos permite resolver la especiación geoquímica con información redundante, y permite definir errores en los datos. Los algoritmos tradicionales de especiación utilizan un número fijo de datos y condiciones de equilibrio para calcular las concentraciones de las especies de un sistema químico. Con este método, demostramos que el uso de datos redundantes (p.ej. datos o hipótesis que exceden el mínimo requerido, y por tanto no son estrictamente necesarios) puede mejorar los resultados de la especiación reduciendo los errores de estimación. De hecho, mostramos como los errores de especiación disminuyen aumentando el número de datos redundantes. El segundo método que presentamos permite calcular proporciones de mezcla de miembros extremo en una muestra a partir de datos químicos inciertos. Los métodos de mezcla tradicionales utilizan trazadores conservativos, y esto limita mucho sus aplicabilidad. La novedad de este método está en la posibilidad de imponer condiciones de equilibrio y considerar reacciones cinéticas, que naturalmente permiten cuantificar reacciones. Hemos aplicado el método a unas muestras representativas de mezcla entre agua dulce y agua salada tomadas por Sanz (2007), en las que también hemos caracterizado disolución/precipitación de carbonatos y producción/consumo de CO2. Estos métodos han sido implementados en una librería ("CHEPROO++") usando el paradigma de programación orientada a objetos. Este módulo se puede utilizar para cálculos hidrogeoquímicos como mezclas de agua si se acopla a programas de balance de masa, y también puede extender programas de transporte conservativo para resolver transporte reactivo. Una peculiaridad de CHEPROO++ es la posibilidad de definir componentes desacoplando las especies de actividad constante (CAS) como, por ejemplo, minerales puros en equilibrio o agua (si la solución está suficientemente diluida). CHEPROO++ considera CAS como especies primarias. El desacople de CAS puede ser útil para la especiación porque permite reducir el tamaño del sistema que se tiene que resolver iterativamente. Para comprobar que desacoplar CAS es una ventaja, hemos aplicado el algoritmo de especiación que desacopla CAS a una aplicación de transporte reactivo. En particular, lo hemos utilizado para el paso químico del Sequential Iteration Approach, uno de los algoritmos para transporte reactivo. Hemos comparado el algoritmo propuesto con el tradicional, que no desacopla CAS, en un dominio unidimensional donde la calcita está disolviendo en equilibrio. Los resultados muestran que desacoplar CAS puede ayudar a reducir el número de iteraciones necesarias para el transporte y para la química en el caso de disolución en equilibrio
El transport reactiu i la modelació geoquímica són eines necessàries en hidrogeologia, perquè ajuden a identificar i quantificar processos geoquímics que es donen en diferents aplicacions com contaminació d’aigües subterrànies, interacció aigua-roca i segrest geològic de CO2. En aquesta tesi presentem mètodes per a càlculs de mescla i especiació per interpretació de dades hidrogeoquímiques i modelació numèrica. El primer mètode que presentem permet resoldre la especiació geoquímica amb informació redundant, i permet definir errors en les dades. Els algoritmes tradicionals d’especiació utilitzen un nombre fix de dades i condicions d’equilibri per calcular les concentracions de les espècies d’un sistema químic. Amb aquest mètode, demostrem que l’ús de dades redundants (p. e. dades o hipòtesis que excedeixen el mínim requerit, i per tant no són estrictament necessàries) pot millorar els resultats de l’especiació reduint els errors d’estimació. De fet, ensenyem com els errors d’especiació disminueixen augmentant el nombre de dades redundants. El segon mètode que presentem permet calcular proporcions de mescla de membres extrem en una mostra a partir de dades químiques incertes. Els mètodes de mescla tradicionals utilitzen traçadors conservatius, i això limita molt la seva aplicabilitat. La novetat d’aquest mètode està en la possibilitat d’imposar condicions d’equilibri i considerar reaccions cinètiques, que naturalment permeten quantificar reaccions. Hem aplicat el mètode a unes mostres representatives de mescla entre aigua dolça i aigua salada preses per Sanz (2007), en què també hem caracteritzat dissolució / precipitació de carbonats i producció/consum de CO2. Aquests mètodes han estat implementats en una llibreria ("CHEPROO ++") utilitzant el paradigma de programació orientada a objectes. Aquest mòdul es pot utilitzar per càlculs hidrogeoquímics com mescles d’aigua si s’acobla a programes de balanç de massa, i també pot estendre programes de transport conservatiu per resoldre transport reactiu. Una peculiaritat de CHEPROO ++ és la possibilitat de definir components desacoblant les espècies d’activitat constant (CAS) com, per exemple, minerals purs en equilibri o aigua (si la solució és prou diluïda). CHEPROO ++ considera CAS com a espècies primàries. El desacoblament de CAS pot ser útil per a la especiació perquè permet reduir la mida del sistema que s’ha de resoldre iterativament. Per comprovar si desacoblar CAS és un avantatge, hem aplicat l’algoritme d’especiació que desacobla CAS a una aplicació de transport reactiu. En particular, l’hem utilitzat per al pas químic del Sequential Iteration Approach, un dels algoritmes per a transport reactiu. Hem comparat l’algoritme proposat amb el tradicional, que no desacobla CAS, en un domini unidimensional on la calcita està dissolent en equilibri. Els resultats mostren que desacoblar CAS pot ajudar a reduir el nombre d’iteracions necessàries per al transport i per a la química en el cas de dissolució en equilibri

