Dissertations / Theses on the topic 'Free particle'

Thesis (M.S. in Physics)--Naval Postgraduate School, December 1990.<br>Thesis Advisor(s): Colson, William B. Second Reader: Maruyama, Xavier K. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): Free Electron Lasers, Computerized Simulations, Parmela Computer Programs, Cray Computers, Theses. Author(s) subject terms: Free Electron Lasers, Computerized Simulation. Includes bibliographical references (p. 52-53). Also available in print.

This study aims to deduce an appropriate shape and density for an electronic free-cell that could be placed into a silo so that position and other desired physical parameters could be recorded. To determine how density and shape affects the trajectory and displacement of free cells, the trajectory and displacement of cylindrical, cuboid and triangular prism free-cells of equivalent volume was investigated in a discharging quasi 3D silo slice. The free-cells were placed at twelve different starting positions spread evenly over one half of the 3D slice. Tests were conducted using a monosized batch of spherical particles with a diameter of approximately 5 mm. Tests were also conducted in a binary mixture consisting of particles of different sizes (5 mm/4 mm) and the same density (1.28 g/cm3) and a binary mixture consisting of particles of different size (6 mm/5 mm) and different densities (1.16 g/cm3/1.28 g/cm3).The rotation of the free cells was also briefly discussed.Computer simulations were conducted using the Discrete Element Method (DEM). The simulation employed the spring-slider-dashpot contact model to represent the normal and tangential force components and the modified Euler integration scheme was applied to calculate the particle velocities and positions at each time step. One trial of each of the metal and plastic, cylindrical, cuboid and triangular prism free cells was compared with the average of three experimental trials. The trajectory and displacement of a representative particle positioned at the same starting position as the free cell was also obtained from DEM simulation and compared with the path and displacement of each of the free cells to determine which free cell followed the particle most closely and hence to determine a suitable free cell that would move with the rest of the grains. Spherical particles are idealised particles. Therefore tests were also conducted with a small number of polyhedral particles, to deduce their flow rate and the critical orifice width at which blockages were likely to form. Simulations were also conducted to test the feasibility of the DEM in modelling the behaviour of these polyhedral particles.Results indicate that for a free cell to move along the same trajectory and have the same displacement and velocity as an equivalent particle in the batch it should have a similar density to the majority of the other particles. A cylindrical free cell of similar density to the particles was found to follow the path of the representative particle more closely than the cuboid or triangular prism. Polyhedral particles were found to have a greater flow rate than spherical particles of equivalent volume.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 306-309).<br>Smoothed Particle Hydrodynamics (SPH) is a simple and attractive meshless Lagrangian particle method with applications in many fields such as astrophysics, hydrodynamics, magnetohydrodynamics, gas explosions, and granular flows that has demonstrated ability to simulate highly non-linear free-surface flows including wave overturning, jets, and the formation of spray and droplets. Despite the increasing popularity and promise of the method, SPH has a number of key issues that must be overcome before the method can realize its full potential in scientific and engineering applications: it is of low order, requires a high degree of tuning, and is inherently unstable. Additionally, there exists little analytic basis or fundamental understanding of the method to guide the many ad-hoc tuning and empirical fixes. The objective of this thesis is to perform an analytical and numerical investigation of the SPH method for free-surface flows. To this end, we perform a quantitative, unified analysis of the numerical method and the physics it captures, and we assess the method's consistency, stability, and convergence. It is shown that SPH introduces spurious solutions dominant in the dynamics of the solution making quantities such as velocity and pressure essentially unusable without filtering. It is also shown that the method is consistent inside the domain but imposes spurious, leading order, dynamic free-surface boundary conditions which alter the flow and further permit the introduction of spurious solutions. We further extend the analysis to address the effects of different empirical SPH treatments introduced in the literature, classifying these respectively as accuracy, consistency, or stability treatments, and characterizing their effectiveness. Based on the findings of the analysis, we eliminate the tuneable and empirical nature of the method by providing rational guidelines for the usage and effects of the relevant SPH treatments. Finally, we propose a modified SPH method that maintains the key features of SPH and significantly reduces spurious errors present in current SPH implementations. This thesis is among the first to provide a unified systematic analysis of the SPH method, shedding insight into the many proposed variations and fixes, and informs and guides new rational improvements to the method. This work lays the foundation for the development of SPH as a valuable engineering tool in the study of violent free-surface flows.<br>by Areti Kiara.<br>Ph.D.

Geophysical massive flows as snow avalanches and debris flows are characterized by a wide grain size distribution. The interactions between particles among the granulometric classes are a consequent of a such large distribution. However, most of the studies on the geophysical massive flows assume the simplifying hypothesis of a constant granulometry. The aim of this work is studying the coexistence of two granulometric classes in statistically stationary and homogeneous conditions and investigating the physical processes responsible for the particles transfer. Experimental investigations using two different grain size classes were conducted to reproduce the two-phases mixture. The granular material was recirculated in a close system and the experiments were carried out in a laboratory flume having a loose two size granular bed. A proper optical technique was innovatively improved to obtain the average and instantaneous values of the velocity and concentration from the side-walls. Through these values, the average particle profiles of velocity, concentration and granular temperature of the two solid fractions were computed. Moreover, the instantaneous values provide the average profiles of the second order correlation of the variables, such as the component of the granular temperature and the fluctuating components of the velocity and the concentration. The average distribution profiles in time of velocity and concentration prove the statistically stationary and homogeneous condition in a stretch sufficiently long of the running flow. Moreover, two types of regimes were identified: in case of low and intermediate discharges, the frictional regime nearly prevails at the free surface; for high discharges there is a coexistence across the flow depth of two regimes, the frictional regime in the intermediate flow-depth region and the collisional regime in the free surface. The existence of a vertical velocity component of both phases brings to hypothesize the presence of secondary circulations in the flow.

Geophysical massive flows as snow avalanches and debris flows are characterized by a wide grain size distribution. The interactions between particles among the granulometric classes are a consequent of a such large distribution. However, most of the studies on the geophysical massive flows assume the simplifying hypothesis of a constant granulometry. The aim of this work is studying the coexistence of two granulometric classes in statistically stationary and homogeneous conditions and investigating the physical processes responsible for the particles transfer. Experimental investigations using two different grain size classes were conducted to reproduce the two-phases mixture. The granular material was recirculated in a close system and the experiments were carried out in a laboratory flume having a loose two size granular bed. A proper optical technique was innovatively improved to obtain the average and instantaneous values of the velocity and concentration from the side-walls. Through these values, the average particle profiles of velocity, concentration and granular temperature of the two solid fractions were computed. Moreover, the instantaneous values provide the average profiles of the second order correlation of the variables, such as the component of the granular temperature and the fluctuating components of the velocity and the concentration. The average distribution profiles in time of velocity and concentration prove the statistically stationary and homogeneous condition in a stretch sufficiently long of the running flow. Moreover, two types of regimes were identified: in case of low and intermediate discharges, the frictional regime nearly prevails at the free surface; for high discharges there is a coexistence across the flow depth of two regimes, the frictional regime in the intermediate flow-depth region and the collisional regime in the free surface. The existence of a vertical velocity component of both phases brings to hypothesize the presence of secondary circulations in the flow.

