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Pande, Jayant Verfasser], and Ana-Sunčana [Gutachter] [Smith. "Analytical and numerical study of microswimming using the 'bead-spring model' / Jayant Pande ; Gutachter: Ana-Suncana Smith." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1123284288/34.
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Pande, Jayant [Verfasser], and Ana-Sunčana [Gutachter] Smith. "Analytical and numerical study of microswimming using the 'bead-spring model' / Jayant Pande ; Gutachter: Ana-Suncana Smith." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1123284288/34.
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Paudyal, Nabina. "Brownian Dynamics Simulation Of A Five-site Model for a Motor Protein on a Bead-Spring Substrate." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415390064.
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Pei, Hongxia. "Bead Modeling of Transport Properties of Macromolecules in Free Solution and in a Gel." Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/chemistry_diss/49.
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On the bead modeling methodology, or BMM, a macromolecule is modeled as a rigid, non-overlapping bead array with arbitrary radii. The BMM approach was pioneered by Kirkwood and coworkers (Kirkwood, J.G., Macromolecules, E.P. Auer (Ed.), Gordon and Breach, New York, 1967; Kirkwood, J.G., Riseman, J., J. Chem. Phys., 1948, 16, 565) and applied to such transport properties as diffusion, sedimentation, and viscosity. With the availability of computers, a number of investigators extended the work to account for the detailed shape of biomolecules in the 1970s. A principle objective of my research has been to apply the BMM approach to more complex transport phenomena such as transport in a gel, electrophoresis (free solution and in a gel), and also transport in more complex media (such as the viscosity of alkanes and benzene). Variables considered by the BMM include the number of beads (N), the radii of the beads, net charge and charge distribution, conformations, salt type, and salt concentration. The BMM has been extended to: (1) account for the existence of a gel; (2) characterize the charge and secondary structure of macromolecules; (3) account more accurately for hydrodynamic interaction (remove the orientationnal preaveraging approximation of hydrodynamic interaction); (4) study the effect of ion relaxation for particles in arbitrary size, shape, and charge; (5) consider the salt dependence of electrokinetic properties; (6) account for the formation of possible complex between guest ions and BGE ions. We also did diffusion constant measurement by NMR for amino acids and short peptides in 10%D2O-90% H2O at room temperature and applied to our modeling study by BMM.
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Xin, Yao. "Electrokinetic Modeling of Free Solution Electrophoresis." Digital Archive @ GSU, 2007. http://digitalarchive.gsu.edu/chemistry_diss/18.
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Modeling electrophoresis of peptides, proteins, DNA, blood cells and colloids is based on classical electrokinetic theory. The coupled field equations-Poisson, Navier-Stokes or Brinkman, and ion transport equations are solved numerically to calculate the electrophoretic mobilities. First, free solution electrophoretic mobility expressions are derived for weakly charged rigid bead arrays. Variables include the number of beads (N), their size (radius), charge, distribution (configuration), salt type, and salt concentration. We apply these mobility expressions to rings, rigid rods, and wormlike chain models and then apply the approach to the electrophoretic mobilities and translational diffusion constants of weakly charged peptides. It is shown that our bead model can predict the electrophoretic mobilities accurately. In order to make the method applicable at higher salt concentrations and/or to models consisting of larger sized subunits, account is taken of the finite size of the beads making up the model structure. For highly charged particles, it is also necessary to account for ion relaxation. This ion relaxation effect is accounted for by correcting "unrelaxed" mobilities on the basis of model size and average electrostatic surface, or "zeta" potential. With these corrections our model can be applied to the system with absolute electrophoretic mobilities exceeding approximately 0.20 cm2/kV sec and also models involving larger subunits. This includes bead models of duplex DNA. Along somewhat different lines, we have investigated the electrophoresis of colloidal particles with an inner hard core and an outer diffusive layer ("hairy" particles). An electrokinetic gel layer model of a spherical, highly charged colloid particle developed previously, is extended in several ways. The charge of the particle is assumed to arise from the deprotonation of acidic groups that are uniformly distributed over a portion (or all) of the gel layer. Free energy considerations coupled with Poisson-Boltzmann theory is used to calculate the change of the local pKa of the acidic groups depending on the local electrostatic environment. Based on the modeling of electrophoresis and viscosity, we predict that the thickness of the gel layer decreases as the salt concentration increases. And only the outermost portion of the gel layer is charged.
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Wang, Zifeng. "Langevin Dynamics Simulation of Catenaned Polymer Translocation through A Nanopore under A Driving Force." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619736392349226.
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Mackura, Mark. "Nano-confinement Effects of Crystalline Walls on the Glass Transition of a Model Polymer." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1366815752.
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Sun, Wangru. "Modèle de forêts enracinées sur des cycles et modèle de perles via les dimères." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS007/document.
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Le modèle de dimères, également connu sous le nom de modèle de couplage parfait, est un modèle probabiliste introduit à l'origine dans la mécanique statistique. Une configuration de dimères d'un graphe est un sous-ensemble des arêtes tel que chaque sommet est incident à exactement une arête. Un poids est attribué à chaque arête et la probabilité d'une configuration est proportionnelle au produit des poids des arêtes présentes. Dans cette thèse, nous étudions principalement deux modèles qui sont liés au modèle de dimères, et plus particulièrement leur comportements limites. Le premier est le modèle des forêts couvrantes enracinées sur des cycles (CRSF) sur le tore, qui sont en bijection avec les configurations de dimères via la bijection de Temperley. Dans la limite quand la taille du tore tend vers l'infini, la mesure sur les CRSF converge vers une mesure de Gibbs ergodique sur le plan tout entier. Nous étudions la connectivité de l'objet limite, prouvons qu'elle est déterminée par le changement de hauteur moyen de la mesure de Gibbs ergodique et donnons un diagramme de phase. Le second est le modèle de perles, un processus ponctuel sur $\mathbb{Z}\times\mathbb{R}$ qui peut être considéré comme une limite à l'échelle du modèle de dimères sur un réseau hexagonal. Nous formulons et prouvons un principe variationnel similaire à celui du modèle dimère \cite{CKP01}, qui indique qu'à la limite de l'échelle, la fonction de hauteur normalisée d'une configuration de perles converge en probabilité vers une surface $h_0$ qui maximise une certaine fonctionnelle qui s'appelle "entropie". Nous prouvons également que la forme limite $h_0$ est une limite de l'échelle des formes limites de modèles de dimères. Il existe une correspondance entre configurations de perles et (skew) tableaux de Young standard, qui préserve la mesure uniforme sur les deux ensembles. Le principe variationnel du modèle de perles implique une forme limite d'un tableau de Young standard aléatoire. Ce résultat généralise celui de \cite{PR}. Nous dérivons également l'existence d'une courbe arctique d'un processus ponctuel discret qui encode les tableaux standard, defini dans \cite{Rom}The dimer model, also known as the perfect matching model, is a probabilistic model originally introduced in statistical mechanics. A dimer configuration of a graph is a subset of the edges such that every vertex is incident to exactly one edge of the subset. A weight is assigned to every edge, and the probability of a configuration is proportional to the product of the weights of the edges present. In this thesis we mainly study two related models and in particular their limiting behavior. The first one is the model of cycle-rooted-spanning-forests (CRSF) on tori, which is in bijection with toroidal dimer configurations via Temperley's bijection. This gives rise to a measure on CRSF. In the limit that the size of torus tends to infinity, the CRSF measure tends to an ergodic Gibbs measure on the whole plane. We study the connectivity property of the limiting object, prove that it is determined by the average height change of the limiting ergodic Gibbs measure and give a phase diagram. The second one is the bead model, a random point field on $\mathbb{Z}\times\mathbb{R}$ which can be viewed as a scaling limit of dimer model on a hexagon lattice. We formulate and prove a variational principle similar to that of the dimer model \cite{CKP01}, which states that in the scaling limit, the normalized height function of a uniformly chosen random bead configuration lies in an arbitrarily small neighborhood of a surface $h_0$ that maximizes some functional which we call as entropy. We also prove that the limit shape $h_0$ is a scaling limit of the limit shapes of a properly chosen sequence of dimer models. There is a map form bead configurations to standard tableaux of a (skew) Young diagram, and the map is measure preserving if both sides take uniform measures. The variational principle of the bead model yields the existence of the limit shape of a random standard Young tableau, which generalizes the result of \cite{PR}. We derive also the existence of an arctic curve of a discrete point process that encodes the standard tableaux, raised in \cite{Rom}
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Kriuchevskyi, Ivan. "Mechanical and viscoelastic properties of glass-forming polymers in the bulk and thin films : molecular dynamics study of model systems." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE044/document.