In recent years there has been an increasing awareness of the detrimental influence of diffuse sources of pollution on aquatic systems and of the integral role played by sediment in the mobilisation and transport of pollutants. The recognition of the environmental, societal and economic importance of the ecological health of aquatic environments has led to a change in emphasis regarding agricultural and environmental policy. To implement successful delivery of emerging policy requirements, there is a current need to have an enhanced understanding of the relationship between different forms of land use and sources of diffuse pollution, particularly sources of fine sediment. To understand the potential impacts of future land use changes, including environmental conservation measures on sources of sediment, it is useful to consider them within a longer-term context. This study has successfully applied the sediment source fingerprinting technique to floodplain overbank sediment cores in a retrospective study of six diverse UK river catchments with identified sediment problems. The varying estimates of relative sediment contributions from differing sources have been compared to known land use change in the study catchments over concurrent time periods, to explore any associations which might be apparent. Over the last 40 years, the increased cultivation of high erosion risk crops, such as those which are harvested late in the season (e.g. maize) and those which are sown in the autumn (e.g. winter wheat), has contributed disproportionately to the total sediment load relative to the area of land occupied by such cultivation. Increased stocking densities have resulted in increased relative sediment contributions from grassland sources, particularly intensively managed temporary grassland, but can have an even greater impact on sediment contributions derived from channel bank sources. The installation and maintenance of drainage for agriculture or for flood risk management has resulted in increased relative sediment loads from channel bank and associated sub-surface sources. Through the further development of such research, the efficacy of mitigation measures can be tested against evidence-based historic trends and those management approaches which provide identifiable improvements can be developed as best practice options for future land management targeted at reducing the negative impacts of excessive sediment ingress to river systems. The design of the source fingerprinting methodology used in this work was based on an established successful approach and this was developed further through the incorporation of a number of refinements designed to improve the robustness of the technique and expedite its implementation.

In this dissertation the results of Jerrum and Sinclair on the conductance of Markov chains are used to prove that almost all generalized Steinhaus graphs are rapidly mixing and an algorithm for the uniform generation of 2 - (4k + 1,4,1) cyclic Mendelsohn designs is developed.