In the past 10 years there has been a significant amount of research into two-phase particle transport. The terrorist events of September 11, 2001 sparked a series of studies analyzing particle entrainment and deposition in turbulent airflows. One area of research needing further attention has been the study of particles entrained in axisymmetric air jets. An experimental rig was designed and built to study entrainment properties and deposition of Newtonian particles, after injection into a turbulent axisymmetric free air jet. Newtonian spherical particles, ranging from 1mm to 6mm in diameter, were injected into a turbulent airstream and blown through a nozzle into a large, open space. As the particles fell out of the jet stream, their linear distances, from nozzle to initial-ground-contact, were recorded and analyzed. The experiments conducted indicated particle size and density to be significant factors when considering Newtonian particle entrainment. Additionally, particle deposition distribution revealed a consistent positive skewness, as opposed to an expected Gaussian form. The data presented in this paper provide a starting point for understanding entrainment of Newtonian spherical particles in jets. The simple experimental rig geometry and results also provide an opportunity for computational fluid dynamics models to be validated, answering a call from the 2006 Annual Review of Fluid Mechanics.<br>Master of Science

Thesis (M.Sc.Eng.)<br>To determine satellite trajectories in low earth orbit, engineers need to adequately estimate aerodynamic forces. But to this day, such a task su↵ers from inexact values of drag forces acting on complicated shapes that form modern spacecraft. While some of the complications arise from the uncertainty in the upper atmosphere, this work focuses on the problems in modeling the flow interaction with the satellite geometry. The only numerical approach that accurately captures e↵ects in this flow regime—like self-shadowing and multiple molecular reflections—is known as Test Particle Monte Carlo. This method executes a ray-tracing algorithm to follow particles that pass through a control volume containing the spacecraft and accumulates the momentum transfer to the body surfaces. Statistical fluctuations inherent in the approach demand particle numbers on the order of millions, often making this scheme too costly to be practical. This work presents a parallel Test Particle Monte Carlo method that takes advantage of both graphics processing units and multi-core central processing units. The speed at which this model can run with millions of particles enabled the exploration of regimes where a flaw was revealed in the model’s initial particle seeding. A new model introduces an analytical fix to this flaw—consisting of initial position distributions at the boundary of a spherical control volume and an integral for the correct number flux—which is used to seed the calculation. This thesis includes validation of the proposed model using analytical solutions for several simple geometries and demonstrates uses of the method for the aero-stabilization of the Phobos-Grunt Martian probe and pose-estimation for the ICESat mission.<br>2031-01-01

Geophysical granular flows, such as snow avalanches, pyroclastic density currents, mudslides and debris flows, can be extremely hazardous to local populations, and understanding their complex behaviour remains an important challenge. This project aims to provide insight into these events by exploring different aspects in isolation, using a combination of mathematical theory, numerical simulations and small-scale experiments. Firstly, the effect of lateral confinement is examined by studying granular material moving in an inclined chute. This can have applications to natural releases flowing down confined valleys or conduits, and the relative simplicity of the geometry also provides a useful test case for new theoretical models. One such model is the recent depth-averaged μ(I)-rheology, which, because of the viscous terms introduced into the depth-averaged momentum balance, may be described as an intermediate approach between full constitutive laws and classical shallow-water-type equations for dense granular flows. Here, a generalisation of the new system to two spatial dimensions is described, and the resulting viscous equations are able to capture the cross-slope curvature of the downslope velocity profiles in steady uniform chute flows. This may be regarded as major progress compared to traditional hyperbolic models, which only admit constant velocity solutions. Particle size-segregation in geophysical granular flows is then investigated, which can cause important feedback on the overall bulk properties as it can lead to the development of regions with different frictional properties. A particularly striking example is segregation-induced 'finger' formation, where large particles are segregated to the flow surface and sheared to form a resistive coarse-rich front, which is unstable and spontaneously breaks down into a series of lobate structures. These travel both faster and further than one might anticipate. To model such segregation-mobility feedback effects, the depth-averaged μ(I)-rheology is extended to bidisperse flows by coupling with a depth-integrated model for size-segregation. The system of equations remains mathematically well-posed and is able to qualitatively capture finger formation, with the newly-introduced viscous terms controlling the characteristics of the leveed channels that develop. A more subtle segregation effect is studied in bidisperse roll waves, which form as small irregularities merge and coarsen as they move downslope, eventually growing into destructive large amplitude pulses. Experimental measurements show lateral, as well as vertical, segregation profiles, with the coarser grains accumulating at the fastest moving wave crests. The disturbances that form in mixtures with higher proportions of large particles grow more slowly, leading to smaller amplitude waves that travel at slower speeds, and the new coupled model predicts qualitatively similar behaviour. Finally, the influence of complex topography is investigated. A smooth two-dimensional bump is placed across the width of a chute, which, depending on the initial conditions, can lead to the formation of an airborne jet or granular shock at steady state. A simple depth-averaged model in a curvilinear coordinate system following the topography accurately captures both regimes, and represents a significant improvement on using an aligned Cartesian approach.

Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(工学)<br>甲第14147号<br>工博第2981号<br>新制||工||1442(附属図書館)<br>26453<br>UT51-2008-N464<br>京都大学大学院工学研究科都市環境工学専攻<br>(主査)教授 後藤 仁志, 教授 細田 尚, 准教授 牛島 省<br>学位規則第4条第1項該当

This thesis investigates wave loading on bodies in the free surface using smoothed particle hydrodynamics (SPH). This includes wave loading on fixed bodies, waves generated by heaving bodies in still water and the heave response of a body in waves, representing a wave energy device. SPH is a flexible Lagrangian technique for CFD simulations, which in principle applies to steep and breaking waves without special treatment allowing us to simulate highly nonlinear and potentially violent flows encountered in a real sea. However few detailed tests have been undertaken even with small amplitude waves.This research uses the open-source SPH code SPHysics. First two forms of SPH formulation, standard SPH with artificial viscosity and SPH-Arbitrary Lagrange Euler (ALE) with a Riemann solver, are used to simulate progressive waves in a 2-D tank. The SPH-ALE formulation with a symplectic time integration scheme and cubic spline kernel is found to model progressive waves with negligible dissipation whereas with the standard SPH formulation waves decay markedly along the tank. We then consider two well-defined test cases in two dimensions: progressive waves interacting with a fixed cylinder and waves generated by a heaving semi-immersed cylinder. To reduce computer time in a simple manner a variable particle mass distribution is tested with fine resolution near the body and coarse resolution further away, while maintaining a uniform kernel size. A mass ratio of 1:4 proved effective but increasing to 1:16 caused particle clumping and instability. For wave loading on a half-submerged cylinder the agreement with the experimental data of Dixon et al. (1979) for the root mean square force is within 2%. For more submerged cases, the results show some discrepancy, but this was also found with other modelling approaches. For the heaving cylinder, SPH results for the far field wave amplitude and vertical force on the cylinder show good agreement with the data of Yu and Ursell (1961). The variable mass distribution leads to a computer run time speedup of nearly 200% in these cases on a single CPU. The results of the vertical force and wave amplitude are shown to be quite sensitive to the value of the slope limiter in the Riemann solver for the 2-D heaving cylinder problem. A heaving 2-D wedge or 3-D cone whose oscillatory vertical motion is prescribed as the elevation of a focused wave group is a precise test case for numerical free-surface schemes. We consider two forms of repulsive boundary condition (Monaghan & Kos, 1999, and Rogers et al., 2008) and particle boundary force (Kajtar and Monaghan, 2009) for the 2-D wedge case, comparing the result with the experimental data of Drake et al. (2009). The repulsive boundary condition was more effective than the particle boundary force method. Variable particle mass with different kernel sizes was then tested for 2-D problems for mass ratios of 1:4, 1:16 and 1:4:16 with satisfactory results without particle clumping and instability. For the 3-D cone case, SPH reproduces the experimental results very closely for the lower frequency tested where there is no separation from the bottom surface of the body but for the higher frequencies the magnitudes of force minima were underestimated. The mass ratios of 1:8 and 1:8:27 in two and three nested regions are tested for the 3-D cone problem where a computer run time speedup of nearly 500% is achieved on 16 processors for the mass ratio of 1:8.Finally, the floating body of a heaving wave energy device known as the Manchester Bobber is modelled in extreme waves without power take-off. The results for a single float are in approximate agreement with the experiment.