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En nous concentrant sur les valeurs du module de cisaillement l’équilibre Geq pour le modèle bien connu des polymères vitrifiables (echantillionné par le biais de la MD), nous avons adressé la question générale de en quoi les propriétées méchaniques des couches mince diffères de la phase volumique. Il a été démontrè que dans les deux cas Geq de manière non ambigus sèpare l’état fluide (Geq = 0) de l’état vitreux (Geq > 0). Nous avons aussi insisté sur le fait que Geq pour la couche mince dépend de lépaisseur du film h mais aussi de de la pression tangentielle qui est un résultante de la procédure de préparation de la couche minceFocusing on the equilibrium shear modulus Geq of well-known glass-forming polymer model system (sampled by means of MD), we have addressed the general question of how the mechanical properties of the thin polymer films differs from the bulk. Using ”stress fluctuation” formalism we obtained Geq(T) for the bulk and films. It has been demonstrated that in both cases Geq unambiguously separates the fluid state (Geq = 0) from the glass (Geq > 0). We also stressed that Geq for the film does not only depend on film thickness h, but also on tangential pressure that is a consequence of the film preparation procedure
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Hove, Darlington. "Finite element analysis of a composite sandwich beam subjected to a four point bend." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/1465.
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The work in this dissertation deals with the global structural response and local damage effects of a simply supported natural fibre composite sandwich beam subjected to a four-point bend. For the global structural response, we are investigating the flexural behaviour of the composite sandwich beam. We begin by using the principle of virtual work to derive the linear and nonlinear Timoshenko beam theory. Based on these theories, we then proceed to develop the respective finite element models and then implement the numerical algorithm in MATLAB. Comparing the numerical results with experimental results from the CSIR, the numerical model correctly and qualitatively recovers the underlying mechanics with some noted deviances which are explained at the end. The local damage effect of interest is delamination and we begin by reviewing delamination theory with more emphasis on the cohesive zone model. The cohesive zone model relates the traction at the interface to the relative displacement of the interface thereby creating a material model of the interface. We then carry out a cohesive zone model delamination case study in MSC.Marc and MSC.Mentat software packages. The delamination modelling is carried out purely as a numerical study as there are no experimental results to validate the numerical results.
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Corre, Grégoire. "Enriched elasto-plastic beam model." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1031/document.
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Ce travail s'inscrit dans le cadre d'un partenariat scientifique entre le Laboratoire Navier et la société STRAINS. Convaincue du besoin de renouveler les méthodes actuelles de calcul de structures, STRAINS développe un nouveau logiciel dédié à l'analyse des ouvrages d'art. Dans ce contexte, cette thèse propose de nouveaux outils pour l'analyse des structures élancées. Le modèle élastique de poutre d'ordre supérieur développé par cite{Ferradi2016} est d'abord adapté au cas des déformations imposées, permettant ainsi au modèle de représenter un grand nombre de phénomènes physiques tels que le fluage, la précontrainte ou les chargements thermiques. Différents exemples viennent souligner la précision numérique du modèle ainsi que ses performances en temps de calcul. Le modèle est également étendu au cadre de la théorie de la plasticité. Considérant les déformations plastiques comme des déformations imposées, les résultats précédemment obtenus sont utilisés pour développer une nouvelle cinématique d'ordre supérieur. Enfin, un nouvel élément de poutre élastoplastique pour le béton armé est proposé. Le béton est décrit grâce au modèle élastoplastique et les ferraillages sont modélisés par des éléments barres à une dimension. Cette méthode permet une description précise du comportement du béton et une représentation fidèle des renforcements. La validité des calculs est évaluée par des considérations de dissipation énergétiqueThis thesis work is presented in the framework of a scientific partnership between Laboratoire Navier and the french start-up STRAINS. Believing in the need for new methodologies in structural analysis, STRAINS is developing a new software dedicated to the structural analysis of bridges. In this context, this work suggests new tools for the analysis of slender structures.The higher-order elastic beam element developed by cite{Ferradi2016} is first extended to the case of eigenstrains, enabling the model to deal with various physical phenomena such as creep, prestress or thermal loads. An enriched kinematics is used to capture the local response of the structure. Different examples highlight the local accuracy of the model and its fast computational performances. The model is also extended to plasticity in small perturbations. Considering the plastic strains developing in the structure as eigenstrains, the previous works are used to derive a higher-order elastoplastic kinematics.Finally, a new elastoplastic beam element for reinforced concrete is suggested. The concrete material is described by using the elastoplastic beam model developed previously while steel rebars are modeled by one dimensional bar elements. This method enables a fine local description of the concrete behavior and an accurate representation of the reinforcement. The validity of computations is assessed thanks to energy considerations
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Hodgson, Susanne H. "Using the controlled human malaria infection model to investigate immunity to malaria." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:b3c9a2eb-beab-4ef6-bd8d-483390f316b8.
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Controlled human malaria infection (CHMI) studies, where healthy volunteers are infected with Plasmodium falciparum have become a vital tool to accelerate vaccine and drug development. As CHMI trials are carried out in a controlled environment, they allow unprecedented, detailed evaluation of parasite growth dynamics and immunological responses to infection. Though commonly performed in malaria-naïve populations, CHMI trials have rarely been conducted in malaria-endemic regions and to date, have not been used to investigate naturally acquired immunity (NAI) to P. falciparum infection. This thesis describes the first CHMI study in Kenya and the first attempt to use the modern CHMI model to explore the dynamics and mechanisms of NAI. Using samples collected post-CHMI from both UK volunteers and Kenyan subjects with varying prior exposure to P. falciparum, this work reports and compares the findings of key in vitro assays including GIA, ADRB activity and changes in gene expression in order to understand the effect of NAI on these measures.
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Deshmukh, Prutha. "Damage Detection Of a Cantilever Beam Using Digital Image Correlation." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623169831665585.
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Chirravuri, Varun R. "Identifying a low-order beat-to-beat model of arterial baroreflex action." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61152.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 127-133).
The arterial baroreflex is a fast-acting control mechanism that the body relies on to regulate blood pressure. Previous efforts to quantitatively model the baroreflex have relied primarily on non-parametric characterization of the transfer function from blood pressure to heart rate (Berger et al.,1989, Akselrod et al., 1981,1985). Of the parametric models proposed, most focus on matching empirical transfer functions with continuous-time models (Berger et al., 1991). Use of these models is often restricted to simulation, and consequently not focused on prediction. We develop a beat-to-beat, one-pole model for the baroreflex that can parsimoniously capture both the empirical frequency-domain and time-domain characteristics of the baroreflex. Further, we develop a robust identification method for on-line estimation of our model parameters from clinical data. We conclude by presenting preliminary results of our model and estimation method applied to patients undergoing drug-induced autonomic blockade.
by Varun R. Chirravuri.
M.Eng.
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Archard, Daniel. "Molecular beam studies of model NSR catalysts." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54721/.