Jag vill med denna C-uppsats redovisa vad som är enkelt kontra det som är besvärligt då jag under en period får möjlighet att mixa filmmusik i 5.1 hos Ljudligan. Därutöver vill jag även fokusera på att skildra hur jag löser de problem som uppstår vid mixningen för att slutligen redovisa det som är enkelt att lösa. Med till praktiken har jag en generell förståelse för surround och de olika delmomenten vid mixning. För att lösa de moment som jag upplever som besvärliga kommer jag först att försöka på eget sätt att arbeta fram en bekväm ljudbild. Huruvida jag når ett bra resultat beror dels att jag själv ska bli nöjd, men även på om min handledare hos Ljudligan uppskattar min färdiga produktion. Jag kommer vid behov att fråga de övriga anställda hos Ljudligan för rekommendationer gällande mina problem. Slutligen kommer jag att vända mig till litteraturen för problemlösningar. Under perioden hos Ljudligan fick jag arbeta med cirka 15 minuters musik till filmen Låt den rätta komma in. Flerkanaligtljud har funnits sedan 1930-talet, där Walt Disney tillsammans med sina kollegor 1938 tog fram teknologin Fantasound. Därefter har tekniken utvecklas och idag förutom att vara vanligt vid fil m och TV även introducerats inom bilindustrin Min slutsats är att en bedömning huruvida vad som är enkelt kontra det som var besvärligt vid mixning av filmmusik i Surround är högst subjektivt. Mixar man filmmusik bör man vara noggrann med volym och dynamik, så att man inte stör filmens handling och dialog. Ett bra tips är att låta någon annan bedöma och ge sin feedback innan man lämnar ifrån sig arbetet. Vill man arbeta så effektiv som möjligt och spara tid bör man enligt min mening dela in kanalerna i olika grupper, då man arbetar mycket med automatiseringar.

Advances in microfluidics have led to the development of devices which can perform simple operations on fluids with the aim of developing a fully integrated "lab-on-a-chip". Of prime importance to this procedure is the efficient operation of each individual component. Using theoretical prediction sand two-dimensional Molecular Dynamics (MD) simulations, we have explored the operation of two such devices: one which forces a cavity of fluid into rotational motion and one to mix two different fluid species. For the rotational operation, we have referred to experimental results for a circular cavity coupled to a microfluidic channel in which a laminar flow is induced. This flow causes the fluid in the cavity to rotate which we model with MD simulations. We examine the role of wall-fluid interactions and its effect on enhancing the amount of angular momentum generated in the cavity. The reduction in wall-fluid interaction allows the fluid to slip along the wall and acquire a greater level of spin. We hope this technique can be applied experimentally to enhance the rotation in these devices. For the mixing operation, we examined a previously studied theoretical system where the authors claim obstacles in microchannels increase mixing efficiency for a fluid composed of two species. We make theoretical predictions to the contrary and demonstrate, using MD simulations, that our predictions are correct. Our results show that obstacles have two effects. First, obstacles increase the amount of contact between fluid species which only has a negligible effect on increasing the mixing efficiency. Second, the obstacles flatten the normally Poiseuille (quadratic) flow profile over a finite channel length which decreases the distance required for partial but not complete mixing. We demonstrate that all channels of at least a certain length, defined by the diffusive properties of the channel, will reach full mixing at the same point. Both projects illustrate the utility of MD simulations in predicting fluid behaviour in microfluidic systems. Our aim is that these studies can be integrated into the greater body of knowledge pertaining to microfluidics.

This thesis is an investigation of the subject of extra dimensions in particle physics. In recent years, there has been a large interest in this subject. In particular, a number of models have been suggested that provide solutions to some of the problem with the current Standard Model of particle physics. These models typically give rise to experimental signatures around the TeV energy scale, which means that they could be tested in the next generation of high-energy experiments, such as the LHC. Among the most important of these models are the universal extra dimensions model, the large extra dimensions model by Arkani-Hamed, Dimopolous, and Dvali, and models where right-handed neutrinos propagate in the extra dimensions. In the thesis, we study phenomenological aspects of these models, or simple modifications of them. In particular, we focus on Kaluza–Klein dark matter in universal extra dimensions models, different aspects of neutrino physics in higher dimensions, and collider phenomenology of extra dimensions. In addition, we consider consequences of the enhanced renormalization group running of physical parameters in higher-dimensional models.
QC 20120427