This thesis presents the formulation of a Smoothed Particle Hydrodynamics (SPH) model and its application to a range of engineering applications. The motivation for this research lies in the desire to accurately model viscous and turbulent free-surface flows, including those with complete break-up of the free-surface. At present, boundary element modelling is typically chosen to describe free-surface flows where viscous effects are not important. The Volume of Fluid method is able to model most flow phenomena, but the representation of the free-surface is insuffcient for the most complex flows. Current SPH models have shown aptitude for modelling such flows, but there is a noticeable lack of validation carried out in the literature. This thesis includes a thorough investigation into established modelling techniques, extending or developing new techniques where necessary, in order to create a versatile and accurate SPH model for free-surface flows. Where possible, quantitative comparisons with experimental observations have been carried out to ensure a suitable level of accuracy has been achieved. First, a fairly basic SPH model is constructed through testing its ability to generate and propagate solitary waves in a numerical wave flume. This is succeeded by a thorough investigation into solitary waves breaking on a 5° slope, through which further developments are added to the SPH model. The full process, including overturning, post-breaking behaviour, run-up, and the subsequent hydraulic jump are quantitatively compared with experimental measurements. The work carried out in this thesis shows that the SPH model can successfully capture violent free-surface flows with large deformations from the initial surface geometry. Validation studies demonstrate that SPH can form an important part of model testing for engineering developments involving these types of flows.

Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2004.<br>Ludovice, Peter, Committee Chair; Lee, Jay, Committee Member; Meredith, Carson, Committee Member; Morris, Jeff, Committee Member; Neitzel, Paul, Committee Member. Vita. Includes bibliographical references (leaves 120-123).

There is a growing need for the clean generation of electricity in the world, and increased efficiency is one way to achieve cleaner generation. Increased efficiency may be achieved through an improved understanding of the heat flux of participating media in combustion environments. Real-time in-situ optical measurements of gas temperature and concentrations in combustion environments is needed. Optical methods do not disturb the flow characteristics and are not subject to the temperature limitation of current methods. Simpler, less-costly optical measurements than current methods would increase the ability to apply them in more circumstances. This work explores the ability to simultaneously measure gas temperature and H2O concentration via integrated spectral intensity ratios in regions where H2O is the dominant participating gas. This work considered combustion flows with and without fuel and soot particles, and is an extension of work previously performed by Ellis et al. [1]. Five different combustion regimes were used to investigate the robustness of the infrared intensity integral method first presented by Ellis et al. [1]. These included Post-Flame Natural Gas (PFNG), Post-Flame Medium Wood (PFMW), Post-Flame Fine Wood (PFFW), In-Flame Natural Gas (IFNG), and In-Flame Fine Wood (IFFW). Optical spectra were collected as a function of path length for each regime. Methods for processing the spectra to obtain gas temperature, gas concentration, broadband temperature, and broadband emissivity were developed. A one-dimensional spectral intensity model that allowed for specular reflection, and investigated differences between measured and modeled spectral intensities was created. It was concluded that excellent agreement (within 2.5%) was achieved between optical and suction pyrometer gas temperatures as long as 1) the optical probe and cold target used were well-aligned 2) the path length was greater than 0.3 m and 3) the intensity from broadband emitters within the path was smaller than the gas intensity. Shorter path lengths between 0.15 – 0.3 m produced reasonable temperatures with 7 % error while path lengths of 0.05 m or less were as much as 15% in error or the signal would not effectively process. Water vapor concentration was less accurate being at best within 20% (relative) of expected values. The accurate determination of concentration requires first an accurate temperature concentration as well low broadband participation. Some optical concentrations were in error as much as 85%. The 1-D model was compared to the measurement and it was found that the model peaks were sharper and shifted 0.167 cm-1 compared to the measured data. The reason for the shift can be attributed to the uncertainty of the reference laser frequency used in the FTIR. No conclusion was found for the cause of the sharper peaks in the model. The integrated area of bands used to find temperature and concentration matched well between the model and measured spectrum being typically within 3%.

Lorsque l'on focalise une impulsion laser courte et intense dans un gazsous-dense, celle-ci peut accélérer une fraction des électrons du gaz,et ainsi générer un faisceau d'électrons ayant une énergie de quelquescentaines de MeV. Ce phénomène, connu sous le nom d'accélérationlaser-plasma, pourrait avoir de nombreuses applications,notamment pour la réalisation de sources de rayons Xultra-intenses appelées lasers à électrons libres (LEL). Cependant,ces applications nécessitent que le faisceau d'électrons ait uneexcellente qualité (faible divergence, faible émittance et faible dispersion en énergie). Au cours de cette thèse, différentes solutions ont été développéesafin d'améliorer la qualité des faisceaux d'électrons issus del'accélération laser-plasma. Ce travail est effectué à travers desmodèles analytiques ainsi que dessimulations Particle-In-Cell (PIC). Nous commençons cependant par montrer que les simulations PIC onttendance à surestimer l'émittance du faisceau, en raison de l'effetCherenkov numérique. Afin d'estimer correctement l'émittance ici, nousproposons un algorithme PIC modifié qui n'est pas sujet à l'effetCherenkov numérique. A l'aide de cet algorithme, un nouveau mécanisme permettant de générerle faisceau est observé puis étudié : il s'agit de l'injection optique transverse. Les faisceaux produits par ce mécanisme sontcaractérisés par une forte charge, une faible divergence et une faibleémittance. Par ailleurs, nous proposons un dispositif - la lentille laser-plasma - qui permet defortement réduire la divergence finale des faisceaux. Cesrésultats sont placés dans leur contexte, à travers une discussion despropriétés nécessaires pour un laser à électrons libres compact. Nousmontrons en particulier que les accélérateurs laser-plasma pourraientêtre avantageusement combinés avec des onduleurs laser-plasmainnovants, afin de produire des sources de rayons X intenses<br>When an intense and short laser pulse propagates through an underdensegas, it can accelerate a fraction of the electrons of the gas, andthereby generate an electron bunch with an energy of a few hundreds ofMeV. This phenomenon, which is referred to as laser-wakefield acceleration, has many potential applications, including the design of ultra-bright X-ray sources known as freeelectron lasers (FEL). However, these applications require the electronbunch to have an excellent quality (low divergence, emittance andenergy spread). In this thesis, different solutions to improve thequality of the electron bunch are developed, both analytically and through the use of Particle-In-Cell (PIC) simulations. It is first shown however that PIC simulations tend to erroneously overestimate the emittance of the bunch, due to the numerical Cherenkov effect. Thus, in order to correctly estimate the emittance, a modified PICalgorithm is proposed, which is not subject to this unphysical Cherenkov effect. Using this algorithm, we observed and studied a new mechanism togenerate the electron bunch: optical transverse injection. This mechanism can produce bunches with ahigh charge, a low emittance and a low energy spread. In addition, wealso proposed an experimental setup - the laser-plasma lens- which can strongly reduce the final divergence of the bunch. Finally, these results are put into context by discussing the propertiesrequired for the design of a compact FEL. It is shown in particularthat laser-wakefield accelerator could be advantageously combinedwith innovative laser-plasma undulators, in order to produce brightX-rays sources