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The adsorption and reaction of various simple molecules (O2, NO, CO and NO2) commonly associated with gasoline engine exhaust catalysis were investigated on a model catalytic system under ultra-high vacuum conditions using a variety of surface science techniques including molecular beam scattering and temperature programmed desorption. The model catalytic surfaces studied were clean Pt(111), K/Pt(111) and BaO/Pt(111) surfaces. The alkaline and alkaline earth metal surfaces were prepared by metal vapour deposition (in an oxygen background in the case of BaO) and annealing. Also investigated was the ability of each of the catalytic surfaces to oxidise NO and CO and to store and reduce NO2. It was found that the clean Pt(111) surface was effective at oxidising CO provided the oxygen was in an adsorbed atomic form. Pt(111) was also found to be effective in the reduction of NO2 . NO and O2 were found to react in a gas phase reaction that made mixed molecular beam studies problematic however it was found when beaming NO with a background pressure of O2 that no Pt(111) catalysed surface reaction was observed. It was found that dosing K onto the Pt(111) surface increased the sticking coefficient of oxygen greatly and that more than a monolayer of K on the surface catalysed the reduction of NO to N2. Unlike the Pt(111) surface, K/Pt(111) was capable of storing NO2 without it being immediately reduced. Potassium peroxide however was found to prevent NO2 storage. In a similar fashion to K, NO2 was stored on BaO, being released as NO and O2 on heating. NO is partially reduced to N2O by the BaO surface at ambient temperature with increased temperature favouring complete reduction to N2.
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Kircali, Omer Faruk. "Active Vibration Control Of A Smart Beam: A Spatial Approach." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607555/index.pdf.
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This study presented the design and implementation of a spatial Hinf controller to suppress the free and forced vibrations of a cantilevered smart beam. The smart beam consists of a passive aluminum beam with surface bonded PZT (Lead-Zirconate-Titanate) patches. In this study, the PZT patches were used as the actuators and a laser displacement sensor was used as the sensor.
In the first part of the study, the modeling of the smart beam by the assumed-modes method was conducted. The model correction technique was applied to include the effect of out-of-range modes on the dynamics of the system. Later, spatial system identification work was performed in order to clarify the spatial characteristics of the smart beam.
In the second part of the study, a spatial Hinf controller was designed for suppressing the first two flexural vibrations of the smart beam. The efficiency of the controller was verified both by simulations and experimental implementation.
As a final step, the comparison of the spatial and pointwise Hinf controllers was employed. A pointwise Hinf controller was designed and experimentally implemented. The efficiency of the both controllers was compared by simulations.
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Huang, Yue. "Dynamic model of circulating fluidized bed." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4823.
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Thesis (Ph. D.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains ix, 133 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 103-114).
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Frey, Stephan. "Propriétés viscoélastqiues des fondus de polymères vitrifiables." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAE008/document.
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À l'approche de la transition vitreuse les fondus de polymères montrent une augmentation importante de la viscosité de plusieurs ordres de grandeur. Le but de cette étude est d'acquérir une compréhension plus profonde des propriétés viscoélastiques des fondus de polymères vitrifiables. Les polymères sont modélisés comme des chaînes flexibles en utilisant un modèle de bille-ressort. Les propriétés dynamiques sont analysées dans le cadre de la théorie de couplage de mode idéale. Nous constatons que la température critique de couplage de mode varie avec l'inverse de la longueur de chaîne. En étudiant la fonction de relaxation de cisaillement, nous constatons que les processus de relaxation polymériques, ne sont pas modifiés, mais décalés vers des temps plus importants en approchant la transition vitreusePolymer melts show a remarkable increase of their viscosity by many orders of magnitude on approaching the glass transition. The aim of this study is to gain a deeper insight into the viscoelastic properties of glass forming polymer melts. The polymers are modeled as flexible chains using a bead-spring model. The dynamic properties are analyzed in the framework of the ideal mode-coupling theory. We find that the critical temperature of the ideal mode-coupling theory scales with the reciprocal chain length. By studying the shear relaxation function we find that the polymer relaxation processes are not altered but shifted to later times in the approach of the glass transition
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Williams, Timothy Joe. "Statistically constrained decimation of a turbulence model." W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539623778.
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The constrained decimation scheme (CDS) is applied to a turbulence model. The CDS is a statistical turbulence theory formulated in 1985 by Robert Kraichnan; it seeks to correctly describe the statistical behavior of a system using only a small sample of the actual dynamics. The full set of dynamical quantities is partitioned into groups, within each of which the statistical properties must be uniform. Each statistical symmetry group is then decimated down to a small sample set of explicit dynamics. The statistical effects of the implicit dynamics outside the sample set are modelled by stochastic forces.;These forces are not totally random; they must satisfy statistical constraints in the following way: Full-system statistical moments are calculated by interpolation among sample-set moments; the stochastic forces are adjusted by an iterative process until decimated-system moments match these calculated full-system moments. Formally, the entire infinite heirarchy of moments describing the system statistics should be constrained. In practice, a small number of low-order moment constraints are enforced; these moments are chosen on the basis of physical insights and known properties of the system.;The system studied in this work is the Betchov model--a large set of coupled, quadratically nonlinear ordinary differential equations with random coupling coefficients. This turbulence model was originally devised to study another statistical theory, the direct interaction approximation (DIA). By design of the Betchov system, the DIA solution for statistical autocorrelation is easy to obtain numerically. This permits comparison of CDS results with DIA results for Betchov systems too large to be solved in full.;The Betchov system is decimated and solved under two sets of statistical constraints. Under the first set, basic statistical properties of the full Betchov system are reproduced for modest decimation strengths (ratios of full-system size to decimated-system size); however, problems arise at stronger decimation. These problems are solved by the second set of constraints. The second constraint set is intimately related to the DIA; that relationship is shown, and results from the CDS under those constraints are shown to approach the DIA results as the decimation strength increases.
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Perilla, Rozo Carlos Andres. "Noise model for a dual frequency comb beat." Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/34414.
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Cette thèse porte sur le raffinement d’un modèle du bruit utilisé pour des mesures spectroscopiques réalisées avec des peignes de fréquences optiques. La majorité des travaux antérieurs utilisaient des peignes de fréquences où le glissement (chirp) est minimisé, en supposant que tout glissement différentiel entre les peignes allait réduire le rapport signal sur bruit. L’hypothèse sous-jacente était que l’impact du bruit multiplicatif serait augmenté, le glissement lui permettant d’agir plus longtemps sur le signal d’interférence. Cependant, d’autres recherches indiquaient plutôt contraire : le chirp pourrait améliorer la mesure. Cette thèse cherche à augmenter la compréhension du comportement du bruit lorsque les peignes ont des glissements différentiels. De plus, celle-ci apporte de nouvelles évidences sur l’utilité du chirp dans ce type de mesure. À cet effet, nous avons fait une révision bibliographique des modèles du bruit dans les peignes de fréquences optiques. Ensuite, du point de vue théorique, nous avons analysé les effets du chirp sur les bruits additifs et multiplicatifs. Pour le bruit d’intensité, nous avons proposé un modèle phénoménologique décrivant le comportement de l’émission spontanée amplifiée (ASE) dans un laser à verrouillage de mode par rotation non linéaire de polarisation. Les spectres des peignes et leurs battements ont été caractérisés en portant une attention particulière à leur relation avec l’ASE. La thèse permet de conclure que le chirp différentiel n’affecte pas les niveaux des densités spectrales de bruit. Grâce au glissement différentiel de fréquence, il est possible d’envoyer plus puissance à l’échantillon et ainsi améliorer le rapport signal sur bruit des instruments à peignes de fréquence. D’un autre côté, la caractérisation de l’ASE a établi sa nature non-stationnaire. Elle a aussi expliqué des attributs spectraux qui sont observés régulièrement dans les signaux de battement des peignes. Finalement, en supposant que l’ASE circule largement dans une cavité opérée sous le seuil, sa caractérisation fournit une méthode pour estimer le déphasage non linéaire que subit le train d’impulsions femtosecondes.This thesis proposes a noise model refinement for spectroscopic measurements using dual optical frequency combs. Until now most studies centered their efforts on noise characterization using chirp free combs based on an unproved hypothesis: measurements would get worse with chirped combs since multiplicative noises would be present over a longer duration on the interference pattern thus leading to a greater impact. However, at least one experimental result hinted to the contrary: differential chirp would actually improve the signal to noise ratio. This thesis therefore aims at increasing the understanding of noise when a differential chirp is present in a dual comb measurement. The specific goal is to provide new insights about the usefulness of chirp in this kind of measurement. With this in mind, we conducted a literature review of noise models in optical frequency combs. We subsequently analyzed the chirp’s effect in the presence of both additive and multiplicative noise. The thesis also proposes a phenomenological model to describe the amplified spontaneous emission - ASE in short pulse lasers mode locked using non linear polarization rotation. Finally the comb spectra and their beat notes are characterized putting special attention to their relation with the ASE components. As conclusions, we can report that noise power spectral density levels do not change with a differential chirp. Chirping allows sending a greater optical power through the sample, such that the measurement signal to noise ratio can be improved. On the other hand, the ASE characterization established its non-stationary nature and explained very well characteristic features routinely observed in dual comb beat notes that were not fully understood. Finally, assuming the ASE experiences a sub threshold linear cavity allows using theses features to estimate the non linear phase shift experienced by the modelocked pulse train in the laser cavity.