In this work we provide several improvements in the study of phase transitions of interacting particle systems: - We determine a quantitative relation between non-extremality of the limiting Gibbs measure of a tree-based spin system, and the temporal mixing of the Glauber Dynamics over its finite projections. We define the concept of 'sensitivity' of a reconstruction scheme to establish such a relation. In particular, we focus on the independent sets model, determining a phase transition for the mixing time of the Glauber dynamics at the same location of the extremality threshold of the simple invariant Gibbs version of the model. - We develop the technical analysis of the so-called spatial mixing conditions for interacting particle systems to account for the connectivity structure of the underlying graph. This analysis leads to improvements regarding the location of the uniqueness/non-uniqueness phase transition for the independent sets model over amenable graphs; among them, the elusive hard-square model in lattice statistics, which has received attention since Baxter's solution of the analogous hard-hexagon in 1980. - We build on the work of Montanari and Gerschenfeld to determine the existence of correlations for the coloring model in sparse random graphs. In particular, we prove that correlations exist above the 'clustering' threshold of such a model; thus providing further evidence for the conjectural algorithmic 'hardness' occurring at such a point.

This thesis consists of four chapters. Chapters 1 and 2 are somewhat related in the sense that they deal with similar dynamical systems. Each chapter comes complete with its own references and notations. For the convenience of the reader, we provide an introduction and indeed an elongated summary to the whole thesis in Chapter 0. In Chapter 1, we study how closed orbits of a subshift of finite type hits to a finite homogeneous extension. In particular, we obtain an asymptotic formula for the number of closed orbits according to how they lift to the extension space. We apply our findings to the case of finite extensions and also to automorphism extensions of hyperbolic toral automorphisms. Chapter 2 deals with lifting ergodic properties of an arbitrary measure preserving transformation T to homogeneous extensions of T. Our results extends well known theorems already obtained for the case of compact group extensions of measure-preserving transformations. We also give simplified results to the special case when the base transformation is a Markov shift and the skewing-function depends on a finite number of coordinates. In Chapter 3, we look at the rate of mixing of rectangle sets of two dimensional Markov shifts with respect to the natural shift actions. We show that if one of the matrix defining the Markov measure is aperiodic then this rate is exponentially fast. We provide an example to illustrate what could happen in general.

Un des objectifs du Femtomagnetisme est de contrôler l’aimantation des matériaux avec des impulsions laser femtoseconde. Il a été démontré qu’une réponse magnéto-optique (MO) cohérente a lieu avant la thermalisation des populations de spins dans une configuration pompe-sonde MOKE. Elle résulte du couplage cohérent spin-photon dû à l’interaction spin-orbite. Une description simplifiée de cet effet a été faite en tenant compte d’un système à huit niveaux couplés au champ laser. La cohérence MO est définie par le temps de déphasage dépendent du champ T2MO. Dans ce travail, il est montré que la réponse MO cohérente d’un grenat dopé au bismuth peut être mesurée directement avec différentes configurations de mélange à quatre ondes MO. L’importance de connaître la phase spectrale de l’impulsion pour obtenir T2MO a été étudié. Avec des impulsions de 10fs dans le proche infra-rouge, une mesure de T2MO donne (2.8+/-1)fs, c. à d., du même ordre de grandeur que le temps de déphasage des charges
One of the goals of Femtomagnetism is to manipulate the magnetization of materials using femtosecond optical pulses. It has been shown in ferromagnetic films that a magneto-optical (MO) coherent response takes place before the thermalization of the spins populations in a pump and probe MOKE experiment. It results from the coherent spin-photon coupling mediated by the spin-orbit interaction. A simplified description of this effect has been made by considering an eight-level system coupled with the laser field. The MO coherence can be defined by the magnetic field dependent dephasing time T2MO. In the present work, it is shown that the coherent MO response of a bismuth-doped garnet can be directly measured in different degenerated MO four-wave mixing configurations. The importance of well-knowing the spectral phase of the pulse to measure T2MO was studied. Using 10fs near infra-red pulses, T2MO was shown to be (2.8+/-1)fs that is of the same order of the charges dephasing time