In meiner Doktorarbeit untersuche ich ein Kac-artiges Vielteilchen-Modell, das eine Beschreibung von plastischen Verformungen ohne Verwendung einer Referenz-Konfiguration ermöglicht. Im Rahmen des Modells wird die Verformung eines Körpers durch Angabe von Atompositionen beschrieben. Es wird eine Mesoskala zwischen der Mikroskala der Atom-Atom Abstände und der Makroskala des Körpers eingeführt. Um jeden Punkt wird die Konfiguration auf dieser Mesoscala mit einem Bravais-Gitters approximiert. Die Matrix, die dieses Gitter aufspannt, wird als Argument eines elastischen Energiefunktionals verwendet. Auf diese Weise wird ein Energiefunktional definiert, das die Eigenschaften des Systems festlegt. Im Ersten Teil meiner Doktorarbeit analysiere ich das Modell im Fall das eine Referenz-Konfiguration lokal existiert. Ich schätze die Energiedichte einer solchen Konfiguration mit einer Störungsrechung von oben ab und erhalte eine obere Schranke für die Energiebarriere für plastische Relaxation in zwei Dimensionen. Im zweiten Teil untersuche ich Möglichkeiten Lagrange-Koordinaten im Rahmen des Modells zu konstruieren. Ich beweise, dass für zwei Punkte deren Abstand klein genug sind und die bestimmte Regularitätseigenschaften erfüllen, die Gitterparameter der approximierenden Bravais-Gitter bis auf eine Reparametrisierung nahe beieinander liegen müssen. Dies erlaubt diskrete Ketten von regulären Punkten zur Definition von Homotopieklassen zu benutzen die mit verallgemeinerten Burgers-Vektoren charakterisiert werden. Es ist mit dieser Technik auch möglich die Kernenergie von Versetzungen nach unten abzuschätzen. Schließlich passe ich eine Methode kontinuierliche Lagrange-Koordinaten, die von L. Mugnai und S. Luckhaus entwickelt wurden, an das Model an und verbessere sie dergestalt, dass ich die Energiedichte mit Hilfe eines Funktionales der Lagrange-Koordinaten nach unten abschätzen kann<br>I study a Kac-type many particle model that allows a reference-free description of plastic deformation.In the framework of the model the state of the body is given by a set of atom position. The typical atom-atom distance is the microscopic scale. The size of the body is the macroscopic scale. Around each point a lattice is fitted to the configuration on a mesoscopic scale. The lattice parameters are used as an argument of a non-linear elasticity energy functional. Hence, this procedure allows to define an free-energy functional of a particle configuration. In the first part of my thesis I analyze the model in the case that a reference configuration exists locally. I bound the energy-density of such a configuration from above with a pertubative calculation and obtain an upper bound for the energy barrier of plastic deformation for dimension two. In the second part I explore the possibility to construct Lagrangian coordinates in the framework of the model. I prove that for two points that are close to each other and that fulfill certain regularity assumptions the fitted lattice parameters are close to each other up to a reparametrisation. This allows to use discrete chains of regular points for homotopy type arguments and define a generalized Burgers vector as a topological quantity. I also use this method to get a lower bound for the core energy of a dislocation. Finally, I adapt a method to construct continuous Lagrangian coordinates presented in by L.Mugnai and S.Luckhaus to my model and improve it to a point where I can use a functional of these Lagrangian coordinate as a lower bound for the energy of the model

In this study, a computational model which couples particle method for fluid part and modal superposition for structure part is developed to investigate the Fluid Structure Interaction problems with free surface. As a Lagrangian mesh-free method, the MPS (Moving Particle Semi-implicit) method is very suitable for simulating violent flows such as breaking waves on free surface. However, despite its wide range of applicability, the original MPS algorithm suffers from some inherent difficulties in obtaining an accurate fluid pressure in both spatial and time domain. Different modifications to improve the method have been proposed in the literature. In this study, the following modifications are proposed to improve the accuracy of pressure calculations and the stability of the method: i) A density error compensation source term in the pressure Poisson equation with no artificial term in the formulation, ii) New solid and free surface boundary handling methods, iii) Particle position shifting and collision handling, and iv) A new version of “cell-link” neighbour particle searching strategy, which reduces about 6.5/9 ( 72%) of the searching area compared with traditional “cell-link” algorithm. For problems where violent free surface deformation only occur in a constrained area, the efficiency of MPS is further improved by weakly coupling with BEM (Boundary Element Method). For the structure that undergoes very large rigid motions and relatively small elastic deformation, an efficient computational model that couples the rigid-body and flexible modes in the same set of formulation. Unlike the traditional modal analysis, this model takes into account the mutual effect between rigid-body motion and flexible deformation. It is more efficient compared with FE(Finite Element) method, regardless of the size of the structure. For 2D cases,if only the first three modes are chosen to represent the flexible deformation of the structure, it only results in a 6 x 6 equation system to be solved. For the fluid structure interaction coupling, the Gauss-Seidel iteration with Aitken relaxation scheme is used. The effectiveness of the proposed modifications for MPS method is validated by a 2D Dam-break flow. Furthermore, various typical impact flow problems in marine engineering are simulated to test the applicability of the modified MPS method. It includes 2D/3D Dam-break with different boundary conditions (such as obstacle in the middle of the tank, spring supported rigidwall and flexible cantilever beam), liquid sloshing, wedge-shape and ship-section-shape dropping problems. The weak coupling scheme between MPS and BEM are also tested by the 2D breaking solitary wave impacting a flexible wall problem. The coupling of fluid and structure solver is also tested by various problems including 2D flexible wedge dropping and 2D/3D floating beam/ship slamming problems. The numerical results obtained are found to be in good agreement with the available numerical or experimental results. With the proposed modifications, the stability and accuracy of the pressure field are improved in spatial and time domains. The proposed structure model also proves to be effective.

Polymer chain microstructure, including characteristics such as molecular weight and branch length, can impact the end-use properties of the polymer. The assumptions contained in deterministic models prevent examination of the structure of individual polymer chains, so removal of these assumptions is necessary to gain insight into molecular-level mechanisms that determine chain microstructure. The work presented here uses a combination of stochastic and deterministic models to examine two significant mechanistic issues in free radical polymerization. The zero-one assumption concerning the number of radicals is often made for miniemulsion polymerization using oil-soluble initiators because of accelerated termination due to radical confinement. Although most of the initiator is present inside the particles, opposing viewpoints exist as to whether the locus of radical generation is the particle phase or the aqueous phase. A well-mixed kinetic Monte Carlo (KMC) model is used to simulate the molecular weight distribution and the results are compared to estimated molecular weights for several chain-stopping events, with the finding that the dominant nucleation mechanism varies with reaction temperature and particle size. Intramolecular chain transfer to polymer, or backbiting, is often assumed to produce only short-chain branches. Using a lattice KMC model, a cumulative distribution function (CDF) is obtained for branch lengths produced by backbiting. Implementation of the CDF in both a rate-equation model and the well-mixed KMC model shows that, for the butyl acrylate solution polymerization system used for comparison, backbiting is responsible for most of the branches, including long-chain branches, even though overlap of the polymer coils in the solution is predicted, a condition which would normally be expected to lead to significant intermolecular chain transfer to polymer. The well-mixed KMC model provides a more thorough analysis of chain microstructure while the rate-equation model is more computationally efficient.

The paper describes the microstructure and mechanical properties of ceramic material based on silicon nitride obtained by cold isostatic pressing and sintering in a nitrogen atmosphere. Microhardness and flexural strength are examined. The work is aimed to show that obtained material has moderately high strength, good physical characteristics and submicron structure.

Ni/NiO nanopowders have been prepared by using thermal decomposition of aqua solutions of nickel acetate ammine complexes in air at the annealing temperature range 300 – 500 ºC, time of decomposition from 30 to 180 min. Particle size of powders has been investigated by and scanning electron microscopy (SEM). Powders pore structure has been determinated by low temperature nitrogen adsorption method. Content of free carbon in powders is determitated by stage of decomposition and annealing temperature. Decomposition of hydroxy-containing precursor at occurred in 3 stages: 1) the primary formation of Ni; 2) decomposition of precursors with formation of NiO; 3) afterreduction of NiO to Ni by residuals of organic compounds and ammonia. The first two stages is characterized by highly endothermic effect that can lead to decreasing of acetic acid evaporation rate and resulted in high free carbon content of powders. Increasing of deposition time permits to remove of acetic acid from particle surface and decrease free carbon content in powder.

Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy. The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design. These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.

Studying the interactions of solid particles and deformable gas<br />bubbles in viscous liquids is very important in many applications,<br />especially in mining and chemical industries. These interactions<br />involve liquid-solid-air multiphase flows and an<br />arbitrary-Lagrangian-Eulerican (ALE) approach is used for the direct<br />numerical simulations. In the system of rigid particles and<br />deformable gas bubbles suspended in viscous liquids, the<br />Navier-Stokes equations coupled with the equations of motion of the<br />particles and deformable bubbles are solved in a finite-element<br />framework. A moving, unstructured, triangular mesh tracks the<br />deformation of the bubble and free surface with adaptive refinement.<br />In this dissertation, we study four problems. In the first three<br />problems the flow is assumed to be axisymmetric and two dimensional<br />(2D) in the fourth problem.<br /><br />Firstly, we study the interaction between a rising deformable bubble<br />and a solid wall in highly viscous liquids. The mechanism of the<br />bubble deformation as it interacts with the wall is described in<br />terms of two nondimensional groups, namely the Morton number (Mo)<br />and Bond number (Bo). The film drainage process is also<br />considered. It is found that three modes of bubble-rigid wall<br />interaction exist as Bo changes at a moderate Mo.<br />The first mode prevails at small Bo where the bubble deformation<br />is small. For this mode, the bubble is<br /> hard to break up and will bounce back and eventually attach<br />to the rigid wall. In the second mode, the bubble may break up after<br />it collides with the rigid wall, which is determined by the film<br />drainage. In the third mode, which prevails at high Bo, the bubble<br />breaks up due to the bottom surface catches up the top surface<br />during the interaction.<br /><br />Secondly, we simulate the interaction between a rigid particle and a<br />free surface. In order to isolate the effects of viscous drag and<br />particle inertia, the gravitational force is neglected and the<br />particle gains its impact velocity by an external accelerating<br />force. The process of a rigid particle impacting a free surface and<br />then rebounding is simulated. Simplified theoretical models are<br />provided to illustrate the relationship between the particle<br />velocity and the time variation of film thickness between the<br />particle and free surface. Two film thicknesses are defined. The<br />first is the thickness achieved when the particle reaches its<br />highest position. The second is the thickness when the particle<br />falls to its lowest position. The smaller of these two thicknesses<br />is termed the minimum film thickness and its variation with the<br />impact velocity has been determined. We find that the interactions<br />between the free surface and rigid particle can be divided into<br />three regimes according to the trend of the first film thickness.<br />The three regimes are viscous regime, inertial regime and jetting<br />regime. In viscous regime, the first film thickness decreases as the<br />impact velocity increases. Then it rises slightly in the inertial<br />regime because the effect of liquid inertia becomes larger as the<br />impact velocity increases. Finally, the film thickness decreases<br />again due to Plateau-Rayleigh instability in the jetting regime.<br />We also find that the minimum film thickness corresponds to an<br />impact velocity on the demarcation point between the viscous and<br />inertial regimes. This fact is caused by the balance of viscous<br />drag, surface deformation and liquid inertia.<br /><br />Thirdly, we consider the interaction between a rigid particle and a<br />deformable bubble. Two typical cases are simulated: (1) Collision of<br />a rigid particle with a gas bubble in water in the absence of<br />gravity, and (2) Collision of a buoyancy-driven rising bubble with a<br />falling particle in highly viscous liquids. We also compare our<br />simulation results with available experimental data. Good agreement<br />is obtained for the force on the particle and the shape of the<br />bubble.<br /><br />Finally, we investigated the collisions of groups of bubbles and<br />particles in two dimensions. A preliminary example of the oblique<br />collision between a single particle and a single bubble is conducted<br />by giving the particle a constant acceleration. Then, to investigate<br />the possibility of particles attaching to bubbles, the interactions<br />between a group of 22 particles and rising bubbles are studied. Due<br />to the fluid motion, the particles involved in central collisions<br />with bubbles have higher possibilities to attach to the bubble.<br>Ph. D.

Blood flow through microcirculation in both simple and complex geometry has been difficult to predict due to the composition and complex behavior of blood at the microscale. Blood is a dense suspension of deformable red blood cells that is comparable in dimensions to the microchannels that it flows through. As a result, rheological properties at the microscale can vastly differ from bulk rheological properties due to non-continuum effects. To further develop our understanding of blood microflow; experimental techniques should be explored. In this work, we explore micro-particle image velocimetry (μPIV) and two-beam fluorescence cross-correlation spectroscopy (2bFCCS) in the application of characterizing blood in microflow conditions. For the development of the μPIV analysis, a polydimethylsiloxane co-flow channel is used to observe blood flow in controlled conditions. Flow conditions (velocity profile and blood layer thickness) are selected based on an analytical model and compared to experimental measurement. The experimental results presented indicate that current flow conditions are inadequate in providing a controlled rate of shear on the blood layer in the co-flow channel and further optimization are required to improve the measurement of the velocity profile. For the development of the 2bFCCS application for blood flow analysis, a wide glass capillary microfluidic device is used to complete the verification of fluorescence fluid admissibility, the effect of laser intensity on inducing photobleaching and the velocity measurement performance. The experimental measurement of the velocity profile is validated against the theoretical profile for a rectangular channel. Results of the velocity profile of high concentration red blood cells show promise in the technique’s ability to measure blood microflows closer to physiological conditions.

Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy. The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design. These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.

Understanding turbulent flow structure in open channel flows is an important issue for Civil Engineers who study the transport of water, sediments and contaminants in rivers. In the present study, turbulent flows over rough impermeable and porous beds are studied numerically using the Smoothed Particle Hydrodynamics (SPH) method. A comprehensive review is carried out on the methods of turbulence modelling and treatment of bed boundary in open channel flows in order to identify the limitations of the existing particle models developed in this area. 2D macroscopic SPH models are developed for simulating turbulent free surface flows over rough impermeable and porous beds under various flow conditions. For the case of impermeable beds, a drag force model is proposed to take the effect of bed roughness into account, while for the case of porous beds, macroscopic governing equations are developed based on the SPH formulation, incorporating the effects of drag and porosity. To simulate the effect of turbulence on the average flow field, a Macroscopic SPH-mixing-length (MSPH-ML) model is proposed based on the Large Eddy Simulation (LES) concept where the mixing-length approach is applied to estimate the eddy-viscosity rather than employing the standard Smagorinsky model. The difficulty in reproducing steady uniform free surface flow is tackled by introducing novel inflow/outflow techniques for the situations in which the flow quantities are unknown at the inflow and outflow boundaries. The performance of these models is tested by simulating different engineering problems with an insight developed into turbulence modelling and bed/interface boundary treatment. The accuracy of the models is tested by comparing the predicted quantities such as flow velocity, water surface elevation, and turbulent shear stress with existing experimental data. The limitations of the models are mainly attributed to the macroscopic representation of the roughness layer and porous bed, difficulty in the determination of the values of the empirical coefficients in the closure terms, and limitations with the use of fine computational resolution. On the other hand, the main strength of the model is describing the complicated processes occuring at the bed using simple and practical computational treatments so that the momentum transfer is estimated accurately. It is shown that if the closure terms in the momentum equation which represent the effect of bed drag and flow turbulence are determined carefully based on the physical conditions of bed and flow, the model is capable of being employed for different civil engineering applications.