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Wild, Michelle Anne. "Growth dynamics of braided gravel-bed river deltas in New Zealand." Thesis, University of Canterbury. Dept of Civil and Natural Resources Engineering, 2013. http://hdl.handle.net/10092/8456.
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This research has been undertaken to further our knowledge of decade-to-century timescale braided, gravel-bed river delta growth dynamics. The study included: a review of available literature; field studies; the development of microscale models for two study deltas; and the development of a simple numerical model incorporating movement of braided river channels across a delta topset (varying the location of sediment delivery to the delta).
Results from the microscale modelling showed that successful physical modelling requires well-defined fixed boundaries and, ideally, good historical aerial photography for the estimation of the model time scale. A complex braided gravel-bed river delta system composed of two merging deltas entering a deep, low-energy receiving basins was able to be successfully modelled to provide valuable information on delta growth dynamics. However, a microscale model of a delta prograding into shallow receiving basins, with a large supply of fine sediment, was more difficult to calibrate and assess (partly due to limited field data), and was considered less reliable.
The simple rule-based numerical model ‘DELGROW’, developed to simulate a braided river system entering a deep, low-energy body of water, requires a known sediment supply rate, as well as information on the braided river topography, submerged delta foreset, and lakebed bathymetry. Unlike simple 1-d width-averaged geometric models, DELGROW takes into consideration barriers (e.g. islands) as well as relatively complex converging braided river delta configurations. By changing the sediment supply, or modifying the river system, the response of the river system to various scenarios can also be assessed.
Microscale models and DELGROW appear to realistically simulate decade-to-century timescale growth of braided gravel-bed river deltas entering a deep, low-energy, receiving basin. Both of these modelling methods initially use the supplied sediment to try and eliminate any riverbed irregularities (e.g. low areas), before continuing to advance and deposit sediment in a more evenly-distributed manner, whilst taking into consideration irregularities due to barriers, and asymmetric sediment sources such as merging deltas. Neither model can reliably predict locations of bank erosion, or channel avulsions that divert flow and sediment outside of the fixed model boundaries.
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Hou, Chuanchuan. "Vibration-based damage identification with enhanced frequency dataset and a cracked beam element model." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20434.
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Damage identification is an important topic in structural assessment and structural health monitoring (SHM). Vibration-based identification techniques use modal data to identify the existence, location and severity of possible damages in structures, often via a numerical model updating procedure. Among other factors influencing the practicality and reliability of a damage identification approach, two are of primary interest to this study. The first one concerns the amount and quality of modal data that can be used as ‘response’ data for the model updating. It is generally recognised that natural frequencies can be measured with relatively high accuracy; however, their number is limited. Mode shapes, on the other hand, are susceptible to larger measurement errors. Seeking additional modal frequency data is therefore of significant value. The second one concerns the errors at the numerical (finite element) model level, particularly in the representation of the effect of damage on the dynamic properties of the structure. An inadequate damage model can lead to inaccurate and even false damage identification. The first part of the thesis is devoted to enhancing the modal dataset by extracting the so called ‘artificial boundary condition’ (ABC) frequencies in a real measurement environment. The ABC frequencies correspond to the natural frequencies of the structure with a perturbed boundary condition, but can be generated without the need of actually altering the physical support condition. A comprehensive experimental study on the extraction of such frequencies has been conducted. The test specimens included steel beams of relatively flexible nature, as well as thick and stiffer beams made from metal material and reinforced concrete, to cover the typical variation of the dynamic characteristics of real-life structures in a laboratory condition. The extracted ABC frequencies are subsequently applied in the damage identification in beams. Results demonstrate that it is possible to extract the first few ABC frequencies from the modal testing in different beam settings for a variety of ABC incorporating one or two virtual pin supports. The inclusion of ABC frequencies enables the identification of structural damages satisfactorily without the necessity to involve the mode shape information. The second part of the thesis is devoted to developing a robust model updating and damage identification approach for beam cracks, with a special focus on thick beams which present a more challenging problem in terms of the effect of a crack than slender beams. The priority task has been to establish a crack model which comprehensively describes the effect of a crack to reduce the modelling errors. A cracked Timoshenko beam element model is introduced for explicit beam crack identification. The cracked beam element model is formulated by incorporating an additional flexibility due to a crack using the fracture mechanics principles. Complex effects in cracked thick beams, including shear deformation and coupling between transverse and longitudinal vibrations, are represented in the model. The accuracy of the cracked beam element model for predicting modal data of cracked thick beams is first verified against numerically simulated examples. The consistency of predictions across different modes is examined in comparison with the conventional stiffness reduction approach. Upon satisfactory verification, a tailored model updating procedure incorporating an adaptive discretisation approach is developed for the implementation of the cracked beam element model for crack identification. The updating procedure is robust in that it has no restriction on the location, severity and number of cracks to be identified. Example updating results demonstrate that satisfactory identification can be achieved for practically any configurations of cracks in a beam. Experimental study with five solid beam specimens is then carried out to further verify the developed cracked beam element model. Both forward verification and crack damage identification with the tested beams show similar level of accuracy to that with the numerically simulated examples. The cracked beam element model can be extended to crack identification of beams with complex cross sections. To do so the additional flexibility matrix for a specific cross-section type needs to be re-formulated. In the present study this is done for box sections. The stress intensity factors (SIF) for a box section as required for the establishment of the additional flexibility matrix are formulated with an empirical approach combining FE simulation, parametric analysis and regression analysis. The extended cracked beam element model is verified against both FE simulated and experimentally measured modal data. The model is subsequently incorporated in the crack identification for box beams. The successful extension of the cracked beam element model to the box beams paves the way for similar extension to the crack identification of other types of sections in real-life engineering applications.
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Titievsky, Kirill. "Physical interpretation of coarse-grained bead-spring models of complex fluids." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/46597.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.Includes bibliographical references (leaves 143-148).
Bulk properties and morphology of block copolymers and polymer blends are highly sensitive to processing history due to small free energy differences among various stable and metastable states. Consequently, modeling these materials requires accounting for both thermal fluctuations and non-equilibrium processes. This has proven to be challenging with traditional approaches of energy minimization and perturbation in field theories. At the same time, simulations of highly coarse-grained particle-based models, such as lattice chain Monte Carlo and bead-spring simulations, have emerged as a promising alternative. The application of these methods, however, has been hampered by a lack of clear physical interpretation of model parameters.This dissertation gives a rigorous interpretation to such coarse-grained models. First, a general thermodynamic approach to analyzing and comparing coarse-grained particle models is developed. Second, based on the analysis, a specific particle-based model is constructed so that it is unambiguously related to the standard Gaussian chain model and related field theories at realistic molecular weights. This model is complementary to field theoretic polymer simulations, which are computationally prohibitive for realistic molecular weights. Several applications of the model are demonstrated, including: fluctuation corrections to mean-field theories of block copolymers as well as a detailed investigation of the key effects governing the self-assembly of diblock copolymers confined in cylinders such as fibers or pores. The latter application introduces a novel impenetrable wall boundary model designed to attenuate effects of the walls on the total monomer density. The general approach and the specific models proposed here will find immediate application in modeling effects of flow, metastability, and thermal fluctuations on the morphology of complex fluids with molecular weights of 104 - 106 g/mol using lattice and continuous space molecular simulations.
by Kirill Titievsky.
Ph.D.