Le travail qui suit comporte quatre chapitres : le premier est centré autour de la propriété de mélange faible pour les échanges d'intervalles et flots de translation. On y présente des résultats obtenus avec Artur Avila qui renforcent des résultats précédents dus à Artur Avila et Giovanni Forni. Le deuxième chapitre est consacré à un travail en commun avec Zhiyuan Zhang et concerne les propriétés d'ergodicité et d'accessibilité stables pour des systèmes partiellement hyperboliques de dimension centrale au moins égale à deux. On montre que sous des hypothèses de cohérence dynamique, center bunching et pincement fort, la propriété d'accessibilité stable est dense en topologie C^r, r>1, et même prévalente au sens de Kolmogorov. Dans le troisième chapitre, on expose les résultats d'un travail réalisé en collaboration avec Julie Déserti, consacré à l'étude d'une famille à un paramètre d'automorphismes polynomiaux de C^3 ; on montre que de nouveaux phénomènes apparaissent par rapport à ce qui était connu dans le cas de la dimension deux. En particulier, on étudie les vitesses d'échappement à l'infini, en montrant qu'une transition s'opère pour une certaine valeur du paramètre. Le dernier chapitre est issu d'un travail en collaboration avec Jiangong You, Zhiyan Zhao et Qi Zhou ; on s'intéresse à des estimées asymptotiques sur la taille des trous spectraux des opérateurs de Schrödinger quasi-périodiques dans le cadre analytique. On obtient des bornes supérieures exponentielles dans le régime sous-critique, ce qui renforce un résultat précédent de Sana Ben Hadj Amor. Dans le cas particulier des opérateurs presque Mathieu, on montre également des bornes inférieures exponentielles, qui donnent des estimées quantitatives en lien avec le problème dit "des dix Martinis". Comme conséquences de nos résultats, on présente des applications à l'homogénéité du spectre de tels opérateurs ainsi qu'à la conjecture de Deift
The following work contains four chapters: the first one is centered around the weak mixing property for interval exchange transformations and translation flows. It is based on the results obtained together with Artur Avila which strengthen previous results due to Artur Avila and Giovanni Forni. The second chapter is dedicated to a joint work with Zhiyuan Zhang, in which we study the properties of stable ergodicity and accessibility for partially hyperbolic systems with center dimension at least two. We show that for dynamically coherent partially hyperbolic diffeomorphisms and under certain assumptions of center bunching and strong pinching, the property of stable accessibility is dense in C^r topology, r>1, and even prevalent in the sense of Kolmogorov. In the third chapter, we explain the results obtained together with Julie Déserti on the properties of a one-parameter family of polynomial automorphisms of C^3; we show that new behaviours can be observed in comparison with the two-dimensional case. In particular, we study the escape speed of points to infinity and show that a transition exists for a certain value of the parameter. The last chapter is based on a joint work with Jiangong You, Zhiyan Zhao and Qi Zhou; we get asymptotic estimates on the size of spectral gaps for quasi-periodic Schrödinger operators in the analytic case. We obtain exponential upper bounds in the subcritical regime, which strengthens a previous result due to Sana Ben Hadj Amor. In the particular case of almost Mathieu operators, we also show exponential lower bounds, which provides quantitative estimates in connection with the so-called "Dry ten Martinis problem". As consequences of our results, we show applications to the homogeneity of the spectrum of such operators, and to Deift's conjecture