Tsunamis are among the most terrifying and complex physical phenomena potentially affecting almost all coastal regions of the Earth. Tsunami waves propagate in the ocean over thousands of kilometres away from their generating source at considerable speeds. Among several other tsunamis that occurred during the past decade, the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami in Japan, considered to be the deadliest and costliest natural disasters in the history of mankind, respectively, have hit wide stretches of densely populated coastal areas. During these major events, severe destruction of inland structures resulted from the action of extreme hydrodynamic forces induced by tsunami flooding. Subsequent field surveys in which researchers from the University of Ottawa participated ultimately revealed that, in contrast to seismic forces, such hydrodynamic forces are not taken into proper consideration when designing buildings for tsunami prone areas. In view of these limitations, a novel interdisciplinary hydraulic-structural engineering research program was initiated at the University of Ottawa, in cooperation with the Canadian Hydraulic Centre of the National Research Council, to help develop guidelines for the sound design of nearshore structures located in such areas. The present study aims to simulate the physical laboratory experiments performed within the aforementioned research program using a single-phase three-dimensional weakly compressible Smoothed Particle Hydrodynamics (SPH) numerical model. These experiments consist in the violent impact of rapidly advancing tsunami-like hydraulic bores with individual slender structural elements. Such bores are emulated based on the classic dam-break problem. The quantitatively compared measurements include the time-history of the net base horizontal force and of the pressure distribution acting on columns of square and circular cross-sections, as well as flow characteristics such as bore-front velocity and water surface elevation. Good agreement was obtained. Results show that the magnitude and duration of the impulsive force at initial bore impact depend on the degree of entrapped air in the bore-front. The latter was found to increase considerably if the bed of the experimental flume is covered with a thin water layer of even just a few millimetres. In order to avoid large fluctuations in the pressure field and to obtain accurate simulations of the hydrodynamic forces, a Riemann solver-based formulation of the SPH method is utilized. However, this formulation induces excessive numerical diffusion, as sudden and large water surface deformations, such as splashing at initial bore impact, are less accurately reproduced. To investigate this particular issue, the small-scale physical experiment of Kleefsman et al. (2005) is also considered and modeled. Lastly, taking full advantage of the validated numerical model to better understand the underlying flow dynamics, the influence of the experimental test geometry and of the bed condition (i.e. dry vs. wet) is investigated. Numerical results show that when a bore propagates over a wet bed, its front is both deeper and steeper and it also has a lower velocity compared to when it propagates over a dry bed. These differences significantly affect the pressure distributions and resulting hydrodynamic forces acting on impacted structures.

Film flow of a suspension has been investigated both experimentally and theoretically. Gravity-driven free-surface inclined plane flow of a suspension of neutrally buoyant particles has been investigated using a stereoscopic particle imaging velocimetry technique. Particles have been shown to migrate away from the solid surface, and the film thickness has been shown to decrease as the fluid moves down the inclined plane. The free surface has been characterized using a light reflection technique, which shows that surface topography is affected by the inclination angle, and the particle concentration. This flow has been modeled based on a suspension normal stress approach. A boundary condition at the free surface has been examined, and model predictions have been compared with experimental results. The model predicts that the film thickness, relative to its initial value, will decrease with the bulk particle concentration. The thin film flow over the inner cylinder in partially filled Couette flow of a suspension has been experimentally investigated as well as modeled. Concentration bands have been shown to form under a variety of different fill fractions, bulk particle concentrations, inclination angles, ratio of inner to outer cylinder, and rotation rates of the inner cylinder. The banding phenomena ranges from a regime where bands are small, mobile and relatively similar in concentration to the bulk, to a regime where the concentration bands are larger, stationary, and where the space between them is completely devoid of particles. The role of the film thickness in the band formation process has been investigated, and has led to a model for the band formation process based on a difference in the rate that fluid can drain from height fluctuations relative to the particles.

Estimating human motion is the topic of this thesis. We are interested in accurately estimating the motion of a human body using only video images capturing the subject in motion. Video images from up to two cameras are considered. The first main topic of the thesis is to investigate a new type of input data. This data consists of some sort of texture. This texture can be added to the human body segment under study or it can be the actual texture of the skin. In paper I we investigate if added texture together with the use of a two camera system can provide enough information to make it possible to estimate the knee joint center location. Evaluation is made using a marker based system that is run in parallel to the two camera video system. The results from this investigation show promise for the use of texture. The marker and texture based estimates differ in absolute values but the variations are similar indicating that texture is in fact usable for this purpose. In paper II and III we investigate further the usability in images of skin texture as input for motion estimation. Paper II approaches the problem of estimating human limb motion in the image plane. An image histogram based mutual information criterion is used to decide if an extracted image patch from frame k is a good match to some location in frame k+1. Eval- uation is again performed using a marker based system synchronized to the video stream. The results are very promising for the application of skin texture based motion estimation in 2D. In paper III, basically the same approach is taken as in paper II with the substantial difference that here estimation of three dimensional motion is addressed. Two video cameras are used and the image patch matching is performed both between cameras (inter-camera) in frame k and also in each cameras images (intra-camera) for frame k to k+1. The inter-camera matches yield triangulated three dimensional estimates on the approximate surface of the skin. The intra-camera matches provide a way to connect the three dimensional points between frame k and k+1 The resulting one step three dimensional trajectories are then used to estimate rigid body motion using least squares methods. The results show that there is still some work to be done before this texture based method can be an alternative to the marker based methods. In paper IV the second main topic of the thesis is discussed. Here we present an investigation in using model based techniques for the purpose of estimating human motion. A kinematic model of the thigh and shank segments are built with an anatomic model of the knee. Using this model, the popular particle filter and typical simulated data from the triangulation in paper III, an estimate of the motion variables in the thigh and shank segment can be achieved. This also includes one static model parameter used to describe the knee model. The results from this investigation show good promise for the use of triangulated skin texture as input to such a model based approach.