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Capoani, Federico. "Adiabatic extraction models for beam dynamics." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12056/.
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Il presente lavoro prende le mosse da un problema di dinamica
dei fasci relativo a un metodo di separazione di un fascio di particelle recentemente messo in funzione nell’sincrotrone PS al CERN. In questo sistema, variando adiabaticamente i parametri di un campo magnetico, nello spazio delle fasi si creano diverse isole di stabilità (risonanze) in cui le particelle vengono catturate.
Dopo una parte introduttiva in cui si ricava, a partire dalle equazioni di Maxwell, l’hamiltoniana di una particella sottoposta ai campi magnetici che si usano negli acceleratori, e una presentazione generale della teoria dell’invarianza adiabatica, si procede analizzando la dinamica di tali sistemi.
Inizialmente si prende in considerazione l’hamiltoniana mediata
sulle variabili veloci, considerando perturbazioni (kick) dei termini dipolare e quadrupolare. In ognuno dei due casi, si arriva a determinare la probabilità che una particella sia catturata nella risonanza.
Successivamente, attraverso un approccio perturbativo, utilizzando le variabili di azione ed angolo, si calcola la forza della risonanza 4:1 per un kick quadrupolare.
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Staley, Alan Joseph. "A Finite Difference Approach to Modeling High Velocity/Variable Loads using the Timoshenko Beam Model." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76954.
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Electromagnetic launchers (railguns) are set to replace traditional large caliber ship mounted cannons in the near future. The success of the railgun depends heavily upon a comprehensive understanding of beam behavior during periods of heavy dynamic loading. It is hypothesized that the combination of velocity transition effects, electromagnetic loading, and other non-linear or design specific effects contribute to areas of high stresses/strains over the length of the rail/beam during launch.
This paper outlines the use of the Timoshenko beam model, a model which builds upon the traditional Bernoulli-Euler beam theory with the addition of shear deformation and rotary inertia effects, a necessity for high wave velocities. Real-world experimental setups are simplified and approximated by a series of linear springs and dampers for model prediction and validation.
The Timoshenko beam model is solved using finite difference (FD) methods for the approximation of spatial derivatives and MATLAB ordinary differential equation (ODE) solvers. The model shows good convergence and precision over a large range of system parameters including load velocities, foundation stiffness values, and beam dimensions. Comparison to experimental strain data has validated model accuracy to an acceptable level. Accuracy is further enhanced with the inclusion of damping and non-linear or piecewise effects used to mimic experimental observations. The MATLAB software package presents a valid preliminary analysis tool for railgun beam and foundation design while offering advantages in ease of use, computation time, and system requirements when compared to traditional FEA tools.Master of Science
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Tang, Gaven. "Two-dimensional mobile-bed dam-break model." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43508.
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Sudden and catastrophic dam-breaks typically induce high bed shear stresses downstream as the flood-wave propagates over the alluvial channel and flood plain. In fact, the non-dimensionalized shear stresses are often high enough that they are comparable to those typically seen in the transport of sand. Despite the existence of these shear stresses, industry typically ignores sediment transport altogether and assumes a fixed-bed when modelling dam-breaks. This thesis will examine the validity of the fixed-bed assumption and create a depth-averaged 2D mobile-bed dam-break model. This model will then be tested by simulating the Malpasset (France) dam-break of 1959, and a sensitivity analysis will then be performed on the parameters of grain roughness, vegetation roughness, friction angle, grain size, and depth to bedrock to examine differences in inundation and flood-wave propagation.
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Chua, Kel Win. "Predictive model of fluidized bed melt granulation." Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505425.
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This thesis describes the development of a computer model that predicts aggregation behavior in fluidized bed melt granulation (FBMG) processes. In FBMG processes, the molten binder enters at one or more points and is then distributed around the bed, these processes are necessarily spatially inhomogeneous. Current granulation modelling using Population Balance Equations (PBE) adopts a lumped approach, using a single lumped rate constant. This thesis shows how to take account of these spatially distributed processes and then predicted the apparent lumped rate constant. The first half of this thesis presents a series of experimentally validated sub-models to describe time scales of events leading to aggregation. These events are granule-granule collision, droplet-granule collision, binder spreading and binder solidification. Computational Fluid Dynamic using a twin-fluid model is used to calculate granulegranule collision time scale and droplet-granule collision time scales. A Volume of Fluid method is used to calculate binder spreading time scales. A dynamic energy balance is used to calculate binder solidification time scales. Validation of the twin-fluid model is done by comparing fluidized bed pressure time series with experiment. Validation of spreading model is done using high speed images of binder droplet spreading. Validation of solidification model is done using high speed infrared images of binder droplet solidification on glass plate. Generalizations for binder spreading time scale and binder solidification time scale are made, so that these time scales for other FBMG process can be calculated directly, reducing the reliance on computational modelling. Granule-granule collision time scale per particle is in the region of O.Ols. Binder spreading time scale is less than O.OOls~ Binder solidification time scale varies from 0.005s to O.Ols. This wider variation for solidification time scale is caused by the effect of fluidized bed operating temperature. By separation of time scales, we evaluate probability that a granule is wet upon granulegranule collision. Binder contact angle determines the wetted area covered by single droplet. Droplet solidification time scale determines the lifetime of the wetted area. This probability is used to calculate granulation efficiency. Applying granulation efficiency with collision rates allows aggregation rate constants for different process variables in FBMG to be evaluated. Our evaluation found that most aggregation takes place within 5cm of the nozzle. In general the calculated aggregation rate constant is higher than the experimentally measured aggregation rate constant. \Ve attributed the unknown effects of averaging across granule SIze, the probability of liquid bridge survival and probability of solid bridge survival with an apparent probability of survival.
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Landesman, Barbara Tehan. "A new mathematical model for a propagating Gaussian beam." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184545.
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A new mathematical model for the fundamental mode of a propagating Gaussian beam is presented. The model is two-fold, consisting of a mathematical expression and a corresponding geometrical representation which interprets the expression in the light of geometrical optics. The mathematical description arises from the (0,0) order of a new family of exact, closed-form solutions to the scalar Helmholtz equation. The family consists of nonseparable functions in the oblate spheroidal coordinate system and can easily be transformed to a different set of solutions in the prolate spheroidal coordinate system, where the (0,0) order is a spherical wave. This transformation consists of two substitutions in the coordinate system parameters and represents a more general method of obtaining a Gaussian beam from a spherical wave than assuming a complex point source on axis. Further, each higher-order member of the family of solutions possesses an amplitude consisting of a finite number of higher-order terms with a zero-order term that is Gaussian. The geometrical interpretation employs the skew-line generator of a hyperboloid of one sheet as a ray-like element on a contour of constant amplitude in the Gaussian beam. The geometrical characteristics of the skew line and the consequences of treating it as a ray are explored in depth. The skew line is ultimately used to build a nonorthogonal coordinate system which allows straight-line propagation of a Gaussian beam in three-dimensional space. Highlights of the research into other methods used to model a propagating Gaussian beam--such as complex rays, complex point sources and complex argument functions--are reviewed and compared with this work.
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Ashiq, Mohammad. "Bed load transport models for coarse bed material rivers." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336301.
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Plan, Emmanuel Lance Christopher VI Medillo. "Retournement, flexion, étirement : particules dans les écoulements laminaires et chaotiques." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4032/document.