Esta tese apresenta uma análise estatística detalhada dos dados de experimentos com neutrinos solares mais recentes, com duas diferentes soluções para oscilações de neutrinos, ambas caracterizadas por um grande comprimento de oscilação. A primeira baseada no mecanismo de oscilação padrão, ou seja, induzida por massa, sendo esta estudada nos casos de duas e três gerações e dentro do regime de quase-vácuo. E a segunda, uma exótica, que usa como mecanismo de oscilação uma possível violação do princípio de equivalência, que foi analisada somente para o caso de duas gerações, sendo este discutido para transições entre neutrinos ativos, e entre neutrinos ativos e estéreis. Nossos resultados mostraram que ambas soluções são consistentes com os dados de neutrinos solares e, também, no caso específico do quase-vácuo, observamos que a hipótese de três gerações ficou desfavorecida.
This thesis presents a well detailed statistical analysis using the recent data from solar neutrino experiments. This analysis was done in the framework of two different solutions of neutrino oscillations, both characterized by a long oscillation wavelength. The first was based on the standard mass induced oscillation mechanism, here we worked in the scheme of two and three neutrino generations within the quasivacuum regime. The second was an exotic mechanism, where the neutrino oscillation is due to a possible breakdown of the equivalence principle, this alternative was analyzed only for two neutrino generations, in the cases for the conversion among active neutrino and active to sterile neutrino. Our results show a good agreement between the solar neutrino data and both solutions, also in the specific case of quasivacuum, we found that the hypothesis for the three neutrino generation is disfavored.

Civil Engineering
Ph.D.
The longitudinal solute transport modeling is critical in river and stream water quality management, control, and the mitigation of hazardous riverine spills. One of the widely used "deadzone" model is the transient storage model (TSM). TSM is a significant improvement over the advection-dispersion model (ADM), but it cannot simulate the breakthrough curve (BTC) immediately after a large pool. Additionally, the calibration (parameterization) method is challenged by the non-identifiability which is common to all inverse modeling, and it seems TSM cannot be easily used as a predictive tool, more of an interpretive tool of solute transport, i.e., is the parameter set calibrated via inverse modeling transferable? Pools are fundamental stream morphology unit in streams with mixed bed materials in pool-riffle or pool-step sequences. Understanding of how a pool impacts the longitudinal solute transport is the first step towards improving current model such as TSM or developing new models. By introducing a dimensionless group, e= Q/(Dt W) (where, Q is the average volumetric flow rate; Dt is an average transverse dispersion coefficient; W is the channel flow width), derived from non-dimensionalization of the governing equations of one of the most rigorous 2-dimansional (2D) (depth-averaged) model, Mike21, this work presents an alternative way of longitudinal solute transport investigation. Using the 2D fully hydrodynamic Mike21, numerical experiments were conducted on hypothetical streams in this dissertation. Simulation study on hypothetical stream with pool reveals that a pool's effects on longitudinal solute transport are manifested by three aspects: boosting longitudinal spreading (concentration peak attenuation), causing a solute plume delay and increasing solute residence time. These effects fade like a "wake" as the solute plume moves downstream. e provides an insight into the physics of longitudinal transport; it outlines a relative transverse mixing intensity of a stream. The internal transport and mixing condition (including the secondary circulations) in a pool together with the pool's dimensions determine the pool's storage effects especially when e >>1. The BTCs downstream from a pool may be "heavy tailed" (i.e., have enormously slow decaying rate) which cannot be modeled by the TSM. Results also suggest that the falling limb of a BTC more accurately characterizes the pool's storage effects because the corresponding solute has more chance to sample the entire storage area. n a more fundamental perspective, the predictive ability of inverse modeling parameterized model is discussed and conclusion is made about the role of a stream/river system's nonlinearity in determining the predictability; a misleading mis-nomenclature in TSM application is also demonstrated with a numerical experiment.
Temple University--Theses