This thesis deals with different approaches to filtering the signal output of a three axis accelerometerfor free space orientation, that is, finding the orientation of a sensor relative to gravity. Theplatform this orientation system is to be developed for is a low-power, high-efficiency fixed-pointmath microprocessor, therefore efficiency and mathematical operation precision are factors thatalso need to be taken into consideration in this work.This is an exploratory work which goals are to analize potential filtering solutions for free spaceorientation with a three-axis accelerometer, develop a tool to validate the theorical analysis, studythe repercusions of limited precision math on those algorithms and implement a filtering solutionas versatile as possible.The goal of finding the orientation with the output of an accelerometer and without a prioriinformation is deceptively simple: while in relaxed state and within inertial systems the outputof a three axis accelerometer and the direction of gravity is the same, when that hypothesis istaken away measurements output by the accelerometer include both gravity and acceleration dueto external forces applied to the system.The contributions of this thesis are a discussion of potential solutions for free space orientationwith unrestrictive preconditions by use of an accelerometer, and an implementation of such solutionfor the MSP430, popular platform of choice for digital signal processing. The main purposeof such a solution is to improve the precision with which gravity is estimated from the outputof the accelerometer. Potential applications of this work are relative position tracking, mapping,positioning systems (for example, within buildings or vehicles, where any other existing positioningsystem cannot work, such as tunnels for GPS).Instead of just low-pass filtering the output of the accelerometer, estimations to the state ofexternal forces applied to the system and tracking of changes to those forces are presented. Tomodel that system, the Kalman filter and the Particle filter are introduced and analyzed as potentialsolutions.This document includes a discussion of both Kalman and Particle filters, implementation ofa tool to compare and validate the models to estimate gravity, a discussion of the effect of fixedpoint math to those models and an implementation of a gravity estimation algorithm that is typeand plattform agnosic based on the output of a 3-axis accelerometer.All relevant code has been included as an appendix to this work This thesis deals with di_erent approaches to _ltering the signal output of a three axis accelerometer for free space orientation, that is, _nding the orientation of a sensor relative to gravity. The plattform this orientation system is to be developed for is a low-power, high-e_ciency _xed-point math microprocessor, therefore e_ciency and mathematical operation precision are factors that also need to be taken into consideration in this work. This is an exploratory work which goals are to analize potential _ltering solutions for free space orientation with a three-axis accelerometer, develop a tool to validate the theorical analysis, study the repercusions of limited precision math on those algorithms and implement a _ltering solution as versatile as possible. The goal of _nding the orientation with the output of an accelerometer and without a priori information is deceptively simple: while in relaxed state and within inertial systems the output of a three axis accelerometer and the direction of gravity is the same, when that hypothesis is taken away measurements output by the accelerometer include both gravity and acceleration due to external forces applied to the system. The contributions of this thesis are a discussion of potential solutions for free space orientation with unrestrictive preconditions by use of an accelerometer, and an implementation of such solution for the MSP430, popular platform of choice for digital signal processing. The main purpose of such a solution is to improve the precision with which gravity is estimated from the output of the accelerometer. Potential applications of this work are relative position tracking, mapping, positioning systems (for example, within buildings or vehicles, where any other existing positioning system cannot work, such as tunnels for GPS). Instead of just low-pass _ltering the output of the accelerometer, estimations to the state of external forces applied to the system and tracking of changes to those forces are presented. To model that system, the Kalman _lter and the Particle _lter are introduced and analyzed as potential solutions. This document includes a discussion of both Kalman and Particle _lters, implementation of a tool to compare and validate the models to estimate gravity, a discussion of the e_ect of _xed point math to those models and an implementation of a gravity estimation algorithm that is type and plattform agnosic based on the output of a 3-axis accelerometer. All relevant code has been included as an appendix to this work.<br>Denna avhandling beskriver olika metoder för filtrering av utsignalen från en tre-axlig accelerationsmätare för orientering i ledigt utrymme, det vill säga att finna en sensors orientering iförhållande till tyngdkraften. Den plattform detta orienteringssystem ska utvecklas för är en högeffektivmikro-processor med fixed-point matematik, därför är även matematisk operationsprecisionoch efiektivitet faktorer som måste beaktas i detta arbete.Detta är ett förberedande arbete där målet är att analysera möjliga filtreringslösningar för friutrymmesorientering med en tre-axlig accelerationsmätare, utveckla ett verktyg för att validerateoretisk analys, studera konsekvenserna av att använda begränsad precisionsmatematik både algoritmernaoch implementera en filtreringslösning för mikroprocessorerna.Målet med att finna orienteringen med hjälp av utsignalen från en accelerationsmätare ochutan a priori-information är bedrägligt enkel: I avslappnat tillstånd och inom interna system ärutgången hos en tre-axlig accelerationsmätare och tyngdkraftens riktning densamma, när den hypotesenär borttagen visar mätningar att utgång av accelerometern inkluderar både gravitationoch acceleration pågrund av yttre påfrestningarna påsystemet.Bidragen från denna uppsats är en diskussion om möjliga lösningar för orientering i frittutrymme med orestriktiva förutsättningar genom användning av en accelerationsmätare, och ettgenomförande av en sådan lösning för fixed-point matematik mikrokontrollerna. Det huvudsakligasyftet med en sådan läsning är att förbättra den precision med vilken gravitation uppskattas frånutsignalen från en accelerationsmätare. Potentiella tillämpningar av detta arbete är relativ positionsspårning, kartläggning, positioneringssystem (till exempel inom byggnader eller fordon, därandra befintliga positioneringssystem inte kan arbeta, till exempel tunnlar för GPS).Istället för att bara lågpass-filtrera utsignalen från en accelerationsmätare appliceras uppskattningartill stadiet av yttre krafter påsystemet och spårning av ändringar i dessa krafter presenteras.För att modellera systemet introduceras Kalman-filter och partikelfilter för att analyseras som potentiellalösningar.Det här dokumentet innehåller en diskussion om både Kalman och Partikelfilter, implementationav ett verktyg för att jämföra och validera modeller i syfte att uppskatta gravitationen,en diskussion om effekten av fixed-point matematik för dessa modeller och ett genomförande aven gravitationsuppskattningsalgoritm för mikrokontrollerna utifrån utgången hos en treaxlig accelerometer.Relevant kod finns som bilaga till detta arbete.. Denna avhandling beskriver olika metoder för filtrering av utsignalen från en tre-axlig accelerationsm ätare för orientering i ledigt utrymme, det vill säga att finna en sensors orientering i förhållande till tyngdkraften. Den plattform detta orienteringssystem ska utvecklas för är en högeffektiv mikro-processor med fixed-point matematik, därför är även matematisk operationsprecision och efiektivitet faktorer som måste beaktas i detta arbete. Detta är ett förberedande arbete där målet är att analysera möjliga filtreringslösningar för fri utrymmesorientering med en tre-axlig accelerationsmätare, utveckla ett verktyg för att validera teoretisk analys, studera konsekvenserna av att använda begränsad precisionsmatematik både algoritmerna och implementera en filtreringslösning för mikroprocessorerna. Målet med att finna orienteringen med hjälp av utsignalen från en accelerationsmätare och utan a priori-information är bedrägligt enkel: I avslappnat tillstånd och inom interna system är utgången hos en tre-axlig accelerationsmätare och tyngdkraftens riktning densamma, när den hypotesen är borttagen visar mätningar att utgång av accelerometern inkluderar både gravitation och acceleration pågrund av yttre påfrestningarna påsystemet. Bidragen från denna uppsats är en diskussion om möjliga lösningar för orientering i fritt utrymme med orestriktiva förutsättningar genom användning av en accelerationsmätare, och ett genomförande av en sådan lösning för fixed-point matematik mikrokontrollerna. Det huvudsakliga syftet med en sådan läsning är att förbättra den precision med vilken gravitation uppskattas från utsignalen från en accelerationsmätare. Potentiella tillämpningar av detta arbete är relativ positionssp årning, kartläggning, positioneringssystem (till exempel inom byggnader eller fordon, där andra befintliga positioneringssystem inte kan arbeta, till exempel tunnlar för GPS). Istället för att bara lågpass-filtrera utsignalen från en accelerationsmätare appliceras uppskattningar till stadiet av yttre krafter påsystemet och spårning av ändringar i dessa krafter presenteras. För att modellera systemet introduceras Kalman-filter och partikelfilter för att analyseras som potentiella lösningar. Det här dokumentet innehåller en diskussion om både Kalman och Partikelfilter, implementation av ett verktyg för att jämföra och validera modeller i syfte att uppskatta gravitationen, en diskussion om effekten av fixed-point matematik för dessa modeller och ett genomförande av en gravitationsuppskattningsalgoritm för mikrokontrollerna utifrån utgången hos en treaxlig accelerometer. Relevant kod finns som bilaga till detta arbete..<br>Este documento presenta y discute diferentes soluciones para filtrar la señal de salida de un acelerómetro triaxial con el objetivo de conocer su orientación en el espacio libre, es decir, estimar la orientacifion del senson en relación con la gravedad. La plataforma sobre la cual estos algoritmos han de ser desplegados es un microcontrolador de bajo consumo y alta eficiencia, TI MSP430, por ello, la eficiencia y la precisión de las operaciones matemáticas en los diferentes algoritmos son también tratadas en este documento. Éste es un trabajo de exploración cuyos objectivos son el análisis de soluciones para el filtrado de la señal de un acelerómetro triaxial, el desarrollo de una herramienta para la validación del análisis teórico, el estudio de la repercusión sobre los algoritmos de filtrado de la limitada precisión en las operaciones matemáticas, y la implementación de una solución de filtrado para el microcontrolador MSP430 de Texas Instruments. Encontrar la orientación de un sensor con la señal de salida de un acelerómetro es un abjetivo relativamente complejo: mientras el sensor están estacionario, la señal de salida es la orientación, pero cuando fuerzas externas son aplicadas sobre el sensor, estas fuerzas contribuyen como ruido al problema que se presenta. Las contribuciones de este documento son una discusión sobre potenciales soluciones para el filtrado de la señal de un acelerómetro triaxial para la orientación en el espacio libre, y una implementación de una solución para el microcontrolador MSP430, plataforma popular para el proceso digital de señales. La principal misión de esta implementación es la mejora de la precisión con la que se estima la dirección de la gravedad mediante el uso de un acelerómetro triaxial. Aplicaciones potenciales están relacionadas con seguimiento de posición, mapeado, sistemas de posicionamiento (por ejemplo, dentro de vehiculos o edificios donde otros sistemas no funcionarían, como por ejemplo GPS en un túnel). En lugar de un simple filtro paso bajo para eliminar el ruido introducido por fuerzas externas, estimaciones del estado de las fuerzas externas y filtros para el seguimiento de las mismas son presentados en este documento. Para modelar dicho sistema, se introcucen el filtro de Kalman y el filtro de Partículas, y ambos se analizan como soluciones para este problema. Este documento incluye una discusión de ambos tros, la implementacion de una herramienta de validación para los mismos, anfialisis del efecto de la introducción de álgebra de punto fijo sobre los modelos, y una implementacion del sistema para el MSP430 de Texas Instruments. El código relevante de este trabajo se incluye como apéndice a este trabajo.