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Les particules soumises à un écoulement peuvent manifester des orientations préférées et une variété de déformations en fonction de leur géométrie et élasticité et du champ de vitesse de l'écoulement. A l’inverse, les flux peuvent être modifiés lorsque les contraintes des particules sont non négligeables. Cette thèse présente des résultats théoriques et numériques sur cette relation bilatérale en deux parties. La Ière partie commence par une analyse de stabilité et des simulations numériques qui montrent une particule brownienne semi-flexible dans un écoulement élongationnel effectuant un retournement, un phénomène associé aux flux de cisaillement. Le Chap. 2 étend les outils analytiques dédiés aux modèles simples ou aux flux indépendante du temps pour les modèles perle-barre-bond généraux dans les flux aléatoires. En partant des résultats des chapitres précédents, Le Chap. 3 aboutit à l'étude d'un degré de liberté lagrangien inexploré dans un écoulement turbulent : la flexion. Une particule semi-flexible courbe différemment dans les flux aléatoires bidimensionnels et tridimensionnels. La IIème partie concerne la turbulence élastique, un régime chaotique créé dans un écoulement de faibles forces inertielles par l'ajout de polymères élastiques. Le Chap. 4 estime le nombre de degrés de liberté d'une solution de ce régime via la dimension Lyapunov de l'attracteur du modèle Oldroyd-B bidimensionnel, un modèle connu de reproduire la turbulence élastique dans les simulations numériques. Le Chap. 5 pose des questions sur la nécessité d'élasticité pour produire un régime chaotique et conclut qu'une solution de polymère de barres peut créer un régime comparable à la turbulence élastiqueParticles, when subjected into a flow, may display preferred orientations and a variety of deformations depending on their geometry and elasticity and the flow velocity field. Flows can conversely be modified when the particle stresses are sufficiently large. This thesis presents theoretical and numerical results on this two-way relationship between particles and flows in two parts. Part I starts with a stability analysis and numerical simulations that show a simple semiflexible Brownian particle in an extensional flow undergo tumbling, a phenomenon normally associated to shear flows. Chapter 2 extends analytical tools available only for elementary polymer models or for steady flows to general bead-rod-spring models in random flows. By building on the results from the previous chapters, Chap. 3 culminates with the study of an unexplored Lagrangian degree of freedom in a turbulent flow: bending. A semiflexible particle is shown to display different bending behaviours in two- and three-dimensional random flows. This prediction is confirmed via direct numerical simulations of the particle in a turbulent flow. Part II concerns “elastic turbulence", a chaotic regime created in a flow with low inertial forces by the addition of elastic polymers. Chapter 4 provides an estimate for the number of degrees of freedom of a solution of this chaotic system via the Lyapunov dimension of the attractor of the two-dimensional Oldroyd-B model, a model known to reproduce elastic turbulence in numerical simulations. Chapter 5 questions the necessity of elasticity in producing a chaotic regime and concludes that a rodlike polymer solution can create a regime similar to elastic turbulence
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Ezeanochie, Tochukwu Chinedu. "Modelling and Simulation of Filopodial Protrusion." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32781.
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The effect of substrate surface topology on the interaction of living cells with inanimate substrates is a well-established phenomenon. When cells are placed on biomaterials, they outgrow protrusions called filopodia that sense surface features in their immediate surroundings and initiate the formation of stable cell adhesion complexes closer to the cell body. Adhesion proteins permit filopodia to constantly explore the surrounding microenvironment. A better understanding of the relationship of filopodia with surface features is highly relevant for exploiting custom-made surfaces to guide cell activity.
In this work, mathematical modeling and simulation were used to describe different phenomena related to the interaction of a filopodium with its microenvironment, with the aim of reproducing experimentally observed phenomena associated to filopodia growth and interactions with substrates. The Kelvin Voigt model was used for the viscoelastic response of filopodia. Result predict filopodia protrusion under test conditions and helps improving our understanding on the effect of substrate topology on the biomechanical response of filopodial extensions.
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Kang, Fatima Maria de Angelis. "Análise quantitativa de modelos de prototipagem rápida baseados em dados de tomografia volumétrica, por meio de inspeção de engenharia reversa tridimensional." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/23/23139/tde-27102009-095334/.
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O objetivo neste estudo foi avaliar a reprodutibilidade quantitativa dos modelos tridimensionais gerados por meio de imagens de tomografia volumétrica de feixe cônico, obtidos por dois tomógrafos volumétricos NEWTOM 9000 DVT (i- (Quantitative Radiology, Verona, Itália) e i-CAT (Imaging Sciencies Int. Hatfield, Pensilvânia. Estados Unidos da América), submetidos à inspeção de engenharia reversa. Uma mandíbula macerada foi digitalizada por meio do SCANNER 3D VIVID 910, com precisão de 0,01 mm, associado à fotometria digital, sendo utilizado o software GEOMAGIC STUDIO, e assim obteve-se um modelo considerado padrão ouro. Posteriormente realizamos o exame de tomografia volumétrica de feixe cônico, na mesma mandíbula nos dois tomógrafos volumétricos, obtendo-se assim os modelos virtuais tridimensionais. Por meio de um alinhamento das geometrias do padrão ouro com os modelos virtuais resultantes da tomografia do aparelho NEWTOM 9000 DVT e do i-CAT, foram observadas as possíveis discrepâncias. Concluímos que estas alterações encontradas após a análise quantitativa das diversas regiões foram menores nas imagens adquiridas pelo tomógrafo volumétrico de feixe cônico modelo i-CAT, e portanto possibilitam a geração de modelos de prototipagem rápida de melhor qualidade.The purpose of this study was to evaluate the quantitative reproductability of the 3d models created using CT images. The images used were obtained from two different cone beam tomographs: NEWTOM 9000 DVT (Quantitative Radiology, Verona, Italy) and i-CAT ( Imaging Sciences Int., Hatfield, EUA) and then inspected through reverse engineering processing software. A dry mandible was digitalized using a 3D Scanner VIVID 910 and the GEOMAGIC STUDIO software to obtain a 0,01mm precision model considered to be our gold standard. Two distinct 3D virtual models were then created after submitting the same dry mandible to a cone beam exam on both tomographs (NEWTOM and i-Cat). Possible discrepancies between the 3D models and the gold standard were analyzed through and alignment of their geometries. After evaluating the discrepancies at the different sites of the models, we concluded that the virtual model obtained using the i-Cat tomograph images was more accurate and therefore of greater quality.
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Lu, Yunkai. "Random Vibration Analysis of Higher-Order Nonlinear Beams and Composite Plates with Applications of ARMA Models." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29128.
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In this work, the random vibration of higher-order nonlinear beams and composite plates subjected to stochastic loading is studied. The fourth-order nonlinear beam equation is examined to study the effect of rotary inertia and shear deformation on the root mean square values of displacement response. A new linearly coupled equivalent linearization method is proposed and compared with the widely used traditional equivalent linearization method. The new method is proven to yield closer predictions to the numerical simulation results of the nonlinear beam vibration. A systematical investigation of the nonlinear random vibration of composite plates is conducted in which effects of nonlinearity, choices of different plate theories (the first order shear deformation plate theory and the classical plate theory), and temperature gradient on the plate statistical transverse response are addressed. Attention is paid to calculate the R.M.S. values of stress components since they directly affect the fatigue life of the structure. A statistical data reconstruction technique named ARMA modeling and its applications in random vibration data analysis are discussed. The model is applied to the simulation data of nonlinear beams. It is shown that good estimations of both the nonlinear frequencies and the power spectral densities are given by the technique.Ph. D.
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Varenius, Malin. "Using Hidden Markov Models to Beat OMXS30." Thesis, Uppsala universitet, Tillämpad matematik och statistik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-409780.
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Sikora, Roman. "DC-DC měnič pro matrix beam modul." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-413161.
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The master thesis deals with the development of buck-boost DC-DC converter which supplies matrix beam module. The design is focused on testing two-phase boost converter and three channel buck converter manufactured by NXP Semiconductors. Part of the design is implementation of microcontroller for converter control and communication with computer. Part of the thesis is also to design user interface on Windows platform for easy system configuration. Next thing the thesis deals with is designing load for DC-DC converter that is variable and can make different current consumption. One part of this thesis is focused to achieve the lowest conducted emissions and to maximize conducted immunity. Part of this project is production of a prototype and prototype testing.
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Gayadeen, Sandira. "Synchrotron electron beam control." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:234025b3-2d1b-495e-846e-688f14149b21.