L’approximation dite « anélastique » permet de filtrer les ondes acoustiques grâce à un développement asymptotique deséquations de Navier-Stokes, réduisant ainsi le pas en temps moyen, lors de la simulation numérique du développement d’instabilités hydrodynamiques. Ainsi, les équations anélastiques sont établies pour un mélange de deux fluides pour l’instabilité de Rayleigh-Taylor. La stabilité linéaire de l’écoulement est étudiée pour la première fois pour des fluides parfaits, par la méthode des modes normaux, dans le cadre de l’approximation anélastique. Le problème de Stokes issu des équations de Navier-Stokes sans les termes non linéaires (une partie de la poussée d’Archiméde est prise en compte) est défini ; l’éllipticité est démontrée, l’étude des modes propres et l’invariance liée à la pression sont détaillés. La méthode d’Uzawa est étendue à l’anélastique en mettant en évidence le découplage des vitesses en 3D, le cas particulier k = 0 et les modes parasites de pression. Le passage au multidomaine a permis d’établir les conditions de raccord (raccord Co de la pression sans condition aux limites physiques). Les algorithmes et l’implantation dans le code AMENOPHIS sont validés par les comparaisons de l’opérateur d’Uzawa développé en Fortran et à l’aide de Mathematica. De plus des résultats numériques ont été comparés à une expérience avec des fluides incompressibles. Finalement, une étude des solutions numériques obtenues avec les options anélastique et compressible a été menée. L’étude de l’influence de la stratification initiale des deux fluides sur le développement de l’instabilité de Rayleigh-Taylor est amorcée
The « anelastic » approximation allows us to filter the acoustic waves thanks to an asymptotic development of the Navier-Stokes equations, so increasing the averaged time step, during the numerical simulation of hydrodynamic instabilitiesdevelopment. So, the anelastic equations for a two fluid mixture in case of Rayleigh-Taylor instability are established.The linear stability of Rayleigh-Taylor flow is studied, for the first time, for perfect fluids in the anelastic approximation.We define the Stokes problem resulting from Navier-Stokes equations without the non linear terms (a part of the buoyancyis considered) ; the ellipticity is demonstrated, the eigenmodes and the invariance related to the pressure are detailed.The Uzawa’s method is extended to the anelastic approximation and shows the decoupling speeds in 3D, the particular casek = 0 and the spurius modes of pressure. Passing to multidomain allowed to establish the transmission conditions.The algorithms and the implementation in the existing program are validated by comparing the Uzawa’s operator inFortran and Mathematica langages, to an experiment with incompressible fluids and results from anelastic and compressiblenumerical simulations. The study of the influence of the initial stratification of both fluids on the development of the Rayleigh-Taylor instability is initiated

Semiconductor nanostructures exhibit many remarkable electronic and optical properties. The key to designing and utilising semiconductor quantum structures is a physical understanding of the detailed excitation, transport and energy relaxation processes. Thus the nonequilibrium dynamics of semiconductor quantum structures have attracted extensive attention in recent years. Ultrafast spectroscopy has proven to be a versatile and powerful tool for investigating transient phenomena related to the relaxation and transport dynamics in semiconductors. In this thesis, we report investigations into the electronic and optical properties of various semiconductor quantum systems using a variety of ultrafast techniques, including up-conversion photoluminescence, pump-probe, photon echoes and four-wave mixing. The semiconductor quantum systems studied include ZnO/ZnMgO multiple quantum wells with oxygen ion implantation, InGaAs/GaAs self-assembled quantum dots with different doping, InGaAs/InP quantum wells with proton implantation, and silicon quantum dots. The spectra of these semiconductor nanostructures range from the ultraviolet region, through the visible, to the infrared. In the UV region we investigate excitons, biexcitons and oxygen implantation effects in ZnO/ZnMgO multi-quantum wells using four-wave mixing, pump-probe and photoluminescence techniques. Using time-resolved up-conversion photoluminescence, we investigate the relaxation dynamics and state filling effect in InGaAs self-assembled quantum dots with different doping, and the implantation effect in InGaAs/InP quantum wells. Finally, we study the optical properties of silicon quantum dots using time-resolved photoluminescence and photon echo spectroscopy on various time scales, ranging from microseconds to femtoseconds.