River ice jams can cause many problems including extreme flooding, damage to structures, interference with navigation, and restrictions on hydropower operations. Their annual cost to the Canadian economy has been estimated to be nearly one hundred million dollars. This thesis explores the application of smoothed particle hydrodynamics (SPH) to river ice flows. SPH is a meshless method used to solve fluid dynamics problems, whereby the fluid is replaced by a set of particles that move with the flow. This method is particularly well suited to modelling complex free-surfaces and moving solid boundaries. The main contributions of this study were the new developments made to an existing SPH code enabling the accurate simulation of freely moving solid objects in a free-surface flow subject to hydrodynamic and solid contact forces. An SPH Arbitrary Lagrangian-Eulerian (ALE) formalism was used to model the fluid flow and the hydrodynamic forces exerted on solid objects. This study involved coupling the existing SPH-ALE model with the discrete element method (DEM) used to model solid interactions with other solids and with boundaries. The solid interactions were implemented as both a hard-sphere model based on instantaneous, inelastic collisions, and a soft-sphere linear spring and dashpot model based on force-displacement relationships. Application and validation test cases of freely moving solid objects were simulated and compared with analytical solutions, laboratory experiments, and other computational results. These new capabilities were then applied to river ice dynamics problems. The methods used in this study are suited to smaller scale river ice processes where the dynamic effects may not be captured with traditional depth-averaged modelling techniques. Computational results showing the stability of a floating ice block approaching a stationary cover and ice accumulation upstream of an obstruction are encouraging and they show promise to serve as a useful quantitative engineering tool in the future.<br>Les embâcles de glace peuvent causer de nombreux problèmes, y compris des inondations, des dommages aux structures, interférence avec la navigation et des restrictions sur les opérations hydroélectriques. Leur coût annuel pour l'économie canadienne est estimé à presque 100 millions de dollars. Cette thèse étude l'application de la méthode de simulation numérique, smoothed particle hydrodynamics (SPH) pour les problèmes de glace en rivière. SPH est une méthode utilisée pour résoudre les problèmes de dynamique des fluides, dans laquelle le liquide est modélisé par un ensemble de particules. Cette méthode est particulièrement bien adaptée pour modéliser les écoulements à surfaces libres. Les principales contributions de cette étude sont les nouveaux développements apportés à un code SPH existant, permettant la simulation d'objets solides qui sont emportés avec l'écoulement à surface libre. Un formalisme SPH Arbitrary Lagrangian-Eulerian (ALE) a été utilisé pour modéliser l'écoulement du fluide et les forces hydrodynamiques sur les objets solides. Cette étude porte sur le couplage du modèle existant SPH-ALE avec la discrete element method (DEM) utilisée pour modéliser les interactions solides entre eux et avec des parois. Les interactions solides ont été implémentées comme un modèle de hard-sphere, basé sur les collisions inélastiques instantanées, ainsi qu'un modèle soft-sphere basé sur les relations entre les forces et les déplacements. Des cas-test de validation et application ont été simulés et évalués pour vérification avec des solutions analytiques, des expériences de laboratoire, et d'autres résultats de calcul. Ces nouvelles fonctionnalités ont ensuite été appliquées aux problèmes dynamiques de glace en rivière. Les résultats numériques montrent la stabilité d'un bloc de glace flottant qui s'approche un bloc fixe et l'accumulation de glace en amont d'une obstruction. Ces résultats prometteurs permettent de valider cette technique pour l'évaluation quantitative future en ingénierie.

Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1&micro;M in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide nanoparticles reduced the cellular damages to the normal breast epithelial cell line (CRL 8798) induced by X-rays and to the Keratinocyte cell line induced by UV irradiation. Cerium oxide nanoparticles were also found to be neuroprotective to adult rat spinal cord and retinal neurons. We propose that cerium oxide nanoparticles act as free radical scavenger (via redox reactions on its surface) to decrease the ROS induced cellular damages. Additionally, UV-visible spectroscopic studies indicated that cerium oxide nanoparticles possess auto-regenerative property by switching its oxidation state between Ce3+ and Ce4+. The auto-regenerative antioxidant property of these nanoparticles appears to be a key component in all the biological applications discussed in the present study.<br>Ph.D.<br>Department of Mechanical, Materials and Aerospace Engineering;<br>Engineering and Computer Science<br>Materials Science and Engineering

Der Betrieb eines Freien Elektronen Lasers (FEL), bei dem die spontan emittierte Undulatorstrahlung ueber Wechselwirkung mit dem Elektronenstrahl selbst verstaerkt wird, setzt eine praezise Ausrichtung des Elektronenstrahls mit dem Photonenstrahl voraus. Um den Ueberlapp von Elektronen-und Photonenstrahl zu gewaehrleisten, wurde ein neuartiger Typ von Wellenleiter-Strahllagemonitor entwickelt, der in eine Vakuumkammer des Undulators des FELs der TESLA Test Facility (TTF) integriert ist. Vier um das Strahlrohr verteilte Wellenleiter koppeln ueber schmale Schlitze einen Bruchteil jenes elektromagnetischen Feldes aus, welches den Strahl begleitet. Die induzierten Signale haengen von der transversalen Strahlposition und der Strahlintensitaet ab. Mit vier Schlitz-Wellenleiter Paaren laesst sich ein lineares Signal ableiten, anhand dessen die Position des Elektronenstrahls bestimmt werden kann. Die induzierten Signale werden mittels eines stegbelasteten Wellenleiters in die erste Stufe eines bei 12 GHz arbeitenden Empfaengers zugefuehrt. Die vorliegende Arbeit beschreibt Design, Tests und Implementierung dieses neuartigen Typs von Strahllagemonitor.<br>The operation of a free electron laser working in the Self Amplified Spontaneous Emission mode (SASE FEL) requires the electron trajectory to be aligned with very high precision in overlap with the photon beam. In order to ensure this overlap, one module of the SASE FEL undulator at the TESLA Test Facility (TTF) is equipped with a new type of waveguide beam position monitor (BPM). Four waveguides are arranged symmetrically around the beam pipe, each channel couples through a small slot to the electromagnetic beam field. The induced signal depends on the beam intensity and on the transverse beam position in terms of beam--to--slot distance. With four slot--waveguide combinations a linear position sensitive signal can be achieved, which is independent of the beam intensity. The signals transduced by the slots are transferred by ridged waveguides through an impedance matching stage into a narrowband receiver tuned to 12 GHz. The present thesis describes design, tests, and implementation of this new type of BPM.