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This thesis develops techniques for the design and analysis of controllers to achieve sub-micron accuracy on the position of electron beams for the optimal performance of synchrotrons. The techniques have been applied to Diamond Light Source, the UK's national synchrotron facility. Electron beam motion in synchrotrons is considered as a large-scale, two-dimensional process and by using basis functions, controllable modes of the process are identified which are independent and allow the design to be approached in terms of a family of single-input, single-output transfer functions. This thesis develops techniques for the design and analysis of controllers to achieve sub-micron accuracy on the position of electron beams for the optimal performance of synchrotrons. The techniques have been applied to Diamond Light Source, the UK's national synchrotron facility. Electron beam motion in synchrotrons is considered as a large-scale, two-dimensional process and by using basis functions, controllable modes of the process are identified which are independent and allow the design to be approached in terms of a family of single-input, single-output transfer functions. In this thesis, loop shaping concepts for dynamical systems are applied to the two-dimensional frequency domain to meet closed loop specifications. Spatial uncertainties are modelled by complex Fourier matrices and the closed loop robust stability, in the presence of spatial uncertainties is analysed within an Integral Quadratic Constraint framework. Two extensions to the unconstrained, single-actuator array controller design are considered. The first being anti-windup augmentation to give satisfactory performance when rate limit constraints are imposed on the actuators and the second being a strategy to account for two arrays of actuators with different dynamics. The resulting control schemes offer both stability and performance guarantees within structures that are feasible for online computation in real time.
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Brink, Hendrik Gideon. "Multi-Vortex distributor : effect on 2-D fluidized bed reactor performance." Diss., University of Pretoria, 2011. http://hdl.handle.net/2263/25719.
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The influence of the distributor configuration on the mass transfer and bubble sizes in a 2-D FBR was studied for two types of distributor configurations: - A novel multi-vortex (MV) distributor with tuyéres directed vertically and horizontally at different heights.
- A standard perforated plate distributor (baseline).
- Uc Baceline = 0.30 m/s.
- Uc MV distributor = 0.25 m/s.
Dissertation (MEng)--University of Pretoria, 2011.
Chemical Engineering
unrestricted
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Sumnicht, Daniel W. "A computer model of a kraft char bed." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/5476.
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Silva, Carla de Mello da. "Estudo do efeito magnetocalórico através do acoplamento entre as redes cristalinas e magnéticas: uma extensão do modelo de Bean-Rodbell." Universidade do Estado do Rio de Janeiro, 2008. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=804.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorSILVA, Carla de Mello. Estudo do efeito magnetocalórico através do acoplamento entre as redes cristalina e magnética: uma extensão do modelo de Bean-Rodbell. 2008. 91f. Dissertação (Mestrado em Física) Instituto de Física, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, 2008. Neste trabalho, apresentamos um estudo do efeito magnetocalórico considerando os conceitos fundamentais envolvidos na formulação teórica e mostramos os procedimentos envolvidos nos cálculos das grandezas termodinâmicas e magnéticas que caracterizam o potencial magnetocalórico de um sistema. O modelo de Bean-Rodell, que leva em consideração a interação magneto-elástica e prevê a possibilidade de uma transição de fase magnética de primeira ordem, é estudado e usado para descrever o efeito magnetocalórico nos sistemas Gd5(SixGe1-x)4, MnFeP0.45As0.55 e MnAs(1-x)Sbx. Além disso, propomos uma extensão do modelo de Bean-Rodbell, incluindo na entropia de Debye a deformação da rede cristalina devido à interação magneto-elástica. Apresentamos também estudos envolvendo os gráficos de Arrott para descrever a ordem da transição de fase magnética, com aplicações nos sistemas Pr3In e Gd5(Si2Ge2).
In this work we present a study of the magnetocaloric effect considering the fundamental concepts about the theoretical formulation and the calculations procedures of the thermodynamics and magnetic quantities, which describe the magnetocaloric potential. The Bean-Rodbell magnetic model, which predicts the possibility of the first order magnetic phase transition, is present and used to describe the giant magnetocaloric effect in Gd5(SixGe1-x)4, MnFeP0.45As0.55 and MnAs(1-x)Sbx. Also, an extension of the Bean-Rodbell model is considered including the influence of the lattice deformation on the Debye entropy. In addition, Arrott plots are performed in order to investigate the existence of the first order magnetic phase transition with application in Pr3In and Gd5(Si2Ge2) compounds.
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Dongo, Kouadio Kouman. "Forecasting the Chinese Futures Markets Prices of Soy Bean and Green Bean Commodities." Digital Archive @ GSU, 2007. http://digitalarchive.gsu.edu/math_theses/23.
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Using both single and vector processes, we fitted the Box-Jenkin’s ARIMA model and the Vector Autoregressive model following the Johansen approach, to forecast soy bean and green bean prices on the Chinese futures markets. The results are encouraging and provide empirical evidence that the vector processes perform better than the single series. The co-integration test indicated that the null hypothesis of no co-integration among the relevant variables could be rejected. This is one of the most important findings in this paper. The purposes for analyzing and modeling the series jointly are to understand the dynamic relationships over time among the series and improve the accuracy of forecasts for individuals series by utilizing the additional information available from the related series in the forecasts for each series.
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廖德榮 and Tak-wing Liu. "A generalized beam on elastic foundation model for fracture studies." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31208745.
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Liu, Tak-wing. "A generalized beam on elastic foundation model for fracture studies /." [Hong Kong : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12433871.
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Lindholm, Brian Eric. "Reconciliation of a Rayleigh-Ritz beam model with experimental data." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06102009-063201/.
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King, David John Stephen. "A biomechanical model for lung fibrosis in proton beam therapy." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/814043/.
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The physics of protons makes them well-suited to conformal radiotherapy due to the well-known Bragg peak effect. From a proton’s inherent stopping power, uncertainty effects can cause a small amount of dose to overflow to an organ at risk (OAR). Previous models for calculating normal tissue complication probabilities (NTCPs) relied on the equivalent uniform dose model (EUD), in which the organ was split into 1/3, 2/3 or whole organ irradiation. However, the problem of dealing with volumes < 1/3 of the total volume renders this EUD based approach no longer applicable. In this work the case for an experimental data-based replacement at low volumes is investigated. Lung fibrosis is investigated as an NTCP effect typically arising from dose overflow from tumour irradiation at the spinal base. Considering a 3D geometrical model of the lungs, irradiations are modelled with variable parameters of dose overflow. To calculate NTCPs without the EUD model, experimental data is used from the quantitative analysis of normal tissue effects in the clinic (QUANTEC) data. Additional side projects are also investigated, introduced and explained at various points. A typical radiotherapy course for the patient of 30×2Gy per fraction is simulated. A range of geometry of the target volume and irradiation types is investigated. Investigations with X-rays found the majority of the data point ratios (ratio of EUD values found from calculation based and data based methods) at ∼20% within unity showing a relatively close agreement. The ratios have not systematically preferred one particular type of predictive method. No Vx metric was found to consistently outperform another. In certain cases there is a good agreement and not in other cases which can be found predicted in the literature. The overall results leads to conclusion that there is no reason to discount the use of the data based predictive method particularly, as a low volume replacement predictive method.
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Petrie, Tracy. "Motion binning in cone-beam CT without a prior model." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/1684/.
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Cone-beam CT (CBCT), used to reduce setup error in radiotherapy, takes a sequence of about 670 two-dimensional X-rays acquired in a circular arc around the patient over two minutes and reconstructs a three-dimensional volume from these projections. Consequently, when tissues move significantly during the acquisition the resulting volume is blurry or contains streaks. The projections themselves, though, are sharp. One of the main areas of research with CBCT has been to attempt to reconstruct the motion from these projections by collecting them into respiratory-phase or amplitude bins and using these to reconstruct bin-specific volumes. A variety of mechanisms are employed to identify and record respiratory motion so that it can be correlated with the projections. Not all motion that occurs in the body can be correlated with respiration. The research question pursued in this thesis is whether motion can be identified in a binning process without prior knowledge or models of the motion. Nomenclature describing motion classes and a specific type of artefact are introduced. The distinctiveness of this artefact class is demonstrated and methods to mitigate it are proposed and evaluated. Several techniques are then used to reduce an intractable search space to a computationally feasible one. A unique application of PCA to the reconstruction process allows new kinds of search approaches to be considered including an exhaustive search which requires a protocol change and a multiple-restart hill-climbing search that can be used with existing protocols. Experiments with three classes of phantoms, including a novel animated physical phantom, show the effectiveness of the two search methods which are finally compared with each other.