Etude des processus de relaxation dephasante (t2) de molecules de colorant (cresyl violet) dissoutes dans 1 film mince de colle cellulosique en fonction de la temperature. Utilisation d'une technique d'optique non lineaire, de type melange a 4 ondes: la spectroscopie coherente en lumiere incoherente. Afin d'interpreter les resultats, mise au point d'un 1er modele assimilant le niveau excite a un continuum d'etats vibrationnels, calcul considere comme etape preliminaire d'un calcul plus sophistique. Elaboration d'un 2eme modele decrivant l'action d'une excitation non lineaire sur un systeme a 2 niveaux en prenant en consideration les effets de bord des bande et d'ecart a la resonance. 2 valeurs du parametre t2 en fonction de la temperature sont deduites

碩士
國立中央大學
土木工程研究所
91
Abtract The scope of this research are : (1) measure the basic properties of MSWI bottom ash; (2) study the solution to improve the expansion problem resulted from the gas production after mixing the bottom ash with cement; (3) investigate the methods to accelerate the setting time of bottom ash contained mortar due to the retardation of cement hydration induced from the organic matter in the ash. Test results show that the generation of hydrogen resulted from the reaction of the aluminum contained in the bottom ash with alkaline or acidic solution might be the source of gas production to induce mortar expansion. Spray sodium hydroxide or phosphoric acid on the bottom ash could reduce the gas production. However, immerse the bottom ash in sodium hydroxide or phosphoric acid solution would abtain better efficiency of gas reduction. Both reincinerate the bottom ash and washing the bottom ash by sodium hydroxide solution could accelerate the setting time and inicrease the strength development of the mortar contained ash due to the reduction of organic matter in the ash. Keywords: Bottom ash; expansion; Reincineration

In this dissertation, we introduce new families of valid inequalities for general linear mixed integer programs (MIPs) and second-order conic MIPs (SOCMIPs) and establish several theoretical properties and computational effectiveness of these inequalities. First we introduce the mixed n-step mixed integer rounding (MIR) inequalities for a generalization of the mixing set which we refer to as the n-mixing set. The n-mixing set is a multi-constraint mixed integer set in which each constraint has n integer variables and a single continuous variable. We then show that mixed n-step MIR can generate multi-row valid inequalities for general MIPs and special structure MIPs, namely, multi- module capacitated lot-sizing and facility location problems. We also present the results of our computational experiments with the mixed n-step MIR inequalities on small MIPLIB instances and randomly generated multi-module lot-sizing instances which show that these inequalities are quite effective. Next, we introduce the n-step conic MIR inequalities for the so-called polyhedral second-order conic (PSOC) mixed integer sets. PSOC sets arise in the polyhedral reformulation of SOCMIPs. We first introduce the n-step conic MIR inequality for a PSOC set with n integer variables and prove that all the 1-step to n-step conic MIR inequalities are facet-defining for the convex hull of this set. We also provide necessary and sufficient conditions for the PSOC form of this inequality to be valid. Then, we use the aforementioned n-step conic MIR facet to derive the n-step conic MIR inequality for a general PSOC set and provide conditions for it to be facet-defining. We further show that the n-step conic MIR inequality for a general PSOC set strictly dominates the n-step MIR inequalities written for the two linear constraints that define the PSOC set. We also prove that the n-step MIR inequality for a linear mixed integer constraint is a special case of the n-step conic MIR inequality. Finally, we conduct a polyhedral study of the triplet formulation for the single row facility layout problem (SRFLP). For any number of departments n, we prove that the dimension of the triplet polytope (convex hull of solutions to the triplet formulation) is n(n - 1)(n - 2)/3. We then prove that several valid inequalities presented in Amaral (2009) for this polytope are facet-defining. These results provide theoretical support for the fact that the linear program solved over these valid inequalities gives the optimal solution for all instances studied by Amaral (2009).