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Song, Huimin. "Rigorous joining of advanced reduced-dimensional beam models to 3D finite element models." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33901.
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This dissertation developed a method that can accurately and efficiently capture the response of a structure by rigorous combination of a reduced-dimensional beam finite element model with a model based on full two-dimensional (2D) or three-dimensional (3D) finite elements.
As a proof of concept, a joint 2D-beam approach is studied for planar-inplane deformation of strip-beams. This approach is developed for obtaining understanding needed to do the joint 3D-beam model. A Matlab code is developed to solve achieve this 2D-beam approach. For joint 2D-beam approach, the static response of a basic 2D-beam model is studied. The whole beam structure is divided into two parts. The root part where the boundary condition is applied is constructed as a 2D model. The free end part is constructed as a beam model. To assemble the two different dimensional model, a transformation matrix is used to achieve deflection continuity or load continuity at the interface. After the transformation matrix from deflection continuity or from load continuity is obtained, the 2D part and the beam part can be assembled together and solved as one linear system.
For a joint 3D-beam approach, the static and dynamic response of a basic 3D-beam model is studied. A Fortran program is developed to achieve this 3D-beam approach. For the uniform beam constrained at the root end, similar to the joint 2D-beam analysis, the whole beam structure is divided into two parts. The root part where the boundary condition is applied is constructed as a 3D model. The free end part is constructed as a beam model. To assemble the two different dimensional models, the approach of load continuity at the interface is used to combine the 3D model with beam model. The load continuity at the interface is achieved by stress recovery using the variational-asymptotic method. The beam properties and warping functions required for stress recovery are obtained from VABS constitutive analysis. After the transformation matrix from load continuity is obtained, the 3D part and the beam part can be assembled together and solved as one linear system. For a non-uniform beam example, the whole structure is divided into several parts, where the root end and the non-uniform parts are constructed as 3D models and the uniform parts are constructed as beams. At all the interfaces, the load continuity is used to connect 3D model with beam model. Stress recovery using the variational-asymptotic method is used to achieve the load continuity at all interfaces. For each interface, there is a transformation matrix from load continuity. After we have all the transformation matrices, the 3D parts and the beam parts are assembled together and solved as one linear system.
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Santos, Daniel dos. "Análise de vigas de concreto armado utilizando modelos de bielas e tirantes." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-22062006-102606/.
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O modelo de bielas e tirantes apresenta como uma de suas vantagens a generalidade, ou seja, é capaz de representar, de modo aproximado, porém realista e sistemático, grande parte dos elementos de concreto estrutural da atualidade. Além disso, permite ao engenheiro fácil visualização físico-intuitiva do comportamento do concreto estrutural. Por outro lado, o modelo ainda tem um enorme potencial não aproveitado. Ainda não se tem um critério exato para determinação dos nós e das seções transversais das bielas de alguns elementos. Apesar de haver certas incertezas no caso de vigas-parede e principalmente de blocos de fundação, nas vigas esses elementos do modelo podem ser determinados sem grandes dificuldades. Possivelmente, a solução seria variar as dimensões das bielas e as posições dos nós, ambas hipotéticas, a fim de confrontar várias situações com resultados experimentais. Daí a grande importância da difusão do modelo de bielas e tirantes: um maior número de análises de modelagens e de resultados de ensaios levará a um maior domínio sobre o modelo. Este trabalho consiste na análise de vigas de concreto armado utilizando modelos de bielas e tirantes. São apresentados os conceitos que levaram à concepção do modelo, desde a Analogia Clássica da Treliça, chegando aos critérios para verificação dos elementos da treliça e às recomendações atuais de normas e pesquisadores. Com o auxílio do programa computacional CAST (2000), foram modeladas quatro vigas, sendo as três primeiras biapoiadas sem descontinuidades e a quarta com balanço e descontinuidade geométrica (abertura na alma). A primeira viga biapoiada teve algumas de suas características iniciais alteradas a fim de gerar o segundo e o terceiro modelos, procurando-se estabelecer limites de carregamentos e análises comparativas. Os resultados das modelagens permitiram comparações com os resultados das verificações realizadas segundo os critérios da NBR 6118:2003 e do MC CEB-FIP (1990) e, permitiram também, identificar os aspectos de maior dificuldade na concepção de um modelo de bielas e tirantes e os pontos críticos dos mesmos, nos quais há maior possibilidade de falha nas verificaçõesOne of the main advantages presented by the strut-and-tie model is generality. This model is able to approximately represent, in a realistic and systematic way, the majority of todays reinforced concrete elements. Furthermore, it allows the physics-intuitive visualization of the behavior presented by structural concrete. On the other hand, its potentials are not fully explored yet. Up to date, there is no accurate criterion for the determination of nodes and transverse sections of some strut elements. Despite presenting some uncertainties related to the determination of wall-beams (and mainly of foundation blocks), the model can determine beams without major difficulties. Probably, the key is to vary the dimensions of the struts and the positions of the nodes, both hypothetical, in order to confront various situations with experimental data. Hence, it is very important to diffuse the strut-and-tie model: the bigger the number of modeling analysis and experimental data, the better the comprehension of the model. This work aims to analyze reinforced concrete beams employing the strut-and-tie model. Here are presented the concepts that led to the development of the model, ranging from the Truss Classic Analogy to the criteria employed to verify truss elements and the recommendations from researchers and established standards (rules or norms). Four examples of beams were modeled. Three of them were double-based and the fourth presented balance and no geometric discontinuity (with an opening). Some of the characteristics of the first double-based beam were altered in order to generate the second and the third model, thus establishing loading limits and comparative analysis. The modeling allowed comparisons between the verifications performed in accordance with the NBR 6118:2003 and MC CEB-FIP criteria. It also allowed the identification of major difficulties and critical aspects related to the development of struts and ties, the ones that are most prone to failure in the verification process
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Parent, Alain Paul. "Scale models of gravel bed rivers." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28319.
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The combined studies of flow processes in a full size gravel-bed river and its associated small-scale model have demonstrated the applicability of the similitude concepts as well as the potential of scale models for quantitative research in fluvial geomor phology. This scaling investigation
considered the comparison of velocity profiles, shear stress measurements, flow structure and surface bed material samples. An extension of the strict comparison on a detailed level of field and laboratory processes in a specific case consisted in the proposition of a "generic model" framework according to which laboratory systems are viewed as part of the same family as field ones if some crucial conditions are satisfied. The pool-riffle sequence, used as a vehicle for the demonstration herein, is presented as a poorly Known but ubiquitous river phenomenon which would benefit from such research methodology. The laboratory study performed herein revealed the need for an appraisal of the variability of shear stress estimates in intermediate relative roughness flows such as field size gravel-bed rivers. Knowledge of elements of the history of the prototype (field) river was also demonstrated to be important for the appraisal of model performance.Arts, Faculty of
Geography, Department of
Graduate
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Mehay, Dennis Nolan. "Bean Soup Translation: Flexible, Linguistically-motivated Syntax for Machine Translation." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345433807.
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Rydström, Sara. "Regularization of Parameter Problems for Dynamic Beam Models." Licentiate thesis, Växjö University, School of Mathematics and Systems Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-7367.
Full textAbstract:
The field of inverse problems is an area in applied mathematics that is of great importance in several scientific and industrial applications. Since an inverse problem is typically founded on non-linear and ill-posed models it is a very difficult problem to solve. To find a regularized solution it is crucial to have a priori information about the solution. Therefore, general theories are not sufficient considering new applications.
In this thesis we consider the inverse problem to determine the beam bending stiffness from measurements of the transverse dynamic displacement. Of special interest is to localize parts with reduced bending stiffness. Driven by requirements in the wood-industry it is not enough considering time-efficient algorithms, the models must also be adapted to manage extremely short calculation times.
For the developing of efficient methods inverse problems based on the fourth order Euler-Bernoulli beam equation and the second order string equation are studied. Important results are the transformation of a nonlinear regularization problem to a linear one and a convex procedure for finding parts with reduced bending stiffness.